Nerves, MUs, planes, axes

Question 1

Function of the spinal cord

Answer 1

To transmit signals from the brain to the peripheral nervous system and from the peripheral nervous system to the brain

Question 2

What is the role of the nervous system

Answer 2

The nervous system collects information from external and internal stimuli,
processes the information, and initiates and controls the response of the
musculoskeletal system to the stimuli

Question 3

Cranial and spinal nerves

Answer 3

12 pairs of cranial nerves that pass from the brain through openings in the skull to the head, chest, neck and abdomen
31 pairs of spinal nerves that orignate from the SC, which pass through openings between the vertebrae on each side and then form different plexuses

Question 4

5 plexi of the spinal nerves

Answer 4

Cervical
Branchial
Lumbar
Sacral
Pudendal

Question 5

Motor neurons consist of

Answer 5

Cell body
Dendrites
Axon
Nodes of Ranvier
Terminal branches

Question 6

Where is the cell body located

Answer 6

Located within the spinal cord (CNS)

Question 7

What do dendrites do

Answer 7

transmit impulses from the CNS to the cell body
The dendrites of motor neurons synapse with thousands of other neurons. Some may be inhibitory, others excitatory

Question 8

Role of the axon

Answer 8

Transmits impulses away from the cell body, towards the muscle

Question 9

How does an impulse travel from the cell body to the terminal brances

Answer 9

Dendrites receive information from surrounding tissue within the CNS and conduct nerve impulses to the cell body
If the impulse exceeds the threshold of the cell body, an AP is sent from the cell body down to the muscle fibres that the motor neuron innervates with

Question 10

What is a motor unit

Answer 10

A single motor neuron and all the muscle fibres that it innervates

Question 11

If a movement needs greater precision, what size of motor units will there be?

Answer 11

Small motor units
Motor units with motor neurons that innervate fewer muscle fibres are associated with greater precision

Question 12

If a movement needs greater force generation, what size of motor units will there be?

Answer 12

Large motor units
Motor units with motor neurons that innervate many muscle fibres are associated with greater force generation

Question 13

How does the impulse travel across the NMJ?

Answer 13

ACh is released and binds to receptors on sarcolemma, causing it to depolarise
This initiates muscle contraction

Question 14

What does an influx of sodium ions do?

Answer 14

An influx of sodium ions through sodium channels associated with the ACh receptors causes depolarization of the muscle fibre (end plate potential), which creates an action potential within the muscle fiber

Question 15

What do T tubules do?

Answer 15

Following depolarisation of the sarcolemma, the AP travels to the interior of the MF through T tubules

Question 16

The action potential then triggers the release of calcium ions from its storage in the ________.

Answer 16

Sarcoplasmic reticulum

Question 17

The calcium ions diffuse out of the sarcoplasmic reticulum and into the_____

Answer 17

Sarcoplasm

Question 18

What initiates contraction of the muscle fibre by its sarcomeres?

Answer 18

The arrival of calcium into the saroplasm

Question 19

What is the sliding filament theory?

Answer 19

Thick myosin filaments attach and pull on thin actin filaments so they slide over one another. This sliding pulls the Z lines of the sarcomere closer together, thus shortening the sarcomere and an increase in tension in the muscle

Question 20

How does calcium open the binding sites?

Answer 20

Calcium arrives and bonds to troponin, displacing tropomyosin, opening binding sites

Question 21

Phases of a single muscle contraction in response to a single depolarisation (a twitch)

Answer 21

Stimulus
Latent period - 5 milliseconds following stimulus
Contraction phase - muscle fibres begin shortening, lasts about 40ms
Relaxation phase - lasts 50ms

Question 22

What is the motor unit All or None theory

Answer 22

When an AP is initiated in a motor neuron, it causes depolarisation of all the muscle fibres innervated by the motor neurone

Question 23

2 ways in which muscle tension can be graded

Answer 23

1. Number of motor units recruited
2. Frequency of motor unit stimulation

Question 24

For a task requiring great strength, would motor units be stimulated more or less frequently

Answer 24

More

Question 25

What is summation

Answer 25

When successive stimuli are provided before relaxation phase of first twitch has completed, subsequent twitches combine with the first to produce a sustained contraction
This generates a greater amount of tension than single contraction would produce individually

Question 26

What is tetanus

Answer 26

As frequency of stimuli increase, the resultant summation increases
accordingly producing increasingly greater total muscle tension
* This is true up to a point, once the muscle is receiving impulses at a rate that
it cannot relax, it reaches a state of continuous contraction (tetanus)

Question 27

3 axes of roation and the plane of movement that works around this axis

Answer 27

Mediolateral axis (sagittal)
Anteroposterior axis (frontal)
Vertical/longitudinal axis (transverse)

Question 28

What is internal rotation

Answer 28

The anterior surface of the moving segment rotates medially