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What is Autoregulation?

Automatic response in a cell, tissue, or organ

What is Extrinsic regulation?

Responses controlled by nervous and endocrine systems

What are the 5 steps of a control system?

1. Stimulus produces change in variable
2. Change detected by receptor
3. Input: Info sent along afferent pathway to control center
4. Output: Info sent along efferent pathway to effector
5. Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis

What are the five components of Negative Feedback Control system?

1. Regulated or controlled variable
2. Sensor - Receptor
3. Control center - Integrates and generates command signal if regulated variable is not equal to the set point value → error signal
4. Effector - Controlled system
5. Feedback

6 Examples of Negative Feedback

1. Blood pressure, blood volume
2. Oxygen and carbon dioxide tensions
3. Blood glucose concentration
4. Metabolite concentrations
5. End-product inhibition
6. Concentration of ions: H+, K+, Ca++, Mg++, Na+, Cl-, etc.

5 qualities of Negative Feedback

1. Promotes stability
2. Prevent sudden & severe changes within the body
3. A change in the variable being regulated brings about responses that tend to push the variable in the direction opposite to the original change (disturbance) - to ↓ disturbance or error
4. Minimizes change from the operating set point of the system, leading to stability
5. Response time is very quick

Example of quick time response of negative feedback

Baroreflex: You are lying down and then stand up quickly - at first you get dizzy, but within 4-5 sec, your head clears up

(Positive feedback cycle) Variable is sensed and action taken to ____ or _____ the change in the variable

reinforce or exaggerate

(Positive feedback cycle) Does not lead to stability or regulation - but to ______
The disturbance and the controller act in the ___ direction

a progressive change in one direction

Positive feedback, if unchecked, can lead to a ____ or cascade and dangerous situations

vicious cycle

7 Examples of Positive Feedback

1. Upstroke of the action potential in nerve and muscle
2. Calcium-induced calcium release from sarcoplasmic reticulum
3. Parturition - labor and birth - oxytocin
4. Ovulation
5. Circulatory Shock
6. Heat stroke
7. Blood clotting

What is Feedforward Control?

Information flows ahead to another process to trigger a change in anticipation of an event that will follow

4 examples of Feedforward Control?

1. Cephalic phase of digestion
2. Salivation, gastric secretions, motility occurs before food arrives in GI tract
3. Increased heart rate, respiration rate and depth prior to onset of exercise
4. Anxiety, stress response in anticipation of ...

Positive vs. Negative Feedback Control

(+): Exponential growth and divergent behavior
(-): Maintenance of equilibrium and convergent behavior

Failure of homeostasis results in _____


Departure from optimal conditions → _______

disordered function or disease

Examples of Homeostatic Imbalances

Hypertension: May result from overactive sympathetic vasoconstrictor response due to high levels of stress
Resetting of set point.

Circulatory Shock: Blood vessels inadequately filled and blood cannot circulate normally resulting in inadequate blood flow to meet tissues' needs. Reflex increase in HR, BP, vasoconstriction.

Heart Failure

The pancreas and liver work together to maintain homeostasis through?

A. a feedforward control system.
B. negative feedback control system.
C. positive feedback control system.
D. None of the above


A structure that is composed of two or more tissues would be a/an ?

A. complex cell.
B. complex tissue.
C. organ.
D. organ system.


A jogger has stepped in a pothole and sprained his ankle. Which organ systems
have suffered damage?

A. Cardiovascular and renal
B. Endocrine and gastrointestinal
C. Reproductive and respiratory
D. Skeletal and muscular


In congestive heart failure, the weakened heart is unable to pump with sufficient strength to empty its own chambers. As a result, blood backs up in the veins, blood pressure rises, and circulation is impaired. Which of the following will happen as this situation worsens owing to positive feedback?

A. Blood flow to the heart muscle increases as blood pressure decreases to improve the pumping ability of the heart muscle.
B. Blood pressure will continue to increase, which will decrease the workload of the heart.
C. Circulation of blood throughout the body will increase as blood pressure increases.
D. The heart will receive inadequate blood flow causing the heart to become weaker.

D, C is true but not answer

Predict how a heart-strengthening medication will reverse the positive feedback.

A. Decreases blood pressure and makes it easier for the heart to pump blood to vulnerable organs.
B. Decreases nerve stimulation of the heart such that the work of the heart decreases and becomes less vulnerable to ischemia.
C. Increases heart rate which decreases the volume of blood in the heart.
D. Increases the force of the heart beat and increases the amount of blood the heart pumps, thus improving delivery of blood to all organs.


Organization of the Body

Atoms (are the smallest chemical units) -> Molecules
(group of atoms working together) -> Organelles (group of molecules working together) -> Cells (group of organelles working together) -> Tissues (group of similar cells working together) -> Organs (group of different tissues working together) -> Organ systems (group of organs working together) ->
Organism -> Population (1 species) -> Ecosystem (multiple species) -> Biosphere

Organization of Heart Muscle

Protein molecules (chemical level)
Protein filaments (organelle level)
Muscle cells (cellular level)
Cardiac muscle tissue (tissue level)
Heart (organ level)

8 Necessary Life Functions

1. Maintain Boundaries - For constant internal environment ex. Kidneys for salt
2. Movement
3. Responsiveness - irritability, excitability
4. Digestion - ex. starch to glucoose
5. Metabolism
6. Excretion - rid waste products
7. Reproduction
8. Growth

5 Survival Needs of the Body

1. Nutrients: CHO, proteins, fats, Vitamins, minerals, electrolytes
2. Oxygen
3. Water (we r 60%)
4. Temperature (98.6)
5. Atmospheric pressure (barimeteric goes down as we ascend and vice versa)

Multicellular organisms are surrounded by an ______. But the cells in the body live in a liquid internal environment, ______. Most of our body cells interact with _______ through the ______

external environment (air or water)
the extracellular fluid
external world through the internal environment

Each cell in the body requires an ______ and _____

environment that supplies nutrients & removes metabolic wastes

What is Equilibration time?

time from when animals are placed in a new environment to when a response is measured at equilibrium (or death)

What is identity function?

where x = y, which is a model of no regulation

What is Homeostasis?

All body systems working together to maintain a stable internal environment

Homeostasis: The capacity to maintain stability of the internal environment by the presence of _______

regulatory mechanisms in the body

11 Body Conditions Maintained Within Narrow Limits

1. Osmotic pressure
2. Blood pressure
3. Core body temperature
4. Intracellular fluid
5. Extracellular fluid
e.g., blood volume, interstitial fluid
6. Oxygen concentrations
7. Carbon Dioxide concentrations
8. Glucose concentrations
9. Metabolites concentrations
10. Ion concentrations: H+, K+, Ca++, Mg++, Na+, Cl-, etc.
11. Red blood cell concentrations

Stable conditions achieved by _____ and ____ control systems

negative and positive feedback

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