Physiology Lecture Notes PDF

Physiology is the study of biological function – of how the body works, from molecular mechanisms within cells to the actions of tissues, organs, and systems, and how the organism as a whole accomplishes particular tasks essential for life. The emphasis is on mechanisms – with questions that begin...

Physiology is the study of biological function – of how the body works, from molecular mechanisms within cells to the actions of tissues, organs, and systems, and how the organism as a whole accomplishes particular tasks essential for life. The emphasis is on mechanisms – with questions that begin with how and answers that involve cause-and effect sequences Hierarchical Organization of Body Plans External Environment Most animals are composed of specialized cells Terrestrial organized into tissues that have different functions. Aquatic Tissues make up organs, which together make up organ systems. Animal Body (Multicellular) Internal Environment Animal Cell Parts and General Functions Extracellular Fluid (ECF)- Interstitial fluid- Intravascular Free Ribosomes- protein synthesis fluid- Cerebrospinal fluid Ribosome- protein synthesis Intracellular Fluid (ICF)- Cytosol Mitochondria- ATP production Golgi Apparatus- sorting and packaging Exchange with the Environment Lysosome- Breakdown of molecules An animal’s size and shape directly affect how it Smooth ER- lipid synthesis exchanges energy and materials with its surroundings. Exchange occurs as substances dissolved in the Microfilaments- movement aqueous medium diffuse and are transported across the cells’ plasma membranes. Rough ER- protein synthesis A single-celled protist living in water has a sufficient Plasma membrane- selective transport of substances surface area of plasma membrane to service its entire Cilia- movement volume of cytoplasm. Nuclear pore- passage of nucleic acids Multicellular organisms with a sac body plan (e.g. Cnidaria – jellyfish, corals) have body walls that are Nuclear Envelope- separates nucleus from cytoplasm only two cells thick, facilitating diffusion of materials. Nucleus- stores genetic information More have highly folded internal surfaces for Cytoplasm- hold organelles in place exchanging materials. Centrioles- cell division Microtubules- movement Different tissues have different structures that are suited to their functions.  Tissues are classified into four main categories: 3 types of connective tissue fibers, all made of protein: 1.Epithelial 2.Connective 3.Muscle 4.Nervous 1. Collagen fibers provide strength and flexibility. Epithelial Tissue 2. Elastic fibers stretch and snap back to their original Covers the outside of the body and lines the organs length. and cavities within the body. 3. Reticular fibers join connective tissue to adjacent It contains cells that are closely joined. tissues. Epithelial tissues are classified according to: 1. Arrangement – relative number of layers Simple – one layer Stratified – two or more layers 2. Cell Shape In vertebrates, the fibers and foundation combine to form six major types of connective tissue: Squamous – scale-like 1. Loose connective tissue binds epithelia to underlying Cuboidal – cube-like tissues and holds organs in place. Columnar – column-shaped 2. Fibrous connective tissue is found in tendons, which attach muscles to bones, and ligaments, which connect bones at joints. 3. Cartilage is a strong and flexible support material. 4. Adipose tissue stores fat for insulation and fuel. 5. Blood is composed of blood cells and cell fragments Two less easily categorized types of epithelia: in blood plasma. 1. Pseudostratified epithelium– actually a simple 6. Bone is mineralized and forms the skeleton. columnar epithelium but its cells vary in height and nuclei lie at different levels – gives false appearance of being stratified. 2. Transitional epithelium– aka urothelium, a specialized stratified epithelium that become flattened when stretched. Connective Tissue Muscle Tissue Mainly binds and supports other tissues. Consists of long cells called muscle fibers, which It contains sparsely packed cells scattered throughout contract in response to nerve signals. an extracellular matrix. Divided in the vertebrate body into three types: The matrix consists of fibers in a liquid, jellylike, or solid foundation. 1. Skeletal muscle, or striated muscle, is attached to 3. Respiratory System- Gas exchange (uptake of bones and is responsible for voluntary movement. oxygen; disposal of carbon dioxide) 2. Smooth muscle mainly lines internal organs and is -Lungs, Trachea, Other Breathing Tubes responsible for involuntary body activities. 4. Lymphatic System- body defense (fighting infections 3. Cardiac muscle is responsible for contraction of the and virally induced cancers) heart. -Bone marrow, Lymph nodes, Thymus, Spleen, Lymph vessels 5. Urinary System- disposal of metabolic wastes; regulation of osmotic balance of blood -Kidneys, Ureters, Urinary bladder, Urethra 6. Endocrine System- coordination of body activities (such as digestion and metabolism) Nervous Tissue -Pituitary, Thyroid, Pancreas, Adrenal, and other hormone- secreting glands Senses stimuli and transmits signals throughout the animal. 7. Reproductive System- gamete production; promotion of fertilization; support of developing Nervous tissue contains: embryo 1. Neurons, or nerve cells-that transmit nerve impulses. -Ovaries or Testes and associated organs 2. Glial cells, or glia-that help nourish, insulate, and 8. Nervous System- coordination of body activities; replenish neurons. detection of stimuli and formulation of responses to them - Brain, Spinal cors, Nerves, Sensory organs 9. Integumentary System- protection against mechanical injury, infection, dehydration; thermoregulation. - Skin and its derivatives ( hair, claws, sweat glands) 11 Organ Systems of the BODY 10. Skeletal System- body support, protection of 1. Digestive System- Food processing ( ingestion, internal organs, movements. digestion, absorption, elimination) -Skeleton(bones, tendons, ligaments, cartilage) - Mouth, Pharynx, Esophagus, Stomach, Intestines, 11. Muscular System- locomotion and other movement Liver, Pancreas, Anus -skeletal muscles 2. Cardiovascular System- Internal distribution of materials -Heart, Blood vessels, Blood Homeostasis Animals must ensure that the ICF and ECF remain as stable as possible. This maintenance of a constant internal environment is called homeostasis. Claude Bernard (1813–1878) French physiologis Observed that the milieu intérieur (internal environment) remains remarkably constant despite changing conditions in the external environment. Walter Cannon (1871–1945) American physiologist Coined the term homeostasis to describe this internal constancy. The most common homeostatic control system is based around the principle of feedback. There are three principle components of a feedback system: 1.Receptor 2. Integrating center (Control center) 3.Effector The basic components of a feedback system and their arrangement Stimulus Receptor Afferent neurons s Integrating center Receptor- is responsible for detecting change in the Efferent neurons Effectors environment of the animal, either the external environment in which it lives, or its internal Response environment. The function of the receptor is to convert the detected change in the environment into action potentials which are sent via the afferent (sensory) division of the nervous system to the integrating center. Action Potential The effector is a general term given to structures which bring about a biological response. The permeability of Na+ and K+ depends on gated channels that open in response to stimulation. Effectors include muscles and glands – that produce a specific response to a detected stimulus. Net diffusion of these ions occurs into stages: first Na+ moves into the axon, then K+ moves out. This flow of ions, and the changes in the membrane potential that result, constitute an event called an action potential. Integrating center- is usually the brain or spinal cord in animals that possess them. The role of the integrating center is to compare the incoming information about a particular variable with what the variable should be. The integrating center must have a predetermined For example, the Hypothalamus is the integrating value for each variable that it controls. This value is center for the control of body temperature in known as the set point and it is the value of a particular mammals. variable that an animal strives to maintain. On the basis of incoming information from e.g. body temperature – the set point for mammals is thermoreceptors, the hypothalamus “decides” what approximately 37 ºC; some birds as high as 42 ºC. appropriate responses must be initiated to restore body e.g. blood pH – the set point is between 7.35–7.45. temperature to its desired value. This response is brought about by the action of Negative Feedback effectors, which are stimulated via efferent (motor) Negative feedback is when any deviation from the set pathways. point is made smaller or is resisted.  The response by the effector is stopped once the A conformer allows its internal condition to vary with variable returns to its set point. certain external changes. Acclimatization – the ability to alter the range over which a particular variable is maintained. Temperature, altitude, humidity, pH, salinity, pressure, etc. It can be considered as a fine tuning of homeostatic control systems, the cause of which is some factor in the environment. Positive Feedback e.g. High altitudes Positive feedback occurs when a response to the Acclimatization at high altitudes occurs when original stimulus results in the deviation from the set individuals travel to places like tall mountains or hill point becoming even greater. stations. When at high altitudes, the body undergoes changes to adapt to the lower oxygen levels and reduced air pressure. Key changes during acclimatization to high altitudes: Increased production of red blood cells. Increased pressure in pulmonary arteries, forcing blood into underutilized lung sections. Increased depth and volume of respiration e.g. Deep sea diving Deep sea divers must acclimatize during ascent from great depths, involving decompression to eliminate dissolved inert gases from their bodies. Animals manage their internal environment by During descent, hydrostatic and ambient pressure regulating or conforming to the external environment. increase, causing gases to dissolve in the body. A Regulator uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation.