spread of the nerve impulse Flashcards
what are the different types of neurones?
multipolar neurons, bipolar neurons and pseudounipolar neurons
what are the key characteristics of multipolar neurons?
they are most abundant in the CNS, their cell body is closest to their dendrites.
what are some key characteristics of bipolar neurons and where is an example of where they may be found?
bipolar neurons have a dendritic tree which carries impulses from the dendrites to the cell body which interprets the information and passes it on down the axon. e.g. in a retina.
what are some key characteristics of pseudo unipolar neurons?
the electrical impulse comes from the dendritic tree and almost bi-passes the cell body which is budded off from the axon.. Mainly found in the spinal ganglia
what two features of the axon determine the speed at which the nerve impulse travels?
the diameter of the axon and whether it is myelinated or not
how does the speed at which the nerve impulse travels vary with the diameter of the axon?
the larger the diameter of the axon, the lower the resistance is. passive movement of charge is easier with lower resistance, therefore larger axons have faster passive change movement.
where do you find schwann cells?
in the peripheral nervous system (schwann cells form the myelin sheath around peripheral axons of neurons)
where do you find oligodendrocytes?
in the CNS (in the white matter)
why is the myelin in oligodendrocytes and schwann cells chemically different in composition?
these two cells have different embryological origins
what type of myelin does Multiple Sclerosis attack?
oligodendrocyte myelin (so the CNS is differentially affected)
what happens after the action potential has been generated in one region of the axon?
there is a refractory period during which a second action potential cannot be triggered.
where are action potentials generated in myelinated fibres?
ONLY at the node of ranvier.
what is the purpose of saltatory (jumping) conduction?
increases the distances which can be covered in a given time and saves energy on ion transport.
