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...

**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 **External Environment** Terrestrial Aquatic **[Animal Body (Multicellular)]** **Internal Environment** Extracellular Fluid (ECF)- Interstitial fluid- Intravascular fluid- Cerebrospinal fluid Intracellular Fluid (ICF)- Cytosol **Exchange with the Environment** An animal's size and shape directly affect how it exchanges energy and materials with its surroundings. Exchange occurs as substances dissolved in the aqueous medium **diffuse** and are **transported** across the cells' plasma membranes. A **single-celled protist** living in water has a sufficient surface area of **plasma membrane** to service its entire volume of cytoplasm. **Multicellular organisms with a sac body plan** **(e.g.** **Cnidaria -- jellyfish, corals)** have body walls that are only two cells thick, facilitating diffusion of materials. More have highly folded internal surfaces for exchanging materials.  **Hierarchical Organization of Body Plans** Most animals are composed of specialized **cells organized into tissues** that have different functions. Tissues **make up organs**, which together **make up organ systems.** **Animal Cell Parts and General Functions** **Free Ribosomes-** protein synthesis **Ribosome-** protein synthesis **Mitochondria-** ATP production **Golgi Apparatus-** sorting and packaging **Lysosome-** Breakdown of molecules **Smooth ER-** lipid synthesis **Microfilaments-** movement **Rough ER-** protein synthesis **Plasma membrane-** selective transport of substances **Cilia-** movement **Nuclear pore-** passage of nucleic acids **Nuclear Envelope**- separates nucleus from cytoplasm **Nucleus**- stores genetic information **Cytoplasm-** hold organelles in place **Centrioles-** cell division **Microtubules-** movement **Different tissues have different structures that are suited to their functions.** Tissues are classified into four main categories: 1.Epithelial 2.Connective 3.Muscle 4.Nervous **Epithelial Tissue** Covers the outside of the body and lines the organs and cavities within the body. It contains cells that are closely joined. **Epithelial tissues are classified according to:** **1. Arrangement** -- relative number of layers Simple -- one layer Stratified -- two or more layers **2. Cell Shape** Squamous -- scale-like Cuboidal -- cube-like Columnar -- column-shaped **Two less easily categorized types of epithelia:** **1. Pseudostratified epithelium**-- actually a simple 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** Mainly binds and supports other tissues. It contains **sparsely packed cells** scattered throughout an **extracellular matrix.** The matrix consists of **fibers in a liquid, jellylike, or solid foundation.** **3 types of connective tissue fibers, all made of protein:** **1.** **Collagen fibers** provide strength and flexibility. **2. Elastic fibers** stretch and snap back to their original length. **3. Reticular fibers** join connective tissue to adjacent tissues. **In vertebrates, the fibers and foundation combine to form six major types of connective tissue:** **1. Loose connective tissue** binds epithelia to underlying tissues and holds organs in place. **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 in blood plasma. **6. Bone** is mineralized and forms the skeleton. **Muscle Tissue** Consists of long cells called muscle fibers, which contract in response to nerve signals. **Divided in the vertebrate body into three types:** **1. Skeletal muscle**, or striated muscle, is attached to bones and is responsible for voluntary movement. **2. Smooth muscle** mainly lines internal organs and is responsible for involuntary body activities. **3. Cardiac muscle** is responsible for contraction of the heart. **Nervous Tissue** Senses stimuli and transmits signals throughout the animal. **Nervous tissue contains:** **1. Neurons, or nerve cells**-that transmit nerve impulses. **2. Glial cells, or glia**-that help nourish, insulate, and replenish neurons. **11 Organ Systems of the BODY** **1. Digestive System-** Food processing ( ingestion, digestion, absorption, elimination) **-** Mouth, Pharynx, Esophagus, Stomach, Intestines, Liver, Pancreas, Anus **2. Cardiovascular System-** Internal distribution of materials -Heart, Blood vessels, Blood **3. Respiratory System-** Gas exchange (uptake of oxygen; disposal of carbon dioxide) -Lungs, Trachea, Other Breathing Tubes **4. Lymphatic System-** body defense (fighting infections and virally induced cancers) -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) -Pituitary, Thyroid, Pancreas, Adrenal, and other hormone- secreting glands **7. Reproductive System-** gamete production; promotion of fertilization; support of developing embryo -Ovaries or Testes and associated organs **8. Nervous System-** coordination of body activities; 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) **10. Skeletal System-** body support, protection of internal organs, movements. -Skeleton(bones, tendons, ligaments, cartilage) **11. Muscular System-** locomotion and other movement -skeletal muscles **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**  **Receptor-** is responsible for detecting change in the environment of the animal, either the external environment in which it lives, or its internal 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 permeability of Na+ and K+ depends on gated channels that open in response to stimulation. 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. For example, the **Hypothalamus** is the integrating center for the control of body **temperature** in mammals. On the basis of incoming information from thermoreceptors, the hypothalamus "decides" what appropriate responses must be initiated to restore body temperature to its desired value. This response is brought about by the action of effectors, which are stimulated **via efferent** **(motor) pathways.** The **effector** is a general term given to structures which bring about a biological response.  Effectors include **muscles and glands** -- that produce a specific response to a detected stimulus. The integrating center must have a predetermined value for each variable that it controls. This value is known as the **set point** and it is the value of a particular variable that an animal strives to maintain. e.g. **body temperature** -- the set point for mammals is approximately 37 ºC; some birds as high as 42 ºC. e.g**. blood pH** -- the set point is between 7.35--7.45. **Negative Feedback** Negative feedback is when any deviation from the set point is made smaller or is resisted.  The response by the effector is stopped once the variable returns to its set point. **Positive Feedback**  Positive feedback occurs when a response to the original stimulus results in the deviation from the set point becoming even greater.  **Animals manage their internal environment by regulating or conforming to the external environment.** **A Regulator** uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation. **A conformer** allows its internal condition to vary with 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. **e.g. High altitudes** Acclimatization at high altitudes occurs when individuals travel to places like tall mountains or hill 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. During descent, hydrostatic and ambient pressure increase, causing gases to dissolve in the body.