Comprehensive Study Guide for Human Physiology

Homeostasis

Refers to the body's ability to maintain a stable internal environment despite changes in external conditions.

Atom

Basic unit of matter.

Molecule

Two or more atoms bonded together.

Organelle

Specialized structures within cells (e.g., mitochondria).

Cell

Basic unit of life.

Tissue

Groups of similar cells performing a common function (e.g., muscle tissue).

Organ

Composed of different types of tissues working together (e.g., heart).

Organ System

Group of organs that perform related functions (e.g., cardiovascular system).

Organism

A complete living entity capable of independent existence.

Local Control

Responses confined to a specific area (e.g., blood vessel constriction in response to injury).

Negative Feedback

The response reduces the stimulus (e.g., body temperature regulation: when body temperature rises, mechanisms like sweating cool the body, bringing it back to normal).

Positive Feedback

The response amplifies the stimulus (e.g., childbirth: uterine contractions lead to more contractions until delivery).

General Purpose of Homeostasis

To maintain conditions favorable for cell function and survival.

Negative Feedback Example

Regulation of blood sugar by insulin.

Positive Feedback Example

Blood clotting cascade during injury.

Nucleus

Contains genetic material (DNA), controls cell activities.

Mitochondria

Site of ATP production through cellular respiration.

Ribosomes

Protein synthesis.

Rough ER

Has ribosomes; synthesizes proteins.

Smooth ER

Synthesizes lipids, detoxifies drugs.

Golgi Apparatus

Modifies, sorts, and packages proteins for transport.

Lysosomes

Digestion and waste removal.

Peroxisomes

Detoxification, breakdown of fatty acids.

Cytoskeleton

Provides structure, shape, and aids in cell movement.

Plasma Membrane

Controls movement of substances in/out of the cell.

Glycolysis

Location: Cytoplasm. ATP Produced: 2 ATP.

Citric Acid Cycle (Krebs Cycle)

Location: Mitochondria (matrix). ATP Produced: 2 ATP.

Electron Transport Chain (ETC)

Location: Inner mitochondrial membrane. ATP Produced: ~34 ATP.

Non-Penetrating Solutes

Solutes that cannot cross the membrane, influencing water movement by osmosis.

Osmolarity

Concentration of solute particles in solution.

Osmolarity Calculation Example

1M NaCl → 2 Osm/L (because NaCl dissociates into two ions).

Diffusion

Movement from higher to lower concentration.

Osmosis

Water moves toward the higher solute concentration.

Isotonic

Equal solute concentration inside and outside the cell.

Hypotonic

Lower solute concentration outside, causing water to enter the cell.

Hypertonic

Higher solute concentration outside, causing water to exit the cell.

Carrier-Mediated Transport

Transport proteins bind to molecules, causing a conformational change to move the molecule across the membrane.

Symport

Carrier-mediated transport where molecules move in the same direction.

Antiport

Carrier-mediated transport where molecules move in opposite directions.

Fick's Law of Diffusion

Rate of diffusion = (Concentration gradient × Surface area × Permeability) / Distance.

Intracellular Fluid (ICF)

Fluid inside cells, comprising about 2/3 of body water.

Extracellular Fluid (ECF)

Fluid outside cells, comprising about 1/3 of body water.

Interstitial Fluid

Fluid surrounding cells.

Plasma

Fluid found in blood vessels.

Peptide Hormones

Hormones composed of chains of amino acids; water-soluble and produced in the rough endoplasmic reticulum.

Steroid Hormones

Hormones derived from cholesterol; lipid-soluble and synthesized in the smooth endoplasmic reticulum.

Amine Hormones

Hormones derived from amino acids (tyrosine or tryptophan) and produced by enzymatic modifications.

Catecholamines

A type of amine hormone that uses secondary messengers.

Thyroid Hormones

Amine hormones (T3/T4) that act directly on nuclear receptors.

ADH (Antidiuretic Hormone)

Increases water reabsorption, reduces urine output.

Oxytocin

Uterine contractions, milk ejection.

LH (Luteinizing Hormone)

Stimulates ovulation and progesterone production in females; testosterone production in males.

FSH (Follicle-Stimulating Hormone)

Stimulates follicle development and estrogen production in females; sperm production in males.

ACTH (Adrenocorticotropic Hormone)

Stimulates cortisol release.

TSH (Thyroid-Stimulating Hormone)

Stimulates release of thyroid hormones (T3/T4).

Prolactin

Stimulates milk production.

Growth Hormone (GH)

Stimulates growth, protein synthesis, and metabolism.

Testosterone

Promotes male secondary sex characteristics and sperm production.

Estrogen

Promotes female secondary sex characteristics and regulates the menstrual cycle.

Progesterone

Maintains pregnancy, regulates menstrual cycle.

Aldosterone

Increases sodium reabsorption, regulates blood pressure.

Cortisol

Regulates metabolism, suppresses immune response.

Androgens

Precursor to sex hormones.

Adrenaline (Epinephrine)

Increases heart rate, bronchodilation, glycogen breakdown.

Thyroid Hormones (T3/T4)

Increases metabolism, heart rate, and growth.

Parathyroid Hormone (PTH)

Increases blood calcium levels.

Calcitonin

Lowers blood calcium levels.

Insulin

Lowers blood glucose levels.

Glucagon

Raises blood glucose levels.

Humoral Regulation

Hormone release in response to changing blood levels of ions/nutrients.

Hormonal Regulation

One hormone stimulates the release of another.

Nervous System Regulation

Hormone release triggered by neural input.

Components of Blood

Plasma: ~55% of whole blood; Formed Elements: ~45%; Red Blood Cells (Erythrocytes): ~99% of formed elements.

Lifespan of Red Blood Cells

~120 days.

Lifespan of Neutrophils

~6 hrs to a few days.

Lifespan of Lymphocytes

Days to years.

Lifespan of Monocytes

Months.

Lifespan of Eosinophils

~5 days.

Lifespan of Basophils

A few hours to days.

Lifespan of Platelets (Thrombocytes)

~8-10 days.

Transport

gases (O₂, CO₂), nutrients, hormones, waste

Regulation

pH, body temperature, fluid volume

Protection

against blood loss (clotting), infection (immune defense)

RBCs

transport O₂ via hemoglobin; some CO₂ transport

WBCs

immune defense against pathogens

Platelets

clotting to prevent blood loss

Plasma

transports nutrients, hormones, and waste; maintains osmotic balance and pH

Water (~90%)

solvent for carrying substances; heat distribution

Plasma Proteins (~7%)

includes Albumin, Globulins, and Fibrinogen

Albumin

maintains osmotic pressure, transports lipids/hormones

Globulins

antibodies (γ-globulins), transport proteins

Fibrinogen

involved in clotting

Solutes (~1%)

includes electrolytes, nutrients, waste, gases, hormones

Electrolytes (Na⁺, K⁺, Ca²⁺, Cl⁻)

osmotic balance, membrane potentials

Nutrients

glucose, amino acids

Waste

urea, creatinine

Hormones

chemical messengers in the body

Hormone Class: Steroid

Lipid-soluble, made from cholesterol, bound to plasma proteins, acts through direct gene activation

Hormone Class: Amino Acid-based

Water-soluble, made from amino acids, free in plasma, binds to surface receptor → secondary messenger (e.g., cAMP)

Hormone Class: Peptide/Protein

Water-soluble, made from amino acid chains, free in plasma, binds to receptor → uses second messengers