Module 4 - Nerves Flashcards
1
Q
excitable cells
A
- All neurons and muscle cells are excitable
- Use resting membrane potential to create an electrochemical impulse (action potential)
2
Q
non-excitable cells
A
- Cells that do not generate action potentials
- Most cells in body are non-excitable
3
Q
voltage dependant channels
A
- Movement of ions across membrane (sodium Na+ & potassium K+)
- Sensitive to changes in membrane potential
- Open when cell becomes more positive (depolarization)
- Sodium channels open immediately & close with inactivation gate
- Potassium channels open after brief pause (when sodium enters inactivation period)
4
Q
permeability during action potential
A
- Na+ peaks rapidly
- K+ leave slowly
- Repolarization, K+ leave cell (return to membrane resting potential)
- Depolarization, Na+ enters the cell
5
Q
depolarization in action potential
A
- Membrane potential rapidly changes from resting (-70mV) to (+35mV)
6
Q
repolarization in action potential
A
- After depolarization
- Membrane potential returns to -70mV
7
Q
threshold in action potential
A
- Point that must be reached in depolarization to fire an action potential
- -55mV is considered the standard threshold
8
Q
overshoot in action potential
A
- Peak of action potential where membrane potential is positive
- Between 0mV and the peak of amplitude
9
Q
hyperpolarization in action potential
A
- Membrane potential becomes briefly more negative before returning to resting potential (-90mV)
10
Q
direction of flow of action potential
A
- Specific regions where action potentials can occur (cell body/1st node of ranvier)
- Travels in one direction, towards axon terminal
- Refractory period prohibits flow in backwards direction
11
Q
action potential propagation
A
- Generated on axon hillock
- Travel down nerve to axon terminal
- Movement of action potential down axon
- Current is carried by positively charged ions (Na+)
- From positive to negative areas (unlike charges attract)
12
Q
saltatory conduction
A
- Much faster than unmyelinated nerve fibers (jumping nodes of ranvier)
- Action potential cannot back up
- Channels are closed behind moving action potential (refractory period)
13
Q
all or nothing mentality of action potential
A
- If threshold isn’t reach repolarization returns membrane potential to resting state
- If threshold is reached action potential propagates down axon at full height & size
14
Q
steps of neuromuscular junction
A
- Action potential on presynaptic motor nerve fiber triggers voltage-gated Ca++ ion channels to open
- Ca++ flows into cell, down concentration gradient
- Influx of Ca++ trigger the fusing synaptic vesicles to the membrane
- Release of Ach into synaptic cleft via exocytosis
- Ach diffuses across synaptic cleft & attaches to Ach (ligand) receptors on muscle cells membrane
- Ligand-gated ion channels open
- Lots of Na++ in, few K+ leave
- Triggers local depolarization (end plate potential EPP)
- Depolarization of EPP spreads to adjacent cell membrane
- Voltage gated channels are open (for action potential)
- Allow large amounts of Na+ into muscle cell & trigger action potential
- Ach is broken down into acetic acid & choline by AChe enzyme
- Choline is taken back to axon terminal to be recycled
15
Q
dendrites
A
- receive incoming signals
- increase overall surface area to communicate with more neurone
- thin branching processes of cell body
