Nervous coordination and muscles Flashcards
What is a neurone?
Specialised cell that generates action potentials to communicate with other neurones or effectors.
What does a motor neurone do?
Transmits impulses from the central nervous system to muscles or glands.
What is the effect of temperature on neurone impulse transmission?
Higher temperature increases diffusion rates and therefore increases speed of transmission,
Describe the features of a neurone in a resting state.
Neurone not transmitting an impulse is polarised, as the inside and outside are oppositely charged; inside of the cell is negatively charged, the potential difference is about -70mV.
List the stages of an action potential.
Resting potential - threshold potential - depolarisation - repolarisation - refractory period.
Describe the neuromuscular junction.
Motor neurones form a neuromuscular junction with each muscle fibre; synpase functions like a cholinergic synapse, but causes muscle fibres to contract.
Which two structural proteins are involved in muscle contraction?
Actin, myosin.
What is the refractory period?
Follows the repolarisation in an action potential, where there in no membrane permeability to sodium and potassium ions and the neurone is unresponsive.
What are the components of a synapse?
Two neurones (presynaptic and postsynpatic); the gap between them - synaptic cleft.
What is the sequence of events involved in transmitting an impulse at a synapse?
- Presynaptic neurone has an action potential at its surface membrane.
- This action potential causes neurotransmitter molecules to be released into synaptic cleft.
- Neurotransmitter molecules bond temporarily with receptors on postsynaptic neurone membrane.
- Molecules cause depolarisation of postsynaptic neurone; if this is above the threshold, impulse will be sent.
In a cholinergic synapse, what happens to acetylcholine when it is released from the synaptic knob and what is the impact of this?
Diffuses across the cleft and binds to receptors on the postsynaptic membrane, delaying the impulse by about 0.5ms.
In a cholinergic synapse, what determines whether the impulse is triggered in the postsynaptic neurone?
It has to reach the threshold potential.
What happens to acetylcholine after it has bound to its receptor?
Acetylcholinesterase on postsynaptic membrane hydrolyses ACh; breakdown product choline is reabsorbed into synaptic knob.
Nervous system.
Communication is by nerve impulses.
Transmission via neurons and are very rapid.
Nerve impulses travel to specific parts of the body.
Localised, rapid, short-lived response.
Usually temporary and reversible effect.
Nerve impulses.
Electrical signals that pass along nerve cells are known as neurons.
Axon.
A long fibre possessed by neurons.
Insulated by a fatty sheath with small uninsulated sections along its length (called nodes of Ranvier).
Myelin sheath.
A substance made by specialised cells known as Schwann cells.
Myelin is made when Schwann cells wrap themselves around the axon along its length.
Presence of Schwann cells.
The electrical impulse does not travel down the whole axon but jumps from one node to the next.
Saltatory conduction.
‘jumping’ of the electrical impulse between nodes of Ranvier; speeds up the conduction of the impulse and its transfer from one cell to another.
Dendrites.
Extensions from neurons’ cell bodies.
They can connect to many other neurones and receive impulses from them, forming a network for easy communication.
3 types of neurons.
Sensory, relay, motor.
Sensory neurons.
Carry impulses from receptors to the CNS (brain or spinal cord).
Relay neurons.
Found entirely within the CNS and connect sensory and motor neurons.
