A&P Test 2 Flashcards
What are the different ways to classify a neuron?
Size
Myelenation states
What is a A neuron?
a heavily myelinated neuron
What is a B neuron?
a lightly myelinated neuron
What is a C neuron?
a non-myelinated neuron
What is the biggest size a neuron diameter can be?
20 mm
What is the smallest size a neuron diameter can be?
0.5mm
Important information is usually sent through
a bigger, myelinated neuron
Motor functions are sent through
bigger, myelinated neurons
Less important information is usually sent through
smaller, less myelinated neurons
What are examples of the less important information that is sent via neurons?
Tickle
Cold
Warmth
Myelinated (A fibers) are subdivded into what categories?
Alpha
Beta
Gama
Delta
What is the largest subcategory of an A neuron?
alpha
Rank the A neuron subunits from smallest to largest
Delta<Gama<Beta<Alpha
All neurons have a
Cell body
What is another name for the cell body in a neuron?
Soma
What are the projections from the cell body called?
Dendrites
Can dendrites connect to the cell body?
Yes
Excitatory connections on the dendrites create a more ______ membrane potential
postive
Inhibitory connections on the dendrites create a more ______ membrane potential
negative
What is the projection from the soma that an action potential moves down called?
Axon
Is the axon hillock more negative or more positive?
more Negative
Most axons are
myelinated
What is a presynaptic terminal?
The very end of an axon before it connects to a target
What are the “brakes” in the nervous system?
Axon hillocks and Chloride
What is the neurotransmitter that is used on the axon hillock?
GABA
If we remove all of our endogenous GABA, what would happen?
We would have seizures
What is an example of something that removes all of our natural GABA?
Alcoholism
What is GABA mediated neurotransmission?
Endogenous GABA that increases permeability to Cl- which makes the cell more negative.
What is the concentration gradient of Cl-?
higher on the outside, lower on the inside
Why don’t we have outside excitation at the axon hillock?
It would bypass the soma making the soma irrelevant
What are the 2 main categories of brain cells?
Neurons
Glial cells
Which brain cell proliferates the fastest?
glial cells
What is the smallest glial cell?
microglia
What are the macroglial cells?
Astrocytes
ependymal
oligodentrocytes
-schwann
why are astrocytes named astrocytes?
They are shaped like a star
What is a big part of the functional BBB?
Astrocytes
Where is one place that astrocytes connect to?
to the outside of an endothelial cell on a capillary
It wraps itself around the true part of the BBB
How are astrocytes oriented where it connects to capillaries?
It wraps itself around the cell
Where is the BBB found?
in between the capillaries of our endothelial cells
What is the true part of the BBB?
the tight junctions between endothelial cells an capillaries
What is one thing that astrocytes are very good at?
maintaining electrolytes in the CSF
If there is an excess of electrolytes in the CSF, what happens?
The electrolytes can be tucked away in the astrocytes
What are the 3 main functions of astrocytes?
Supportive structure for the BBB
Regulate electrolytes in the CSF
Maintain the pH of the CSF
Where are astrocytes found?
surrounding the CNS
What are on ependymal cells?
cillia
What is the function of ependymal cells?
Producing and moving of CSF
Where is the main place CSF is made?
ependymal cells
What are the myelin producing cells in the CNS?
oligodendroctyes
What forms the myelin sheath in the PNS?
Schwann cells
What is the function of the microglial cells?
Act as macrophages and work as the immune system in the CSF, keeping the area clean and free from debris
What are the decision making cells?
multipolar neuron
What does a multipolar neuron look like?
What decisions do multipolar neurons make?
to send an action potential or not
What is the best example of the bipolar neuron?
type of photoreceptors in a retina that send messages through the optic nerve
What does a bipolar neuron look like?
Bipolar neurons are typically used for what?
specialized senses (optic nerve)
Bipolar neurons are primarily sensory, meaning they don’t require a lot of connections to other cells. This designed is set up to
sense information and then pass that information as action potentials to some other area of the brain.
What are the majority of the sensory cells that are found immediately outside of the spinal cord?
Pseudounipolar neurons
Where are the decisions made in relation to a pseudounipolar neuron?
the sensor itself
What does the soma of a unipolar neuron exist for?
as a place to build proteins and replace things that need to be maintained within the neuron
What is an example of a multipolar neuron?
a motor neuron
Where are true unipolar neurons found?
in lower life forms, not in humans
What is somatic sensation?
Consciously discernable sensations
Free nerve endings are what type of sensor?
pain
what’s another term for a pain receptor?
nociceptor
free nerve ending
More distortion or stretch on a pressure sensor equals
more sodium entering the cell and more action potentials that will be fired
What is a mechanoreceptor?
a sensor that takes some kind of physical environmental disturbance and turns that into an electrical signal
What is an example in adaptability?
a baro receptor that adjusts it’s action potentials to a high map so that the body recognizes the prolonged BP as normal.
How long does it take for baroreceptors to recognize an elevated BP as “normal”
2 days
What is reverse adaptation?
When you have a stimulus for an extended period of time, and instead of the body recognizing it as normal, the body ramps up the action potentials
What are examples of sensory receptors?
Pacinian corpuscle
Meissner’s corpuscle
Golgi tendon apparatus
muscle spindle
How are muscle spindles oriented?
they wrap around muscles.
What do muscle spindles tell us?
If a muscle has completed the task it was supposed to do
A stimulation has to reach ______ to create an action potential
threshold
What is threshold?
The bar that depolarization has to get over to.
If we just barely depolarize over threshold, what will result?
An action potential will occur after a little bit of time has passed
What makes the plateau in the top of a cardiac action potential?
Slow Ca++ channels opening slowly after depolarization.
When chloride channels are open, what does chloride do?
Comes into the cell down it’s concentration gradient and makes it more negative
what ion keeps the brakes on the nervous system?
chloride
ca++ coming into the cell is going to be
stimulatory
calcium is
large and charged
how does calcium contribute to the cell becoming more negative?
It sits in the Na+ leak channel openings and blocks Na+ from entering
how does hypocalcemia contribute to a more excitable cell?
The less Ca++ molecules there are to block the Na+ leak channels, the more Na+ is going to go into the cell and make it positive
What can you give to a hyperkalemic person to help decrease their cell’s excitability? why?
Ca++
Ca++ blocks leaky Na+ channels meaning less Na+ can come in
Calcium’s effect on a resting cell is typically
inhibitory, slows down irritable tissue, and stabilized membrane potential
Why doesn’t Ca++ block K+ channels?
K+ pushes Ca++ out of the way if it settles on the channel
If a motor neuron is not surrounded by a normal amount of Ca++, what is the result?
The motor neuron is more + and excitable leading to more contractility of the skeletal muscle
What causes Trousseau’s sign?
Hypocalcemia. Less Ca++ being available around motor neurons, making the neurons more +++ because Na+ is coming into the cell. This hyperactivity leads to the hyperactivity of skeletal muscles. This causes Tetany
What is the Chvostek’s sign named after?
A Russian guy
Does Ca++ effect fast Na+ channels?
No, only the leaky Na+ at rest
What is an ion besides Ca++ that helps settle down an excited cell by hyperpolarizing a Vrm?
Mg++
Not sure how
What are some things that effect AP propagation?
Length of the nerve
diameter of the nerve
What are the properties of a neuron that sends action potentials quickly?
Short, wide, and insulated
How does a schwann cell orient itself?
It wraps itself in a spiral around a neuron.
The layers are compacted, pushing out the water that was in the cell originally becoming a good insulator.
A Schwann cell is a
lipid compound
What are 2 ways to speed up an action potential?
Increase VG Na+ channels
Decrease the amount of Na+ being pumped out
How does a neuron decrease the amount of Na+ leaving the cell?
It insulates the outside of the cell with myelin, making it so that Na+ is blocked from leaving the cell
What are 2 things that myelin does?
Speeds up propagation of action potentials
Creates a more efficient cell
Why is reduced ATP requirements a good thing in a neuron?
If we have a block that isn’t allowing blood to feed the neuron, it gives it a little longer survival because it doesn’t need as much energy
What are the spaces between the myelin called?
Nodes of Ranvier
What is found in the nodes of ranvier?
Lots of fast sodium channels, K+ channels, and Na+/K+ pumps
Which type of neuron is harder to anesthetize? why?
a myelinated neuron
Because it has a really high fast sodium channel density located at the nodes of ranvier
What is saltatory conduction?
The jumping pattern of Na+ going from one node of ranvier to the next and exciting more fast Na+ channels, allowing more Na+ into the cell
What helps protect neurons from crush injuries?
myelin. It protects the neuron by providing robustness
What is included in the CNS?
Brain
spinal cord
cranial nerve 2 (optic nerve)
retinas
What are the cells called in the CNS that maintain and produce myelin?
oligodendrocytes
What is included in the PNS?
everything outside of the spinal cord
What cells are found in the PNS that maintain and produce myelin?
Schwann cells
Are oligodendrocytes easy to replace?
no
If we lose myelin around our optic nerve, we may have
cloudy or delayed vision, or loss of peripheral vision
When did Giullain-Barre syndrome spike and why?
after covid, because antibodies were made against covid and were not just specific to covid. they also reacted with the nervous system
What is MS
multiple sclerosis
a demyelinating disease that happens in our motor system
How does MS work?
Over time, the fast Na+ channels and K+ channels disappear underneath the myelin sheaths leaving only the high density areas at the node of ranvier. Na+/K+ pump do repopulate under the myelination.
In MS when the myelination is gone, the movement of Na+ downstream is stunted by the Na+ being pumped out during the whole length of where the myelin used to be.
The action potential can no longer reach it’s target, the muscle, which can lead to paralysis
Does Guillain-Barre last forever?
No, it goes away over time
What causes demyelinating diseases?
Infection
autoimmune reactions to vaccines
genetics plays a big role in this
What is a synapse?
The point where neurons connect and communicate with eachother
What is another name for an electrical synapse?
Gap junction
what are connexons made from?
6 Connexin proteins that fit together to form a tube
How do connexons work?
2 connexons, one on each cell line up to each other and create a pathway for small molecules to pass through
What is the most common ion that moves through gap junctions?
Na+
What is a very fast way of sending an action potential from one cell to another?
Electrical synapses though gap junctions.
This cuts out the time of a chemical synapse where the ligand has to bind and cause confirmation change etc.
Unlike a chemical synapse, an electrical synapse can send action potentials
both directions.
What causes a lot of abnormal reentry problems in the heart?
Electrical synapses (gap junctions) sending action potentials in both directions.
The ______ the ion the _____ it moves through a gap junction
smaller; faster
What is one determinant of how easy an action potential is going to get from one cell to another?
how many gap junctions are available
Is there a lot of gap junctions in the pacing areas of the heart?
no, it’s mostly chemical synapses which allows for a built in delay.
some smooth muscle has some gap junctions that allow
neighboring smooth muscle cells to act as a unit
The target to a neuron and the neurotransmitter defines
what a cell is going to be able to do
In the heart, ACh is
inhibitory
in skeletal muscle, ACh is
excitatory
What is the presynaptic terminal?
The sending cell
What is the postsynaptic terminal?
The receiving cell
What does GABA do in the axon hillock?
Increases permeability to Cl-
