Introduction to Human Physiology – Module 1

Question-and-answer flashcards covering key concepts from Module 1: cell structure, membranes, transport, ATP production, tissue types, organ systems, and homeostasis.

What does physiology study?

The biological functions of living organisms—how the body works.

What is the smallest structural unit of life examined in physiology?

The cell.

What is homeostasis?

The dynamic process of maintaining a relatively stable internal environment.

What is the main purpose of physiological regulation mechanisms?

To preserve homeostasis.

Put these in order from simplest to most complex: organ, tissue, system, cell, organism.

Cell → tissue → organ → organ system → organism.

What name is given to the process by which unspecialized cells become specialized?

Differentiation.

Name the four primary tissue types and their key roles.

Epithelium (covering), connective (support), muscle (movement), nervous (control).

List three membrane-bound organelles.

Examples: nucleus, mitochondria, Golgi apparatus (others: RER, SER, lysosomes).

List two non-membranous organelles.

Examples: ribosomes, microtubules (others: microfilaments, centrioles).

Which organelle houses DNA and directs cellular activity?

The nucleus.

Where is most ATP generated inside the cell?

In the mitochondria.

Which organelle packages proteins for secretion?

The Golgi apparatus.

Which organelle contains digestive enzymes for intracellular cleanup?

Lysosomes.

Describe the basic structure of the plasma membrane.

A phospholipid bilayer with embedded proteins and cholesterol (fluid mosaic).

Why is the plasma membrane called the fluid mosaic model?

Because proteins float among lipid molecules like mosaic tiles and both can move laterally, giving the membrane fluidity.

What property of phospholipids drives bilayer formation?

Hydrophilic heads face water; hydrophobic tails avoid water and meet in the center.

Give three key functions of the plasma membrane.

Selective permeability, cell recognition/communication, structural boundary (also junction formation).

What are tight junctions?

Impermeable cell junctions that bind cells into leak-proof sheets.

What are desmosomes?

Anchoring junctions that hold cells together under mechanical stress.

What are gap junctions?

Communicating junctions that allow ions or small molecules to pass between cells.

Define simple diffusion.

Passive movement of molecules from high to low concentration.

Give one substance that crosses membranes by simple diffusion.

Oxygen (or carbon dioxide).

Why do glucose and amino acids require facilitated diffusion?

They are water-soluble and need carrier proteins to cross the hydrophobic lipid bilayer.

Define osmosis.

Diffusion of water across a selectively permeable membrane toward the higher solute concentration.

What is osmotic pressure?

The tendency of a solution to pull water into it, proportional to its solute concentration.

What is tonicity?

A solution’s ability to change cell shape by altering the cell’s water content.

What happens to red blood cells in a hypertonic solution?

They lose water and shrink (crenation).

What happens to red blood cells in a hypotonic solution?

They gain water, swell, and may burst.

What transport mechanism moves solutes against their gradient using ATP?

Active transport.

Which pump keeps intracellular K⁺ high and Na⁺ low?

The sodium-potassium pump (Na⁺/K⁺-ATPase).

Define endocytosis.

Uptake of large particles or fluid by vesicle formation at the plasma membrane.

Define exocytosis.

Fusion of a vesicle with the plasma membrane to release its contents outside the cell.

Why must dialysis fluid match blood glucose levels during kidney dialysis?

To prevent glucose from diffusing out of the blood while allowing waste like urea to leave.

What molecule is known as the cell’s energy currency?

ATP (adenosine triphosphate).

Name the four stages of cellular respiration.

Glycolysis, transition reaction, citric acid cycle, electron transport chain.

Where does glycolysis occur and what does it yield?

In the cytoplasm; it produces 2 pyruvate, 2 NADH, and a net gain of 2 ATP.

How many NADH, FADH₂, and ATP are produced per glucose in the citric acid cycle?

6 NADH, 2 FADH₂, and 2 ATP (plus CO₂).

Approximately how many ATP are generated by the electron transport chain per glucose?

About 32 ATP.

What process regenerates NAD⁺ under low-oxygen conditions?

Fermentation (anaerobic glycolysis).

Compare ATP yield: fermentation vs. aerobic respiration.

Fermentation yields only 2 ATP per glucose; aerobic respiration yields up to ~36 ATP.

Which system is the body’s fast-acting control system?

The nervous system.

How does the endocrine system transmit signals?

By releasing hormones into the bloodstream to reach distant targets.

Which system transports oxygen, nutrients, and hormones via blood?

The cardiovascular system.

Which system removes nitrogenous wastes and maintains water–salt balance?

The urinary system.

What feedback mechanism reverses deviations from a set point?

Negative feedback.

Give an example of positive feedback in the human body.

Oxytocin-driven uterine contractions during childbirth.

What can result when homeostatic regulation fails?

Illness or disease, e.g., diabetes mellitus.

Which hormone is deficient or ineffective in diabetes mellitus?

Insulin.

Which process brings particles into a cell by vesicle formation?

Endocytosis.

Homeostasis refers to what?

Maintaining a stable internal environment.