Koofers

Energy/Neurophiosology - Flashcards

Flashcard Deck Information

Class:BIOL 408 - Physiology of Organisms
Subject:Biology
University:University of Kansas
Term:Spring 2013
- of -
INCORRECT CORRECT
- INCORRECT     - CORRECT     - SKIPPED
Shuffle Remaining Cards Show Definitions First Take Quiz (NEW)
Hide Keyboard shortcuts
Next card
Previous card
Mark correct
Mark incorrect
Flip card
Start Over
Shuffle
      Mode:   CARDS LIST       ? pages   PRINT EXIT
Levels of Organization Organism

Organ System>Organ & Tissue>Cellular>Macromolecular>Molecular


Themes/Principles of Physiology Function = based on structure

Homeostasis

Genetics & Physiology
         functions arise through evolution and are genetically determined

Conformity vs Regulation Conformity = no homeostasis 
       conforms to outside world

Regulation = homeostasis
        zone of stability
 example --> fish internal fluctuations ∆/time of a physiochemical variables (oxygen)
Negative Feedback Negative feedback occurs when the result of a process influences the operation of the process itself in such a way as to reduce changes.
(shuts off original stimulus)
Process:
Disturbance --> controlled system --> output --> sensor --> error/signal --> inverting amplifier --> negative feedback --> Starts over again

Examples:  Blood sugar levels, blood pressure, temperature, homeostatic activities
Generated by Koofers.com
Positive Feedback Positive feedback is a process in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation.
(amplifies original stimulus)
Process:
Disturbance --> controlled system --> output --> sensor --> error/signal --> amplifier --> Positive feedback --> Starts over again
Continues until material for loop has run out

Examples:  Blood clotting, Uterus contractions in childbirth, AP's
Principles of Animal Physiology
  1. Optimization/efficiency
  2. Flexibility - adjust to internal/external conditions
  3. Control/Regulatory Mechanisms - maintain homeostasis
  4. Specialization/Compartmentalization - division of tasks
Energy Important Questions to Consider:
  1. What is it - Voltage and Concentration gradients, ATP
  2. how to get it - Cellular Respiration --> ATP
  3. how to control it
ATP Molecules Adenosine group with a triphosphate

ATP broken into ADP (removal of 1 phosphate) --> 7.3Kcal/mol

Other energy rich compounds:
  1. phosphoenolpyruvate
  2. glucose 1-phosphate
  3. 1,3-diphosphoglycerate
  4. phosphocreatine
Generated by Koofers.com
Energy Metabolism multi-step and bidirectional

Cellular Respiration:
Glycolysis, Citric Acid Cycle, and Chemiosmosis

Glucose is trapped into cell by phosphorylation
Glycolysis glucose (requires 2ATP molecules & converts to ADP)
  • 2ADP + 2Pi --> 2ATP (Net Gain) (4 total are produced)
  • 2NAD+ --> 2NADH + 2H+   ****NAD+ is the limiting reactor
After above steps done, 2 pyruvate and 2 H2O molecules  made

***Without O2 --> Anaerobic glycolysis (no CAC or Chemiosmosis)
buildup of pyruvate and lactate
Pyruvate converted to lactate to regenerate NAD+ to continue glycolysis    **(Pyruvate = Key Juncture)
Aerobic Cellular Respiration After Glycolysis  --> Krebs Cycle (net gain of 2 ATP) 
                                        Acetyl CoenzymeA --> CO2 and H+
***Oxygen must be present for Krebs cycle and Chemiosmosis

Chemiosmosis (couples e- Trans Chain w/ ATP Synth) --> 34 ATP
ATP Synthase = most important protein (uses Proton [Conc] Gradient)
        Oxidative phosphorylation
Oxygen = final e- acceptor (low e- pressure & readily avail in atmos)
Energetics of Cell. Respiration In General:  Gluc + O2 --> CO2 + H2O + ∆H (686Kcal)

In Cell:  Gluc + 38P +38ADP + O2 --> CO2 + H2O + 38ATP + 420Kcal

39% efficieny compared to 30% diesel and 20% gasoline engines

Generated by Koofers.com
Enzyme Roles in Metab Reax Enzymes lower activation energy for reactions
-->not used up in one single reax so enzymes can continue to facilitate those reactions

Lock and Key Models
  • so only specific substrates can bind to proteins
Enzyme activity increases w/ Temp, but will denature if it gets too hot
Certain enzymes work better in specific pH levels
       pH can --> ∆ in protein [Conc.] and ∆ in [Charge]
Control of Enzyme Activity Regulatory molecules (Cofactors - small molecules that help enzymes work)
  • Organic molecules:  coenzymes, and NAD+
  • metal ions: Calcium (hormones, AP's, muscle contrax, etc)
Inhibitors (reversible**, irreversible)
    reversible inhibitors compete w/ substrate to bind at allosteric site (no reax will occur)         Substrates bind at Active site (reax occurs)

End Product Inhibition - End prod. stops reax (negative feedback)
A (enz1)-->B (enz2)-->C (enz3)-->D (enz4)-->E (enz5)--> End Prod
Membranes cellular and subcellular compartmentalization

phospholipid bilayer -->
areas differ in chemical composition

creation of chemical and electrical gradients = source of chemical and electrical potential
  • require transport mechanisms
sugar molecules are found outside cell, not inside
  • used for cell-cell recognition
Diffusion solute molecules travel from high concentration to low concentration
  • random motion drives diffusion
  • kinetic energy, no ATP required

influx = in,     efflux = out
Net flux = J1 - J2

Generated by Koofers.com
Rate of Diffusion Qs/t = Ds x A x Cs / X (Fick Diffusion Equation)
  • Ds = Diffusion Coefficient
  • A = cross sectional area
  • Cs/X = ∆ in [ ] of solute with distance
Osmosis and Osmotic ∆ Osmosis = diffusion of water across semipermeable membrane, but not solutes
  • Hydrostatic pressure = in direction of water
  • Osmotic pressure = in direction of solutes
isotonic solution - equal [ ] inside and outside cell (no ∆ in cell Vol)
hypotonic solution - [ ] inside cell is > outside (cell Vol increases)
hypertonic solution - [ ] outside cell > inside (cell Vol decreases)

Permeability Ease with which a substance can passively pass thru a unit area of a membrane

Qs/t = P(C1-C2)
  • C1-C2 = [ ] gradient of solute across membrance
  • P = permeability constant = Dm x K/X
  • As P increases, so does flux and Permeability
  • P varies for each solute
Passive Transport no energy needed to transport molecules
  • Diffusion through aqueous channes
  • diffusion through lipid phase
  • carrier-mediated transport - selective and saturation effects
  •  Facilitated diffusion          example = proteins

Generated by Koofers.com
Active Transport requires energy, ATP     use of pumps
can produce chemical or electrical gradient across membranes
  • transport against gradient
  • high degree of selectivity for transported chemical
  • can be exchange pumps: Na for K ions
  • Selective inhibition: - ouabain inhibs Na/K pumps
  • Need ATP:  ATP-ases in membrance
Types of Pumps Uniporter - ions being pumped in only 1 direction
Symporter - ions being pumped from same side
Antiporter - can pump ions in both directions
Nerve Cells Transmit information from one nerve cell to the next

Multipolar Neurons More than 2 processes
Numerous dendrites and one long axon



Generated by Koofers.com
Unipolar Neurons Possess one single process
start as bipolar neurons during development


Functional Classifications of Neurons based on direction of AP propogation
      SAME
  • Afferents - periphery to CNS
  • Efferents - CNS to periphery
  • Interneurons - stay in CNS

Galvani's experiment - discovered "animal electricity" and contracted muscles with nerve and connection to zinc and copper
Know Structure of Nerve Cell Dendrites
Soma
Axon hillock
Axon terminals
Synapse

Physiological Responses depend on
  • anatomical form
  • specialized regions w/ membranes not uniform
V = I x R Ohm's Law
Generated by Koofers.com
Electrical Signals in Neurons Neurons have resting membrane potential

neurons are excitable --> can rapidly ∆ their memb potential

∆ in membrane potential act as electrical signals

Information Flow graded potential changes - occur at sensory membrane and postsynaptic membrane

Signal strength decreases as distance traveled increases

All or none potentials occur at axons


Graded Potentials Short-lived ∆ in membrane potential (depolarizations or hyperpolarizations)

Voltage ∆ are decremental
  • the charge is lost quickly through the permeable plasma membrane
Magnitude varies w/ strength of stimulus
  • can stimulate AP's if strong enough
Action Potentials nerve impulse, method of communication between neurons

brief reversal in memb potential w/ a total amplitude of 100mV
  • resting = -70mV and rises to +30mV
AP's do NOT decrease in strength w/ distance

Depolarization--> repolarization--> hyperpolarization (short period)

Generated by Koofers.com
Passive Electrical Responses Always when currents are forced across membrane b/c membrane has electrical properties
  • capacitance (storage of e-'s)
  • conductance (resistance)
Responses are INDEPENDENT of molecular changes in membrane

Ion channels act as resistance
membrane stores charges

Active Electrical Responses opening and closing of ion channels in response to stimulus
  • Gating - ∆ in biological property of nerve membrane
  • activation = opening
  • inactivation = closing of ion channels

Gated Ion channels
  • Voltage Gated:  change in voltage
  • Ligand-Gated:  neurotransmitters
  • Mechanically-Gated:  stretching of membrane

Chemical and Genetic Disorders with Gates
  • TTX, found in puffer fish, blocks gating of Na channels
  • Cystic Fibrosis - gene mutation --> blocks Cl channels

Equilibrium Potential If membrane is permeable to only ion X, then the membrane potential will move to the equil. potential for that ion

membrane = permeable to K
Ions move down electrochemical gradient

Net movement stops when eq. potential is reached
  • Na channels close and K channels open
Membrane potential = closer to K at -60mV than Na at +60
  • Na/K pumps = always working in nerve cells, 3Na out/ 2K in
Generated by Koofers.com
Más Action Potential Depolarization - makes membrane potential less negative
Hyperpolarization - makes membrane more negative

AP amplitude does NOT depend on stimulus strength


Ionic Events during AP *****VERY IMPORTANT LOOK AT SLIDE******
  1. Conductance(g) of Na increases rapidly******
  2. (g)Na stops ∆ as Vm --> Eq Pot of Na******
  3. (g)K increases as Vm --> Eq Pot of Na**
  4. (g)Na decreases rapidly as Vm --> Eq Pot of K**
  5. (g)K decreases as Vm --> Eq Pot of K**
  6. Lingering decrease in (g)K - after-hyperpolarization
******Rising Phase (depolarization)
**Falling Phase (hyperpolarization)

Hodgkin Cycle Regenerative part of AP
Positive Feedback - speeds process up, does not turn it off
  • opens Na channels (sensitive to Voltage ∆)
  • wont quite reach Eq Pot of Na, Eq Pot = Limiting Factor

Membrane Depolarization--> Increase in (p)Na--> Na influx--> Depol
Voltage-Gated Channels Positive feedback for Na influx into cell until reaches Eq Pot
  • before that point, Voltage gated channels for K open
  • K leaves the cell --> Negative FB
  • K continues Negative FB loop until after-hyperpolarization

Generated by Koofers.com
Nernst Equation & Misc For the given Na concentration:
(E)Na = 0.058log( [Na outside] / [Na inside] )

Na moves into cell b/c [ ] differences
Na rushes in, (-) charge in cell, (+) charge outside cell

repolarization - allows cell to return to resting value

Na/K pumps keep the concentrations unequal across membranes
Refractory Period Slowly recovering from AP
Absolute Refractory Period: No stimulus of any strength can produce an AP due to **inactivation of Na channels
Relative Refractory Period:  Strong stimulus can --> another AP but w/ a smaller amplitude due to **Na activation and still some K activation

Does not approach (E)Na as closely b/c K channels are still open,
**K channels need to be closed
Continuous Stimulus Excitability of memb decreases w/ time (threshold increases)

Physiological ∆ is called Accomodation
  • context dependent, some membranes accomodate faster than others 
Phasic response flatlines in the middle

tonic response creates new AP's, but each one is a little more spaced apart in time
Channel Density Axon Hillock = where AP is initiated
  • has high concentration of Voltage gated channels
  • lower threshold
  • shorter relative refractory period
Generated by Koofers.com
Graded vs Action Potential Summary Graded:
Vary in Magnitude,  vary in duration,  decay w/ Distances
occur in dendrites and cell body,  caused by opening and closing of many kinds of ion channels

Action Potential:
always same magnitude,  always same duration,  can be transmitted long distances,  occur in axons, caused by opening and closing of voltage-gated ion channels
Spread of Voltage along Axon Resistance along axon causes decay of signal

Length Constant:   lambda = (Rm/Rl)^1/2
  • Rl = resistance along membrane
  • Rm = resistance across
Some neurons have different Length Constants
  • Larger Rm and a smaller Rl --> increase passive spread/ velocity or propagation
Net effect of increasing radius of Axon = increase in speed of conduction
Propagation of Action Potentials Nerve cells that are short relative to length constant show graded responses, but signals = strong enough to cause neurotransmitters to be released
  • ∆ in memb potential --> signaling other neighboring cells

AP's = regeneration, (not a wave down axon)
  • AP's = 5x as large as threshold level --> safety factor, this extra depolarization --> membrane ahead of AP to depolarize and produce next AP

Myelin
  • acts as an insulator
  • prohibits ions from moving across membrane
  • pushes depolarization further down axon



Generated by Koofers.com
Axons
Problems of Large axons 
  • take up a lot of space --> limits # of neurons that can be packed into nervous system
  • very expensive to produce and maintain
Squids and cucarachas have huge axons

Insulate axon w/ myelin
  • enables rapid signal conduction in a compact space

Nodes of Ranvier Spacings in b/w myelin
  • depolarizations --> Na to enter axon thru open channels --> AP's
  • depolarization encounters the next node -->
leapfrogging of AP's = saltatory conduction

Multiple Sclerosis - loss of myelin in Nervous System
  • slows down conduction of AP
  • muscle weakness, fatigue, vision loss, trouble walking
Synapse Connection between two neurons:
  • Electrical - membranes fused
  • Chemical - graded response
Electrical Synapse Fusion of neurons in which there is physical contact
           Charge goes from A-->B, allows current to flow
Allows current AP in one cell to spread into other and depolarize it

Function = rapid transmission of signals
  • Synchronization of electrical activity in groups of neurons  (i.e. the heart's contractions - contrax needs to happen at same time)
  • Info = transfered in BOTH directions, No control of info flow
Generated by Koofers.com
Chemical Synapse Not physically connected  --> Gap between neurons = Synaptic Cleft      
            **Use of Neurotransmitters, receptors,
  • Terminal at rest -->
  • AP arrives; vesicles fuse w/ terminal membrane --> exocytosis of transmitter(Ca entry into terminal = req'd for NroTr release)
  • Transmitter binds to postsynaptic receptor proteins --> ion channels open
  • Transmitter is removed from cleft; fused membrane recycled
Inactivation of Neurotransmitters
  • Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells (serotonin)
  • Enzymes inactivate neurotransmitters (Ach)
  • Neurotransmitters can diffuse out of synaptic cleft (norepinephrine)
Nicotine
  • binds to receptors selective to Ach & cause AP in postsynaptic cell & there is no enzyme to remove it
  • get muscles to contract when there shouldn't be contrax


Types of Chemical Transmission Fast
  • NT release close to receptors
  • Receptors --> directly open ion channels
  • use of small vesicles (easy to release material)
Slow
  • NT release = distant from receptors
  • receptors indirectly open ion channels (use an intracellular messenger)
  • Use of large vesicles to release more NT's
Major Known Neurotransmitters Acetylcholine
  • excitatory in vertebral skel muscles, inhibitory in others sites
  • CNS, PNS, vertebrate neuromuscular junction
Biogenic Amines (dopamine, NE, serotonin[CNS, inhib] )
  • Excitatory or inhibitory
  • CNS, PNS
Amino Acids (CNS, excitatory or inhib, invertebral neuromuscle junx)
Neuropeptides (CNS or PNS, excitatory or inhibitory)


Generated by Koofers.com
Acetylcholine Primary NT at vertebrate neuromuscular junction
  1. Acetyl CoA = synth in mitochondria
  2. choline acetyl transferase catalyzes conversion of choline and acetyl CoA into ACh
  3. ACh packaged into synaptic vesicles
  4. ACh released & binds to receptor on PostSyn Cell
  5. AChE breaks down ACh into choline and acetate --> terminating the signal in PostSyn Cell
  6. PreSyn Cell takes up and recycles choline,   the acetates diffuse out of synapse
Synaptic Currents EPP = sig/current prod'd in synapse (excitatory PostSyn Pot)Graded

Binding of NT on receptors of PostSyn membrane --> opening of PostSyn Channel (Na and K can pass through)
  • 2 Synaptic currents
  1. Inward syn current = Na
  2. Outward syn current = K
  • if only one or other ion can move across membrane then membrane Pot --> Eq Pot for that ion
New Eq estab'd with this phenomena --> Reversal Pot (E rev)
Eq Potentials and Rev Potentials If E(rev) = Vm --> no ∆
If E(rev) > Vm --> Depolarization(more Na moving across,  excitatory)
If E(rev) < Vm --> Hyperolarization (more K moving across,  inhibitory)

Thus the Value of Reversal Potential = essential in distinguishing b/w excitatory and inhibitory synapse

***Chemical Synapse acts as Switch in neural circuits (Yes or No AP)
  • Exc and Inhib PostSyn Signals = integrated in same PostSyn Cell
Summation of Postsynaptic Potentials
  • Subthreshold --> No AP
  • Temporal Summation --> AP (summation over time)
  • Spatial Summation --> AP (summation over space)
  • Spatial Summation of EPSP and IPSP --> No AP

Generated by Koofers.com
Presynaptic Inhibition Inhib synapse on top of excitatory synapse
  • Renshaw cells --> control overstimulation of muscle cells normally release inhib NT (glycine) onto motor neurons to prevent excessive muscle contrax
Strychnine Poisoning
  • Strychnine binds to and blocks glycine receptors in spinal cord
  • Massive contrax of all skel muscles, convulsions
  • diaphragm contrax --> no breathing
  • fatal within 3 hours
Summary of Electrical and Chemical Synapses Electrical Synapse
  • Rare in complex animals, common in simple animals
  • fast, bi-directional
  • excitatory
  • Postsynaptic signal is similar to presynaptic
Chemical Synapse
  • Common in complex animals, rare in simple animals
  • Slow, unidirectional
  • excitatory or inhibitory
  • Postsynaptic signal can be different
Sensory Modalities Chemoreceptors
Mechanoreceptors
Photoreceptors
Thermoreceptors
Electroreceptors
Receptor Cell conversion of receptor potential into propagated impulses
  • receptor is not regenerative (NO Hodgkin Cycle)
Stimulus --> small receptor potential --> AP
  • Receptor current spreads electronically to spike initiation zone
  • Or ∆ NT release to produce AP in secondary neuron

Stimulus --> receptor --> G protein --> effector enzyme --> 2nd Messenger molecule --> ion channel
Generated by Koofers.com
Receptor Events ****Look at Slides****
Transduction
  • Stimulus reaches receptor cell
  • Receptor protein activated
Amplification
  • Cascade of protein interax modifies intracell. 2nd messengers
  • Ion channels open (or close)
∆ in Conductance --> receptor current
Receptor current ∆ Vm --> Spike initiation zone/transmitters released
  • # and/or ƒ of AP along axon ∆ (afferent)  (  All or None AP's)
Stretch Receptor Cell
  • Muscles stretch
  • stretch receptor cell measures the stretching of muscles

  • converts stimulus to graded and later to AP and AP sent



Stimulus-Response Relationship The Stronger the Stimulus --> the more AP's produced per unit of time

Stimulus intensity = semilogarithmic relat to response 
Refractory periods and only so much receptor potential = reason

Sensory Quality--> Spec. sensor cell connected CNS
  • Intensity = temporal distribution
  • Input-Output = semi-log relat (see above)



Input-Output Relations Receptor response = proportional to log of stimulus intensity
  • high intensity of scale becomes compressed (extending dynamic range of detection)
  • Sunlight = 10^9 times más strong than moonlight
  • Human auditory system can detect 12 orders of magnitude of sound
Dynamic Range of Detection = certain range of stimulus intensity
  • Upper limit of receptor current (finite # ion channels)
  • Upper lim of amplif of receptor Pot (Cant exceed Revers Pot)
  • Upper limit of on AP ƒ (refractory period)
Generated by Koofers.com
Range Fractionation Different cells w/ different but overlapping sensitivities (extends dynamic range)

Response to stimuli of Const Intensity
  • Tonic and phasic receptor cells
Adaptation of receptor cell to continued stimulus
Sensory Adaptation 4 possible mechanisms:
  1. Depletion of receptor molecules (rhodopsine in eyes)
  2. ∆ in electrical properties of receptor cell                              Activation of Ca dependent K channels due to más [Ca]
  3. Accessory structures --> time dep. ∆ (pupil adjustment)
  4. Accomadation --> a drop in sensitivity of receptor cell due to depolarization
Function = extend dynamic range, allowing detection of weak & strong stimuli
  • tonic receptors = pain, danger sits   phasic = noise
Lateral Inhibition Example = color chart of same intensity
  • used to enhance contrast

vision and hearing = uses of this
Chemoreception Gustatory organs --> taste (gustation), have taste pores

Olfactory Organs --> smell,  insects have larger pores(better smellers)

4 Basic tastes:
  1. Sweet
  2. Sour
  3. Salty
  4. Bitterness

Generated by Koofers.com
Sensory Transduction Taste Receptors 
  • ligand binds to receptor-->
  • Signal Transduction Pathway-->
  • K+ channels close, Ca and Na channels open (influx & Depol)
  • stimulates release of NT's
Taste:
Ensemble coding --> groups of neurons send "pieces" of sensory "puzzle" to brain where pieces put together
Labeled Line Coding --> very selective sensor cells  analogous to calling a specific person in phone 
Olfaction Sends signals directly to brain (Maybe why smells are remembered better)
  • VNO - chamber used to process sexual communication (sex pheromones)
Odoroant binds to receptor --> G protein --> Adenylate Cyclase (ATP for prod of cAMP) --> cAMP binds to Cyclic Nucleotide gated cation channel
Glomerulus - cluster of neurons that receive info from receptor cells w/ similar selectiveness (1st place of sensory processing)
  • not in taste cells
Sensory Pathways Olfactory -->cortex (directly)

Every other sense passes through Thalamus(center for processing info) and then projected to relevant cortical area

Equilibrium pathways project to cerebellum w/ a branch to the cortex via thalamus
Sensory Processing
  1. Somatosensory cortex
  2. sensory association areas (integration of all sensory input)
  3. Visual cortex
  4. Olfactory cortex

Look at slides


Generated by Koofers.com
Somatosensory Processing Somesthetic (Body feelings) - touch, pain, temp, pressure

information is projected to the somatosensory cortex

Somototopic Order in Sensory Cortex
  • More surface area in brain --> more information processing
  • therefore is more important
Hearing Sound: Alternation of high and low pressure waves

Detected by special mechanoreceptor cells (hair cells)

Features of Sound-->
  • Pitch/tone (deps on ƒ)
  • Intensity/loudness (deps on amplitude)
  • Timbre/Quality (deps on overtones)
Hearing: Its Mechanoreceptors
  1. Sound waves strike tympanic membrane --> Vibrations
  2. Sound wave E transfered to 3 bones of middle ear and vibes
  3. Stapes attached to membrane of oval window, vibrations of oval window create fluid waves w/in cochlea
  4. Fluid waves push the flexible membrane of cochlear duct
  5. E from waves transfer across cochlear duct and is dissipated back into the middle of ear at the round window
  6. Hair cells w/in cochlear duct creates AP's in sensory neurons of cochlear nerve
  • Organ of Corti = Important for Hearing
Generated by Koofers.com

List View: Terms & Definitions

  Hide All 79 Print
 
Front
Back
 Levels of OrganizationOrganism

Organ System>Organ & Tissue>Cellular>Macromolecular>Molecular


 Themes/Principles of PhysiologyFunction = based on structure

Homeostasis

Genetics & Physiology
         functions arise through evolution and are genetically determined

 Conformity vs RegulationConformity = no homeostasis 
       conforms to outside world

Regulation = homeostasis
        zone of stability
 example --> fish internal fluctuations ∆/time of a physiochemical variables (oxygen)
 Negative FeedbackNegative feedback occurs when the result of a process influences the operation of the process itself in such a way as to reduce changes.
(shuts off original stimulus)
Process:
Disturbance --> controlled system --> output --> sensor --> error/signal --> inverting amplifier --> negative feedback --> Starts over again

Examples:  Blood sugar levels, blood pressure, temperature, homeostatic activities
 Positive FeedbackPositive feedback is a process in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation.
(amplifies original stimulus)
Process:
Disturbance --> controlled system --> output --> sensor --> error/signal --> amplifier --> Positive feedback --> Starts over again
Continues until material for loop has run out

Examples:  Blood clotting, Uterus contractions in childbirth, AP's
 Principles of Animal Physiology
  1. Optimization/efficiency
  2. Flexibility - adjust to internal/external conditions
  3. Control/Regulatory Mechanisms - maintain homeostasis
  4. Specialization/Compartmentalization - division of tasks
 EnergyImportant Questions to Consider:
  1. What is it - Voltage and Concentration gradients, ATP
  2. how to get it - Cellular Respiration --> ATP
  3. how to control it
 ATP MoleculesAdenosine group with a triphosphate

ATP broken into ADP (removal of 1 phosphate) --> 7.3Kcal/mol

Other energy rich compounds:
  1. phosphoenolpyruvate
  2. glucose 1-phosphate
  3. 1,3-diphosphoglycerate
  4. phosphocreatine
 Energy Metabolismmulti-step and bidirectional

Cellular Respiration:
Glycolysis, Citric Acid Cycle, and Chemiosmosis

Glucose is trapped into cell by phosphorylation
 Glycolysisglucose (requires 2ATP molecules & converts to ADP)
  • 2ADP + 2Pi --> 2ATP (Net Gain) (4 total are produced)
  • 2NAD+ --> 2NADH + 2H+   ****NAD+ is the limiting reactor
After above steps done, 2 pyruvate and 2 H2O molecules  made

***Without O2 --> Anaerobic glycolysis (no CAC or Chemiosmosis)
buildup of pyruvate and lactate
Pyruvate converted to lactate to regenerate NAD+ to continue glycolysis    **(Pyruvate = Key Juncture)
 Aerobic Cellular RespirationAfter Glycolysis  --> Krebs Cycle (net gain of 2 ATP) 
                                        Acetyl CoenzymeA --> CO2 and H+
***Oxygen must be present for Krebs cycle and Chemiosmosis

Chemiosmosis (couples e- Trans Chain w/ ATP Synth) --> 34 ATP
ATP Synthase = most important protein (uses Proton [Conc] Gradient)
        Oxidative phosphorylation
Oxygen = final e- acceptor (low e- pressure & readily avail in atmos)
 Energetics of Cell. RespirationIn General:  Gluc + O2 --> CO2 + H2O + ∆H (686Kcal)

In Cell:  Gluc + 38P +38ADP + O2 --> CO2 + H2O + 38ATP + 420Kcal

39% efficieny compared to 30% diesel and 20% gasoline engines

 Enzyme Roles in Metab ReaxEnzymes lower activation energy for reactions
-->not used up in one single reax so enzymes can continue to facilitate those reactions

Lock and Key Models
  • so only specific substrates can bind to proteins
Enzyme activity increases w/ Temp, but will denature if it gets too hot
Certain enzymes work better in specific pH levels
       pH can --> ∆ in protein [Conc.] and ∆ in [Charge]
 Control of Enzyme ActivityRegulatory molecules (Cofactors - small molecules that help enzymes work)
  • Organic molecules:  coenzymes, and NAD+
  • metal ions: Calcium (hormones, AP's, muscle contrax, etc)
Inhibitors (reversible**, irreversible)
    reversible inhibitors compete w/ substrate to bind at allosteric site (no reax will occur)         Substrates bind at Active site (reax occurs)

End Product Inhibition - End prod. stops reax (negative feedback)
A (enz1)-->B (enz2)-->C (enz3)-->D (enz4)-->E (enz5)--> End Prod
 Membranescellular and subcellular compartmentalization

phospholipid bilayer -->
areas differ in chemical composition

creation of chemical and electrical gradients = source of chemical and electrical potential
  • require transport mechanisms
sugar molecules are found outside cell, not inside
  • used for cell-cell recognition
 Diffusionsolute molecules travel from high concentration to low concentration
  • random motion drives diffusion
  • kinetic energy, no ATP required

influx = in,     efflux = out
Net flux = J1 - J2

 Rate of DiffusionQs/t = Ds x A x Cs / X (Fick Diffusion Equation)
  • Ds = Diffusion Coefficient
  • A = cross sectional area
  • Cs/X = ∆ in [ ] of solute with distance
 Osmosis and Osmotic ∆Osmosis = diffusion of water across semipermeable membrane, but not solutes
  • Hydrostatic pressure = in direction of water
  • Osmotic pressure = in direction of solutes
isotonic solution - equal [ ] inside and outside cell (no ∆ in cell Vol)
hypotonic solution - [ ] inside cell is > outside (cell Vol increases)
hypertonic solution - [ ] outside cell > inside (cell Vol decreases)

 PermeabilityEase with which a substance can passively pass thru a unit area of a membrane

Qs/t = P(C1-C2)
  • C1-C2 = [ ] gradient of solute across membrance
  • P = permeability constant = Dm x K/X
  • As P increases, so does flux and Permeability
  • P varies for each solute
 Passive Transportno energy needed to transport molecules
  • Diffusion through aqueous channes
  • diffusion through lipid phase
  • carrier-mediated transport - selective and saturation effects
  •  Facilitated diffusion          example = proteins

 Active Transportrequires energy, ATP     use of pumps
can produce chemical or electrical gradient across membranes
  • transport against gradient
  • high degree of selectivity for transported chemical
  • can be exchange pumps: Na for K ions
  • Selective inhibition: - ouabain inhibs Na/K pumps
  • Need ATP:  ATP-ases in membrance
 Types of PumpsUniporter - ions being pumped in only 1 direction
Symporter - ions being pumped from same side
Antiporter - can pump ions in both directions
 Nerve CellsTransmit information from one nerve cell to the next

 Multipolar NeuronsMore than 2 processes
Numerous dendrites and one long axon



 Unipolar NeuronsPossess one single process
start as bipolar neurons during development


 Functional Classifications of Neuronsbased on direction of AP propogation
      SAME
  • Afferents - periphery to CNS
  • Efferents - CNS to periphery
  • Interneurons - stay in CNS

Galvani's experiment - discovered "animal electricity" and contracted muscles with nerve and connection to zinc and copper
 Know Structure of Nerve CellDendrites
Soma
Axon hillock
Axon terminals
Synapse

Physiological Responses depend on
  • anatomical form
  • specialized regions w/ membranes not uniform
 V = I x ROhm's Law
 Electrical Signals in NeuronsNeurons have resting membrane potential

neurons are excitable --> can rapidly ∆ their memb potential

∆ in membrane potential act as electrical signals

 Information Flowgraded potential changes - occur at sensory membrane and postsynaptic membrane

Signal strength decreases as distance traveled increases

All or none potentials occur at axons


 Graded PotentialsShort-lived ∆ in membrane potential (depolarizations or hyperpolarizations)

Voltage ∆ are decremental
  • the charge is lost quickly through the permeable plasma membrane
Magnitude varies w/ strength of stimulus
  • can stimulate AP's if strong enough
 Action Potentialsnerve impulse, method of communication between neurons

brief reversal in memb potential w/ a total amplitude of 100mV
  • resting = -70mV and rises to +30mV
AP's do NOT decrease in strength w/ distance

Depolarization--> repolarization--> hyperpolarization (short period)

 Passive Electrical ResponsesAlways when currents are forced across membrane b/c membrane has electrical properties
  • capacitance (storage of e-'s)
  • conductance (resistance)
Responses are INDEPENDENT of molecular changes in membrane

Ion channels act as resistance
membrane stores charges

 Active Electrical Responsesopening and closing of ion channels in response to stimulus
  • Gating - ∆ in biological property of nerve membrane
  • activation = opening
  • inactivation = closing of ion channels

 Gated Ion channels
  • Voltage Gated:  change in voltage
  • Ligand-Gated:  neurotransmitters
  • Mechanically-Gated:  stretching of membrane

Chemical and Genetic Disorders with Gates
  • TTX, found in puffer fish, blocks gating of Na channels
  • Cystic Fibrosis - gene mutation --> blocks Cl channels

 Equilibrium PotentialIf membrane is permeable to only ion X, then the membrane potential will move to the equil. potential for that ion

membrane = permeable to K
Ions move down electrochemical gradient

Net movement stops when eq. potential is reached
  • Na channels close and K channels open
Membrane potential = closer to K at -60mV than Na at +60
  • Na/K pumps = always working in nerve cells, 3Na out/ 2K in
 Más Action PotentialDepolarization - makes membrane potential less negative
Hyperpolarization - makes membrane more negative

AP amplitude does NOT depend on stimulus strength


 Ionic Events during AP*****VERY IMPORTANT LOOK AT SLIDE******
  1. Conductance(g) of Na increases rapidly******
  2. (g)Na stops ∆ as Vm --> Eq Pot of Na******
  3. (g)K increases as Vm --> Eq Pot of Na**
  4. (g)Na decreases rapidly as Vm --> Eq Pot of K**
  5. (g)K decreases as Vm --> Eq Pot of K**
  6. Lingering decrease in (g)K - after-hyperpolarization
******Rising Phase (depolarization)
**Falling Phase (hyperpolarization)

 Hodgkin CycleRegenerative part of AP
Positive Feedback - speeds process up, does not turn it off
  • opens Na channels (sensitive to Voltage ∆)
  • wont quite reach Eq Pot of Na, Eq Pot = Limiting Factor

Membrane Depolarization--> Increase in (p)Na--> Na influx--> Depol
 Voltage-Gated ChannelsPositive feedback for Na influx into cell until reaches Eq Pot
  • before that point, Voltage gated channels for K open
  • K leaves the cell --> Negative FB
  • K continues Negative FB loop until after-hyperpolarization

 Nernst Equation & MiscFor the given Na concentration:
(E)Na = 0.058log( [Na outside] / [Na inside] )

Na moves into cell b/c [ ] differences
Na rushes in, (-) charge in cell, (+) charge outside cell

repolarization - allows cell to return to resting value

Na/K pumps keep the concentrations unequal across membranes
 Refractory PeriodSlowly recovering from AP
Absolute Refractory Period: No stimulus of any strength can produce an AP due to **inactivation of Na channels
Relative Refractory Period:  Strong stimulus can --> another AP but w/ a smaller amplitude due to **Na activation and still some K activation

Does not approach (E)Na as closely b/c K channels are still open,
**K channels need to be closed
 Continuous StimulusExcitability of memb decreases w/ time (threshold increases)

Physiological ∆ is called Accomodation
  • context dependent, some membranes accomodate faster than others 
Phasic response flatlines in the middle

tonic response creates new AP's, but each one is a little more spaced apart in time
 Channel DensityAxon Hillock = where AP is initiated
  • has high concentration of Voltage gated channels
  • lower threshold
  • shorter relative refractory period
 Graded vs Action Potential SummaryGraded:
Vary in Magnitude,  vary in duration,  decay w/ Distances
occur in dendrites and cell body,  caused by opening and closing of many kinds of ion channels

Action Potential:
always same magnitude,  always same duration,  can be transmitted long distances,  occur in axons, caused by opening and closing of voltage-gated ion channels
 Spread of Voltage along AxonResistance along axon causes decay of signal

Length Constant:   lambda = (Rm/Rl)^1/2
  • Rl = resistance along membrane
  • Rm = resistance across
Some neurons have different Length Constants
  • Larger Rm and a smaller Rl --> increase passive spread/ velocity or propagation
Net effect of increasing radius of Axon = increase in speed of conduction
 Propagation of Action PotentialsNerve cells that are short relative to length constant show graded responses, but signals = strong enough to cause neurotransmitters to be released
  • ∆ in memb potential --> signaling other neighboring cells

AP's = regeneration, (not a wave down axon)
  • AP's = 5x as large as threshold level --> safety factor, this extra depolarization --> membrane ahead of AP to depolarize and produce next AP

 Myelin
  • acts as an insulator
  • prohibits ions from moving across membrane
  • pushes depolarization further down axon



 Axons
Problems of Large axons 
  • take up a lot of space --> limits # of neurons that can be packed into nervous system
  • very expensive to produce and maintain
Squids and cucarachas have huge axons

Insulate axon w/ myelin
  • enables rapid signal conduction in a compact space

 Nodes of RanvierSpacings in b/w myelin
  • depolarizations --> Na to enter axon thru open channels --> AP's
  • depolarization encounters the next node -->
leapfrogging of AP's = saltatory conduction

Multiple Sclerosis - loss of myelin in Nervous System
  • slows down conduction of AP
  • muscle weakness, fatigue, vision loss, trouble walking
 SynapseConnection between two neurons:
  • Electrical - membranes fused
  • Chemical - graded response
 Electrical SynapseFusion of neurons in which there is physical contact
           Charge goes from A-->B, allows current to flow
Allows current AP in one cell to spread into other and depolarize it

Function = rapid transmission of signals
  • Synchronization of electrical activity in groups of neurons  (i.e. the heart's contractions - contrax needs to happen at same time)
  • Info = transfered in BOTH directions, No control of info flow
 Chemical SynapseNot physically connected  --> Gap between neurons = Synaptic Cleft      
            **Use of Neurotransmitters, receptors,
  • Terminal at rest -->
  • AP arrives; vesicles fuse w/ terminal membrane --> exocytosis of transmitter(Ca entry into terminal = req'd for NroTr release)
  • Transmitter binds to postsynaptic receptor proteins --> ion channels open
  • Transmitter is removed from cleft; fused membrane recycled
 Inactivation of Neurotransmitters
  • Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells (serotonin)
  • Enzymes inactivate neurotransmitters (Ach)
  • Neurotransmitters can diffuse out of synaptic cleft (norepinephrine)
Nicotine
  • binds to receptors selective to Ach & cause AP in postsynaptic cell & there is no enzyme to remove it
  • get muscles to contract when there shouldn't be contrax


 Types of Chemical TransmissionFast
  • NT release close to receptors
  • Receptors --> directly open ion channels
  • use of small vesicles (easy to release material)
Slow
  • NT release = distant from receptors
  • receptors indirectly open ion channels (use an intracellular messenger)
  • Use of large vesicles to release more NT's
 Major Known NeurotransmittersAcetylcholine
  • excitatory in vertebral skel muscles, inhibitory in others sites
  • CNS, PNS, vertebrate neuromuscular junction
Biogenic Amines (dopamine, NE, serotonin[CNS, inhib] )
  • Excitatory or inhibitory
  • CNS, PNS
Amino Acids (CNS, excitatory or inhib, invertebral neuromuscle junx)
Neuropeptides (CNS or PNS, excitatory or inhibitory)


 AcetylcholinePrimary NT at vertebrate neuromuscular junction
  1. Acetyl CoA = synth in mitochondria
  2. choline acetyl transferase catalyzes conversion of choline and acetyl CoA into ACh
  3. ACh packaged into synaptic vesicles
  4. ACh released & binds to receptor on PostSyn Cell
  5. AChE breaks down ACh into choline and acetate --> terminating the signal in PostSyn Cell
  6. PreSyn Cell takes up and recycles choline,   the acetates diffuse out of synapse
 Synaptic CurrentsEPP = sig/current prod'd in synapse (excitatory PostSyn Pot)Graded

Binding of NT on receptors of PostSyn membrane --> opening of PostSyn Channel (Na and K can pass through)
  • 2 Synaptic currents
  1. Inward syn current = Na
  2. Outward syn current = K
  • if only one or other ion can move across membrane then membrane Pot --> Eq Pot for that ion
New Eq estab'd with this phenomena --> Reversal Pot (E rev)
 Eq Potentials and Rev PotentialsIf E(rev) = Vm --> no ∆
If E(rev) > Vm --> Depolarization(more Na moving across,  excitatory)
If E(rev) < Vm --> Hyperolarization (more K moving across,  inhibitory)

Thus the Value of Reversal Potential = essential in distinguishing b/w excitatory and inhibitory synapse

***Chemical Synapse acts as Switch in neural circuits (Yes or No AP)
  • Exc and Inhib PostSyn Signals = integrated in same PostSyn Cell
 Summation of Postsynaptic Potentials
  • Subthreshold --> No AP
  • Temporal Summation --> AP (summation over time)
  • Spatial Summation --> AP (summation over space)
  • Spatial Summation of EPSP and IPSP --> No AP

 Presynaptic InhibitionInhib synapse on top of excitatory synapse
  • Renshaw cells --> control overstimulation of muscle cells normally release inhib NT (glycine) onto motor neurons to prevent excessive muscle contrax
Strychnine Poisoning
  • Strychnine binds to and blocks glycine receptors in spinal cord
  • Massive contrax of all skel muscles, convulsions
  • diaphragm contrax --> no breathing
  • fatal within 3 hours
 Summary of Electrical and Chemical SynapsesElectrical Synapse
  • Rare in complex animals, common in simple animals
  • fast, bi-directional
  • excitatory
  • Postsynaptic signal is similar to presynaptic
Chemical Synapse
  • Common in complex animals, rare in simple animals
  • Slow, unidirectional
  • excitatory or inhibitory
  • Postsynaptic signal can be different
 Sensory ModalitiesChemoreceptors
Mechanoreceptors
Photoreceptors
Thermoreceptors
Electroreceptors
 Receptor Cellconversion of receptor potential into propagated impulses
  • receptor is not regenerative (NO Hodgkin Cycle)
Stimulus --> small receptor potential --> AP
  • Receptor current spreads electronically to spike initiation zone
  • Or ∆ NT release to produce AP in secondary neuron

Stimulus --> receptor --> G protein --> effector enzyme --> 2nd Messenger molecule --> ion channel
 Receptor Events****Look at Slides****
Transduction
  • Stimulus reaches receptor cell
  • Receptor protein activated
Amplification
  • Cascade of protein interax modifies intracell. 2nd messengers
  • Ion channels open (or close)
∆ in Conductance --> receptor current
Receptor current ∆ Vm --> Spike initiation zone/transmitters released
  • # and/or ƒ of AP along axon ∆ (afferent)  (  All or None AP's)
 Stretch Receptor Cell
  • Muscles stretch
  • stretch receptor cell measures the stretching of muscles

  • converts stimulus to graded and later to AP and AP sent



 Stimulus-Response RelationshipThe Stronger the Stimulus --> the more AP's produced per unit of time

Stimulus intensity = semilogarithmic relat to response 
Refractory periods and only so much receptor potential = reason

Sensory Quality--> Spec. sensor cell connected CNS
  • Intensity = temporal distribution
  • Input-Output = semi-log relat (see above)



 Input-Output RelationsReceptor response = proportional to log of stimulus intensity
  • high intensity of scale becomes compressed (extending dynamic range of detection)
  • Sunlight = 10^9 times más strong than moonlight
  • Human auditory system can detect 12 orders of magnitude of sound
Dynamic Range of Detection = certain range of stimulus intensity
  • Upper limit of receptor current (finite # ion channels)
  • Upper lim of amplif of receptor Pot (Cant exceed Revers Pot)
  • Upper limit of on AP ƒ (refractory period)
 Range FractionationDifferent cells w/ different but overlapping sensitivities (extends dynamic range)

Response to stimuli of Const Intensity
  • Tonic and phasic receptor cells
Adaptation of receptor cell to continued stimulus
 Sensory Adaptation4 possible mechanisms:
  1. Depletion of receptor molecules (rhodopsine in eyes)
  2. ∆ in electrical properties of receptor cell                              Activation of Ca dependent K channels due to más [Ca]
  3. Accessory structures --> time dep. ∆ (pupil adjustment)
  4. Accomadation --> a drop in sensitivity of receptor cell due to depolarization
Function = extend dynamic range, allowing detection of weak & strong stimuli
  • tonic receptors = pain, danger sits   phasic = noise
 Lateral InhibitionExample = color chart of same intensity
  • used to enhance contrast

vision and hearing = uses of this
 ChemoreceptionGustatory organs --> taste (gustation), have taste pores

Olfactory Organs --> smell,  insects have larger pores(better smellers)

4 Basic tastes:
  1. Sweet
  2. Sour
  3. Salty
  4. Bitterness

 Sensory TransductionTaste Receptors 
  • ligand binds to receptor-->
  • Signal Transduction Pathway-->
  • K+ channels close, Ca and Na channels open (influx & Depol)
  • stimulates release of NT's
Taste:
Ensemble coding --> groups of neurons send "pieces" of sensory "puzzle" to brain where pieces put together
Labeled Line Coding --> very selective sensor cells  analogous to calling a specific person in phone 
 OlfactionSends signals directly to brain (Maybe why smells are remembered better)
  • VNO - chamber used to process sexual communication (sex pheromones)
Odoroant binds to receptor --> G protein --> Adenylate Cyclase (ATP for prod of cAMP) --> cAMP binds to Cyclic Nucleotide gated cation channel
Glomerulus - cluster of neurons that receive info from receptor cells w/ similar selectiveness (1st place of sensory processing)
  • not in taste cells
 Sensory PathwaysOlfactory -->cortex (directly)

Every other sense passes through Thalamus(center for processing info) and then projected to relevant cortical area

Equilibrium pathways project to cerebellum w/ a branch to the cortex via thalamus
 Sensory Processing
  1. Somatosensory cortex
  2. sensory association areas (integration of all sensory input)
  3. Visual cortex
  4. Olfactory cortex

Look at slides


 Somatosensory ProcessingSomesthetic (Body feelings) - touch, pain, temp, pressure

information is projected to the somatosensory cortex

Somototopic Order in Sensory Cortex
  • More surface area in brain --> more information processing
  • therefore is more important
 HearingSound: Alternation of high and low pressure waves

Detected by special mechanoreceptor cells (hair cells)

Features of Sound-->
  • Pitch/tone (deps on ƒ)
  • Intensity/loudness (deps on amplitude)
  • Timbre/Quality (deps on overtones)
 Hearing: Its Mechanoreceptors
  1. Sound waves strike tympanic membrane --> Vibrations
  2. Sound wave E transfered to 3 bones of middle ear and vibes
  3. Stapes attached to membrane of oval window, vibrations of oval window create fluid waves w/in cochlea
  4. Fluid waves push the flexible membrane of cochlear duct
  5. E from waves transfer across cochlear duct and is dissipated back into the middle of ear at the round window
  6. Hair cells w/in cochlear duct creates AP's in sensory neurons of cochlear nerve
  • Organ of Corti = Important for Hearing
36, "/var/app/current/tmp/"