Comprehensive Notes on Anatomy, Physiology, and Homeostatic Systems Homeostasis
Levels of Biological Organization
Tissue: Defined as a group of cells that work together to perform a certain function.
Organ: Defined as two or more tissues that work together to perform a specific task.
Organ System: Defined as multiple organs that function together to perform a vital body function.
Organism: Defined as all the organ systems functioning together as an integrated unit.
Example Hierarchy:
Cardiac tissue (Tissue) connects to the Heart (Organ), which is part of the Circulatory system (Organ system) within a Human (Organism).
Major Organ Systems in Animals
Respiratory: Manages gas exchange.
Circulatory: Transports materials throughout the body.
Reproductive: Ensures the continuation of the species through the production of offspring.
Digestive: Processes food and absorbs nutrients.
Urinary (Excretory): Removes waste and balances fluids.
Immune: Protects the body against infection.
Nervous: Coordinates body activities via electrical signals.
Endocrine: Regulates body functions via chemical hormones.
The Respiratory and Circulatory Systems
System Integration: The respiratory and circulatory systems join forces to bring oxygen and nutrients to cells and maintain homeostasis regarding gas exchange.
Respiratory System Function: It moves gases into and out of the blood. Its primary function is to exchange oxygen and carbon dioxide within the body.
Respiratory Surface: This is the specific part of an animal where gases are exchanged with the environment.
Condition for Function: Respiratory surfaces must stay moist because gases must be dissolved in water before they can diffuse across these surfaces.
Example: In a newt, gas exchange occurs in the feathery gills located behind the head.
Circulatory System Function: It transports blood to all cells of the body.
Mechanisms of Exchange:
Every organism must exchange materials with the environment, occurring ultimately at the cellular level.
Simple Animals: Small, simple animals (like flatworms) exchange materials directly via diffusion.
Complex Animals: For large, complex animals, diffusion is insufficient. They require a circulatory system to bridge the distance between the environment and internal cells.
Reproductive System and Animal Development
Human Reproductive System: Consists of male and female systems working together as one unit.
Sexual Reproduction: Involves mixing genes where half of the genes come from the mother and half from the father, leading to genetic diversity in the population.
Haploid Sex Cells: The system produces haploid cells: sperm (produced by males) and eggs (produced by females).
Conception: Occurs when sperm and egg meet to form a fertilized egg (fusion).
Process of Gestation and Development:
Fertilization: Takes place in the fallopian tube if sperm is present.
Egg Movement: Both fertilized and unfertilized eggs move through the fallopian tube to the uterus over a period of days.
Zygote Formation: Following conception, the zygote undergoes several rounds of cell division to form an embryo and later a fetus.
Embryogenesis and Gastrulation: After forming a hollow ball of cells called a blastula, one end of the embryo folds in and expands to fill the space. This process, gastrulation, results in three primary germ layers:
Endoderm
Mesoderm
Ectoderm
Embryonic/Fetal Milestones:
At 8 weeks: The embryo is the size of a bean, is developing arms, legs, and organ systems, and is officially called a fetus.
At 12 weeks: All organ systems are beginning to function. The fetus has a fully functional placenta. The liver produces red blood cells, kidneys filter blood, fingernails develop, and bones begin hardening.
Growth Phase: For the remaining weeks, the fetus grows to become capable of living independently.
Pregnancy Duration: A typical pregnancy lasts weeks, though births commonly occur between and weeks.
Post-Birth: The system also enables birth and breastfeeding.
Digestive and Urinary Systems
Digestive System Functions:
Ingestion: The act of eating.
Digestion: Breaking food down into molecules small enough for absorption.
Absorption: The uptake of nutrients by the body's cells.
Elimination: Passing undigested material out of the body.
Urinary System Functions: Excretes urine and regulates the balance of water and ions in body fluids.
Survival Necessity: Animals must balance the need for water with the disposal of waste.
The Kidney: The crucial organ of the excretory system. It maintains homeostasis for all body systems by removing wastes and keeping the blood balanced.
The Immune System
Core Task: Responsible for fighting off infection and pathogens.
Modes of Defense:
Preventing Attacks: Relies on physical barriers like the skin and mucous membranes to exclude microorganisms.
Detecting Invaders: Uses the circulatory and lymphatic systems to transport white blood cells (WBCs) to infection sites once a pathogen enters the body.
Attacking Invaders: WBCs can attract more WBCs, engulf invaders, spray parasites with poison, and initiate immune responses.
Polypeptide Defense: Uses antibodies, interferons, and complement proteins to attack invaders.
Memory: The system "remembers" invaders, providing immunity so the person does not get sick if the same pathogen invades again.
The Nervous System
Main Functions:
Sensory Input: Receiving signals from sensory receptors.
Integration: Interpreting signals and forming appropriate responses.
Motor Output: Conducting signals from the integration center to effector organs (muscles or glands) to execute responses.
Divisions:
Central Nervous System (CNS): Comprised of the brain and spinal cord; acts as the primary processing center.
Peripheral Nervous System (PNS): Comprised of all other nerves; acts as "cables" carrying information to and away from the CNS.
The Endocrine System and Nervous Connection
Definition: Produces hormones that affect growth, development, and homeostasis.
Hormones: Chemical messengers produced by a gland, secreted into the blood, and carried to target parts of the body.
Targets: Some targets are broad (e.g., sex hormones affecting most tissues), while others are specific (e.g., glucagon acting only on specific cells).
Interconnectivity: The nervous system sends signals through the endocrine system.
Sympathetic Nervous System: Activates when a person is excited; triggers the "fight-or-flight" response.
Parasympathetic Nervous System: Sometimes called the "rest-and-digest" system; triggered when getting ready for lunch. It conserves energy, slows heart rate, increases intestinal/gland activity, and relaxes gastrointestinal sphincters.
Signaling Mechanism: Nervous system uses action potentials; endocrine system uses hormones.
Homeostasis and Feedback Systems
Homeostasis: The process of maintaining relatively constant internal conditions despite widely fluctuating external conditions.
Feedback Mechanisms:
Negative Feedback: A change in a variable triggers a mechanism that reverses that change (most common).
Positive Feedback: Homeostasis is regulated by magnifying a change instead of reversing it.
Examples of Hormonal and Behavioral Regulation
Urinary Homeostasis:
The adrenal gland secretes aldosterone to regulate the reabsorption and excretion of and ions.
Kidney function is fine-tuned by the nervous system and hormones to balance salt and water in the bloodstream.
Neuro-Endocrine Homeostasis:
Hypothalamus: Part of the brain and master controller of the Pituitary gland (the "master gland").
Antidiuretic Hormone (ADH): Secreted by the pituitary (under hypothalamic control); causes tubule cell membranes to allow more water to flow from tubules into capillaries.
Pituitary Hormones: Controls growth (Growth Hormone), reproduction (LH, FSH, prolactin, oxytocin), metabolic rate (ACTH, TSH), and blood pressure/excretion (ADH).
Blood Sugar Regulation (Pancreas):
The pancreas is located behind the stomach.
Insulin: Released during high blood sugar; allows muscle, fat, and liver cells to absorb glucose. It lowers blood sugar and promotes glycogen formation in the liver.
Glucagon: Released during low blood sugar; promotes the release of glucagon to stimulate glycogen breakdown into glucose, raising blood sugar.
Behavioral Responses: Humans seek warmth (clothes, sunlight) or curl their bodies to retain heat.
Endotherms: Regulate temperature internally via sweating or shivering.
Ectoderms: Must bask in the sun to raise body temperature.
Circadian Biological Clock: Controlled by cells in the hypothalamus that respond to light/dark signals from the retina.
Light Perception: Affects hormone production/suppression, body temperature, appetite, and sleep drive.
Diurnal vs. Nocturnal: Different organisms exhibit different sleep/wake responses to light signals.
Growth, Development, and Aging
Growth: An irreversible increase in an organism's size over time by making more cells. It may continue throughout life or stop at maturity.
Development: The process of maturing into another stage of life. Stages typically include embryonic, larval, metamorphosis, and adult phases (sexual maturity).
Preparation: In sexual reproduction, development must be prepared in the gonads of both parents.
Aging: This can be measured in two ways:
Functional Senescence: A decline in the body's performance.
Demographic Senescence: A decline in fertility rate coupled with an increased risk of mortality.