Principles of Neuroscience Lecture 2 Function of the Nervous System Flashcards
Describe the way action potentials in neurons work
Resting state: the neuron is polarised
Threshold: if depolarisation at the axon hillock surpasses the threshold, an action potential will fire. At this point, voltage gated sodium channels open, and sodium rushes into the neuron (down its concentration gradient), depolarising the cell
Depolarisation: once the cell is depolarised, the voltage gated sodium channels shut, and the cells slowly returns to a hyperpolarised state.
This action potential moves down an axon like a Mexican wave
What experiments did Galvani do?
He delivered charge from a scalpel onto a nerve and observed muscle contraction.
What is saltatory conduction?
This is the quickening of impulse conduction by myelination of the axon, so that only small regions of the axon are exposed (node of ranvier)
Differentiate between the two types of cell that produce myelin sheaths
Schwann cells: PNS
Oligodendrocytes: CNS
What are the two possible types of synapse?
Chemical and electrical
Describe electrical synapses.
When/where do they occur?
Electrical synapses are very rare.
In this case, the depolarisation does not stop at the axon terminal, but instead ions pass through to the post-synaptic vesicle via tit junctions.
This is very quick compared to chemical synapses.
These occur in the intercostal muscles where coordination is important
Describe chemical synapses.
Chemical synapses make up the vast majority of synapses
Depolarisation of a neuron leads to fusion of a synaptic vesicle, releasing neurotransmitters into the synaptic cleft.
These molecules then interact with receptors on the post-synaptic neuron, causing a response (firing of this neuron)
What did Loewi discover?
Vagusstoff
A heart that is removed from the body, but still has the vagus nerve connected was placed in a solution.
The nerve was stimulated, and neurotransmitters from this parasympathetic nerve caused the slowing of heart pumping.
This solution was then put with another heart, and this heart showed the same slowing of pump rate
Briefly describe some features of neurotransmitter synthesis
This is an extremely energy intense process, and is part of the reason that the brain has such a high energy demand.
Molecules are synthesised in the cell body (ER reticulum), and transported down the axon (anterograde)
Describe some of the features of synaptic vesicles
These have many receptors on them, which control their position in the cell, their position during synapse, fusion with the membrane etc.
