Homeostasis:

The process by which organisms maintain a stable internal environment despite changes in external conditions. This involves feedback mechanisms that regulate body temperature, pH, glucose levels, etc.

Diffusion:

A passive process where molecules move from an area of higher concentration to an area of lower concentration. In single-celled organisms, diffusion directly exchanges gases and nutrients with the environment. In multicellular organisms, diffusion occurs across cell membranes and within tissues to distribute oxygen, nutrients, and waste products.

Homeostasis

The process by which organisms maintain a stable internal environment despite changes in external conditions.

Diffusion

A passive process where molecules move from an area of higher concentration to an area of lower concentration.

Sensory Neurons

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

Motor Neurons

Carry signals from the CNS to muscles and glands.

Interneurons

Connect sensory and motor neurons within the CNS.

Dendrites

Receive signals from other neurons.

Cell Body (Soma)

Contains the nucleus and organelles.

Axon

Transmits electrical impulses away from the cell body.

Synaptic Terminals

Release neurotransmitters to communicate with other neurons.

Synapse

The junction between two neurons where neurotransmitters are released to transmit signals.

Action Potential

A rapid change in membrane potential that travels along the axon.

Glial Cells

Support neurons by providing nutrients, removing waste, and insulating axons with myelin sheaths.

Central Nervous System (CNS)

Comprises the brain and spinal cord.

Peripheral Nervous System (PNS)

Includes all nerves outside the CNS.

Reflexes

Automatic responses to stimuli that involve sensory neurons, interneurons, and motor neurons.

Sensory Cells

Specialized cells that detect stimuli and convert them into electrical signals.

Touch

Mechanoreceptors in the skin.

Vision

Photoreceptors (rods and cones) in the retina.

Hearing

Hair cells in the cochlea.

Smell

Olfactory receptors in the nasal cavity.

Taste

Taste buds on the tongue.

Membrane Channels

Ion channels that open or close in response to stimuli, initiating sensory transduction.

Opsins

Light-sensitive proteins in photoreceptors that play a key role in vision.

Foveal Vision

Sharp central vision with high acuity.

Peripheral Vision

Detects motion and provides a broader field of view.

Brain

Processes sensory information to create perceptions and responses.

Skeletal Muscle

Voluntary muscles attached to bones.

Cardiac Muscle

Involuntary muscle found in the heart.

Smooth Muscle

Involuntary muscles in the walls of internal organs.

Muscle Fibers

Composed of myofibrils containing actin and myosin filaments.

Cross-Bridge Cycle

The process where myosin heads bind to actin, pull, and release, powered by ATP.

Calcium

Triggers muscle contraction by binding to troponin, which moves tropomyosin to expose binding sites on actin.

Antagonist Muscles

Muscle pairs that work opposite each other to move bones (e.g., biceps and triceps).

Gas Exchange

Oxygen is taken in, and carbon dioxide is expelled.

Ventilation

The process of moving air in and out of the lungs.

Gills

Extract oxygen from water.

Tracheae

Air-filled tubes in insects.

Lungs

Organs for gas exchange in terrestrial animals.

Negative Pressure Breathing

Diaphragm contraction creates a vacuum that draws air into the lungs.

Hemoglobin

A protein in red blood cells that binds oxygen; its affinity for oxygen is affected by pH and CO2 levels.

Myoglobin

Stores oxygen in muscle cells for use during intense activity.

Circulatory System

Transports nutrients, gases, and wastes throughout the body.

Open Circulatory System

Hemolymph bathes organs directly.

Closed Circulatory System

Blood is confined to vessels.

Heart

Pumps blood.

Arteries

Carry blood away from the heart.

Veins

Return blood to the heart.

Capillaries

Sites of material exchange.

Blood Flow

Path through the cardiovascular system, including the pulmonary and systemic circuits.

Material Exchange

Occurs primarily in capillaries.

Heart Contraction

Coordinated by the sinoatrial (SA) node and atrioventricular (AV) node.

Herbivores

Eat plants.

Carnivores

Eat other animals.

Omnivores

Eat both plants and animals.

Diet Components

Carbohydrates, proteins, fats.

Essential Minerals

Required for various bodily functions.

Essential Amino Acids

Must be obtained from the diet.

Vitamins

Organic compounds needed in small amounts.

Undernutrition vs. Malnutrition

Lack of sufficient calories vs. lack of essential nutrients.

Ingestion

Taking in food.

Digestion

Breaking down food into absorbable units.

Absorption

Nutrients enter the bloodstream.

Elimination

Expelling undigested material.

Alimentary Canal

The digestive tract from mouth to anus.

Mouth

Begins mechanical and chemical digestion.

Salivary Glands

Produce saliva to moisten food.

Epiglottis and Glottis

Prevent food from entering the trachea.

Stomach

Secretes acid and enzymes to digest food.

Small Intestine

Absorbs nutrients.

Pancreas

Produces digestive enzymes and bicarbonate.

Liver

Produces bile to emulsify fats.

Gallbladder

Stores and releases bile.

Large Intestine

Absorbs water and forms feces.

Appendix

A vestigial structure with immune functions.

Innate Immunity

Nonspecific defense mechanisms.

Adaptive Immunity

Specific responses to pathogens.

MHC I

Present on all nucleated cells; presents to cytotoxic T cells.

MHC II

Present on antigen-presenting cells; presents to helper T cells.

Macrophages

Engulf and digest pathogens.

Dendritic Cells

Present antigens to T cells.

Neutrophils

First responders to infection.

Helper T Cells

Activate other immune cells.

Cytotoxic T Cells

Kill infected cells.

Natural Killer Cells

Destroy virus-infected and cancerous cells.

B Cells

Produce antibodies.

Antibodies

Bind to antigens to neutralize them.

T Cell Receptors

Recognize antigens presented by MHC molecules.

Cytokines

Signaling molecules that regulate immune responses.

Vaccines

Stimulate the immune system to develop immunity to specific pathogens.

Hormones

Chemical messengers that regulate physiological processes.

Water-Soluble Hormones

Bind to receptors on the cell surface.

Lipid-Soluble Hormones

Pass through cell membranes and bind to intracellular receptors.

Endocrine Glands

Include the pituitary, thyroid, adrenal glands, etc.

Hypothalamus and Pituitary

The hypothalamus controls the pituitary, which regulates other endocrine glands.

Calcium Regulation

Parathyroid hormone increases blood calcium levels.

Short-Term Stress Responses

Mediated by the adrenal medulla (epinephrine and norepinephrine).

Long-Term Stress Responses

Mediated by the adrenal cortex (cortisol).

Ammonia

Highly toxic, requires a lot of water to excrete, common in aquatic animals.

Urea

Less toxic, requires less water, common in mammals, amphibians, and some fish.

Uric Acid

Least toxic, conserves water, common in birds, reptiles, and insects.

Cortex

Outer layer containing nephrons.

Medulla

Inner region with renal pyramids.

Renal Pelvis

Funnel-shaped structure that collects urine.

Glomerulus

A network of capillaries where blood filtration begins.

Bowman's Capsule

Encases the glomerulus and collects the filtrate.

Proximal Tubule

Reabsorbs nutrients, ions, and water from the filtrate.

Loop of Henle

Concentrates urine by reabsorbing water and salts.

Distal Tubule

Further adjusts the composition of the filtrate.

Collecting Duct

Final site for water reabsorption, leading to the renal pelvis.