Please enable JavaScript.
Coggle requires JavaScript to display documents.
LU9 Hormone & Endocrinology (Control and feedback (Hormone feedback…
LU9 Hormone & Endocrinology
Functions of hormone
Communicate
one body part with another parts.
Coordinate body organs through
action
and
feedback
Regulates
a}.
Metabolism
b}.
Growth
c}.
Development
d}.
Maturation
e}.
Reproduction
Definition of Hormone
A
chemical signal
that secreted into body fluid (blood) communicates regulatory messages within the body and only specific receptors on target cells will respond to that hormone.
Hormone signaling
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
Endocrine System
Endocrine gland
is
ductless
.
chemical hormone produced by specialized cells present in each gland, then enter bloodstream to whole body.
slow, long-lasting response.
versus
Exocrine system
Exocrine gland
has
ducts
that secrete substances (eg. enzyme & sweat)
onto epithelial surfaces and into lumen.
Class of hormone
Lipid-based hormones
steroids, eicosanoids
Lipid-solublle
, can pass through cell membrane
bind to receptor in cytoplasm, form hormone-receptor complex - bind to receptor in nucleus, then bind to DNA as
transcription factors
activate genes, induce new proteins synthesis
Protein-based hormones
polypeptides, glycoproteins, amines
Water-soluble
, can’t pass through plasma membrane
trigger
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
Hormone response
Same hormone can
exert different response
depending on the target cells or
regulate different function
in different animals.
eg. Estrogen:
In bird, it stimulates ovalbumin production in reproductive system and proteins synthesis in liver.
Female humans do not respond to estrogen by making ovalbumin.
Thyroxine:
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
prothoracic gland
to scretes
ecdysone
which induces
molting
in moth.
Juvenile hormone
from
corpora allata
promotes retention of larval characteristic and balances the effect of BH & ecdysone.
Control and feedback
Hormonal stimulation
: other hormones activate endocrine glands
Humoral stimulation
: ions level change in blood triggers the release of hormone
Neutral stimulation
:
Hypothalamus
"master control center" receives nerve impulses and stimulate
pituitary gland
"master gland" to secrete broad range of hormones to regulate other glands.
eg. Thyroid gland - Thyroid-Stimulating Hormone (TSH).
Hormone feedback mechanism
Positive feedback
Amplify effect
Lactation (Oxytocin & Prolactin)
Labor contractions (Oxytocin, Prostaglandins & Estrogen)
Frog metamorphosis
Negative feedback
Inhibit further change
Body temp.
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.]
Hormone disorder
unusual hormone level
behavioral, physical or physiological changes
Endocrine disease
Endocrine gland hyposecretion
Endocrine gland hypersecretion
Tumours (benign or malignant) of endocrine glands
Hyperthyrodism
in cat
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
Hypercortisolism
Prolonged exposure of cortisol
Cushing’s syndrome
- cortisol imbalance
Goiter
Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine
