CENTRAL AND PERIPHERAL NERVOUS SYSTEM

Anatomical division of nervous system

• Central nervous system (CNS)• Consist of brain located in cranial cavity and spinal card

located in vertebral canal.

• CNS is responsible for integrating, processing , and coordinating sensory data, and giving appropriate motor command.

• It is also the seat of higher functions such as intelligence, memory, learning and emotions.

• Peripherar nervous system (PNS) includes all the neural tissues outside the CNS , such as 12 pairs of cranial nerves, 31 pairs of spinal nerves and plexus, ganglia associated with cranial, spinal nerves and autonomic ganglia.

• The PNS provides sensory information to the CNS and carries its motor commands to the peripheral tissues and systems.

C5-T1

L1-L4

Functional division

• Afferent brings sensory information to the CNS• Efferent carries motor commands to the muscles

and glands. somatic nervous system (SNS) it provides the

voluntary control over the skeletal muscle contraction

autonomic nervous system (ANS) innervates involuntary structures such as heart, smooth muscle and glands and thus provides an involuntary regulation of smooth muscle,

cardiac muscle, and glandular activity

Central nervous system

Brain and spinal card • Both of them consist of gray matter and white matter

• In brain the gray matter consist of nerve cell bodies and dendritesand present at the periphery,while white matter is made up predominantly of myelinated nerve fibres present in the centre.

• In spinal cord the white matter is outside and gray matter in side.

• Both grey and white matter contain neuroglia(supporting cells) and blood vessels

Brain • The adult brain constitutes about one-fiftieth (1/50) of body

weight(2%of body wt) and weighs about 1400g in male(to accommodate more body mass and muscle group) and 1200g in female.

• Neurons=100 billion, uses 20% of body energy, 20% ardiac out put,25% of total body glucose, low gluse leeds to coma

• It consist of following parts1. Cerebrum2. Diencephalon3. Medbrain4. Pons5. Medulla oblongata 6. Cerebellum

Brain stem

A. Prosencephalon –forebrain (1,2) -telecephalon:- cerebral hemispheres + lateral ventricles

- diencephalon:- -thalamus + 3rd ventricle -hypothalamus- optic cup-pituitary -pineal body

B. Mesencephalon: midbrain (3,4) aqueduct of sylvius

C. Rhombencephalon: hind brain - metencephalon – pons(5), cerebellum -Myelencephalon- medulla oblongata (6-12) + 4th ventricle

-central canal-subarachnoid space

Foramen of monro

F. LuschkaF. magendie

Functions of the brain

• It receives information from, and controls the activities of trunk and limbs mainly through its connections with the spinal cord.

• It receives the information from, and controls the activities of head and neck structures though cranial nerves

• It assimilates experiences, a requisite to higher mental processes such as memory, learning and intelligence

• It is also responsible for one’s personality, thoughts and aspirations.

Cerebrum • Consists of two hemispheres left and right,

occupy the anterior and middle cranial fossae, and supratentorial region of posterior cranial fossa.

• The two hemispheres are separated by longitudinal cerebral fissure, the fibres of corpus callosum interconnect the corresponding cortical areas of the two cerebral hemispheres, and lies in the floor of cerebral fissure.

• The surface of cerebral hemisphere is convoluted, have elevations(gyri) and shallow depressions (sulci)

Cerebrum (cont)

• The central sulcus runs downwards and forwards from superomedialborder to the lateral sulcus.

• The superolateral surface of each cerebral hemisphere is divided into four lobes, which are named after the overlying skull bones.

• Frontal lobe: is anterior to the central sulcus, is important for voluntary motor functions, motivation, aggression, emotions, effect, drive and awareness of self.

• Parietl lobe is posterior to the sulcus , is the major center for reception and evaluation of all sensory information except for smell hearing, and visions

• Occipital lobe is behind the parieto-occipital sulcus, is responsible for occupation and integration of visual input

• Temporal lobe is below the lateral sulcus , receives and evaluates input for smell and hearing and plays an important role in memory

Cerebrum (cont)

• Limbic system / lobe is a complex ring-shapemass of grey matter situated at the junction of telencephalon and diencephalon.

• It consisting of cingulate gyrus, isthmus parahippocampal gyrus, uncus, dentate gyrus

• It is associated with basic survival instincts, viz. acquisition of food and water and reproduction (sexual behaviour)

Cerebrum (cont)

• Basal Ganglia is subcortical masses of gray matter which are situated in the white core of each cerebral hemisphere

• It include the lentiform nucleus, caudate nucleus, claustrum, and amygdaloid body (these also called extraphramidal nuclei.

• It regulate the muscle tone and helps in smoothening the voluntary motor activities of the body.

• It control automatic associated movements, like swinging of arms during walking

• Control reflex muscular activity

• Its lesion cause parkinsonism

Diencephalon Part of the brain between cerebrum and brain stem

Thalamus is the Largest part of the diencephalon, thalamus in each hemisphere are separated from one another by 3rd

ventricle

• Functions: it forms a great gate-way for all sensory impulses except smell, crude sensations like pain and touch.

• It project sensation to the cerebral cortex

Hypothalamus:

• it is the inferior portion of diencephalon, which forms the floor and inferolateralwall of the third ventricle. Grossly it is about 4.0 gm

• It componints are optic chiasma, infundibulum, tubercinereum and mammillary bodies

• it contains several small nuclei and nerve tracts.

• It regulate visceral activity through autonomic nervous system and hormonal activity through the hypothesis cerebri

• Metathalmus:

• it consist of oftwo medial 7 lateral geniculate bodies,

• function’s as relay stations for auditory and visual impulses

Epithalamus• situated posterior to the

thalamus,consist of pineal body and habenular nuclei.

• Pineal body is endocrine gland,secretesmelatonin,regulatedevelopment of gonades,secondry sexual characters.reduction of malatonin secretion precipitate puberty

• Habenular nuclei have olfactory and limbic connections,influenced by smell and involved by emotional and visceral response

Subthelamus:• it lies between

thalamus and midbrain

• it is involved controlling motor function(inhibitory control on basal nuclei and cerebral motor cortex

Mid Brain • Is the small part of brain stem, is just superior to the pons and contain the

nuclei 3rd and 4th cranial nerves. It is traversed by the cerebral aqueduct.

• The part dorsal to the aqueduct, is called tectum, which consist of two superior and two inferior colliculi, which in turn concerned with visual and auditory reflexes

• Cerebral peduncles are ventral to the aqueduct,each consist of tegmentum,substantia nigra,crus cerebri.space between the two crus cerebri is called interpeduncular fossa

• Function: are ocular reflexes , postural reflexes .contain sensory and motor tracts to and from cerebral cortex, basal nuclei cerebellum,thalamus,spinal cord

•

• Contain 3rd ,4th cranial nuclei

Hind brain

Pons

cerebellum

medulla oblongata

Pons• Middle Part of the brain stem.

• Pons mean bridge, it connect two cerebellar hemispheres by middle cerebellar peduncles

• The verticle median sulcus lodges basilar artery

• Dorsal part (tegmentum) is the direct upward continuation of medulla oblongata(reticular formation) contain motor and sensory nuclei of 5th cr n.

• Function= contain vital centres(circulatory,respiratory)

Medulla oblongata• Lower part of brain stem, continuous

inferiorly with spinal cord at foramen magnum

• On the ventral surface have two pyramidal shaped elevations produced by cortico- spinal tracts involved in conscious control of skeletal muscles

• Lateral to pyramids oval elevations called inferior olivary nuclei

• Dorsal to each olive is an inferior cerebellar peduncle

• On the dorsal aspect have cuneate and gracile tubercles,containg similarly named nuclei

• Medulla contains various vital autonomic centres responsible for several reflexes such as thiose involved in regulation of heart rate,blood vessels diameter,breathing,swallowing,vomiting,coughing,sneezing

Cerebellum (little brain)

• Lies dorsal to pons &medulla.consist of 2 hemispheres and median worm like part vermis

• Connected with mid-brain by superior cerebellar peduncle,with pons by middle cerebellar peduncle,with medulla by inferior cerebellar peducle

• Surface has narrow transverse ridges called folia(leaf) separated by fissures

• Function= involuntry control of somatic motor activities(maintenace of equilibrium,muscle tone,andposture)