Flashcards in Option D.5 Hormones and metabolism (AHL) Deck (44)
Where are hormones secreted from?
From Endocrine glands (ductless glands) directly into bloodstream
Outline journey of hormones
Secreted from endocrina glands;
in small quantity;
travels directly via bloodstream (only briefly);
to TARGET CELLS/ORGANS;
control and coordinate several body activities;
unused hormones are broken down in liver;
must be excreted continuously
What is the difference between hormone and nervous system?
- quick, precise communication
- specific changes in metabolism and development (extended period)
BOTH coordinated by brain
Which human organ is the only one that has endocrine and exocrine glands?
Contrast Endocrine and exocrine glands
- secrete hormones
- deliver directly via bloodstream
- at target organs, triggers specific metabolic reactions
- secrete (digestive) enzymes
- deliver via ducts (lumen of a gut or body surface)
Give example of an endocrine gland
- secrete anti diuretic hormone; targeted at collecting ducts of kidney tubules
- sex hormones; targeted at gonads
- secrete melatonin; targeted at tissues/organs responding to our body clock
Give example of an exocrine gland
- sweat on skin surface
- saliva into mouth
- gastric juice into stomach
What are the three chemical categories of hormones?
steroid derived from cholesterol;
What is an example of a tyrosine derivative hormone?
thyroxin - four iodine atoms
What is an example of a peptide hormone?
insulin; FSH; LH
what is an example of a steroid hormone?
How do lipid soluble hormones influence metabolism?
- diffuse into blood through lipid bilayer of plasma membrane;
- hormone binds to receptor (cytoplasm or in nucleus)
- receptor is activated, alters expression of genes
How do receptor hormones promote the transcription of specific genes
receptor hormone complex can:
cause activation of gene
- transcribes RNA
- RNA leaves nucleus
- directs formation of protein
- new protein brings functional/structural change to cell;
can turn off gene
- interrupts cell process
What are water soluble hormones?
- CANNOT pass through membrane directly
- bind to receptors in plasma membrane of target cell
What are second messengers?
small water soluble molecules that
- quickly spread throughout cytoplasm
- relay signals through out cells
What are the most common second messengers?
calcium ions and cAMP
What is the role of second messengers?
binding hormones causes CASCADE EFFECT:
- activation of enzymes in membrane
- ATP converted into cAMP
- cAMP activates protein kinase enzymes;
- this adds phosphate to enzymes
- can activate enzyme /or inactivate
What happens to cAMP after a brief period of use?
inactivated by enzyme; impact of hormone (it was helping) terminates
Outline role of second messenger using example of a specific hormone
- under threat, organism needs blood glucose (energy)
- epinephrine released and reaches liver
- binds to G protein couple receptor
- G protein activated
- activates adenylyl cyclase to convert ATP to cAMP
- CAMP activates protein kinase enzyme;
- activates glycogen breakdown
What is hypothalamus?
part of brain has major endocrine functions;
well supplied with blood vessels;
site of special neurons
What are the key roles of hypothalamus?
monitoring blood composition;
maintenance of internal environment - homeostasis
What does the pituitary gland consist of?
anterior pituitary and posterior pituitary
How does the hypothalamus control endocrine activity of pituitary glands?
hypothalamus releases hormones from neurosecretory cells; into portal vein;
nerve impulses via neurons connected
What is a neurosecretory cell?
type of neuron that secretes chemical messengers which travel around body via blood
What do hormones secreted by pituitary glands control?
growth, development changes in body tissue/organ, reproduction and homoeostasis
What does anterior pituitary do?
synthesizes and secrete hormones to control growth reproduction and homoeostasis
Example of anterior pituitary hormone
FSH and LH
What do posterior pituitary glands do?
secrete oxytocin and ADH, bu are NOT produced there
Where are hormones released by posterior pituitary gland synthesized?
neurosecretory cells; stored in ends of axons; secretion stimulated by hypothalamus