Week 3: Synapses

Question 1

Excitatory Postsynaptic Potential (EPSP)

Answer 1

stimulate axon briefly, slight depolarization in post-synaptic neuron
- not an action potential (doesn’t reach threshold, depolarization decays quick over time/space)
- make action potentials in post synaptic cell more likely

stimulate twice w/ large gap of time = two EPSPs

time interval short enough, second adds to first (temporal summation)

increase frequency and firing rate over spontaneous rate

Question 2

Inhibitory Postsynaptic Potential (IPSP)

Answer 2

input from axon can hyperpolarize postsynaptic cell
- increases negative charge inside, less likely to fire action potential

synaptic input opens K_ channels to leave cell or Cl- to enter cell

decay over time and space, dont travel like action potentials

decrease frequency and firing rate below spontaneous rate

Question 3

Presynaptic Neuron

Answer 3

neuron before/above the synapse
- contains vesicles of NTs

Question 4

Postsynaptic Neuron

Answer 4

neuron after/below the synapse
- contains receptors to recieve message for NTs

Question 5

Reflex Arc

Answer 5

circuit from sensory neuron to muscle response
- sensory neuron senses touch
- excites second neuron (intrinsic neuron)
- intrinsic neuron excites motor neuron
- motor neuron excites muscle

Question 6

Reflexes

Answer 6

automatic muscular response to a stimulus

requires communication between neurons

slower than conduction along an axon

Question 7

Spatial Summation

Answer 7

stimuli that can happen near each other @ same time and have cumulative effect

pinching two points together can lead to reflex when neither point alone does
- pinching activates sensory neurons which feed excitation to spinal neuron
- spinal neuron conmbine input from multiple sensory neurons

depolarizations from different presynaptic neurons add up in a single postsynaptic neuron

Question 8

Spontaneous Firing Rate

Answer 8

the rate at which a neuron produces action potentials (electrical signals) without any external stimulation

Question 9

Synapse

Answer 9

specialized gap between neurons

Question 10

Temporal Summation

Answer 10

repeated stimuli w/in brief time have cumulative effect
- threshold of excitation reached by multiple sub-threshold stimuli timed properly

single pinch on dog’s foot once doesn’t cause reflex, several rapid light pinches do

small depolarizations back-to-back add up

Question 11

Acetylcholine

Answer 11

loss in Alzheimer’s, neuromuscular junction

Question 12

Acetylcholinesterase

Answer 12

enzyme that breaks down acetylcholine, breaks into two parts and sends choline back to presnayptic neuron to be recycled neurotransmitters

Question 13

Amino Acids

Answer 13

component of nearly all NTs, come from diet
- some NTs are related

Question 14

Catecholamines

Answer 14

epinephrine, norepinephrine, dopamine

Question 15

COMT

Answer 15

breaks down dopamine, waste product washes away

catechol-o-methyltranferase

Question 16

Exocytosis

Answer 16

release of a neurotransmitter from presynaptic neuron into synaptic cleft

caused by calcium

Question 17

G Proteins

Answer 17

a family of intracellular signaling proteins that play a crucial role in transmitting signals from cell surface receptors to intracellular effectors.

Question 18

Ionotropic Effects

Answer 18

when NT attaches to receptor, channel opens
- faster, short-term effects
- focal

channels = transmitter-gated/ligand-gated (not volatage)
- when NT binds, channel changes shape, quick effects

can be excitatory or inhibitory

Question 19

Ligand-Gated

Answer 19

a membrane protein that functions as an ion channel, opening to allow specific ions to pass through the cell membrane only when a particular molecule (the ligand) binds to it

Question 20

Metabotropic Effects

Answer 20

neurotransmitter attaches to receptor & bends it, sequence of metabolic reactions starts
- open/close ion channels among other things
- slower/longer last effects
- more widespread

Question 21

Neurotransmitters

Answer 21

chemical, released at synapse, that affects another neuron (most made in presynaptic terminal)
- can be excitatory or inhibitory

glutamate: most plentiful excitatory NT
- learning/memory, excitotoxicity

GABA: typically inhibitory
- some sedatives act on GABA receptors

acteylcholine
- loss in Alzheimer’s, neuromuscular junction

dopamine
- movement, reward

norepinephrine
- mood, arousal, fight/flight

serotonin
- sleep state, mood

Question 22

Reuptake

Answer 22

presynaptic neuron takes up intact molecules
- serotonin & catecholamines have transporters
- transporters (membrane proteins) take up NT intact
- SSRIs: specific serotonin reuptake inhibitors

Question 23

Second Messenger

Answer 23

intracellular signaling molecules that amplify and relay signals from extracellular molecules (first messengers) into the cell

Question 24

Transmitter-Gated

Answer 24

a type of ion channel that opens when a specific chemical signal, or neurotransmitter, binds to it, allowing ions to pass through the cell membrane

Question 25

Transporters

Answer 25

proteins in cell membranes that move ions and molecules, such as neurotransmitters, across the membrane, controlling synaptic transmission and neuron function

Question 26

Vesicles

Answer 26

tiny packets of neurotransmitters allows NTs to be released if: - NT has been made + loaded into vesicles - loaded vesicles dock near release sites - calcium elevated -> vesicles fuse with remebrane releasing NTs into synapse - vesicles recycled

Question 27

Sensory Neuron

Answer 27

a nerve cell in the peripheral nervous system that transmits sensory information from sensory organs and receptors to the central nervous system

Question 28

Intrinsic Neuron

Answer 28

nerve cells that are located within the walls of specific organs, such as the gastrointestinal tract, heart, and bladder

Question 29

Motor Neuron

Answer 29

specialized nerve cells that control muscle movement

Question 30

Inhibition

Answer 30

blocking or supression of something when one set of muscles is excited, different set relaxed

Question 31

Affinity

Answer 31

an innate attraction

Question 32

Efficacy

Answer 32

the ability to produce a desired or intended result

Question 33

Tolerance

Answer 33

a diminished response to a drug that develops with repeated exposure, requiring a larger dose to achieve the same effect

Question 34

Key Terms of Psychopharmacology

Answer 34

affinity, tolerance, etc.

Question 35

Agonists

Answer 35

mimics or increases effects - can bind to receptors, cause more release, block breakdown, etc.

Question 36

Antagonists

Answer 36

blocks transmission - physically block, increase reuptake, break down in synapse, etc.

Question 37

Sherrington's 1st Observation: Reflex Speed

Answer 37

speed of conduction thru reflex arc never more than 15 m/s action potential velocities along sensory and motor neurons = 40 m/s something slows transmission

Question 38

Sherrington's 2nd Observation: Summation

Answer 38

repeated stimuli w/in brief time or over small space have cumulative effect - threshold of excitation can be reached by multiple stimuli if timed properly or close enough

Question 39

Sherrinton's 3rd Observation: Inhibitory Synapses

Answer 39

some messages block neuronal activity - some neurons make action potentials in other cells less likely when they fire action potentials foot pinch causes contraction of some muscles at same time as relaxation of others - relaxation <-- inhibition - best way to keep motor neuron from accidentally firing = inhibit action potentials

Question 40

Otto Lowei

Answer 40

shows nerves stimulate muscle by chemical release through stimulating frog vagus nerve, collecting fluid, and injecting into another frog - something in fluid controls heart rate

Question 41

Chemical Events @ Synapse

Answer 41

neurons make chemicals that serves as NTs action potential at presynaptic terminal lets calcium enter, causes release of neurotransmitter into synaptic cleft released NTs attach to receptors on postsynaptic membrane, alter activity NT separates from receptors, can be taken back to presynaptic or diffuse away some postsynaptic cells send reverse message to control NT release

Question 42

Release and Diffusion of a Neurotransmitter

Answer 42

release - depolarization opens voltage gated calcium channels in presynaptic terminals, calcium enters cell - calcium causes exocytosis - action potentials don't always release NT, amont can vary diffusion - NT diffuses across synaptic cleft (concentration gradient) - small gap = quick diffusion - some NT make it to postsynaptic membrane, attach to a receptor like a lock and key

Question 43

Removing Neurotrnamitters

Answer 43

once job of NT is done, remove it by: - breaking it apart (enzymes like acetylcholinesterase) - taking it back up into presynaptic cell (serotonin/catecholamine transporters)