Motor system 1

Question 1

Key points of the sensorimotor system

Answer 1

Primary motor cortex: higher level command- what makes you do a thing

Question 2

Basal ganglia

Answer 2

• group of structures.

- making decisions

Question 3

Cerebellum

Answer 3

• fine regulation of motor command

Question 4

Key points of the sensorimotor system

Answer 4

1. ) Motor control is governed by lower and upper motor neurons
2. ) The lower motor neurons begins (has cell body) in brainstem/spinal cord and projects to the muscle
3. ) Upper motor neurons originate in higher centres and project down to meet the lower motor neurons

Question 5

How much weight does muscle make up

Answer 5

40%

Question 6

Smallest muscle I body

Answer 6

The stapedius (ear)

Question 7

Biggest muscle in body

Answer 7

Gluteus maximus

Question 8

Strongest

Answer 8

Masseter

Question 9

Key facts about muscles

Answer 9

• They can only contract or relax

Question 10

How do we achieve a range of movements?

Answer 10

1. ) Antagonistic arrangement

2. ) Recruitment of muscle fibres: fast/slow twitch/small or large motor units

Question 11

What is a motor unit?

Answer 11

It is a single alpha motor neuron and all the muscle fibres it innervates

Question 12

Features of motor units

Answer 12

• fewer fibres = greater movement resolution = those innervating finger tips
• It is the final common pathway for motor control
• activation of an alpha motor neuron depolarises + causes contraction of all fibres in that unit

Question 13

Define the motor pool

Answer 13

This is all the lower motor neurons that innervate single muscle
The muscle pool contains alpha + gamma motor neurons
Arranged in a rod like shape in the ventral horn of the S.C

Question 14

What are cell bodies in the ventral horn activated by

Answer 14

1. ) Sensory info from muscle

2. ) Descending info from brain

Question 15

Sensing in muscle

Answer 15

CNS needs to know:

1. ) How much tension is on the muscle
2. ) What is the length (stretch) of the muscle

Question 16

What senses tensiom

Answer 16

Golgi tendon organ

Question 17

What senses stretch

Answer 17

Muscle spindles

Question 18

Golgi tendon organs

Answer 18

• within the tendon (where muscle joins bone)

- it sends ascending sensory info to the brain via S/C about how much force there is in the muscle

Question 19

Muscle spindiles

Answer 19

• Sense length of muscle and forms a key part of reflex circuit

Question 20

Features of intrafusal fibres

Answer 20

• are innervated separately by gamma motor neurons

- they are set at a length that optimises muscle stretch detection

Question 21

Features of muscle spindles

Answer 21

• embedded within most muscle

- composed of intrafusal fibres

Question 22

Withdrawl reflex

Answer 22

• Say you step on a pin
• you need a reflex so you withdraw your leg but also put weight on your other leg so you don’t fall over
• this is reciprocal innervation

Question 23

The vestibular righting reflex

Answer 23

• detects the body is not upright as well as any acceleration due to gravity

Question 24

Control of muscle force: size principle

Answer 24

• units are recruited in order of size (smallest first)

- fine control required at lower forces

Question 25

Control of muscle force: muscle fibre types

Answer 25

1. ) Slow
2. ) Fast fatigue resistant
3. ) Fast fatigue