Nervous Physiology L1

8/9/2019 Nervous Physiology L1

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Physiology of the CentralPhysiology of the Central

Nervous SystemNervous System


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NERVOUS SYSTEMNERVOUS SYSTEM

CNSCNS PNSPNS

BRAINBRAIN SPINAL CORDSPINAL CORD ANSANS SNSSNS

SympatheticSympathetic ParasympatheticParasympathetic


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Structures/Substances that protect the

brain and spinal cordy Bones

y Meninges

y CSF

y Blood Brain Barrier


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BRAIN and SPINAL

CORD

BRAIN

SPINAL CORD


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Meninges

CRANIAL MENINGES

SPINAL MENINGES


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SUBDURAL SPACE


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Cerebrospinal FluidyFound in the ventricles, cistern and

subarachnoid space.

yProduced in the choroid plexus (50-

70%), ependymal surfaces, around the

blood vessels and subaracnoidal

membranes.

yConstitutes 15% of the brain volume


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Characteristics of cerebrospinal fluid

yCSF is clear, colorless and alkaline fluid

y

Volume 150 mlyRate of production 500 - 550 ml/day

yTurnover 3 - 4 times / day

yCSF pressure 120 180 mm H2O or70 180 mm CSF


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Functions of CSF

yIt protects the brain and spinal

cordyIt regulates the extracellular

environment of the brain and

spinal cordyProvides nutrition


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Hydrocephalus

yAccumulation of large amount of

fluid (CSF) in the brain.


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Blood Brain BarrieryBarrier to free ion flow between the blood

and the brain tissue.

yImmature at birth

yComposed of;

y Endothelial cells (tight junction)

y Epithelial cells of the choroid plexus (tight

junction)

y Plial and arachnoid membranes

y Footlike processes of asrocytes


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yDisruption of BBB can be due to;yInfection

yTrauma/injury

yTumors

yMarked increases in blood pressure

y

Intravenous injection of hypertonicfluid


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Functions of BBByIt maintains the constancy of the

environment of the neurons in the CNS.

yIt protects the brain tissue from

endogenous and exogenous toxins in the

blood

yIt prevents the escape of NTA into the

general circulation.


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Permeability of BBB

yhighly permeable (small and non polar)

y water, CO2, O2, L-dopa (dopamine), and 5-HT

(serotonin)

y less permeable (small and large polar

substances)

y glucose (GLUT1 55k and 45k), HCO3-, Na+, Cl-

K+

(Na+

K+

Cl-

cotransporter), H+

etc.y impermeable

y proteins protein-bound substances


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Cerebral HemispheresyyActivity in the two hemispheres isActivity in the two hemispheres is

coordinated by interconnectionscoordinated by interconnectionsthrough the cerebral commisures.through the cerebral commisures.

yyBulk of the neocortex is interconnectedBulk of the neocortex is interconnectedthrough the corpus callosumthrough the corpus callosum


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Cerebral Dominance

yyDominant (Categorical ) HemisphereDominant (Categorical ) Hemisphereyy For sequential and analytical processesFor sequential and analytical processes

yy Main language centerMain language center

yy Center for calculationCenter for calculation

yy Expressing ideas in speech and writingExpressing ideas in speech and writing

yy

Understanding printed and spoken wordsUnderstanding printed and spoken wordsyy StereognosisStereognosis

Dominance appears at about 5 7 years of age


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yyNonNon--dominant (representational) hemispheredominant (representational) hemisphere

yySpatiotemporal relationsSpatiotemporal relations

yySimple language comprehensionSimple language comprehension

yyStereognosisStereognosis

yyNonNon--verbal ideationverbal ideation

yyRecognition of facesRecognition of faces

yy Identification of objects by their formIdentification of objects by their form

yyAppreciation of art/music/tonesAppreciation of art/music/tones

yy Interpretation of body languageInterpretation of body language


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Hemispheric dominance - Handedness

y In 96% of right handed the dominant hemisphere isthe left

y

In 15% of left handed the dominant hemisphere isthe right

y In 15% of left handed there is no clear lateralization

y In 70% of left handed the dominant hemisphere is

the left


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Basal GangliayControls rate of voluntary motor

activity

yEither enhance or decrease voluntary

motor activity

y

Also involved in planning andprogramming motor command


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LIMBIC SYSTEM

y Formerly called

rhiencephalon

y Intimately concerned with

emotional expressions

(fear, rage and sexual

behavior) and with the

genesis of emotionsy plays a role in olfaction

y concerned with autonomic

responses


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Limbic Systemy The allocortex and juxtallocortex

y Major connections to the hippocampal system,

olfactory tract and amygdalay Along with the hypothalamus concerned with

sexual behavior, emotions (rage & fear) andmotivation

Prolonged after-discharge following stimulation

so emotion is not easily turned on and off at will


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EMOTIONSyMental Components

y Congnition

y Affect

y Conation

yPhysical Componentsy

Hypertensiony Tachycardia and tachypnea

y Sweating


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THALAMUSsensory and motor relay to the cerebral cortex


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HYPOTHALAMUS


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Functions of Hypothalamusy regulation of body temperature

y anterior hypothalamus - response to heat

y posterior hypothalamus - response to cold


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Functions of Hypothalamusy regulation of endocrine activity by secreting

various hormones:y ADH (vasopressin)

y Oxytocin

y catecholamines Arcuate nucleus

y CRH - paraventricular

y GRH - paraventricular and arcuate nuclei

y TRH - paraventricular nuclei

y GnRH - preoptic

y PRH /PIH - periventricular and arcuate nucleus

ParaventricularSupraoptic nuclei


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Functions of Hypothalamusy regulation of food

intake

y satiety center -ventromedial nucleus

y decreases appetite when

stimulated

y feeding center - lateral

hypothalamus

y increases appetite when

stimulated


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Functions of Hypothalamusy regulation of water

intake

y thirst center - lateralhypothalamus

y increases water intake when

stimulated

y controls circadian

rhythmy suprachiasmatic nuclei


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Functions of Hypothalamus

y regulation of

autonomic responsesy concerned with sexual

behavior, emotions of

rage and fear

and motivation


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y autonomic function

y regulation of the cardiovascular system

y regulation of the respiratory systemy body water and electrolyte balance

y regulates GI secretory activities


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ENDOCRINE FUNCTIONS


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BRAIN STEMyComposed of

y

MidbrainyPons

yMedulla

oblongata


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MIDBRAINy acoustic relay, control

of eye movement and

motor controly cranial nerves

associated with the

pons and midbrain

are III, IV, V, VI andVII


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PONSy respiratory and urinary

bladder control

y vestibular control of eyemovement


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MEDULLA OBLONGATAy contains vital centers

y Cardiovascular centers

y Respiratory centers

y responsible for brainstemreflexesy vomiting

y sneezing

y

swallowing (centralprogram generator)

y gagging

y coughing


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yy control of visceral functions and brainstemcontrol of visceral functions and brainstem

reflexesreflexes

yy

cranial nerves associated with the medullacranial nerves associated with the medullaare the XII, XI, X, IX and part of VII.are the XII, XI, X, IX and part of VII.

yybrainstem reflexesbrainstem reflexes Gustatory, Gag, Cough,Gustatory, Gag, Cough,

BaroreceptorBaroreceptor, Chemoreceptor, Chemoreceptor, Vomiting, Vomiting


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CEREBELLUMinvolved in motor

coordination


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CEREBELLUMCEREBELLUM

helps regulate movements and posturehelps regulate movements and posture

and also involved in some forms ofand also involved in some forms of

motormotorlearning.learning.

its major role is for motor coordinationits major role is for motor coordination

(rate, range, force and direction of the(rate, range, force and direction of themovement)movement)


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SPINAL CORD


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Spinal Cordy Center for reflex actions

y Somatic and autonomic afferent pathways

y Somatic and autonomic efferent pathways

y Center for micturition and defecation

y Exerts tonic influence on muscles

y

Involve in the execution of motor commandsy Provides communicating branches for the

autonomic nervous system

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Nervous Physiology L1