1.2- CNS Cells, Cell Anatomy, & Neural Transmission Flashcards
What is the basic building block of the nervous system?
Neurons
What two ways are neurons different from other cells?
Excitable & Conductive
True or False: A fetus develops more neurons after birth.
False. A fetus has all neurons at birth.
True or False: Mature neurons do not divide.
True
True or False: Neurons are all the same size.
False. Neurons can be very long or very short (axon can be up to 1 yard long).
What is another name for cell body?
Soma
What is the gooey, watery substance in the cell that contains everything else?
Cytoplasm
Where is the nucleus located in healthy cells? in diseased cells?
The nucleus is central in healthy cells. The nucleus is displaced in diseased cells.
What are the two types of ribosomes?
Free ribosomes & rough endoplasmic reticulum
What is the function of free ribosomes?
to make protein for cells own use
What is the function of rough endoplasmic reticulum?
produces neurotransmitters
What part of a cell makes protein?
Free ribosomes
What part of a cell produces neurotransmitters?
Rough ER
What is the function of the Golgi apparatus?
packages neurotransmitters
What part of a cell packages neurotransmitters made by the rough ER?
Golgi apparatus
The Golgi apparatus packages neurotransmitters into a _____________.
synaptic vesicle
What part of a cell is the powerhouse of the cell/releases energy?
Mitochondria
What is the term for the extension of the soma that receives transmission from other cells (input site)?
Dendrite
What is the function of the dendrite?
conducts impulse from the end of the dendrite towards the cell body
What type of specific neuron has the most dendrites?
spinal motor neuron
On average, more dendrites are found on _____ neurons.
motor
On average, less dendrites are found on ____ neurons.
sensory
What is an output unit of the cell that sends impulses to the next target cell?
Axon
How many axons on a neuron?
one, but it can go very long distances
Where can an axon impulse go? (3 things)
to other neurons, muscle cells, or glands
What is the narrowed area of the cell body that forms into the axon?
Axon hillock
What is the broadened end area of the axon just before the synapse?
Presynaptic terminal
What helps with the flow of material to and from cell body and presynaptic terminal?
Microtubules
What are the two transport methods along the microtubules?
Anterograde transport and retrograde transport
What type of transport is the flow of material AWAY from the cell body TOWARD end of axon?
Anterograde transport
What type of transport is the flow of material from the end of the axon back towards the cell body?
Retrograde transport
Synaptic vesicles return via ________ from the synapse after release of the _______ for reuse.
retrograde transport; neurotransmitter
What type of transport slows with the aging process?
Axoplasmic (process of anterograde & retrograde transports together)
What is the term for the gap between neurons?
synaptic cleft
Where is the site for interneural communication?
synaptic cleft
The synapse includes the ________, _________, and the ________.
pre-synaptic membrane, synaptic cleft, and the post-synaptic membrane
Where does the chemical process of transmission occur?
synapse
Where is a synapse located?
It can be located anywhere on a dendrite, cell body, or axon.
Some areas of a synapse are more excitable than others. What is the more excitable area?
Dendrite -> takes less neurotransmitters
How are neurons classified?
- Number and arrangement of parts
2. Function
What type of neuron has many dendrites from the cell body with only 1 axon?
Multipolar neuron
What is the most common cells of the nervous system?
multipolar neurons
What type of neuron receives huge amounts of input from multiple places?
multipolar neurons
What type of neuron travels from the CNS to the muscle?
Efferent (motor) neurons
What is an example of an efferent neuron?
spinal motor neuron
What is the traveling path of an efferent (motor) neuron?
from the CNS to muscle
What type of neuron has 2 primary processes from soma- the dendrite and axon?
bipolar neuron
What type of neuron might have a dendrite root that divides into multiple dendritic branches?
bipolar neuron
What type of neuron has high precision in reception and transmission?
bipolar neuron
Why does a bipolar neuron have high precision in reception and transmission?
because 1 single dendrite receives info and transmits to only 1 other neuron
What type of neuron is a bipolar neuron where dendrite receives impulse in a sensory organ and transmits back towards the CNS?
Afferent (sensory) neuron
Afferent (sensory) neuron- bipolar neuron where _____ receives impulse in a sensory organ and transmits ______________
dendrite; back towards the CNS
Examples of afferent (sensory) neurons
retina, inner ear, taste buds
What is a subclass of bipolar cells?
Pseudounipolar
What type of neuron appears to have a single projection from the cell body that divides into 2 axonal roots (no true dendrites)?
pseudounipolar
What are the 2 types of axonal roots of a pseudounipolar neuron?
- Peripheral axon
2. Central axon
What is long and myelinated, conducts sensory info from the sensory organs to the cell body?
Peripheral axon
What conducts info from soma to spinal cord?
Central axon
What is the travel path of a peripheral axon?
from the sensory organs to the cell body
What is the travel path of a central axon?
from soma to spinal cord
Why does a pseudounipolar neuron travel quickly?
it skips the soma
___________ neurons - CNS to smooth or skeletal muscles
Efferent (motor)
__________ neurons - sensory info from periphery to CNS
Afferent (sensory)
__________ - process info locally or sends info short distances from one area of the nervous system to another (processes info at the spinal cord level)
Interneurons
Which direction do efferent neurons travel?
from CNS to smooth or skeletal muscles
Which direction do afferent neurons travel?
from periphery to CNS
What type of support cell provides support for neurons and help with neural transmission?
Glial cells
What type of cell may play a role in Alzheimer’s disease and MS?
Glial cells
Glial cells are classified into what two sizes?
Microglia and macroglia
What type of cell acts as phagocytes?
Microglia
Microglia cells are only found in the _____.
CNS
What do microglia cells do?
Act as phagocytes- destroy bacteria and old or damaged cells
What are the three types of macroglia cells?
- Astrocytes
- Oligodendrocytes
- Schwann cells
_______ are star shaped cells found in CNS.
Astrocytes
Where are astrocytes found?
CNS
What 3 things do astrocytes do?
- role in cell communication
- act as scavengers to clean up debris (remove spent neurotransmitter)
- transport nutrients to nerve by connecting neuron to capillaries (part of blood-brain barrier)
What type of cell has a role in cell communication (stimulated by other neurons, change in shape or pressure)?
Astrocytes
What type of cell acts as a scavenger to clean up debris (remove spent neurotransmitter)?
Astrocytes
What type of cell transports nutrients to nerve by connecting neuron to capillaries?
Astrocytes
Problems with astrocytes can lead to _______.
scarring in brain causing tumors and seizures
What type of cell produces myelin in CNS?
Oligodendrocytes
What is the lipid and protein layer that wraps around axon?
Myelin
What insulates electrical conduction so one fiber does not short out on another?
Myelin
More and thicker myelin = __________
faster conduction
Not continuous, areas not myelinated called ______
Nodes of Ranvier
Diseases (MS) can attack ______.
myelin
What is myelin?
a lipid and protein layer that wraps around axon and insulates electrical conduction so one fiber does not short out on another
What is the function of a oligodendrocyte?
to produce myelin in CNS
What type of cell produces myelin in the PNS?
Schwann cells
Schwann cells are the only support cells of the PNS. It must do what three things?
- make myelin
- clear debris
- support neurons
Each Schwann cell may myelinate ______ axons.
several
What is the outer plasma membrane of the Schwann cell called?
Neurolemma
What is Neurolemma?
the outer plasma membrane of the Schwann cell- covers the myelin produced around the axon in the PNS
True of False: Neurolemma degenerates when cut.
False. Does NOT degenerate when cut.
(why nerve can regenerate in PNS -> can remake connections) *will degenerate in CNS
What happens if a soma is damaged?
the entire nerve cell dies
Wallerian degeneration occurs when ___________.
axon is damaged
What 4 things occur during Wallerian degeneration?
- damaged segments retract away from each other
- distal axonal segment degenerates & pulls away from myelin sheath
- axon terminal degenerates & dies
- glial cells scavenge the area
What is axonal sprouting?
if soma of injured cell is intact, regeneration of PERIPHERAL nerves is possible
How can an injured axon regrow to a new target?
- when axon degenerates, it leaves before the neurolemma (like a hollow pipe)
- this pipe can act as a guide for axonal regrowth to direct it back to the proper target
Where is neurolemma produced?
PNS (one of the reasons regeneration does not occur in the CNS)
What is neuroma?
nerve tumor of free nerve ending
How does a neuroma occur?
when a nerve tries to regenerate and can’t find its way
What is the growth rate of an axon?
1mm/day
True or False: An axon returns to a pre-injury state.
False. Not complete or same as before injury.
Why might an axon not be the same as before injury?
- may go to wrong target
2. schwann cells remake myelin but have more nodes (slows conduction)
Neurons function because of a difference in _____ _____ across the membrane created by having different _____ ______ on either side of the cell membrane.
electrical potential
electrical charges
How is the difference in electrical potential created?
by having ions with different electrical charges on each side of the membrane
There are 4 channels that allow ions to move back and forth across the cell membrane of the axon. One is a non-gated channel. What are the 3 gated channels?
- modality gated
- ligand gated
- voltage gated
What type of channel allows slow diffusion of a small number of ions via osmosis through the membrane?
non-gated channels (open all the time & allows constant dripping)
Describe Modality gated channels
- open in response to touch, pressure, hot, cold, etc
- only in sensory system
Describe Ligand gated channels
- open in response to neurotransmitter binding
- in post synaptic membrane
Describe Voltage gated channels
- open in response to changes in electrical potential across the membrane
- as one channel depolarizes it opens up the next channel
What type of gated channel opens in response to touch, pressure, hot, cold?
Modality gated
What type of gated channel opens in response to neurotransmitter binding?
Ligand gated
What type of gated response opens in response to changes in electrical potential across the membrane?
Voltage gated
What type of gated channel is only in sensory system?
Modality gated
What type of gated channel is in post synaptic membrane?
Ligand gated
What type of gated channel opens as the previous one depolarizes?
Voltage gated
Resting potential is _____mV.
Action potential is ______mV.
Resting potential is -70mV.
Action potential is +35mV.
What occurs when the axon has a negative ionic charge inside due to large negative molecules permanently trapped in the cell; outside there is a positive ionic charge due to Na+ ions?
Resting potential
Resting potential-
What type of charge is inside the cell? Outside the cell?
Inside the cell is a negative charge. Outside the cell is a positive charge.
With impulse transmission, when a stimulus is received, a ____________ of the cell membrane occurs.
reversal or depolarization
How does a reversal or depolarization of a cell membrane occur?
- started by opening of modality or ligand gated channels allowing Na+ (sodium) in the cell
- as Na+ enters, charge inside that area of the membrane rises to +35mV
What is it called when the adjacent membrane reaches the +35mV threshold and the next voltage regulated channel down the membrane opens?
Action Potential
*once tripped, the succession continues the entire length of the neuron
What happens when the impulse reaches the presynaptic membrane?
the synaptic vesicles containing the neurotransmitter flattens against the membrane emptying the neurotransmitter into the synaptic cleft
__________ - if axon is myelinated this process occurs much faster because depolarization will only have to occur where there is no myelin (Node of Ranvier)
Saltatory Conduction
What must happen after depolarization?
cell must return back to the resting potential
After depolarization occurs, cell must return back to resting potential. Another gate opens allowing __________.
K+ (potassium) to leave the cell.
After depolarization occurs, the cell must return back to the resting potential. Another gate opens allowing K+ to leave the cell. Then what happens?
the negative charge is restored, but actually becomes more negative, down to -135mV
(also a problem b/c Na+ is inside the membrane and K+ is outside)
What is the refractory period?
time between depolarization and restoration of the -70mV resting potential
What are the two types of refractory periods?
- Absolute refractory period
2. Relative refractory period
__________ - membrane is completely unresponsive to another stimuli (occurs during the time the membrane has a positive charge)
Absolute refractory period
___________ - occurs while restoration of the - charge is occurring (internal charge is more negative than the -70mV resting potential)
Relative refractory period
What type of refractory period occurs during the time the membrane has a positive charge?
Absolute
What type of refractory period occurs during the restoration of the - charge?
Relative
What type of refractory period may be responsive to a very strong stimuli?
Relative refractory period
What occurs via an active transport system that restores the resting potential?
Repolarization
What is the Sodium Potassium Pump?
the cell membrane uses energy (ATP) to actively eject Na+ while returning K+ into the cell
_________ - the cell membrane uses energy (ATP) to actively eject Na+ while returning K+ into the cell
Sodium Potassium Pump
What is a Node of Ranvier?
an area of no myelin
