Nervous Coordination And Muscles Flashcards
What are the parts of a motor neurone?
Cell body, dendrons, axon, Schwann cells, myelin sheath and nodes of ranvier
What are Schwann cells?
It protects the axon and carries out phagocytosis
What’s a myelin sheath?
Covers the axon and is made up of the membranes of Schwann cells
What are nodes of ranvier?
Constructions between adjacent Schwann cells where there is no myelin sheath
What are sensory neurones?
Transmit nerve impulses from a receptor to an intermediate or motor neurone
What are motor neurones?
Transmit nerve impulses from an intermediate relay neurone to an effector (gland/ muscle)
What are intermediate/relay neurones?
Transmit impulses between neurones
What happens at resting potential?
3 Na+ are actively transported out of the axon whilst 2 K+ are transported in by the sodium potassium pump. Na+ is more positive than K+ causing more Na+ to be in the tissue fluid than in the cytoplasm. Na+ naturally diffuse back in whilst K+ move out
How do you reach action potential?
K+ channels open Na+ channel closed they then open causing Na+ to enter the axon more channels open so more Na+ enters. If this reaches +40mv an action potential has been met
How do you depolarise an axon?
After action potential has been met Na+ ion channels close and K+ channels are open. This causes K* to leave the axon. This causes the axon to be more negative than usual (hyperpolarisation). K+ then leaves the axon causing it to reach resting potential -65mv and repolarise
When can action potentials occur along myelinated axons?
Action potentials can only occur where there is no myelin insulin (nodes of ranvier)
What factors affect the speed of action potentials?
How often there are gaps in the myelin sheath
The diameter of the axon
Temperature
What’s the point in a refractory period?
Ensures action potentials are propagated in one direction only
Produces discrete impulses
Limits the number of action potentials
What’s spatial summation?
A number of different presynaptic neurones together release enough neurotransmitter to exceed threshold of the post synaptic neurone
What’s temporal summation?
A single presynaptic neurone releases neurotransmitter many times over a short period of time. If it exceeds threshold of the postsynaptic neurone an action potential will be triggered
What is hyperpolarisation?
Presynaptic neurone releases a neurotransmitter that attaches to Cl- channels on postsynaptic to open them so Cl- moves in whilst K+ moves out. This makes the postsynaptic neurone negative becoming less likely to create an action potential
What happens in a transmission across a synapse?
Ca2+ attach to receptors on outside is presynaptic neurone causing it to enter. This causes the vesicles to move and fuse with the membrane releasing acetylcholine. This diffuses along the synaptic cleft and bind with receptors of Na+ ion channels on the postsynaptic neurone. Na+ enters generating an action potential
What’s the I band?
Only actin
What’s the A band
Actin and myosin
What’s the h zone?
Myosin only
What are slow twitch fibres?
Less powerful contractions but over a long period of time best used for marathons. Aerobic respiration
What are fast twitch fibres?
They contract more rapidly and produce more powerful contractions but only for a short period of time. Anaerobic respiration
What changes when a muscle contracts?
The I band becomes narrower
The z lines are closer together
The h zone bee comes narrower
What is myosin and actin made of?
Fibrous protein tail and globular protein head for myosin
Globular protein for actin
