PROPERTIES OF THE MOTOR UNIT

Question 1

What is the motor unit?

Answer 1

An alpha (lower) motor neurone and all the extrafusal muscle fibres it supplies as well as the NMJ

Question 2

What part of the nervous system contains motor units

Answer 2

Somatic - they are somatic efferents

Question 3

What is muscle tone, what does it do and how is it regulated?

Answer 3

• The amount of tension or resistance to movement in the muscles
• Changes in muscle tone affect the way voluntary movements are created
• Muscle tone is regulated by signals that travel to the brain from nerves which tell the muscle to contract

Question 4

What is the difference between striated and non striated muscle

Answer 4

Striated muscle - attached to tendons and ligaments and involved in voluntary muscle movement (skeletal and cardiac muscle)

Non - striated muscle - mostly are situated in the lining of inner organs and show involuntary movement (smooth muscle)

Question 5

Importance of skeletal muscle (3)

Answer 5

• Muscle tone - posture
• Stability of joints
• movements

Question 6

What is a myocyte

Answer 6

A muscle cell in cardiac or smooth muscle

Question 7

What is a muscle cell in skeletal muscle called?

Answer 7

muscle fiber

Question 8

What is a fascicle formed from?

Answer 8

A collection of myocytes

Question 9

What are myocytes made from?

Answer 9

Lots myofibrils

Question 10

What do a bunch of fascicli form?

Answer 10

Muscles

Question 11

What is the name of the connective tissue that ensheathes the myocyte

Answer 11

Endomysium

Question 12

What is the name of the sheath enveloping the fascicle?

Answer 12

Perimysium

Question 13

Name of the sheath enveloping all fascicles in a muscle and the neuromuscular bundle.

Answer 13

Epimysium

Question 14

What is a tendon?

Answer 14

Fibrous connective tissue that connects muscle to bone. It brings the actions of individual myofibrils together so that the myocytes produce combined actions

Question 15

What are the two types of motor neurones?

Answer 15

• Upper motor neurone
• Lower motor neurone

Lower motor neurones are driven by upper motor neurones

Question 16

Where are motor neurones in the spinal cord found?

Answer 16

Grey matter

Question 17

Where are lower motor neurones found?

Answer 17

Cell body in a cranial nerve motor nucleus or the ventral horn of the spinal cord

Question 18

Give the 3 categories of muscle fibres

Answer 18

Type FF = Fast twitch - fast and easily fatigued
Type FR = intermediate twitch - fast and resistant to fatigue
Type S = Slow twitch

Question 19

What action is taken by muscles when there is nerve damage?

Answer 19

The muscle cells are persuaded to take up another nerve supply because without it the muscle could die. The characteristic of the nerve influences the muscle