Nervous systems Flashcards
What is a nerve impulse
Self propagating wave of electrical disturbance travelling along surface of axon membrane
What is resting potential
Potential difference across he axon when a neuron is at rest
What are the charges of inside and outside of an axon
Inside is negatively charged relative to outside
What is an axon
The long fibre in a neurone tat conducts impulses away from the cell body
What is the purpose of the myelin sheath
Made of schwaan cells that insulates the axon, shields the axon from surrounding tissue fluid and insulates it from other neurones
What is depolarisation
A rapid temporary reversal of the resting membrane potential
What is re polarisation
A return to the resting membrane potential
How is resting potential maintained?
Membrane more permeable to potassium ions and less to sodium ions
Sodium ions are actively transported out and potassium ions pumped in
How does MS lead to slower responses to stimuli?
Myelin sheath broken down
Impulse is unable to jump from node to node
More depolarisation over length of membrane
How does a lower temperature lead to slower nerve impulse conduction?
Ions have less kenetic energy and therefore they diffuse more slowly
What factors affect speed of nerve impulse conduction
Myelination
Diameter of axon
Temperature
What is the absolute refractory period?
After generation of an action potential
Voltage gated sodium channels are inactivated
They cannot respond to further stimulus
What is a synapse?
Junction between neurones
Where are neurotransmitters made and where are they stored?
Made in pre synaptic neurones
Stored in synaptic vesicles
What is summation?
Arrival of multiple action potentials leading to a build up of neurotransmitter
Why does depolarisation happen?
Sodium ion gates open
Why can another action potential not be generated once one has just been generated?
Membrane more impermeable to sodium ions
Sodium ion cannot enter axon
Membrane becomes more negative than resting potential
Explain why a neurotransmitter (e.g. acetylcholine) can only bind with one type of receptor protein in the postsynaptic membrane.
Unique shape of receptor protein / binding site Due to (tertiary) structure of protein molecule
What is the role of calcium ions (Ca2+) in synaptic transmission?
Cause vesicles to move to presynaptic membrane
How is an action potential generated?
Sodium ion channels open;
Allowing rapid influx of sodium ions