motor unit Flashcards
What is a motor neuron
a nerve cell which CONDUCTS a NERVE to a group of MUSCLE FIBRES
What is a motor unit
Group of muscle fibres controlled by 1 motor neuron
Function of a motor unit
carry nerve impulses from the brain and spinal cord to the muscle fibres, initiating muscular contraction
What is the action potential
positive electrical charge inside the nerve and muscle cells
which
conducts the nerve impulse down the neuron and into the muscle fibre
What is the neurotransmitter
a chemical (acetylcholine) produced and secreted by a neuron
which transmits the nerve impulse across the synaptic cleft
to the muscle fibre
What is the all or none law
depending on whether the stimulus is above a threshold, all muscle fibres will give a complete contraction or no contraction at all
What is the flow chart of how motor units cause muscular contraction
Fill in the blank
A motor unit is made up of the motor …….. and the muscle fibres it stimulates
neuron
Fill in the blank
A nerve impulse is conducted down the axon to the synaptic cleft by an ………… ……….
electrical charge
Fill in the blank
A ………….. called acetylcholine assist the nerve impulse across the gap into the ……… fibre
neurotransmitter
muscle
Fill in the gap
If the electrical charge reaches a ……… value, the muscle fibre will contract in an … or …… fashion
threshold
all or none
Extend your knowledge
What is the electrical charge inside of the axon and its outside surroundings?
and when there’s a sudden change in voltage what diffuses into the axon?
There is an electrical difference between the inside of the axon (negative)
and its outside surroundings (positive) termed resting potential.
When the nerve is activated, there is a sudden change in voltage as sodium ions (Na+) diffuse into the axon
This triggers a wave of action potential that travels from the cell body down the axon to the synapse
State the parts of a motor unit
Dendrites
Axon
Muscle fibre
Neuromuscular junction
How can skeletal muscle contract
It can only contract if it is stimulated by an electrical impulse sent from the cenrtal nervous system
How can we vary strength of muscle contraction
Recruit the correct number of motor units for the action being completed
recruit the correct size of the motor units for the action being completed
What are slow oxidative muscle fibres
Structurally designed to store oxygen in myoglobin and process oxyegn in the mitochondria which allows athletes to work aerobically
produce a small force, but resist fatigue for a long period of time
predominately used by endurance athletes such as marathoners
red in colour
Describe the fast oxidative glycolytic muscle fibres
Structurally designed to produce a large amount of force quickly
can resist fatigue, but not for as long as type 1 muscle fibres
moderate levels of myoglobin and capillaries
red/pink in colour
predominantly used by high-intensity athletes, such as 800m runners
Describe the fast glycolytic muscle fibres
structurally designed to work anaerobically and have a large store of phosphocreatine
fatigue very quickly
white in colour
low levels of myoglobin and capilaries
produce very high concentrations
predominantly used by short duration and high intensity athletes such as 100m runners
What are the muscle fibre recovery rates?
type 1- 1:1 or 1:0.5 (slow oxidative)
type 2 and 2b - 1:3+ (fast glycolytic)
Why is there a difference in recovery rates from type 1 to type 2a/b fibres
type 1 muscle fibres are not damaged,
whereas type 2a and 2b muscle fibres are damaged and worked to exhaustion so they need more time to fully recover (min 48 hours)
Which type of contraction is likely to cause most damage
eccentic
Relate the exercise intensity to the muscle fibres
low intensity- slow oxidative
higher intensity- fast oxidative glycolytic
high intensity- fast glycolytic recruited alongside all other fibre types
What is the first stage in the motor unit flow chart
nerve impulse initiated in the motor neuron cell body
What is the second stage in the motor unit flow chart
NI conducted down the axon of the motor neuron by a
nerve action potential to the synamotic cleft
What is the third stage of the motor unit flow chart
Neurotransmitter called acetylcholine is secreted into the synaptic cleft to conduct the nerve impulse across the gap
what is the fourth stage of the motor unit flow chart
if the electrical charge is above a threshold the muscle fibre will contract
