Homeostasis

internal change

___ ___ results on loss of homeostasis, organisms have to do something to go back to a normal range

homeostasis

the body’s ability to maintain a relatively stable internal environment by keeping regulated variables within a narrow range

• ex: temp., blood pressure

homeostatic regulatory system

an active regulatory mechanism that minimizes changes to the internal environment to maintain homeostasis

Regulated variable, sensors, integrating center, effectors, reponse

What are the steps that are invovled in a response loop pathway

regulated variables

a variable that is actively controlled to stay constant over time

• ex: body temp., blood glucose, blood pressure

Set point

the base value around which the normal range of the regulated variable fluctuations

• ex: body temp.

Sensor

detects change in the internal or external environment

Integrating Center

receives information from the sensor and initiates a response to maintain a set point

effectors

a physical entity (cell, tissue, organ) that can bring about a physiological response

• ex: sweat glands, blood vessels

response

change to the regulated variable

• ex: blood vessels dilates (effector)→ cools body (response) sweat glands secrete sweat (effector)→ cools body (response)

negative feedback

when the sensor detects that the regulated variable is back at its set point (it did its job) and the integrating center no longer needs to activate effectors

• truly homeostatic

• stops the response once it reaches its set point

positive feedback

not homeostatic (does nothing to stop the change), response enhances or amplifies a change, regulated variable continues to move in the direction of the initial change

• ex: oxytocin causes the uterus to continually contract leading to childbirth

1. Nervous System

2. Tonic Control

3. Antagonistic Control

4. Tissue Specific Effects

What are the steps to Cannon’s Postulates of homeostasis

nervouse system

plays a key role in maintaining the internal environment, monitors regulated variables and adjusts effector activity to keep them within an appropriate range

Tonic control

the level of the variables is adjusting by increasing or decreasing the intensity of the signal, does not turn off or not it varies by strength

• ex: blood vessel diameter

Tissue Specific Effect

chemical signals, a signal chemical messengers can produce different effects, depends on receptor type and intracellular signaling pathway

• ex: epinephrine causes