Central Nervous system (CNS):
(i) Dura Mater: It is the first and the outermost membrane which is thick, very strong and nonelastic.
(ii) Arachnoid Mater: It is middle, thin, delicate and non-vascular membrane found only in mammals.
(iii) Pia Mater: It is innermost, most vascular, thin and transparent membrane.
The space between the arachnoid and pia mater is filled with a fluid called cerebrospinal fluid (CSF). It protects the brain from mechanical shocks.
Meningitis: Any inflammation of meninges is called meningitis.
Weight of brain: In adult male 1400 gm, female 1250 gm.
Parts of Brain:
|(1) Fore brain||(a) Cerebrum||(b) Diencephalon|
|(2) Mid brain||(a) Crura cerebri||(b) Corpora quadrigemina|
|(3) Hind brain||(a) Cerebellum||(b) Pons||(c) Medulla oblongata|
(1) Forebrain (Prosencephalon):
(a) Cerebrum (Telencephalon):
(i) Anterior: Frontal lobe for intelligence, knowledge, abstract, reasoning,creative ideas and memory.
(ii) Middle: Parietal lobe for taste, writing, pain, touch and pressure.
(iii) Lateral: Temporal lobe for language, hearing and smell.
(iv) Posterior: Occipital lobe meant for vision.
Fig: Various lobes of cerebrum
Fig: Median section of the brain
(2) Mid brain (Mesencephalon):
(a) Cerebral peduncles (Crura cerebri):
(b) Optic lobes (Corpora Quadrigemina):
(3) Hind Brain (Rhombencephalon):
(c) Medulla oblongata:
(i) It controls all the involuntary activities of the body. e.g. - heart beats, respiration, blood pressure salivation.
(ii) It also concerned with some reflexes- sneezing reflex, coughing reflex, vomiting reflex, yawning reflex.
|Difference between cerebrum and cerebellum|
|1||Part of||Fore brain||Hind brain|
|2||Size||Largest part of brain||Second largest part of brain|
|3||Function||Associated with intelligence, memory||Associated with body balance and posture|
(B) Spinal Cord
Functions of spinal cord -
(i) Spinal cord regulates and conducts the reflex actions.
(ii) It acts as bridge between brain & organs of the body.
(iii) It also provides relay path for the impulses coming from brain.
(i) Watering in mouth on sight of food
(ii) Closing of eyes when flashed with strong light.
(iii)Withdrawal of hand when pinched with a needle.
(iv)Blinking of eyelids, gut peristalsis, yawning, sneezing, coughing.
PERIPHERAL NERVOUS SYSTEM:–
(A) Cranial Nerves:–
(B) Spinal Nerves:–
AUTONOMIC NERVOUS SYSTEM (ANS)
(a) Sympathetic nervous system
(b) Parasympathetic Nervous system.
(a) Sympathetic Nervous System:–
(b) Para sympathetic Nervous System:–
|Effects of sympathetic and parasympathetic nervous system|
|S. No.||Organs involved||Sympathetic effect||Parasympathetic effect|
|1||Eyes||Dilation of pupil||Constriction of pupil|
- Cerebrospinal Fluid (C.S.F):– This fluid is clear and alkaline in nature just like lymph. C.S.F is present in ventricle of brain, subarachnoid space between arachnoid and piamater and spinal cord. It acts as shock absorbing medium.
- Broca's area: It is motor speech area, present in frontal lobe of cerebrum. If it gets destroyed the animal becomes unable to speak.
- In human brain more than 100 billion neurons are present.
- In mammals the speed of nerve impulse is 100-130 m/sec.
- Grey matter: It is composed of cytons and non-medullated nerve fibres.
- White matter: It is composed of medullated nerve fibres.
- Electroencephalograph: is an instrument which records the electrical activity of the brain in the form of a graph of electric potentials generated with time. Such a record in called electroencephalogram (EEG). The electroencephalogram (EEG) of a patient is done by placing two electrodes of electroencephalograph instrument on the scalp of the patient. Then a record of four different types of waves (a, b, d and q) is produced on the graph paper. These waves vary in their frequency. These waves give the characteristic activity of the brain of a person. The EEG of a patient is useful to diagnose brain ailment.
|1. What is the central nervous system?|
|2. How does the central nervous system function?|
|3. What is the role of the human brain in the central nervous system?|
|4. How is the central nervous system protected?|
|5. Can the central nervous system be affected by diseases or injuries?|