Introduction to Human Physiology and Cell Organization PDF

Introduction to Human Physiology and Cell Organization İlker Çoban Learning Objectives By the end of this course, students should be able to: Define physiology. Explain the structure of cells and cell membranes. Describe the methods of substance transport across the cell membrane...

Introduction to Human Physiology and Cell Organization İlker Çoban Learning Objectives By the end of this course, students should be able to: Define physiology. Explain the structure of cells and cell membranes. Describe the methods of substance transport across the cell membrane. Identify the organelles of the cell and describe their functions. Explain the types of cell movement and provide examples. Define secondary messengers. Explain the concept of tissue and the fundamental characteristics of tissues. Explain the concept of homeostasis. Identify the fluid compartments of the body and explain the fundamental differences between them. Explain the mechanisms of negative feedback and positive feedback with examples. What is Physiology? Physiology is the branch of science that investigates the logic of life in living organisms. The science of physiology studies the functions of living beings and the underlying mechanisms of these functions, ranging from the molecular level to the levels of cells, tissues, organs, systems, and organisms. It seeks answers to questions like how it works and why it works that way. The field of physiology includes sub-disciplines such as human physiology, animal physiology, plant physiology, and microbial physiology. To understand and treat diseases, it is essential to first know the normal functioning mechanisms of the systems. If the normal functioning mechanism is unknown, abnormal conditions cannot be understood or interpreted. Basic Unit of Life The smallest functional unit of a living organism is the cell. It is estimated that there are over 100 trillion cells in our body. It is known that there are more than 200 different types of cells, each with distinct characteristics, shapes, and functions. Basic Unit of Life When cells are examined under a light microscope, four basic components can be distinguished: 1.Cell membrane 2.Nucleus 3.Cytoplasm 4.Nuclear membrane Ökaryot bir hücre Basic Functions of Cells Receiving and processing stimulus signals from the internal and external environment. Transporting substances through membrane-structured organs, such as the walls of the digestive system and blood vessels. Facilitating reproductive, division, and proliferation activities at the cellular level, excluding nerve and muscle cells. Producing energy through the reaction of nutrients with oxygen in cellular metabolism, and removing carbon dioxide and waste products generated by metabolism. Producing enzymes, hormones, and signaling molecules, which are secreted via exocytosis, and carrying out digestive processes. Basic Functions of Cells Acquiring substances necessary for cellular metabolism through endocytosis at the cell membrane. Enabling movement, balance, and posture at the organ level through the contraction of skeletal muscles, facilitating the body's motor functions. Propelling blood through the circulatory system via the contraction of cardiac muscle. Advancing, distributing, and mixing contents within organs through the contraction of smooth muscles, which operate two cavities. Fighting against infections. The formation of a zygote and its differentiation into an organism. Ect… Tissue Cells that are grouped together to perform the same function are called "tissue." Generally, there are four main types of tissues: 1.Epithelial tissue 2.Connective tissue 3.Muscle tissue 4.Nervous tissue 5. Adipose tissue (fat tissue) Common misuses include terms like lung tissue, kidney tissue, and pancreas tissue. Epithelial Tissue 1.Covering epithelium 2.Glandular epithelium: Eccrine Apocrine (pheromones) Holocrine (fat cells) Serous (tear glands) Mucous (goblet cells in the small intestine and respiratory system) Seromucous (saliva) 3. Additionally, there are sensory epithelia: Taste buds Olfactory cells Connective Tissue This type of tissue fills the intercellular spaces and serves several functions, including: Providing support Creating a matrix Offering protection Supplying nutrients Binding tissues together Repairing tissue losses Contributing to defense and shape. Examples of connective tissue include fibroblasts, collagen fibers, elastic fibers, tendons, subcutaneous connective tissue, adipose tissue, blood, bone, and cartilage. Muscle Tissue This type of tissue aids in the fundamental motor functions of the body and organs and is excitable (and in some cases, can generate stimuli). There are three types: 1.Smooth muscle 2.Skeletal muscle 3.Cardiac muscle Nervous Tissue This tissue group is excitable and capable of generating stimuli. The basic cells are neurons. Its functions include: Generation and transmission of electrical signals Formation of thoughts and ideas Reception of sensations such as touch, temperature, pressure, vision, hearing, and taste Stimulation of muscles, activation of glandular cells, and execution of autonomic functions, among many others. Fat Tissue Brown adipose tissue is more abundant in newborns. Its primary function is to produce heat, thanks to the protein thermogenin. Fat Tissue White adipose tissue is specialized as a long-term energy reserve. Organs Many types of tissue come together to form organs. Many organs contain different types of tissues. Organ Systems Belirli bir görevi gerçekleştirmek için birlikte çalışan organlar organ sistemlerini meydana getirirler. 1. Integumentary system 2. Skeletal system 3. Muscular system 4. Endocrine system 5. Nervous system 6. Circulatory system 7. Respiratory system 8. Digestive system 9. Reproductive system 10.Urinary system Internal and External Environment of the Body The body is continuously subjected to interventions from both the external environment and its internal environment. Despite these interventions, it manages to survive and maintain a state of balance. Single-celled organisms can obtain the nutrients and other substances they need from their surrounding environment in various ways and excrete metabolic waste back into that environment to survive. However, multicellular organisms do not have direct connections to the external environment like single-celled organisms. Therefore, complex organisms, such as humans, require multiple different systems to balance their internal environment with the external environment. Extracellular Fluid-Internal Environment On average, about 60% of an adult human body's composition is made up of a fluid that consists of ions and other substances in aqueous solutions. The majority of this fluid is found within the cells and is referred to as intracellular fluid. One-third of it, however, is located outside the cells and is called extracellular fluid. Extracellular fluid consists of blood plasma and interstitial fluid. The nutrients, ions, and many other substances contained in extracellular fluid are essential for cells to sustain their natural life processes. Therefore, cells actually live in extracellular fluid. As long as there is a sufficient amount of nutrients (such as carbohydrates, fats, amino acids, and other building blocks) in the extracellular fluid, cells can survive, grow, and perform their specialized functions. Extracellular Fluid-Internal Environment This extracellular fluid is continuously in motion throughout the body and is rapidly transported by circulating blood. Subsequently, blood and tissue fluids mix with each other through diffusion across the capillary vessel walls. As a result, extracellular fluid is referred to as the body's internal environment, or "milieu intérieur" Differences Between Extracellular and Intracellular Fluids Extracellular fluid contains large amounts of: Sodium Chloride Bicarbonate It also includes essential nutrients for cell survival, such as oxygen, glucose, fatty acids, and amino acids. Additionally, carbon dioxide, which is transported to the lungs for exhalation, and other cellular waste products that are eliminated through the kidneys, are found within the extracellular fluid. Intracellular fluid is rich in: Potassium Magnesium Phosphate ions All these concentration differences are regulated by specific mechanisms. Homeostasis For an organism to sustain life, there must be a certain degree of stability between the previously mentioned internal and external environments within specific limits. The maintenance of this stability in the body's internal environment is referred to as "homeostasis." Homeostasis is preserved and regulated by "homeostatic mechanisms." Disruptions in these homeostatic mechanisms can lead to diseases, dysfunctions, and even death. Types of Homeostatic Mechanisms and Related Systems All organ systems in the body, except for the reproductive system, play an active role in maintaining homeostasis. While the reproductive system is not essential for homeostasis, it contributes to the continuation of life. The systems involved in homeostasis include: Excretory system Circulatory system Respiratory system Digestive system Nervous system Endocrine system Key aspects of homeostasis include: Nutrient homeostasis (e.g., blood glucose levels: 70-100 mg/dL) Gas homeostasis (e.g., O₂ and CO₂ levels) Metabolite homeostasis (e.g., uric acid, urea) Acid-base homeostasis (pH: 7.35-7.45) Fluid volume homeostasis Blood pressure homeostasis (Systolic: 100-140 mmHg, Diastolic: 60-90 mmHg) Body temperature homeostasis (36-37.5°C) General Mechanism of Homeostasis All regulatory systems in the body have 3 basic elements. Receptor Control center Effector Types of Regulatory Systems In the operation of regulatory systems; Negative feedback Positive feedback Feed forward circuits serve. Negative Feedback The response generated is in the opposite direction of the initiating stimulus. Examples include: Regulation of blood glucose levels Regulation of blood O₂ and CO₂ levels Regulation of body temperature Regulation of body weight Positive Feedback Unlike negative feedback, the response in positive feedback enhances the variable further. Examples include: Oxytocin and uterine contractions Opening of Na channels during action potential formation Coagulation due to blood vessel damage Positive Feedback Positive feedback can sometimes lead to a vicious cycle and death! Homeostazla İlgili Süreçler Adaptation and Acclimatization Adaptation is a characteristic that promotes survival in a given environment. Homeostatic control systems are actually biologically acquired adaptation processes inherited through genetics. This means the ability to respond to a stress situation. This adaptive ability is not fixed and can be reinforced by prolonged exposure. The process of enhancing the functioning of an existing homeostatic system is called acclimatization. Organizati on of the Cell Definition The different substances that make up the cell collectively are referred to as "protoplasm." Protoplasm includes: Water Electrolytes (ions) Proteins Lipids Carbohydrates Water Hücrenin temel sıvı ortamı sudur. Yağ hücreleri hariç olmak üzere genel olarak hücrelerin %70-85’i sudan oluş­ur. Hücre de bir çok hücresel kimyasal, bu su ortamında çözünmüş durumdadır. Çözünmeyenler ise suyun içerisinde parçacıklar halinde süspanse olmuştur. Ions The most important ions within the cell are potassium, magnesium, phosphate, sulfate, bicarbonate, and to a lesser extent, sodium, chloride, and calcium. Ions are essential for cellular reactions. On the other hand, ions that can effectively move between the surfaces of cell membranes are necessary for transmitting electrochemical signals in excitable structures such as nerve and muscle fibers, enabling them to respond to or generate stimuli. Proteins Proteins normally constitute about 10-20% of cell mass and are the most abundant substances after water in many cells. They are classified into structural proteins and functional proteins. Structural proteins form the components of the cell's cytoskeleton. Functional proteins typically act as enzymes within the cell and are often mobile in the cytosolic fluid. These enzymes catalyze specific chemical reactions occurring within the cell. Lipids The most important ones in the cell are phospholipids, cholesterol and triglycerides. They can be found in different amounts in different cell types. While phospholipids and cholesterol play a role in the formation of the cell membrane, triglycerides form the storage energy source. Carbohydrates Other than being a part of glycoprotein molecules, they play very little role in structural functions. Their main purpose of use is as an energy source. glycocalyx Physical Structure of the Cell Cytoplasm The clear liquid part of the cytoplasm in which particles are dispersed is called cytosol. The amount of cytosol may vary depending on the function of the cell. Physical Structure of the Cell Cytoplasm In the gelatinous cytosol, there are dissolved proteins, water, electrolytes, glucose, enzymes, RNA, amino acids, nucleotides, and degradation products. Apart from these, there are organelles that perform various functions. On the other hand, many metabolic reactions related to the functions of the cell that do not occur in membrane-bound organelles in the cytosol take place. Protein synthesis and folding Signal transmission Cell division and movements Molecular transport Physical Structure of the Cell- Organelles Organelles Containing Organelles Without Membrane Structure (membranous) Membrane Structure Plasma Membrane Proteasome Smooth and Rough ER Ribosome Golgi Microtubules Endosomes Lysosomes Centrioles Transport Vesicles Filaments (actin-myosin- Mitochondria intermediate filaments) Peroxisome Physical Structure of the Cell- Organelles Plasma Membrane (Cell Membrane - Plasmalemma) The plasma membrane is a highly dynamic structure that delineates the boundaries of the cell, selectively separating its internal environment from the external environment. It is also referred to as the "plasma membrane" or "plasmalemma." Specific terms include: Sarcolemma: the membrane of a muscle cell Oolemma: the membrane of an egg cell In international literature, "cell membranes" and "plasma membranes" may refer to different structures. Cell membranes can also apply to organelles. Hücrenin Fiziksel Yapısı- Organeller Plasma Membrane (Cell Membrane - Plasmalemma) The cell membrane is composed of proteins, lipids, and carbohydrates, with a thickness of approximately 75- 100 Å (7.5-10 nm). Its composition includes: 55% proteins 25% phospholipids 13% cholesterol 4% other lipids 3% carbohydrates Cell Membrane Lipids The cell membrane contains three types of lipids: 1.Phospholipids 2.Glycolipids 3.Cholesterol These lipids are present in varying proportions among different cell types. The ratios can also differ between the inner and outer sides of the membrane, demonstrating asymmetry. Changes in this asymmetric structure can alter the fate of the cell. This is sometimes referred to as the "eat me" signal! Phospholipids They consist of a head and a tail. The structure formed by van der Waals bonds between the hydrocarbon chains The membrane can be observed by electron microscopy in cells stained with osmium tetroxide. Osmium tetroxide binds to the polar head.  Lipidlerin hareketi nadiren Lateral Flip- hareket flop (sıklıkla) (nadir en) Cholesterol Amphipathic. Cholesterol consists of 3 parts; Polar head part Rigid steroid ring part Nonpolar tail part Not found in bacterial and plant membranes. Cell Membrane Proteins The amount of protein in the membrane varies depending on the cell type. There are two types of membrane proteins: 1.Integral proteins: These span the entire membrane. 2.Peripheral proteins: These attach to only one surface of the membrane and do not span it completely. Zar Proteinlerinin Görevleri Integral proteins: They form structural channels (pores) that allow the diffusion of water molecules and water-soluble substances, particularly ions, between extracellular and intracellular fluids. These protein channels are selective, facilitating the preferential diffusion of certain substances over others. They also include carrier proteins that enable the passage of substances that cannot otherwise cross the lipid bilayer. Additionally, integral proteins can serve as receptors. Peripheral proteins: These proteins typically function as enzymes or act as molecules that regulate the passage of substances through the "pores" of the cell membrane.  Ekstrasellüle r alan Taşıyıcılar Bağlayıcılar Reseptörl Enzimler er Sitozol Carbohydrates Membrane carbohydrates are almost always found as glycoproteins or glycolipids, combined with proteins or lipids. Most integral proteins are glycoproteins, and about one-tenth of the membrane lipid molecules are glycolipids. The "glyco" portions of these molecules always protrude outward from the cell surface. Many carbohydrate compounds known as proteoglycans consist of small protein cores with carbohydrate materials loosely attached to the outer surface of the cell. Therefore, the outer surface of the cell is often entirely covered by a loose carbohydrate coat known as the glycocalyx. Functions of Membrane Carbohydrates Due to their negative charge, carbohydrates contribute to the negative charge of the cell's outer surface and repel other negatively charged substances. In some cases, the glycocalyx of certain cells can bind to the glycocalyx of other cells, allowing the cells to adhere to one another. Most carbohydrates also serve as receptors for hormones such as insulin. They protect the cell from mechanical and chemical effects and play a role in cell recognition (e.g., blood groups, immune structures). Functions of the Cell Membrane Selective permeability Signal transduction Endocytosis Exocytosis Compartmentalization Metabolic processes and organization Storage, transport, secretion Representing the electrical charge of the cell