PHYS261 Midterm Study Guide: Key Concepts in Physiology

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Chapter 1: Introduction to Physiology

Pathophysiology

Pathophysiology is the study of how normal physiological processes are altered by disease. It helps explain the mechanisms underlying symptoms and signs of illness.

Key Point: Pathophysiology bridges basic physiology and clinical medicine.
Example: Diabetes mellitus disrupts glucose homeostasis, leading to hyperglycemia.

Teleological vs Mechanistic Explanations

Teleological explanations focus on the purpose of a physiological process, while mechanistic explanations describe how the process occurs.

Teleological: "Why" (e.g., Why do we sweat? To cool the body.)
Mechanistic: "How" (e.g., How do we sweat? By activation of sweat glands via sympathetic nerves.)

Homeostasis

Homeostasis is the maintenance of a stable internal environment despite external changes.

Key Point: Involves feedback mechanisms (negative and positive feedback).
Example: Regulation of blood glucose by insulin and glucagon.

Crossover Study

A crossover study is a type of clinical trial where participants receive multiple interventions in a sequence, allowing each participant to serve as their own control.

Key Point: Reduces variability and increases statistical power.

Placebo

A placebo is an inactive substance or treatment used as a control in experiments.

Key Point: Used to measure the psychological effect of receiving treatment.

Hypothesis and Theory

A hypothesis is a testable statement predicting an outcome. A theory is a well-substantiated explanation based on evidence.

Key Point: Hypotheses are tested; theories are established after repeated validation.

Dependent vs Independent Variables

In experiments, the independent variable is manipulated, while the dependent variable is measured.

Example: In a study on exercise and heart rate, exercise intensity is independent; heart rate is dependent.

Chapter 2: Molecular Interactions

Glycosylated Molecules

Glycosylated molecules are proteins or lipids with carbohydrate chains attached, important for cell recognition and signaling.

Example: Glycoproteins in cell membranes.

Biochemistry of Lipids

Lipids are hydrophobic molecules, including fats, oils, phospholipids, and steroids.

Key Point: Lipids are essential for energy storage, membrane structure, and signaling.

Amino Acids and Essential Amino Acids

Amino acids are building blocks of proteins. Essential amino acids cannot be synthesized by the body and must be obtained from diet.

Example: Leucine, lysine, and valine are essential amino acids.

Nucleotides

Nucleotides are the monomers of nucleic acids (DNA and RNA), consisting of a sugar, phosphate, and nitrogenous base.

Key Point: ATP is a nucleotide used for energy transfer.

Important Cations of the Body

Cations are positively charged ions crucial for physiological functions.

Examples: Na+, K+, Ca2+, Mg2+

Isotopes, Ions, Ionic and Covalent Bonds

Isotopes are atoms with the same number of protons but different neutrons. Ions are charged atoms. Ionic bonds involve electron transfer; covalent bonds involve electron sharing.

Example: NaCl forms via ionic bonding; H2O via covalent bonding.

Enzymes

Enzymes are biological catalysts that speed up reactions by lowering activation energy.

Factors Affecting Activity: Temperature, pH, substrate concentration, inhibitors.
Competitive Inhibitor: Binds to active site, blocking substrate.
Allosteric Inhibitor: Binds elsewhere, changing enzyme shape.
Maximum Reaction Rate: is reached when all enzyme active sites are occupied.

Chapter 4: Energy and Cellular Metabolism

Enzyme Activity and Activation Energy

Enzymes lower the activation energy required for reactions, increasing reaction rates.

Equation: (activation energy) is reduced by enzyme presence.

Regulation of Metabolic Pathways: ATP Production

Cells regulate metabolism via enzyme control, substrate availability, and feedback inhibition. ATP is produced through glycolysis, citric acid cycle, and electron transport chain.

Key Point: ATP is the main energy currency.

Electron Transport Chain

The electron transport chain (ETC) is a series of protein complexes in mitochondria that generate ATP via oxidative phosphorylation.

Equation:

Base Pairs of START and STOP Codons

START codon: AUG (codes for methionine). STOP codons: UAA, UAG, UGA.

Key Point: These codons signal initiation and termination of translation.

Overview of Protein Synthesis

Protein synthesis involves transcription (DNA to mRNA), mRNA processing, and translation (mRNA to protein).

Transcription: DNA is copied to mRNA.
mRNA Processing: Introns removed, exons spliced, cap and tail added.
Translation: Ribosome reads mRNA, assembles amino acids into polypeptide.

Chapter 5: Membrane Dynamics

Compartments of Body Fluids

Body fluids are divided into intracellular fluid (ICF) and extracellular fluid (ECF), which includes plasma and interstitial fluid.

Key Point: Fluid compartments are separated by cell membranes.

Molarity, Osmolarity, Osmolality, and Tonicity

These terms describe solute concentration and effects on cell volume.

Molarity: Moles of solute per liter.
Osmolarity: Osmoles per liter.
Osmolality: Osmoles per kilogram.
Tonicity: Effect of solution on cell volume (isotonic, hypertonic, hypotonic).

Diffusion of Uncharged Molecules

Uncharged molecules diffuse across membranes down their concentration gradient.

Key Point: No energy required; rate depends on gradient and membrane permeability.

Membrane Receptor Proteins

Extracellular ligands bind to membrane receptors, triggering cellular responses.

Example: Hormone binding activates signal transduction pathways.

Membrane Transporters

Carrier proteins and channel proteins facilitate movement of substances across membranes.

Carrier Proteins: Bind and transport specific molecules.
Channel Proteins: Form pores for ions to pass.

Endocytosis, Exocytosis, and Membrane Recycling

Endocytosis brings substances into cells; exocytosis releases substances; membrane recycling maintains membrane composition.

Example: Neurotransmitter release via exocytosis.

Chapters 8, 9, 10: Neurons and Sensory Physiology

Action Potential Phases

Action potentials are rapid changes in membrane potential in neurons.

Rising Phase: Na+ influx depolarizes membrane.
Overshoot: Membrane potential becomes positive.
Falling Phase: K+ efflux repolarizes membrane.

Refractory Periods

Absolute refractory period: no new action potential possible. Relative refractory period: action potential possible with stronger stimulus.

Key Point: Ensures unidirectional propagation.

All-or-None Principle

Action potentials occur fully or not at all, depending on threshold stimulus.

Key Point: No partial action potentials.

Convergence and Divergence

Convergence: multiple inputs to one neuron. Divergence: one neuron sends output to multiple targets.

Example: Sensory pathways converge; motor pathways diverge.

Spatial Summation

Multiple simultaneous inputs combine to reach threshold for action potential.

Key Point: Important for synaptic integration.

EPSP

Excitatory postsynaptic potential (EPSP) is a depolarizing event at the postsynaptic membrane.

Key Point: Increases likelihood of action potential.

Chronic and Referred Pain

Chronic pain persists beyond normal healing. Referred pain is felt in a location different from its origin.

Example: Heart attack pain felt in left arm.

Two-Point Discrimination

Ability to distinguish two close stimuli as separate.

Key Point: Indicates sensory receptor density.

Anterograde Amnesia

Loss of ability to form new memories after injury.

Example: Damage to hippocampus.

Associative Learning

Learning by associating two stimuli or a behavior and a stimulus.

Example: Pavlov's dogs salivating at bell.

Physiology of Hearing, Balance, Taste, Smell, and Vision

Sensory systems convert environmental stimuli into neural signals.

Hearing: Cochlea transduces sound.
Balance: Vestibular apparatus senses head movement.
Taste: Taste buds detect chemicals.
Smell: Olfactory receptors detect odorants.
Vision: Retina detects light.

Visual Pathway Structures

Pathway: Eye → Optic nerve → Optic chiasm → Optic tract → Lateral geniculate nucleus → Visual cortex.

Chapters 7, 22, 23: Endocrine System and Metabolism

Hormones of Anterior and Posterior Pituitary

Anterior Pituitary	Posterior Pituitary
ACTH, TSH, GH, PRL, FSH, LH	ADH (vasopressin), Oxytocin

Hormones of Adrenal Medulla

Key Hormones: Epinephrine, Norepinephrine, Dopamine

Adrenogenital Syndrome, Cushing’s, Addison’s, Grave’s Disease

Adrenogenital Syndrome: Excess androgen production.
Cushing’s Syndrome: Excess cortisol.
Addison’s Disease: Deficient cortisol and aldosterone.
Grave’s Disease: Autoimmune hyperthyroidism.

Push-Pull Control

Hormonal regulation often involves opposing hormones (e.g., insulin vs glucagon).

Fat Synthesis

Fat synthesis (lipogenesis) occurs in the fed state, converting excess glucose to triglycerides.

Fed State vs Fasted State Metabolism

Fed State	Fasted State
Insulin dominant, storage of nutrients	Glucagon dominant, mobilization of nutrients

Glycogenolysis and Gluconeogenesis

Glycogenolysis: Breakdown of glycogen to glucose.
Gluconeogenesis: Synthesis of glucose from non-carbohydrate sources.

Endocrine Response to Hypoglycemia

Low blood glucose triggers glucagon release, stimulating glycogenolysis and gluconeogenesis.

Chapters 16, 17, 18: Blood and Respiratory Physiology

Composition of Blood/Plasma

Component	Function
Plasma	Transport, osmotic balance
Red Blood Cells	Oxygen transport
White Blood Cells	Immune defense
Platelets	Clotting

Cellular Elements in Blood

Red Blood Cells (Erythrocytes): Carry oxygen.
White Blood Cells (Leukocytes): Immune function.
Platelets: Clot formation.

Cytokines in Hematopoiesis

Cytokines are signaling proteins that regulate blood cell formation.

Example: Erythropoietin stimulates RBC production.

Hemoglobin, Transferrin, Bilirubin, Liver, Jaundice

Hemoglobin: Oxygen-carrying protein in RBCs.
Transferrin: Iron transport protein.
Bilirubin: Breakdown product of hemoglobin.
Liver: Processes bilirubin; dysfunction leads to jaundice.

Hemostasis vs Homeostasis

Hemostasis is the process of stopping bleeding; homeostasis is maintaining internal stability.

Key Steps: Vasoconstriction, platelet plug, coagulation.

Platelet Plug Formation

Platelets adhere to damaged vessel, aggregate, and form a temporary plug.

Alveolar Structure

Alveoli are tiny air sacs in the lungs where gas exchange occurs.

Key Point: Thin walls, surrounded by capillaries.

Pulmonary Circulation

Blood flows from right ventricle to lungs for oxygenation, then returns to left atrium.

Dalton’s Law and Boyle’s Law

Dalton’s Law: Total pressure of a gas mixture is sum of partial pressures.
Equation:
Boyle’s Law: Pressure and volume are inversely related.
Equation:

Lung Volumes and Capacities; Spirometer

Lung volumes (tidal, residual, etc.) and capacities (vital, total) are measured with a spirometer.

Key Point: Used to assess respiratory function.

Compliance, Elastance, Surfactant

Compliance: Ability of lung to stretch.
Elastance: Ability to return to original shape.
Surfactant: Reduces surface tension in alveoli, preventing collapse.