SISTEM SARAF PUSATSISTEM SARAF PUSAT

SITI SALWA BINTI MAIL880215-01-5970PISMP PJ ( 2 )/ 2008UNTUK PERHATIAN : EN CHE ISHAK ISMAIL

Central Nervous SystemCentral Nervous System• Consists of– Brain• Located in cranial vault of skull– Spinal cord• Located in vertebralcanal• Brain and spinal cord– Continuous with each

other at foramen magnum

• Components– Brain, spinal cord, nerves, sensory

receptors

• Responsible for– Sensory perceptions, mental activities,stimulating muscle movements, secretions

ofmany glands

• Subdivisions– Central nervous system (CNS)– Peripheral nervous system (PNS)

THE BRAINTHE BRAIN

VENTRICLES•Ventricles continuous with the another one and with the central canal of the spinal cord

•The hollow ventricular chambers are filled with cerebrospinal fluid an d lined by ependymal cells, a type of neuroglia

•The paired lateral ventricles, are large c-shaped chambers that reflect the pattern of cerebral growth.

•The lateral ventricles lie close together, separated only by a thin median membrane called the septum pellucidum

•Each lateral ventricles communicates with the narrow third ventricles via a channel called an interventricular foramen.

•The third ventricles is continuous with fourth ventricles via the canal like cerebral aqueduct .

• the cerebral hemispheres form the superior part of the brain.

•Nearly the entire surface of the cerebral hemispheres is marked by elevated ridges of tissue called gyri, seperated by shallow grooves called sulci

•Deeper groves called fissures, separate large regions of the brains

•Several sulci divide each hemisphere into five lobes, •Frontal•Parietal•Temporal•Occipital •Insula

•The central sulcus which is lies in the frontal plane, separates the frontal lobes from the parietal lobe.

•Bordering the central sulcus are the precentral gyrus anteriorly and the postcentral gyrus posteriorly.

•Each cerebral hemisphere has three basic regions: a superficial cortex of gray matter, which looks gray in the fresh brain tissue, an internal white matter; and the basal nuclei, island of gray matter situated deep within the white matter.

Cerebral hemisphere

CEREBRAL CORTEX

-Contains three kinds of functional areas : motor areas, sensory areas and association areas

-MOTOR AREAS- control voluntary movement, lie in the posterior part of the frontal lobes:

-Primary( somatic ) motor cortex-Premotor cortex-Broca’s area-Frontal eye’s field

•SENSORY AREAS• areas concerned with conscious awareness of sensation, the sensory of the cortex, occur in the parietal, insular, temporal and occipital.

•Primary somatosensory cortex•Somasensory cortex•Auditory areas•Olfactory ( smell) cortex•Gustatory ( taste )cortex•Visceral sensory cortex•Vestibular (equilibrium) cortex

Multimodal Association areas

-Multimodal association areas is more complexly connected, receiving inputs from multiple senses and sending outputs to multiple areas.

-Anterior association area-Posterior asscociation area-Limbic association area

DIENCEPHALON-Forming the Central core of the forebrain and surrounded by cerebral hemispheres.

-Consist largely of three paired structures:-The thalamus-Hypothalamus-Epithalamus

• Thalamus

•Consist of bilateral egg-shaped nuclei, which form the superolateral walss of the third ventricles•The nuclei are connected at the midline by an interthalamic adhesion ( intermediate mass)•the thalamus are contains a large number of nuclei, most named according to their relative location. Each nuclei has a functional specialty and each projects fibers to and receives.

Hypothalamus1.- The hypothalamus caps the brain stem and forms the inferolateral walss of the third ventricles2.Contains many functionally important nuclei. The main visceral control center of the body an is vitally important to overall body homeotasis

2.1 autonomic control center2.2 center for emotional response2.3 body temperature regulation2.4 regulation of food intake2.4 regulation of water balance and thirst2.5 regulation sleep-wake cycles2.6 control endocrine system functioning

3.Hypothalamus Controls TemperatureThe hypothalamus is like your brain's inner thermostat

(that little box on the wall that controls the heat in your house). The hypothalamus knows what temperature your body should be (about 98.6° Fahrenheit or 37° Celsius). If your body is too hot, t he hypothalamus tells it to sweat. If you're too cold, the hypothalamus gets you shivering. Both shivering and sweating are attempts to get your body's temperature back where it needs to be.

BRAIN STEMBRAIN STEM

-The brains stem regions are midbrain, pons and medulla oblongata-Brain stem centers produce the rigidly programmed, automatic behaviors necessary for survival-Positioned between the cerebrum and the spinal cord.

MID BRAINMID BRAIN-The midbrain (mesencephalon) occupies only a small region in humans (it is relatively much larger in "lower" vertebrates). We shall look at only three features: the reticular formation: collects input from higher brain centers and passes it on to motor neurons. -the substantia nigra: helps "smooth" out body movements; damage to the substantia nigra causes Parkinson's disease.

- the ventral tegmental area (VTA): packed with dopamine-releasing neurons that

= are activated by nicotinic acetylcholine receptors and = whose projections synapse deep within the forebrain.

- The VTA seems to be involved in pleasure: nicotine, amphetamines and cocaine bind to and activate its dopamine-releasing neurons and this may account — at least in part — for their addictive qualities.

PonsPons•The pons seems to serve as a relay station carrying signals from various parts of the cerebral cortex to the cerebellum. Nerve impulses coming from the eyes, ears, and touch receptors are sent on the cerebellum. The pons also participates in the reflexes that regulate breathing. The reticular formation is a region running through the middle of the hindbrain (and on into the midbrain). It receives sensory input (e.g., sound) from higher in the brain and passes these back up to the thalamus. The reticular formation is involved in sleep, arousal (and vomiting).

Medulla oblongataMedulla oblongata

• The medulla looks like a swollen tip to the spinal cord. Nerve impulses arising here

• rhythmically stimulate the intercostal muscles and diaphragm — making breathing possible •regulate heartbeat

•regulate the diameter of arterioles thus adjusting blood flow.

SPINAL CORDSPINAL CORD

• Extends from foramenmagnum to second lumbarvertebra • Segmented -Cervical -Thoracic -Lumbar -Sacral• Gives rise to 31 pairs ofspinal nerves

• Not uniform in diameterthroughout length

Meninges

•Connective tissue membranes surrounding spinal cord and brain – Dura mater – Arachnoid mater – Pia mater

•Spaces – Epidural: Anesthesia injected – Subdural: Serous fluid – Subarachnoid: CSF

Cross Section of Spinal Cord

Cross Section of Spinal Cross Section of Spinal CordCordWhite matter

•Myelinated axons forming nerve tracts

•Fissure and sulcus

•Three columns orfuniculi– Ventral– Dorsal– Lateral

Gray matter

• Neuron cell cell bodies,dendrites, axons• Horns Three columns or funiculi– Ventral– Dorsal– Lateral– Posterior (dorsal)– Anterior (ventral)– Lateral• Commissures– Gray: Central canal– White

Cells of Nervous SystemCells of Nervous System

Neurons or nerve cells– Receive stimuli and transmit actionpotentials

– Organization• Cell body or soma

• Dendrites: Input

• Axons: Output

• Neuroglia or glial cells– Support and protect neurons

TYPES OF NEURONSTYPES OF NEURONS • Functional classification– Sensory or afferent:

Action potentials toward CNS

– Motor or efferent: Action potentials away from CNS

– Interneurons or association neurons: Within CNS from one

neuron to another• Structural classification– Multipolar, bipolar,

unipolar

NEUROGLIA OF CNSNEUROGLIA OF CNSAstrocytes– Regulate

extracellular brain fluid composition

– Promote tight junctions to form blood-brain barrier

• Ependymal Cells– Line brain ventricles

and spinal cord central canal

– Help form choroid plexuses that secrete CSF

NEUROGLIA OF NEUROGLIA OF CNSCNS

• Microglia– Specialized

macrophages• Oligodendrocytes– Form myelin

sheaths if surround axon

NEUROGLIA OF NEUROGLIA OF PNSPNS

Schwann cells or neurolemmocytes

– Wrap around portion of only one axon to form myelin sheath

• Satellite cells– Surround neuron

cell bodies in ganglia, provide support and nutrients

• Myelinated axons– Myelin protects and insulates axons from one another– Not continuous• Nodes of Ranvier• Unmyelinated axons

Myelinated and UnmyelinatedAxons

Electrical SignalsElectrical Signals

Electrical Signals• Cells produce electrical signals called

actionpotentials• Transfer of information from one part

of body to another• Electrical properties result from ionicconcentration differences across plasmamembrane and permeability of

membrane

THE SYNAPSETHE SYNAPSE• Junction between twocells• Site where actionpotentials in one cellcause action potentialsin another cell• Types– Presynaptic– Postsynaptic

Chemical SynapsesChemical Synapses

Neurotransmitter RemovalNeurotransmitter Removal

Neuronal Pathways and

Circuits

Organization of neurons in CNS varies– Convergent pathways: Many converge and synapse with smaller numberof neurons– Divergent pathways: Small number of presynaptic neurons synapse withlarge number of postsynaptic neurons– Oscillating circuits: Arranged in circular fashion to allow action potentialsto cause a neuron farther along circuit to produce an action potential morethan once

Oscillating

Circuits