Human Biology Overview

Peripheral Resistance Regulation

• Arterioles are the primary site for regulating peripheral resistance.

Excitation-Contraction Coupling

• Action potential (AP) along the T-tubule triggers the release of calcium ions (Ca²⁺) from the sarcoplasmic reticulum (SR) near myofibrils.
• This calcium release initiates muscle contraction.

Atrioventricular Valves

• The mitral valve and tricuspid valve are the atrioventricular valves.

Cardiac Output

• Cardiac output is calculated by multiplying heart rate by stroke volume.

Germ Layers

Ectoderm

• Outermost germ layer.
• Develops into skin and the nervous system.

Mesoderm

• Middle germ layer.
• Forms muscle, skeleton, and organs related to circulation, reproduction, and excretion.

Endoderm

• Innermost germ layer.
• Develops into the lining of the gut and associated organs.

Types of Tissues

• Epithelial tissue: Lines body surfaces.
• Muscle tissue: Composed of fibers that contract.
• Nervous tissue: Composed of cells with projections for transmitting electrical signals.
• Connective tissue: Diverse group including loose connective tissue, cartilage, bone, and blood.

Basic Cell Structure

• Nucleus, cytoplasm, and cell membrane are the components of a basic cell structure.

Nucleus

• Organelle containing chromosomes.

Cytoplasm

• Jelly-like substance within the cell, suspending organelles.

Nucleobases in DNA

• Adenine (A)
• Thymine (T)
• Guanine (G)
• Cytosine (C)

Chromosome

• A structured package of DNA.

Cell Cycle Phases

• Interphase:
  • G1: Cell growth.
  • S: DNA synthesis.
  • G2: Growth and preparation for mitosis.
• Mitosis: Cell division.

Mitosis Phases

• Prophase: Chromatin condenses into chromosomes.
• Metaphase: Spindle fibers attach, chromosomes align at the cell's center.
• Anaphase: Sister chromatids separate and move to opposite poles.
• Telophase & Cytokinesis: Two daughter cells form.

Regulator Molecules

• Molecules that either promote or halt the cell cycle.

Cancer

• Characterized by uncontrolled cell growth.

Proto-oncogenes

• Precursors to oncogenes.
• Code for positive cell cycle regulators.

Meiosis

• Cell division in germ cells producing gametes (sperm or egg).
• Results in four daughter cells each with half the chromosomes of the parent cell.

Zygosity

• Degree of similarity of alleles for a trait in an organism.

Homozygous/Heterozygous

• Homozygous: Two copies of the same allele.
• Heterozygous: One dominant and one recessive allele.

Allele

• Alternative form of a gene (e.g., A, B, and O blood types).

Autosomal Dominant/Recessive

• Dominant: Only one affected allele needed for expression.
• Recessive: Two affected alleles needed for expression; one affected allele is a carrier.

Central Dogma of Molecular Biology

• DNA → RNA → Protein. Genetic information flows in one direction.

Translation

• mRNA decoding to synthesize protein.

Transcription

• DNA to RNA process.

Protein Folding

• Amino acid chain folding to a functional protein.

Peptide Bond

• Chemical bond linking amino acids.

Peptide

• Chain of amino acids.

Ribosome

• Organelle synthesizing protein.

Gene

• Functional unit of DNA.

Codon

• Three-base sequence in DNA or RNA specifying an amino acid.

Protein Structures

• Primary: Amino acid sequence.
• Secondary: Local folding (alpha-helices, beta-sheets).
• Tertiary: 3D folding pattern due to interactions.
• Quaternary: Protein with multiple polypeptide chains.

Organelles

• Structures within a cell performing specific functions.

Cytosol

• Fluid component of the cytoplasm.

Endoplasmic Reticulum

• Network of membranes involved in protein and lipid transport.

Golgi Apparatus

• Modifies, sorts, and packages proteins and lipids.

Endocytosis

• Cell taking material into the cell via membrane infolding.

Exocytosis

• Cell releasing material outside the cell.

Lysosomes

• Organelles containing enzymes for cellular waste breakdown.

Mitochondria

• Site of ATP (energy) production. Contains DNA.

ATP

• Adenosine triphosphate, the main energy currency of cells.

ATP Production

• Anaerobic: No oxygen, small ATP yield, in cytoplasm.
• Aerobic: Requires oxygen, large ATP yield, in mitochondria.

Cell Membrane Structure

• Double lipid layer with polar and nonpolar ends.

Diffusion

• Movement of solutes from high to low concentration.

Osmosis

• Solvent movement from low solute concentration to high solute concentration across a membrane.

Filtration

• Movement across a membrane (sieve-like) due to pressure difference.

Active Transport

• Energy-requiring movement of material against a concentration gradient.

Sodium-Potassium Pump

• Active transport using energy to move Na+ out and K+ into the cell.

Resting Membrane Potential

• Electrical charge of a neuron at rest (-70mV).

Depolarization

• Inside of the cell becomes less negative (Na+ influx).

Action Potential

• Rapid change in membrane potential during signaling.

Threshold Potential

• Membrane potential value needed to initiate an action potential.

Repolarization

• Return of the membrane potential to resting state (K+ efflux).

Central Nervous System

• Brain and spinal cord.

Peripheral Nervous System

• Nerves connecting the CNS to the rest of the body (sensory & motor).

Neuron

• Nerve cell, primary function: signal conduction.

Nuclei

• Clusters of neuron cell bodies in the CNS.

Ganglia

• Clusters of neuron cell bodies in the PNS.

Glial Cells

• Supporting cells in the nervous system.

Myelin Sheath

• Fatty insulation around neurons, speeds signal conduction.

Multiple Sclerosis

• Myelin sheath destruction, impacting signal transmission.

Synapses

• Junctions where neurons communicate.

Neurotransmitters

• Chemical messengers transmitting signals between neurons.

Peripheral Nervous System Divisions

• Sensory division: Input from receptors.
• Motor division: Output to muscles/glands.
  • Somatic nervous system: Voluntary control.
  • Autonomic nervous system: Involuntary control.

Peripheral Nerves

• Most nerves are both sensory and motor. Sensory nerves carry input.

Dorsal Root

• Sensory input to the spinal cord.

Ventral Root

• Motor output from the spinal cord.

Proprioceptors

• Receptors in muscles/tendons/joints monitoring position and movement.

Static/Dynamic Equilibrium

• Static: Body position.
• Dynamic: Body movement/acceleration.

Sight

• Light passes through the lens and projects onto the retina. Focal point determines vision clarity.

Myopia

• Nearsightedness. Focal point in front of the retina. Fixed with concave lens.

Hypermetropia (Hyperopia)

• Farsightedness. Focal point behind the retina. Fixed with convex lens.

Retina

• Light-sensitive layer at the back of the eye containing photoreceptor cells.

Motor Nerve Cells

• Conduct impulses from the brain to muscles/glands.

Motor Unit

• Motor neuron and all muscle fibers it innervates.

Neuromuscular Junction

• Synapse between motor neuron and muscle fiber.

Skeletal Muscle Stimulation

• Short action potential triggers a short twitch. Maximal power with no relaxation between pulses.

Antagonistic Action

• Opposing muscle action.

Sympathetic/Parasympathetic Nervous Systems

• Sympathetic: "Fight or flight," increases activity, spinal cord centers.
• Parasympathetic: "Rest and digest," decreases activity, brain stem and spinal cord centers.

Cerebrospinal Fluid

• Fluid cushioning and protecting the CNS.

Spinal Cord Functions

• Conduction, signal processing, and reflexes.

Tendon/Stretch Reflex

• Sensory signal to spinal cord synapses with motor neuron.

Crossed Extensor Reflex

• When one leg withdraws, the opposite leg extends.

Cerebrum

• Area of the brain responsible for voluntary movement, sensory perception, thinking, etc.

Cortex

• Outermost layer of the brain, responsible for higher-level functions.

Frontal Lobe

• Rational behavior, motor control.

Parietal Lobe

• Sensory information, language processing.

Occipital Lobe

• Visual processing.

Temporal Lobe

• Memory and learning related functions.

Primary Motor Area

• Plans and executes voluntary movement.

Thalamus

• Relay center for sensory information.

Basal Ganglia

• Regulates voluntary movement, procedural learning, and habits.

Parkinson's Disease

• Degeneration of dopamine-releasing neurons in the basal ganglia, causing tremors, rigidity, etc.

Cerebellum

• Coordinates movement, posture, and balance.

Limbic System

• Involved in emotions, motivation, and memory.

Amygdala

• Processes emotions, particularly fear and aggression.

"Happy Chemicals"

• Serotonin: Significance, importance.
• Dopamine: Gratification, satisfaction.
• Oxytocin: Social bonding.
• Endorphins: Pain relief.

Hippocampus

• Processes memories into long-term storage; crucial for learning.

Referred Pain

• Pain felt in a location other than where the pain originates.