PHY261 Electrical Properties of Multipolar Neuron Lecture Notes PDF

PHY261 Faculty of Science Electrical Properties of Multipolar neuron Dr Ayman Sobhi 10/8/2023 1 Nature and Subject of Biophysics  The subjects of biophysics are the physical principles underlying all processes of living systems.  Bioph...

PHY261 Faculty of Science Electrical Properties of Multipolar neuron Dr Ayman Sobhi 10/8/2023 1 Nature and Subject of Biophysics  The subjects of biophysics are the physical principles underlying all processes of living systems.  Biophysics is an interdisciplinary science somewhere between biology and physics, as may be concluded from its name, and is furthermore connected with other disciplines, such as mathematics, physical chemistry, and biochemistry. The term "biophysics" was first used in 1892 by Karl Pearson in his book The Grammar of Science. 10/8/2023 2 Bio physics Neuron Forces in Circulatory Hearing system body 10/8/2023 3 10/8/2023 4  Lecture one Nervous system introduction Lecture Three Structure of Neuron Potential difference Myelinated vs Unmyelinated Resting Potential Neuron classification Electrical local Potential Changes properties of Ion Movements during Action Potentials neuron Refractory Period Lecture Two Impulse Processing Cell Membranes and Ion Distributions Model of Electrical Conduction along an Axon Types of Ion channels Introduction to resistance Introduction to capacitor Ions Transport Introduction to potential Passive transport Diffusion Osmosis Facilitated diffusion Active transport Membrane potential Lecture Outline What are you going to learn today ? Electrical properties of neuron Lecture one Nervous system introduction Structure of Neuron Myelinated vs Unmyelinated Neuron classification 10/8/2023 6  what do you think about that gif ? Video 0 Neurons are the basic unit of the nervous system. Neurons are responsible for sending, receiving, 10/8/2023 and interpreting information from all parts of the body. 7 10/8/2023 8 1- nervous system introduction 10/8/2023 9 1- nervous system introduction The somatic nervous system, or voluntary nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles. The autonomic system is the part of the peripheral nervous system that is responsible for regulating involuntary body functions, such as heartbeat, blood flow, breathing, and digestion. 10/8/2023 10 1- nervous system introduction Parasympathetic nervous system: This part of the autonomic nervous system helps maintain normal body functions. This division also performs such tasks as controlling the bladder, slowing heart rate, and constricting eye pupils. Sympathetic nervous system: This division regulates the flight-or-fight responses. The sympathetic system also performs such tasks as relaxing the bladder, speeding up heart rate, and dilating eye pupils. 10/8/2023 11 For Reading 10/8/2023 12 2- Structure of multipolar Neuron Cell Body Dendrites Axon Axon terminal Synaptic 10/8/2023 Myelin Sheaths 13 2- Structure of multipolar Neuron Cell Body The cell body (soma) is the metabolic center of the neuron. contains the nucleus and ribosomes and thus has the genetic information and machinery necessary for protein synthesis. 10/8/2023 14 2- Structure of multipolar Neuron Dendrites The armlike fibers that convey incoming messages (electrical signals) toward the cell body are dendrites. Neurons may have hundreds of the branching dendrites, depending on the neuron type, but each neuron has only one axon, which arises from a conelike region of the cell body called the axon hillock. Knoblike outgrowths called dendritic spines increase the surface area of dendrites still further. Thus, the structure of dendrites in the CNS increases a cell’s capacity to receive signals from many other neurons. 10/8/2023 15 2- Structure of multipolar Neuron Axon The axon is a long process that extends from the cell body and carries outgoing signals to its target cells. In humans, axons range in length from a few microns to over a meter. The region of the axon that arises from the cell body is known as the axon hillock (or initial segment). The axon hillock is the location where, in most neurons, propagated electrical signals are generated. These signals then propagate away from the cell body along the axon. The axon may have branches, called collaterals. 10/8/2023 16 2- Structure of multipolar Neuron Axon Electrical cable 10/8/2023 17 2- Structure of multipolar Neuron Axon terminal All axons branch profusely ‫ ﺑﻛﺛرة‬at their terminal end, forming hundreds to thousands of axon terminals. These terminals contain hundreds of tiny vesicles, or membranous sacs, that contain chemicals called neurotransmitters. As we said, axons transmit nerve impulses away from the cell body. When these impulses reach the axon terminals, they stimulate the release of neurotransmitters into the extracellular gap to the cell opposite the terminal. 10/8/2023 18 2- Structure of multipolar Neuron Synaptic Each axon terminal is separated from the next neuron by a tiny gap called the synaptic cleft. Such a functional junction is called a synapse (syn = to clasp or join). Although they are close, neurons never actually touch other neurons. Video 1 10/8/2023 19 2- Structure of multipolar Neuron Myelin Sheaths Most long nerve fibers are covered with a whitish, fatty material called myelin, which has a waxy appearance. Myelin protects, insulates the fibers and increases the transmission rate of nerve impulses. Axons are myelinated by Schwann cells. These cells wrap themselves around the axon in a jelly-roll fashion. myelin sheath has gaps, or indentations, called nodes of Ranvier, at regular intervals. 10/8/2023 20 2- Structure of multipolar Neuron Homeostatic Imbalance The importance of the myelin insulation to nerve transmission is best illustrated by observing what happens when myelin is not there. In people with ‫اﻟﺗﺻﻠب اﻟﻣﺗﻌدد‬multiple sclerosis (MS), the myelin sheaths around the fibers are gradually destroyed, converted to hardened sheaths called sclerosis. As this happens, the electrical current is short-circuited. The affected person may have visual and speech disturbances, lose the ability to control his or her muscles, and become increasingly disabled. Multiple sclerosis is an autoimmune disease in which a protein component of the sheath is attacked. As yet there is no cure, but injections of interferon (a hormonelike substance released by some immune cells) appear to hold the symptoms at bay and provide some relief 10/8/2023 21 3-Myelinated vs Unmyelinated Video 2 Homeostatic Imbalance 10/8/2023 22  Video 3 3-Myelinated vs Unmyelinated 10/8/2023 23 3-Myelinated vs Unmyelinated 10/8/2023 24 4- Neuron Classification Neurons may be classified either according to how they function or according to their structure. Functional Classification 10/8/2023 25 4- Neuron Classification Functional Classification Functional classification groups neurons according to the direction the nerve impulse is traveling relative to the CNS. On this basis, there are sensory, motor, and association neurons (interneurons) Sensory, or afferent ‫ اﻟوارد‬neurons Neurons carrying impulses from sensory receptors (in the internal organs or the skin) to the CNS are sensory, or afferent, neurons. Sensory neurons keep us informed about what is happening both inside and outside the body. Motor, or efferent ‫ اﻟﺻﺎدر‬neurons Neurons carrying impulses from the CNS to the viscera and/or muscles and glands are motor, or efferent, neurons. The cell bodies of motor neurons are usually located in the CNS. interneurons, or association neurons They connect the motor and sensory neurons in neural pathways. Their cell bodies are typically located in the CNS 10/8/2023 26 4- Neuron Classification Functional Classification 10/8/2023 27 10/8/2023 28 4- Neuron Classification Structural Classification Structural Classifications based on the number of processes extending from the cell body Multipolar neuron Bipolar neuron Unipolar neuron 10/8/2023 29 4- Neuron Classification Structural Classification Structural Classifications based on the number of processes extending from the cell body Multipolar neuron All motor neurons are multipolar 10/8/2023 30 4- Neuron Classification Structural Classification Structural Classifications based on the number of processes extending from the cell body Bipolar neuron Neurons with two processes—an axon and a dendrite—are called bipolar neurons. Bipolar neurons are rare in adults, found only in some special sense organs (eye, nose), where they act in sensory processing as receptor cells. 10/8/2023 31 4- Neuron Classification Structural Classification Structural Classifications based on the number of processes extending from the cell body Unipolar neuron Unipolar neurons have a single process emerging from the cell body. 10/8/2023 32 QUOTES 10/8/2023 34