Cell and Muscle Physiology

• Physiology is the study of how living organisms function, encompassing a wide range of topics from molecular mechanisms within cells to the integrated function of the whole body.

Cell Physiology

• The cell is the basic functional unit of the body.
• Cell physiology focuses on the mechanical, physical, and biochemical functions of cells.
• Key areas include membrane transport, cell signaling, and cellular metabolism.
• Membrane transport mechanisms govern the movement of substances across the cell membrane; these mechanisms include diffusion, osmosis, and active transport.
• Cell signaling involves communication between cells through chemical signals, which bind to receptors and trigger intracellular responses.
• Cellular metabolism encompasses all the chemical processes that occur within a cell to maintain life, including energy production (ATP synthesis) and synthesis of cellular components.

Muscle Physiology

• Muscle physiology studies the function of muscle tissue, including skeletal, smooth, and cardiac muscle.
• Skeletal muscle is responsible for voluntary movements and is characterized by its striated appearance due to organized sarcomeres.
• Smooth muscle is found in the walls of internal organs and blood vessels and is responsible for involuntary movements such as peristalsis and vasoconstriction.
• Cardiac muscle is found only in the heart.
• Muscle contraction occurs through the sliding filament mechanism, in which actin and myosin filaments interact to shorten the sarcomere.
• Calcium ions play a critical role in regulating muscle contraction by binding to troponin, which exposes myosin-binding sites on actin.
• Energy for muscle contraction is provided by ATP, which is generated through aerobic and anaerobic metabolism.

Nerve Physiology

• Nerve physiology examines the function of the nervous system, including neurons, glial cells, and synapses.
• Neurons are specialized cells that transmit electrical and chemical signals.
• Glial cells support and protect neurons.
• Action potentials are rapid changes in membrane potential that propagate along the neuron's axon, enabling long-distance communication.
• Synapses are junctions between neurons where signals are transmitted via neurotransmitters.
• Neurotransmitters are chemical messengers that bind to receptors on the postsynaptic cell, triggering either excitatory or inhibitory responses.
• Key neurotransmitters include acetylcholine, dopamine, serotonin, and norepinephrine.

Cardiovascular Physiology

• Cardiovascular physiology studies the function of the heart and blood vessels in transporting blood, oxygen, nutrients, and hormones throughout the body.
• The heart acts as a pump, driving blood through the systemic and pulmonary circulations.
• Blood pressure is the force exerted by blood against the walls of blood vessels and is regulated by factors such as cardiac output, peripheral resistance, and blood volume.
• Cardiac output is the amount of blood pumped by the heart per minute, determined by heart rate and stroke volume.
• Peripheral resistance is the resistance to blood flow in the blood vessels, influenced by factors such as vessel diameter and blood viscosity.
• Blood volume is the total amount of blood in the body, regulated by hormones such as antidiuretic hormone (ADH) and aldosterone.

Respiratory Physiology

• Respiratory physiology studies the function of the lungs and airways in gas exchange, allowing oxygen to enter the body and carbon dioxide to be removed.
• Ventilation is the process of moving air in and out of the lungs, driven by pressure gradients created by the diaphragm and intercostal muscles.
• Gas exchange occurs in the alveoli, where oxygen diffuses from the air into the blood and carbon dioxide diffuses from the blood into the air.
• Hemoglobin, a protein in red blood cells, binds to oxygen and transports it throughout the body.
• Respiration is regulated by the respiratory center in the brainstem, which monitors blood levels of oxygen, carbon dioxide, and pH.

Renal Physiology

• Renal physiology studies the function of the kidneys in filtering blood, regulating fluid and electrolyte balance, and excreting waste products.
• The nephron is the functional unit of the kidney, consisting of the glomerulus, proximal tubule, loop of Henle, distal tubule, and collecting duct.
• Glomerular filtration is the process by which blood is filtered in the glomerulus, producing a filtrate that enters the renal tubules.
• Tubular reabsorption is the process by which substances are reabsorbed from the filtrate back into the blood, including water, glucose, amino acids, and electrolytes.
• Tubular secretion is the process by which substances are secreted from the blood into the filtrate, including waste products, drugs, and excess ions.
• Urine formation is the end result of filtration, reabsorption, and secretion, with the composition and volume adjusted to maintain homeostasis.

Gastrointestinal Physiology

• Gastrointestinal physiology studies the function of the digestive system in breaking down food, absorbing nutrients, and eliminating waste.
• Digestion begins in the mouth with mechanical and chemical breakdown of food.
• The stomach stores food, secretes acid and enzymes for digestion, and regulates the release of chyme into the small intestine.
• The small intestine is the primary site of nutrient absorption, with the aid of enzymes from the pancreas and bile from the liver.
• The large intestine absorbs water and electrolytes, forms feces, and eliminates waste.
• Gut motility, including peristalsis and segmentation, propels food through the digestive tract.

Endocrine Physiology

• Endocrine physiology studies the function of endocrine glands and hormones in regulating various bodily functions, including metabolism, growth, and reproduction.
• Hormones are chemical messengers secreted by endocrine glands into the bloodstream, where they travel to target cells and elicit specific responses.
• The hypothalamus and pituitary gland form a key regulatory axis, controlling the secretion of many hormones.
• Major endocrine glands include the thyroid gland, adrenal glands, pancreas, and gonads.
• Hormone action involves binding to receptors on target cells, which triggers intracellular signaling pathways and alters gene expression or cellular activity.

Reproductive Physiology

• Reproductive physiology studies the function of the male and female reproductive systems, including gametogenesis, fertilization, pregnancy, and lactation.
• Gametogenesis is the process of producing eggs (oogenesis) and sperm (spermatogenesis) through meiosis.
• Fertilization occurs when a sperm cell fuses with an egg cell, forming a zygote.
• Pregnancy involves the development of the embryo and fetus within the uterus, supported by hormonal changes and placental function.
• Lactation is the production and secretion of milk by the mammary glands, stimulated by hormones such as prolactin and oxytocin.

Integrated Physiology

• Integrated physiology examines how different organ systems interact and coordinate to maintain homeostasis in the body.
• Exercise physiology studies how the body responds and adapts to physical activity, involving cardiovascular, respiratory, muscular, and endocrine systems.
• Environmental physiology studies how the body responds and adapts to environmental stressors such as heat, cold, altitude, and pollution.
• Pathophysiology studies the physiological mechanisms underlying disease, providing insights into the causes and progression of illness.