motor units and muscle fibres

Question 1

what is a motor neurone

Answer 1

a nerve cell that conducts a nerve impulse to a group of muscle fibers

Question 2

what is a motor unit

Answer 2

A motor neuron and the muscle fibres stimulated by its axon

Question 3

what is a neurotransmitter

Answer 3

a chemical produced and secreted by a neuron which transmits the nerve impulse across the synaptic cleft to the muscle fiber

Question 4

what is the neurotransmitter in motor units called?

Answer 4

acetylcholine

Question 5

what is the all or none law

Answer 5

the neuron either fires at full strength or it does not fire at all

Question 6

what does muscle contraction depend on

Answer 6

-number of motor units recruited
-the frequency of which the impulse arrives

Question 7

what is a neuromuscular junction

Answer 7

where an axon terminal meets at muscle fibre

Question 8

what is a synaptic cleft

Answer 8

a gap across which acetylcholine is secreted after an electrical impulse has reached the motor endplate and stimulated the vesicle to release it.

Question 9

function of dendrites

Answer 9

receive incoming signals from other neurons

Question 10

function of nodes of ranvier

Answer 10

allow an action potential to propagate quickly down an axon - allows the impulse to jump from node to node

Question 11

function of the myelin sheath

Answer 11

Protect and electrically insulate the axon
Increase speed of nerve impulse transmission

Question 12

what is a neuromuscular system

Answer 12

This is composed of all the motor units, muscles, and nerves that work together.

Question 13

what is the motor end plate

Answer 13

location where an action potential can travel to to stimulate a muscle fibre - specialised synapses at the end of axon branches of a motor neuron

Question 14

How does an eletrical impulse stimulate a muscle cell?

Answer 14

1. dendrites of the motor neuron recieve impulses from other neurones + pass them on to the cell body where a nerve impulse is then initiated
2. the nerve impulse is conducted down the axon of the motor neuron by a nerve action potential to the synaptic cleft
3. the neurotransmitter (acetylcholine) is secreted into the synaptic cleft to conduct the nerve impulse across the gap
4. if the electrical charge is above a threshold, the muscle fibre will contract
5. this happens on an ‘all or none’ basis

Question 15

what is the protein that carries the oxygen from the blood to the haemoglobin

Answer 15

myoglobin

Question 16

what are structural characteristics of slow oxidative muscle fibres

Answer 16

-many mitochondria
-high capillary density
-high myoglobin content

Question 17

what are structural characteristics of fast glycolytic muscle fibres

Answer 17

-large neurone size
-large amount of fibres per neurone
-high phosphocreatine store

Question 18

what are structural characteristics of Fast Oxidative Glycolytic Muscle Fibres

Answer 18

-large neurone size
-large fibres per neurone
-high mitochondria density
-high phosphocreatine store

Question 19

what are functional characteristics of slow oxidative muscle fibres

Answer 19

-fatigue resistant
-aerobic respiration
-low force and strength of contraction

Question 20

what are functional characteristics of fast glycolytic muscle fibres

Answer 20

-high strength and force of contraction
-fatigues easily
-high anaerobic capacity

Question 21

what are functional characteristics of Fast Oxidative Glycolytic Muscle Fibres

Answer 21

-moderate strength and force of contraction
-moderate fatigue resistance
-moderate aerobic and anaerobic capacity

Question 22

Sporting example of slow oxidative muscle fibres

Answer 22

Marathon runner

Question 23

Sporting example of fast oxidative glycolytic muscle fibres

Answer 23

800m-1500m runner

Question 24

A sporting example of a fast glycolytic muscle fibre

Answer 24

100m sprinter

Question 25

What does high capillary density mean for an athlete

Answer 25

More O2 can be transported to muscles

Question 26

What does high mitochondria density mean for an athlete

Answer 26

More anaerobic respiration can take place-more energy

Question 27

What does high myoglobin store mean for an athlete

Answer 27

More O2 in muscle to mitochondria

Question 28

What is phosphocreatine

Answer 28

High energy compound that can be broken down without oxygen

Question 29

What happens during the first stage of action potential (polarisation)

Answer 29

Sodium ions are extra cellular and potassium ions are intercellular.
The voltage is -70mvolts which creates an imbalance

Question 30

What happens during the second stage of action potential (depolarisation)

Answer 30

Sodium ions move into intercellular space through sodium gates
The voltage is -55mvolts
This is called the threshold of excitation

Question 31

What happens during the third stage of action potential (repolarisation/hyperpolarisation)

Answer 31

Potassium ions move to extra cellular space through potassium gates
Charge then becomes too negative (-80mvolts)
This means it is hyperpolarised

Question 32

What happens on the fourth stage of action potential (polarisation)

Answer 32

It returns back to resting potential
Potassium ions are in intracellular space and sodium ions are in extra cellular space
-70mvolts

Question 33

What happens when impulses travel through synapses

Answer 33

-calcium ions rush into axon terminals
-acetylcholine (a neuronetransmitter) is released and the impule travels across the synapse

Question 34

What is resting potential

Answer 34

Where there is a lower charge inside the neurone than outside the neurone

Question 35

What is action potential

Answer 35

The electrical impulse carried down the axon