Neuromuscular Structure and Function

Question 1

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Peripheral nervous system
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which is allostatic(feedforward)
- increased adrenaline BEFORE competition

Answer 1

Central nervous system
- The Brain
- The Spinal cord
Peripheral nervous system
- Spinal nerves (autonomic and somatic)
- Muscle units

Question 2

• Cerebral cortex (……………………)

THE LIMBIC SYSTEM
* Processing and interpretation of … information
* Release of …, such as … that contributes to “…”
* Improved mood and … during PA. CALLED …
* Controls … and goal-directed behavior,
* Aids in the management of ..

Answer 2

• Cerebral cortex (Language, reasoning and abstract thinking, sensory and voluntary motor control)

THE LIMBIC SYSTEM - hippocampus, amygdala, hypothalamus, and thalamus
* Processing and interpretation of sensory information
* Release of neurotransmitters, such as endorphins that contributes to “runner’s high”.
* Improved mood and reduced perception of pain during PA. EXERCISE INDUCED HYPOAGLESIA
* Controls motivation and goal-directed behavior,
* Aids in the management of stress-related hormones.

Question 3

Hypothalamus - EXAM
- … and …
- … nervous system (cardio-vascular and cardio-respiratory rhythm)

Brain stem
- …
- …
- …

• Contain nuclei that regulate the … functions
• A … connects motor and sensory neurons to the spinal cord.

EXAM
* Reduced vagal tone (less parasympathetic) vs. Sympathetic nerve activation.
Both contribute to HR at onset of exercise

Answer 3

Hypothalamus
- Metabolism and temperature
- Autonomic nervous system (cardio-vascular and cardio-respiratory rhythm)

Brain stem - MPM
- Midbrain
- Pons
- Medulla oblongata

• Contain nuclei that regulate the cardiac and respiratory functions
• A passage connects motor and sensory neurons to the spinal cord.
• Reduced vagal tone vs. Sympathetic nerve activation

Question 4

EXAM
1) Motor nerves (…)
* Pyramidal tract (… movements)
* … pairs of spinal motor nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal)
2) Sensory nerves (…)
3) Interneurons
* if they exist, it is …

Motor unit - EXAM
* Makes up the … of the movements
* Consists of an … and the … that it innervates. In GRAY matter
* Difference in motor neurone-muscle fiber ratio (e.g. … or …) contributes to variation in …

• All or None principle(WITHIN ONE UNIT): …

Answer 4

1) Motor nerves (efferent) - motor commands to muscle
* Pyramidal tract (voluntary movements)
* 31 pairs of spinal motor nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal)
2) Sensory nerves (afferent) from muscle back to brain
3) Interneurons
* if they exist, it is not EXCITATORY, it is INHIBITORY

Motor unit
* Makes up the functional unit of the movements
* Consists of an alpha motoneurone and the specific muscle fibers that it innervates
* Difference in motor neurone-muscle fiber ratio (e.g. 1:5 or 1:800) contributes to variation in motor skills. 800 is a bigger muscle (quad), small muscle like fingers is a lower ratio, better control

• All or None principle: All of the muscle fibers innervated in a motor neuron are stimulated to contract. In muscle fibre, when alphamotoneuron activation, all fibres are actviatited

Question 5

Action potential (AP)

• A wave of … that propagates along the surface of a nerve or muscle
• Produced by changes in the …
• Includes three stages
  1) Depolarization (…)
  2) Repolarization (…)
  3) Ions … with NA+/K+ pumps

Saltatory conduction
- when there are myelin sheaths insulators the conduction is faster, and ions are concentrated between sheaths, acts as an accelerator

Answer 5

Action potential (AP)

• A wave of depolarization that propagates along the surface of a nerve or muscle
• Produced by changes in the membrane potential
• Includes three stages
  1) Depolarization (influx of NA+)
  2) Repolarization (outflux of K+)
  3) Ions return back with NA+/K+ pumps

Question 6

Neuromuscular junction (motor endplate) - EXAMMMM
* Presynaptic terminal - AP reaches
* Synaptic cleft - ACh released across
* Postsynaptic terminal - binds to Na+ receptors
* Synaptic vesicles - Na+ in, stimulated SR, Ca2+ out
Ca binds to troponin, moves tropomyosin, myosin head binds to actin
ATP detaches myosin from actin, and hydrolysis of ATP arms it

• Acetylcholine

Answer 6

Neuromuscular junction (motor endplate)
* Presynaptic terminal
* Synaptic cleft
* Postsynaptic terminal
* Synaptic vesicles
* Acetylcholine

Question 7

Muscle twitch characteristics

• Large motor neurones with fast conduction velocity innervate … and … muscle fibers.
• Smaller motor neurones with slow conduction velocity innervate … muscle fibers
• FF – type … muscle fibers
• FR – type … muscle fibers
• S – Type …
• SURGICALLY innervating FF muscle Fibers with the NEURONS from a slow- twitch muscle fiber eventually alters the twitch characteristics of FF motor unit.
• The type of fibre is determined by the alpha motor neuron with a soma in the spinal cord. if you cut it and connect it to another muscle group, characteristics can change

POWER and contractile speed?

Answer 7

Muscle twitch characteristics

• Large motor neurones with fast conduction velocity innervate fast- fatigable (FF) and fast fatigue- resistant (FR) muscle fibers.
• Smaller motor neurones with slow conduction velocity innervate slow (S) muscle fibers
• FF – type IIx muscle fibers. not long
• FR – type IIa muscle fibers. ENDURANCE = ANDURANCE
• S – Type I. very long
• Surgically innervating FF muscle Fibers with the neurons from a slow- twitch muscle fiber eventually alters the twitch characteristics of FF motor unit.

I > IIa > IIx

Question 8

Motor unit recruitment

1) Recruitment: increasing the …
2) Rate coding: Increasing …

• The size principle(WITHIN WHOLE MUSCLE): lower and slower movements … larger and faster movements …

Muscle spindles
* Provides mechano-sensitive information about changes in … and …
* Responds to any … of the muscle

EXAMMMMM
* Nuclear chain fibers: responds to … stretch
* Nuclear bag fibers: responds to … stretch
* … the level of muscle contraction

Answer 8

Motor unit recruitment

1) Recruitment: increasing the number of motor units recruited
2) Rate coding: Increasing frequency of motor units discharge

• The size principle: lower and slower movements (type 1) larger and faster movements (type 2a/x)

Muscle spindles
* Provides mechano-sensitive information about changes in muscle fiber length and tension.
* Responds to any stretch of the muscle

EXAMMMMM
* Nuclear bag fibers: responds to phasic stretch (b and p). dynamic and changing length
* Nuclear chain fibers: responds to static stretch, chain hold still and remains tension
* Increases the level of muscle contraction

Question 9

Stretch Reflex (myotatic reflex)
* An involuntary … of muscles induced by a … of the muscle
* This reflex arc involves … nerves and … synapse
* Helps the body to maintain its …
* Even in standing still, continual sub- conscious stretch reflex activities make many tiny adjustments to keep the body erect

Golgi tendon organs
* Responds to the … created by … , NOT…
* Protective … mechanism
* … the level of muscle contraction

Answer 9

Stretch Reflex (myotatic reflex)
* An involuntary contractions of muscles induced by a stretch of the muscle
* This reflex arc involves only two nerves and one synapse
* Helps the body to maintain its balance.
* Even in standing still, continual sub- conscious stretch reflex activities make many tiny adjustments to keep the body erect

Golgi tendon organs
* Responds to the tension created by muscle contraction, NOT muscle stretching
* Protective sensory mechanism
* Reduces the level of muscle contraction