Week 2 Neuro Part 2

Question 1

What type of lower motor neurones innervate the muscle bulk

Answer 1

alpha motor neurones

Question 2

What type of lower motor neurone innervate a muscle spindle

Answer 2

gamma motor neurones

Question 3

where do the axons of lower motor neurons exit the spinal cord

Answer 3

the ventral roots

Question 4

How are motor neurone distrinuted in the spinal cord

Answer 4

they are not distriuted equally - there are higher numbers in the cervical enlargement and lumbar enlargement

Question 5

What is a motor unit

Answer 5

the alpha motor neurone and all of the skeletal muscle fibres it innervates - ies the smallest functional component of the motor system

Question 6

what is the motor neurone pool

Answer 6

the collection of alpha motor neurones that innervates a single muscle

Question 7

How is the force of muscle contraction graded

Answer 7

frequency of action potentials

recruitment of additional synergistic motor units

Question 8

How are lower motor neurones cell bodies distributed in the ventral horn

Answer 8

those innervating axial muscles are more medial, distal muscle are more lateral

those innervating flexors are dorsal, extensors are ventral

Question 9

What ate type one muscle fibres

Answer 9

slow oxidative - slow contraction and relaxation
resist fatigue
red fibres

Question 10

what are type two a fibres

Answer 10

fast contraction an relaxation fatigue resistant

red fibres

Question 11

what are type 2 b fibres

Answer 11

fast contraction but easily fatigued
white fibres
poorly vascularised

Question 12

which skeletal muscle fibres types have high myoglobin and which have low

Answer 12

types 1 and 2a - high

type 2b - low

Question 13

which type of motor unit is most numerous

Answer 13

slow

Question 14

which type of muscle fibres are associated with fast fatiguing motor units

Answer 14

type 2b

Question 15

What type of muscle fibres are associated with fatigue resistant muscle fibres

Answer 15

Type 2a

Question 16

what type of muscle fibre is associated with slow motor units

Answer 16

type 1

Question 17

what type of motor neurone is required for standing

Answer 17

slow - with type 1 muscle fibres - resisting fatigue

Question 18

What type of motor unit is required for walking/jogging

Answer 18

fast fatigue resistant - type 2a muscle fibres

Question 19

What type of motor unit is require for movements such as jumping

Answer 19

fast fatigable - type 2b

Question 20

what does it mean to have a small motor unit

Answer 20

each alpha fibre is only supplying a few muscle fibres - needed for fine movements eg extraocular eye movement

Question 21

what does it mean to have a large motor unit

Answer 21

each alpha motor neurone supplies a large number of muscle fibres

Question 22

What is the myotatic reflex

Answer 22

when a skeletal muscle is stretched in contracts

Question 23

what organ within the muscle senses the change in length

Answer 23

muscle spindle

Question 24

what motor neurons are the efferents for the muscle spindle

Answer 24

gamma motor neurones

Question 25

What neurotransmitter mediates the myotatic reflex

Answer 25

glutamate

Question 26

what is different about mytatic reflexes

Answer 26

it is a monosynaptic reflec arc - synapse occurs in the spinal cord

Question 27

What sensory neurones innervate the spindle fibres and act as the the afferent limb of the reflex arc

Answer 27

Ia sensory neurones

Question 28

How can the intrafusal fibres be subdivided in the muscle spindle

Answer 28

Bag 1 - sensitive to rate of change of muscle length - innervated by dynamic gamma motor neurones bag 2- sensitive to changes in absolute length of muscle fibre - innervated by static gmn chain fibres - sensitive to absolute length - static gamma fibres

Question 29

which afferent fibre is more sensitive to rate of change of muscle lenght

Answer 29

1a

Question 30

Which afferent fibres is more sensitive to changes in absolute length

Answer 30

II

Question 31

Where are Golgi tendons located

Answer 31

at the junction of muscle and tendon

Question 32

what do Golgi tendons do

Answer 32

monitor changes in mucles tension in series with extrafusal fibres they therefore act to regulate muscle tension to protect muscle form overload

Question 33

What sensory afferents innervate Golgi tendons

Answer 33

group Ib

Question 34

what is the inverse myotatic reflex

Answer 34

group Ib afferents form Golgi tendons synpats on inhibitory interneurons which synsaps on alpha motor neurons to relax the muscle polysynaptic (unlike myotatic reflex which is monsynaptic)

Question 35

where are proprioceptive axons present

Answer 35

in connective tissue of joints eg joint capsules and ligaments

Question 36

where does proprioception arise from

Answer 36

muscle spindles Golgi tendon organs joint receptors

Question 37

what is reciprocal inhibition

Answer 37

when the extensor contracts - flexor must relax and vice versa

Question 38

what mediated the recipricol inhibition

Answer 38

inhibitory interneurons

Question 39

what do excitatory interneurons mediate

Answer 39

the flexor reflex | the crossed extensor reflex

Question 40

what is the flexor refelx

Answer 40

contraction of flexors occurs due to noxius stimulus eg pain

Question 41

what is crossed extensor reflex

Answer 41

noxius stimuli causes limb to extend - enhances postural support during withdrawal of foot from pain you do not fall over