Neurophysiology

EXAM 2

reductionist approach

analyzes the biological functions across a descending hierarchy of complexity

action potential

• all or nothing

• magnitude/amplitude is always the SAME

• frequency varies

• carries information through its pattern of occurrence

neuronal activity

movement of ions in and out of a cell, across the semi permeable membrane

• Na (out of cell)

• K (into cell)

resting potential

Na influx out of cell, Na-K pumps to make resting membrane potential

depolarization

ESPC (with summation) causes excitatory behavior to reach the threshold to open the voltage gated sodium channels

• A decrease in membrane potential (making the interior less negative), increasing AP probability.

hyperpolarization

K channels open, letting K to rush out of the cell

• An increase in membrane potential (making the interior more negative), decreasing AP probability.

autoreceptor

presynaptic receptor binding the neurons own neurotransmitter, functioning like a negative feedback brake on further release

axon hillock

specialized place in the cell body that integrates EPSP and IPSP to determine if it reaches threshold for AP

calcium

ion entering the axon terminal to trigger the fusion of the synaptic vesicles and neurotransmitter release

dendritic release

release of neurotransmitters from the dendrites instead of terminals, enables bidirectional flow of information

electrical synapse

gap junction allowing for almost instantaneous signaling between closely opposed neurons

EPSP (excitatory postsynaptic potential)

depolarizing potential

• caused by NA influx

IPSP (inhibitory postsynaptic potential)

hyperpolarizing potential

• caused by Cl influx

myelin

fatty sheath surrounding the axon that accelerates signal transmission

nodes of ranvier

uninsulated gaps in the myelin sheath where the AP is regenerated during saltatory conduction

potassium

inside cation whose efflux repolarizes and hyperpolarizes the neurons

reflex arc

series of neurons mediating automatic responses

• sensory, motor, synapse)

refractory period

around 1 millisecond period where an AP cannot fire

• right after a firing

• ensures one directional flow

• limits firing frequency

reuptake

recycling neurotransmitters back into the presynaptic terminal via specialized transporters

saltatory conduction

rapid jumping of an AP over the nodes on ranvier in myelinated axons

sodium

outside cell cation whose influx generates an AP

spatial summation

integration of multiple inputs arriving at different locations on the neuron

SSRI (selective serotonin reuptake inhibitor)

drug class that blocks serotonin reuptake to treat mood disorders

synaptic vesicle

membrane bound sac in the axon terminal containing neurotransmitters

temporal summation

integration of multiple inputs arriving at the hillock at DIFF TIMES

propagation

regeneration of the AP along the axon

• as one is depolarized, the adjacent one is triggered

poison dart frogs

Secrete toxins that irreversibly open sodium channels, causing lethal paralysis.

scorpions

Venom prevents open sodium channels from closing, leading to over-excitation.

epilepsy

Certain seizure disorders are linked to genetic mutations in sodium channels.

grasshopper mouse

it has evolved sodium channels

• unaffected by scorpion venom, allowing it to prey on scorpions without harm.

5-HT2A

promotes impulsive behavior

5-HT2C

inhibits impulsive behavior

negative feedback loop

autoreceptor acts as a "brake," sensing the high serotonin levels and signaling the neuron to decrease initial serotonin release.

Retrograde Messengers

neurotransmitters like Anandamide (endogenous cannabinoid) or THC are released from dendrites to regulate neurotransmitter release from axon terminals

• This process bypasses the general rule that APs are only generated adjacent to the cell body

  • allowing the postsynaptic cell to communicate "backward" to the presynaptic terminal.