concept 48.4: neurons communicate with other cells at synapses

what happens at electrical synapses

the electrical current flows from one neuron to another through gap junctions

what does a gap junction do

connects cells together and allows ions to flow from the cytoplasm of one cell to its adjacent cell

what occurs at chemical synapses

a chemical messenger- neurotransmitter- carries information between neurons (from presynaptic cell to post- synaptic cell)

most common synapse

chemical synapses

what does the presynaptic neuron do

synthesizes and packages the neurotransmitter in synaptic vesicles located in the synaptic terminal

what causes the release of a neurotransmitter

the action potential causes the relrease by exocytosis

where does the neurotransmitter bind to

a receptor protein found on the plasma membrane of the postsynaptic cell

ligand gated ion channel (aka ionotropic receptor

located at most chemical synapses, the receptor that binds and responds to neurotransmitters

post synaptic potential

when a neurotransmitter binds it causes the ion channels to open and this generates the post synaptic potential

is postsynaptic potential depolarizing or hyperpolarizing

both

what does is mean that postsynaptic potentials are graded potentials

is enough postsynaptic potentials depolarize the axon hillock of the postsynaptic neuron to threshold, an action potential will be created

what could happen to a neurotransmitter after exocytosis

it can diffuse out of the synaptic cleft, it can be taken up by surrounding cells, it can be degraded by enzymes

how does cocaine work

it prevents the uptake of dopamine

how many neurotransmitters are they in how many groups

over 100 neurotransmitters groups into 5 groups

how many receptors can a single neurotransmitter bind to

over a dozen

can a neurotransmitter excite and inhibit different cells at the same time

yes

when does receptor activation and postsynaptic response cease

when neurotransmitters are cleared from the synaptic cleft

what does the effect of a neurotransmitter depend on

it depends on the postsynaptic cell

acetylcholine

common neurotransmitter involved in muscle stimulation, memory formation, and learning, and can be inhibited by many toxins

amino acid neurotransmitters

include glutamate (stimulatory), glycine (inhibitory), and gamma amino butyric acid (GABA) (inhibitory)

biogenic amines

include dopamine, epinephrine, norepinephrine, serotonin

neuropeptides

short chains of amino acids that include substance P and endorphins (affecting our perception of pain

gases

(NO and CO) are PNS local regulators, generated on demand