Neuron PhysiologyNeuron Physiology

Nervous System Organization

Nervous System Organization

CNS - Brain and spinal cordPNS - Nerves and Receptors

Somatic Autonomic - sympathetic and

parasympatheticEnteric - GI tract

CNS - Brain and spinal cordPNS - Nerves and Receptors

Somatic Autonomic - sympathetic and

parasympatheticEnteric - GI tract

Cells in Nervous TissueCells in Nervous Tissue

Glial cells - support cells (Schwann cells, Oligodendrocytes, Astrocytes, etc.)

NeuronsStructural - Multipolar, Bipolar,

UnipolarFunctional - Sensory, Motor,

Interneuron

Glial cells - support cells (Schwann cells, Oligodendrocytes, Astrocytes, etc.)

NeuronsStructural - Multipolar, Bipolar,

UnipolarFunctional - Sensory, Motor,

Interneuron

NeurogliaSmaller than neurons5-50x more numerousCan multiply and divideDo not send action potentials

NeurogliaAstrocytes – Blood-brain barrier, may help

form synapses, chemical balanceOligodendrocytes – Myelin sheaths in CNSMicroglia – PhagocytesEpendymal Cells – Produce and circulate

CSF, Blood-CSF barrierSchwann Cells – Myelin sheaths in PNSSatellite Cells – Structural support and

exchange with cell bodies in PNS

Most of Brain and spinal cord

Retina, inner ear,Olfactory area inbrain

Sensory neurons

Electrical signalsElectrical signals

Graded potentials - short distanceAction potentials - short and longGraded ActionMembrane potential called resting

membrane potential in excitable cells

Ion flow = electric current

Graded potentials - short distanceAction potentials - short and longGraded ActionMembrane potential called resting

membrane potential in excitable cells

Ion flow = electric current

Ion ChannelsIon Channels

Leakage channelVoltage-gated channelLigand-gated channel (direct

or indirect)Mechanically-gated channel

Leakage channelVoltage-gated channelLigand-gated channel (direct

or indirect)Mechanically-gated channel

Action potentialsAction potentials

Myelination

PropagationPropagation

Graded vs. Action potentials

Graded vs. Action potentials

Dendrites/Cell bodyLigand-gated/Mech-

gated channelsLocalizedVariable amplitudeLonger durationHyper- or

depolarizingNo refractory

period

Dendrites/Cell bodyLigand-gated/Mech-

gated channelsLocalizedVariable amplitudeLonger durationHyper- or

depolarizingNo refractory

period

AxonVoltage-gated

channelsPropagatedAll or nothingShorter durationDepolarizing then

repolarizingRefractory

AxonVoltage-gated

channelsPropagatedAll or nothingShorter durationDepolarizing then

repolarizingRefractory

Graded Action

SynapsesSynapses

Postsynaptic potentialsPostsynaptic potentials

Excitatory (EPSP)DepolarizationAction potential easier to generate

Inhibitory (IPSP)HyperpolarizationAction potential more difficult

(membrane more negative than usual)

Excitatory (EPSP)DepolarizationAction potential easier to generate

Inhibitory (IPSP)HyperpolarizationAction potential more difficult

(membrane more negative than usual)

SummationSummation

Integration of multiple inputs at trigger zone

Spatial - Multiple presynaptic neurons simultaneously

Temporal - Rapid and repeated stimulation from single presynaptic neuron

EPSPs Threshold Action potentialEPSPs Threshold Partial depolarizationInhibitory Excitatory = Hyperpolarization

Integration of multiple inputs at trigger zone

Spatial - Multiple presynaptic neurons simultaneously

Temporal - Rapid and repeated stimulation from single presynaptic neuron

EPSPs Threshold Action potentialEPSPs Threshold Partial depolarizationInhibitory Excitatory = Hyperpolarization

NeurotransmittersNeurotransmitters

Effects modified by stimulating or inhibiting:SynthesisReleaseReceptor availabilityRemoval

Effects modified by stimulating or inhibiting:SynthesisReleaseReceptor availabilityRemoval

Neurotransmitter RemovalNeurotransmitter Removal

Diffusion away from receptors

Enzyme degradationUptake via

neurotransmitter transporters

Diffusion away from receptors

Enzyme degradationUptake via

neurotransmitter transporters

Neural circuitsNeural circuits

Functional groups of neuronsTypes:

Simple seriesDivergingConverging

Functional groups of neuronsTypes:

Simple seriesDivergingConverging

Gray and White MatterWhite matter =

myelinated axonsGray matter =

everything else!Unmyelinated

axonsCell bodies and

dendritesNeuroglia

Contrast:Ganglion – Collection of cell bodies

in PNSNuclei – Collection of cell bodies in

CNS

Tract – Bundles of axons in CNSNerve – Bundles of axons in PNS

Nerves

Spinal Cord

Brain

Cerebrospinal fluid (CSF)Composition:

Glucose, proteins, lactic acid, urea, ions, some WBCs

Choroid plexuses and ependymal cellsProtects from mechanical and

chemical damageCirculates between ventricles and

through subarachnoid space

CerebrumLateralized into hemispheresCortex – outer gray matter

Gyri – foldsSulci and fissures – grooves between gyri

White matterTracts between hemispheres, within the same

hemisphere and between cerebrum and lower structures

Cerebrum

CerebrumLobes:

Frontal – primary motor area, Broca’s area, Prefrontal cortex (mood, intellect, logic, personality, etc.)

Parietal – Primary somatosensory area, gustation

Temporal – Primary auditory area, olfaction

Occipital – Primary visual areaInsula

Lateralization

Basal Ganglia

•Regulates initiation and termination of movements•Input from cortex, output to motor area•Parkinson’s disease

Cerebellum

•Coordination of movements•Posture and balance•Corpora quadrigemina (coliculi)

DiencephelonThalamus – Relay for sensory

information; nuclei for movement control

Epithalamus – pineal gland; emotional response to smells

Hypothalamus – Controls ANS and pituitary; homeostasis; hormone production; body rhythms and behavioral patterns

Brain StemMedulla oblongata – Relays information to and from brain; Reticular formation; Cardiovascular and respiratory centers

Pons – Relay between cerebellar hemispheres; areas for breathing regulation

Autonomic Nervous System

What does it do?

• Regulation of smooth muscle, cardiac muscle and many glands

• Involuntary• Sympathetic and

parasympathetic

Dual Innervation

• Most organs receive innervation from both sympathetic and parasympathetic

• Autonomic tone = balance between divisions (regulated by hypothalamus)

Sympathetic responses

• E situations (Exercise, emergency, excitement, embarrassment)

• “Fight or flight” response includes:– Pupil dilation– Airway dilation– Increase in cardiac output and

blood pressure– Reduced blood flow to kidney

and GI tract– Increased blood flow to skeletal

and cardiac muscle, liver, and adipose tissue

– Increase in blood glucose level• Longer lasting and more

widespread effects than parasympathetic

Parasympathetic

responses• “Rest and digest”• SLUDD

– Salivation– Lacrimation– Urination– Digestion– Defecation

• Decreases in:– Heart rate– Airway diameter– Pupil diameter