Muscle 2

Question 1

The neuromuscular junction

Answer 1

• The point of contact where your nervous system controls your muscles

Question 2

how many neuromuscular junctions do each muscle fibre have

Answer 2

exactly 1

○ Controlled by firing of one neuron

Question 3

Where do motor neurons come from

Answer 3

out of spinal cord

Question 4

upper motor neurone

Answer 4

goes from brain to cord

Question 5

lower motor nuerone

Answer 5

goes from cord to muscle

Question 6

spinal reflexes

Answer 6

• Circuit bypasses higher centres - short circuits

Question 7

polysynaptic

Answer 7

○ Can be polysynaptic
§ Involving extra modulatory neurons in the circuit
○ Causing relaxation of antagonist muscle

Question 8

Muscle spindles

Answer 8

• Encapsulated intrafusal fibres within the muscle belly

- Monitor change in muscle length and rate of change in muscle length

Question 9

muscle spindles are both

Answer 9

○ Static - sense constant tesion on muscle

○ Dynamic - sense when muscle is stretched

Question 10

muscle spindle sensory and motor aspects

Answer 10

sensory in the middle and started contractile muscle parts toward the ends

Question 11

contractile ends of muscle spindles

Answer 11

§ Shorten with muscle to maintain sensitivity in shortened muscles - activated by stretch tension

Question 12

motor nuerones telling contractile ends to muscle spindles what to do

Answer 12

gamma-MNs
§ Slower
§ so they are not hyperactive when muscle is actively shortening

Question 13

myotactic reflex also called

Answer 13

catch reflex

Question 14

myotactic reflect mediated by

Answer 14

muscle spindle

Question 15

muscle spindle sensory neurone synapses with

Answer 15

alpha motor neurone

Question 16

Golgi tendon organs

Answer 16

• Encapsulated receptors
  
  • In myotendinous junction
  • Monitor tendon tension
• don’t have a motor aspect because they don’t have to stretch

Question 17

golgi tendon organs monitor

Answer 17

tension that may be
○ Static - slow adapting and low intensity
○ Dynamic - rapid adapt, intense

Question 18

inverse myotactic reflex also called

Answer 18

drop reflex

Question 19

inverse myotactic reflex mediated by

Answer 19

Golgi tendon organs

Question 20

• Inverse myotactic reflex

Answer 20

○ Sensory neuron synapses with an inhibitory interneuron
○ Inhibit aMN firing, relaxes muscle
○ Negative feedback prevents damage
○ A drop reflex

Question 21

Contracting a flexor muscle, requires

Answer 21

relaxation of its associated extensor muscle

Question 22

Excitatory neuron synapses with

Answer 22

synergist (agonist) muscle

Question 23

Inhibitory interneuron synapse at

Answer 23

antagonist muscle

Question 24

motor unit

Answer 24

§ Single motor neuron and the multiple muscle fibres that it innervates

Question 25

More myofibres =

Answer 25

greater force

Question 26

More motor units =

Answer 26

greater dexterity (fine coordination) 
			§ Take up more space in the brain

Question 27

3 types of motor units

Answer 27

○ Type 1 - slow contracting, fatigue resistant
○ Type 2a - fast contracting, fatigue resistant
○ Type 2b - fast contracting, fast fatigue \

Question 28

Type 1

Answer 28

slow contracting, fatigue resistant

Question 29

Type 2a

Answer 29

fast contracting, fatigue resistant

Question 30

Type 2b

Answer 30

fast contracting, fast fatigue \

Question 31

• Slow motor units

Answer 31

○ Small forces, fatigue resistant

○ Continuous activity

Question 32

• Fast motor units

Answer 32

○ Fatigable
○ High forces, fatigue quickly
○ Small bursts of explosive activity

Question 33

which motor units recruited first

Answer 33

• Small slow Mus are recruited first

Question 34

• Henneman’s size principle

Answer 34

Slow motor neurons have lower threshold for synaptic activation