Physiology and Pathophysiology (PHO221) Lecture 3 PDF

Physiology and Pathophysiology (PHO221) Lecture 3 Nervous System Prof Dr Noha Nassar Professor & Head...

Physiology and Pathophysiology (PHO221) Lecture 3 Nervous System Prof Dr Noha Nassar Professor & Head of Pharmacology Department Faculty of Pharmacy Department of Pharmacology & Toxicology MSA University Fall 2024 19-10-2024 Prof Dr Noha Nassar 1  Prof Dr Noha Nassar (G209) E-mail: [email protected] Monday 10:00 – 12:00 Wednesday 10:00 - 2:00 Dr Mai Moustafa (G22) E-mail: [email protected] Monday 10:00 – 12:00 Wednesday 10:00 - 2:00 Dr Omnia Farouk Email: [email protected] Tuesday from 10-12 am G008  Interactive methods 1- Explanations supported with Q&A to stimulate and elicit ideas and enhance the students’ engagement. 2-Videos and diagrams 3- Online quiz @Google sheet@ https://www.youtube.com/watch?v=RNLceVI8jcc https://www.youtube.com/watch?v=R1_B5_ytWSc https://www.youtube.com/watch?v=6O-0CVAgaEM https://www.youtube.com/watch?v=oa6rvUJlg7o https://www.youtube.com/watch?v=Ta_vWUsrjho https://www.youtube.com/watch?v=ezy2WJdRXgw https://www.youtube.com/watch?v=jZD_--i9vBM https://www.youtube.com/watch?v=Gsf9IB-wQdU https://www.youtube.com/watch?v=X4uuCgElLK8  References Textbook of Medical Physiology Guyton and Hall Textbook of Medical Physiology 19-10-2024 Prof Dr Noha Nassar 5 Nervous system Nervous system  Human Brain The cerebrum (pl.: cerebra), telencephalon or endbrain is the largest part of the brain, containing the cerebral cortex (of the two cerebral hemispheres) Several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In the human brain, the cerebrum is the uppermost region of the central nervous  Human Brain https://www.pharmacy180.com/article/the https://anatomyinfo.com/parts-of-the-brain/ brain-3551/  Human Brain Hippocampus: memory, learning, and emotion. Hypothalamus: helps in hormonal production that regulate heart rate, body temperature, hunger, and the sleep-wake cycle⇒ Homeostasis. Medulla: it's where the brain and spinal cord connect ⇒ transmitting signals between the spinal cord and brain + in controlling autonomic activities, such as heartbeat and respiration. Cerebellum: primarily responsible for muscle control, including balance and movement. https://anatomyinfo.com/parts-of-the-brain/  Human Brain https://www.pharmacy180.com/article/the- brain-3551/ 12  Human Brain The 12 cranial nerves include the: 1. Olfactory nerve ⇒ nose ⇒ smelling. 2. Optic nerve⇒ eye 3. Oculomotor nerve⇒ eye 4. Trochlear nerve⇒ eye 5. Trigeminal nerve⇒ face sensory 6. Abducens nerve⇒ rectus muscle of eye. 7. Facial nerve⇒face motor 8. Vestibulocochlear nerve⇒ ear 9. Glossopharyngeal nerve⇒ pharyngeal muscle 10.Vagus nerve⇒ motor ⇒ origin of parasympathetic nervous system + Sacral nerves are parasympathetic. 11.Accessory nerve⇒ pharynx, larynx, neck, shoulder muscles https://www.pharmacy180.com/article/the- brain-3551/ 12.Hypoglossal nerve⇒ tongue  Human Brain https://www.pharmacy180.com/article/the- brain-3551/ Spinal Cord Spinal Cord In the brain, grey matter is mainly found in the outer layers, while in the spinal cord it forms the core 'butterfly' shape. 19-10-2024 Prof Dr Noha Nassar 17  Neuron It is the structural and the functional unit of nervous system  Neuron Neurons=nerve cells =the structural units of the nervous system. Neurons are highly specialized cells that conduct messages in the form of nerve impulses from one part of the body to another. Neurons are typically large, complex cells. The plasma membrane of neurons is the site of electrical signaling. Dendrites: receive signals from other neurons Axons: transfer signals from one neuron to another Axon hillock: generate impulse in neuron Schwann Cells: produce myelin sheath. Neuron Neuron Neuron Neuron 19-10-2024 Prof Dr Noha Nassar 24 Neuron  Neuron 19-10-2024 Prof Dr Noha Nassar 26  Neuron 19-10-2024 Prof Dr Noha Nassar 27  Neuron Synapses Neurons communicate with one another at junctions called synapses. At a synapse, one neuron sends a message to a target neuron—another cell. Most synapses are chemical; these synapses communicate using chemical messengers. Other synapses are electrical; in these synapses, ions flow directly between cells. At a chemical synapse, an action potential triggers the presynaptic neuron to release neurotransmitters. These molecules bind to receptors on the postsynaptic cell and make it more or less likely to fire an action potential. Neuron 19-10-2024 Prof Dr Noha Nassar 30  Neuron Ability to respond to Excitability/Irritability stimuli Functional property of Ability to transmit an Conductivity impulse neurons Release of a chemical Secretion transmitter t the nerve ending Stimulus should be in All or none law adequate threshold strength Absolute Refractory Relative 19-10-2024 Prof Dr Noha Nassar 31  Neuron 19-10-2024 Prof Dr Nassar 32  Neuron 1. In myelinated nerve fibers, the velocity of impulse transmission is faster because the process of depolarization occurs only at the nodes of Ranveir and, therefore, it appears as if the impulses are jumping from one node to the successive node. 2. It acts as a protective sheath minimizing injury to the nerve fiber. 3. It acts as an insulator and prevents cross transmission of impulses from one fiber to the other in a mixed nerve 19-10-2024 Prof Dr Nassar 33  Neuron An action potential =nerve impulse: is a transient (short lasting) reversal in the membrane potential that is conducted down the length of the fiber. This occurs only in excitable cells: nerve and muscle fibers. ⇒ If you stimulate a liver cell, that reversal isn’t going to occur. https://antranik.org/what-is-an-action-potential- nerve-impulse/  Neuron Resting membrane potential: Difference in electrical potential across the plasma membrane when the cell is not stimulated or when the cell is in a state of relaxation. Differences between a cell’s internal and external electrical potential have traditionally been expressed as a percentage difference.  Neuron Causes of resting membrane potential : Increased concentration of Na+ outside. Leak of intracellular K+ to outside more than Na+ leak inside The presence of intracellular proteins carrying negative charges Na/K pump: it is the pump which pump 3 Na + ions outside the neuron and pump 2 K+ ions inside the cell  Neuron https://www.pharmacy180.com/article/cell-membrane-potential-3544/  Neuron Depolarization Sodium channels open and influx of Na Repolarization: Potassium channels open and K effluxes the cell Hyperpolarization (Under shoot) occur due to slow closure of K channels increased K efflux and the membrane becomes more negative  Neuron https://antranik.org/what-is-an-action-potential- nerve-impulse/  Neuron Refractory period A- Absolute refractory period : During the phase of depolarization and early part of repolarization. Due to opened Na + channels inactive “It is impossible to generate another action potential” B- Relative refractory period: During late part of repolarization. Due to Na+ channels are inactivated and can be activated again “Action potential can be generated only in  Neuron https://www.youtube.com/watch?v=xACXraaj hrw  Neuron Different state of sodium channels during the action potential 19-10-2024 Prof Dr Noha Nassar 43 19-10-2024 Prof Dr Noha Nassar 44  Spinal Cord reflexes A reflex is an involuntary and nearly instantaneous movement in response to a stimulus. The reflex is an automatic response to a stimulus that does not receive or need conscious thought as it occurs through a reflex arc. Reflex arcs act on an impulse before that impulse reaches the brain  Spinal Cord reflexes Most reflex arcs involve only three neurons. The stimulus, such as a needle stick, stimulates the pain receptors of the skin, which initiate an impulse in a sensory neuron. This travels to the spinal cord where it passes, by means of a synapse, to a connecting neuron called the relay neuron situated in the spinal cord. The relay neuron in turn makes a synapse with one or more motor neurons that transmit the impulse to the muscles of the limb causing them to contract and pull away from the sharp object. Reflexes do not require involvement of the brain, although in some cases the brain can prevent reflex action.  Spinal Cord reflexes A reflex action, also known as a reflex is an involuntary and nearly instantaneous movement in response to stimulus. When a person accidentally touches a hot object, they automatically jerk their hand away without thinking. A reflex does not require any thought input. The path taken by the nerve impulses in a reflex is called a reflex arc. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This characteristic allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain, although the brain will receive sensory input while the reflex action occurs. What is the reflex arc Spinal Cord reflexes  What is the reflex arc 19-10-2024 Prof Dr Noha Nassar 50 Reflex arc  Guess the role?!! Astrocytes BBB Ependymal CSF cells Oligodendrocytes Myelination Microglia Brain immune cells Scan me =) Faculty of Pharmacy 19-10-2024 Prof Dr Noha Nassar 56