Afferent Nerves Efferent Nerves

cell body: cell body: central part of cell; contains the nucleus axon: axon: long slender extension from cell body; used to transmit electrical signals axon terminals: axon terminals: branching ends; receives electrical signals and releases chemical signals out of the neuron dendrites: dendrites: branches that receive chemical signals & convert them into electrical signals

Dendrites receive an incoming signal The signals travels along Synapse : Synapse : the gap between neurons the length of the neuron The axon terminals of the pre-synaptic cell deliver the signal to the post-synaptic cell

A neuron is typically at -70mV RESTING POTENTIAL

a positive electrical signal at +35mV ACTION POTENTIAL

time Voltage (mV) -70 mV RESTING POTENTIAL

A transport protein forces ions against their concentration gradients 3 sodium (Na + ) molecules are pushed outside the cell 2 Potassium (K + ) molecules are pushed inside the cell There is a net removal of positive ions (cations) outside the cell; inside of the cell becomes negative RESTING POTENTIAL

time Voltage (mV) -70 mV ACTION POTENTIAL DEPOLARIZATION the inside of the cell changes from -70mV to +35mV

that bind receptors on the dendrites of the post-synaptic cell axon terminals of the pre-synaptic cell through exocytosis NEUROTRANSMITTERS: NEUROTRANSMITTERS: chemical signals sent from the

DEPOLARIZATION The binding of neurotransmitters to the receptors of dendrites triggers the opening of a few Na + channels This causes a slightly positive charge When the charge reaches the threshold (-55mV), many voltage- controlled Na + channels open, causing a flood of positive charges All-or-None Principle

time Voltage (mV) -70 mV ACTION POTENTIAL REPOLARIZATION the cell returns to resting potential; often overshoots this return

REPOLARIZATION As Na + channels close, K + gates open. K + rushes out of the cell, returning to the cell to a -70mV resting potential

As the action potential reaches the axon terminal, neurotransmitters are exocytosed from the neuron and bind to receptors on the next neuron

Select one of the following neurotransmitters and be prepared to share its role with the class Acetylcholine Dopamine Norepinephrine & Epinephrine Serotonin Histamine