L1 Cell Physiology Flashcards
What is homeostasis?
The ability to maintain a relatively stable internal environment in an ever-changing outside world
What do pyrogens do?
Cause a rise in the sETPOINT for metabolic heat production
Where do exogenous pyrogens come from?
Foreign substances like bacteria or viruses
Where do endogenous pyrogens come from?
Produced by immune cells in response to infection
What are the components of a negative feedback system?
Sensor
Integrator
Effector
What order is the HPA axis in?
Hypothalamus
Anterior pituitary
Adrenal cortex
What hormone does the hypothalamus send to the anterior pituitary
Corticotropin releasing hormone
What hormone does the anterior pituitary send to the adrenal cortex?
Adrenocorticotropic Hormone (ACTH)
What hormone does the adrenal cortex release?
Cortisol
Where is the problem in the HPA axis when you have Addison’s disease?
Adrenal cortex messed up. No cortisol gets released
What are CRH, ACTH, and Cortisol levels like in Addison’s disease (primary hypoadrenocorticism)/
CRH: High
ACTH: High
Cortisol: None
(No cortisol to negatively feedback to the hypothalamus and the ant pituitary so they keep producing their hormones)
What is the problem with Secondary adrenal insufficiency?
Very little ACTH gets released from anterior pituitary
What are the levels of CRH, ACTH, and Cortisol like in secondary adrenal insufficeieny?
CRH: high
ACTH: low
Cortisol: low
How do you tell if someone has Primary hypoadrenocorticism (Addison’s) vs Secondary Adrenal insufficiency?
Give them ACTH and see what happens to Cortisol levels.
In primary, Cortisol levels will not increase
In secondary, cortisol levels will increase
What are 2 examples of Feedforward feedback?
Racer on block gets an increased heart rate in preparation for race
Smelling food gets your stomach going in preparation of eating
What causes illness and death
disruption in homeostasis
