PS1090 - synapses, neurotransmitters, hormones

what is a synapse

the gap between pre-synaptic and post-synaptic neurons

name the two types of synapses

electrical and chemical synapse

how do electrical synapses work

direct ion flow through gap junctions (connexons) for very fast transmission

where are electrical synapses common

in reflexes and sensory systems needing speed

what happens in chemical synapses at the axon terminal

action potential opens Ca2+ channels; Ca2+ triggers neurotransmitter release into synaptic cleft

what is an EPSP

excitatory postsynaptic potential: Na+ channels open, causes depolarization

what is an IPSP

inhibitory postsynaptic potential: Cl- channels open, causes hyperpolarization

what is spatial summation

multiple pre-synaptic neurons signal one post-synaptic neuron at once

what is temporal summation

rapid signals from one pre-synaptic neuron to post-synaptic neuron

difference between ionotropic and metabotropic receptors

ionotropic: fast ion channel opening (milliseconds); metabotropic: slower G-protein/second messenger cascades

what are the 5 steps of neurotransmitter lifecycle

synthesized, stored in vesicles, released, binds receptors, removed (reuptake/enzymes)

what do excitatory neurotransmitters do

promote action potential generation

where is serotonin produced (serotonergic system)

raphe nuclei in brainstem; controls mood, sleep, appetite, emotion

how do SSRIs treat depression

block serotonin reuptake, increasing availability in synaptic cleft

where is dopamine produced, and its two main roles

substantia nigra (movement) and VTA (reward); controls voluntary movement and pleasure/reward

why are drugs more addictive than natural rewards

they cause 10x higher dopamine release, hijacking reward system

what is the pituitary gland's role

master gland connected to hypothalamus; releases hormones like oxytocin, vasopressin

what does oxytocin do in behaviour

promotes social bonding, trust, closeness, lactation, uterine contractions

describe the HPA axis stress response

hypothalamus (CRH) → pituitary (ACTH) → adrenal glands (cortisol); negative feedback stops it

effect of chronic stress/PTSD on the brain

high cortisol shrinks hippocampus, reduces neurogenesis, causes premature brain aging