Lecture 7; 9/11 Flashcards
Test 2
What is sub-threshold?
Below the threshold required to have an AP
What is acute sub threshold potentials?
Weak stimulus/depolarization
Define: Threshold
Bar the stimulus/depolarization has to get over to have AP
The higher the stimulus over the threshold =
The faster the AP (also means stronger stimulus)
T/F: Every cell’s threshold potential is about -65
F
Every cell’s threshold for an AP is different depending on the type of tissue
What happens if the stimulus barely crosses the threshold?
Delayed AP
What is L-Type?
V-G Ca++ channels
What do L-type channels do in the heart?
They open slowly after depolarization which results in the plateau
Ca++ floods into the heart causing depolarization and contraction of the myocardial.
What does the depolarization plateau tell you?
How well the heart is going to pump
How long should the depolarization plateau be?
About 0.5 seconds
Compared to the usual 1ms
This gives the heart muscle time to contract and pump blood
If we decrease Cl- in the nervous system what could happen?
Seizures
We want to keep the nervous system_____
hyperpolarized
IV Ca++ and Mg++ _______ neuronal and muscular cell electrical excitability
Decreases
“Calming effect”
Describe a Calcium
Double charged
Large and clunky
Huge concentration gradient
Hangs out by cell wall
What happens to Na+ and K+ when you give Ca++?
Ca++ will block the leaky Na+ channels because Ca++ wants to get into the cell real bad, but its too big to go through there.
ECF Na++ will increase
ECF K++ will decrease and ICF will increase
What does decreased levels of Ca++ in the blood do?
More Na++ going into the cell which will increase the V(rm) = more excitable cell
T/F: Calcium inhibits electrical activity of the cell
T
What happens if you increase your serum K+?
You decrease the concentration gradient
K+ will not leave as fast
Where are 2 places that AP happen?
Motor neuron
Skeletal muscle
Trousseau sign is caused by
Hypocalcemia
Spasms in wrist
Chvostek’s sign is caused by
Hypocalcemia
Spasms in face
What does tetany mean?
involuntary muscle spasms
You can give a _____ bolus for tissues that are too depolarized
Ca++/Mg++
T/F: V-G Na++ channels are clogged by Ca++
F
Only effects leaky channels
Myelin Sheath is a ______ structure that helps send AP ________
Robust
Quickly
How does the diameter of the nerve effect the rate of the AP?
Wider = Faster
More narrow = more resistance = slower
What are the 3 things that affect the rate of an AP?
Length of nerve
Diameter of nerve
Presence of Myelin sheath
How does myelin effect rate of AP?
No myelin = slow
More myelin = faster
How is myelin formed?
Schwann cell nucleus grows overtime and wraps around the neuron in a spiral
As it spirals, the water is squeezed out and it becomes a good insulator.
What does a myelin sheath do?
-Prevents Na+ from being pumped back out during an AP by a Na/K pump
-Allows faster conduction of AP
What is the Nodes of Ranvier?
High density area packed with Lots of fast Na+ channels, Na/K pump, and K+ channels
What is Saltatory conduction?
Jumping from 1 node of renvier to another to spread the AP
What is part of the CNS?
Brain, spinal cord, Cranial nerve 2 (optic nerve)
T/F: Myelin makes cells less prone to ischemia
T
T/F: Myelin adds protection from crush injuries
T
What cell is responsible at producing/maintaining myelin in the CNS?
Oligodendrocytes
What cell is responsible at producing/maintaining myelin in the PNS?
Schwann Cells
Oligodendrocytes are _____ at reproducing myelin
Bad
Oligodendrocytes and Schwann cells are ______ cells
Glial
At what age do you begin to lose myelin?
40
Myelinated neurons are _____
energy efficient
Myelinated cell require _____ anesthesia
More
d/t fast Na+ channels density at the nodes of renvier
If myelin sheath is degraded, what will come back?
Na/K pumps
What happens to the stuff under the myelin sheath?
degraded
What diseases are associated with loss of myelin sheath?
MS, Optic Neuritis, Guillain-Barre
After covid, what disease did we see an increase in regarding loss of myelin sheath?
Gullian- Barre
From covid infection, body generated antibodies that affected the nervous system
Explain whats going on in demyelinating diseases
Since the meylin is degraded or gone Na/K ATP pumps will regenerate
This will make it almost impossible to generate an AP in that area but the Na+ will just get pumped right back out and we will not be able to excite the cell.
How does an electrical synapse gap junction work?
Simple diffusion ion channel
How many connexins make a connexon?
6
Explain cell signaling with electrical synapse gap junctions
fast way to get AP from 1 cell to another
- 6 connexins from a connexon
- 2 connexions connect to form an ion channel (conduits) that allows the passage of small ions
- Gap junction is the area where the connexons meet
Ca++ can go through but its big and it doesnt go well
What area has a decrease in Gap junctions to allow for delays?
Pacing area of the heart
Where are connexions located?
In the cell wall
Which is faster, a chemical or electrical synapse?
Electrical
Fiber classification A:
Heavily myelinated
AP sent fastest
Fiber classification C:
No myelination
Fiber classification B:
Lightly myelinated
If information is need to be sent quickly, what class of fibers would it be sent on?
Class A
What class of fibers are motor neurons under?
Class A
What is another name for a cell body?
Soma
Describe a neuron structure
-Cell body
-Dendrites
-Axon
- Axon Hillock
What is the cell body?
Mostly the decision maker
Has lots of mitochondria
charge -60
What are dendrites?
Receiving end
Recieves info from descending pathways from brain or sensory info from dorsal horn
talks to other neurons
This end is stuck to the anterior horn on the grey matter of the spine
Negatively charged
What is the Axon Hillock?
Has multiple inhibitory connections (GABA receptors which increase Cl permeability)
Supresses overactivity of the CNS
Most negatively charged
What is the Axon?
Area that AP is sent down
Used for signaling
Myelinated
Excitatory connections will make the dendrite area more _____
positive
Inhibitory connections will make the dendrite more_____
negative
Alcohol is a ______ antagonist. It can cause ________
GABA
Seizures
What happens if you remove the inhibitory connections on the axon hillock?
Increase excitability in the nervous system —> seizures
What are Glial cells? what are the 4 kind?
Supporting cells that can divid and replicate
Astrocytes, Ependymal cells, oligodendrocytes, and microglia
What are Astrocytes?
Important in BBB
helps maintain balance in CSF, electrolytes, and pH buffer
connects with endothelial
What is ependymal cells?
Produces and moves CSF with cilia
What is Microglia?
Acts as immune system
degrades dead cells and keeps the area around the CNS clean
What are Oligodendrocytes
Form myelin sheath in the CNS
Schwann cells in PNS
What are the 3 different types of neurons?
Multipolar
Bipolar
Pseudounipolar
Describe Neuron: Multipolar
Decision making
Cell body attached to dendrites
Cell body at top
Cell body sits on top of axon
AP travels down axon
Describe Neuron: Bipolar
Special sensory
Ex) Optic nerve
Dendrites at the top
Cell body in the middle
myelinated axon between dendrites and cell body and cell body and bottom
Describe Neuron: Pseudouipolar
Sensory
Cell body only there to support the structure
Majority of sensory cells outside spinal cord
Decisions made by sensors itself
Feeds in through the posterior/dorsal horn in the grey matter of the spinal cord
What type of neuron is a motor neuron?
Multipolar
