plant versus animal hormones

-p.h. produced by any actively growing part of plant / a.h. produced by specialized endocrine glands and neurosecretory cells

-a.h travel through blood and can reach distant parts of plant

-p.h. usually have the same effect on all the cells they reach (except auxins) / a.h. bind to very specific target tissues and only have an effect there

endocrine system compared to nervous system

endocrine system responds to stimuli on a more long term basis

can take minutes, hours, or days to act because hormones may take a long time to be synthesized and travel to target cells

1. bind to a receptor

2. activate, inactivate, or trigger some activity in target cell

3. signal amplification: one hormone molecule has a big effect

steroids

-sex (testosterone, androgen)

-corticosteroids (cortisol)

peptides

-chains of less than 100 amino acids (insulin)

glycoproteins

-longer polypeptide chains (FSH/LH)

amines

-secreted by thyroid, modified AA, (epinephrine)

lipophilic

after passing through phospholipid bilayer (cell membrane), binds to specific receptor protein

-receptor protein and hormone enter nucleus together

-now that receptor protein has been activated by hormone, it causes DNA to synthesize new proteins (different from itself)

can't diffuse through cel membrane so they do one of two things.

1. bind to a receptor and be carried through the membrane

2. use a second messenger system

2nd messenger system

one way a hydrophilic hormone affects cell

-can't get through plasma membrane so it binds to a receptor embedded in membrane

-this sends a signal to 2nd messenger (in cell) which has an effect in the cell

-typically activate or inactivate enzyme

endocrine gland

secrete stuff (enzymes) through ducts

i.e. sweat glands and digestive enzymes

first hormone released in digestion

upon seeing, smelling, tasting, thinking about food, gastrin cause stomach to start producing pepsin and HCL

-upon eating more gastrin released and more pepsin and HCL released (positive feedback loop)

digestive hormone

-if acid products of digestion (HCL) enters duodenum, secretin is released from duodenum which stimulates pancreas to secrete digestive enzymes into duodenum

3rd hormone released in digestion

-fats in partially digested materials in duodenum stimulate cck release

-cck stimulates gall bladder to release bile

last hormone released in digestion

-stops digestive cycle

-inhibits secretion of previous three hormones and shuts off digestive process when no more partially digested material present

endocrine cells in pancreas

-two types:

alpha - secrete glucagon

beta - secrete insulin

makes excess glucose in blood get stored in muscles (glycogen) and fat tissue (fat) 

-essentially lowers blood sugar

normal digestive processes

-after meal, hepatic portal vein brings glucose, AA, etc. to liver

-liver removes surplus and stores glucose as glycogen

-between meals, liver releases gylocgen into blood as glucose

-muscle stores gluscoes as glycogen and adipose tissue stores it as fat

stimulates glucose uptake by muscles and adipose tissue

-inhibits glycogen from breaking down (into glucose)

-changes to glucose to glycogen in liver and muscles

-promotes synthesis of fats from glucose

-hormone that counteracts insulin

-makes glycogen get released into blood as glucose

-produced in alpha islets in pancreas

results from too much insulin

-also called insulin shock

-too little sugar

-cells lack glucose, can't do cell. resp.

-results in cell death and first cells to die are nerve cells

-can result from too much insulin injection (diabetic) or pancreatic tumor

to much blood sugar

-not enough insulin

-causes weakness, dehydration

juvenile onset

-islet cells fail to secrete insulin

adult onset

-insulin production normal but either removed by liver or fails to stimulate target cells

extension of the hypothalamus (brain) and composed of nervous tissue

-stores and secretes hormones made in the hypothalamus

non-nervous tissue

glandular tissue

synthesizes its own hormones, which may control other endocrine glands

thyroid stimulating hormone

released by anterior pit.

tropic

adrenocorticotropic hormone

-stimulates the adrenal cortex (in adrenal gland on top of kidney)

-released by ant pit.

tropic

growth hormone

-stimulates development and enlargement of all body parts

-triggered by GHRH from hypothalamus

-not tropic

-too much GH and cause giantism, too little can cause dwarfism

-released by anterior pit.

gonadotropic hormones

aka gonadotropins

follicle stimulating hormone

tropic

stimulates follicle to develop into egg

-released from the anterior pit.

lutenizing hormone

-tropic

-released by anterior pit

-triggers ovulation in female

-stimulates production of testosterone in males

PRL

prolactin

-stimulates mammary glands in mammals to produce milk

-regulates larval development in amphibians

comes from anterior pit.

melanocyte-stimulating hormone

-stimulates melanocyte in amphibians

-released from ant. pit.

hormone released by the POSTERIOR pituitary

-stimulates muscles of uterus to contract during childbirth

-also helps mammary glands produce milk

antidiuretic hormone

aka vassopressin

-released by the POSTERIOR PITUITARY

makes collecting duct more permeable to water ultimnately resulting in more concentrated urine (more H₂0 uptake by peritubular capillaries)

secretes releasing hormones: make the ant pit. secrete hormones

 and secretes inhibiting hormones: make the ant. pit. stop secreting hormones

-these hormones are secreted by neurosecretory cells at the base of the hypothalamus into small vessels leading to the Ant. pit.

TSH, ACTH, gonadotropins

-negative feedback mechanisms control these hormones

-hormones secreted by the secondary glands result in negative feedback on tropic hormones

growth hormone releasing hormone

triggers ant. pit. to release GH

if it ends in RH (releasing hormone), it's from the hypothalamus

endorphins

type of hormone

body's natural painkillers

-released by ant. pit.