Endocrine System Flashcards
T/F: endocrine system is the first control system for homeostasis
F, it’s the second
- 1st is nervous system
Endocrine system is _____ acting, but lasts ______
- slower than nervous
- lasts longer
Endocrine system acts via…
hormones
Hormone functions will regulate…
- metabolic rate
- water and electrolyte balance
- cell proliferation
- reproductive organs
Hormones control changes to help the body cope with…
stress
Hormones are secreted in…
very small amounts by specialized cells
How are hormones carried?
via blood
Hormones act on…
receptors of target cells to alter function
Classifications of hormones by signaling pattern:
- endocrine
- neurocrine
- paracrine
- autocrine
How are endocrine hormones produced and how do they travel?
- produced by classical endocrine cells
- travel via blood to target tissue
How are neurocrine hormones released?
released by axonal ends of neurons into blood
What happens to paracrine hormones?
diffuses to different local cell types through ISF or gap junctions
What happens to autocrine hormones?
acts on itself or other identical cells via gap junctions
What regulates the release of hormones?
- feedback control (positive, negative, neural)
- chronotropic control
Describe negative feedback:
- most common
- brings body back to normal
- ex: relationship between pituitary and target glands
Describe positive feedback:
- less common
- amplifies effect of hormone
- brings it farther away from homeostasis
- self-limiting
Describe neural control:
- ANS alters hormone secretion
- changes are detected by nervous receptors (visual, auditory, etc)
Describe chronotropic control:
hormones are released based on rhythms which are genetically encoded or acquired
Examples of chronotropic control:
- circadian (24-25 hours)
- diurnal (day-night)
- ultradian (multiple times a day)
Which gland regulates the circadian clock?
pineal via release of melatonin
Types of chemicals that can act as hormones:
- amino acids (water or lipid soluble)
- proteins and peptides (water soluble)
- steroids (lipid soluble)
- prostanoids (paracrine/autocrine)
Amino acids are derived from…
- tyrosine
- tryptophan
Amino acids are released by…
exocytosis
Proteins and peptides are synthesized as ______ and accumulates into ______
- large precursor molecules
- vesicles
Examples of proteins and peptides:
- insulin
- ANP
- thyroid regulation hormone (TRH)
Steroids are derived from…
cholesterol
Steroids require _____ in the blood
protein carriers
Prostanoids are derived from…
arachidonic acid (unsaturated fatty acid)
T/F: prostanoids are stored
F, are immediately released after synthesis
Prostanoids act on….
membrane receptors coupled to G proteins on target tissues
What are the forms of hormones that affect the 1/2 life of it?
- free/active hormones
- prohormones
- carrier bound hormones
Describe free/active hormones:
- fast acting
- shortest 1/2 life
- can be degraded by enzymes
Describe prohormones:
- circulates as inactive precursor of water soluble hormones
- cleavage turns it into active
- prolongs 1/2 life
Describe carrier bound hormones:
- longest 1/2 life
- slowest response time
- binds to specific globulins made by liver
- carrier protects hormones from degradation
- reduces renal clearance
T/f: hormones are reversibly removed from plasma
F, irreversibly removed by target cell uptake, metabolic degradation, urinary and biliary excretion
What are the two major sites of hormone extraction and degradation?
- kidney
- liver
What types of hormones are filtered?
free hormones
In order for hormones to create a response, they must be…
- recognized and bound to specific receptor
- hormone-receptor complex has to be coupled to signal generating mech (2nd messengers) or act on itself
Secondary messengers alter…
- enzyme activity or concentration
- functional proteins
- structural proteins
What are the two receptor systems based on solubility?
- membrane
- intracellular
Plasma membrane receptors are activated by…
non-lipid soluble (NLS) hormones
How fast is the response of plasma membrane receptors?
seconds to minutes
Structure of membrane receptors:
large glycoproteins with specific extracellular binding sites
- located inside membrane
What happens when a hormone occupies a membrane receptor?
change in conformation of receptor
What is the % of available membrane receptors that creates the max biological action?
5-10%
What is upregulation of membrane receptors and when does it occur?
- increasing the number of membrane receptors
- hormones recruit their own receptor and enhance sensitivity of cell
- occurs when there is intermittent exposure to a lot of hormones
What is downregulation of membrane receptors and when does it occur?
- decrease in number of membrane receptors
- occurs when there is a lot of hormones for a sustained period of time
- lessens effect of chronic exposure
Phosphorylation and dephosphorylation of membrane receptors alters…
affinity of receptor, which can also be altered by pH, osmolarity, ion concentration, and substrate levels
