Endocrine system Flashcards
Difference between endocrine and exocrine glands?
Endocrine = ductless glands
Exocrine = sebaceous glands/sweat glands in integumentary system; contains an acinus which has a duct for secretion/release of their products
What is autocrine, paracrine and neurocrine?
Autocrine = A > hormone > A response
- some cell producing hormone is some cell influenced by that hormon
Paracrine = A > hormone > B response
- Hormone travels to a nearby cell inducing appropriate responses
Neurocrine = Neuron > hormone > bloodstream > B > response
WHat is a hormone?
A chemical substance released in the ECF that regulates the metabolic functions of other cells in the body
What are important characteristics about hormones?
- Hormones must bind to specific receptors to influence target cell functions
- Hormones are specific - they can only influence target cells that express receptors for it, the level of target cell activation depends on;
a) hormone concentration
b) target cell receptor content (if a cell expresses a lot of receptors, there is a stronger stimulation)
c) affinity of hormone for receptor (low affinity = hormone might bind to it or pass it by) i.e. how strongly that hormone is attracted to the receptor to bind to it
What is the main mechanism of action of a peptide/protein hormone?
A water soluble hormone so it cannot cross the plasma membrane
Bind to a cell surface receptor
Activation of membrane bound G protein
Production of 2nd messenger (cyclic AMP(
Activation of protein kinases to regulate activity of key enzymes, open/close channels
Protein kinases = able to phosphorylate targets
What is phosphodiesterase?
Enzyme that degrades leftover cAMP molecules
Important in bringing the stimulation to and end so that hormones can still later stimulate receptors when needed
what are steroid hormones?
Lipid soluble therefore they can enter the nucleus and activate gene transcription
Because they are lipid soluble they can easily cross the PM/nuclear membrane
what is a half life pertaining to a hormone?
the persistence of a hormone in the blood
steroid hormones tend to last longer in the bloodstream while peptide/proteins/amino acids usually diffuse out of the blood therefore staying there for a shorter period of time
what does the blood level of a hormone depend on?
- rate of synthesis
- rate of degradation/clearance from the blood (how long the hormone is being broken down for or removed from the blood)
Where is the one place during a hormonal response where the ratio is 1:1 in the sequence of products forming?
Between cylic AMP to the activated protein kinases because only 1 cAMP can bind to 1 protein kinase
Describe the 3 types of stimuli for a hormonal release
- Humoral stimuli; hormone secretion in direct response to a change in the blood level of a nutrient or ion (PTH and blood Ca+2)
- Neural stimuli; not as common (sympathetic NS and epinephrine release by the adrenal medulla)
- Hormonal stimuli; a 3 tierd system (hypothalamus, pituitary and target endocrine gland) - hypothalamic-pituitary axis
what is a portal system?
A set of 2 capillaries with direct communication via the veins (2 capillary beds connected through veins)
What type of stimuli is the hypothalamus?
Neural; produces a number of releasing factors (hormones) that travel to the anterior pituitary via the hypophyseal portal system
What structure connects the pituitary to the hypothalamus?
Infundibulum
What is the posterior lobe considered as?
A hormone storage area; releases hormones but does not produce them
