LU9 Hormone & Endocrinology (Control and feedback (Hormone feedback…
LU9 Hormone & Endocrinology
Functions of hormone
one body part with another parts.
Coordinate body organs through
Definition of Hormone
that secreted into body fluid (blood) communicates regulatory messages within the body and only specific receptors on target cells will respond to that hormone.
hormones released from endocrine gland into extracellular fluid & circulatory system to other body parts
it binds to specific receptor of target tissue, initiate response and feedback mechanism
feedback signal stops or increases hormone production
chemical hormone produced by specialized cells present in each gland, then enter bloodstream to whole body.
slow, long-lasting response.
that secrete substances (eg. enzyme & sweat)
onto epithelial surfaces and into lumen.
Class of hormone
, can pass through cell membrane
bind to receptor in cytoplasm, form hormone-receptor complex - bind to receptor in nucleus, then bind to DNA as
activate genes, induce new proteins synthesis
polypeptides, glycoproteins, amines
, can’t pass through plasma membrane
2° messenger pathway
“signal transduction”: transmit “signal” across membrane
multi-step “cascade”: activates a series of 2° messengers
activate cellular response
enzyme action, uptake or secretion of molecules
Same hormone can
exert different response
depending on the target cells or
regulate different function
in different animals.
In bird, it stimulates ovalbumin production in reproductive system and proteins synthesis in liver.
Female humans do not respond to estrogen by making ovalbumin.
in human and other vertebrates, it is responsible for metabolic regulation
It triggers metamorphosis in amphibians.
Hormone regulation in insect development
Brain hormone (BH) / prothoracicotropic hormone (PTTH)
from neurosecretory cells in brain trigger
promotes retention of larval characteristic and balances the effect of BH & ecdysone.
Control and feedback
: other hormones activate endocrine glands
: ions level change in blood triggers the release of hormone
"master control center" receives nerve impulses and stimulate
"master gland" to secrete broad range of hormones to regulate other glands.
eg. Thyroid gland - Thyroid-Stimulating Hormone (TSH).
Hormone feedback mechanism
Lactation (Oxytocin & Prolactin)
Labor contractions (Oxytocin, Prostaglandins & Estrogen)
Inhibit further change
Blood calcium (Parathyroid hormone)
Sugar metabolism (insulin & glucagon)
Blood osmolarity (ADH)
Metabolism & growth [TRH (from hypothalamus) triggers the release of TSH (from anterior pituitary), then further stimulates the thyroid to produce thyroxine which is important for metabolism and development.]
unusual hormone level
behavioral, physical or physiological changes
Endocrine gland hyposecretion
Endocrine gland hypersecretion
Tumours (benign or malignant) of endocrine glands
extra thyroxine-a thyroid hormone in the bloodstream
Some of the symptoms are;
Weight loss despite increase in appetite
Increased activity level / Rapid heart rate
Increased urination / Diarrhea
Aggression / Nervousness
Prolonged exposure of cortisol
- cortisol imbalance
Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine