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.
