9.1/2 Homeostasis Flashcards
What is homeostasis?
The maintenance of a dynamic equilibrium within narrow limits through responses of the body
What levels must be maintained in the body?
pH
Core temperature
Water potential
Why must pH levels be maintained?
Too high - enzymes denature
Need them at their optimum pH
Why must temperature be maintained
Enough Ke for E-S complexes to be made
Why must water potential be maintained?
To avoid damage to cells
What is a negative feedback system?
When a change in conditions is detected by receptors and the body opposes the change to restore the equilibrium
What is a positive feedback system?
When a change in conditions is detected by receptors and is amplified, increasing the effect
What are hormones?
Proteins/peptides produced in the endocrine glands that are then released into the blood
Where are hormones produced?
Endocrine glands
How are hormones transported through the body?
Through the blood
What is the difference between endocrine and exocrine glands?
Exocrine - release hormones into small tubes or ducts
Endocrine - release straight into the blood
What does the pituitary gland do
Produces hormones which affect the endocrine glands
What controls the pituitary gland?
Hypothalamus
What are the two modes of hormone action?
Release of second messenger
Enter straight into cell
When do hormones cause the release of a second messenger?
When the hormone isn’t lipid soluble and can’t leave through the phospholipid bilayer
Explain how second messengers work
Hormones can’t pass through the cell membrane
Bind to receptors on the cell surface membrane
Triggers membrane bound reactions
Forms secondary messenger
Activates enzymes - changes metabolism
Name a second messenger?
cAMP
Name a hormone which works by a second messenger model
Adrenaline
How do hormones bring about change by entering cells?
Pass through lipid membrane
Enters cell and binds to receptor
Receptor-hormone complex passes into nucleus
Acts as a transcription factor and turns genes on or off
