Homeostasis Flashcards
Target cells
Cells with the receptors
Ligands
chemical molecules that have binding site
Upregulation
cells become more sensitive, more receptors
Downregulation
cells become less sensitive, pulls receptors into cytosol
Agonists
Ligand binds to the receptor and triggers the response you’re supposed to trigger
Antagonists
Ligand binds to the receptor and completely blocks it, no response
two types of receptors
Intracellular receptor: Lipophilic
-Cytosolic or nuclear
-Bind steroid or thyroid hormones
-act as transcription factors
Membrane receptor: lipophobic
-are integral membrane proteins
-bind peptide hormones and other lipophobic signals
-usually activate a secondary messenger
Secondary messenger
When proteins activate and pass signal to another cell (start of signal transduction)
extracellular signal –> intracellular signal
examples of secondary messenger
cAMP and calcium
Steroid and peptide hormone actions
steroid = participate in new protein synthesis
peptide = response is to modulate existing protein inside the cell
What is the function of the plasma protein?
to carry steroid hormones
Cannon’s Postulates
-role of automatic nervous system in homeostasis (constantly monitoring)
-tonic activity
-antagonistic control (two systems where one increases and the other decreases)
-effects of chemical signals based on receptors
Homeostasis control systems
Input signal –> controller –> output signal
To maintain something in the body would it be negative or positive feedback?
Negative feedback
Localized and systemic responses (homeostasis)
Local control: paracrine
Systemic control (long distance): nervous and endocrine systems
Simple Neural Reflex
helps decrease tissue damage
ex: touching something hot and quickly move it back (muscle contract)
Simple endocrine reflex
When glucose levels high
-> insulin (second messenger) is released from Beta cell in response to high plasma glucose where liver takes up and stores glucose as glycogen and body cells take up more glucose.
When glucose levels low
->alpha cells release glucagon in blood and liver breaks down glycogen into glucose to release.
Positive feedback (goes in one direction)
- Blood clotting- to stop the bleeding
- Milk letdown reflex- release milk
- Giving birth- contraction and pushing
