Neurones, muscles etc Flashcards
What is a neurone?
Specialised animal cell that passes on nerve impulses
What is the myelin sheath formed from?
Schwann cells
What are the gaps in the myelin sheath called?
Nodes of Ranvier
What is a synapse?
A junction that transfers an electrical impulse between two neurones, or a neurone an a muscle fibre
Within the presynaptic neurone, neurotransmitter molecules are transported in…
Synaptic vesicles
What does the presynaptic neurone contain a large number of?
Mitochondria
Synapses are unidirectional, what does this mean?
Synapses can only pass information in one direction across a synapse, from the presynaptic neurone to the postsynaptic neurone.
What is spatial summation?
Multiple different presynaptic neurones release enough neurotransmitters at once to exceed the threshold potential and trigger an action potential.
What is temporal summation?
A single presynaptic neurone releases neurotransmitters many times over a very short period to exceed the threshold potential and trigger an action potential.
Where is the Pacinian corpuscle located?
Deep under an animal’s skin
What is the Pacinian corpuscle made out of?
Tissue layers, and the sensory neurone
What does the Pacinian corpuscle respond to?
Mechanical pressure
There are ion channels in the membrane of the Pacinian corpuscle’s sensory neurone.
Describe how these facilitate an action potential being sent to the central nervous system.
First, the membrane of the sensory neurone contains stretch-mediated sodium ion channels.
When the Pacinian corpuscle experiences pressure, these ion channels open.
An influx of sodium ions cause the inside of the neurone to become depolarised. This is called a generator potential.
When many of these potentials build up, the threshold value is reached, triggering an action potential. This action potential is sent to the central nervous system.
