Body Structure and Homeostasis Flashcards
Homeostasis
The tendency to resist change in order to maintain a stable, relatively consistent, internal environment.
Negative Feedback Loops
Feedback loop that acts to oppose the triggering stimulus
Positive Feedback Loops
Feedback loop that amplifies the starting signal
Set Points
Target values of Negative Feedback Loops
Insulin
decreases the concentration of glucose in the blood. After you eat a meal, your blood glucose levels rise, triggering the secretion of insulin from β cells in the pancreas. Insulin acts as a signal that triggers cells of the body, such as fat and muscle cells, to take up glucose for use as fuel. Insulin also causes glucose to be converted into glycogen—a storage molecule—in the liver. Both processes pull sugar out of the blood, bringing blood sugar levels down, reducing insulin secretion, and returning the whole system to homeostasis.
Glucagon
increases the concentration of glucose in the blood. If you haven’t eaten for a while, your blood glucose levels fall, triggering the release of glucagon from another group of pancreatic cells, the α cells. Glucagon acts on the liver, causing glycogen to be broken down into glucose and released into the bloodstream, causing blood sugar levels to go back up. This reduces glucagon secretion and brings the system back to homeostasis.
Glucose
Basic energy source for the body.
Diabetes
a disease caused by a broken feedback loop involving the hormone insulin. The broken feedback loop makes it difficult or impossible for the body to bring high blood sugar down to a healthy level.
Order of Body Organization
Cells –> Tissues –> Organs –> Organ Systems
Cells
Smallest units of life
Tissues
Made of a group of similar cells that work together on a specific task
Organs
Structure made up of two or more tissues, organized to carry out a specific function
Organ Systems
Groups of organs with related functions
Extracellular Fluid
Fluid outside of cells
Unicellular Organisms
Consist of only a single cell, ex. amoebas
Multicellular Organisms
Made up of many cells, ex. humans
Nervous Tissue
involved in sensing stimuli—external or internal cues—and processing and transmitting information.
Muscle Tissue
essential for keeping the body upright, allowing it to move, and even pumping blood and pushing food through the digestive tract.
Epithelial Tissue
consists of tightly packed sheets of cells that cover surfaces—including the outside of the body—and line body cavities.
Connective Tissue
consists of cells suspended in an extracellular matrix. In most cases, the matrix is made up of protein fibers like collagen and fibrin in a solid, liquid, or jellylike ground substance. Connective tissue supports and, as the name suggests, connects other tissues.
Types of Nervous Tissue
It consists of two main types of cells: neurons, or nerve cells, and glia.
Types of Muscle Tissue
Muscle cells, often called muscle fibers, contain the proteins actin and myosin, which allow them to contract. There are three main types of muscle: skeletal muscle, cardiac muscle, and smooth muscle.