Nervous System Lecture Notes PDF

Nervous System Dr. Pallav Sengupta Assistant Professor, Physiology College of Medicine October 4, 2024 www.gmu.ac.ae COLLEGE OF MEDICINE Learning objectives On completion of...

Nervous System Dr. Pallav Sengupta Assistant Professor, Physiology College of Medicine October 4, 2024 www.gmu.ac.ae COLLEGE OF MEDICINE Learning objectives On completion of this unit, the student will be able to: Discuss the organization of nervous system Explain the structures and functions of neuron and neuroglial cells Describe the various phases of nerve action potential Discuss the role of neurotransmitters Describe the functions of different neural centers Characteristics of nervous system neural response > - fast first system The nervous system receives information from different senses simultaneously. The nervous system integrates information. The nervous system is very fast. It can receive information, integrate it, and produce a response within tenths of a second. The nervous system can initiate specific responses, including muscle contraction, glandular secretion, and even conscious thought and emotions.  Divisions of the Nervous System central nervous system. Peripheral nervous system pairs) 3 biometricala cranial nerve (12 pairs) humans - (31 - Spinal nerves · from to brain sensory peripheral order from nerves t higher centertor , -l what we need do? superficial (kinesthetic) inside the body. + special controlled by autonomic. system ANS motors we cannot visceral sensory + control (involuntary) => autonomic heres system. (ANS)  Neuron > - nerve cells Each neuron contains: - Cell body with nucleus, mitochondria , other cell organelles - Dendrites : fibers that receive messages from other neurons - Axons : fibers that send messages to other neurons Neurons do NOT touch; there is a gap between them called a synapse Messages are sent across the synapses by special chemicals called neurotransmitters canbe excitoryorinhibitor a r inside spinal cord bring into to higher center found only in refine, eye everywhere climbs) whitish under compound microscope velocity - fastest propogation , higher ~ made of cholesterol matter grey under microscope grey ,  Neuroglial neurons protect cells (neuronsare blacInt restricted) CNS PNS Microglia Ependymal Astrocytes Oligodenrocytes cells cells Neuroglial cells support and protect neurons. Do not generate or transmit impulse Schwann Satellite Schwann cells (in the PNS) – produce fatty cells cells insulating material – myelin  Membrane Potential outside cell [Na+] is higher Na+-K+ pump maintains resting potential : The Na+-K+ pump actively transports 3 Na+ ions out of the cell in exchange for 2 K+ ions. Most of the K+ leaks out again. However, the inward leak of sodium is so slow that the pump effectively is able to exclude most Na+ from the cell. The exclusion of positive ions (Na+) from the cell creates a voltage difference across the cell membrane – membrane potential a neuron capable of action potentials but not generating one at the moment, the normal membrane potential at rest is its resting (membrane) potential. The resting potential of a neuron is about −70 millivolts (mV). (-ve) ↳Internal voltage at rest becomes (tue) start bullet points. When stimulated the  response triggered. influx , efflux. generate current a ·  Action Potential A neuron’s resting potential of about -70mV is maintained by the constant action of the sodium-potassium pump. Impulses arriving from other neurons can cause small local changes in the neuron’s membrane potential called graded potentials. The sum of graded potential is sufficiently strong to reach a certain triggering membrane voltage called the threshold, an action potential results. An action potential is a sudden, temporary reversal of the voltage difference across the cell membrane. An action potential involves 3 events: depolarization, repolarization and reestablishment of the resulting potential. Depolarization Sodium channels open Sodium diffuses into the cytoplasm of axon Membrane depolarizes (meaning membrane potential shifts from negative (-70mV) to positive (+ 30mV) Repolarization Sodium channels close Potassium channels open Potassium diffuses out of axon Loss of positive ions from cell – repolarization (inside of axon again negative) Re-establishment of resting potential Potassium channels close: After a brief hyperpolarization caused by a delay in the full closure of potassium channels, the membrane potential returns to its normal resting value  Neurotransmitter chemical used to transmit from cell to cell (excitory or inhibitory) signals.. Once an action potential reaches the axon terminals of a neuron, the information inherent in it must be converted to another form for transmitting to its target (muscle cell, gland cell, or another neuron). the action potential causes the release of a chemical that crosses a specialized junction between the two cells called a synapse. This chemical substance is called a neurotransmitter because it transmits a signal from a neuron to its target. The entire process of transmission from a neuron to its target is called synaptic transmission.  Actions of neurotransmitter Neurotransmitters exert excitatory or inhibitory effects excitatory inhibitory. know pure  CNS (Central Nervous System) The central nervous system (CNS) is made up of the brain and spinal cord. It is one of 2 parts of the nervous system. The other part is the peripheral nervous system, which consists of nerves that connect the brain and spinal cord to the rest of the body CNS is protected by bone. The brain is encased in the skull, the spinal cord is enclosed in a hollow channel within the vertebrae. CNS is enclosed by three membranes of connective tissue, called meninges, the dura mater, the arachnoid, and the pia mater. These three meninges protect the neurons of the CNS and the blood vessels. CNS is bathed in cerebrospinal fluid, which fills the space between the arachnoid and the pia mater. Act as a liquid shock absorber around the brain and spinal cord and also tends to isolate the central nervous system from infections. Functional barrier between blood and brain is called the blood-brain barrier.  Lobes of the Brain The brain is a complex organ that controls thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger and every process that regulates our body. Together, the brain and spinal cord that extends from it make up the central nervous system, or CNS. 2 connected by corpus callesum nemisphere Cerebrium connection. contradictory Frontal · Parietal limbic cortex. Occipital Temporal * Note: Occasionally, the Insula is considered the fifth lobe. It is located deep to the Temporal Lobe.  Parts of Brain Cerebrum : largest part of human brain Responsible for: - Thought - Language - Senses - Memory - Voluntary movement  Parts of Brain Cerebellum : at base of brain - rectifies movement -Responsible for: contracting vs. relaxing · - Muscle coordination - Balance - Posture  Parts of Brain Brain Stem : connects brain to spinal cord -Responsible for: - Breathing - Swallowing - Heartbeat - Blood pressure Center cardiac respiratorya  Spinal cord > - passage of nerves. The spinal cord extends downward from the base of your brain. It's made up of nerve cells and groups of nerves that carry messages between your brain and the rest of your body. The spinal cord extends from the base of the skull to the area of about the second lumbar vertebra, or about 17 inches It is protected by the vertebral column. The outer portions of the spinal cord consist primarily of bundles of axons, which in the CNS are called nerve tracts rather than nerves. These axons are generally myelinated, giving them a whitish appearance, the areas of the cord occupied by these ascending (sensory) and descending (motor) nerve tracts are called white matter. Neurons of the PNS enter and leave the spinal cord at regular intervals via the dorsal (sensory) and ventral (motor) horns that fuse to form spinal nerves. Near the center of the spinal cord is a region occupied primarily by the cell bodies, dendrites, and axons of neurons of the CNS, and also neuroglial cells. These structures are not myelinated, so the area they occupy is referred to as gray matter. Within the gray matter, sensory and motor neurons synapse with neurons of the CNS that transmit signals up the spinal cord to the brain.  Spinal cord Responsible for: Conducting impulses between the brain and the rest of the body  Peripheral Nervous System (PNS) PNS comprises of spinal nerves (31 pairs) and cranial nerves (12 pairs)  Disorders of the Nervous System Parkinson’s Disease degeneration tremors due to neural. > - It is a motor disorder occurring due to neurodegeneration in substantia nigra (part of basal ganglia). movemen t helps to start/stop Alzheimer’s Disease of Cerebral cortex 1 It is a neurodegenerative disorder that results in memory loss. Epilepsy Epilepsy is a common condition that affects the brain and causes frequent seizures. Seizures are bursts of electrical activity in the brain that temporarily affect how it works. Paralysis Loss of sensation and movement of part of the body due to an injury of the spinal cord or brain References 1. Johnson D Michael.,Human Biology, 8th edition.Pearson education limited 2017.ISBN: 978-1-292-16627-8