Nervous system of Human Beings Anatomy and physiology-1.pptx

Physiology 1st year pharm D

1. Nervous system The organised network of nerve tissue in the body is called nervous system It includes : Central nervous system (CNS) and peripheral nervous system ( pns ) Central nervous system includes: Brain and spinal cord. Peripheral nervous system: nerves that extends from spinal cord to rest of body.

2. CELLS AND TISSUES OF NERVOUS SYSTEM CELLS: 1.Neurons 2.Nerve cells TISSUES: 1.Neurons 2.Neuroglia NEURONS : each Neuron consist of a cell body and its processes one axon and many dendrites. Neurons are commonly referred to as Nerve cells. bundle of axon Bound together are called nerves. Neuron generate and transmit electrical impulse called as action potential. Action potential can be initiated In response to stimuli from 1.outside the body. For example: touch. 2.Inside the body for example: change in concentration of carbon dioxide in blood alters respiration

3. CELL BOBIES: Cell bodies form the grey matter of nervous system and are found at the periphery of the brain and in the centre of spinal cord. Group of cell bodies are called nuclei in the centre nervous system and ganglia in the periphere nervous system Axons and dendrites: Axons and dendrites are extensions of cell bodies and form the white matter of nervous system. Axones are found deep in the brain and in groups called tracts at the periphery of the spinal cord they are referred to as nerve fibers outside the brain and spinal cord. Axons: Each nerve cell has only one axon and axons carry impulses away from the cell body and usually much longer than the dendrites sometimes as longer as 100 cm. Dendrites: These are the many short processes that received and carry incoming action potentials toward the cell bodies. They have the same structure as axons but are usually shorter and branching. They also transmit impulses.

4. CSF is a clear, colorless fluid that surrounds the brain and spinal cord, providing cushioning and protection. It is produced by the choroid plexus in the ventricles of the brain and circulates through the subarachnoid space. CSF(cerebrospinal) Functions of CSF: . 1.Cushioning: Protects the brain and spinal cord from mechanical damage. 2. Nutrition: Supplies nutrients and oxygen to the central nervous system. 3. Waste removal: Removes waste products from the central nervous system. 4. Pressure regulation: Helps regulate intracranial

5. Meninges are protective membranes that cover the brain and spinal cord. There are three layers of meninges : Dura mater : The outermost layer, attached to the skull and spinal canal . Arachnoid mater: The middle layer, surrounding the subarachnoid space . Pia mater: The innermost layer, closely adhering to the brain and spinal cord . Functions of meninges : 1. Protection: Shields the brain and spinal cord from injury . 2 . Support: Provides a framework for the central nervous system . 3 . Circulation for the circulation of. Meninges

6. Relationship between CSF and meninges : CSF production: The choroid plexus in the ventricles produces CSF, which flows through the subarachnoid space between the arachnoid and pia mater . CSF circulation: CSF circulates through the subarachnoid space, eventually returning to the bloodstream through the arachnoid villi . Meningeal protection: The meninges protect the CSF and the central nervous system from injury and infection. Dysfunction or damage to the CSF and meninges 1 . Meningitis: Inflammation of the meninges, often due to infection . 2 . Hydrocephalus: Accumulation of CSF, leading to increased intracranial pressure . 3 . Subarachnoid hemorrhage: Bleeding into the subarachnoid space, often due to aneurysm rupture.

7. ACTION POTENTIAL Action potential is a rapid, temporary change in the electrical charge across a neuron's cell membrane. It's generated by a complex interplay of ion channels, pumps, and electrochemical gradients Phases of the action potential Resting potential: the neuron is at rest, with a negative charge (-70mv) Depolarization: sodium channels open, allowing positively charged sodium ions to rush in, reducing the negative charge. Threshold: if depolarization reaches -55mv, the action potential is triggered. Rising phase: more sodium channels open, and the electrical charge becomes positive (+30mv). Falling phase: potassium channels open, allowing positively charged potassium ions to leave, returning the charge to negative. Repolarization: the neuron returns to its resting state (-70mv). Refractory period: the neuron is unable to generate another action potential for a brief time.

8. Neurotransmitter is a chemical substance that act as mediator for transmission of impulse from one neuron to another neuron through synapse Neurotransmitter are classified into two types Excitatory neurotransmitter Inhibitory neurotransmitter Excitatory neurotransmitter is a chemical substance which is responsible for conduction of impulse from presynaptic neuron to postsynaptic neuron Inhibitory neurotransmitter is a chemical substance which inhibits the conduction of impulse from presynaptic neurone to postsynaptic neuron Example Common excitatory neurotransmitters is acetyl choline noradrenaline common inhibitory neurotransmitter are GABA and Dopamine

9. Electrical synapse is the synapse in which physiological continuity between the presynaptic and postsynaptic neuron is provided by gap junction between two neuron there is a direct exchange of fine between two neurons through a gap junction because of reason action potential reaching to the terminal portion of presynaptic on enter the postsynaptic neuron : Important feature of electrical synapse is that the synaptic delay is very less the direct flow of current moreover impulse is transmitted is either direction through the electrical synapse This type of transmission occur in some of cardiac muscles fibre smooth muscles fibre intestine and epithelial cell

10. Chemical synapse is the junction between a nerve fibre and a muscles fibre are between two nerve fibre through a signal are transmitted by the release of electrical transmitter In the chemical synapse there is a no continuity between the two neuron because the presence of space called synaptic cleft*between two neuron action potential reaching the presynaptic terminal cause release of neurotransmitter substances from vesicles to the terminal neurotransmitter reach the post synthetic neuron through synaptic cleft and cause the production of potential changes

11. Nerves are specialized bundles of cells, called neurons, that transmit and receive electrical and chemical signals in the body. Layer of connective tissue of nerve 1. Endoneurium Innermost layer surrounding individual nerve fibre i.e optic nerve fiber 2. Perineurium Middle layer surrounding group of nerve fibre i.e radial nerve 3 . Epineurium Outermost layer surrounding the numbers of bundle of nerve fibers i.e sciatic

12. Types of nerve Sensory nerve Carry information from body to spinal cord Receptors 1. Somatic cutaneous or common sensesOriginate from skin i.e pain touch heat and cold 2 . Proprioceptor senses Originate in muscle and joints 3 . Special senses They are site,hearing , balance, smell and taste Autonomic apparent nerve These originate in internal organ glands and tissue i.e baroreceptors, chemoreceptor Motor are efferent nerve Originate in brain spinal cord and autonomic ganglia Types 1.Somatic nerves 2 . Autonomic nerves 4 . Mixed nerve Mixed nerves are nerve that contain both sensory and motor nerve Examples of mixed nerves include:- Sciatic nerve

13. Neuroglia Neuroglia is a supporting cell of the nervous system It is not excitable (don't tansmit impulses) Location CNS and PNS Types In CNS Astrocytes Ependymal cell Oligodendrocytes Microglia IN PNS Schwan cells Satellite cell

14. Astrocytes It is a star shaped neuroglial cell present in all part of brain Types Fibrous astrocytes Protoplasmic astrocytes Fibrous astrocytes Present in white matter it's is important role in the formation of blood brian barrier by sending processes to the blood vessels of brian Protoplasmic astrocytes Present in gray matter the process of neuroglia run between nerve cell bodies Ependymal cells Epe means epithelium Present only in CNS The cells form the epithelial lining of the brain central canal of the spinal cord.

15. Microglia micro means small smallest glial cells that drived from monocytes present only CNS Act as macrophages to destroy microorganisms Oligodendrocytes It is a smaller than astrocyte It is only present in CNS Oligodendrocytes form and maintain myelin sheath in CNS Schwan Cells it is a major glial cells of PNS It is only present in PNS Schwan cells are formation of myelin sheath Play an important role in nerve the generation Satellite cells Present on the exterior surface of neurons in PNS Provide physical sport to neurone maintain homeostasis at PNS

16. Response of nervous tissue to injury neurons reach maturity after birth and Cannot replace damaged to neurone lead Rapid necrosis with acute failure function or slow atrophy. this changes may result from hypoxia and anoxia, nutritional Defficiency , poisons , trauma, infection, aging, hypoglycemia Peripheral nerve regeneration is the process by which damaged peripheral nerve fibers regrow and repair themselves. Here's an overview of the process in anatomy : Degeneration : The damaged nerve fiber degenerates, and the myelin sheath breaks down . Clearing: Schwann cells and macrophages remove debris . Proliferation: Schwann cells proliferate, forming a regeneration tube ( Bungner's band ). Axonal sprouting: The proximal end of the damaged nerve fiber sprouts new axons 5 Axonal growth: The new axons grow through the regeneration tube . 6.Remyelination : Schwann cells remyelinate the new axons . 7. Reinnervation : The regenerated nerve fibers reconnect with target muscles or sensory receptors .

17. Neuroglial damage Astrocytes : when these cell damage thier process multiple Forming a mesh which inhibits the growth of CNS neurons Oligodendrocytes : lead the demyelinating disease such as sclerosis Microglia : they lead to Alzheimer's and stroke disease