5c. Nervous System Physiology

What generates an action potential?

Ion movement

What leads to the release of neurotransmitters?

Action potentials

What are neurotransmitters?

Chemicals that relay messages from neurons

What creates a negative internal environment in a neuron?

NA-K pump

What happens when inside and outside of cells have different charges?

The membrane becomes polarized

How is K+ concentrated in ICF?

High

How is Ka+ concentrated in ECF?

Low

What is the concentration of Na+ in ICF?

Low

What is the concentration of Na+ in ECF?

High

What is the concentration of proteins in ICF?

Higher

What is the concentration of protein in ECF?

Where is the difference of charge in a cell?

Immediately on either side of the membrane

What is membrane potential?

The charge difference in the cell membrane

What is resting membrane potential?

The potential difference across the cell membrane in an unstimulated cell

What is the approximate resting membrane potential?

-70mV

Which side of the cell membrane is more negative?

The inside

What is resting membrane potential established by?

Unequal distribution of Na and K ions, negatively charge protein ions, exit of K ions due to leak channels

What is moved by the Na-K pump?

3 Na ions out of cell, 2 K ions into cell

What builds chemical and electrical gradients?

Na-K pump

What is depolarizing?

The decrease in charge difference of membrane potential

What is hyperpolarizing?

The increase in charge difference to membrane potential

What is repolarization?

When depolarization is followed by a return to a polarized state

What causes changes in membrane potential?

Ion channels

Which channels open and close due to binding of a molecule?

Ligand-gated channels

What channels open and close in response to pressure?

Mechanically-gated channels

What channels open and close in response to changes in electrical potential?

Voltage-gated channels

What channels are always open or randomly open and close?

Leak channels

What are graded potentials?

Small changes in resting membrane potential that vary in size

What cause graded potentials?

Mechanically-gated and ligand-gated channels

Where do graded potentials occur?

Along dendrites and cell body

What enters the neuron in a graded potential?

Na ions

When does depolarization occur in graded potentials?

When the inside of a neuron becomes more positively charged

What is summation?

When smaller graded potentials add together

Which way does depolarization move membrane potential?

Towards the threshold

Which way does hyperpolarization move graded potentials?

Away from the threshold

What happens when threshold is reached?

Action potential is guaranteed to move down axon

What is the value of the threshold?

-55mV

What are the types of graded potentials?

Excitatory postsynaptic potential and inhibitory postsynaptic potential

What does excitatory postsynaptic potential do?

Moves membrane toward threshold, depolarizes membrane

What does inhibitory postsynaptic potential do?

Moves membrane away from threshold, hyperpolarizes membrane

What are the 2 types of summation?

Spatial and temporal summation

What is spatial summation?

Graded potentials occurring at several different synapses over a short period of time

What is temporal summation?

Graded potentials occurring at one synapse over a short period of time

Where does the axon potential begin?

At the axon hillock and travels to the axon terminals

What are refractory periods?

The time during and after an action potential occurs when another cannot occur

What is absolute refractory period?

When it is absolutely unlikely for an action potential to occur

What is relative refractory period?

When it is relatively unlikely for an action potential to occur

How do action potentials move in an unmyelinated axon?

Continuous conduction, like a wave

How do action potentials move in a myelinated axon?

Saltatory conduction, like jumping

What stops an action potential from going backwards?

Refractory period

What influences the speed of action potentials?

Myelination, size of electrochemical gradient, axon diameter

What are synapses?

Areas where neurons communicate

What are the 2 types of synapses?

Chemical and electrical synapses

What are chemical synapses?

Synapses that release neurotransmitters

What are electrical synapses?

Synapse with direct connections that ions use to move from one cell to another

What type of synapses are more common in the body?

Electrical synapses

What are the components of a chemical synapse?

Presynaptic cell, neurotransmitter, synaptic cleft, receptors for neurotransmitter, postsynaptic cell, system for cleaning out synapse

What are the 3 ways neurotransmitters are cleared from a synapse?

Diffusion, reuptake, breakdown

What does removal method for of a neurotransmitter depend on?

The neurotransmitter or synapse

What are regulatory neurons?

Neurons that facilitate or inhibit activities of presynaptic neuron