3.5.2 - Coordination Flashcards
Myelin sheath definition
Covers the axon and is made up of membranes of the Schwann cells
Do myelinated neurones transmit nerve impulses faster or slower than unmyelinated neurones?
Faster, because myelin sheath acts like an electrical insulator, whereby the action potential is prevented from occurring
Nodes of Ranvier definition
The gaps in an axon, where there is no myelin sheath
Schwann cells definition
They surround the axon, protecting it and providing electrical insinuation. They wrap round the axon many times, so layers of membrane build up around
Sensory neurone function
Transmit nerve impulses from a receptor to a relay neurone. They have a dendron that carries the impulse towards the cell body and an axon that carries it away
Motor neurone function
Transmit nerve impulses from a relay neurone to an effector (E.G. Gland or muscle). They have a long axon and many short dentrites
Dendron definition
Small extensions of the cell body which subdivide into dentrites, that carry nerve impulses towards the cell body
Axon definition
A single long fibre that carries the nerve impulses away from the cell body
Differences between sensory/ motor neurones?
Sensory neurones have the cell body in the middle, motor neurones have it at the end
Sensory neurones take the electrical impulse from the receptors to the CNS, motor take it from the CNS to the effector
Nerve impulse definition
Self-propagating wave of electrical disturbance that travels along the surface of an axon membrane
Resting potential value?
70mV
Resting potential basic description?
Na+ ions actively transported out of axon
K+ ions actively transported in
More Na ions leave than K ions enter = concentration gradient
Na wants to diffuse in, and K out
Na gates are closed so can’t, but K gates are open
K ions diffuse out of axon = potential difference
When reaches an equilibrium, the resting potential is constant
Polarisation of an axon definition?
When the resting potential is achieved
Action potential basic description?
Na gates closed, axon is at resting potential
Energy (from nerve impulse) causes Na gates to open, letting Na diffuse into he axon
When potential = 40mV, Na gates close, K gates open
K ions diffuse out, axon repolarises
Hyper polarisation occurs, K gates close and Na/K pump continues
Reaches resting potential again, the axon repolarises
Unidirectional definition? What is unidirectional?
Synapses, can only travel one way (pre synaptic knob - post synaptic knob)
Neurotransmitter definition?
Neurotransmitter = acetylcholine, is required for transmission across a synapse. Can only be made in the pre synaptic knob.
Acetylcholine definition
One type of neurotransmitter, released by the pre synaptic knob of a neurone. Diffuses across the synapse, to bind with a receptor, passing the nerve impulse to another neurone
Action potential definition
The change that occurs in the electrical charge across the membrane of an axon when it is stimulates and a nerve impulse is passing
Acetylcholinesterase
The enzyme that hydrolysis acetylcholine (the neurotransmitter), making it inactive in the synapse
Dendrite definition
A branched extension of the cell body of a neurone, which conducts electrical impulses towards the cell body
Refractory period definition
Once an action potential has been created, there’s a period after when inward movement of Na ions is prevented because the sodium gates are closed. Impossible to generate an action potential
Repolarisation definition
Return to the resting potential in the axon of the neurone after an action potential
Generator potential definition
Depolarisation of the membrane of a receptor cell as a result of a stimulus
Resting potential definition
The difference in electrical charge maintained across the membrane of the axon of a neurone when not stimulated
