Concept Map 8 by Sophie Gregoretti

key

gregoretti668 — 2023-10-22 23:48:43 UTC

blue = lecture
green = reading
yellow = article

history

gregoretti668 — 2023-10-22 23:49:46 UTC

Fritsch and Hitzig (mid 19th century)

gregoretti668 — 2023-10-22 23:55:03 UTC

- electrical stimulation of the neocortex of dogs causes movement (arms & legs)

Caton (early 19th century)

gregoretti668 — 2023-10-23 00:12:58 UTC

- measure electrical currents of brain w voltmeters and electrodes on the skull

Hermann von Helmholtz (19th cent)

gregoretti668 — 2023-10-23 00:14:02 UTC

- determined speed that electricity travels through a nerve

action potentials

gregoretti668 — 2023-10-23 00:14:13 UTC

neuron communication

gregoretti668 — 2023-10-23 00:15:21 UTC

wave of stimulation passing from neuron to neuron

hyperpolarization

gregoretti668 — 2023-10-23 00:17:00 UTC

- charge difference increases
- charge gets more negative
- inward flow of Cl- and outward flow of K+

depolarization

gregoretti668 — 2023-10-23 00:18:16 UTC

- charge diff decreases
- charge gets more positive
- inward flow of Na+

gregoretti668 — 2023-10-23 00:18:41 UTC

gregoretti668 — 2023-10-23 00:19:40 UTC

action potential

gregoretti668 — 2023-10-23 00:20:49 UTC

- brief reversal in polarity of an axon
- 1ms long

threshold potential

gregoretti668 — 2023-10-23 00:22:31 UTC

- voltage on neural (resting) membrane at which an action potential is triggered
- opening of Na+ and K+ voltage sensitive channels
- approximately -40 mV relative to extracellular surround

voltage-sensitive ion channels

gregoretti668 — 2023-10-23 00:23:54 UTC

Na+ channels are more sensitive than K+ --> opens sooner to changes in membrane voltages

gregoretti668 — 2023-10-23 00:31:01 UTC

depolarization due to Na+ influx
- when tetrodotoxin blocks sodium channels, a slightly different action potential only from efflux of K+ is recorded

hyperpolarization due to K+ efflux
- when TEA surrounds the axon (blocks K+ channels), a smaller-than-normal action potential due to Na+ influx is recorded

refractory periods

gregoretti668 — 2023-10-23 00:34:27 UTC

absolute refractory period
- state of an axon while repolarizing when a new AP cannot be elicited because gate 2 of Na+ channels is closed
>> during flush, toilet can't be flushed again

relative refractory period
- state of an axon in the later phase of an AP when increased electrical current is required to produce another AP
- K+ channels still open
>> when the bowl is refilling, toilet can be flushed again but its harder

saltatory conduction and the myelin sheath

gregoretti668 — 2023-10-23 00:41:33 UTC

- axon is insulated by myelin produced by:

> CNS: oligodendroglia

> PNS: Schwann cells

- node of Ranvier: myelin sheath segments seerated by a gap

myelin sheaths

gregoretti668 — 2023-10-23 00:45:09 UTC

- no Na+ channels under myelin sheaths
- Na+ ions that started action potentials at hillock diffuse to node of Ranvier where action potential is regenerated in a flowing action down the axon to the presynaptic area

EPSPs and IPSPs

gregoretti668 — 2023-10-23 00:45:31 UTC

excitatory postsynaptic potential (EPSP)

gregoretti668 — 2023-10-23 00:47:29 UTC

- brief depolarization of a neuron membrane in response to stimulation
- neuron is more likely to produce an AP

inhibitory postsynaptic potential (IPSP)

gregoretti668 — 2023-10-23 00:48:11 UTC

- brief hyperpolarization of a neuron membrane in response to stimulation
- neuron is less likely to produce an AP

gregoretti668 — 2023-10-23 00:49:18 UTC

only last milliseconds before resting potential is restored

gregoretti668 — 2023-10-23 00:49:42 UTC

associated with opening Na+ channels --> influx of Na+

gregoretti668 — 2023-10-23 00:50:34 UTC

associated with opening K+ channels --> efflux of K+
associated with opening of Cl- channels --> influx of Cl-

summation of inputs

gregoretti668 — 2023-10-23 00:54:52 UTC

gregoretti668 — 2023-10-23 00:55:18 UTC

add EPSPs and IPSPs to produce an AP

temporal summation

gregoretti668 — 2023-10-23 00:56:05 UTC

pulses that occur at approximately the same time in a membrane are summed

spatial summation

gregoretti668 — 2023-10-23 00:56:37 UTC

pulses that occur at approximately the same location on a membrane are summed

gregoretti668 — 2023-10-23 01:01:40 UTC

if summed ionic inputs exceed threshold (approx -50mV) at axon hillock, AP initiated

Galvani (18th century)

gregoretti668 — 2023-10-24 14:03:23 UTC

electrical current applied to frog leg nerve --> stimulated movement

gregoretti668 — 2023-10-24 14:08:47 UTC

- first experimented in pt w hole in her skull from cancer

- larger voltages caused seizures

EEG

gregoretti668 — 2023-10-24 14:11:35 UTC

clinical diagnostic tool tp record electrical brain activity

>> for sleep disorders and seizure disorder (like epilepsy)

!!! spike = action potential

gregoretti668 — 2023-10-24 14:14:55 UTC

for experiments

gregoretti668 — 2023-10-24 14:33:31 UTC

don't use in a live animal bc the animal will die

culture neurons, then you can use tetrodotoxin in the solution bath the neuron is in --> blocks Na+ channels functions, so only the K+ channels will be working and you can study its function

gregoretti668 — 2023-10-24 20:22:45 UTC

gregoretti668 — 2023-10-24 20:25:26 UTC

many diff receptors types that open and close channels, or sets of channels depending on ions concentrations
electrical history of the neuron impacts how likely an AP is

all or none

gregoretti668 — 2023-10-24 20:28:11 UTC

once an AP has begin, it will be completed

spike trains

gregoretti668 — 2023-10-24 20:28:42 UTC

sequence of spikes that create bytes of info

in rising phase

gregoretti668 — 2023-10-24 20:30:40 UTC

increased Na+ channel permeability allows AP to occur

gregoretti668 — 2023-10-24 20:35:10 UTC

channels can be inactivated which also contributes to membrane voltage changes

gregoretti668 — 2023-10-24 20:37:01 UTC

the AP is the point at which one more Na+ entering the cell will trigger regenerative NA conductance OR one more K+ leaving the cell will cause a resting potential

gregoretti668 — 2023-10-24 20:38:50 UTC

refractory periods limit the rate neurons can fire APs

gregoretti668 — 2023-10-24 20:40:37 UTC

gregoretti668 — 2023-10-24 20:41:45 UTC

during absolute refractory period: Na+ channels are inactivated, so no amt of depolarizing current can trigger an AP

Na+ channel inactivation is the root cause of the absolute refractory period

gregoretti668 — 2023-10-24 20:42:47 UTC

the absolute refractory period ends when enough Na+ channels leave the inactivated state upon repolarization of the membrane potential

gregoretti668 — 2023-10-24 20:43:48 UTC

LSD

gregoretti668 — 2023-10-26 00:38:02 UTC

serotonergic psychedelic

anxiolytic and antidepressant properties

variables being studied

gregoretti668 — 2023-10-26 00:40:17 UTC

study anxiety-like behaviors, cortical dendritic spines, and 5HT neurons activity originating in the dorsal raphe nucleus (DRN)

animal model

gregoretti668 — 2023-10-26 00:40:47 UTC

male mice exposed to chronic restraint stress

results

gregoretti668 — 2023-10-26 00:53:43 UTC

no anxiolytic or antidepressant effect in non-stressed mice

prevented stress-induced anxiety-like behavior
prevented stress-induced decrease cortical spine density
decreased firing og 5HT neurons, but repeated LSD increased basal firing rate and restored the low 5 HT firitng induced by stress
decreased inhibitory response of 5HT neurons to microiontophoretic applications of 5HT agonist (8-OH-DPAT)

gregoretti668 — 2023-10-26 00:55:31 UTC

LSD prevents anxiety-like behaviors associated w chronic stress
np effects on nonstressed mice
increased spinogenesis
enhancement of 5HT neurotransmission which might be bc of 5HT receptor desensititization

acute LSD treatment DOESNT have anxiolytic or antidepressant effect

gregoretti668 — 2023-10-26 01:02:09 UTC

all of these are not significant!!

reduced 5HT DRN firing activity

gregoretti668 — 2023-10-26 01:21:56 UTC

gregoretti668 — 2023-10-26 01:23:12 UTC

microiontophoretic ejection of increasing 8-OH-DPAT currents show significant difference in the response of 5HT DRN neurons when treated w LSD

gregoretti668 — 2023-10-26 14:10:21 UTC

measured the validity of LSD dosage w degree of head twitch response, 30 and 60 had highest head twitch response

REPEATED LSD treatment has anxiolytic effect

gregoretti668 — 2023-10-26 14:12:42 UTC