Human Biology Exam 2 Study Guide: Muscular, Respiratory, Digestive Systems & Genetics

Major Muscle Groups: Includes biceps, triceps, quadriceps, hamstrings, pectorals, and others.

• Muscles Sectioning Body Cavities: Diaphragm separates thoracic and abdominal cavities.

Electrical Impulses and Muscle Contraction

Muscle contraction is initiated by electrical impulses from motor neurons.

• Action Potential: A rapid change in membrane potential that triggers muscle contraction.

• Order of Events: Nerve impulse → release of neurotransmitter (acetylcholine) → depolarization of muscle cell → calcium release → contraction.

• Release of Molecules: Calcium ions are released from the sarcoplasmic reticulum, enabling contraction.

Types of Muscle Contractions

• Isotonic Contraction: Muscle changes length (movement occurs).

• Isometric Contraction: Muscle length remains the same (no movement, but tension increases).

Heat Generation

• Body Heat: Most human body heat is generated by muscle activity, especially during contraction.

Summary Table: Muscle Contraction Types

Type	Muscle Length	Movement
Isotonic	Changes	Yes
Isometric	Constant	No

Human Respiratory System

Significance of Breathing

Breathing is essential for gas exchange, supplying oxygen to tissues and removing carbon dioxide.

• Oxygen Transport: Oxygen-rich blood is pumped from the lungs to the heart, then distributed throughout the body.

• Respiratory Diseases: Includes asthma, bronchitis, emphysema, and pneumonia.

Structures of the Respiratory System

• Upper Respiratory System: Includes nose, nasal cavity, pharynx, larynx. Functions: filter, warm, and humidify air.

• Lower Respiratory System: Includes trachea, bronchi, lungs. Functions: gas exchange, air conduction.

Mechanics of Breathing

• Inhalation: Diaphragm and intercostal muscles contract, increasing thoracic volume and decreasing lung pressure.

• Exhalation: Muscles relax, thoracic volume decreases, lung pressure increases, air is expelled.

• Pressure Changes: $\Delta P = P_{atm} - P_{lung}$

• Intercostal Muscles: Assist in expanding and contracting the rib cage during breathing.

Blood Flow Through the Heart

• Order: Pulmonary veins → left atrium → left ventricle → aorta → body tissues.

Human Digestive System

Major Structures and Functions

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

• Major Structures: Mouth, esophagus, stomach, small intestine, large intestine, rectum.

• Accessory Organs: Liver, pancreas, gallbladder.

• Function of Enzymes: Catalyze breakdown of macromolecules; produced in salivary glands, stomach, pancreas, small intestine.

• Large Surface Area: Villi and microvilli in the small intestine increase absorption efficiency.

Metabolic Rates

• Basal Metabolic Rate (BMR): Energy expended at rest.

• Standard Metabolic Rate (SMR): Energy expenditure under specific conditions.

Digestion Process

• Peristalsis: Wave-like muscle contractions that move food through the digestive tract.

• "My Plate": A 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 in organisms.

• Genes: Segments of DNA that code for proteins.

• Chromosomes: Structures that organize and carry genes; humans have 23 pairs.

• Genome: The complete set of genetic material in an organism.

• Homologous Chromosomes: Chromosome pairs with the same genes but possibly different alleles.

• Karyotype: Visual representation of chromosome number and structure.

Genotype and Phenotype

• Genotype: The genetic makeup of an organism.

• Phenotype: The observable traits resulting from genotype and environment.

Punnett Square and Alleles

• Punnett Square: Diagram used to predict genetic crosses.

• Dominant Allele: Expressed when present ($A$).

• Recessive Allele: Expressed only when homozygous ($a$).

• Homozygous: Two identical alleles ($AA$ or $aa$).

• Heterozygous: Two different alleles ($Aa$).

Mendelian Laws

• Law of Segregation: Each parent passes one allele for each gene to offspring.

• Law of Independent Assortment: Genes for different traits are inherited independently.

Inheritance Patterns

• Incomplete Dominance: Heterozygote shows intermediate phenotype.

• Codominance: Both alleles are fully expressed (e.g., blood type $AB$).

• Polygenic Inheritance: Multiple genes influence a trait (e.g., skin color).

• Environmental Impact: Environment can modify phenotypic expression.

• Linked Genes: Genes located close together on a chromosome tend to be inherited together.

• New Allele Combinations: Occur during meiosis via crossing over.

• Sex-linked Genes: Genes located on sex chromosomes (e.g., X-linked traits).

• Nondisjunction: Failure of chromosomes to separate properly during meiosis, leading to abnormal chromosome numbers in gametes.

Summary Table: Types of Inheritance

Type	Phenotype Expression	Example
Dominant	Trait appears if allele present	Huntington's disease
Recessive	Trait appears only if homozygous	Cystic fibrosis
Incomplete Dominance	Intermediate phenotype	Red and white flowers produce pink
Codominance	Both alleles expressed	AB blood type
Polygenic	Multiple genes affect trait	Skin color

Example: A Punnett Square can be used to predict the probability of offspring inheriting certain traits.

Additional info: The notes above expand on brief review points with academic context, definitions, and examples to ensure completeness and clarity for exam preparation.