skeletal muscle

Question 1

what are the motoneurones of the spinal cord called

Answer 1

alpha-motoneurones

Question 2

where are the cells bodies of alpha motoneurones found?

Answer 2

ventral horn

Question 3

what is a motor unit

Answer 3

single alpha motoneurone and all the muscle fibre it innervates

Question 4

what is focal innervation

Answer 4

each muscle fibre is innervated by one alpha motoneurone

Question 5

what NT is used at a neuromuscular junction

Answer 5

ACh

Question 6

what type of receptor does ACh bind to at NMJ

Answer 6

nicotinic

Question 7

what are end plate potentials

Answer 7

the depolarisation of the muscle membrane at the NMJ

Question 8

how is smooth contraction achieved

Answer 8

each alpha motoneurone innervates muscle fibres that are spread throughout muscles and they fire asynchronously

Question 9

how are muscle contractions made to be precise

Answer 9

the innervation ratio is inversely correlated w contractile precision

Question 10

what is the innervation ratio

Answer 10

number of muscle fibres each alpha neurone activates, low is for more fine control

Question 11

characteristics of type I muscle fibres

Answer 11

1. slow twitch
2. low contractile force
3. high resistance to fatigue
4. energy from oxidative phos
5. red
6. for posture

Question 12

characteristics of type II

Answer 12

1. fast twitch
2. high contractile force
3. low resistance to fatigue
4. glycolytic source of energy
5. white
6. for rapid movement

Question 13

how can we increase force of contaction

Answer 13

1. recruit more alpha motoneurones
2. increase AP firing rate of each alpha motoneurone -> leads to summation of contractions

Question 14

what is tetanus

Answer 14

maximum summation, leads to paralysis

Question 15

what are renshaw cells

Answer 15

inhibitory interneurones, use glycine as NT

Question 16

where are renshaw cells found

Answer 16

spinal cord

Question 17

what do renshaw cells do and how

Answer 17

inhibit APs going to muscle by lateral inhibition

Question 18

what are gamma motoneurones

Answer 18

motoneurones that innervate muscle spindles

Question 19

what are the 2 parts that make up a muscle fibre

Answer 19

extrafusal fibre, intrafusal fibre

Question 20

what part of the muscle fibre causes contraction and interacts w alpha motoneurones

Answer 20

extrafusal fibre

Question 21

what does the gamma motoneurone innervate

Answer 21

intrafusal fibre

Question 22

what are the 3 types of intrafusal muscle

Answer 22

1. Dynamic nuclear bag fiber
2. static nuclear bag fiber
3. nuclear chain fiber

Question 23

what types of intrafusal muscle are innervated by group Ia afferent fibres

Answer 23

all of them

Question 24

what info do group Ia fibres relay about intrafusal muscle

Answer 24

change in stretch and absolute stretch

Question 25

what information do the group II afferent fibres relay about intrafusal muscles

Answer 25

absolute stretch

Question 26

what does the gamma loop do

Answer 26

monitors muscle contraction and corrects it if required

Question 27

where are the golgi tendon organs found and what do they do

Answer 27

between the muscle and bone, they detect force of contraction in skeletal musc and protest the muscle from overloading (stops contraction)

Question 28

what innervates golgi tendon organs

Answer 28

Ib sensory neurones

Question 29

how does the golgi tendon reflex work

Answer 29

Ib sensory neurones activated, glycine released and alpha motoneurone inhibited so muscle cannot contract more