neuromuscular structure and function

Question 1

what is the function of the cerebral cortex

Answer 1

• language
• reasoning and abstract thinking
• sensory and voluntary motor control

Question 2

what is the function of the basal ganglia

Answer 2

• initiation and execution of movements
• facilitate desired movements and inhibit unwanted competing movements
  (chooses actions that are likely to lead to positive consequences)

Question 3

what is the function of the hypothalamus

Answer 3

• metabolism and temp
• autonomic NS (cardiovascular and cardiorespiratory rhythm)

Question 4

what is the function of the limbic system

Answer 4

• processing and interpretation of sensory info
• controls motivation and goal directed behaviour influencing the initiation and maintenance of exercise routines
• promotes adaptive reactions to physical challenges and aids in the management of stress related hormones

Question 5

what does the limbic system release and what is the function

Answer 5

• release of endorphins that contribute to the feelings of pleasure and euphoria (runners high)
• leads to improved mood and reduced perception of pain during PA (exercise induced hypoalgesia - pain reduction)

Question 6

what is the function of the brainstem

Answer 6

• passage connects motor and sensory neurons to the spinal cord
• contain nuclei that regulate the cardiac and respiratory functions

Question 7

what is reduced vagal tone from brainstem

Answer 7

increased sympathetic nerve activation therefore increased HR and ventilation

Question 8

what is the function of the cerebellum

Answer 8

• processes the info necessary to regulate body posture and equilibrium (balance)
• receives sensory info form sensory afferents
• sends info to thalamus and than cerebral cortex

Question 9

what is the corticospinal tract

Answer 9

collection of axonal nerves bundles (white matter) initiating at the cerebral cortex, passing through the brainstem and terminating on lower MNs

Question 10

what occurs at the pyramidal decussation

Answer 10

90% decussate - lateral CST controls extremities
10% don’t decussate - ventral CST controls trunk and core muscles

Question 11

how many pairs of spinal MNs are there

Answer 11

31

Question 12

what is the pathway of a spinal cord reflex

Answer 12

1. stimulus
2. afferent pathway
3. monosynaptic connection (afferent neuron connects directly to efferent neuron)
4. efferent pathway

Question 13

how long does a spinal cord reflex take

Answer 13

<150 ms
- doesn’t go all the way to the brain

Question 14

what is a MU made up of

Answer 14

an aMN and the specific muscle fibres that it innervates
- makes up the functional unit of mvmt

Question 15

what is the difference in ratios between small and large MUs (aMN:muscle fibres)

Answer 15

small = 1:5 - fine mvmt
large = 1:800 - gross mvmt

Question 16

what are the 3 stages of an AP

Answer 16

1. depolarisation (influx of Na+)
2. repolarisation (outflux of K+)
3. ions return back with Na+/K+ pumps

Question 17

what does the speed of conduction depend on

Answer 17

unmyelinated vs myelinated
(nociceptors = unmyelinated)
- saltatory conduction on myelinated nerves

Question 18

what occurs when an AP reaches the NM junction

Answer 18

1. presynaptic terminal - AP reaches and releases ACh
2. ACh travels across the synaptic cleft
3. postsynaptic terminal - AP generates here due to ACh receptors
4. synaptic vesicles contain ACh
5. AP goes to t-tubule and touches sarcoplasmic reticulum causing Ca2+ release

Question 19

what is the function of the spinal reflex

Answer 19

used for anything related to maintaining balance quickly
- skating, running on unstable surfaces, etc

Question 20

what is the all or none principle

Answer 20

all muscle fibres innervated in a MU are stimulated to contract

Question 21

what is the size principle

Answer 21

anatomic basis for the orderly recruitment of small to large MUs to produce a smooth muscle action

Question 22

what is recruitment

Answer 22

increasing the number of MUs recruited
- occurs first

Question 23

what is rate coding

Answer 23

increasing frequency of MUs discharge
- occurs second

Question 24

what is the order of recruitment and rate coding during exercise

Answer 24

both increase as exercise intensity increases
- recruitment = first
- rate coding = second

Question 25

what are muscle spindles

Answer 25

fusiform structure embedded in the muscle - monosynaptic - no interneuron

Question 26

what do muscle spindles respond to

Answer 26

any stretch of the muscle - provides mechnosensitive info about changes in muscle fibre lngth and tension - sends info to spinal cord and sends excitatory info back to the aMNs

Question 27

what do nuclear bag fibres respond to

Answer 27

phasic stretch (changes in stretch)

Question 28

what do nuclear chain fibres respond to

Answer 28

static stretch (maintained stretch)

Question 29

where are GTOs

Answer 29

in the muscle tendon unit

Question 30

what are GTOs

Answer 30

responds to the tenison created by muscle contraction (active force production NOT stretching) - protective sensory mechanism

Question 31

what do GTOs do

Answer 31

reduces the level of muscle contraction and tension in the muscle - has an inhibitory interneuron that inhibits the aMN during dangerously high active force production (main difference from muscle spindle)

Question 32

what is the stretch (myotatic) reflex

Answer 32

involuntary contractions of muscle from a rapid stretch - only involves afferent and efferent neurons and 1 synapse - spinal cord only

Question 33

what is the function of the stretch reflex

Answer 33

helps the body to maintain its balance in a fraction of a second - tiny adjustments all the time to keep standing