Homeostasis 2 Flashcards
Receptor (sensor)
detects change.. which sends a signal to a control centre
Control centre (integrator)
compares with normal level which sends a signal to an Effector
Effector
responds to change
a change in the bodys internal or external environment is detected by….
a recepter
A nerve impulse is sent along a ………… to the brain (control centre) then along a …….to the ……….
sensory neuron….. motor neuron … effector
…… are often glands which will respond by sending ……….. ….. called hormones into the blood
Effectors…. chemical messengers….
What are hormones?
Chemical messengers (signals) released by cells into the blood stream that are transported via the blood stream to act on distant target cells
60 + hormones identified by chemical structure
hormones are specific: (how/why)
only activate cells with tissues that posess the target receptor
What do target cells possess?
receptors that recognize the hormones, others do not possess this
Which two systems work together to control organs and tissues
Nervous system and Endocrine
Nervous system
responds quickly to environment changes
Endocrine system
takes longer but maintains control over long period of time
What is the endocrine system composed of (4)
-A system of ductless sensory organs
-endocrine glands secrete hormones directly into the blood
=blood transports hormones to target tissues
- hormones help the cells in the tissues to elicit a response to maintain homeostasis
Exocrine Glands
do notsecrete hormones into blood or extracellular fluid, into specific ducts that lead outside or into body cavities
ex. salivary glands sweat glands, mammary glands
protein hormones
are polar and water soluble range between 3-200 amino acids long
-cannot cross lipid bilayer, can combine with surface receptors
-causes a series of events and changes in cell
- insulin, growth hormone
Protein Hormone Pathway
-Protein hormones bind to cell membrane receptor molecules.
Receptor molecule changes shape.
-Signal activates and is sent inside the cell (through membrane)
-Signal calls for changes to occur (ie. enzyme release or activation, etc)
Glucagon
Hormone GLUCAGON binds to liver receptor cells → phosphate groups are added → enzyme activated → glycogen broken down to glucose
Steroid Hormones
Steroid hormones are made from a nonpolar cholesterol (lipid) precursor. They are not soluble in water, but are lipid soluble.
Can diffuse through phospholipid bilayer into target cells where they combine with receptor molecules in the cytosol
Then ‘hormone-receptor complex’ moves into nucleus and activates a gene to produce a specific protein
Ex. Testosterone and Estradiol
Steroid Hormone Pathway
-Steroid hormones cross membrane
-Bind to cell receptors (in cytosol or nucleus)
-Hormone-receptor complex binds to a gene control sequence
-Turns gene on/off
-Protein production is activated/deactivated and cell activity changes
Cells can only respond if they have…
receptors for hormones to bind to (in/out)
Hormone receptor complexes respond by…
turning them on and off
amplification
occurs when hormones bind to receptors. Proteins activated, activate other proteins
are hormone responses the same across species
- hormone response different among species
Peptide synthesis
synthesized as prohormones- require further processing (e.g. cleavage ) to activate