Lecture Exam 2Lecture Exam 2Material represented from chapters Material represented from chapters corresponding to corresponding to ALLALL Nervous System Nervous System PhysiologyPhysiology

Nervous System Physiology: Nervous System Physiology: – Intro., Resting Membrane Potential Intro., Resting Membrane Potential Ch. 5 (156-162)Ch. 5 (156-162)– Nerve Impulse Conduction Nerve Impulse Conduction Ch. 8Ch. 8 – Central Nervous Sys. (Functional Regions) Central Nervous Sys. (Functional Regions) Ch. 9Ch. 9– Sensory Physiology Sensory Physiology Ch. 10Ch. 10 – Peripheral Nervous Sys. (ANS & SNS) Peripheral Nervous Sys. (ANS & SNS) Ch. 11Ch. 11

Stop at Muscle Physiology. Stop at Muscle Physiology.

Chapter 10Chapter 10

Sensory PhysiologySensory Physiology

Perception and Sensation Perception and Sensation

PerceptionPerception = = interpretation of interpretation of sensation, sensation, utilizing regions utilizing regions of the brainof the brain

Sensation = Sensation = conscience conscience awareness of a awareness of a stimulus event stimulus event detected by detected by sensory sensory receptorsreceptors

Figure 10-4: Sensory pathways

Sensory Receptor TypesSensory Receptor TypesChemoreceptorsChemoreceptors– Respond to Respond to

chemical ligandschemical ligands

MechanoreceptorsMechanoreceptors– Respond to various Respond to various

forms of forms of mechanical NRGmechanical NRG

PhotoreceptorsPhotoreceptors– Respond to lightRespond to light

ThermoreceptorsThermoreceptors– Respond to Respond to

temperaturetemperature

NociceptorsNociceptors– Respond to painRespond to pain

Figure 10-1: Sensory receptors

Sensory Transduction Converts Sensory Transduction Converts Stimuli into Graded PotentialsStimuli into Graded Potentials

Transduction = conversion of stimulus NRG into info..that can be Transduction = conversion of stimulus NRG into info..that can be processed by the nervous systemprocessed by the nervous system

Adequate stimulus = NRG form to which receptors respond Adequate stimulus = NRG form to which receptors respond – i.e. light, temp., pain, mechanical NRG, ect.)i.e. light, temp., pain, mechanical NRG, ect.)

Threshold stimulus = the minimum stimulus required to activate a Threshold stimulus = the minimum stimulus required to activate a receptorreceptor

Generator potentialGenerator potential– = graded potentials whose amplitude is proportional to the = graded potentials whose amplitude is proportional to the

strength of the stimulusstrength of the stimulusI.E. stronger stimulus, stronger generator potentialI.E. stronger stimulus, stronger generator potential

If generator potential reaches threshold, it initiates an action If generator potential reaches threshold, it initiates an action potential that travels along the sensory neuron to the CNSpotential that travels along the sensory neuron to the CNS

Sensory AdaptationSensory Adaptation= reduction in sensitivity in the presence of a = reduction in sensitivity in the presence of a constant stimulus caused by a decreased constant stimulus caused by a decreased generator potential thus causing a generator potential thus causing a decreased decreased number of action potentials per secondnumber of action potentials per second sent over sent over the sensory neuron the sensory neuron decreased perception of decreased perception of sensationsensation

Phasic receptors Phasic receptors rapidly adapting rapidly adapting

Tonic receptors Tonic receptors slow adapting or do not adapt slow adapting or do not adapt

Pain, vision, & proprioception DO NOT adaptPain, vision, & proprioception DO NOT adapt

Receptive Fields of NeuronsReceptive Fields of NeuronsFig. 10-2 Receptor fields of sensory neurons

Convergence of primary sensory neurons allows simultaneous subthreshold stimuli to sum at the secondary sensory neuron and initiate an action potential.

Convergence of primary sensory neurons allows simultaneous, subthreshold stimuli to sum at the secondary sensory neuron & initiate an action potential.

Two-Point DiscriminationTwo-Point Discrimination

Figure 10-3: Two-point discrimination

Somatic PathwaysSomatic PathwaysFigure 10-9: Sensory pathways cross the body’s midline

Somatic Senses Somatic Senses Figure 10-10: The somatosensory cortex

Free nerve endingsFree nerve endings

Cold receptorsCold receptors– detect detect lossloss of heat (stimuli of heat (stimuli belowbelow body temp.) body temp.)

Warm receptorsWarm receptors– detect detect gaingain of heat (stimuli of heat (stimuli aboveabove body temp.) body temp.)

Pain receptorsPain receptors

TemperatureTemperature

NociceptorsNociceptors

Fast painFast pain– sharp, & localizedsharp, & localized– transmitted via alpha-delta (myelinated) fiberstransmitted via alpha-delta (myelinated) fibers

Slow painSlow pain– Duller, more diffuseDuller, more diffuse– Transmitted via C (unmyelinated) fibersTransmitted via C (unmyelinated) fibers

PainPain

Referred PainReferred Pain

Figure 10-13: Referred pain

Chapter 11Chapter 11

Efferent Division : Autonomic Efferent Division : Autonomic (ANS) and Somatic Motor Control (ANS) and Somatic Motor Control

(SNS)(SNS)(Control of Body Systems)(Control of Body Systems)

Autonomic Division: Homeostatic balancingAutonomic Division: Homeostatic balancing

ControlsControls– Smooth & cardiac Smooth & cardiac

muscle muscle – Glands & adiposeGlands & adipose

Antagonistic branchesAntagonistic branches– ParasympatheticParasympathetic

"Rest & digest""Rest & digest"

Restore bodyRestore body

– SympatheticSympathetic““Fright, fight, or flight"Fright, fight, or flight"

Energetic actionEnergetic action

Figure 11-1: Homeostasis and the autonomic division

Autonomic Pathways: Communicate to BodyAutonomic Pathways: Communicate to Body

Figure 11-2: The hypothalamus and brain stem initiate autonomic, endocrine, and behavioral responses

Coordinates Coordinates homeostatic homeostatic responsesresponses– Autonomic Autonomic – Endocrine Endocrine – Behavioral Behavioral

Blood pressureBlood pressureOsmolarityOsmolarityTonic regulationTonic regulationAntagonistic Antagonistic controlcontrolReceptor directed Receptor directed responseresponse

HypothalamusHypothalamus– Water balanceWater balance– TemperatureTemperature– HungerHunger

PonsPons– RespirationRespiration– CardiacCardiac– VasoconstrictionVasoconstriction

MedullaMedulla– RespirationRespiration

Autonomic Control CentersAutonomic Control Centers

Figure 11-3: Autonomic control centers in the brain

Preganglionic Preganglionic neuronneuron– ShortShort– Origin: spinal cordOrigin: spinal cord– NT: cholinergicNT: cholinergic (ACh) (ACh)

GangliaGanglia– Sympathetic chainSympathetic chain– Near spinal cordNear spinal cord– Nicotinic ReceptorNicotinic Receptor

Postganglionic Postganglionic neuronneuron– LongLong– NT: adrenergicNT: adrenergic (NE) (NE)

Comparison of Sympathetic PathwaysComparison of Sympathetic Pathways

Figure 11-7: Sympathetic and parasympathetic pathways

Comparison of Parasympathetic PathwaysComparison of Parasympathetic Pathways

Figure 11-7: Sympathetic and parasympathetic pathways

Preganglionic Preganglionic neuronsneurons– Originate inOriginate in

Brain stemBrain stem

Lower cordLower cord

– NT: cholinergicNT: cholinergic (ACh) (ACh)

GanglionGanglion– Near targetNear target– Nicotinic receptorsNicotinic receptors

Postganglionic Postganglionic neuronneuron– NT: cholinergicNT: cholinergic (ACh) (ACh)

Figure 11-5: Autonomic sympathetic and parasympathetic pathways

VaricositiesVaricosities

NT released to NT released to ECFECF

No cleftNo cleft

ImpactImpact– Large areaLarge area– Slow actingSlow acting– Long durationLong duration

Synapses in Autonomic NervesSynapses in Autonomic Nerves

Figure 11-8: Varicosities of autonomic neurons

Acetylcholine synthesis & recyclingAcetylcholine synthesis & recycling

Figure 8-21: Synthesis and recycling of acetylcholine at the synapse

Norepinephrine Release and RecyclingNorepinephrine Release and Recycling

Figure 11-9: Norepinephrine release at a varicosity of a sympathetic neuron

Autonomic Neurotransmitters

Sympathetic Division Parasympathetic Division

Neurotransmitter Norepinephrine Acetylcholine

Synthesized (made) from

Tyrosine Acetyl CoA + choline

Inactivated by (ENZ) Monoamine oxidase (MAO)

Acetylcholinesterase AChE

ENZ location in Mitochondria of varicosity Synaptic cleft

Varicosity of reuptake Norepinephrine Choline

*Varicosity = swollen regions along autonomic axons that store and release neurotransmitters.

Table 8-4-1: Major Neurocrines

Adrenal Medulla: Adrenal Medulla: A Modified Sympathetic GanglionA Modified Sympathetic Ganglion

Figure 11-10: The adrenal medulla

Sympathetic Sympathetic stimulationstimulation– Catecholamine Catecholamine

release to bloodrelease to bloodEpinephrineEpinephrine

NorepinephrineNorepinephrine

– Travel to:Travel to:Multiple targetsMultiple targets

Distant targetsDistant targets

Receptor Found In Sensitivity Second Messenger

1 Most sympathetic target tissue NE > E Activates phospolipase C

2 Gastrointestinal tract & pancreas NE > E Inhibits cAMP

1 Heart muscle, kidney NE = E Activates cAMP

2 Certain blood vessels and smooth muscle of some organs

E > NE Activates cAMP

NE = Norepinephrine (neurotransmitter) E = Epinephrine (hormone from adrenal medulla)

SENSITIVITY OF PERIPHERAL ADRENERGIC RECEPTORS

TO CATECHOLAMINES

Norepinephrine

1 receptor 2 receptor

Activates Phospholipase

Reduces/Inhibits cAMP levels

Release of Ca+2

Smooth muscle contraction & gland secretion

Smooth muscle relaxation & decrease in

gland secretion

Alpha Receptor Stimulation

Epinephrine

Beta Receptor Stimulation

Activation of adenylate cyclase

cAMP

1 Receptor 2 Receptor

Stimulation of metabolism, cardiac muscle stimulation

Inhibition and relaxation of smooth muscle

in respiratory passageways and in blood vessels

of skeletal muscles

Receptor Agonists (mimics) Antagonists (blockers) Indirect Agonists/Antagonists

Cholinergic Acetylcholine AChE* inhibitors: neostigmine; parathionInhibits ACh release: botulinus toxin

Muscarinic

Muscarine Atropine; scopolamine

Nicotinic Nicotine -bungarotoxin (muscle only), tetraethylammonium (TEA) (ganglia only), curare

Adrenergic Norepinerphrine; Epinephrine

Stimulates NE release: ephedrine, amphediminesPrevents NE uptake: cocaine

Pheylephrine “alpha-blockers”

Isopreterenol “beta-blockers”; propranolol (1 &

2); metoprolol (1 only)

*AChE = acetylcholinesterae

Review of Efferent Pathways: Motor & AutonomicReview of Efferent Pathways: Motor & Autonomic

Figure 11-11: Summary of efferent pathways

COMPARISION OF SNS & ANS

SOMATIC AUTONOMIC

Number of neurons in efferent pathway

1 2

Neurotransmitter/receptor at neuron-target synapse

ACh (nicotinic) ACh (muscarinic) or NE ( or )

Target tissue Skeletal Muscle Smooth and cardiac muscle; some endocrine and exocrine glands; some adipose tissue

Structure of axon terminal regions

Boutons Boutons and varicosities

Effects on target tissue Excitatory only: muscle contracts

Excitatory or Inhibitory

Peripheral components found outside the CNS

Axons only Preganglionic axons, ganglia, postganglionic neurons

Summary of function Posture and movement Visceral function, including movement in internal organs & secretion; control of metabolism

Body movementBody movement

AppendagesAppendages

LocomotionLocomotion

Single neuron Single neuron – CNS originCNS origin– MyelinatedMyelinated

Terminus Terminus – BranchesBranches– Neuromuscular Neuromuscular

junctionjunction

Somatic Motor Division: Controls Skeletal Somatic Motor Division: Controls Skeletal MusclesMuscles

Figure 11-11: Summary of efferent pathways

Neuromuscular Junction: OverviewNeuromuscular Junction: Overview

Figure 11-12: Anatomy of the neuromuscular junction

Terminal Terminal boutonsboutons

Synaptic cleftSynaptic cleft– MatrixMatrix– AChEAChE– Hold togetherHold together

End motor plateEnd motor plate– On muscleOn muscle– Nicotinic Nicotinic

receptorsreceptors

Neuromuscular Junction: Neuromuscular Junction: Mechanism of Signal ConductionMechanism of Signal Conduction

Figure 11-13: Events at the neuromuscular junction

Axon terminalAxon terminal– AP signalsAP signals– ACh releaseACh release

Motor end plateMotor end plate– 2 ACh bind2 ACh bind– opens cation opens cation

channelchannel– Na+ influxNa+ influx– Membrane Membrane

depolarizeddepolarized

Stimulates fiber Stimulates fiber contractioncontraction

Autonomic branches: Autonomic branches: sympathetic and parasympathetic sympathetic and parasympathetic – Regulate glands, smooth & cardiac musclesRegulate glands, smooth & cardiac muscles– Team with endocrine to regulate homeostasis Team with endocrine to regulate homeostasis – Are regulated by hypothalamus, pons & medullaAre regulated by hypothalamus, pons & medulla– Have pathways with 2 neurons and a ganglionHave pathways with 2 neurons and a ganglion– Use varicosities to release NTs Use varicosities to release NTs – Have diverse receptors: tonic & antagonistic Have diverse receptors: tonic & antagonistic

regulationregulation

SummarySummary

Somatic ControlSomatic Control

Efferent motor neurons control skeletal Efferent motor neurons control skeletal musclesmuscles– Single long myelinated neuron from CNS Single long myelinated neuron from CNS – Neuromuscular junction structure & Neuromuscular junction structure &

mechanismmechanism

SummarySummary