Human Circulatory, Respiratory, and Endocrine System Functions and Pathways

Deoxygenated blood flow pathway

Enters right atrium -> right ventricle -> lungs via pulmonary artery.

Oxygenated blood flow pathway

Enters left atrium from lungs -> left ventricle -> body via aorta.

Thickest heart chamber

Left ventricle, because it must pump blood to the entire systemic body circulation.

Primary heart pacemaker

Sinoatrial (SA) node, which initiates the electrical impulse.

Alveoli gas exchange mechanism

Occurs via passive diffusion across a single-cell layer of capillaries.

Function of lung surfactant

Lipids that lower surface tension inside alveoli to prevent lung collapse during exhalation.

Brain structure regulating breathing

Medulla oblongata, which monitors carbon dioxide (CO2) levels and blood pH.

Pancreas blood sugar regulation

Beta cells secrete insulin to lower blood glucose; alpha cells secrete glucagon to raise it.

Master gland of endocrine system

Pituitary gland, which is controlled by the hypothalamus.

Antidiuretic Hormone (ADH) function

Produced by hypothalamus, tells kidneys to reabsorb water to increase blood volume and pressure.

Sympathetic nervous system effects

Triggers 'fight-or-flight' (dilated pupils, fast heart rate, stopped digestion).

Parasympathetic nervous system effects

Triggers 'rest-and-digest' (slowed heart rate, activated digestion).

Direction of neuron electrical impulse

Travels from dendrites, through cell body, down the axon, to axon terminals.

Function of myelin sheath

Fatty layer surrounding axons that increases the speed of electrical signal transmission.

Primary site of nutrient absorption

Small intestine, specifically via microvilli.

Stomach enzymes and acid

Uses pepsin and hydrochloric acid (HCl) to chemically break down proteins.

Bile production vs storage

Liver produces bile; gallbladder stores and concentrates it to emulsify fats.

Innate vs Adaptive immunity

Innate is non-specific (skin, phagocytes); adaptive is highly specific and creates memory.

B Cells function and maturation

Produce antibodies (humoral immunity) and mature in the bone marrow.

T Cells function and maturation

Destroy infected host cells (cell-mediated immunity) and mature in the thymus.

Active vs Passive immunity

Active comes from making your own antibodies (vaccine/infection); passive comes from external antibodies (breastmilk).

Functional unit of the kidney

Nephron, responsible for filtering blood, reabsorbing nutrients, and secreting waste.

Glomerulus function

Site where blood pressure forces water and solutes out of the blood into Bowman's capsule.

Renal response to low blood pressure

Kidneys release renin, activating the RAAS system to retain water and sodium.