PBL 2 Flashcards
what are glial cells?
these provide functional and structural support for the neurones. e.g. Schwann cells
what are the key features of cell bodies?
they hold the nucleus.
It is the site of protein synthesis, which occurs on small granules of rough endoplasmic reticulum called nissl substance.
what is a ganglion?
a group of neuron cell bodies in the peripheral nervous system
what is the function of dendrites?
extend out-ward from the cell body and are specialized to receive chemical signals from the axon termini of other neurons. Dendrites convert these signals into small electric impulses and transmit them inward, in the direction of the cell body.
what is the membrane of the axon called?
what is the axon hillock?
the axolemma
tapered end of the cell body
what is myelin?
what is it composed of in the CNS? and the PNS?
a layer of insulating lipid
CNS- oligodendrocyte cells
PNS- Schwann cells
What are Nodes of Ranvier?
gaps between the myelin sheaths that allow for saltatory conduction of impulses
why does the axon terminal contain a large number of mitochondria?
to facilitate secretion of neurotransmitters
describe the connective tissue layers that form nerves?
endometrium surrounds axons of individual neurones. neurones bundle together to form a fascicle which is surrounded by a perineurium. a collection of fascicles is then surrounded by an epineurium
what are unipolar neurones?
Here the cell body is at one end of a single unbranched axon, and there are no dendrites. These can be found in the cochlear nucleus of the brain.
what are bipolar neurones?
These neurones have two processes arising from a central cell body – typically one axon and one dendrite. These cells are found in the retina.
what are multipolar neurones?
They have one axon and many dendrites, with a cell body displaced to one side of the axon. Motor neurones are a prime example of this.
what are psuedounipolar neurones?
They have one axon which is divided into two branches by the presence of the cell body. Sensory neurones are all Pseudounipolar.
describe the action potential?
In the resting state, the nerve cell membrane is polarized due to differences in the concentrations of ions (Na+/K+) across the plasma membrane
In response to the arrival of an action potential, voltage-gated Na+ channels open and Na+ floods into the neuron= rapid depolarization.
Voltage gated K+ channels then open and K+ floods out of the neuron=repolarization.
The Na+/K+ pump then exchanges Na+ and K+ to restore the resting membrane potential after hyperpolarization.
Synaptic knobs contain vesicles which store neurotransmitters and are released into the synaptic cleft by exocytosis in response to an action potential.
Neurotransmitters diffuse across the synaptic cleft and act on specific receptor sites on the post-synaptic neuron surface
what does the speed of conduction of an action potential depend on?
Larger diameter axons have a higher conduction velocity, which means they are able to send signals faster. This is because there is less resistance facing the ion flow
