Lecture 7 - Neuromuscular System II

Question 1

Fatigue

Answer 1

Build up of waste products in muscles, depleted ATP and how one feels

Fatigue is used to describe a non-specific but debilitating symptom in a range of chronic diseases and disorders such as cancer ( symptom in a medical sense)

Fatigue vs fatiguability

Perceived fatigue ( subjective feeling )

Performance Fatigability (sports sense and one we will be studying)

Contractile function and muscle activation are sub catagaroies of Performance Fatigability

Question 2

Neuromuscular fatigue

Answer 2

-A failure to maintain a required submaximal force during a given task

• An exercise-induced decline in maximal muscle force or power production capacity

Question 3

Organization of neuromuscular system

Answer 3

Central nervous system
* Brain
* Spinal cord

Peripheral nervous system
* Peripheral nerves
* Neuromuscular junction
* Muscle units

Question 4

Order of neuromuscular system

Answer 4

Motor cortex to internal capsule to medulla to anterior/lateral corticospinal tract to lower motor neurone

Question 5

Spinal cord

Answer 5

Motor nerves (efferent)

Pyramidal tract – voluntary movements
* 31 pairs of spinal motor nerves
* 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal

2. Sensory nerves (afferent)
   (going back to brain)
3. Interneurons

Question 6

Role of spinal interneurons

Answer 6

-Process sensory input
- Modulate motor output
- Relay proprioceptive data

Contain excitatory & inhibitory neurotransmitters

E.g., excitatory reflex response - move foot when step on thorn
E.g., inhibit antagonist muscles - contract muscle

Question 7

Motor Unit

Answer 7

Makes up the functional unit
of the movements
* Consists of an ⍺-motoneurone
and the specific muscle fibres
that it innervates
* Difference in muscle fibre-
motor unit ratio (e.g., 1:5 or
1:800) contributes to variation
in motor skills
* All or none principle: All of
the muscle fibres innervated
in a motor neuron are
stimulated to contract

Question 8

Neuromuscular junction

Answer 8

Presynaptic terminal
* Synaptic cleft
* Postsynaptic terminal
* Synaptic vesicles
* Acetylcholine (ACh)

Question 9

Muscle wisdom

Answer 9

Sustained isometric contraction = increasing fatigue

• Muscle wisdom theory proposed that slowing firing
  frequency of recruited motor units could serve to
  minimize fatigue
• Slower firing rate helps reduce metabolic demand in
  muscles while maintaining performance