Anatomy Notebook PDF

Anatomy Notebook  September 10, 2024 Lecture 1: Cells & Tissues Cellular Structure: - Plasma membrane: § It is the outermost struc...

Anatomy Notebook  September 10, 2024 Lecture 1: Cells & Tissues Cellular Structure: - Plasma membrane: § It is the outermost structure enveloping the cell, often referred to as “bag” that contains the cell’s components. It is a double layer of lipids, specifically phospholipids with polar head and long fatty acid chains. § The plasma membrane contains: # Phospholipids: The main component of the plasma membrane, providing structure and fluidity. # Cholesterol: A molecule that helps maintain the fluidity of the plasma membrane. # Integral Membrane Proteins: Proteins embedded in the plasma membrane that span the outside and inside of the cell, performing various functions such as: - Structural functions: Providing mechanical support and shape to the cell. - Signalling Functions: Transmitting signals from outside the cell to the inside. Cytoplasm: - It is the region enclosed by the plasma membrane, consisting of: § Cytosol: A jelly-like matrix that organelles are embedded in, containing solutes, nutrients, and waste products. § Organelles: Specialized structures within the cell that perform specific functions. Types of Cellular Organelles and their functions: - Mitochondria: Generates ATP (cellular energy currency) through cellular respiration. - Ribosomes: Translates messenger RNA (mRNA) into protein. - Rough Endoplasmic Reticulum (RER): Synthesizes proteins and lipids, and transports them to other parts of the cell. Cellular Functions: - Cell signalling: The process by which cells communicate with each other and their environment through signals and receptors. - Cell movement: The ability of cells to move and change shape, often involving the cytoskeleton and transmembrane proteins. Cell Diversity: - Cell specialization: The process by which cells develop specific features and functions to perform specific tasks. - Cellular heterogeneity: The presence of different cell types within a population, even when they appear homogeneous under a microscope. Lecture 1: Cells & Tissues September 10, 2024 Endoplasmic Reticulum (ER): - The ER is a network of membranous tubules and cisternae found throughout the cytoplasm of eukaryotic cells. - It is divided into two types: # Rough ER: § has ribosomes attached to its surface, which are responsible for protein system. § Functions: - Protein synthesis. - Protein folding and modification - Lipid Synthesis § “The rough ER is like a sorting house or distribution centre within the cell, taking cargo from the ER and modifying and absorbing it into the cell.” # Smooth ER: § lacks ribosomes and is involved in lipid synthesis and detoxification. § Functions: - Lipid synthesis (e.g., cholesterol) - Detoxification - Storage of lipids and proteins Golgi Apparatus: - It is a complex organelle responsible for protein modification, sorting, and packaging. - Functions: § Protein modification (e.g., glycosylation) § Protein sorting and packaging § Lipid synthesis Microtubules and Cilia: - Microtubules: dynamic structures composed of tubulin proteins that provide structural support and shape to cells. - Cilia: microtubule- based organelles that project from the cell surface and are involved in movement and sensory reception. - Functions: § Movement (e.g., flagella in sperm cells) § Sensory reception (e.g., olfactory receptors) Nucleus: - Nucleus: the control center of the cell, containing most of the cell’s genetic material. - Nuclear Envelope: a double membrane structure that surrounds the nucleus and regulates the movement of materials in and out. - Nucleolus: a region within the nucleus where ribosome synthesis occurs. Lecture 1: Cells & Tissues September 10, 2024 Epithelial Tissue: - This is a type of tissue that forms the lining of organs and glands. - Characteristics: § Composed of cells: # Epithelial tissue is made up of cells that are closely packed together. § Avascular: # Epithelial tissue lacks blood vessels and relies on diffusion for nutrients and waste exchange. § Polarized: # Epithelial cells have distinct apical and basal surfaces that perform different functions. § Tight Junctions: # Epithelial cells are connected by tight junctions that form a barrier and maintain tissue integrity. Cell Junctions: - Specialized junctions that connect epithelial cells and form a barrier. - Functions: § Barrier function § Maintain of tissue integrity § Definition of apical and basal surfaces. Cellular Polarity: - refers to the asymmetrical distribution of cellular components, such as organelles and proteins, within a cell. - In epithelial cells, polarity is established by the presence of specialized junctions and the basement membrane. Basement Membrane: - It is a thin layer of extracellular matrix that separates the epithelial cells from the underlying connective tissue. - It provides a physical scaffold for the cells to attach to and helps filter substances. - Functions: § Physical Scaffolds: provides surface for cells to attach to. § Filtration: Filters substances from outside in or inside out. Epithelial Cell Regeneration: - Epithelial Cells have high regenerative capacity, meaning they can quickly replace damaged or lost cells. This is important for many the integrity of the epithelial layer and preventing damage to underlying issues. Cancer and Epithelial Cells: - Most cancers that arise in the clinic are carcinoma, which are tumors that originate from epithelial cells. The loss of cellular polarity and the disruption of cell-cell junctions can contribute to the development of cancer. Lecture 1: Cells & Tissues September 10, 2024 Classification of Epithelial Tissue: # Epithelial tissue can be classified on two criteria: § Cell Shape: - Epithelial cells come in three main shapes: Squamous Cells: flat, scale-like shape Cuboidal Cells: cube-shaped cells Columnar Cells: tall, columned-shaped cells § Number of Layers: - Epithelial tissue can be classified as: Simple epithelium: one layer of cells Stratified epithelium: two or more layers of cells. Classification of Stratified Epithelium: - When classifying stratified epithelium, the apical most cell type is used to determine the classification. - Classifications: § Stratified Squamous Epithelium: Multiple layers of cells with squamous cells on the apical surface. § Stratified Cuboidal Epithelium: Multiple layers of cells with cuboidal cells on the apical surface. § Stratified Columnar Epithelium: Multiple layers of cells with columnar cells on the apical surface. Examples of Epithelial Layers: - Simple Squamous Epithelium: # Characteristics: § Fraglile, Thin Cells, Single layer, Minimal barrier or filtration # Location: § Alveoli in the lungs § Blood Vessels and heart chambers ( endothelial cells) # Function: § Gas exchange in the lungs § Lubrication in serous cavities - Specialized Squamous Epithelium: # Endothelial cells: specialized squamous cells that line blood vessels and heart chambers. # Mesothelial cells: specialized squamous cells that line serous cavities and secrete lubricating fluid.  Lecture 1: Cells & Tissues September 10, 2024 Simple Epithelium: - It is a type of epithelial tissue that consist of a single layer of cells. - There are several types of simple epithelium, each with distinct characteristics and functions: § Mesothelium: A type of simple epithelium that lines the serous membranes, which secrete a lubricating fluid that reduces friction between organs. Location: serous membranes, such as the pleura, pericardium, and peritoneum. Function: Secretion of lubricating fluid. § Cubodial Epithelium: A type of simple epithelium that consists of cube-shaped cells, often involved in secretion and absorption. Location: Kidney tubules, ducts, and glands. Function: Secretion and absorption. § Simple Columnar Epithelium: A type of simple epithelium that consists of tall, column-shaped cells, often involved in absorption and protection. Location: Digestive tract, respiratory tract Function: Absorption, protection § Pseudostratified Columnar Epithelium: A type of simple epithelium that appears to have multiple layers of cells, but is actually a single layer of cells that are tightly packed. Location: Trachea, bronchi Function: Protection, Secretion Stratified Epithelium: - It is a type of epithelial tissue that consists of multiple layers of cells. - There are several types of stratified epithelium, each with distinct and characteristics and functions: § Stratified Squamous Epithelium: A type of stratified epithelium that consists of multiple layer of flat, squamous cells, often involved in protection. Location: Skin, esophagus, mouth. Function: Protection - Characteristics: Multiple layers of cells Cells are tightly packed Apical cells are often dead and keratinized Found in areas where there is a lot of stress, such as skin and esophagus. Provides protection against physical stress and wear and tear.  Lecture 1: Cells & Tissues September 10, 2024 Epithelial Glands: - Classified into two main types: § Endocrine Glands: releases their products, hormones, directly into the blood. They do not have ducts for the most part. § Exocrine Glands: Secrete their products into ducts or directly into the site of action. Examples include: - Mucus-secreting glands - Sweat glands - Oil glands - Salivary glands Unicellular Exocrine Glands: - Consist of a single cell that secretes a product. - Examples include: § Goblet cells in the digestive epithelium § Mucus cells Multicellular Exocrine Glands: - Consist of an epithelial sheet that is folded into a glandular structure. - Classified into three types based on their structure: # Simple : Unbranched ducts structure # Compound: Branched ducts structure # Tubular: Tubular structure Type of Secretion: - Monocrine secretion: The most common type of secretion, where the cell releases its product through exocytosis. - Holocrine Secretion: The cell accumulates its product and releases it by rupturing and releasing its contents. - Apocrine Secretion: The cell accumulates its product in the apex and releases it by pinching off the apex. Connective Tissue: - provides protection, binding and support, insulation, storage, and transportation of materials. Types of Connective Tissue: - Mesenchymal Connective Tissue: Found only in the developing embryo. - Connective Tissue Proper: Comes in two flavors, dense and loose. - Cartilage: A rigid, yet flexible tissue found in joints and bones. It provides support and flexibility. - Bone: a hard, calcified tissue that provides support and protection. - Blood: Transport materials throughout the body. - Adipose Tissue: a type of connective tissue that stores fat. Lecture 1: Cells & Tissues September 10, 2024 Structural Components of Connective Tissue: - Cells: Various cell types specific to the connective tissue, including blasts (immune cells) and mature cells. - Fibers: Collagen, elastin, and reticular fibers. - Ground Substance: A gel-like substance that fills the space between cells and fibers. Cells Types in Connective Tissue: - Blasts: Immature cells that produce connective tissue, such as fibroblasts, osteoblasts, and erythroblasts. - Mature Cells: Cells that maintain the connective tissue, such as fibrocytes and osteocytes. - Mixed Bag of Cells: Connective tissue can contain a variety of cell types, including immune cells and blood cells. Structural Elements of Connective Tissue: - Collagen fibers: § High tensile strength, found in tendons and ligaments. - Elastic fibers: § allow tissue to deform and snap back to its original shape, found in lungs and elastic arteries. - Reticular fibers: § a mesh-like structure that provides support and shape to the tissue. Ground Substance: - It is the non-cellular component of connective tissue. - It is composed of: § Interstitial fluid: extracellular fluid that surrounds cells. § Proteoglycans: protein-sugar complexes that trap water and provide structure to the tissue. § Structural proteins: such as fibronectin and laminin, which provide sites for cells to attach to. - Ground Substance is like a sponge that holds water and provides structure to the tissue. The matrix: - It is the combination of the ground substance and the structural elements of connective tissue. - It provides a framework for cells to attach to and move through.  September 13, 2024 Lecture 2 : Nerve and Muscle The plasma membrane is composed of various lipids, including phospholipids, glycolipids, and cholesterols. Phospholipids: - Phospholipid: a type of lipid that has both hydrophilic (water-loving) and hydrophobic (water-hating) Part. - The hydrophilic part is the phosphate head, while hydrophobic part is the fatty acid tail. - Phospolipids are the main component of the plasma membrane, making up the bulk of the lipid bilayer. Glycolipids: - Glycolipids: a type of lipid that has a sugar molecule attached to a phospholipid. - Glycolipids are found in smaller amounts in the plasma membrane compared to phospholipids. Cholesterol: - Cholesterol: a type of lipid that is found in the plasma membrane and helps to provide stability and structure. - Cholesterol makes up about 20% of the plasma membrane and helps to anchor receptors in place. Arrangement of Phospholipids in Plasma Membrane: - The phospholipids in the plasma membrane are arranged in a specific way with the hydrophilic heads facing outwards and the hydrophobic tails facing inwards. Hydrophilic Hydrophobic Heads Tails Facing outwards, in Facing inwards, in Location contact with the middle of the extracellular fluid or lipid bilayer. cytoplasm. Interacting with Providing stability Function water and other and structure to the polar molecules. plasma membrane. Membrane Proteins: - Membrane Proteins are embedded in the plasma membrane and perform various functions, including transport, receptor stimulation, and cell signaling. Lecture 2 : Nerve and Muscle September 13, 2024 Types of Membrane Proteins: - Integral Proteins: Proteins that span the entire thickness of the plasma membrane, with both hydrophobic and hydrophilic parts. - Peripheral Proteins: Proteins that are attached to either the intracellular or extracellular surface of the plasma membrane. Functions of Membrane Proteins: Function Description Providing passageways for ions Transport and molecules to diffuse across the plasma membrane. Receptor Binding to hormones and Stimulation transmitting signals to the cell. Transmitting signals from the Cell Signalling extracellular space to the intracellular space. Examples of Membrane Proteins: - Channels: Proteins that provide passageways for ions and molecules to diffuse across the plasma membrane. - Receptors : Proteins that bind to hormones and transmit signals to the cell. - Filaments: Proteins that are part of the cytoskeleton and provide structure and shape to the cell. Cell membrane proteins are embedded in the plasma membrane and perform various functions. Some of these proteins function as: - Receptors: These proteins receive signals from outside the cell, such as hormones. There are two types of receptors : - Surface receptors: These receptors are embedded in the plasma membrane and receive signals from water- soluble hormones, such as insulin. - Intracellular receptors: These receptors are found inside the cell and receive signals from fat-soluble hormones, such as steroid hormones. - Enzymes: These proteins catalyze chemical reactions, such as the breakdown of ATP to form cyclic AMP. - Cell adhesion molecules (CAMs): These proteins allow cells to interact with each other and form tissues. Glycocalyx: - The glycocalyx is a sugar coating on the outside of the plasma membrane of cells. It is a mixture of carbohydrates attached to lipids and proteins on the outer surface of the cell. It serves as a molecular signature that helps the immune system recognize cells as self. Lecture 2 : Nerve and Muscle September 13, 2024 Functions of Glycocalyx: Function Description Helps the immune system Molecular Signature recognize cells as self. Immune System Allows immune system to distinguish Recognition between self and non-self cell Allows cells to interact with each Cell-cell recognition other Cell Junctions: - Cell Juctions are points of connection between adjacent cells. There are three common types of cell junctions: # Tight Junctions: § These are impermeable connections between cells that prevent substances from passing through. § These are formed by the close attachment of the plasma membranes of two cells. § They are found in tissues where a barrier is needed, such as the epithelial lining of the gut. Characteristics Description Prevents substances from Impermeable passing through. Strong Plasma membranes of two cells Attachment are closely attached. Found in tissues where a Barrier Function barriers is needed. # Desmosomes and Gap Junctions: § Desmosomes and gap junctions allows for cell-cell communication and interaction. Characteristics Description Desmosomes Allow for mechanical strength and adhesion between cells. Allow for direct communication Gap Junctions and exchange of ions and small molecules between cells. Lecture 2 : Nerve and Muscle September 13, 2024 Cancer Cells and the Immune System: - Cancer cells can evade the immune system by: § Changing their molecular signature. § producing enzymes that inhibit the immune system. § Escaping recognition by the immune system. - The immune system has difficulty recognizing cancer cells as foreign because they can mimic the molecular signature of normal cells. - Cell Junctions are specialized structures that connect cells to each other, and play a crucial role in maintaining tissue structure and function. Disorders Related to Cell Junctions: - GERD (Gastrointestinal Reflux Disease): A disorder that affects the tight junctions in the esophagus, allowing stomach acid to flow back up into the esophagus. - Hepatitis: A disorder that affects the tight junctions in the liver, allowing toxins to enter the liver and cause damage. - Cancer: A disorder that affects the cell junctions in various tissues, allowing cancer cells to spread and invade surrounding tissues. Membrane Tranport: - Membrane transport is the movement of molecules and ions across the cell membrane. Selectively Permeability: - The cell membrane is selectively permeable, meaning that it allows certain molecules and ions to pass through while preventing others. Molecules / Ions Permeability Lipid-Soluble Permeable molecules Water-Soluble Impermeable molecules Sodium Ions Impermeable Potassium Ions Impermeable Chloride Ions Impermeable Mechanisms of Memory Transport: - There are several mechanisms of membrane transport including: § Passive Transport: The movement of molecules and ions across cell membrane without the use of energy. § Active Transport: The movement of molecules and ions across the cell membrane using energy. § Facilitated Diffusion: The movement of molecules and ions across the cell membrane with the help of transport proteins. Lecture 2 : Nerve and Muscle September 13, 2024 Passive Transport vs. Active Transport: Passive Active Transport Transport ATP use No ATP used ATP used Down a Against a Direction of concentration concentration Movement gradient. gradient. Energy No energy Energy Requirements required Required Passive Transport: - There are four main types of Passive transport: § Simple diffusion: The movement substances from an high concentration to an area of low concentration, without the need for energy or transport proteins. § Facilitated Diffusion: The movement of substances from an area of high concentration to an area of low concentration, with the help of transport proteins. § Filtration: The movement substances through a semipermeable membrane, driven by hydrostatic pressure. § Osmosis: The movement of water molecules from one area of high concentration to another area of low concentration, through a semipermeable membrane. Concentration Gradient: is a difference in concentration of a substance between two areas. Electrochemical Gradient: is a difference in both concentration and electrical charge between two areas. Diffusion: - Diffusion is the tendency of molecules to scatter evenly throughout an environment. - Factors affecting Diffusion: § Concentration Difference: Larger differences in concentration increase the rate of diffusion. § Molecular Size: Larger molecules diffuse slower. § Temperature: Higher temperatures increase the kinetic energy of molecules, increasing the rate of diffusion. - Types of Diffusion: § Simple Diffusion: is a passive process where substances can freely move through the plasma membrane without the help of membrane proteins. # Characteristics of simple diffusion: - Substances must be small and lipid soluble. - No energy is required. - No membrane proteins are involved. # Examples of substances that cross the plasma membrane by simple diffusion: Oxygen, Carbon Dioxide, and water. Lecture 2 : Nerve and Muscle September 13, 2024 § Facilitated Diffusion : It is a type of diffusion that requires the help of membrane proteins to transport substances across the plasma membrane. # There are two types of facilitated Diffusion: - Carrier-Mediated Facilitated Diffusion - Channel-Mediated Facilitated Diffusion Carrier-Mediated Facilitated Diffusion: - A protein binds to a substance on one side of the membrane, changes shape, and releases the substance on the other side. - Characteristics: § Specificity: Carrier proteins are specific to one or a few substances. § Reversible Binding: Carrier proteins bind and release substances reversibly. § Limited Capacity: Carrier proteins have a limited number of binding sites. § Tranport Maximum : The maximum rate of transport is reached when all carrier proteins are occupied. - Examples of Carrier-mediated facilitated diffusion: § Glucose transport, Amino Acid transport, Ion transport. Carrier Saturation and Transport Maximum: - Carrier saturation occurs when all carrier proteins are occupied by a substance, and the rate of transport cannot be increased further. - The transport maximum is the maximum rate of transport that can be achieved by a carrier protein. Channel-Mediated Facilitated Diffusion: A protein forms a channel that allows substances to pass through the membrane.  September 17, 2024 Lecture 3 : Nerve and Muscle Facilitated Diffusion: § It is a type of passive transport that doesn’t require ATP. § It involves the movement of molecules from an area of high concentration to an area of low concentration with the assistance of a Carrier protein or channel protein. § Example: Glucose transport from the GI tract into the bloodstream and then to various tissues for metabolic needs. Channel Mediated Diffusion: § It is a type of facilitated diffusion that involves the movement of molecules through a channel protein in the cell membrane, allowing for the passage of small inorganic ions. § It can be inhibited by blocking the pore. Type of Channel Proteins: - Leaky Channels: Always open, allowing for slow leakage of ions. - Gated Channels: Opening and closing controlled by chemicals or electrical signals. - Examples: § Potassium channels § Sodium Channels Filtration: - It is a type of passive transport that involves the movement of water and solutes through a membrane or wall, driven by a pressure gradient. - It is not driven by concentration gradient. - Example: Capillary beds in the cardiovascular system m where blood is the transport medium. - Types of capillaries: - Continuous Capillaries: - No gap between endothelial cells. - Fenestrated Capillaries: - Small pores (fenestrae) between endothelial cells. - Sinusoidal Capillaries: - Large gaps between endothelial cells. Osmosis: - It is the movement of water from an area of high concentration to an area of low concentration through a semi-permeable membrane (movement of water across plasma membrane). Lecture 3 : Nerve and Muscle September 17, 2024 The plasma membrane is semi-permeable, allowing certain substances to pass through while restricting others. Water is one of the substances that can cross the plasma membrane, and it does so through two main mechanisms: - Diffusion: Water molecules can diffuse directly through the phospholipid bilayer, although this is a relatively slow process. - Water Channels: Water can also pass through specific channels in the plasma membrane, known as Aquaporins. § These channels are created by integral membrane and provide faster route for water to enter and leave the cell. Osmolarity: - The concentration of solute particles in a solvent, measured in units of osmoles per litern(Osm/L). - The osmolarity of a solution depends on the number of solute particles, not the type of solute. For example: § Sodium Chloride (NaCl) has 2 solute particles ( Na+ and Cl-). § Glucose (C6H12O6) has 1 solute particles. - When a solute is dissolved in water, the number of solute particles can affect the osmolarity of the solution. For example: § Sodium Chloride has 1 mole. § Glucose has 1 mole. Tonicity and Osmolarity: - Tonicity is a measure of the relative concentration of solutes in a solution, compared to another solution. - Tonicity is different from osmolarity, which is an absolute measure of solute concentration. Solution Osmolarity Tonicity Isotonic Equal to the cell’s internal No net movement of osmolarity water Hypotonic Lower than the cell’s internal Water enters the cell Osmolarity Hypertonic Higher than the cell’s internal Water leaves the cell osmolarity Osmosis in Animal Cells: - When animal cells are placed in different solution, they can shrink or swell due to the movement of water. The direction of water movement depends on the Tonicity of the solution. Solution Tonicity Effect on Cell Isotonic No net movement of water No change in cell size Hypotonic Water enters the cell Cell swells Hypertonic Water leaves the cell Cell shrinks Lecture 3 : Nerve and Muscle September 17, 2024 Example: Sucrose Solution - a 2M sucrose solution is placed in different concentrations of sucrose solution. The sucrose molecules cannot move through the semi-permeable membrane, but water can. Types of Tonicity: - Isotinic: A solution with the same concentration of solutes as another solution. - Hypertonic: A solution with a higher concentration of solutes than another solution. - Hypotonic: A solution with lower concentration of solutes than another solution. Clinical Applications of Tonicity: - 0.9% Saline Solution: § An isotonic solution used in IV drips to hydrate patients without affecting cell shape. - Hypertonic Solution: § Used to treat edema by pulling fluid from the interstitial space into the bloodstream. - Hypotonic Solution: § Used to treat dehydration, but must be administered carefully to avoid rapid changes in cell shape. Active Transport: - Active transport is the movement of molecules or ions across a cell membrane against their concentration gradient, requiring energy in the form of ATP. - Has two types: § Primary Active Transport: Directly uses ATP to transport molecules or ions against their concentration gradient. § Secondary Active Transport: Indirectly uses ATP to transport molecules or ions against their concentration gradient. - Characteristics: § Requires energy in the form of ATP § Moves molecules or ions against their concentration gradient. § Often involves carrier proteins or pumps. § Can be coupled to the transport of other molecules or ions. - Examples: § Sodium-Potassium Pump: # A primary active transport system that maintains the concentration gradients of sodium and potassium ions across the cell membrane. § Proton Pump: # A primary active transport system that pumps protons (hydrogen ions) out of the cell to maintain a stable pH.  Lecture 3 : Nerve and Muscle September 17, 2024 Vesicular Transport: - It is the movement of large particles, such as proteins or lipids, across a cell membrane using vesicles. - Characteristics: § Involves the formation of vesicles from the cell membrane. § Requires energy in the form of ATP. § Can be used to transport large particles or drop,ets of fluid. § Often involves the fusion of vesicles with other membranes. - Examples: § Endocytosis: # The uptake of particles or fluid into the cell through the formation of vesicles. § Exocytosis: # The release of particles or fluid from the cell through the fusion of vesicles with the cell membrane. *Transport Systems. Transport systems: - are mechanism that move molecules across cell membranes. - These systems can be classified into two main categories: # Symport: § A type of transport system that moves two or more molecules in the same direction across the cell membrane. § Examples: - Glucose absorption in the bloodstream from the GI tract. - Sodium and glucose co-transport in the kidneys. # Antiport: § A type of transport system that moves two or more molecules in opposite directions across the cell membrane. § Examples: - Sodium-potassium pump (Na+/ K+ ATPase) Sodium-Potassium Pump: - an example of primary active transport that moves sodium ions out of the cell and potassium ions into the cell. Step Description 1 Binding of sodium ions to the pump. 2 Hydrolysis of ATP and phosphorylation of the pump. 3 Change in pump shape, releasing sodium ions outside the cell. 4 Binding to potassium ions to the pump. 5 Dephosphorylation of the pump, releasing potassium ions into the cell. - It is essential for maintaining the proper concentration gradient of sodium and potassium ions across the cell membrane, which is necessary for various cellular functions, including muscle contraction and nerve impulses. September 24, Lecture 3 : Nerve and Muscle September 17, 2024 How Secondary Active Transport Works: 1. The sodium-potassium pump creates a concentration gradient of sodium and potassium ions across the plasma membrane. 2. The sodium ions move down their concentration gradient into the cell. 3. The movement of sodium ions is coupled with the movement of glucose or amino acids into the cell. 4. The glucose or amino acids are transported against their concentration gradient into the cell. Importance of Secondary Active transport: - It is important for absorption of glucose and amino acids from GI tract into the bloodstream. Endocytosis: - has three types: § Phagocytosis: The engulfment of large particles or cells by the cell membrane. § Pinocytosis: The uptake of small molecules or liquids by the cell membrane. § Receptor-Mediated Endocytosis: The uptake of molecules by the cell membrane through specific receptors. Receptor-Mediated Endocytosis: - It is a type of Endocytosis that involves the binding of molecules to specific receptors on the cell surface. Molecule Receptor Function Insulin Insulin Receptor Regulates glucose uptake Cholesterol LDL receptor Regulates cholesterol uptake Hormones Hormones receptors Regulates various cellular processes - It is important for the regulation of various cellular processes including glucose uptake, cholesterol uptake, and hormone signaling. Exocytosis: - It is important for the release of neurotransmitters, hormones, and other signaling molecules. - the process of exocytosis involves the following steps : § A vesicle containing the substance to be released forms within the cell. § The vesicle is transported to the plasma membrane. § The vesicles fuses with the plasma membrane, forming a pore. § The substance is released through the pore into the extracellular fluid. SNARE Proteins: - Play a crucial role in the process of exocytosis. - Has two types: § v-SNARE: A protein associated with the vesicles. § t-SNARE: A protein associated with the target membrane (plasma membrane).  September 17, 2024 Lecture 3 : Physiology of the Neuron The nervous system: - It is a complex system that allows for communication between different parts of the body. - It consists of two main parts: § Central Nervous system (CNS): # The CNS includes the brain and spinal cord. # It is protected by bones (skull and vertebral column. § Perioheral Nervous System ( PNS): # The PNS includes all the nervous tissue outside the CNS. # It is responsible for communicating with the outside world and bringing information to the CNS. Organization of the Nervous Systsem: - The Nervous system can be organized into different divisions: § Sensory Division: # Collects sensory information from the environment and senses it to the CNS. § Motor Division: # Sends commands from the CNS to muscles and glands. § Somatic Nervous System: # Controls voluntary movements (e.g.m skeletal muscles). § Autonomic Nervous System: # Controls involuntary movements (e.g., heart rate, digestion). The Enteric Nervous System (ENs): - It is a network of neurons that innervates the gastrointestinal tract. It is often referred to as “gut brain.” - It can function independently, but it also communicates with the CNS. Neurons: - are specialized cells that transmit and process information. - They have several distinct features: § Extremely Longevity: # Neurons can last for over 100 years if adequately nourished. § Interconnections: # Neurons have many connections with other neurons. § High metabolic Rate: # Neurons require a lot of energy to maintain their function. Structure of Neurons: - A typical neuron consists of : § Cell body (Soma): # The central part of the neuron that contains the nucleus and most organelles. § Processes: # Extensions of the neuron that can be either dendrites (receive signals) or axons (transmit signals).  Lecture 3 : Physiology of the Neuron September 17, 2024 Definitions: - Mitotic: § The ability of a cell to undergo cell division. § Neurons are lost-mitotic, meaning they do not divide. - Sodium-Potassium ATPase: § A protein that helps maintain the balance of sodium and potassium ions in the neuron, which is essential for neuronal function. Cell Body (Soma): - It is the part of the neuron where the cell’s genetic material is located and proteins are synthesized. - It contains various organelles, including: § Endoplasmic Reticulum (ER): # a network of membranous tubules and sacs involved in protein synthesis and transport. § Free Ribosomes: # Small organelles responsible for protein synthesis. § Cytoskeletal Elements: # Provide structural support and shape to the cell. § Pigment Inclusions: # Contain pigments that can affect the cell’s color and function. § Mitochondria: # Organelles responsible for generating energy for the cell through cellular respiration. - The cell body is like the command center of the neuron, where all the important decisions are made and the necessary proteins are synthesized. Dendrites: - are branching structures that originate from the cell body and serve as the receptive or input region of the neuron. - They: § increase the surface area of the neuron, allowing it to receive signals form multiple other neurons. § Collect and transmit information from other neurons to the cell body through a mechanism called graded potential. Axons: - are long, thin structures that extend from the cell body and are responsible for transmitting signals to other neurons. - They: § Propagate nerve impulses or action potential to other neurons. § Can be short or long, depending on the type of neuron. § Have a trigger zone where the decision to generate an action potential is made. § Branch into terminal areas, where neurotransmitters are released. Lecture 3 : Physiology of the Neuron September 17, 2024 Axon Structure Description Trigger Zone The region where the decision to generate an action potential is made. Terminal Area The region where neurotransmitters are released Axonal Terminals The ends of the axon where neurotransmitters are released Bundles of Axons: - Nerves are bundles of axons in the peripheral nervous system, while tracts are bundles of axons in the central nervous system. Specialized Terms: - Nuclei: § a cluster of neuronal cell bodies in the central nervous system, - Ganglia: § a cluster of neuronal cell bodies in the peripheral nervous system. - Apsolena: § the plasma membrane of the axon, which contains sodium-potassium ATPase pumps. September 20, 2024 Lecture 4 : Physiology of the Neuron Myelination of Axons: - It is the process of forming a myelin sheath around an axon, which is a whitish lipid protein substance that electrically insulates the axon. - This process is important for increasing the speed of nerve impulses or action potential transmission along the entirely of the axon. Type or cells involved in Myelination: - Peripheral Nervous System: Schwann Cells - Central Nervous System: Oligodendrocytes Myelination in the Peripheral Nervous System: - In PNS, Myelination is formed by Schwann cells. - These cells wrap themselves around a segment of an axon, creating layers of plasma membrane that push the cytoplasm and nucleus to the outside. This process creates a structure that looks like a series of concentric circles. Myelination in the Central Nervous System: - In CNS, myelination is formed by oligodendrocytes. - These cells have many processes that originate from the body and wrap themselves around multiple axons, creating the myelin insulation.  Lecture 4 : Physiology of the Neuron September 20, 2024 Nodes of Ranvier: - The gaps between Myelinated segments are called nodes of Ranvier. - These nodes are important for saltatiry conduction and can also have callateral axons emerging from them. Electrical Properties of Neurons: - Neurons, as well as muscle cells, are excitable. This means that they can be electrically stimulated. - Voltage: § It is the electrical potential energy due to a difference in distribution of charge. § Voltage is measured in milllivolts (mV) and is reported relative to the inside of he cell. The voltage difference between two points is called the potential difference. - Resting Membrane Potential: § It is the voltage difference between the outside and the inside of a cell when it is not being stimulated. § This value is typically around -70 mV and is established by the distribution of ions across the plasma membrane. Cell Polarization: - It refers to the difference in charge between the inside and outside of a cell. - This difference in charge is what leads to the resting membrane potential. Ion Channels: - Ion channels are proteins that serve as channels for ions to pass through the plasma membrane. - There are two main type of ion channels : § Passive ions channels: always open and allow ions to flow through the plasma membrane. § Gated ion channels: can be opened or closed in response to a stimulus, such as a change in voltage or the binding of a chemical. Types of Gated Ion Channels: - Chemcially gated ion channels: § Open in response to the binding of a chemical to a binding site on the channel. - Voltage gated ion channels: § Open or close in response to a change in the membrane potential. Establishment of Resting Membrane Potential: - The plasma membrane is permeable to potassium ions, but not sodium ions. - Potssium ions flow out of the cell through leaky potassium channels, making the inside of the cell more negative. - The sodium-potassium pump helps to maintain the resting membrane potential by pumping sodium ions out of the cell and potassium ions into the cell.  Lecture 4 : Physiology of the Neuron September 20, 2024 Resting Membrane potential Values: Ion Concentration Gradient Potassium High inside, low outside Sodium Low inside, high outside Importance Resting Membrane Potential: - The resting membrane potential is necessary for the proper functioning of cells. - It allows cells to be depolarized or hyperpolarized in response to stimuli. - It is essential for the transmission of signals between neurons. Excitable Cells and Resting Membrane Potential: - An excitable cell is a cell that can be electrically stimulated. Resting Membrane Potential : - It is the difference in electrical charge between the inside and outside of a cell when it is not being stimulated. This potential is generated by the movement of ions across the cell membrane. Changing the Resting Membrane Potential: - When the resting membrane,brand potential changes, it can generate two types of signals: § Graded Potentials: are short-lived signals that travel a short distance and , then fade away. They are generated by the movement of ions across the cell membrane in response to a stimulus. The strength of the stimulus determines how far the graded potential will travel. § Action Potentials: are long-distance signals that travel the length of the axon. They are generated by the movement of ions across the cell membrane in response to a stimulus that reaches a threshold value. The threshold value is typically around -50 to -55 millivolts. Depolarization and Hyperpolarization: - Depolarization is the process by which the cell membrane becomes less negative and more positive. - Hyperpolarization is the process by which the cell membrane becomes more negative.  Lecture 4 : Physiology of the Neuron September 20, 2024 Receptor Potentials: - Receptor potentials are graded potentials that are generated in response to a stimulus. - There are two types: § Separate receptor: The receptor is a separate entity from the neuron. § Dendritic receptor: The dendritic region of the neuron is the receptor itself. Afferent and Efferent Signals: - Afferent signals are incoming signals that are transmitted to the brain. - Efferent signals are outgoing signals that are transmitted from the brain. Synapses: - A synapse is the point of communication between two neurons. - Presynaptic neurons are the neurons that release neurotransmitters. - Postsynaptic neurons are the neurons that receive neurotransmitters. § “The synapse is the point of communication between two neurons, where the presynaptic neuron releases neurotransmitters that bind to receptors on the postsynaptic neuron, generating graded potential.” Depolarization and Repolarization: - When a graded potential (a local depolarization) reaches the axon, it opens the voltage-gated sodium channels. This allows sodium ions to rush into the cell, making the inside more positive. § Depolarization: the process of the inside of the cell becoming more positive. § Repolarization: the process of the inside of the cell returning to its resting state. Threshold Potential: - It is the level of depolarization that must be achieved for an action potential to be generated. § When the inside of the cell reaches a certain level and of depolarization (threshold), an action potential is triggered. This is the point at which cell becomes excited and the action potential begins. Action Potential Phases: - The action potential can be divided into several phases: § Depolarization: the rapid depolarization of the membrane due to the influx of sodium ions. § Repolarization: the return of the membrane to its resting state due to the efflux of potassium ions. § Hyperpolarization: the belief period during which the membrane becomes more negative that the resting membrane potential. Lecture 4 : Physiology of the Neuron September 20, 2024 Lecture 4 : Physiology of the Neuron September 20, 2024  September 24, 2024, Lecture 5 : Physiology of the Neuron Neuron to Neuron Connection: - Neurons communicate with each other through a process called synaptic transmission. This process involves the release of neurotransmitters from the presynaptic neuron and the binding of these neurotransmitters to receptors on the postsynaptic neuron. Definition of Key Terms: - Presynaptic Neuron: § The neuron that releases neurotransmitters into the synapse. - Postsynaptic Neuron: § The neuron that receives transmitters released by the presynaptic neuron. - Synapse: The small gap between the axonal terminal of the presynaptic neuron and the dendritic region of the postsynaptic neuron. Types of Synapses: - There are two types of synapses: § Chemical Synapses: the most common type of synapse and involve the release of neurotransmitters from the presynaptic neuron. The structure of a Chemical Synapse: Components Description Axon The end of the axon of the presynaptic neuron, Terminal where neurotransmitters are released. Synaptic Small sacs within the axonal terminal Vesicles that contain neurotransmitters Synaptic The small gap between the axonal terminal and Clerft the dendritic region of the postsynaptic neuron. Receptor The area on the postsynaptic neuron where Region neurotransmitters bind to receptors. § Electrical Synapses: a type of synapse where the signal is transmitted directly from one neuron to another through gap junction. Structure: - Gap Junctions: channels that connect the cytoplasm of two neurons. - Direct Communication : the signal can travel in both directions through the gap junctions. Characteristics: - Fast transmission: the signal can travel quickly through the gap junctions. - Bidirectional transmission: the signal can travel in both directions through the gap junctions. Location: In Embryonic Tissue and Eye movement.  Lecture 5 : Physiology of the Neuron September 24, 2024 The process Synaptic Transmission: 1. Action Potential: § An electrical signal travels down the axon of the presynaptic neuron and reaches the axonal terminal. 2. Release of Neurotransmitters: § The action potential triggers the release of neurotransmitters from the synaptic vesicles into the synaptic cleft. 3. Biniding of Neurotransmitters: § The released neurotransmitters bind to receptors on the postsynaptic neuron. 4. Graded Potential: § The binding of neurotransmitters triggers a change in the electrical properties of the postsynaptic neuron, resulting in a graded potential. 5. Depolarization: § If the graded potential is strong enough, it can trigger an action potential in the postsynaptic neuron. *** Why is Synaptic Transmission Unidirectional? => Synaotic Transmission is unidirectional because the only area of the synapse that release neurotransmitters is the axonal terminal of the presynaptic neuron, and the only area that has receptors for these neurotransmitters is the postsynaptic neuron. This means that the signal can only travel in one direction, the presynaptic neuron to the postsynaptic neuron. The role of Neurotransmitters in Synaptic Transmission: § Opening and Closing Ion Channels: Neurotransmitters can bind to receptors on the postsynaptic neuron and trigger the opening or closing of ion channels. § Affecting Membrane Permeability: The opening and closing of ions channels can affect the permeability of the membrane, leading to changes in the electrical properties of the neuron. § Triggering Depolarization or Hyperpolarization: The binding of neurotransmitters can trigger either depolarizatiom or hyperpolarization of the postsynaptic neuron, depending on the type of neurotransmitter and the type of receptor. # Chemical synapses. *** Chemical synapses are a type of synapse where the signal is transmitted from one neuron to another through the release of neurotransmitters. Graded Potentials & Action Potentials: § Graded Potential: a change in the membrane potential of a neuron that can be vary in amplitude. § Action Potential: a rapid change in the membrane potential of a neuron that is always the same amplitude. **** “ A graded potential is like a whisper, it can be soft or loud, while action potential is like a shout, it’s always the same volume.”  Lecture 5 : Physiology of the Neuron September 24, 2024 Increasing the Frequency of Impulses: - When the frequency of impulses increases, more neurotransmitters is released into the synaptic cleft. - This can lead to an increase in the number of channels open on the postsynaptic neuron, allowing more ions to flow in. Turning Off the Signal: - There are three ways to turn off the signal: Method Description Reuptake The presynaptic neuron reabsorbs the neurotransmitter. Degradation Enzymes break down the neurotransmitter. Diffusion The neurotransmitter diffuses away from the synaptic cleft. Examples of Neurotransmitters and Their Fate: Neurotransmitter Fate Norepinephrine Reuptake Acetylcholine Degradation by acetylcholinesterase Nitric Oxide Diffusion Synaptic Delay: - Synaptic delay: the time it takes for the neurotransmitter to move from the presynaptic neuron to postsynaptic neuron. - Rate Limiting Step: the slowest step in a series of reactions that determines the overall rate of the process. *** “The synaptic delay is like a bottleneck in a highway, it’s the slowest part of the process that determines how fast the signal can travel.” Neurotransmitter Binding & Graded Potential: - When a neurotransmitter binds to its receptor on the postsynaptic neuron, it generates a graded potential. A graded potential is change in the membrane potential of the neuron that can vary in strength, depending on the amount of neurotransmitters released and the duration of its binding. - The binding of neurotransmitters to their receptors opens channels that allow ions to flow in and out of the cell. This flow of ions changes the membrane potential if the neuron, generating a graded potential.  Lecture 5 : Physiology of the Neuron September 24, 2024 Excitatory and Inhibitory Postsynaptic Potentials: - There are two types of Postsynaptic Potentials: § Excitatory Postsynaptic Potentials (EPSPs): are generated when binding of neurotransmitters opens channels that allow positively charged ions (such as sodium) to flow into the cell. This flow of positively charged ions depolarizes the membrane, making it more positive. § Inhibitory Postsynaptic Potentials (IPSPs): are generated when the binding of neurotransmitters opens channels that allow negatively charged ions (such as chloride) to flow into the cell. This flow of negatively charged ions hyperpolarizes the membrane, making it more negative. Integration Of Signals: - Neurons receive signals from many other neurons, and these signals must be integrated to generate a response. - There are two ways that signals can be integrated: § Temporal Summation: occurs when signals arrive at the neuron in rapid succession. If the signals are close enough in time, they can build on each other to generate an action potential. Signal Arrival Time Effect on Membrane Potential Signals arrive far apart No action potential generated Signals arrive close together Action potential generated § Spatial summation: occurs when signals arrive at different regions of the dendritic area, but are close enough to influence each other. If the signals are strong enough, they can build on each other to generate an action potential. Signal Location Effect on Membrane Potential Signals arrive at distant regions No action potential generated Signals arrive at nearby regions Action Potential generated Action Potentials: - It is a rapid change in the membrane potential of a neuron that occurs when the membrane potential reaches a certain threshold (typically -55 mV). - It is generated in the axon of the neuron and are used to transmit signals to other neurons or to muscles or glands. Threshold Effect on Membrane Potential Membrane Potential reaches threshold Action potential generated Membrane potential doesn’t reach threshold No Action Potential generated  September 24, 2024 Lecture 5: Physiology of Nerve and Muscle II Muscle Physiology: - Three types of muscles in the body: § Skeletal Muscles: attached to the skeleton, allowing for movement of the body’s limps and other parts. They are the longest type of muscle cells and are striated. § Smooth Muscles: involved in involuntary movements, such as the contraction of the heart and the movement of food through the digestive system. § Cardiac Muscles: found in the heart and responsible for pumping blood throughout the body. Functions of Muscular Tissue: - has four main functions: § Movement: allowing for locomotion and manipulation of objects. § Stabilization of Joints: muscles help to hold joints together and provide stability. § Heat Generation: muscles generate heat, which is necessary for maintaining the body’s core temperature. § Protection of Organs: muscles help to protect internal and form valves. Functional Characteristics of Muscular Tissue: - has several functional characteristics, including: § Excitability: the ability to receive and respond to stimuli. § Contractility: the ability to shorten and contract. § Extensibility: the ability of lengthen and stretch. § Elasticity: the ability to return to its original shape after stretching or contracting. Anatomy of Skeletal Muscle Fibers: - Skeletal muscle fibers are: § Long and cylindrical § Multi-nucleated, with many oval nuclei § Syncytheal, meaning they are a single cell containing multiple nuclei Components of Skeletal Muscle Fibers: - Sarcolemma: § The plasma membrane of the muscle cell. - Sarcoplasm: § The cytoplasm of the muscle cell, containing glycogen & myoglobin. - Glycogen: § A storage form of glucose, used by the muscle for energy. - Myoglobin: § A protein that stores oxygen in muscle cells. - Myofibrils: § Bundles of proteins that make up the majority of the muscle fiber. - Sarcoplasmic Reticulum: § a complex network of smooth ER that transmits electrical impulses and stores calcium - T Tubules: § Components that help transmit electrical impulses and regulate muscle connection.  Lecture 5: Physiology of Nerve and Muscle II September 24, 2024 Definition of Key Terms: - Syncytheal: a single cell containing multiple nuclei. - Myofibrills: bundles of proteins that make up the majority of the muscle fiber. - Sarcoplasmic Reticulum: a complex network of smooth ER that transmits electrical impulses and stores calcium. ## Muscle Structure. Muscle Fibers and Fascicles: - Muscle Fibers are the building blocks of muscles. Each muscle fiber is a long, multinucleated cell that contains many myofibrils. Myofibrils are made up of sarcomeres, which are the smallest contractile units of muscle. - A group of muscle fibers is called a fascicle. Fascicles are surrounded by a layer of connective tissue called perimysium. The perimysium is thicker than the endomysium, which is the connective tissue that surrounds individual muscle fibers. Connective Tissue Coverings: - Endomysium: § Thin layer of connective tissue that surrounds individual muscle fibers. - Perimysium: § Thicker layer of connective tissue that surrounds fascicles. - Epimysium: § Thickes