Exam 3 Nervous System 1 Flashcards
what are the three types of neurons?
bipolar, pseudounipolar, and multipolar
what do bipolar neurons function in?
sensory function; specifically vision and olfactory reception (sight and smell)
what do bipolar neurons look like?
two prominent extensions going off the cell body in opposite directions
what do pseudounipolar neurons look like?
continuous dendrite and axon that bypass the major part of the cell body
what is special about pseudounipolar neurons?
the dendrite can carry an AP (functions like an axon)
what is the dendrite of the pseudounipolar neuron called and why?
peripheral axon; carries sensory information from the peripheral sensory receptors in the body toward the cell body)
what is the axon proper of the pseudounipolar neuron called and why?
central axon; carries sensory information from the dendrite/peripheral axon toward the CNS where it connects to part of the CNS
pseudounipolar neuron cell body
DOES NOT appear to function in integration of incoming sensory signals, unlike motor neurons
what do multipolar neurons look like?
dendrites at the top (multiple coming off the cell body) with one long prominent axon which ends at the terminals
what do multipolar neurons function as?
motor neurons
what are neurons in the CNS called and why?
post-mitotic cells; once they mature, they no longer divide
what is the exception to post-mitotic cells in the CNS?
neurons in the hippocampus; they continually divide in order to form and maintain new memories
what is the function of Schwann cells and Oligodendrocytes?
synthesis myelin, incorporate it into their cell membranes, cell membranes grow, and they envelop the axons of neurons in a concentric circular arrangement
where are Schwann cells found?
Peripheral NS
where are Oligodendrocytes found?
Central NS
what does myelin act as?
an insulator on the axons because it’s nonpolar lipid so there is no Na/K current
what do myelinated cells exhibit?
saltatory conduction
what is the relationship between one Schwann cell and the axon of a neuron that it will myelinate?
1:1
how many axons of different neurons can Oligodendrocytes myelinate?
many
what is the general function of Astrocytes?
regulate the cellular environment and the surrounding environment that neurons exist in
what are the specific functions of Astrocytes?
- connect the capillaries that feed blood to the brain to the neurons
- involved in transporting nutrients from the blood to the neurons
- nourishing function to the neurons of the CNS
what percent accounts for the weight of the brain on the body’s weight? and how much is the brain responsible for metabolism?
brain weight is about 8% of body weight, but is responsible for about 25% of total metabolism
what is the function of Astrocytes and foot processes?
astrocytes surround groups of neurons or individual neurons and help isolate them from other groups of neurons
what else do Astrocytes do?
- take up and recycle K
- help facilitate the electrical function of neurons
- help take up/recycle NTs used in the brain
what is laid down first in the development of the brain?
Astrocytes; they provide scaffold for the way neurons grow and form neural pathways
what are Microglia apart of?
defense within the CNS
how are Microglia at rest?
non-activated, non-differentiated
how are Microglia activated?
usually in response to some injury or damage to the neurons in the CNS
what is the main function of activated Microglia?
phagocytosis
what is the function of Ependymal cells?
form the epithelial lining that separates the interstitial fluid of the brain that surrounds the neurons and the outer fluid (cerebrospinal fluid)
what do some specialized forms of Ependymal cells do?
secrete the cerebrospinal fluid
where do all the glial cells come from?
there is an undifferentiated population of stem cells (precursor cells) that can give rise to any of the 4 types of glial cells
what does uncontrolled glial cell precursor growth result in?
tumors
Astrocytoma
usually slow-growing tumor; from astrocyte overgrowth
Glioblastoma
fast growing and very dangerous
anatomical POV of the NS
central: brain and spinal cord
peripheral: cranial and spinal nerves that leave the CNS and travel out to the peripheral parts of the body
functional POV of the NS
peripheral NS divided into Afferent and Efferent NS based on which direction the AP is traveling
Afferent NS
carries signals TOWARD the CNS (sensory system)
Efferent NS
carries signals AWAY from the CNS back out to the peripheral parts of the body (motor system)
Somatic NS
motor neurons that connect to the skeletal muscle
Autonomic/Visceral NS
connects to the cardiac muscle and smooth muscle that surrounds the bodies internal organs
what is the Enteric NS also known as?
solarplexus
what are the three classes of senses for Afferent/sensory neurons?
- external (somatic senses)
- special senses
- internal senses (visceral senses)
external (somatic) senses
come from skin, muscle, joints
ex: touch, pressure, heat, cold, external environment stimuli
special senses
vision, hearing, equilibrium, smell, taste
internal (visceral) senses
things that are adjusted but don’t have conscious thought of doing it
ex: how full is your stomach? HR monitoring, BP monitoring
how are afferent/sensory neurons names?
in which one is stimulated first
where are first-order neurons/primary afferent neurons usually found?
peripheral NS, usually associated with sensory receptor; carries info to the CNS (usually spinal cord) where it then synapses with second-order sensory neurons
what is the function of the thalamus?
relay station in the brain that sends the signals to the appropriate areas so they will register as conscious sensations
reflex arc
neural circuit that serves as a template for how neural systems work; most start with a peripheral sensory receptor and sensory neuron, they go toward the spinal cord, connect with a motor neuron, the motor neuron leaves the spinal cord and activates the effector
ganglion
a cell body or group of cell bodies located outside the CNS
dorsal route ganglion
at the base/root of spinal nerve; sensory neuron comes in and the cell body is outside of the CNS
what does the organization of reflex arcs usually follow?
Bell-Magendie Rule
Bell-Magendie Rule
in reflex arcs, the sensory neurons enter the brain or spinal cord by way of the dorsal route of the cranial or spinal nerves and the motor neurons exit the brain and spinal cord by the ventral route of the cranial or spinal nerves
multiple synapses in the reflex arc
first: between the sensory neuron and the interneuron
second: between the interneuron and the motor neuron
(then the motor neuron leaves the CNS)
what is a reflex arc with interneurons involved called?
a polysynaptic reflex arc
what are the two layers that the spinal cord has?
outer layer = white matter
inner layer = grey matter
what is the outer white matter of the spinal cord from?
axons of the sensory and motor neurons that are myelinated
what is the inner grey matter of the spinal cord from?
cell bodies of interneurons and motor neurons that are not myelinated
