Homeostasis and Stress Overview

The body's ability to maintain a stable internal environment, even when external conditions change. Think of it as a constant balancing act.

A process in which the body detects a change and then initiates a response to counteract that change, bringing the body back to its set point.

A process in which the body detects a change and then amplifies that change, pushing the body further away from its set point.

A group of organs that work together to perform a specific function.

The smallest unit of life that can carry out all the processes of life.

A measure of the acidity or alkalinity of a solution, with a scale from 0 to 14. Lower pH values indicate a higher concentration of hydrogen ions (H+), making the solution acidic. Higher pH values indicate a lower concentration of H+, making the solution alkaline or basic. A pH of 7 is neutral.

The process by which cells break down glucose (sugar) in the presence of oxygen to produce energy (ATP), carbon dioxide, and water. It's a fundamental process for life!

A metabolic pathway that breaks down glucose into pyruvate, producing a small amount of ATP (energy) and NADH. This occurs in the cytoplasm of the cell.

A series of chemical reactions that take place in the mitochondria, where pyruvate is further broken down to produce ATP, NADH, and FADH2. This is the second stage of cellular respiration.

A series of protein complexes embedded in the mitochondrial membrane that use the energy from electrons carried by NADH and FADH2 to produce a large amount of ATP. This is the third and final stage of cellular respiration.

A membrane protein that binds to a specific signaling molecule (ligand), triggering a cellular response. Think of it as a lock and key mechanism where the ligand is the key that activates the receptor.

Passive transport that moves molecules across a membrane from a region of high concentration to a region of low concentration without requiring energy. It's like letting a ball roll downhill.

The process by which a cell makes a copy of its DNA, resulting in two identical DNA molecules. It's like photocopying a document.

The process by which the genetic code in DNA is copied into mRNA. It's like translating a recipe from one language to another.

The process by which the genetic code in mRNA is used to create a protein. It's like building a protein from Lego blocks.

Supports and protects organs, provides framework for movement, produces blood cells, stores minerals, and stores fat.

Dense, solid bone tissue found on the outside of bones, providing strength and support.

Lightweight, porous bone tissue found inside bones, providing flexibility and housing bone marrow.

The process of bone formation, where bone tissue is formed from pre-existing connective tissue.

Bone formation that begins with a cartilage model, gradually replaced by bone tissue.

A fibrous joint where two bones are joined by a thin layer of dense connective tissue. Think of a ligament holding bones together tightly.

A type of joint where a tooth is embedded in a socket within the jawbone, providing a secure connection. Think of a peg fitting snugly into a hole.

This type of joint allows for limited movement, with bones connected by cartilage. Think of the rib cage, where ribs are connected to the sternum by cartilage.

The ability of muscle cells to respond to stimuli, typically by generating an electrical signal.

The ability of muscle cells to shorten and generate force, pulling on bones to create movement.

The ability of muscle cells to be stretched or lengthened, allowing for muscle relaxation and elongation after contraction.

The ability of muscle cells to return to their original shape after being stretched or contracted.

The basic unit of muscle contraction, composed of repeating units of thick and thin filaments within a muscle fiber.

Hormones secreted by the hypothalamus include releasing hormones (stimulating the anterior pituitary) and inhibiting hormones (suppressing the anterior pituitary). Think of them as the "command center" for the pituitary gland.

The anterior pituitary secretes various hormones that control other glands, including thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), and growth hormone (GH). These hormones are often referred to as "tropic hormones" because they stimulate other glands.

The posterior pituitary is an "extension" of the hypothalamus, releasing hormones produced in hypothalamic neurons: antidiuretic hormone (ADH) and oxytocin. These hormones act directly on target tissues.

Hormonal effects can be amplified or diminished by interaction: Permissive - one hormone enables the activity of another (e.g., thyroid hormone allows for full epinephrine effect). Antagonistic - hormones counteract each other's effects (e.g., insulin vs. glucagon). Synergistic - hormones work together to produce a larger effect (e.g., FSH and LH for ovulation).

Most hormone systems operate under negative feedback, where an increase in the target hormone level inhibits its further production. This keeps hormone levels within a narrow range. Positive feedback is less common, where an increase in a hormone stimulates further production of that hormone. Think of the amplification loop!