Feedback loops
Give an example of an effector and describe its role in the feedback loop
a muscle or a gland that brings about change to return a system to a set point
the maintenance of a constant state
homeostasis
What sensory cells detect changes in water potential?
osmoreceptors
The mechanism of action of the hormones adrenaline and glucagon
cyclic AMP second messenger system
a regulating chemical produced and secreted by an endocrine gland and carried in the blood to the cells, tissues, or organs on which it acts
What is a hormone?
What is negative feedback?
information fed back turns the system off
maintaining the chemical make-up, volume and features of blood and tissue fluid within ______ ______
what are normal ranges
where are osmoreceptors found?
hypothalamus
adrenaline binds to the ___________ receptor on the cell surface membrane of a liver cell. Binding actives a membrane protein called ______________.
adrenaline binds to the complementary receptor on the cell surface membrane of a liver cell. Binding actives a membrane protein called G Protein.
State two ways hormones have their action on cells
bind to complementary receptors on the cell surface membrane and active secondary messengers (insulin, glucagon, ADH- water soluble)
enter the cell (steroid hormones as they are lipid soluble and can pass through the phospholipid bilayer)
the desired level at which a system operates
This occurs when deviation from a set point causes changes that result in even greater deviation from the normal. Give an example.
positive feedback
ex: neurons, when a stimulus causes a small influx of sodium ions the permeability of the neuron to sodium increases causing even more rapid entry of ions
what happens to osmoreceptor cells when water potential of the blood is low?
they shrink which stimulates neurosecretory cells in the hypothalamus to produce ADH
The G Protein activates another membrane protein an __________ called adenylate cyclase. This converts ______ to cyclic AMP (2nd messenger) which binds to and activates a _____ protein.
This actives another membrane protein, an enzyme called adenylate cyclase. This converts ATP to cyclic AMP (2nd messenger) which binds to and activates a kinase protein.
Where are hormones produced?
endocrine glands
What monitors the set point?
Receptors- detect internal and external stimuli which indicate deviation from the set point
What behaviors can result in a lower water potential in the blood?
drinking too little water
sweating a lot
eating large amounts of salt
ADH travels along the neurons to what gland that secretes into the capillaries?
pituitary
There follows an enzyme _______ where enzymes are activated by ___________. This amplifies the signal as one enzyme can catalyze the ___________ of many enzymes.
There follows an enzyme cascade where enzymes are activated by phosphorylation. This amplifies the signal as one enzyme can catalyze the phosphorylation of many enzymes.
what are hormones many of?
proteins or polypeptides, some are steroids
What is the role of central control in homeostasis?
coordinates information from various soures and sends instructions for a response
What are the two types of glands and what is different about them?
Exocrine glands transport secretions to the site of action by ducts i.e. saliva and pancreatic juice
Endocrine glands are ductless and secrete hormones directly into the blood
Where does ADH act and how does it affect?
kidneys; increases permeability to water of the cells of the distal convoluted tubule and collecting duct
The last enzyme catalyses the breakdown of _______ to glucose.
The last enzyme catalyses the breakdown of glycogen to glucose.
Describe three features of hormones
effective in relatively small amounts
often have widespread and permanent effects
transported through the blood
relatively small molecules