Study Notes: Muscular, Respiratory, Digestive Systems & Genetics for Medical Terminology

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Human Muscular System

Muscle Cell Structure and Sliding Mechanism

The human muscular system is essential for movement, posture, and heat production. Muscle contraction relies on the sliding filament mechanism within muscle cells (fibers).

Sarcomere: The basic contractile unit of muscle fiber, composed of actin (thin) and myosin (thick) filaments.
Sliding Filament Theory: Muscle contraction occurs when myosin heads bind to actin filaments and pull them inward, shortening the sarcomere.
Actin and Myosin: Actin forms the thin filaments; myosin forms the thick filaments with protruding heads that attach to actin during contraction.
Substructures of Sarcomere: Includes Z-lines (boundaries), A-band (length of myosin), I-band (actin only), H-zone (myosin only), and M-line (center).
Function of Sarcomere: Generates force for muscle contraction by shortening during the sliding of filaments.
Example: During biceps contraction, sarcomeres in muscle fibers shorten, pulling the forearm upward.

Additional info: The sarcoplasmic reticulum stores and releases calcium ions essential for contraction.

Muscle Contraction Mechanism

Muscle contraction is initiated by an electrical signal and involves a series of biochemical events.

Motor neuron releases neurotransmitter (acetylcholine) at neuromuscular junction.
Muscle cell membrane depolarizes, generating an action potential.
Calcium ions are released from the sarcoplasmic reticulum.
Calcium binds to troponin, shifting tropomyosin and exposing actin binding sites.
Myosin heads bind to actin, perform power stroke, and slide filaments.
ATP binds to myosin, causing detachment and resetting the cycle.

Isotonic vs. Isometric Contractions:
- Isotonic: Muscle changes length (movement occurs), e.g., lifting a weight.
- Isometric: Muscle length remains the same (no movement), e.g., holding a weight steady.
Heat Generation: Most body heat is generated by muscle activity (shivering thermogenesis).
Major Muscle Groups: Includes biceps, triceps, quadriceps, hamstrings, pectorals, abdominals, etc.
Muscles Sectioning Body Cavities: The diaphragm separates the thoracic and abdominal cavities.

Human Respiratory System

Significance and Structure

The respiratory system enables gas exchange, supplying oxygen and removing carbon dioxide, which is essential for cellular respiration and energy production.

Upper Respiratory System: Includes nose, nasal cavity, pharynx, and larynx. Functions: filters, warms, and humidifies air; protects lower tract.
Lower Respiratory System: Includes trachea, bronchi, bronchioles, and lungs. Functions: conducts air to alveoli, site of gas exchange.
Example: The nasal cavity traps dust and pathogens, protecting the lungs.

Mechanics of Breathing

Breathing involves coordinated muscle activity and pressure changes to move air in and out of the lungs.

Inhalation (Inspiration): Diaphragm and intercostal muscles contract, increasing thoracic volume and decreasing lung pressure, drawing air in.
Exhalation (Expiration): Muscles relax, thoracic volume decreases, lung pressure increases, pushing air out.
Pressure Changes: Air flows from high to low pressure; during inhalation, lung pressure drops below atmospheric pressure.
Intercostal Muscles: Assist in expanding and contracting the rib cage during breathing.

Equation:

where is the pressure difference, is atmospheric pressure, and is alveolar pressure.

Blood Flow and Gas Exchange

Oxygenated blood is transported from the lungs to the heart and then distributed throughout the body.

Oxygen-rich Blood Flow: Oxygenated blood returns from the lungs to the left atrium, then to the left ventricle, and is pumped to the body.
Order of Flow: Pulmonary veins → left atrium → left ventricle → aorta → systemic circulation.

Respiratory Diseases and Disorders

Several diseases can impair respiratory function and gas exchange.

Common Disorders: Asthma, bronchitis, emphysema, pneumonia, and lung cancer.
Significance: These conditions impair gas exchange and oxygen delivery.

Human Digestive System

Major Structures and Functions

The digestive system breaks down food, absorbs nutrients, and eliminates waste.

Main Structures: Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.
Accessory Organs: Salivary glands, liver, gallbladder, pancreas.
Function of Enzymes: Catalyze breakdown of macromolecules; produced in salivary glands, stomach, pancreas, and small intestine.
Large Surface Area: Villi and microvilli in the small intestine increase surface area for nutrient absorption.

Digestion and Absorption

Food is moved and digested through coordinated muscle contractions and enzyme activity.

Peristalsis: Wave-like muscle contractions that move food through the digestive tract.
Digestion of Molecules: Carbohydrates, proteins, and fats are digested by specific enzymes in different regions of the tract.

Metabolic Rates and Nutrition

Metabolic rates reflect the energy requirements of the body, and balanced nutrition is essential for health.

Basal Metabolic Rate (BMR): Energy expended at rest to maintain vital functions.
Standard Metabolic Rate (SMR): Energy expenditure under standardized conditions (often used in animals).
"My Plate": A visual guide for balanced nutrition, emphasizing fruits, vegetables, grains, protein, and dairy.

Human Genetics and Inheritance

Basic Concepts

Genetics is the scientific study of heredity and variation, focusing on how traits are passed from parents to offspring.

Genes: Segments of DNA that code for proteins; fundamental units of heredity.
Chromosomes: Structures made of DNA and proteins; humans have 23 pairs.
Genome: The complete set of genes in an organism.
Karyotype: A visual representation of all chromosomes in a cell, used to detect chromosomal abnormalities.

Inheritance Patterns

Traits are inherited according to specific patterns determined by the combination of alleles.

Homologous Chromosomes: Chromosome pairs with the same genes but possibly different alleles.
Genotype: The genetic makeup of an organism (e.g., AA, Aa, aa).
Phenotype: The observable traits resulting from the genotype.
Punnett Square: A tool to predict genetic crosses and offspring genotypes.

Alleles and Laws of Inheritance

Alleles are different forms of a gene, and their combination determines trait expression.

Dominant Allele: Expressed when present (e.g., A).
Recessive Allele: Expressed only when two copies are present (e.g., aa).
Homozygous: Two identical alleles (AA or aa).
Heterozygous: Two different alleles (Aa).
Law of Segregation: Each parent passes one allele for each gene to offspring.
Law of Independent Assortment: Genes for different traits are inherited independently.

Complex Patterns and Disorders

Some traits follow more complex inheritance patterns, and genetic disorders can arise from chromosomal or gene abnormalities.

Incomplete Dominance: Heterozygote shows intermediate phenotype (e.g., pink flowers from red and white parents).
Codominance: Both alleles are fully expressed (e.g., AB blood type).
Polygenic Inheritance: Multiple genes influence a trait (e.g., skin color).
Environmental Impact: Environment can affect phenotypic expression (e.g., nutrition, temperature).
Linked Genes: Genes located close together on the same chromosome tend to be inherited together.
New Allele Combinations: Crossing over during meiosis creates genetic diversity.
Sex-linked Genes: Genes located on sex chromosomes (X or Y); often show different inheritance patterns in males and females.
Nondisjunction: Failure of chromosomes to separate during meiosis, leading to abnormal chromosome numbers (e.g., Down syndrome).

Additional info: Some dominant disorders are lethal because a single copy of the allele disrupts vital functions; recessive disorders persist because carriers (heterozygotes) are unaffected and can pass the allele to offspring.

Key Genetics Terms Table

The following table summarizes important genetics terms and their definitions:

Term	Definition	Example
Genotype	Genetic makeup (allele combination)	AA, Aa, aa
Phenotype	Observable trait	Tall, short, blood type
Homozygous	Two identical alleles	AA or aa
Heterozygous	Two different alleles	Aa
Dominant	Expressed when present	A
Recessive	Expressed only if homozygous	a