Classification of Nervous System

Functions of nervous system
Classification of nervous system- central nervous system and peripheral nervous system.

1. NERVOUS SYSTEM SALMA ASGHAR M.Sc (NUTRITION AND DIETETICS)

2. • It is the master controlling and communicating system of the body. • It controls and coordinates all the activities of the body FUNCTIONS: Sensory function: Gathers information from both inside and outside the body. Integration function : Processes the information in the brain and spine. Motor function: Transmit information to the processing areas of the brain and spine.

3. CLASSIFICATION OF NERVOUS SYSTEM:

4. CENTRAL NERVOUS SYSTEM (CNS) ~It includes brain and spinal cord. ~It is referred to as central because it combines information from the entire body and co-ordinates activity across the whole organism. ~ These organs work together to integrate and co-ordinate sensory and motor information for the purpose of controlling the various tissues, organs and organ system of the body. ~It is formed by neurons and supporting cells called Neuroglia. ~Brain and Spinal cord are surrounded by three layers of meninges called the outer dura mater, middle arachnoid mater and the inner pia mater.

5. BRAIN: ~It is situated in the skull. ~It consists of- • cerebrum • cerebellum • diencephalon • medulla oblongata • midbrain and •pons

6. CEREBRUM: ~It forms bulk of the brain. ~It is divided into two hemisphere - left and right. ~The hemispheres are further divided into 4 lobes- •Frontal ( Reasoning and thought) •Parietal (Integrates sensory information) •Temporal (Processes auditory information from ears) •Occipital (Processes visual information from the eyes)

7. CEREBELLUM: ~Major functions of cerebellum are -muscle contraction -balance -posture -muscle tone - maintenance of movements.

8. DIENCEPHALON: ~It includes thalamus and hypothalamus THALAMUS : ~It directs sensory impulses to cerebrum. HYPOTHALAMUS: ~It controls and regulates the functions of ANS -Temperature, appetite, water balance, sleep, and blood vessel constriction and dilation. ~It also plays a role in anger, pleasure, pain and affection.

9. MIDBRAIN : ~It is responsible for eye and auditory reflexes. PONS: ~It is responsible for certain reflex actions. MEDULLA OBLONGATA: ~It regulates - digestion, respiration, swallowing, coughing, sneezing, blood pressure, heart and blood vessel function.

10. THE SPINAL CORD: ~It is a link between brain and nerves in the rest of the body. ~It consists of 4 regions- cervical, thoracic, lumbar and spinal nerves (efferent and afferent) ~ Afferent carries information from body to the brain. ~ Efferent carries information from brain to body ~ It acts as the middleman between the receptors and the effectors, as it conducts sensory and motor impulses to and from the brain.

11. PERIPHERAL NERVOUS SYSTEM: ~ It is formed by the nerves that are associated with the brain (cranial nerves) and the spinal cord (spinal nerves). ~It connects CNS to the organs, limbs and skin. ~These nerves extend from the CNS to the outermost areas of the body. ~Cranial nerves-12 pairs in man. ~Spinal nerves-31 pairs in man. ~ It is again divided into two subdivisions: •SOMATIC NERVOUS SYSTEM •AUTONOMIC NERVOUS SYSTEM

12. SOMATIC NERVOUS SYSTEM: ~It is part of PNS responsible for carrying sensory and motor information to and fro from the CNS. ~It is made up of nerves that connect to the skin, sensory organs and skeletal muscles ~ It is responsible for nearly all voluntary muscle movements. ~Processes sensory information from external stimuli (hearing, touch and sight). .

13. ~The structures that allow this communication to happen are- afferent sensory neuron - efferent motor neuron ~ Afferent neurons take information from nerves to CNS. ~ Efferent neurons take information from CNS to muscle fibres throughout the body.

14. AUTONOMIC NERVOUS SYSTEM: ~The ANS is the portion of the nervous system that controls most visceral function of the body. ~This system helps to control arterial pressure, gastrointestinal secretion, urinary bladder emptying, sweating, body temperature and other activities. ~One of the most striking characteristics of ANS is the rapidity and intensity with which it can change visceral functions.

15. ~ For instance, within 3-5 sec it can increase the heart rate to twice the normal and with in 10-15 sec the arterial pressure can be doubled. ~At the other extent, the arterial pressure can be decreased low enough within 10-15 sec to cause fainting. ~ Sweating can begin within seconds and urinary bladder may empty involuntary also within seconds. ~ The ANS is activated mainly by centres located in the spinal cord, brainstem and hypothalamus.

16. ~ Autonomic nervous system consists of two subdivisions: • Sympathetic division • Parasympathetic division

17. SYMPATHETIC DIVISION: ~It is otherwise called thoracolumbar outflow because, the preganglionic neurons are situated in lateral gray horns of thoracic and first two lumbar segments of Spinal cord. ~ Sympathetic division supplies smooth muscle fibres of all the visceral organs such as blood vessels,heart, lungs, glands, gastrointestinal organs etc,. ~ Allow body to function under stress. ~Flight or fight. ~ Primes body for intense skeletal muscle activity.

18. PARASYMPATHETIC DIVISION: ~It is otherwise called Craniosacral outflow because, the fibres of this division arise from the brain sacral segments of Spinal cord. ~Maintains functions ~Rest and digest. ~Counterbalances sympathetic functions.

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