Synapse; Nervous System cont.

synapse

region where a neuron transfers into another neuron, muscle or gland

presynaptic neuron

first neuron, axon terminal

postsynaptic neuron

second neuron

what is the postsynaptic neuron usually?

Usually dendrites, but can be axon or soma in CNS

What are the types of synapses?

Axodendritic, axosomatic, axoaxonic

Where are two places synapses occurs?

neuron to neuron in CNS & neuromuscular junction

Neuromuscular junction

Acetylcholine (Ach) is neurotransmitter causes muscle impulse instead of another nerve impulse.

Neuromuscular junction is the same as…

Neuron to neuron synapse

Synaptic cleft

space between presynaptic & postsynaptic matrix, filled with matrix

Synaptic vesicle

in the axon terminal, contain neurotransmitters

Neurotransmitters

Proteins used to communicate with postsynaptic membrane, synthesized in soma

Protein channels

on post synaptic membrane, facilitated ion diffusion

What is the first synaptic transmission step?

action potential reaches axon terminal of presynaptic neuron

What is the second synaptic transmission step?

depolarization opens Ca++ gates on presynaptic membrane, Ca++ diffuses into presynaptic neuron

What is the third synaptic transmission step?

Ca++ signals neurotransmitter release, synaptic vesicles fuse with membrane and dump contents

What is the fourth synaptic transmission step?

neurotransmitters bind to receptor on post synaptic membrane

What is the fifth synaptic transmission step?

binding of neurotransmitters opens channels so ions can diffuse

What is the sixth synaptic transmission step?

Reuptake of neurotransmitters, neurotransmitters are reclaimed into presynaptic vesicles AND/OR neurotransmitter is denatured by an enzyme

EPSP/ Excitatory postsynaptic potential

neurotransmitter causes Na+ gates to open, depolarization of postsynaptic membrane occurs.

IPSP

Inhibitory post synaptic potential, neurotransmitters causes CI- gates to open, post synaptic membrane becomes more negative (hyper polarized), prevents nerve impulse in post synaptic membrane.

How much neurons can a neuron synapse with?

1-100,000 neurons

What does the sum of all EPSP’s and IPSP’s determine?

If nerve impulse results in postsynaptic neuron

What is a nerve impluse converted to at synapse?

a chemical

What is a nerve impulse converted to at postsynaptic membrane?

an electrical