BIOLOGY BLOCK 4

Respiratory System

Obtains oxygen and removes carbon dioxide.

Epiglottis

Flap that covers the trachea during swallowing.

Trachea

Windpipe reinforced by C-shaped cartilage rings.

Bronchi

Major airways entering the lungs.

Bronchioles

Small branches leading to alveoli.

Alveoli

Tiny air sacs where gas exchange occurs; oxygen diffuses into blood while carbon dioxide diffuses out.

Surfactant

Reduces surface tension and prevents alveolar collapse.

External Respiration

Gas exchange between alveoli and blood.

Internal Respiration

Gas exchange between blood and tissues.

Hemoglobin

Primary transporter of oxygen in blood.

Bicarbonate

Primary form in which CO₂ is transported in blood.

Medulla Oblongata

Brain region that controls breathing rate.

Circulatory System

Contains arteries, veins, and capillaries for blood transport.

Artery

Carries blood away from the heart.

Vein

Carries blood toward the heart.

Capillary

Site of nutrient and gas exchange.

Pulmonary Circulation

Heart → lungs → heart.

Systemic Circulation

Heart → body → heart.

Plasma

Liquid component of blood.

Erythrocyte

Red blood cell responsible for oxygen transport.

Leukocyte

White blood cell involved in immunity.

Platelet

Cell fragment involved in clotting.

Cardiac Output

Heart rate × stroke volume.

Systole

Heart contraction phase.

Diastole

Heart relaxation phase.

Lymphatic System

System that collects excess interstitial fluid.

Lymphatic Capillary

Collects excess interstitial fluid.

Right Lymphatic Duct

Drains upper right side of body.

Thoracic Duct

Drains most of the body.

Lacteal

Specialized lymphatic capillary in intestinal villi that absorbs fats.

Edema

Swelling caused by lymphatic blockage.

Immune System

System responsible for defense against pathogens.

Innate Immunity

Fast, nonspecific defense against pathogens.

Adaptive Immunity

Specific immune response with memory cells.

Antigen

A molecule recognized as foreign.

Antibody

Protein produced by B cells that binds antigens.

B Cell

Produces antibodies.

Plasma Cell

Activated B cell that secretes antibodies.

T Cell

Lymphocyte involved in cell-mediated immunity.

Helper T Cell

Activates immune cells.

Cytotoxic T Cell

Kills infected cells.

Memory Cell

Provides long-term immunity.

Vaccine

Triggers memory B and T cell formation without causing disease.

Antibiotic Resistance

Evolution of bacteria that survive antibiotic exposure.

Relative Abundance of WBCs

Neutrophils > Lymphocytes > Monocytes > Eosinophils > Basophils (Mnemonic: Never Let Monkeys Eat Bananas).

Renal System

System that filters blood and regulates water and electrolytes.

Kidney

Organ that filters blood.

Nephron

Functional unit of the kidney.

Renal Cortex

Outer kidney region.

Renal Medulla

Inner kidney region.

Renal Pelvis

Collects urine before it enters ureter.

Glomerulus

Capillary network where filtration occurs.

Bowman's Capsule

Collects filtrate from glomerulus.

Filtrate

Fluid entering nephron after filtration.

Proximal Convoluted Tubule (PCT)

Reabsorbs most water, glucose, amino acids, and ions.

Descending Loop of Henle

Permeable to water only.

Ascending Loop of Henle

Permeable to salt only.

Distal Convoluted Tubule (DCT)

Fine-tunes electrolyte balance.

Collecting Duct

Final urine concentration.

ADH

Increases water reabsorption.

Aldosterone

Increases sodium reabsorption.

Endocrine System

System of glands that secrete hormones.

Hormone

Chemical messenger transported in blood.

Endocrine Signaling

Hormones released directly into blood.

Exocrine Signaling

Secretions released through ducts.

Paracrine Signaling

Targets nearby cells.

Autocrine Signaling

Targets the same cell that released the signal.

Peptide Hormones

Hydrophilic hormones that bind membrane receptors.

Steroid Hormones

Cholesterol-derived hormones that bind intracellular receptors.

Amino Acid-Derived Hormones

Derived from single amino acids.

cAMP

Major secondary messenger.

IP3

Secondary messenger that releases calcium from ER.

DAG

Secondary messenger that activates protein kinase C.

Homeostasis

Maintenance of stable internal conditions.

Negative Feedback

Primary mechanism of homeostasis.

Positive Feedback

Amplifies a process.

Hypothalamus

Controls homeostasis and links nervous and endocrine systems.

ADH (Vasopressin)

Promotes water retention.

Oxytocin

Stimulates uterine contractions and milk ejection.

GnRH

Stimulates release of FSH and LH.

Digestive System

System responsible for food breakdown.

Mechanical Digestion

Physical breakdown of food.

Chemical Digestion

Enzymatic breakdown of food.

Salivary Amylase

Begins starch digestion.

Pepsin

Protein-digesting enzyme in stomach.

Pepsinogen

Inactive precursor of pepsin.

Bile

Emulsifies fats.

Pancreatic Amylase

Digests carbohydrates.

Trypsin

Digests proteins.

Lipase

Digests fats.

Small Intestine

Major site of digestion and absorption.

Villi

Fingerlike projections increasing surface area.

Microvilli

Further increase absorption surface area.

Nervous System

System that controls bodily functions.

Neuron

Functional unit of nervous system.

Dendrite

Receives signals.

Axon

Carries signals away from cell body.

Myelin

Insulating layer that speeds conduction.

Schwann Cell

Produces PNS myelin.

Oligodendrocyte

Produces CNS myelin.