Lecture 6; 9/6 Flashcards
Beginning of test 2
Define: Polarization
A difference in electrical charge on the inside and outside of cell
Are cells polarized at rest?
Yes
What is the charge of a resting cell?
about negative 80
-80
What happens to the charge of the cell during an AP? What is this called?
Becomes more positive
Depolarization: Happens when the cell is turned on
Cell becomes less polar
What happens when a cell is hyperpolarized?
Cell becomes more polar
Requires more stimulus to fire an AP
More difficult to excite
When polarity of the cell dips under the resting membrane potential
What is repolarization?
Return to normal V(rm) from depolarized state (AP)
Becoming more negative after an AP
More positive means
Less negative
Slow Ca++ channels need repolarization of _______ in order to function properly
Na+ channels
You can have another AP with repolarizing.
No.
What is V-G Ca++ channels called?
L-type channels
What can block the L-type channels?
DHP (hydropyridine Ca++ channel blockers)
K+ is ____ times more permable than Na+ in a resting cell
10
Cl- makes the inside of the cell more ____
Negative
In finding EMF, what do we have to know?
Relative permeability of each ion that the cell is permeable to
What ion plays an important role in the nervous system?
Cl-
What role does Cl- play in the nervous system?
Cl- permeability is adjusted to hyperpolarize the cell to suppress electrical activity in excitable cells
What do GABA receptors do?
Open Cl- channels in neurons to allow Cl- to flood in to make the cell more negative to supress electrical activity.
How does an AP spread?
2 way process: Outward if theres enough room
1 way process: It may only spread in one way if AP is generated at end of cell (depolarization takes longer)
The cell repolarizes in the _____ direction that it depolarizes
Same
Explain positive feedback in regards to V-G Na+ channels
The AP being generated causes the 1st V-G Na+ channel to open. That 1 change is then amplied causing a bunch of them to open until the cell is repolarized.
Neurons that are specialized in communicating to skeletal muscle
Motor neurons
Each skeletal muscle fiber has at least ___ motor neurons
1
What happens when a motor neuron is activated?
It produces an AP down the myelinated axon
What is released from the end of motor neuron after an AP?
Neurotransmitter… Ach…
What is the target/receiving cell called?
Post synapse
What is the sending cell called?
Pre synapse
Where are neurotransmitters released
Neuromuscular junction
Where do paralytics work?
At the NMJ
What does NMJ mean?
Neuromuscular Junction
What does smoking cigarettes do?
Causes excess nicotine can cause release in Ach which can cause tremors/shakiness
Besides Na+, what other ion can go into via nAch-R on the skeletal muscle and depolarize it.
Ca++
T/F: Binding sites on the nAch-R need to be binded one at a time to work.
F
What is close to the nAch-R?
Fast Na+ channels
What is a nAch-R?
Nicotinic Acetylcholine receptor
Negatively-charged ion pore that when simultaneously bound, open up and allow Na+ to flood into a cell
What happens when a nAch-R is simultaneously bound?
They open for about 1ms
Na+ floods in (Ca+/K+ out)
Na+ activates fast Na+ channels which is the very beginning of an action potential
Where does the motor neuron and skeletal muscle meet?
NMJ
What type of ion does nAch-R repel?
Negatively charged ions
What does mAch-R mean?
muscarinic Acetylcholine receptor
Where are mAch-R located?
On the SA and AV node smooth muscle of the heart and the lungs
Where is the SA and AV node?
On left side
On top of the septum
How does electrical current flow through the heart
SA node - Atrias - AV node - ventricles
What nerve specializes in talking to the heart and comes in contact with the SA and AV nodes?
The Vagus nerve
L Vagus talks to SA
R Vagus talks to AV
What type of receptor is the mAch-R?
GPCR
What happens when an Acetylcholine binds to a mAch-R in the heart?
It activates the receptor
the Alpha amino acid is released and goes to activate the nearby K+ channel where K+ can flood out the cell causing the cell to become more negative.
What is normal heart for this class?
70-72 bpm
What happens with vagal stimulus?
HR decreases.
K+ permeability increase
Pacemaker cells are hyperpolarized
What do Antimuscarinic drugs do?
Increase HR
drug binds to receptor and blocks it.
K+ stays inside the cell keepig it more positive. Making it easier to fire an AP
* When K leaves out of the cell, it becomes more negative making it more difficult to fire an AP
Describe a heart beat
- Vagus nerve stimulated and releases Ach
- Ach binds to the mAch-R
- The alpha amino acid opens K+ channels to allow K+ to flood out the cell
- Cell is hyperpolarized and ready for next beat
a little hyperpolarized is good/ok for the heart
If heart wasn’t being influenced by nervous system, how fast would it beat?
110 bpm
What is atropine?
An Antimuscarinic drug
Increases HR
Physical pressure can turn a motor neuron on?
Yes
Describe how physical pressure can turn on a motor neuron.
Pressure sentive Na+ channels widen when flattened and generate an AP but up the motor neuron for processing.
