exam 3- nervous system 1 Flashcards
name of the cells that are support cells, that support the neurons in the nervous system
neuroglia (glial cells)
the nervous system is a very complex system, has hundreds of billions of…
functioning and supporting components
how many different classes of neurons are there?
name them
3 classes (billions of neurons fall into 1 of these 3 classes)
1- bipolar
2- pseudounipolar
3- multipolar
describe the class of bipolar neurons
2 prominent extensions going off of cell body in opposite directions - single dendrite going off in one direction, single axon in other direction
sensory in function: vision and olfaction
describe the class of pseudounipolar neurons
the dendrite and axon are continuous and bypass the cell body (cell body itself does not function in integration of the incoming signals)
- (dendrite functions like an axon b/c can carry an AP), dendrite called peripheral axon- carries sensory info from peripheral sense receptors in body to the cell body)
- axon called the central axon- carries sensory info towards CNS
in pseudounipolar neurons, the dendrite is called the ___ and the axon is called the ____
peripheral axon
central axon
describe the class of multipolar neurons
multiple dendrites coming off of cell body and one long axon coming off too
- this is our motor neuron (represents the neuron we learned about in AP)
the neurons in the nervous system are called ___ cells
b/c…
post-mitotic cells, meaning once they mature, they no longer divide
- exception is the neurons in the hippocampus of the brain which continually divide in order to form and maintain new memories
what are the two categories of myelinated glial cells
schwann cells (PNS)
oligodendrocytes (CNS)
describe schwann cells and oligodendrocytes
these synthesize myelin (lipid substance), incorporate it into their cell membranes, cell membranes grow and envelop it around their axons in circular arrangements
- myelin is pure lipid, nonpolar, nothing will get through –> no sodium and potassium current, so they act as insulators in these nerve cell axons –> saltatory conduction
one schwann cell and one oligodendrocyte will myelinate how many axons?
1 schwann cell will myelinate 1 axon of 1 neuron
1 oligodendrocyte can myelinate many axons of diff neurons
describe microglia
part of the defense in the CNS
- at rest, exist in non-activated form –> activated in response to injury/damage to neurons of CNS –> transform into activated microglia (major function is phagocytosis- clean up damage from injury)
describe the function of astrocytes
- regulate cellular environment and surrounding environment that neurons of nervous system exist in
- sort of connect the capillaries that feed the brain to the neurons, involved in transporting nutrients from the blood to the neurons (nourishing function to neurons of CNS)
- brain needs constant high supply of nutrients b/c it doesnt make its own, astrocytes help facilitate this
- help take up and recycle neurotransmitters used in the brain
describe astrocyte foot processes
foot processes surround individual and groups of neurons and help them isolate from other groups of neurons (protect them from other groups of neurons that may be firing APs to prevent interference)
- also lots of foot processes at the synapse of neurons- take up and recycle potassium, help facilitate electrical function of neurons
spinal cord injuries do not heal because ___ pathways are so dense that neurons cannot regrow or get through
astrocyte