Control & Coordination - III

Human Brain ● Delicate organ ● Protected inside Brain Box ( Cranium)● Meninges (Coverings of Brain ):-

○ Duramater ○ Arachnoid○ Piamater

● Cerebrospinal Fluid (CSF) :- It is clear colourless slightly alkaline fluid ,filled spaces between membranes.

○ Shock absorber○ Provide cushioning○ Nutrient and waste exchange

Human Brain

● Broadly divided into 3 parts : 1. Fore brain

a. Olfactory lobesb. Cerebrumc. Diencephalon

i. Epithalamus ii. Thalamusiii. Hypothalamus

2. Mid brain 3. Hind brain

a. Cerebellumb. Pons c. Medulla oblongata

1. Fore brain (Prosencephalon)

A. Olfactory lobes :-● Present in pair ● Present in inferior surface or base of the

cerebrum● Relay sense of smell received from olfactory

epithelium (nose ) to cerebrum

B. Cerebrum

● Largest & main thinking part of brain.● It is divided into two cerebral hemisphere:● Both hemisphere are attached by a thick nerve band composed of white

matter called Corpus Callosum.● Each cerebral hemisphere divided into 4 lobes :-

Frontal lobe Parietal lobe Occipital lobe Temporal lobe

● Cerebral Cortex : Outer portion of cerebrum ,made up by thick outer layer of grey matter

● Gyri & Sulci are present on cortex .

● Cerebral Cortex contain 3 areas :

Sensory Area Motor

AreaAssociation Area

● Cerebral Medulla : Inner to Cerebral Cortex ,made up by white matter.● Functions of Cerebrum :

○ Seat of intelligence , memory ,consciousness & will power○ It controls all voluntary actions.

C. Diencephalon

Epithalamus Thalamus Hypothalamus

● It is thin and not formed of nervous tissue,only glial cells.

● Behind it ,there is a short stalk,pineal stalk,where pineal gland hangs.

Epithalamus

● It lies superior to midbrain ● It is composed of primarily of grey matter● The optic nerves which come from the eyes,form a crossing ,the optic

chiasma in front of the hypothalamus.● It relay sensory and motor signals

Thalamus

● Pituitary gland directly attached to hypothalamus via infundibulum● The hypothalamus contains a number of centres which control body

temperature, urge for eating and drinking. ● It also contains several groups of neurosecretory cells, which secrete

hormones called hypothalamic hormones

Hypothalamus

2. Mid Brain (Mesencephalon)

● Small portion of brain convey sensory information to the cerebrum.● A canal called the cerebral aqueduct passess through the midbrain● It consists of

Corpora quadrigemina Cerebral

peduncles

● Consists of a pair of superior and inferior colliculi● Superior colliculi are concerned with sense of sight● Inferior colliculi are concerned with hearing .● The superior and inferior colliculi of each side are termed as corpora

bigemina.

Corpora quadrigemina

● These are two bundles of fibres which lie on the lower or inferior surface of the midbrain

● They relay impulses back and forth between the cerebrum,cerebellum,pons and medulla.

Cerebral peduncles /Crura Cerebri

3. Hindbrain (Rhombencephalon )

Cerebellum Pons Varolii Medulla Oblongata

● Second largest part of human brain

● Cerebellum has very convoluted surface in order to provide the additional space for many more neurons.

Cerebellum

● It consists of two lateral cerebral hemisphere ● Central worm shaped structure vermis connects them● A cross section of the cerebral hemisphere shows a branching tree like

arrangement of grey and white matter called arbor vitae (“tree of life”)● Functions :

○ It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

● It is situated in front of the cerebellum below the midbrain and above medulla.

● Pons consists of fibre tracts that form bridge between two cerebral hemisphere and of fibres which pass between higher levels of the brain and spinal cord.

● Pneumotaxic centre is present

Pons Varolii

● The medulla contains centres which control respiration, cardiovascular reflexes and gastric secretions.

● It receives and integrates signals from spinal cord and send resulting signals to cerebellum and thalamus

● It consists centre for blood pressure,breathing, swallowing ,salivation,sneezing,vomiting,coughing

● The medulla of the brain is connected to the spinal cord.

Medulla Oblongata

Peripheral Nervous System

● The nerves originate from the central nervous system and connects either receptor or effector organs , form PNS.

Cranial Nerves Spinal Nerves

1. Olfactory2. Optic3. Occulomotor4. Trochlear5. Trigeminal6. Abducens7. Facial8. Vestibulocochlear9. Glossopharyngeal

10. Vagus11. Accessory12. Hypoglossal

● 31 pairs ● They are named and numbered according to which vertebrae with

which they are associated.○ Cervical nerves : 8 nerves○ Thoracic nerves : 12 pairs○ Lumbar nerves : 5 pairs○ Sacral nerves : 5 pairs○ Coccygeal : 1 pair

Spinal Nerves

PNS

SOMATIC NEURAL SYSTEM

AUTONOMIC NEURAL SYSTEM

Parasympathetic Neural System

Sympathetic Neural System

● ANS controls & coordinates the involuntary activities of various organs● This system is autonomous in the sense that it regulates such activities

of the body in which the will power of the animal is not involved e.g secretion of digestive fluid

Autonomic Nervous System