Neural Structure and Neural Communication

Soma

Cell body of a neuron

Dendrites

extensions from soma that receive signals

Myelin Sheath

A layer of fatty tissue segmentally encasing the axon = insulation = faster signal transmissions

Terminal Buttons

The endpoint of a neuron where neurotransmitters are stored.

Axon

Long, thin fiber that transmits signals away from the soma towards terminal

Action Potential

A rapid change in the membrane potential of the neuron caused by the movement of ions.

Refractory Period

The membrane potential is hyperpolarized, making it less likely to trigger another action potential. Thru K+ flowing out of cell

resting membrane potential

-70mV

Depolarization

process that makes the membrane potential less negative by Na+ ions flowing into cell

Threshold of Excitation

The level of stimulation required to trigger a neural impulse (-50mV)

Synapse

A junction where information is transmitted from one neuron to the next.

Synaptic Cleft

Space between neurons

Neurotransmitters

chemicals that transmit signals across a chemical synapse; bind to receptors on the post-synaptic neuron.

Endocytosis

reabsorption of neurotransmitters into the presynaptic neuron for recycling

excitatory postsynaptic potentials (EPSPs)

depolarize the postsynaptic cell membrane = increases likelihood that an action potential will be triggered in post

• primary neurotransmitter is glutamate

Inhibitory postsynaptic potentials (IPSPs)

hyperpolarize the postsynaptic cell membrane =decreases likelihood that an action potential will be triggered

• primary neurotransmitter is Gamma aminobutyric acid (GAA)

Neural Integration

Combined effect of EPSPs and IPSPs. A neuron can simultaneously receive both excitatory and inhibitory inputs = only fires when excitatory inputs sufficiently greater than inhibitory

Agonists

Mimic natural compounds and activates receptor to create same effect as natural compound but often with much more significant response

Antagonist

Block the receptor and prevent the natural compound from activating it.

action potential pathway

1. Na+ channels open = Na+ ions enters = depolarisation

2. depolarisation past -50mV = K+ channels open = K+ ions leave but Na+ still entering

3. reaches peak = +40mV = Na+ channels close until back at resting potential

4. K+ ions continue to exit = increasingly negative charge

5. once returned to resting potential K+ channels close and Na+ reset

action of neurotransmitters at receptors

lock and key model = each receptor activated by only one neurotransmitter. When neurotransmitter binds receptor undergoes specific function e.g. opening ion channel