What is the structure of a myelinated motor neurone?
A myelinated motor neurone consists of a cell body, dendrites, axon, myelin sheath, Schwann cells, and nodes of Ranvier.
How is a resting potential established across the neurone membrane?
The resting potential is maintained by the sodium-potassium pump, which actively pumps 3 Na⁺ out and 2 K⁺ in, creating a negative charge inside the neurone.
What role do sodium and potassium ions play in maintaining the resting potential?
The membrane is more permeable to K⁺ ions, which diffuse out, while Na⁺ ions are kept out, maintaining a polarised state.
How do changes in membrane permeability lead to depolarisation?
Depolarisation occurs when voltage-gated Na⁺ channels open, allowing Na⁺ to enter, making the inside more positive.
What is the all-or-nothing principle in action potentials?
The all-or-nothing principle states that an action potential only occurs if the threshold potential is reached; otherwise, no response occurs.
How does an action potential travel along a non-myelinated axon?
In non-myelinated axons, action potentials are transmitted continuously along the axon in a wave-like manner.
What is the role of the refractory period in action potential transmission?
In myelinated axons, action potentials jump between nodes of Ranvier in saltatory conduction, increasing speed.
How does an action potential travel along a myelinated axon, and what is saltatory conduction?
The refractory period prevents another action potential from occurring immediately after one has passed.
How does the refractory period ensure discrete impulses and limit impulse
frequency?
The refractory period ensures discrete impulses and limits the maximum frequency of impulses.
How does myelination affect the speed of conductance?
Myelination increases conduction speed as impulses jump between nodes of Ranvier (saltatory conduction).
How does axon diameter affect the speed of conductance?
Larger axon diameters reduce resistance to ion movement, increasing impulse speed.
How does temperature affect the speed of conductance?
Higher temperatures increase diffusion rates of ions, speeding up conduction, but too high a temperature can denature proteins.
What is the structure of a synapse?
A synapse consists of a presynaptic neurone, synaptic cleft, and postsynaptic neurone with neurotransmitter receptors.
What is the structure of a neuromuscular junction?
A neuromuscular junction is a specialised synapse between a motor neurone and a muscle fibre.
What are the steps involved in synaptic transmission across a cholinergic synapse?
Synaptic transmission steps: Action potential arrives, Ca²⁺ channels open, vesicles release neurotransmitter, neurotransmitter binds to receptors, Na⁺ channels open, new action potential is generated.
What is meant by unidirectionality in synaptic transmission?
Unidirectionality means synapses ensure signals travel in one direction (from pre- to postsynaptic neurone).
What is temporal summation, and how does it affect synaptic transmission?
Temporal summation: Multiple impulses from one neurone quickly add up to trigger an action potential.
What is spatial summation, and how does it affect synaptic transmission?
Spatial summation: Multiple neurones release neurotransmitter at the same time, increasing the chance of reaching the threshold.
How do inhibitory synapses prevent the generation of an action potential?
Inhibitory synapses open Cl⁻ channels, making the inside more negative
(hyperpolarised) and preventing action potentials.
How does transmission across a cholinergic synapse compare to transmission across a neuromuscular junction?
Cholinergic synapses transmit impulses between neurones, while neuromuscular junctions transmit impulses to muscle fibres, always triggering contraction.
How can drugs affect synaptic transmission?
Drugs can mimic, block, or enhance neurotransmitter effects, altering synaptic transmission.
How can information about synapses be used to predict the effects of drugs on nervous coordination?
Information on synapses and neurotransmitters can help predict drug effects, such as increasing or decreasing nerve impulse transmission.
