Human Physiology Basics

The study of how living things function, focusing on the underlying mechanisms of body processes.

A group of cells with similar structure and specialized function.

Exchange materials between the cell and environment.

Connects, supports, and anchors various body parts.

Initiates and transmits electrical impulses.

The state of stable internal conditions maintained by body systems.

A mechanism that counteracts changes in body conditions.

The concentration of nervous system tissue in one end of the body, often the head.

The internal environment of a multicellular organism, composed of the fluids surrounding cells and facilitating life-sustaining exchanges.

A mechanism that amplifies a change, driving the controlled variable further away from the initial state.

The study of abnormal functioning of the body associated with disease.

A specialized cell that transmits information throughout the nervous system, composed of a cell body, dendrites, and an axon.

The branch-like extensions of a neuron that receive information from other neurons or sensory receptors.

The long, slender projection of a neuron that transmits information to other neurons, muscles, or glands.

The junction between two neurons where information is transmitted from one neuron to another.

Chemical messengers released by neurons that transmit signals across synapses.

The difference in electrical charge across the cell membrane of a neuron at rest, typically -70mV.

The rapid change in electrical potential across the cell membrane of a neuron during signal transmission, involving depolarization and repolarization.

The minimum level of stimulation required to trigger an action potential.

The brief period after an action potential during which another action potential cannot be generated.

A protein embedded in the cell membrane responsible for maintaining the resting potential by actively pumping sodium ions (Na+) out of the cell and potassium ions (K+) into the cell.

The potential difference across a membrane when the net movement of ions across it is balanced due to competing electrical and chemical forces.

The process of transmitting information between neurons via chemical messengers called neurotransmitters.

A type of synapse where electric currents directly pass between neurons through gap junctions.

A type of synapse where a chemical messenger (neurotransmitter) is released into the synaptic cleft to transmit information.

The process of releasing neurotransmitters from presynaptic vesicles into the synaptic cleft.

The process of integrating multiple signals from different synapses onto a single neuron.

A graded potential that makes a postsynaptic neuron more likely to fire an action potential.

A graded potential that makes a postsynaptic neuron less likely to fire an action potential.

Multiple EPSPs arriving at a single synapse within a short period of time, summing together to trigger an action potential.

EPSPs from multiple synapses arriving simultaneously, summing together to trigger an action potential.

The division of the nervous system that controls voluntary movements and receives sensory information from the external environment.

The division of the nervous system that controls involuntary functions like heart rate, digestion, and breathing.

The division of the autonomic nervous system responsible for the 'fight-or-flight' response, preparing the body for stressful situations.

The division of the autonomic nervous system that promotes 'rest and digest' functions, calming the body after stress.

The process by which photoreceptor cells convert light energy into a neural signal.

Specialized cells in the retina responsible for detecting light and initiating the phototransduction cascade.

A type of retinal cell that receives graded potentials from rods and cones and further processes the signal.

A type of retinal cell that sharpens image contrast by inhibiting neighboring cells through lateral inhibition.

A type of retinal cell responsible for motion and brightness perception.

The mechanism by which increased activity of one neuron inhibits the activity of its neighboring neurons, enhancing contrast and sharpness.

The ability to perceive different pitches of sound due to the stimulation of specific areas along the basilar membrane of the cochlea.

The ability to perceive the loudness of sound based on the intensity of stimulation of hair cells in the cochlea.

Sensory receptors in the inner ear responsible for detecting changes in head position and movement.

The bending of hair cell stereocilia against the tectorial membrane causes the opening of ion channels, leading to depolarization and neurotransmitter release.

Specialized proteins in sensory cells that detect stimuli in the internal and external environment.

A change detectable by the body, present in various energy forms or modalities.

Neurons carrying sensory information from receptors to the central nervous system (CNS).

The process by which sensory receptors convert stimuli into electrical signals.

Receptor potentials are graded potentials generated in sensory receptors in response to stimuli.

A type of sensory receptor that is highly sensitive to specific stimuli.

The ability of a receptor to adapt to continuous stimulation, causing a decrease in the firing rate of the associated sensory neuron.

Sensory receptors that respond to chemicals.

Sensory receptors that respond to mechanical pressure.

Sensory receptors that respond to light.

Sensory receptors that respond to temperature.

Sensory receptors that respond to changes in osmotic pressure.

Sensory receptors that respond to pain.

The frequency of action potentials in a neuron, which encodes information about the intensity, location, and duration of a stimulus.

The heart pumps deoxygenated blood into the pulmonary arteries, where it picks up oxygen in the lungs. Oxygenated blood then returns to the heart and is pumped out to the body.

The heart pumps oxygenated blood out to the body, where it delivers oxygen to tissues and picks up carbon dioxide. The deoxygenated blood then returns to the heart.

The period when the heart muscle contracts and pumps blood out of the chambers.

The period when the heart muscle relaxes and chambers fill with blood.

The specialized cardiac muscle cells that initiate the heartbeat, located in the upper right atrium.

A cluster of specialized cardiac muscle cells that slow down the electrical signal before it reaches the ventricles, located at the top of the septum.

Modified muscle fibers that rapidly conduct the electrical signal throughout the ventricles, initiating their contraction.

A recording of the electrical activity of the heart, used to assess its health and function.

The outer layer of the cerebrum, composed of neuronal cell bodies, responsible for higher cognitive functions.

The inner layer of the cerebrum, composed of neuronal axons, responsible for transmitting signals between different brain regions.

A relay center in the brain that processes sensory information and regulates consciousness.

A region below the thalamus that links the nervous and endocrine systems, regulating homeostatic functions like hunger, thirst, and body temperature.

A cluster of interconnected brain structures that play a crucial role in motor control and coordination.

The 'master gland' of the endocrine system, responsible for regulating hormone release.

A small gland in the brain that produces melatonin, a hormone that regulates sleep-wake cycles.

The lowest part of the brainstem, controlling vital functions like breathing, heart rate, and blood pressure.

A brain structure located at the back of the head, responsible for coordinating movement and balance.

The region of the frontal lobe responsible for initiating voluntary skeletal muscle movement.

The area of the parietal lobe responsible for receiving and processing sensory information from the body.

A group of interconnected brain structures involved in emotional responses, motivation, and memory formation.

A brain structure in the limbic system responsible for forming long-term memories and spatial navigation.

The brain's ability to acquire knowledge through experience, including learning, remembering, problem-solving, and reasoning.

A type of learning that involves strengthening neural connections through repeated stimulation.

The process by which gases move across a membrane from an area of high partial pressure to an area of low partial pressure.

The movement of fluids over long distances, driven by pressure gradients.

The passive movement of molecules from an area of high concentration to an area of low concentration.

The process of moving air in and out of the lungs to facilitate gas exchange.

The process of transporting oxygen and carbon dioxide throughout the body via the circulatory system.

Red blood cells, responsible for carrying oxygen throughout the body.

The process of breathing in which air flows in and out of the lungs in a rhythmic pattern.

Muscles responsible for expanding and contracting the chest cavity to facilitate ventilation.

The windpipe, the passageway for air entering the lungs.

The organs responsible for gas exchange between the lungs and the blood.

Branches of the trachea that lead to the bronchioles.

Tiny airways in the lungs that connect to the alveoli.

Tiny air sacs in the lungs where gas exchange occurs.

Tiny blood vessels surrounding the alveoli in the lungs.

A protein found in red blood cells that binds to oxygen and transports it throughout the body.

A type of muscle tissue found in the walls of internal organs like the stomach and intestines, responsible for involuntary movements like digestion and breathing.

A type of muscle tissue attached to bones, responsible for voluntary movements like walking and lifting.

A protein structure found in skeletal muscle, allowing for fast, powerful contractions.

A specialized network of membranes in muscle cells that stores and releases calcium ions for contraction.

Proteins within smooth muscle that anchor actin filaments, allowing for coordinated contraction.

The process by which a motor neuron triggers muscle contraction, starting with the release of acetylcholine and ending with the sliding of actin and myosin filaments.

The chemical messenger released by motor neurons at the neuromuscular junction, triggering muscle cell depolarization.

The process by which a muscle cell membrane becomes more positively charged, initiating a cascade of events leading to contraction.

A network of tubular extensions of the muscle cell membrane that conducts depolarization to the interior of the fiber.

A system of glands that produces hormones that regulate various bodily functions.

A type of hormone that binds to receptors on the surface of target cells.

A type of hormone that can cross the cell membrane and bind to receptors inside the cell.

A hormone that stimulates another endocrine gland to release its own hormones.

A hormone that acts directly on non-endocrine target tissues.

Descending limb (water limb) reabsorbs water due to its permeability to water and urea, while the ascending limb (salty limb) actively pumps salts (Na, K, Cl) out, creating a concentration gradient in the medulla.

The medulla surrounding the Loop of Henle becomes hypertonic (high concentration of solutes) due to the active pumping of salts from the ascending limb, and water reabsorption from the descending limb. This concentration gradient helps concentrate the urine.

Urea plays a crucial role in maintaining the hypertonic environment of the medulla, which helps concentrate urine and conserve water. It contributes to the osmotic gradient, facilitating water reabsorption.

Urea is a small, water-soluble molecule, and can passively diffuse across membranes, although it does so slowly. ADH upregulates urea transporter proteins, increasing its facilitated diffusion across the membranes. This helps to maintain the osmotic gradient in the medulla.

ADH (antidiuretic hormone) increases the collecting duct's permeability to water, allowing water to diffuse out of the filtrate, resulting in concentrated urine. This is activated when the body needs to conserve water.

Aquaporins (AQP) are transmembrane proteins that act as water channels, facilitating the movement of water across cell membranes. AQP2, specifically, is inserted into the membrane by ADH, increasing water permeability. This is important for water reabsorption and urine concentration.

When ADH is present, it triggers a signaling cascade that inserts AQP2 water channels into the collecting duct membrane. This increases water permeability, allowing water to move from the filtrate into the peritubular capillary (blood).

In the absence of ADH, the collecting duct is less permeable to water, resulting in dilute urine. This can happen due to factors like alcohol consumption, leading to dehydration.

A chemical process that breaks down large food molecules (polymers) into smaller molecules (monomers) that can be absorbed by the body.

A mechanical process that physically breaks down food into smaller pieces, increasing surface area for chemical digestion.

The first part of the digestive system, starting from the mouth to the stomach.

An enzyme found in saliva that begins the breakdown of carbohydrates.

The breakdown of proteins by enzymes, like pepsin, in the stomach.

The strong acid produced in the stomach (pH 1.5-3), crucial for protein digestion and killing bacteria.

The breakdown of lipids (fats) by enzymes, like lipases, in the stomach & small intestine.

The middle part of the digestive system, primarily responsible for chemical digestion and absorption of nutrients.

Finger-like projections in the small intestine that increase its surface area for efficient nutrient absorption.

Tiny hair-like projections on the surface of villi in the small intestine, further enhancing nutrient absorption.

The process of transporting glucose from the small intestine into the bloodstream.

The final part of the digestive system, responsible for absorbing water and eliminating waste.

A substance produced by the liver that helps emulsify fats, making them easier to digest.

The rhythmic contractions of smooth muscle that propel food through the digestive tract.

Ring-like contractions in the small intestine that mix chyme and enhance digestion.

The process by which the liver secretes bile, a fluid that aids in fat digestion. This involves the production and release of bile salts, which emulsify fats, making them easier to digest and absorb.

Specialized cells in the pancreas that produce and secrete pancreatic juice, a mixture of enzymes and bicarbonate ions crucial for digestion.

Clusters of cells within the pancreas responsible for producing and releasing hormones that regulate blood sugar levels, including insulin and glucagon.

A hormone produced by alpha cells in the Islets of Langerhans, primarily responsible for raising blood glucose levels by stimulating the breakdown of glycogen in the liver.

A hormone secreted by beta cells in the Islets of Langerhans, primarily responsible for lowering blood glucose levels by promoting glucose uptake by cells.

The process of breaking down food into smaller molecules that can be absorbed by the body. It involves mechanical and chemical breakdown in the digestive tract.

The process of absorbing useful nutrients from digested food into the bloodstream.

The movement of undigested food residues and waste products through the digestive tract, primarily in the large intestine.

The process of maintaining a stable internal environment within the body, including regulating water, electrolytes, and blood sugar levels.

The main organ of the urinary system responsible for filtering blood, regulating water and electrolyte balance, eliminating waste products, and producing hormones.

The process of filtering blood in the kidneys, where waste products, excess water, and electrolytes are removed from the bloodstream to form urine.

The process of retrieving useful substances from the filtrate in the nephron and returning them to the bloodstream.

The process of adding substances to the filtrate in the nephron, primarily to remove waste products and regulate the composition of urine.

The tiny, ball-shaped structure in the kidney where blood filtration occurs. It is composed of capillaries surrounded by Bowman's capsule.

The tube that carries urine from the kidneys to the bladder.