What is a neuron?

The Neuron b A neuron is a nerve cell like any other cell in the bodylike any other cell in the body b Neurons are similar to other cells in the body in some ways b However, neurons differ from other cells in the body in some ways

3 major classes of neurons b Sensory (afferent) b Motor (Efferent) b Interneurons b Glia cells developmentdevelopment housekeepinghousekeeping insulationinsulation protectionprotection

Simple Reflex Pathway

The process of neural communication b Within cells - action potential b Between cells - synaptic transmission b Components: dendrites, soma (cell body), axon, and terminal buttons of axon

The Neuron at Rest b Resting potential - Cell is Polarized b neuron membrane separates charged ions, producing a voltage potential b sodium (NA+), potassium (K+), chloride (Cl-), and protein molecules (A-) b selectively permeable (semi-permeable) b sodium-potassium pump maintains ionic imbalance b inside of neuron is negative relative to outside (about -70mV)

Reception of Input b Graded potentials: Excitatory potentials -depolarizing currentExcitatory potentials -depolarizing current Inhibitory potentials - hyperpolarizing currentInhibitory potentials - hyperpolarizing current b determines which ion channels open Excitatory input causes the ion channels to allow sodium ions into neuronExcitatory input causes the ion channels to allow sodium ions into neuron –allows neuron to fire Inhibitory input causes ion channels to keep neuron negatively chargedInhibitory input causes ion channels to keep neuron negatively charged –prevents neuron from firing

Synaptic Transmission b Presynaptic and postsynaptic neurons b Transmission involves movement of neurotransmitters across synaptic cleft about 200 angstroms (one ten-millionth of a millimeter) in width b/t neuronsabout 200 angstroms (one ten-millionth of a millimeter) in width b/t neurons b Once AP reaches terminal button, vesicles spill contents into gap b Traverse cleft, attach to receptor molecules b Either increase (E) or decrease (I) neural firing

Neurotransmitters b Acetylcholine, ACH learning and memorylearning and memory motor neurons and musclesmotor neurons and muscles major excitatory neurotransmittermajor excitatory neurotransmitter b Gamma-Amino Butyric Acid (GABA) major inhibitory neurotransmittermajor inhibitory neurotransmitter anxietyanxiety

Neurotransmitters b Catecholamines: NorepinephrineNorepinephrine –undersupply - depression DopamineDopamine –oversupply - schizophrenia –undersupply - Parkinson’s b Serotonin mood, sleep, and eatingmood, sleep, and eating b Endorphins natural pain killersnatural pain killers

Neurotransmitters