Anatomy & Anatomy & Physiology IPhysiology IUnit SevenUnit Seven

Nervous System Nervous System FunctionFunction

Sensor

Integrating Center

Effectors

StimulusStimulus ResponsResponsee

Nervous System Nervous System FunctionFunction

Anatomy of the Human Anatomy of the Human Nervous SystemNervous System

Anatomy of the Human Anatomy of the Human Nervous SystemNervous System

Anatomy of the Human Anatomy of the Human Nervous SystemNervous System

Neuron – a nerve cellNeuron – a nerve cellNerve – a bundle of neuron Nerve – a bundle of neuron axons axons wrapped in fibrous wrapped in fibrous connective connective tissuetissueGanglion – a mass of neuron Ganglion – a mass of neuron cell cell bodies found in bodies found in the PNSthe PNS

Anatomy of the Human Anatomy of the Human Nervous SystemNervous System

Neuron Properties and Neuron Properties and ClassesClasses

Neuron properties:Neuron properties: ~ excitability – respond to ~ excitability – respond to stimulistimuli ~ conductivity – sending ~ conductivity – sending electrical electrical impulsesimpulses ~ secretion – release of ~ secretion – release of neurotransmittersneurotransmitters

Neuron Properties and Neuron Properties and ClassesClasses

Neuron classes:Neuron classes: ~ afferent (sensory) ~ afferent (sensory) neuronsneurons * detect a variety of * detect a variety of stimuli and stimuli and send messages to the send messages to the CNSCNS

Neuron Properties and Neuron Properties and ClassesClasses

Neuron classes:Neuron classes: ~ interneurons ~ interneurons * found only in the CNS* found only in the CNS * receive signals from * receive signals from afferent afferent neuronsneurons * carry out integrative * carry out integrative functionsfunctions * approximately 90% of all * approximately 90% of all neuronsneurons

Neuron Properties and Neuron Properties and ClassesClasses

Neuron classes:Neuron classes: ~ efferent (motor) neurons~ efferent (motor) neurons * send messages from * send messages from CNS to CNS to effectors (muscles or effectors (muscles or glands)glands) in response to stimuli in response to stimuli

Neuron Neuron Properties Properties

and and ClassesClasses

NeuroNeuron n

StructStructureure

Neuron StructureNeuron Structure

Neuron StructureNeuron Structure

NeurogliaNeuroglia

Neuroglia - support cells Neuroglia - support cells that aid in the functions of that aid in the functions of neurons neurons > four types are found in > four types are found in the CNSthe CNS * astrocytes* astrocytes * oligodendrocytes* oligodendrocytes * microglia* microglia * ependymal cells* ependymal cells

NeurogliaNeuroglia

NeurogliaNeuroglia

Neuroglia - support cells Neuroglia - support cells that aid in the functions of that aid in the functions of neurons neurons > two types are found in > two types are found in the PNSthe PNS * Schwann cells* Schwann cells * satellite cells* satellite cells

The Neural The Neural SynapseSynapse

A synapse is junction at the A synapse is junction at the end of a neuron axon where it end of a neuron axon where it stimulates another cell by way stimulates another cell by way of chemical messengers called of chemical messengers called neurotransmittersneurotransmitters

The Neural The Neural SynapseSynapse

The most common synapse The most common synapse types are:types are: ~ neural synapse – junction ~ neural synapse – junction between one neuron and between one neuron and anotheranother ~ myoneural synapse – ~ myoneural synapse – junction junction between a neuron and a between a neuron and a muscle cell muscle cell

The Neural The Neural SynapseSynapse

The Neural The Neural SynapseSynapse

Presynaptic Presynaptic membranemembrane Synaptic Synaptic

cleftcleft

Postsynaptic Postsynaptic membranemembrane

The Neural The Neural SynapseSynapse

Neurotransmitters are Neurotransmitters are chemical messengers that are chemical messengers that are released by an axon released by an axon presynaptic membranepresynaptic membraneSome neurotransmitters will Some neurotransmitters will excite postsynaptic excite postsynaptic membranes while others will membranes while others will inhibit theminhibit them

NeurotransmittersNeurotransmitters

Neurotransmitter classes:Neurotransmitter classes: + acetylcholine+ acetylcholine + amino acids+ amino acids + monoamines+ monoamines + neuropeptides+ neuropeptides

NeurotransmittersNeurotransmittersAcetylcholine:Acetylcholine: + released in myoneural + released in myoneural synapses & in most ANS synapses & in most ANS synapses synapses + excites skeletal muscle+ excites skeletal muscle + inhibits cardiac muscle+ inhibits cardiac muscle + excites & inhibits smooth + excites & inhibits smooth muscle and glands muscle and glands depending depending on locationon location

NeurotransmittersNeurotransmittersAmino acids:Amino acids: + four types that excite or + four types that excite or inhibit activity in the CNS inhibit activity in the CNS + excitatory – glutamate + excitatory – glutamate & aspartate& aspartate + inhibitory – glycine & GABA+ inhibitory – glycine & GABA (gamma (gamma aminobutyric aminobutyric acid)acid)

NeurotransmittersNeurotransmitters

Amino acids:Amino acids: + glutamate is the principle + glutamate is the principle excitatory neurotransmitter excitatory neurotransmitter of the brain, while aspartate of the brain, while aspartate is the principle one in the is the principle one in the spinal cordspinal cord

NeurotransmittersNeurotransmitters

Amino acids:Amino acids: + GABA is the most common + GABA is the most common inhibitory neurotransmitter inhibitory neurotransmitter in the brain, while glycine is in the brain, while glycine is the most common in the the most common in the spinal cordspinal cord

NeurotransmittersNeurotransmitters

Monoamines:Monoamines: + found mainly in the brain, + found mainly in the brain, but but also in the spinal cord and also in the spinal cord and ANSANS + can exhibit excitatory or + can exhibit excitatory or inhibitory effects depending inhibitory effects depending on locationon location

NeurotransmittersNeurotransmitters

Monoamines:Monoamines: + catecholamines are a group + catecholamines are a group of of commonly known commonly known monoaminesmonoamines ~ norepinephrine is found ~ norepinephrine is found in the brain, spinal cord & in the brain, spinal cord & ANS causing excitation & ANS causing excitation & inhibitioninhibition

NeurotransmittersNeurotransmitters

Monoamines:Monoamines: + catecholamines are a group + catecholamines are a group of of commonly known commonly known monoaminesmonoamines ~ epinephrine is found ~ epinephrine is found in the brain & spinal cord in the brain & spinal cord causing excitation & causing excitation & inhibitioninhibition

NeurotransmittersNeurotransmitters

Monoamines:Monoamines: + serotonin is found in the + serotonin is found in the CNS CNS and is secreted by plateletsand is secreted by platelets + its effects are usually + its effects are usually excitatoryexcitatory

NeurotransmittersNeurotransmitters

Monoamines:Monoamines: + histamine is found in the + histamine is found in the brain and is secreted by brain and is secreted by basophilsbasophils + its effects are as a potent + its effects are as a potent vasodilatorvasodilator

NeurotransmittersNeurotransmitters

Neuropeptides:Neuropeptides: + found mainly in the CNS, but + found mainly in the CNS, but also in the digestive tractalso in the digestive tract + they are mainly inhibitory in + they are mainly inhibitory in nature, playing major roles nature, playing major roles in in pain suppression and pain suppression and digestiondigestion

NeurotransmittersNeurotransmitters

Neuropeptides:Neuropeptides: + beta endorphin suppresses + beta endorphin suppresses pain and fatiguepain and fatigue + cholecystokinin (CCK) + cholecystokinin (CCK) suppresses appetite and suppresses appetite and aids aids in digestionin digestion

The The Neural Neural SynapsSynaps

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The The Neural Neural SynapsSynaps

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Postsynaptic Postsynaptic ResponseResponse

As has been noted, As has been noted, postsynaptic responses can be postsynaptic responses can be excitatory or inhibitoryexcitatory or inhibitoryNeurotransmitters that elicit an Neurotransmitters that elicit an excitatory response do so by excitatory response do so by producing excitatory producing excitatory postsynaptic potentials (EPSPs)postsynaptic potentials (EPSPs)

Postsynaptic Postsynaptic ResponseResponse

Neurotransmitters that elicit an Neurotransmitters that elicit an inhibitory response do so by inhibitory response do so by producing inhibitory producing inhibitory postsynaptic potentials (IPSPs)postsynaptic potentials (IPSPs)Both EPSPs and IPSPs are Both EPSPs and IPSPs are necessary for proper function in necessary for proper function in the nervous systemthe nervous system

Postsynaptic Postsynaptic ResponseResponse

Postsynaptic Postsynaptic ResponseResponse

Postsynaptic Postsynaptic ResponseResponseSummation is Summation is

the process the process of adding up of adding up postsynaptic postsynaptic potentials & potentials & responding responding to their net to their net effecteffect

Postsynaptic Postsynaptic ResponseResponse

Postsynaptic Postsynaptic ResponseResponse

Summation Summation can occur in can occur in two ways:two ways: ~ temporal~ temporal ~ spatial~ spatial

Postsynaptic Postsynaptic ResponseResponse

Postsynaptic Postsynaptic ResponseResponse

Anesthetics (without Anesthetics (without sensation):sensation): # most work by activating # most work by activating inhibitory receptorsinhibitory receptors # others work by decreasing # others work by decreasing membrane permeability to membrane permeability to NaNa++

Postsynaptic Postsynaptic ResponseResponse

Proprioception is subconscious Proprioception is subconscious perception of the position and perception of the position and movements of the bodymovements of the bodyIt results from the input from It results from the input from proprioceptors (receptors in proprioceptors (receptors in muscles, tendons & joints) and muscles, tendons & joints) and the vestibular apparatus of the the vestibular apparatus of the inner earinner ear