Circulatory, Lymphatic, Nervous, Endocrine System

Circulatory System Function

Delivers oxygen and nutrients to cells and takes away waste.

Plasma Definition & Function

Liquid portion of blood containing water, electrolytes, waste, and ions.

Platelets / Thrombocytes Function

Small, round cellular fragments vital for normal blood clotting.

RBC / Erythrocytes Function

Transport oxygen and carbon dioxide.

WBC / Leukocytes Function

Help the body fight infection and other diseases.

Basophils Function

Release histamine and other chemicals causing inflammation and allergic symptoms.

Eosinophils Function

Defend against parasitic infections and regulate allergic responses.

Neutrophils Function

Most abundant WBCs; first responders to bacterial and fungal infections; engulf/destroy via phagocytosis; die forming pus.

Granulocytes Mnemonic

BEN = Basophil, Eosinophil, Neutrophil.

Monocytes & Macrophages Function

Monocytes remove debris and regulate inflammation; differentiate into Macrophages ("big eaters") to engulf/digest pathogens via phagocytosis.

Lymphocytes Types & Origin

B-cells (originating from Bone Marrow) and T-cells (originating from Thymus).

Plasma B-cell Function

Produces and releases large quantities of antibodies to neutralize/eliminate pathogens.

Memory Cell Function

Develops after initial antigen encounter; allows faster and robust response upon subsequent exposures.

Killer / Cytotoxic T-cell Function

Kills infected or cancerous cells directly.

Helper T-cell / CD4+ Function

Activates other immune cells like cytotoxic T-cells and B-cells to mount defense.

NK / Natural Killer Cell Function

Cytotoxic lymphocyte that kills target cells, particularly virus-infected or transformed cancer cells.

Blood Type A

Surface: A-antigens; Plasma: Anti-B antibodies; Compatible with: A, O.

Blood Type B

Surface: B-antigens; Plasma: Anti-A antibodies; Compatible with: B, O.

Blood Type AB (Universal Recipient)

Surface: A and B-antigens; Plasma: NO ANTIBODIES; Compatible with: A, B, AB, O.

Blood Type O (Universal Donor)

Surface: NO ANTIGENS; Plasma: Anti-A and Anti-B antibodies; Compatible with: O only.

Arteries Characteristics

Conduct blood away from heart; thick tunica media, muscular and elastic, small lumen; highest pressure and fast velocity.

Veins Characteristics

Conduct blood towards heart; thin muscle layer, less elastic, large lumen; slower velocity; rely on skeletal muscle and valves for return.

Capillaries Characteristics

Convey blood between arterioles and venules; one endothelial cell thick; site of gas, nutrient, and waste exchange.

Vessels Direction Tip

Artery = Alis or away from heart; Vein = Valik or vack to heart.

Pulmonary Circuit Purpose & Pathway

Carries deoxygenated blood to lungs and returns oxygenated blood; RA -> RV -> Pulmonary Artery -> Lungs -> Pulmonary Vein -> LA; Low-pressure circuit.

Systemic Circuit Purpose & Pathway

Carries oxygenated blood to body and returns deoxygenated blood; LV -> Aorta -> Body Tissues -> Vena Cava -> RA; High-pressure circuit.

Oxygen Concentration Extremes

Pulmonary Artery has lowest oxygen concentration; Pulmonary Vein has highest oxygen concentration.

Heart Structure & Muscle

4 chambers (RA, LA, RV, LV); Walls made of cardiac muscle (myocardium).

AV Valves Types & Locations

Tricuspid Valve (Between RA and RV); Bicuspid/Mitral Valve (Between LA and LV).

SL Valves Types & Locations

Pulmonary Valve (Between RV and Pulmonary Artery); Aortic Valve (Between LV and Aorta).

Heart Sounds (Lubb-Dupp)

Lubb sound = Closing of AV valves; Dupp sound = Closing of SL valves.

Chordae Tendineae & Papillary Muscles

Chordae tendineae ("heart strings") connect papillary muscles to valve leaflets to prevent backflow during ventricular contraction.

Blood Flow Pathway (Full)

Vena Cava -> RA -> Tricuspid Valve -> RV -> Pulmonary Valve -> Pulmonary Artery -> Lungs -> Pulmonary Vein -> LA -> Bicuspid Valve -> LV -> Aortic Valve -> Aorta -> Body.

Electrical Signals Pathway

Sinoatrial (SA) Node (Pacemaker) -> Atrioventricular (AV) Node -> Bundle of His -> Purkinje Fibers.

Bone Marrow Function

Soft tissue in bones that produces WBCs, RBCs, and platelets.

Thymus Function

Upper chest organ active before puberty where T-cells fully mature.

Lymph Nodes Function

Bean-shaped glands that filter lymph, clear out damaged/cancer cells, and store lymphocytes.

Lymph & Lymphatic Vessels

Lymph (extra fluid drained from tissues containing proteins, fats, waste, cells) travels through vessels with one-way valves.

Collecting Ducts (Lymphatic)

Right lymphatic duct and thoracic duct empty lymph into subclavian veins.

Spleen Function

Largest lymphatic organ; filters blood, removes old RBCs ("graveyard of RBCs"), and stores WBCs/platelets.

Innate vs. Adaptive Immunity

Innate = General, non-specific immediate defense; Adaptive = Targeted defense developed over time with immunological memory (cell-mediated & humoral).

Nervous System Functions

Major controlling, regulatory, and communicating center; performs Sensory, Integrative, and Motor functions.

Resting Potential State

Membrane potential is -70mV; Inside is more negative due to Na+/K+ pump (3 Na+ out, 2 K+ in) and K+ leak channels.

Action Potential - Depolarization

Stimulus reaches threshold (-55mV); Voltage-gated Na+ channels open, Na+ rushes in (influx) up to +30mV.

Action Potential - Repolarization

At +30mV, Na+ channels close and Voltage-gated K+ channels open; K+ flows out, making inside negative again.

Action Potential - Hyperpolarization

K+ channels stay open too long, causing membrane potential to drop to -80mV.

Refractory Period Types

Absolute = No new AP possible; Relative = Stronger stimulus needed to initiate AP.

Central Nervous System (CNS) Parts

Brain (protected by cranium) and Spinal Cord (protected by vertebrae); wrapped in meninges and cerebrospinal fluid.

Somatic vs. Autonomic System

Somatic = Voluntary control of skeletal muscle movements; Autonomic = Involuntary control of internal organs and glands.

Sympathetic vs. Parasympathetic

Sympathetic = "Fight-or-flight" (increases HR/breathing, slows digestion); Parasympathetic = "Rest and digest" (slows HR/breathing, increases digestion).

Cerebrum & Four Lobes

Largest brain part; Frontal (higher cognitive functions, motor control, personality), Parietal (sensory touch/temp/pain, spatial processing), Temporal (auditory), Occipital (visual).

Cerebellum Function

Coordination of movement, posture, and balance.

Hypothalamus Function

Control center coordinating the endocrine system and autonomic nervous system.

Hippocampus Function

Crucial role in memory and learning.

Medulla Oblongata Function

Regulates vital autonomic functions (HR, breathing, BP, digestion) and reflexes (swallowing, coughing, sneezing, vomiting).

Superior & Inferior Pons

Superior Pons contains pneumotaxic center (breathing rate/depth); Inferior Pons contains apneustic center (promotes inhalation).

Thalamus Function

Relay station for sensory and motor information; regulates consciousness, alertness, and sleep.

Endocrine System Mechanism

Glands produce hormone chemical messengers sent through bloodstream to target cells.

Negative vs. Positive Feedback

Negative = Output reduces initial stimulus (e.g., thermoregulation, thyroxine/cortisol pathways); Positive = Output enhances initial stimulus (e.g., oxytocin in labor).

TRH, TSH & Thyroxine Axis

Hypothalamus (TRH) -> Anterior Pituitary (TSH) -> Thyroid Gland -> Thyroxine (increases metabolic rate and growth).

CRH, ACTH & Cortisol Axis

Hypothalamus (CRH) -> Anterior Pituitary (ACTH) -> Adrenal Cortex -> Cortisol (stress hormone, suppresses immunity, increases blood sugar).

Growth Hormone (GH) Effects

Promotes tissue/bone growth; Hypersecretion (↑) = gigantism/acromegaly; Hyposecretion (↓) = dwarfism.

LH & FSH Functions

LH = Triggers ovulation/progesterone in females, testosterone in males; FSH = Promotes gamete development in both sexes.

Prolactin, ADH, Aldosterone, Oxytocin

Prolactin (milk production), ADH (water reabsorption in kidneys), Aldosterone (Na+ reabsorption/K+ excretion in kidneys), Oxytocin (uterine contractions, milk ejection).

Pituitary Gland Secretion Origins

Anterior Pituitary = GH, LH, FSH, Prolactin, TSH, ACTH; Posterior Pituitary = ADH, Oxytocin.

Glucagon vs. Insulin

Glucagon (Alpha cells) = Promotes glycogenolysis in liver, increases blood glucose; Insulin (Beta cells) = Promotes glycogenesis in liver, decreases blood glucose.

PTH vs. Calcitonin

PTH (Parathyroid) = Increases blood Ca2+, releases Ca2+ from bones; Calcitonin (Thyroid) = Decreases blood Ca2+, deposits Ca2+ into bones.

Sex Hormones Roles

Estrogen = Female secondary traits, menstrual cycle, endometrium thickening; Progesterone = Maintains endometrium for implantation; Testosterone = Male traits, sperm/muscle growth.

Cell Signaling Types

Endocrine (distant target via blood), Paracrine (nearby cells), Autocrine (signals itself), Juxtacrine (direct physical contact).

Exocrine Gland Secretion Modes

Merocrine (secretion via vesicle release; e.g., sweat glands), Apocrine (pinching off apical cell section; e.g., mammary glands), Holocrine (whole cell sheds; e.g., sebaceous glands).