Physiology 4: Neurophysiology Flashcards
What is a transmembrane potential?
Unequal charges across the membrane
What is the range of the resting potential?
-10 mV to -100 mV (depending on cell type)
Which ion is responsible for “turning the cell off”? And by which mechanism does it keep this cell negative?
Cell is turned off/negative by K+ moving out of the cell. Specifically via the Na+/K+ pump, which pumps 3 Na+ out and 2 K+ in.
How is the cell turned on?
Na+ enters the cell and makes the charge positive (depolarization)
Which ion is responsible for turning on a cardiac pacemaker cell?
Ca+2
List the ions associated with the 4 classes of anti-arrhythmic drugs
- Class I: Na+
- Class II: beta
- Class III: K+
- Class IV: Ca+2
What is the function of class III anti-arrhythmic drugs?
Class III anti-arrhythmic drugs target K+ and blocks phase 3 (when K+ normally leaves the cell) of the action potential
What is the function of class IV anti-arrhythmic drugs?
Class IV anti-arrhythmic drugs target Ca+2 and slows down the heartrate by delaying the firing of pacemaker action potentials
What is the function of class II anti-arrhythmic drugs?
Class II anti-arrhythmic drugs target beta receptors, which decreases the contractility of the heart
What is the function of class I anti-arrhythmic drugs?
Class I anti-arrhythmic drugs target Na+, which delays the depolarization and slows down firing of action potentials to cardiac myocytes
What happens in phase 1 of cardiac myocyte action potentials?
Rapid depolarization. Caused by Na+ entry.
What happens in phase 2 of cardiac myocyte action potentials?
The plateau. Caused by Ca+2 entry.
What happens in phase 3 of cardiac myocyte action potentials?
Repolarization. Caused by K+ loss.
Which ion is responsible for the resting potential and repolarization?
Resting potential: K+ in
repolarization: K+ out
Which ion is responible for depolarization?
Na+ in
What is the shape of a typical nerve action potential?
What is the shape fo the action potential you seen in the SA or AV node?
What is the shape of the aciton potential you see in cardiac muscle cells?
What is a neuroglia (glial cell)?
Cells that support and protect neurons
What is the difference between a depolarizing agent and a nondepolarizing agent?
Depolarizing agent: overstimulates ACh receptor, which causes the receptor to become fatigued and no longer contract
Nondepolarizing agent: blocks the ACh receptors so it is unable to deploarize
The PNS has which 3 types of cells? (Think O-AME has GaSS, call the COPS)
- Ganglia
- Satellite cells
- Schwann cells
The CNS has which 3 types of cells? (Think O-AME has GaSS, call the COPS)
- Oligodendrocytes
- Astrocytes
- Microglia
- Ependymal cells
Function of ependymal cells:
- Form epithelium (ependyma)
- Line central canal of spinal cord & ventricles in brain
- secrete/monitor/circulate CSF
- contain stem cells for repair
Function of astrocytes:
- Maintain blood brain barrier
- Repair damaged neural tissues
Function of oligodendrocytes:
- Myelination, which speed up action potentials
Difference between white matter and gray matter
- White matter: myelination
- Gray matter: unmyelination
Function of microglia
Clean up cellular debris, waste prodcuts, pathogens
What is ganglia?
Masses of neuron cell bodies
Function of satellite cells
Surround ganglia and regulate environment around neuron
Function of Schwann cells
Form myelin sheaths - **many Schwann cells sheath one axon **
Difference between graded potential and action potential
Graded potential: temporary localized changes in resting potential that varies in magnitude
- caused by stimulus
- decreases over time
Action potential: all or none electrical impulse produced by graded potential
- must reach threshold to overcome
- signal does not decrease
What happens during an absolute refractory period vs a relative refractory period
Absolute refractory period: Na+ channels open or close -> no action potential possible
Relative refractory period: membrane potential is almost normal -> very large stimulus can initiate action potential
What are the 2 methods of action potential propagation?
- Continuous propagation - in unmyelinated axons
- Saltatory propagation - in myelinated axons
Difference between excitatory postsynaptic potential (EPSP) and inhibitory postsynaptic potention (IPSP)
- Excitatory postsynaptic potential (EPSP): graded depolarization
- Inhibitory postsynaptic potention (IPSP): graded hyperpolarization
How are neurons inhibited through IPSP?
The neuron that receives many IPSPs is inhibited because the stimulation needed to reach threshold is increased
2 types of summation:
- Temporal
- Spatial
What affects the speed of action potential propagation?
V = MD
V = velocity
M = myelination
D = diameter
What are the properties of norepinephrine (NE):
- Excitatory (depolarizing) effect
- In brain & autonomic nervous system
What are the properties of dopamine?
- Excitatory or inhibitory
- CNS
- Involved in Parkinson’s & cocaine use
What does serotonin do and where is it found (CNS vs PNS)?
- affects attention/emotional states
- CNS
What are the properties of Gamma Aminobutyric Acid (GABA)?
- Inhibitory
- CNS
- Functions not well understood
What are cholinergic synapses?
- synapse that releases ACh
- all neuron-to-neuron synapses in PNS
- many in CNS as well
- all neuromuscular/neuroglandular junctions in PNS
Difference between Type A fibers vs Type C fibers
Type A fibers:
- myelinated ( -> fast speed)
- large diameter ( -> fast speed)
- carries rapid info to/from CNS
Type C fibers:
- unmyelinated ( -> slow speed)
- small diameter ( -> slow speed)
- involuntary muscle, gland control
