propagation of electrical impulses

list the basic components of electrical and chemical synapsis of the PRE-SYNAPTIC membrane

1. action potential arrives at the axon terminal

2. voltage-gated calcium channels open, allowing calcium to enter the cell

3. calcium triggers the release of neurotransmitters by exocytosis

4. neurotransmitters diffuse across the synaptic cleft

list the basic components of electrical and chemical synapsis of the POST-SYNAPTIC membrane

binding of neurotransmitters open ligand-gated ion channels, leading to generation of graded potentials

what are example organs where electrical synapses contribute to communication between cells?

1. heart

2. brain

3. intestines

what is the general concept of continuous conduction?

action potentials send unidirectional signal along the nerve axon or muscle fiber where the gradient potential will reach the axon hillock

why is it important that the action potential reach the axon hillock?

there are more sodium channels located here, so there is a greater chance of reaching the threshold value and producing an electrical impulse

why is action potential unidirectional?

refractory period

what is the effect of the nerve fiber on action potential?

action potential faster in larger diameter fibers because they have lower electrical resistance

what is myelin?

a glial cell plasma membrane concentrically wrapped around the nerve to create tight insulation

where does interrupted insulation occur?

peripheral nerves

what are rodes of ranvier on an axon?

interrupted intervals on the axon that lack the myelinated sheath

why is action potential considered "salatory"?

action potential rapidly jump from node to node because voltage-gated sodium channels only are expressed at nodes of ranvier

why do we want interrupted insulation of the nerve axon during axon potential?

increases the speed of conduction due to nodes of ranvier

what type of electrical impulse conduction is faster?

saltatory conduction in the myelinated axon

what are electrical synapses?

type of communication between cells through connexons that allow bidirectional flow without the release of neurotransmitters into a synaptic cleft

connexons

gap junctional pores in electrical synapses

what type of synapses allows for bidirectional flow?

electrical synapses

what type of synapses enable coordinated contraction of cardiac muscle cells?

electrical synapses

what is the mechanism of electrical synapses?

1. depolarization of the cell membrane

2. ionic flow into neighboring cell

3. depolarization into next cell, so on

what triggers electrical synapses?

depolarization of cell membrane

chemical synapses

use a neurotransmitter and require calcium

what do chemical synapses require?

calcium

what are the steps of chemical synapses?

1. action potential depolarizes presynaptic membrane

2. voltage-gated calcium ion channels open and diffuse into cytoplasm of cell

3. vesicles fuse with membrane and release neurotransmitter into synaptic cleft (calcium dependent exocytosis)

4. diffusion

5. released neurotransmitter binds to post-synaptic receptor (ligand-gated ion channel)

6. post synaptic sodium channels open (influx sodium, action potential)

7. neurotransmitter is removed from the synaptic cleft, and channel closes

for a neurotransmitter to be removed from the synaptic cleft, what must be removed?

must remove the associated ligand

what is the function of SNARE proteins?

1. increase calcium concentration in terminal button

2. allows exocytosis to occur

botulism causes _ paralysis

flaccid

why does botulism cause flaccid paralysis?

the SNARE protein is broken down meaning that the acetylcholine neurotransmitter will not be released meaning that there will be no signal sent to the muscle to contract

tetanus causes _________ paralysis

spastic