Introduction to the nervous system

This presentation based on a broad overview to the human central nervous system focusing over the parts of the system, different cell types present in the system, and special terminology used in the system.

1. By Dr. SAHAR HAFEEZ [email protected] INTRODUCTION TO THE NERVOUS SYSTEM

2. Learning objectives The students should be able; Demonstrate an understanding towards the concept of major divisions of the Nervous system. Enlist different components of the Central, Peripheral , & Autonomic Nervous systems. Enlist the names of main cells in the Nervous tissue. Enlist different parts of the Brain. Understand the concept of General vs Special and Somatic vs Visceral. Define the terms Ganglion, White matter, & Grey Matter.

3. “ The human nervous system is a control system which regulates the body’s response to internal & external stimuli ” It is composed of two components; Central Peripheral

4. Central Nervous System (CNS) Definition: Unpaired, bilaterally symmetrical structures extending along the longitudinal axis of the midsagittal plane of body. Structures arising directly from the neural tube. Includes: Brain Spinal cord

5. Peripheral Nervous System (PNS) Definition: Made up of transmission pathways, connects the central nervous system (CNS) to sensory organs, other organs of the body, muscles, blood vessels and glands. Afferent (sensory) pathways : Carry information to the CNS. Efferent (motor) pathways : Carry information from the CNS.

6. Autonomic Nervous System May be considered a subdivision of the PNS. Entirely motor. Innervates smooth muscle and glands (viscera). Has two subdivisions; Sympathetic sys . (fight or flight) Parasympathetic sys . (feed or breed)

7. ANATOMICAL ORGANIZATION of the NERVOUS SYSTEM Nervous System CNS PNS ANS BRAIN SPINAL CORD CRANIAL NERVES SPINAL NERVES SYMPATHETIC PARA- SYMPATHETIC

8. Cell types present in the Nervous System Nervous tissue is made up of 2 types of cells; Neurons (structural & functional unit) Neuroglia (Supporting cells)

9. Neurons The neurons are the main structural and functional unit of the Nervous system making up the brain, spinal cord, and nerves. Human body contains about 200 billion neurons. Almost half of them are located in the brain. They are held together & supported by another type of tissue, Neuroglia= Nerve glue .

10. The human brain is a soft, shiny, grayish white, mushroom-shaped structure encased within the skull. It is composed of up to one trillion nerve cells. One hundred billion of these are neurons, and the remainder are the supporting neuroglia. There are hundreds of elevations (Gyri) and depressions (Sulci) on the surface of brain The Brain

11. Anatomical Parts of the brain Brain has three major parts; Cerebrum (Forebrain) Brainstem Midbrain Pons Medulla Cerebellum (Hindbrain)

12. The brain is protected by the skull and by three membranes called the meninges . The outermost membrane is known as the Dura mater , the middle as the Arachnoid mater , and the innermost as the Pia mater . Also protecting the brain is cerebrospinal fluid (CSF ) a liquid that circulates between the arachnoid and pia mater. Protection of Brain

13. The spinal cord, a glistening white rope, is a continuation of the brain stem. It transmits impulses to and from the brain and controls some reflex actions. The vertebral column or backbone encloses the spinal cord. the spinal cord is also cushioned and protected by meninges. The thirty-one (31) pairs of spinal nerves exit the vertebral column to serve the areas of the body. The Spinal Cord

14. General VS Special If a nervous element is found throughout the body is said to be ‘ general’ A nervous element restricted to just one part of the body is said to be ‘ special .’ Examples: senses of pain, touch, temperature are present everywhere. Their receptors are present throughout the body (general) Sense of Vision, hearing, taste, smell can only be felt by specific organs. Their receptors are present only in those organs like eyes, ear, tongue, nose (special).

15. Somatic vs Visceral : Somatic nerves/ innervation are related to the body wall (soma=body). Thus somatic innervation means the supply to the skin, muscles, & joints. Visceral nerves/innervation are related to the organs (viscera=organs). Thus visceral innervation means supply to the organ system including glands.

16. Other elements of nervous system Ganglia: a button-shaped structure containing number of nerve cell bodies outside the CNS, often found in the pathways of peripheral nerves. White matter: Areas of CNS mostly made up of Myelinated axons (as the myelin is white colored) Grey matter : Areas of the CNS mostly made up of somas/bodies of neurons.