Koofers

chapter 11 - Flashcards

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Class:PHED 35345 - Exercise Physiology (with lab)
Subject:Physical Education
University:Rowan University
Term:Fall 2014
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Neuromotor system organization central nervous system (CNS) brain
spinal cord
Neuromotor system peripheral nervous system (PNS) 12 cranial nerves
31 pairs of spinal nerves
neurotransmitters chemical messengers: diffuse across a synapse to combine with targeted receptor molecule on postsynaptic membrane to facilitate depolarization or hyperpolarization
Peripheral nervous system
  • 31 pairs of spinal nerves- 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccgeal
  • 12 pairs of cranial nerves- afferent nerves: relay sensory info, from muscles, joints, skin, bones toward brain. Efferent nerves: transmit info away from brain to glands and muscles
  • somatic and autonomic nervous system
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components of PNS somatic
  • innervates skeletal muscle
  • somatic efferent nerve firing excites muscle activation
autonomic reflex arc: patellar reflex*
complex reflexes: crossed- extensor reflex *
Nerve supply to muscle
  • about 420,000 motor nerves exist; a single nerve usually supplies numerous individual muscle fibers.
  • ratio of muscle fibers to nerves relates to muscle's particular movements
  • basic rule: less complex movements have a higher ratio of muscle fibers to motor nerves. Complex eye and hand movements requiring more specialized movements have a considerably lower ratio
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motor units skeletal muscle fibers and their corresponding innervating anterior (alpha) motor neuron:
  • represents movements functional unit
  • whole muscle contains many motor units, each with a single motoneuron and its composite muscle fibers
motor unit anatomy cell body houses control center
  • axon extends from cord and delivers impulse to muscle fibers it nnervates
  • dendrites receive impulses through spinal cord connections and conduct them toward the cell body
  • nerve cells conduct impulses in one direction only-- down axon away from stimulation point
  • all of a motor units muscle fibers disperse over subregions of muscles with other motor unit fibers
facilitation
  • motoneuron generates action potential when its microvoltage decreases to reach its threshold for excitation
  • effective disinhibition fully activates muscle groups during max muscular efforts
  • enhanced neuromuscular activation accounts for considerable improvments in muscular strength without concurrent increases in muscle size
Inhibition
  • presynaptic terminals generate inhibitory impulses by releasing chemicals that increase postsynaptic membrane permeability to K+ and Cl- 
  • increases membrane resting electrical potential to create inhibitory postsynaptic potential that makes neuron firing more difficult
  • gamma- aminobutyric acid and glycine exert inhibitory effects
  • neural inhibition serves protective functions and reduces input of unwanted stimuli to produce smooth, purposeful responses.
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Motor unit characteristics twitch characteristics
  • in response to single elctrical impulse, some motor units develop high twitch tensions, others develop low twitch tensions. and remainder generate intermediate twitch tension
motor unit tension-generating characteristics
  • different motor units and muscles develop different amounts of tension
motor unit three factors govern tension development
  1. all or none principle
  2. gradation of  force principle
  3. level of motor unit recruitment patterns
fiber types
  • fast fatigable (FF)  force production- high. Contraction speed- fast. Fatigue resistance- low. muscle fiber type- fast glycolytic. SAG- yes
  • fast fatigue-resistance (FR)- force production- moderate. speed- fast. resistance- moderate. SAG-yes. type- fast-oxidative- glycolutic (FOG)
  • slow (S)- force production- low. speed-slow. resistance- high. SAG- No. type- Slow-oxidative (SO)

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three physiologic and mechanical motor unit and muscle properties of innervation
  1. twitch ( speed of contraction) characteristics
  2. tension-generating (force) characteristics
  3. neuromuscular fatigability
all of none principle
  • all accompanying muscle fibers act synchronously if stimulus triggers a motoneuron's action potential.
  • single motor unit cannot generate strong and weak contractions- an impulse either elicits an action or it does not
  • once the neuron fires and the impulse reaches the neuromuscular junction. muscles cells always act to their fullest extent
gradution of force principle
  • force of muscle action varies from slight to max in one of two ways:
  1. increasing number of recruited motor units
  2. increasing frequency of motor unit discharge
motor unit recruitment
  • process of adding motor units to increase force
  • size principle: motoneurons with progressively larger axons become recruited as muscle force increases
  • selective recruitment and firing pattern of fast-twitch and slow-twitch motor units that control movement serve as the mechanism to produce the desired, coordinated response


relative to intensity
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neuromuscular fatigability
  • decline in muscle tension or force capacity with repeated stimulation 
  • four factors decrease force-generating capacity:
  1. PA  induced alterations in levels of neurotransmitters
  2. reduced glycogen content in active muscle fibers occurs during prolonged PA
  3. increased levels of blood and muscle lactate
  4. fatigue occurs at the neuromuscular junction
proprioceptors
  • specialized sensory receptors sensitve to stretch, tension, and pressure in muscle, joints, tendons
  • relay critical information about: muscular dynamics, limb position, kinesthesia, proprioception to conscious and subconscious portions of the CNS
  • allow continual monitoring of progress of any movement or sequence of movements and provide the framework for modifying subsequent motor actions
muscle spindles
  • provide mechanosensory info. about changes in muscle fiber length and tension
  • respond to muscle stretch through reflex action by initiating a stronger muscle action to counteract the stretch
  • more spindles exist in muscles that routinely perform complex movements
stretch reflex stretch reflex consists of three parts
  1. muscle spindles: responds to stretch
  2. afferent nerve fibers: carries sensory impulse from spindle to spinal cord
  3. efferent spinal cord motor neuron: activates stretched muscle fibers
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gogi tendon organs
  • connect in series to extrafusal fibers and also located in joint ligaments to detect differences in muscle tension than length
  • when activated by muscle tension or stretch, golgi receptors immediately transmit signals to cause reflex inhibition
  • protect muscle and its connective tissue harness from injury by sudden excessive load or stretch
muscle chemical composition
  • 75% water
  • 20% protein
  • 5% inorganic salts, high-energy phosphates, enzymes pigments NA+ K+ Cl- amino acids fats, carbs
fast twitch muscle fiber characteristics
  • four major characteristics
  1.  rapidly transmit action potentials
  2. high activity level of myosin ATPase
  3. rapid rate of Ca2+ release and uptake by sarcoplasmic reticulum
  4. generate rapid crossbridge turnover
Fast-twitch type 2 subdivisions
  • type 2a fiber- exhibits fast shortening speed and well-developed capacity for energy transfer from aerobic and anaerobic sources. Represents fast-oxidative- glycolytic fibers
  • type 2x fiber- possesses greatest anaerobic potential and rapid shortening velocity. Represents fast-glycolytic fiber 
  • type 2c fiber
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slow twitch muscle fibers
  • generates energy for ATP resynthesis via aerobic energy transfer
  • possess low activity level of myosin ATPase, slow contraction speed, glycolytic capacity less developed than fast-twitch fibers
  • resist fatigue and power in prolonged aerobic PA
  • slow oxidative fibers
muscle fiber type distribution differences
  • individual differences prevalent in muscle fiber type distribution
  • genetic code largely determines the predominant fiber type
  • specific training improves metabolic capacity of each fiber type
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 Neuromotor system organization central nervous system (CNS)brain
spinal cord
 Neuromotor system peripheral nervous system (PNS)12 cranial nerves
31 pairs of spinal nerves
 neurotransmitterschemical messengers: diffuse across a synapse to combine with targeted receptor molecule on postsynaptic membrane to facilitate depolarization or hyperpolarization
 Peripheral nervous system
  • 31 pairs of spinal nerves- 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccgeal
  • 12 pairs of cranial nerves- afferent nerves: relay sensory info, from muscles, joints, skin, bones toward brain. Efferent nerves: transmit info away from brain to glands and muscles
  • somatic and autonomic nervous system
 components of PNS somatic
  • innervates skeletal muscle
  • somatic efferent nerve firing excites muscle activation
 autonomic reflex arc:patellar reflex*
 complex reflexes:crossed- extensor reflex *
 Nerve supply to muscle
  • about 420,000 motor nerves exist; a single nerve usually supplies numerous individual muscle fibers.
  • ratio of muscle fibers to nerves relates to muscle's particular movements
  • basic rule: less complex movements have a higher ratio of muscle fibers to motor nerves. Complex eye and hand movements requiring more specialized movements have a considerably lower ratio
 motor unitsskeletal muscle fibers and their corresponding innervating anterior (alpha) motor neuron:
  • represents movements functional unit
  • whole muscle contains many motor units, each with a single motoneuron and its composite muscle fibers
 motor unit anatomycell body houses control center
  • axon extends from cord and delivers impulse to muscle fibers it nnervates
  • dendrites receive impulses through spinal cord connections and conduct them toward the cell body
  • nerve cells conduct impulses in one direction only-- down axon away from stimulation point
  • all of a motor units muscle fibers disperse over subregions of muscles with other motor unit fibers
 facilitation
  • motoneuron generates action potential when its microvoltage decreases to reach its threshold for excitation
  • effective disinhibition fully activates muscle groups during max muscular efforts
  • enhanced neuromuscular activation accounts for considerable improvments in muscular strength without concurrent increases in muscle size
 Inhibition
  • presynaptic terminals generate inhibitory impulses by releasing chemicals that increase postsynaptic membrane permeability to K+ and Cl- 
  • increases membrane resting electrical potential to create inhibitory postsynaptic potential that makes neuron firing more difficult
  • gamma- aminobutyric acid and glycine exert inhibitory effects
  • neural inhibition serves protective functions and reduces input of unwanted stimuli to produce smooth, purposeful responses.
 Motor unit characteristics twitch characteristics
  • in response to single elctrical impulse, some motor units develop high twitch tensions, others develop low twitch tensions. and remainder generate intermediate twitch tension
 motor unit tension-generating characteristics
  • different motor units and muscles develop different amounts of tension
 motor unit three factors govern tension development
  1. all or none principle
  2. gradation of  force principle
  3. level of motor unit recruitment patterns
 fiber types
  • fast fatigable (FF)  force production- high. Contraction speed- fast. Fatigue resistance- low. muscle fiber type- fast glycolytic. SAG- yes
  • fast fatigue-resistance (FR)- force production- moderate. speed- fast. resistance- moderate. SAG-yes. type- fast-oxidative- glycolutic (FOG)
  • slow (S)- force production- low. speed-slow. resistance- high. SAG- No. type- Slow-oxidative (SO)

 three physiologic and mechanical motor unit and muscle properties of innervation
  1. twitch ( speed of contraction) characteristics
  2. tension-generating (force) characteristics
  3. neuromuscular fatigability
 all of none principle
  • all accompanying muscle fibers act synchronously if stimulus triggers a motoneuron's action potential.
  • single motor unit cannot generate strong and weak contractions- an impulse either elicits an action or it does not
  • once the neuron fires and the impulse reaches the neuromuscular junction. muscles cells always act to their fullest extent
 gradution of force principle
  • force of muscle action varies from slight to max in one of two ways:
  1. increasing number of recruited motor units
  2. increasing frequency of motor unit discharge
 motor unit recruitment
  • process of adding motor units to increase force
  • size principle: motoneurons with progressively larger axons become recruited as muscle force increases
  • selective recruitment and firing pattern of fast-twitch and slow-twitch motor units that control movement serve as the mechanism to produce the desired, coordinated response


relative to intensity
 neuromuscular fatigability
  • decline in muscle tension or force capacity with repeated stimulation 
  • four factors decrease force-generating capacity:
  1. PA  induced alterations in levels of neurotransmitters
  2. reduced glycogen content in active muscle fibers occurs during prolonged PA
  3. increased levels of blood and muscle lactate
  4. fatigue occurs at the neuromuscular junction
 proprioceptors
  • specialized sensory receptors sensitve to stretch, tension, and pressure in muscle, joints, tendons
  • relay critical information about: muscular dynamics, limb position, kinesthesia, proprioception to conscious and subconscious portions of the CNS
  • allow continual monitoring of progress of any movement or sequence of movements and provide the framework for modifying subsequent motor actions
 muscle spindles
  • provide mechanosensory info. about changes in muscle fiber length and tension
  • respond to muscle stretch through reflex action by initiating a stronger muscle action to counteract the stretch
  • more spindles exist in muscles that routinely perform complex movements
 stretch reflexstretch reflex consists of three parts
  1. muscle spindles: responds to stretch
  2. afferent nerve fibers: carries sensory impulse from spindle to spinal cord
  3. efferent spinal cord motor neuron: activates stretched muscle fibers
 gogi tendon organs
  • connect in series to extrafusal fibers and also located in joint ligaments to detect differences in muscle tension than length
  • when activated by muscle tension or stretch, golgi receptors immediately transmit signals to cause reflex inhibition
  • protect muscle and its connective tissue harness from injury by sudden excessive load or stretch
 muscle chemical composition
  • 75% water
  • 20% protein
  • 5% inorganic salts, high-energy phosphates, enzymes pigments NA+ K+ Cl- amino acids fats, carbs
 fast twitch muscle fiber characteristics
  • four major characteristics
  1.  rapidly transmit action potentials
  2. high activity level of myosin ATPase
  3. rapid rate of Ca2+ release and uptake by sarcoplasmic reticulum
  4. generate rapid crossbridge turnover
 Fast-twitch type 2 subdivisions
  • type 2a fiber- exhibits fast shortening speed and well-developed capacity for energy transfer from aerobic and anaerobic sources. Represents fast-oxidative- glycolytic fibers
  • type 2x fiber- possesses greatest anaerobic potential and rapid shortening velocity. Represents fast-glycolytic fiber 
  • type 2c fiber
 slow twitch muscle fibers
  • generates energy for ATP resynthesis via aerobic energy transfer
  • possess low activity level of myosin ATPase, slow contraction speed, glycolytic capacity less developed than fast-twitch fibers
  • resist fatigue and power in prolonged aerobic PA
  • slow oxidative fibers
 muscle fiber type distribution differences
  • individual differences prevalent in muscle fiber type distribution
  • genetic code largely determines the predominant fiber type
  • specific training improves metabolic capacity of each fiber type
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