Synapse - November 22

synapse is what?

the site where a neuron makes a connection w/ another neuron or an effector

what is the side that transmits the signal?

an axon terminal of the presynaptic cell

what is the side that receives the signal?

the dendrite of the postsynaptic (back) cell

(neuron or effector)

synapse can either be ..?

electrical or chemical

what is electrical synapse?

the action potential can move directly across since the plasma membranes of the 2 neurons are in direct contact

why can the action potential move directly across in electrical synapse?

since the plasma membranes of the 2 neurons are in direct contact

what does electrical synapse provide?

provides unbroken and rapid transmission but can only receive input from one axon at a time

what is chemical synapse?

the action potential needs to jump across a narrow gap (synaptic cleft) that separates the 2 neurons which requires a neurotransmitter

chemical synapse: whats a synaptic cleft?

a narrow gap that separates the 2 neurons

chemical synapse: time is required for what?

for release, diffusion, and binding of the neurotransmitter

chemical synapse: a neurotransmitter can receive what?

input from hundreds of axon terminals at one time

whats the most common type of synapse?

chemical synapse

conduction across the synapse: where are neurotransmitters found?

in synaptic vesicles

conduction across the synapse: where are synaptic vesicles located?

in the cytosol of axon terminals

when an action potential arrives, what channels open?

Ca2+ channels in the axon open transporting Ca2+ into the neuron

conduction across the synapse: the increase in Ca2+ ions triggers what?

a protein in the membrane of the synaptic vesicle to fuse w the plasma membrane releasing the neurotransmitter into the synaptic cleft

conduction across the synapse: the increase in Ca2+ ions trigger a protein in the membrane of the synaptic vesicle to fuse w the plasma membrane releasing what?

releasing the neurotransmitter into the synaptic cleft

conduction across the synapse: the neurotransmitter diffuses across what?

the cleft

conduction across the synapse: the neurotransmitter diffuses across the cleft and ..?

binds to receptor molecules in the post synaptic membrane

conduction across the synapse: the neurotransmitter diffuses across the cleft and binds to receptor molecules in where?

in the post synaptic membrane

conduction across the synapse: what happens when the neurotransmitter diffuses across the cleft ad binds to receptor molecules in the post synaptic membrane?

opens gated channels to allow ions to flow into the neuron

conduction across the synapse: if this depolarization reaches the threshold, what happens?

then the signal is sent down the next neuron

neurotransmitters: there are how many different substances?

100

neurotransmitters: describe them.

small and diffuse rapidly

neurotransmitters: some have _ effects (1)

stimulatory

neurotransmitters: what are stimulatory effects?

cause the next neuron in a neural circuit to depolarize by becoming more permeable to sodium ions

neurotransmitters: some have _ effects (2)

inhibitory

neurotransmitters: what are inhibitory effects?

cause the next neuron in a neural circuit to hyperpolarize by becoming more permeable to potassium ions

neurotransmitters: as a result of these effects, what happens?

the potential difference increases (-80mV to -90mV) making it harder to reach the threshold value

neurotransmitters: since the potential difference increases, what happens?

it makes it harder to reach the threshold value

what is acetylcholine?

the best known neurotransmitter that triggers muscle contractions, hormone secretion, wakefulness, attentiveness, memory, learning, etc.

whats the best known neurotransmitter?

acetylcholine

what triggers muscle contractions, hormone secretion, wakefulness, attentiveness, memory, learning, etc?

acetylcholine

what is alzheimer’s disease?

is due to a lack of acetylcholine, resulting in a loss of memory, speech and perception

what neurotransmitter causes alzheimers disease?

acetylcholine (lack of)

what are endorphins?

are released during pleasurable experiences and in times of stress, which helps to reduce pain and induce feelings of euphoria

what is dopamine

a neurotransmitter in the brain associated w a reward

motivation system, low doses of dopamine causes parkinsons disease

what causes Parkinson’s Disease?

low doses of dopamine