Action Potential and Synaptic Cleft

Neutral

In a resting neuron, cells in the body are not electrically...

There is a difference in charge

A "potential" is at work in a cell because

On the outside

Where is sodium located in the cell?

On the inside

Where is potassium located in the cell?

higher to lower concentration

Diffusion always occurs from

Outside the cell

Where does potassium want to go?

Inside the cell

Where does sodium want to go?

proteins embedded in the membrane

What serves a role in membrane channels?

Open (leaky) channels: non-gated

Potassium leaks through easily, sodium leaky channels are more narrow

Gated channels

open or close in response to a stimulus, chemically gated (ligand) channels

voltage gated channels

Closed at rest opens with action potential, response to change in membrane potential

mechanically gated channels

open in response to physical deformation of the receptor

concentration gradient

Movement of ions from area of high to low concentration

electrical gradient

attraction between opposite charges or repulsion of like charges

Internal and external concentrations of electrolytes

What creates a difference in electrical potential (voltage) across a plasma membrane?

membrane potential

The difference in electric charge between the inside, and the outside of a cell caused by a difference in the distribution of ions

-70 mV

Resting potential

resting potential

The membrane potential of living cell at rest. In nerve cells at rest the interior is negative to the exterior.

action potential

Changes where all the gates open (threshold), reversal of resting membrane potential, rapid change in voltage across membrane

It leaves an unbalanced charge

What happens when K+ leaks out of the cell

-55 mV (threshold) = depolarization

What value has to be achieved to start action potential?

"Pumps"

Active transport mechanisms are collectively called?

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

sodium-potassium pump

3 Na+ out, 2 K+ in, forces ions to go against their gradient

electrostatic force

anions and cations have opposite charges and attract eachother by the means of _______________

sodium-potassium pump

It maintains concentrations of ions and other substances needed by living cells in the face of the passive movement

initial segment (axon hillock)

Where do action potentials begin?

Receptors: Stimulus, post synaptic: neurotransmitter

What are action potentials triggered by?

True

T or F: any stimulus that changes membrane potential to threshold, will cause an action potential, all action potentials are the same, no matter how large the stimulus

Depolarization

Decrease in membrane potential, inside of membrane becomes less negative than resting membrane potential. probability of producing impulse increases.

Hyperpolarization

an increase in the membrane potential of a cell, probability of producing impulse decreases, far away from threshold

Hyperpolarization

Number is so negative around -90 MV, triggers gated channels to close. Leaky channels and sodium potassium pump brings number back to -70 MV.

Neurotransmitters

chemical messengers that cross the synaptic gaps between neurons

Acetylcholine, dopamine, serotonin

Examples of neurotransmitters

Voltage-gated Ca2+ channels open and allow Ca 2+ to enter the cell

What happens when the presynaptic membrane is depolarized?

Calcium

Found all over but mostly outside but very slightly inside the cell, activates neurotransmitters

Neurotransmitters

Are the "language" of the nervous system Can be excitatory or inhibitory

True

T or F: The calcium entry causes synaptic vesicles to fuse with the membrane and release neurotransmitter molecules into synaptic cleft

It binds to ligand-gated ion channels (receptor proteins) in the post synaptic membrane

What happens after the neurotransmitter diffuses across the synaptic cleft?

False

T or F: neurotransmitters enters the next cell

Depolarization (excitatory effect) or hyper polarized (inhibitory effect) of the post synaptic neuron

What happens after the neurotransmitters bind to ligand-gated channels?

Acetylcholine

A neurotransmitter that enables learning and memory and also triggers muscle contraction

NMJ (neuromuscular junction)

Stimulates all skeletal muscles

So the postsynaptic membrane can reset and be ready to receive another signal

Why does the neurotransmitter need to be removed from the synaptic cleft?

It can just diffuse away, it can be degraded by enzymes, it can be recycled by the presynaptic neuron

What are the three ways that neurotransmitters can be removed from synaptic cleft?

Reuptake

neurotransmitter's brought back to cell recycled, packed up

Acetylcholinesterase

enzyme that breaks down acetylcholine

Agonist

mimics the action of a neurotransmitter at receptor site

Meds for Parkinson's, low levels of dopamine

Example of agonists

Antagonist

Block the activity of a neurotransmitter at the receptor

antipsychotic drugs, block the receptors, bind without activating

Example of antagonist

re-uptake inhibitors

Medications prevent unused neurotransmitters from being transported back into cell

SSRI - depression and anxiety, serotonin stays in the synapse, strengthens the effect

Example of re-up take inhibitors