Physiology Department

neuronNeuron-the Basic Functional Unit

Dendrites: Receives input Soma: integrate inputs and generate action potentials

axon : axon hillock initial segment axon terminalsconvey outputA motor neuron www.botany.uwc.ac.za/sci_ed/ grade10/mammal/nervous.htm

http://www.hsu.edu/faculty/langlet/lectures/Biological_Foundations/brain_parts/fig2_1.gif

Classification of neurons

Conduction of nerve fiberIntegralityIsolationBidirectionRelative indefatigability

synapses

synapseClassificationStructureSignal transmissionPostsynaptic potentialInhibition and facilitationCharacters

Classification of Synapsessoma

Structure of a synapseStructureCa2+receptor

Signal transmission

Postsynaptic potentialExcitatory postsynaptic potential:

Depolarizes the postsynaptic membraneChemically gated cation channels are opened-especially sodium ionsCloser to threshold

Excitatory postsynaptic potential

Postsynaptic potentialInhibition postsynaptic potential:

Hyperpolarizes the postsynaptic membraneChemically gated chloride and potassium channels are opened-especially potassium ionsFarther from threshold

Inhibition postsynaptic potential

Postsynaptic potential

Spatial summation Temporal summation

A threshold or a supra-threshold EPSP spreads to the initial segment of the axon and triggers one or more nerve impulse.

Inhibition and facilitation

Postsynaptic inhibitionPresynaptic inhibitionPresynaptic facilitation

Postsynaptic inhibitionAfferent collateral inhibitionRecurrent inhibition

Afferent collateral inhibition

Recurrent inhibition

Presynaptic inhibition and facilitation

Characters of synapseOne directionDelaySummationImpulse frequency changeSensitive to internal environment and fatigue easily

Neurotransmitter and receptorNeurotransmitter: Chemicals that act as messengers between cells in the brain and nervous system; they transmit impulses across the gap from a neuron to another neuron, a muscle, or a gland.

NeurotransmitterIdentification:Synthesized in the presynaptic cellBinds with receptor and causes special effect; the effect can be mimicked by adding the substance from outsideInactivated by some enzyme or other waysSpecial agonist and antagonist

ReceptorReceptor:A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific physiologic effect in the cell.

ReceptorCharacteristics:1. Specificity2. Saturation3. Reversibility

receptorsWe have known about the receptor as below:Isoforms---subtypeNegative feedback---presynaptic receptorTwo type of families---Coupling with-chemical gated channel or G-proteinHomologous and heterologous desensitization

ligandLigand:A small molecule binds to a particular large molecule.

ligandAgonist:a substance capable of combining with receptors to initiate an action that can be known in advanceAntagonist:One agent that opposes or fights the action of another.

Acetylcholine

AcetylcholineSynthesis: choline + Acetyl coenzyme A + (choline acetyltransferase) ACh + coenzyme AClearance:ACh acetylcholinesterase (AChE) acetate+choline(reuptaken)

Location of the acetylcholinenicotinic receptors found at neuromuscular junction

both nicotinic and muscarinic receptors are found at peripheral autonomic ganglia.

The postganglionic neurons of the parasympathetic nervous system and some of the postanglionic neurons of the sympathetic nervous system.

Location of acetylcholine in the brain

Receptors of acetylcholineM-receptors:Effecors of most parasympathetic postganglionic fiber and some sympathetic postganglionic fiberN-receptors:Postsynaptic membrane of autonomic ganglia neuronsEnd plate membrane of the nerve-muscle junction

AcetylcholineReceptor agonists antagonists Ach-R carbamylcholineNicotinic nicotine curare N1 hexamethonium N2 succinylcholine muscarinic muscarine atropine pilocarpine scopolamine

Nicotinic Acetylcholine Receptor

NorepinephrineSynthesis:

Norepinephrine Varicosities

Location of norepinephrine

Alpha-adrenergic receptorAlpha-adrenergic stimulation results in:vasoconstriction uterine contraction pupillary dilation inhibition of insulin secretion in response to glucose load stimulation of apocrine sweating in the axillary areas intestinal smooth muscle relaxation - this occurs in response to both alpha- and beta-adrenergic stimulation

Beta-1 receptorBeta-1 stimulation causes inotropy and chronotropy, which if filling is maintained, improves cardiac output.Conduction is enhanced.

Beta-2 receptorBeta-2 stimulation systemically causes arteriolar vasodilatation, which reduces resistance to ejection, and thus improves the cardiac output. It also improves chronotropy.Beta-2 receptor agonists have an action both on bronchial smooth muscle cells and mast cells, resulting in bronchodilation and decreased cellular release of inflammatory mediators.

Receptor of adrenalinAlpha (a1 and a2) and Beta (b1 and b2) receptors. All operate via 2nd messenger systems. a1 receptors affect Ca2+ channels (mostly postsynaptic). a2 receptors are mostly presynaptic (but are also postsynaptic) and affect K+ channels (inhibitory). Beta receptors affect K+ channels, and are also mostly inhibitory.

Norepinephrine- Adrenergic synapse agonist antagonista, b- epinephrinea- norepinephrine phentolaminea1 phenylephrine prazosina2 yohimbineb- isoprenaline propranololb1 dobutamine practololb2 Albuterol butoxamine

serotonin

dopamine

Histamine and enkephlins

Reflexa direct connection between stimulus and response, which does not require conscious thought.

Unconditioned reflex: an automatic instinctive unlearned reaction to a stimulus under the level of cortexConditioned reflex:

Reflex arcBasic components:ReceptorAfferent nerveCentral nervous systemEfferent nerveeffector

Neuron circuitDiverging circuit - presynaptic neuron stimulates several postsynaptic neurons (many downstream)Converging circuit - several presynaptic neurons stimulate a single postsynaptic neuronOscillating circuit - stimulation of one presynaptic neuron results in several postsynaptic impulsesParallel after-discharge circuit - one presynaptic neuron stimulates series of neurons, ending on a common postsynaptic neuron

Reflex arcThe Monosynaptic Stretch Reflex (tendon reflex)The Polysynaptic stretch reflex

Neuron circuits

Feedback of the reflexReceptor CNS effector

Sensory AnalysisNervous system2

Sensory pathway1998-2003 Jacob L. Driesen, Ph.D.

Nuclei of the ThalamusThalamus: relay sensory information from lower centers to the cerebral cortex.

Nuclei of the Thalamus:Sensory relay nucleiCommunication nuclei, Intralaminar nuclei

Sensory projection system specific non-specificspecific, point to point common pathway, dispersioncause to specific sense maintain and change and nerve impulses the excitability

Sensory area of the cerebral cortexSomatic sensory area (primary sensory area or general sensory area): postcentral gyrus of each parietal lobeSomatic sensory area

Somatic sensory area Receive sensory information from the opposite side of the bodyThe head is represented in the most lateral portion,and the lower part of the body is represented mediallyThe sizes of these area are directly proportional to the number of specialized sensory receptors in each respective peripheral area of the body.

Sensory area of the cerebral cortexPrimary motor cortex: proprioceptionVisceral sensePrimary visual areaPrimary auditory areaPrimary gustatory areaPrimary olfactory area

Somatic and visceral senseMechanical senseProprioceptionThermal sensepain

painFast pain and slow painfast pain:is felt within about 0.1 second after a pain stimulus is appliedSharp, acute, electric and prickingSlow pain:Begins only after 1 second or more and then increases slowly over many seconds and sometimes even minutesSlow burning, nauseous, aching, throbbing and chronic pain

painReceptors and pathwayPrimary and secondary hyperalgesiaPain in the deep tissue or organVisceral pain and referred pain

referred painThe pain initiated in one of the visceral organs referred to an area on the body surface.

referred pain

Mechanism: converging and facilitated doctrine

State of brain activitySleep and arousalNervous system3

Evoked cortical potentialrapid fluctuations of voltage between parts of the cerebral cortex that are detectable with an electroencephalograph.

ALPHA WAVEthe normal brainwave in the electroencephalogram of a person who is awake but relaxed; occurs with a frequency of 8-12 hertz

BETA WAVEthe normal brainwave in the encephalogram of a person who is awake and alert; occurs with a frequency between 12 and 30 hertz

DELTA WAVEthe normal brainwave in the encephalogram of a person in deep dreamless sleep; occurs with high voltage and low frequency (1 to 4 hertz)

THETA WAVEthe normal brainwave in the encephalogram of a person who is awake but relaxed and drowsy; occurs with low frequency and low amplitude

ELECTROENCEPHALOGRAM

Mechanism of state of brain activityManagement of arousal: Reticular activating system

Acetylcholineserotonine

Mechanism of sleepAscending inhibitory systemAscending activating systemActive process

Stage of sleepSlow wave sleepFast wave sleep (paradoxical sleep; rapid eye movements)

Stage of sleep

The Nervous System Control of Motor FunctionSpinal Cord, Brain Stem, Basal Ganglia,cerebellum, CortexNervous system4

Classification of the axonswww.marcpickcreations.com

Motor neuron in the spinal cord and motor unitAlpha, belta and gama neuronMotor unit: a alpha neuron and the muscle fibers directly controlled by the alpha neuron.

Spinal Cord--spinal shock--Spinal cord reflexesSpinal Cord

Spinal Shock when the spinal cord is suddenly transected in the upper neck, essentially all cord functions, including the cord reflexes, immediately become depressed to the point of total silence.Spinal Cord

Symptoms of the Spinal ShockUnder the transection:1.decline of the arterial blood pressure2.block of the skeletal muscle reflexes integrated in the spinal cordsome required again, stretch reflexes, flexor reflexes, postural antigravity reflexes, and remnants of stepping reflexes; some become hyperexcitable3.suppression of the sacral reflexes for control of bladder and colon evacuationrecover laterSpinal Cord- Spinal Shock

WHY?Loss of the continual tonic excitation by discharges of nerve fibers entering the cord from higher center, particularly discharges transmitted through the reticulospinal tracts, vestibulospinal tracts, and corticospinal tracts.Spinal Cord- Spinal Shock

Spinal Cord ReflexesStretch reflexes (myotatic reflexes):reflex contraction of a muscle when it is pulled.Tendon reflexesMuscle tonusSpinal Cord

Tendon reflexesPulling tendon rapidlyReceptor-muscle spindledorsal root anterior horn (motor neurons) effector-muscleMonosynaptic pathwaymuscle spindle: detect muscle lengthSpinal Cord

Tendon reflexesSpinal Cord

Muscle TonusPulling tendon slowlyReceptor-muscle spindlespinal cord effector-musclepolysynaptic pathway

Spinal Cord

Golgi Tendon ReflexThe Golgi tendon organ local areas of the cord inhibtory interneuron inhibits the anterior motor neuron dorsal horn Cerebellum and cerebral cortex (through long fiber pathways such as the spinaocerebellar tracts into the cerebellum and through still other tracts to the cerebral cortex)Negative feedbackTendon organ:detect tendon tension

Spinal Cord

Postural Reflex Flexor reflex and the withdrawal reflexes Crossed extensor reflexIntersegmental reflex:scratching reflexSpinal Cord

Flexor reflex and the withdrawal reflexes Crossed extensor reflexPainful stimulus detectedIpsilateral flexors excited-contractIpsilateral extensors inhibited limb is withdrawnContralateral flexors inhibited Contralateral extensors contract maintain balance and support weight

Spinal Cord

Scratching reflexInitiated by the itch and tickle sensationTo-and-fro scratching movementreciprocal innervation circuits that cause oscillationSpinal Cord

Brain StemDecerebrate rigidity: Rigidity of the antigravity muscles-the neck and trunk and the extensors of the legs.?:blockage of the input from the cerebral cortex, red nuclei, and basal ganglia medullary reticular inhibitory system becomes nonfuntional overactivity of the pontine excitatory systemBrain stem

Postural reflex controlled by the stemmaintenance of equilibriumAttitudinal reflex:Tonic labyrinthine reflex :Vestibular nucleiTonic neck reflex :proprioceptorsRighting reflex

Brain stem

Basal Ganglia and Motor Controla collection of nuclei deep to the white matter of cerebral cortex. caudate, putamen, globus pallidussubstantia nigra, subthalamic nucleus

Basal ganglia

Basal Ganglia

schematic summarizes the connections of the basal ganglia http://thalamus.wustl.edu/course/cerebell.htmlBasal ganglia

Parkinson's Disease muscular rigidity, difficulty with the initiation of movement, slowness of movement, a tremor while at rest, and instability of posturedamage to the dopamine pathway leading from the substantia nigra to the putamen of the basal ganglia.

Basal ganglia

Huntington's Chorea jerky, uncontrollable movementssecondary to damage of GABAergic and acetylcholinergic neurons of the caudate nucleus and the putamen nucleus of basal ganglia

Basal ganglia

cerebellumcerebellum

The cerebellum Vestibulocerebellum-balanceSpinocerebellum-muscle tonus and voluntary movementsCerebrocerbellum-plan and designcerebellum

Primary motor cortex and motor pathwayPrimary motor cortex: precentral gyrus cross control inversion the sizes of the areas according to the function of muscles

cortex

Motor pathwayCorticospinal tractsCorticobulbar tract

Autonomic Nervous Systemit runs bodily functions without our awareness or control.

Autonomic Nervous System

Comparison-sympathetic systemOrigins: The cells of the intermediolateral column in the thoracic spinal cordThey also travel to ganglia before reaching the target organ, but sympathetic ganglia are often far from the target Comprehensive; dispersion reflex

comparison -parasympathetic system Origins:located in different nuclei throughout the brainstem Preganglionic fiber travel to the target organ, synapse in ganglia in or near the organ wallLocalized distribution and reflex

The sympathetic systemThe sympathetic system evokes responses characteristic of the "fight-or-flight" response: pupils dilate, muscle vasculature dilates, the heart rate increases, and the digestive system is put on hold.

The parasympathetic systemThe parasympathetic system has many specific functions, including slowing the heart, constricting the pupils, stimulating the gut and salivary glands, and other responses that are not a priority when being "chased by a tiger".

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Visceral activitySpinal cordLower level of the brain stem:basal centerHypothalamusCerebrum cortex

Characteristics of the autonomic nervous systemDouble controlTonicEffector functionWhole body physiological function

HypothalamusThe main function of the hypothalamus is homeostasisthe hypothalamus can control heart rate, vasoconstriction, digestion, sweating, etc.1.body temperature2.water balance:ADH3. endocrine signals to/through the pituitary 4.biorhythm

Learning and memory

learningNonassociative learning: sensitivity and habituation of the synapsesAssociative learning:Conditioned reflex: reinforcementOperant conditioning: fulfillment of an action

Conditioned Reflex1.association2.reinforcement3.two types of signal system:First signal system:material signalSecond signal system:language (representation to the material signal)

Memory stagesprocedural memory Working memoryFirst gradememorydeclarative memory Short-termLong-termcircuitssynapses

amnesiaforgets Rapidly immediately after learningforgets Slowly as time goes on

: cant remember new signal: cant remember things just before the trauma

Mechanism of Learning and Remembering1.association cortex; hippocampus ;thalamus and reticular formation2.long-term potentiation; ciruits3.synthesis of peptides in the nervous system4.new synapses formation

Language Center

Language center

Laterality Cerebral DominanceDominant cerebral hemisphereLeft:Right:

The 3 unofficial rules of student learning:Amnesia: Students forget most of what they learn. Phantasia Students believe they understand, when they really don't. Inertia Students don't understand why they need to learn anything. Don't become part of this stereotype. Break the rules and succeed.

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