Physiology: Homeostasis and Body Systems Flashcards

Question 1

What is Homeostasis?

Accepted Answer

The active maintenance of a relatively stable internal environment, such as temperature, pH, and blood glucose, within narrow limits despite changes in the outside world or the body's own activity.

Question 2

Define Set Point.

Accepted Answer

The target value a regulated variable is held near, against which the body compares the current value to decide whether a correction is needed.

Question 3

Define Negative Feedback.

Accepted Answer

A control loop in which the response opposes and reduces the original change, pushing the variable back toward its set point; it is the mechanism behind almost all homeostasis.

Question 4

Define Positive Feedback.

Accepted Answer

A control loop in which the response amplifies the original change, driving the variable further from its starting value until an outside event ends the cycle; it is used for rapid, one-way processes.

Question 5

Define Feedback Loop.

Accepted Answer

The complete regulatory circuit that senses a variable, compares it to a set point, and drives a response, made of a receptor, a control center, and an effector.

Question 6

Define Receptor (Sensor).

Accepted Answer

The component of a feedback loop that detects a change in the regulated variable and sends that information toward the control center as an input signal.

Question 7

Define Control Center.

Accepted Answer

The part of a feedback loop, often a region of the brain, that receives sensor input, compares it to the set point, and decides the size and direction of the response.

Question 8

What is Effector?

Accepted Answer

The component of a feedback loop, usually a muscle or gland, that carries out the response ordered by the control center and changes the regulated variable.

Question 9

Define Afferent Pathway.

Accepted Answer

The route that carries a signal from a sensory receptor toward the control center; in the nervous system it is the incoming, sensory direction of information flow.

Question 10

Define Efferent Pathway.

Accepted Answer

The route that carries a command away from the control center toward an effector; in the nervous system it is the outgoing, motor direction of information flow.

Question 11

Define Dynamic Equilibrium.

Accepted Answer

A steady overall state that is maintained by continuous, balanced activity rather than by stillness, so the variable stays near constant while its inputs and outputs keep flowing.

Question 12

Define Concentration Gradient.

Accepted Answer

A difference in the amount of a substance between two regions; substances tend to move down the gradient, from where they are more concentrated to where they are less concentrated.

Question 13

What is Diffusion?

Accepted Answer

The passive net movement of particles from a region of higher concentration to one of lower concentration, requiring no cellular energy and driven by the particles' own random motion.

Question 14

What is Osmosis?

Accepted Answer

The passive movement of water across a selectively permeable membrane, from a region of higher water concentration toward one of lower water concentration, driven by solute differences.

Question 15

What is Tonicity?

Accepted Answer

The effect a solution has on cell volume, based on the concentration of solutes that cannot cross the membrane; it predicts whether a cell will swell, shrink, or stay the same.

Question 16

Define Active Transport.

Accepted Answer

The movement of a substance across a membrane against its concentration gradient using cellular energy, usually ATP, to power a protein pump.

Question 17

Define Resting Membrane Potential.

Accepted Answer

The steady voltage difference across the membrane of an unstimulated cell, typically about minus 70 millivolts inside relative to outside, maintained by ion gradients and selective permeability.

Question 18

Define Action Potential.

Accepted Answer

A rapid, all-or-none reversal and recovery of a cell's membrane voltage that travels along an excitable cell, allowing neurons and muscle cells to transmit signals over distance.

Question 19

What is Depolarization?

Accepted Answer

A phase of the action potential in which the membrane voltage becomes less negative, usually as sodium ions rush into the cell, moving the inside toward and past zero.

Question 20

What is Threshold?

Accepted Answer

The critical membrane voltage that a stimulus must reach to trigger an action potential; below it nothing fires, and at or above it a full action potential always follows.

Question 21

Define Autonomic Nervous System.

Accepted Answer

The division of the nervous system that controls involuntary functions such as heart rate, digestion, and glandular secretion, working automatically to keep internal conditions regulated.

Question 22

Define Sympathetic Division.

Accepted Answer

The branch of the autonomic nervous system that prepares the body for exertion or stress, raising heart rate, dilating airways, and shifting blood to muscles in the fight-or-flight response.

Question 23

Define Parasympathetic Division.

Accepted Answer

The branch of the autonomic nervous system that conserves energy and supports maintenance activities, slowing the heart and promoting digestion in the rest-and-digest state.

Question 24

What is Hormone?

Accepted Answer

A chemical messenger released by an endocrine gland into the blood that travels to distant target cells and changes their activity, giving the body slow but widespread control.

Question 25

What is Insulin?

Accepted Answer

A hormone from the pancreas that lowers blood glucose by helping cells take up glucose and by promoting its storage as glycogen, released when blood sugar rises.

Question 26

What is Glucagon?

Accepted Answer

A hormone from the pancreas that raises blood glucose by signaling the liver to break down glycogen and release glucose, released when blood sugar falls.

Question 27

Define Antidiuretic Hormone (ADH).

Accepted Answer

A hormone that tells the kidneys to reabsorb more water, concentrating the urine and conserving body fluid; it is released when the blood becomes too concentrated or blood volume falls.

Question 28

What is Aldosterone?

Accepted Answer

A hormone from the adrenal cortex that tells the kidneys to reabsorb sodium and, with it, water, raising blood volume and blood pressure while promoting potassium loss.

Question 29

What is Baroreceptor?

Accepted Answer

A stretch-sensitive receptor in the walls of large arteries that detects changes in blood pressure and reports them to the brainstem so heart rate and vessel tone can be adjusted.

Question 30

Define Cardiac Output.

Accepted Answer

The volume of blood the heart pumps per minute, equal to heart rate multiplied by stroke volume; it sets how much oxygen and nutrients the body can deliver.

Question 31

Define Mean Arterial Pressure (MAP).

Accepted Answer

The average pressure driving blood through the systemic circulation over one cardiac cycle; it must stay high enough to perfuse organs but not so high that vessels are damaged.

Question 32

What is Nephron?

Accepted Answer

The functional filtering unit of the kidney that filters blood, reabsorbs needed water and solutes, secretes wastes, and produces urine, letting the body regulate fluid and electrolytes.

Question 33

Define Partial Pressure.

Accepted Answer

The pressure contributed by a single gas within a mixture; gases move by diffusion from where their partial pressure is higher to where it is lower, driving gas exchange.

Question 34

What is Buffer?

Accepted Answer

A chemical system that resists changes in pH by absorbing or releasing hydrogen ions, keeping body fluids within the narrow range enzymes need to work.

Question 35

What is Thermoregulation?

Accepted Answer

The homeostatic control of body temperature, balancing heat gained from metabolism and the environment against heat lost, mainly through the skin and controlled by the hypothalamus.