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
what cells form the epithelial lining that separates the interstitial fluid of the brain and the cerebrospinal fluid (separate ventricles of the brain from actual neuron tissue itself)
- some specialized ones secrete the cerebrospinal fluid
ependymal cells
___ = name of fast-growing tumors
__ = name of fast-advancing tumors
astrocytoma
glioblastoma
the nervous system can be organized from a ___ POV, meaning… or a ___ POV, meaning…
anatomical POV, meaning CNS (brain & spinal cord) and PNS (cranial and spinal nerves that leave CNS and travel to peripheral parts of body)
or functional POV, PNS divided into afferent NS (carries impulses toward CNS, sensory motor neurons) and efferent NS (carries impulses away to peripheral parts of motor, motor system
describe the efferent NS
motor system (efferent NS) is divided into somatic and autonomic/visceral nervous system
SOMATIC- motor neurons that connect to skeletal muscle - used to be called voluntary NS
AUTONOMIC/VISCERAL- connects to cardiac muscle and smooth muscle that surrounds the body’s internal organs, used to be called involuntary NS
- autonomic divided into sympathetic and parasympathetic NS- both typically connect to same cardiac/smooth muscles that surround the same organ
- typically antagonistic to each other, have opposite effect (sympathetic= excitatory ; para = inhibitory)
in the autonomic NS, what do the parasympathetic and sympathetic regulate since smooth muscle contracts itself?
they regulate to what degree (speed/strength) the smooth muscle contracts
- in smooth muscle of GI tract, the para NS exerts much greater control that sympathetic (para does this thru enteric NS)
- enteric NS consists of billions of neurons of its own that run through circular and longitudinal muscle of GI tracts and regulate muscle contraction of smooth muscle of intestines (enteric NS known as solarplexis)
what are the 3 classes of senses
1- external senses = somatic senses, come from skin, muscle, joints (heat, cold, touch)
2- special senses = vision, hearing, equilibrium (pressure/touch), smell, taste
3- internal senses (aka visceral senses) = fullness of GI tract, monitoring of heart rate and blood pressure
describe sensory neuron order
afferent neurons are interconnected in a certain sequence and are named by which is stimulated first, then second, third..
1- first-order sensory neuron: primary afferent, usually found in peripheral NS, carries info the CNS, usually spinal cord (afferent neuron with its peripheral receptor that FIRST detects the stimulus) –>
2- second-order sensory neuron: synapses with first-order sensory neuron + located in spinal cord or medulla –>
3- third-order sensory neuron: in the thalamus in brain, sends to area to be registered as conscious sensations
what is the most simple neural circuit?
a reflex arc
briefly describe most reflex arc pathways
starts with a peripheral sensory receptor and sensory neuron –> go towards spinal cord and connects with a motor neuron –> motor neuron leaves spinal cord and activates an effector
-reflex arc has sensory receptor, sensory neuron, motor neuron, and effector
- the sensory neuron comes in, and the cell body is outside of CNS at the root of spinal nerve it’s traveling, so called a DORSAL ROOT GANGLION (ganglion defined as cell body or group of cell bodies located outside of CNS) - at root/base of spinal nerve
organization of reflex arcs follows what rule?
explain
Bell-Magendie rule
in reflex arcs, the sensory neuron enters the brain/spinal cord by way of the DORSAL ROOT of the cranial or spinal nerves and the motor neurons exit the brain/spinal cord by the VENTRAL ROOT of the cranial or spinal nerves
- in many cases, sensory neuron synapses in CNS with an interneuron, which makes connection b/w sensory and motor neuron (multiple synapses in reflex arc –> motor neuron then leaves CNS)
- when interneurons are involved, reflex arc is called polysynaptic reflex arc
describe white and gray matter of spinal cord
white matter comes from axons of sensory and motor neurons that are myelinated (white appearance)
inner gray matter gets its color from cell bodies of interneuron and motor neurons that are not myelinated
describe basic pathway of reflex arc starting with touching something hot
touch something hot –>stimulus travels up sensory neuron, hits spinal cord –> wraps around interneuron to motor neuron –> motor neuron travels back out of arc –> causes muscle to contract and pull hand away
reflex arc is the most ___ pathway between ___ and ___
direct pathway b/w stimulus and response
- respond unconsciously- respond to stimulus before consciously aware of stimulus (this is the advantage of the reflex arc, very fast b/c most direct path)
the more interneurons are recruited in a reflex arc, the more…
potential effectors you can activate –> the more sophisticated response you can give to a stimulus
ex: left foot steps on nail- stimulus goes up leg and synapses with 1 interneuron and goes out to flexer muscle, tells u to pick up that leg … at same time, stimulus can route to second pathway- excites muscle on other leg to take weight off leg you stepped on
3 effectors from 1 stimulus on response to painful stimulus:
- on left leg- extensor muscle is inhibited, flexer muscle activated
- on right leg- extensor muscle activated
