Homeostasis-Lecture 1 Exam 1 Flashcards
Homeostasis
Ability of the body to maintain a relatively stable internal environment by keeping regulated variables (temperature, blood pressure, etc.) within a narrow range
Setpoint in Homeostasis
-The base value around which the normal range of the regulated variable fluctuates
-ex: body temperature
Regulated Variable in Homeostasis
-The stimulus
-A variable that is actively controlled to stay relatively constant over time
-ex: body temperature, blood glucose, blood pressure
Sensor in Homeostasis
Detects changes in the internal or external environment
Integrating Center in Homeostasis
Receives information from the sensor and initiates a response to maintain the set point
Effector in Homeostasis
-A physical entity (cell, tissue, organ) that can bring about a physiological response
-ex: sweat glands, blood vessel, etc.
Response in Homeostasis
-Change to the regulated variable
-ex: sweat gland secretes sweat (effector)-> cool body(response), skeletal muscle contracts(shivering)(effector)-> body warms(response)
Examples of Physiological Variables That are Regulated by Homeostasis
Body temperature, blood glucose, blood pressure
Steps in a Homeostatic Response Loop
Regulated Variable-> Sensor-> Integrating Center-> Effector(s)-> Response
Role of a negative feedback in terms of the relationship between stimulus & response and give an example
Negative feedback decreases the stimulus and the response is to stop to maintain homeostasis
-ex:body temp rises, target/effector(s) bring body temp down, sensors detect this change, and target/effectors stop bringing body temp down
Role of a positive feedback in terms of the relationship between stimulus and response and give an example
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
Which feedback loop (negative or positive) maintains homeostasis? Explain why
Negative feedback loop because it decreases the stimulus and the response is to stop to maintain homeostasis
Cannon’s 4 Postulates of Homeostasis
- The nervous system oversees and maintains the stability of the internal environment by monitoring regulated variables and initiating a response if the variable is too high or too low
- Some regulated variables are under tonic control
- Some regulated variables are under antagonistic control
- One chemical signal can have different effects in different tissues
Difference between tonic control and antagonistic control
-Tonic Control is when variables can be regulated in an up-down fashion (volume). The signal is always present, but its intensity can change.
-Antagonistic Control is one factor increases the response, and another factor decreases the response
How can one chemical signal have opposite effects in two different tissues?
By using different receptors or different signal pathways
