Exam 2 - Lecture 2 Flashcards
Action potential ___________ changes between cells.
Threshold.
This is the amount of sodium that needs to leak in before it triggers Fast Na+ channels to open and fire an action potential. Different types of cells will have different thresholds, and every single cell may have a slightly different threshold.
What will a weak stimulus that’s enough to fire an AP look like?
After it crosses the threshold, there will be a little notch indicating a delay in the action potential.
AP’s in the heart have ___________________. Why?
Plateaus at the top of the AP, makes the AP sustain longer, giving heart muscle time to contract and push blood through heart.
Extension of the AP in the heart is due to
Slow calcium channels
Chloride channels open in heart
Causes chloride to come into the cell, making the cell more difficult to excite (hyperpolarized)
Chloride is the one ion known as keeping __________ on the nervous system
The brakes. Keeps the activity at a controlled level.
Calcium can cause massive depolarization when it floods into the cell due to its ++ nature and high mV, but the _____ can happen to resting cells.
opposite. Calcium is big and clunky and can block Na+ channels, not allowing Na+ to pass through.
Less serum Ca++ = ?
Increased Na+ leaking into cell, making the cell more positive and more excitable.
Giving more Ca++ can result in what?
Makes the cell more negative due to the blocking of Na+ leak channels. Useful for treating Hyperkalemia!
Why does giving calcium lower a patients hyperkalemia?
Increased serum sodium -> blocks Na+ leak channels -> cell becomes more negative -> increased negativity of the cell wants to hold onto potassium -> LESS potassium leaking out of the cell = Lowering serum potassium
Why does a low calcium increase cell Vrm?
Less calcium blocking Na+ leak channels, results in an increase of sodium leaking into the cell, creating a more positive cell.
Calciums affect on a resting cell in general is ______
inhibition.
Why doesnt calcium block K+ leak channels?
K+ would just bump the calcium out of the way because its coming out.
Chovosteks sign is a result of
Hypocalcemia results in increased activity of motor neurons from them being in a positive state.
At rest, which sodium channels does calcium effect? Which do they not effect?
Only sodium leak channels at rest. They do not inhibit the fast Na+ channels.
What ion functions alot like calcium? How?
Magnesium. Has a very similar effect to lowering AP. Its also double positive and large, has a way of calming things down. Magnesium can treat heart problems where the tissue is irritable and/or firing too much, constantly depolarized.
Rate of electrical propagation (AP) is affected by what?
Affected by length of nerve, diameter, and whether it has myelin sheath. Shorter, wider and having myelin sheath all makes it faster. The opposite makes it slower.
Outdoor lights have _____. A/C unit inside has _____.
Small wires. Big wires.
Myelin is derived from
Sphingomyelin in the cell wall.
What does a Schwann cell do?
LIPID COMPOUND that grows and wraps itself around the neuron over time. Like rings of a tree. The water that was initially in the cell gets squeezed out, becomes a good insulator without the water.
the more Fast Na+ channels, the faster the AP can
Spread.
How does the myelin sheath affect the channels along the cell wall?
Blocks them and keeps them from operating.
When Na+/K+ pumps are covered up by myelin sheath, this reduces the cells ________ requirement, and also ______ AP.
Energy requirement, speeds up AP.
Myelinated neurons are less ______ than a non-myelinated neuron of a similar size.
Prone to ischemia.
In between myelinated sheaths on the neuron, the openings are called _____.
Nodes.
Nodes on neurons are _____ with fast Na+ channels.
Packed in high density. Helps speed things up and ensures enough Na+ comes in to make the jump to the next node.
Myelinated neurons typically require __________ (related to anesthesia)
more local anesthetic to block due to the high-density fast Na+ channels.
Which neuron has way more fast Na+ channels?
Non-myelinated neuron.
Saltatory conduction
The action of Na+ jumping from one node to another.
Node of Ranvier
Excites more fast Na+ channels to keep AP going.
Myelin structures are protective and add layer of _____
Robustness to the neurons.
Neurons are delicate and need myelin to be more resistant to crush injuries.
Glial cells
Supporting cells in the nervous system.
CNS support tissues name and what they do? do they reproduce?
Oligodedrocytes: maintain and produce myelin. Fairly difficult to replace, not good at growing new myelin once we reach adulthood.
CNS structures include
Brain, spinal cord, cranial nerve II (optic nerve), and retinas.
PNS support tissues and what they do? do they reproduce?
Maintained by Schwann cells. Able to reproduce myelin, as long as it’s not too bad/continuous.
Optic neuritis
Cloudy vision, delayed, loss of peripheral vision.
Guillain-Barre
Lots of people came down with after covid from body developing antibodies. Cross-reactivity with antibodies and causing affects to parts of the nervous system
Multiple sclerosis
Demyelinating disease with our motor system
What happens to the stuff under the myelin? Fast na+ channels, VG-K channels, etc.
Tend to disappear, dont typically get placed in the myelinated areas, usually placed at the node.
What does the cell place in the cell wall everywhere including under myelin?
Na+/K+ pumps. Can cause Na+ to leave the cell and stop AP because there are no sodium channels under myelin. Signal doesnt send.
Demyelination
Lose all the myelin but everything left over in cell wall does not function normal. Once it is setup, need to keep myelin in order to have normal AP.
Causes of demyelination
Genetics, infection, autoimmune hyperreactivity (vaccines), polyneuropathies.
Synapse is one way of:
One cell talking to another.
Direct electrical Synapses
Gap junctions: cylinders that park themselves in cell wall, lining up in cylinders with neighboring cell to communicate.
Connexon
Made up of 6 connexin proteins, allows ionic current to move through them between cells, parked in the cell wall. Allows cell to activate each other. faster than chemical synapse.
Negative effects of direct electrical synapses
Can continue bad electrical signals, such as ones around the heart causing abnormal rhythms
What can move through gap junctions?
Small ions, mostly sodium. Smaller, the faster. Calcium also can but its large and clunky, doesnt fit nearly as well as sodium.
Pacing areas of the heart have _____ into the electrical systems.
Delays built in. Function of having low # of gap junctions at very specific spots in heart giving the functional pause in order to work correctly.
High # of gap junctions = _________. Low # of gap junctions = ___________.
Relatively low resistance, easy to spread AP. High resistance and difficult to spread AP from one cell to another.
___ connexins make a connexon, _____ connexons make a gap junction.
6, 2.
_____ muscle have gap junctions.
Smooth.
Downside of chemical synapses
Longer to get the message across.
In the heart, ach is ________; In the skeletal muscle, ach is ____.
inhibitory, excitatory.
Ions moving through gap junctions use what type of transport?
Simple diffusion.
Which synaptic terminal is the receiving end with the receptors?
Post-synaptic.
Myelinated neuron classification
A = heavily myelinated
B = Lightly myelinated
C = Non-myelinated
Neuron sizes range from:
0.5 - 20 micrometers.
Information that needs to be sent quickly is sent on larger, myelinated neurons. e.g. skeletal muscle
Myelinated neurons start at _____ micrometers, while unmyelinated neurons have a range of:
1.0, 0.5 - 2.0
“A” fiber subunits
Alpha, beta, gamma, delta. Ranging from largest (alpha) to delta (smallest).
Neuron structure: cell body
Nucleus, mitochondria, place to build things that cell needs.
AKA Soma.
Neuron structure: Dendrites
Receiving ends of neurons, projecting from soma.
Neuron structure: Axon
proximal end of neuron, more negatively charged than dendrite ends, inhibitory in nature. Most axons are myelinated, send information quickly.
Dendrites mV? (Not a specific #)
Excitatory in nature, lightly negatively charged. All of these connections are going to influence what the cell is doing.
Soma mV is ________ and its mV on other areas of neuron?
-60. -10 on dendrites to -75 on axon.
Some of our neurons can have connections with over ____ of their neighbors, especially decision-making neurons (decision to turn themselves on our not)
10,000
Tail end of neuron: presynaptic terminal
Very end of axon, gives off neurotransmitters to post-synaptic terminal receptors.
Axon hillock
Very first portion of axon, takes inputs from NS, tend to suppress activity in the neuron. Inhibitory connections typically keep the brakes on CNS.
GABA
Neurotransmitter used at axon hillock. Gaba receptors on axon hillock tend to increase chloride permeability, making it more negatively charged and more difficult to excite.
If we removed GABA, what would happen?
Over the top crazy levels of NS activity, causing seizures.
Alcoholic for 20 years (GABA receptor agonist), body isn’t producing much of its own _____. If you take alcohol away, what happens?
GABA. Massive seizures and overactivity in CNS.
Heart on its own would want to beat at _____ without _____ telling it otherwise.
110bpm, nervous system.
Nervous system would want to fire at way too fast, without the __________.
natural inhibition of GABA.
Nervous system brakes are applied at
Axon hillock.
Characteristics of glial cells
Much more proliferative than neurons so they can divide and multiply.
e.g. If you have a brain tumor, probably a glial tumor and it proliferates quickly.
Microglia
Smallest of glial cells. Functions as the immune system within structures that contain CSF. Breaks down dead cells, gets rid of things that don’t belong in CSF. Act like macrophages.
Astrocytes
Macroglia, big part of functional blood blain barrier. Looks like a star, the appendages wrap around capillaries surrounding the nervous system. Part of the tight junction, providing support structure.
Astrocytes are good at maintaining ________.
Electrolyte/pH balance within the CNS in the CSF. Can be an electrolyte buffer by tucking away ions inside the astrocyte for a while.
They help out the kidneys with electrolyte management.
Ependymal cells
Macroglia, produce CSF, have motility structures with cilia on the outside to circulate CSF around the system.
Oligodendrocytes
Myelin producing cells within the CNS.
Schwann cells
Macroglia, myelin producing cells in PNS.
Blood brain barrier is found in between the __________.
capillaries of endothelial cells.
Neuron types: Multipolar
Dendrites, connect to other parts of NS, decision making cells. Take in lots of information and make a decision (whether or not to fire an AP).
e.g. motor neuron: pain sensors tell motor neuron something is painful, have to pull body away, decided by motor neuron.
think: decision making
Neuron types: Bipolar
Two projections, one with axon and one with dendrites. Used in special organs, specifically optic nerve, photoreceptors in retina. Designed to sense information and send info to brain.
think: special sensory
Neuron types: Pseudounipolar
majority of sensory cells parked in corridor immediately outside of spinal cord. They sense and send AP. Does not make decisions, just relays information.
think: sensory
Job of cell body in Pseudounipolar neuron:
place to build proteins/things that need to be maintained, supports rest of the structures.
true unipolar neurons
lower forms of lfie, Not found in humans, slightly different from psuedounipolar.
Somatic = ?
Sensible, we can feel it.
Somatic sensory receptors: Free nerve endings
Pain sensors, AKA nociceptors.
Somatic sensory receptors: Pacinian corpuscle, Meissner’s corpuscle.
Pressure sensors
Somatic sensory receptors: Golgi tendon apparatus
pressure/stretch sensors giving us feedback about what our skeletal muscles are doing.
Somatic sensory receptors: Muscle spindles
Stretch sensors interwoven into skeletal muscles that confirm whether muscle contracted or not.
Somatic sensory receptors rely on ____ to send AP?
Rely on Na+ permeability to send action potentials. They stretch/detect pressure, allow Na+ in. Take an environmental disturbance then relay a signal to rest of body.
Adaptation of somatic sensory receptors
ability of sensors to adapt to the environment/blunted response.
e.g. Baroreceptors:
normal MAP of 100, has normal amount of sodium coming into cell.
When MAP goes to 150, more sodium floods in, AP occur at a faster clip, info fed to brain stem, thinks pressure is too high, then makes adjustments.
When MAP stays at 150 for 2 days, that is the new normal and normal amount of sodium is coming into cell, baroreceptor becomes desensitized to high pressure.
Some sensors adapt slow, most adapt quickly. This example is relatively slow.
If baroreceptors didn’t reset/adapt and continue to fire at a fast clip, it will be __________.
Limited in its ability to respond to further changes in new normal.
MAP going from 150-200 won’t change rate of AP, but if they originally adapted then it would change the rate of AP.
Somatic sensors are most concerned with:
Sensing CHANGES.
Some neurons are buried into nerve bundles, making them ___________.
More difficult to block with local anesthesia.
Where does muscarine come from?
Rainforest
What part of astrocytes are bound to endothelial capillaries?
Astrocytic infoot
What are the receptors in the optic nerve/retina
Photoreceptors
If the nervous system had __________ neurons, it will get rid of them
100,000,000
