neuromuscular system

Question 1

What is a motor neurone ?

Answer 1

specialised cells transmit nerve impulses to a group of muscle fibres

Question 2

What is a motor unit ?

Answer 2

A motor neurone and the muscle fibres stimulated by it’s axon

Question 3

What are the 5 steps that take place for a muscle contraction to occur ?

Answer 3

1. impulse sent by the cell body in the cerebellum
2. Impulse (action potential) sent down the motor neurone through the motor end plates into the synaptic cleft
3. nerve transmitter called acetylcholine is secreted into the synaptic cleft to transmit nerve impulses across the gap
4. if the charge is above the threshold, muscle fibre contracts
5. Happens in an all or nothing fashion

Question 4

What is acetylcholine ?

Answer 4

• the neurotransmitter that helps nerve impulse travel across the synaptic cleft

Question 5

What does motor mean ?

Answer 5

movement

Question 6

How can we vary the strength of a muscle contraction ?

Answer 6

• correct number of motor units
• correct size of motor units

Question 7

What is the sympathetic nervous system ?

Answer 7

• speeds things up for exercise (e.g heart rate)

Question 8

What is the parasympathetic nervous system ?

Answer 8

• slows things down to resting state
• relaxes

Question 9

What is the all-or-none law ?

Answer 9

Where a sequence of impulses has to be sufficient intensity to stimulate all of the music fibres in a motor unit in order for them to contract.
If not none of them would contract

Question 10

What are the 3 types of muscle ?

Answer 10

• skeletal muscles
• smooth muscles
• cardiac muscles

Question 11

What are the 3 types of fibres ?

Answer 11

• slow twitch (type 1) = slow oxidative
• fast twitch (type 2a) = fast oxidative glycolytic
• fast twitch ( type 2b) = fast glycolytic

Question 12

What are the characteristics of type 1 fibres (slow twitch) ?

Answer 12

• few fibres, small size
• low force produced
• slow contraction speed
• red in colour
• high myoglobin
• high mitochondria
• low resistance to force

Question 13

What are the characteristics of type 2 fibres (fast twitch type 2a) ?

Answer 13

• many fibres, large fibres
• high force
• fast contraction speed
• pink in colour
• moderate myoglobin
• moderate mitochondria
• moderate resistance to fatigue

Question 14

What are the characteristics of type 2x fibres (fast twitch type 2b) ?

Answer 14

• many fibres, large fibres
• high force
• very fast contraction
• white colour
• low myoglobin
• low mitochondria
• low resistance to fatigue

Question 15

What is wave summation ?

Answer 15

Where there is repeated nerve impulse with no time to relax
A smooth, sustained contraction occurs rather than twitches

Question 16

What is tetanic contraction ?

Answer 16

A sustained muscle contractions caused by a series of fast repeating stimuli

Question 17

What is spatial summation ?

Answer 17

When the strength of a contraction changes by altering the number and size of the muscles motor units

Question 18

What are factors affecting flexibility ?

Answer 18

• bony features of a joint
• elasticity
• gender differences
• age
• body composition

Question 19

What is isometric ?

Answer 19

• a muscle contraction with no movement and no length change

Question 20

What are the two types of isotonic contractions

Answer 20

• concentric
• eccentric

Question 21

What do isotonic contractiosn involve ?

Answer 21

The high repetition of movements against a low resistance such as running and swimming
Concentric = shortening
Eccentric = lengthening

Question 22

What are the steps in PNF ?

Answer 22

• contract
• relax
• antagonist
• contract

Question 23

What is the stretch reflex action ?

Answer 23

• produced by proprioceptors such as muscle spinales
• stretch reflex causes muscle fibres to contract
• the basis of muscle tore and protects the muscle againstW

Question 24

What is the difference between strain and sprains ?

Answer 24

strain = t = tear = muscle
sprain = tendon = ligament