Central Nervous System

Central Nervous System

1. Central Nervous System Prepared by Mr. Vinayak R. Bodhankar M. Pharm. (QA)

2. CONTENTS Nervous system Central nervous system Division of CNS Brain and its parts Spinal cord Other structures in the brain PNS ANS Physiology of ANS

3. NERVOUS SYSTEM The nervous system is divided into CNS consist of Brain & Spinal cord. PNS consisting of: a. 31 pairs of cranial nerves arising from spinal cord b. 12 pairs of cranial nerves arising from brain. c. Autonomic nervous system: i ) Sympathetic nervous system ii) Parasympathetic nervous system

4. The central nervous system (CNS) is comprised of the brain and spinal cord . The CNS receives sensory information from the nervous system and controls the body's responses . The brain plays a central role in the control of most bodily functions, including awareness, movements, sensations , thoughts, speech, and memory. Some reflex movements can occur via spinal cord pathways without the participation of brain structures . The spinal cord is connected to a section of the brain called the brainstem and runs through the spinal canal . CENTRAL NERVOUS SYSTEM

5. 2 Divisions of the central nervous system

6. The Brain The brain is the control center of the body It is about 2% of your body weight and uses 20% of your body’s oxygen . The central nervous system is made up of the brain and spinal cord. The brain constitutes about one- fiftieth of the body weight and lies within the cranial cavity. The brain parts are Cerebrum The brain stem (midbrain, pons, medulla oblongata) Cerebellum The average brain weight of the adult male was 1336 gm, for the adult female 1198 gr. With increasing age, brain weight decreases by 2.7 gr in males , and by 2.2 gr in females per year.

7. Cerebrum: This is the largest part of the brain and it occupies the anterior and middle cranial fossae. Gray Matter – Absence of myelin in masses of neu r o n s a cc ou n t s f or th e g ra y ma t t er of the brain – Cerebral Cortex . White Matter - Myelinated neurons gives neu r o n s a w hi t e ap p ea r an c e – inne r l a y er of cerebrum The cerebral cortex is the outer covering of gray matter over the hemispheres . Largest part of the brain : Learning and Senses 2 hemispheres- Right and Left Connected by the Corpus Callosum Right side controls- left side Left side controls – right side of body Each hemisphere of the cerebrum is divided into lobes which take the names of the bones of the cranium under which they lie: frontal parietal temporal Occipital Cerebral cortex 7

8. 8 FUNCTIONS OF THE CEREBRUM Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving P ari e t al Lob e- ass o ci a t ed with mo v e m e n t, o rie n t a t ion , recognition, perception of stimuli Occipital Lobe- associated with visual processing T empo r al Lob e- as s o c i a t e d w i t h pe r c e p t ion and recognition of auditory stimuli, memory, and speech

9. CEREBELLUM Th e c e r e b ellum is s itu at ed behin d the pon s and immediately below the posterior portion of the cerebrum It is ovoid in shape and has two hemispheres, separated by a narrow median strip called the vermis . Second largest located below the cerebrum at back of skull This part is responsible for the balance and muscle coordination

10. 10 Functions of cerebellum The cerebellum is concerned with the coordination of voluntary muscular movement , posture and balance. It coordinates activities associated with the maintenance of the balance and equilibrium of the body. It is also involved in certain cognitive functions, such as language . The cerebellum plays a major role in adapting and fine- tuning motor programs to make accurate movements through a trial-and-error process . Damage to the cerebellum results in clumsy uncoordinated muscular movement, staggering gait and inability to carry out smooth, steady, precise movements .

11. THE BRAIN STEM ( midbrain, pons, medulla oblongata) Brain stem is the stem-like part of the base of the brain that is connected to the spinal cord . This structure is responsible for basic vital life functions such as breathing, heartbeat, and blood pressure . Medul l a o b l on g a t a d i r e c t l y c o n t r ols b r e a thin g , b lo od flow, and other essential functions . 11 Connects the brain to spinal cord Th e T w o R eg i ons act as “ s w i t chboa r d” Medulla Oblongata – Controls heart rate, breathing rate, and flow of blood through the blood vessels. Pons – Relays signals between the cerebrum and the cerebellum

12. SPINAL CORD Link between brain and rest of body (PNS) 31 pairs of spinal nerves Spinal cord is continuous above with the medulla oblongata . It is a long, thin bundle of nervous tissue. It is approximately 45 cm long in an adult male , and is about the thickness of the little finger . The spinal cord receives and transmits electric signals throughout the entire body & then back to the brain. 12 The white matter tracts in the spinal cord are highways for nerve impulse propagation. Sensory input travels along these tracts toward the brain (afferent neurons), and motor output travels from the brain along these tracts toward skeletal muscles and other effector tissues (efferent neurons). The gray matter of the spinal cord receives and integrates incoming and outgoing information.

13. The spinal cord enables us to do the things automatically. This automatic action is called as Reflex action. For e.g., when you touch a hot object, you immediately withdrawn your hand. This action does not involve your brain because you do not think at all whether you avoid the hot object or not. In a Reflex action, the nerve impulses take a special pathway called as Reflex arc. A reflex is rapid automatic response to the environment that happened without action of the brain. They can be movement or develop through memory. The brain remembers how to respond to certain signals or situations. This is called as conditional reflex.

14. THALAMUS R eceive messages from sensory receptors; relays information to proper regions of cerebrum HYPOTHALAMUS Regulates hunger, thirst, fatigue, anger, etc … Control of pituitary for endocrine function Other Structures inside the Brain P ons Pituitary gland Hypothalamus Cerebrum Medulla oblongata S pin a l cord Cerebellum Thalamus P in e al gland Secti o n 35-3

15. PERIPHERAL NERVOUS SYSTEM Spinal nerves: 31 pairs 8 pairs of cervical nerves 12 pairs of thoracic nerve 5 pairs of lumbar nerve 5 pairs of sacral nerve 1 pair of coccygeal nerve Nerve Plexuses Cervical Brachial Lumbar Sacral Cranial nerves Olfactory Optic nerve Occulomotor Trochlear Trigeminal Abducens Facial Vertibulocochlear Glossopharyngeal Vagus Accessory Hypoglossal

16. AUTONOMIC NERVOUS SYSTEM CNS makes person aware of external environment. Many activities which do not reach the consciousness of person are regulated and controlled by the system called as ANS. Thus ANS controls and regulate the involuntary functions. Called as Autonomic because it is not under the control of will. Division of ANS Sympathetic nervous system Enables the individual to adjust to stress . It originates in the thoracic and the lumbar region of the spinal cord. Parasympathetic nervous system Participate in tissue building. It originates in the cranial and sacral region of the spinal cord.

17. PHYSIOLOGY OF ANS Sympathetic stimulation Organ Parasympathetic stimulation Dilate the pupils Eye Constrict the pupils Bronchodilation Bronchi Bronchoconstriction Increase heart rate Heart Decrease the heart rate Vasodilation Blood vessels Vasoconstriction Relaxation Smooth muscle Increases the movement Increase the sweating Sweat glands Decrease the salivation Salivary gland Increase the salivation Inhibit secretion Gastric gland Increase secretion Kidney Decrease urine flow Blood flow Relaxation of muscle wall Urinary bladder Constriction of muscle wall Increase Metabolic effect Contraction of uterine muscles Sex organs Vasodilation and erection