LU9: HORMONE AND ENDOCRINOLOGY (hormone regulation in insect development…
LU9: HORMONE AND ENDOCRINOLOGY
definition of hormones
A chemical signal secreted into body fluid (often blood), and communicates regulatory messages within the body
function of hormones
A method of communication between one body part to another
Coordinate the organs through action and feedback
class of hormones
hydrophilic & not lipid soluble
trigger secondary (2°) messenger pathway
activate cellular response
bind to receptor proteins in cytoplasm
bind to receptor proteins in nucleus & then bind to DNA as transcription factors
activate genes that result in synthesis of new proteins
A system of ductless glands
Each gland contain specialized cells that synthesizes Hormone
endocrine vs exocrine
Eg: enzyme & sweat
lumen ans surfaces
endocrine vs nervous signalling
Signal type → chemical (hormone)
Action → slow, long-lasting response
Transfer → blood circulation to whole body
Transfer → neuron network to target cells
Action → fast, short-lasting response
Signal type → electrical + chemical
control and feedback
Changing blood levels of certain ions stimulate hormone release
Nerve impulses stimulate hormone release
Most are under control of the sympathetic nervous system
Endocrine glands are activated by other hormones
hormone feedback mechanisms
stimulus triggers control mechanism that amplifies effect
stimulus triggers control mechanism that inhibits further change
metabolisms and growth
hormone regulation in insect development
Ecdysone induces molting in moth.
The third hormone – juvenile hormone (JH) - secreted by a pair of small gland (corpora allata) promotes retention of larval characteristic.
BH stimulates protoracic gland to secretes ecdysone.
JH balance the effect of BH and ecdysone.
Neurosecretory cells in the brain produce brain hormone (BH).
In larval molt and pupal molt, BH and ecdysone promote molting process by inducing development of adult characteristic.
But relatively high concentration of JH promote retention of juvenile characteristics and thus supress metamorphosis.
In adult molt, low level of JH allows larva to develop into moth when induced by BH and ecdysone.
Unusual level of hormones in bloodstream can leads to hormone disorder.
It can be caused by endocrine disease or drugs interaction and if left untreated, can result in serious medical condition.
Symptoms includes behavioral, physical or physiological changes.
Endocrine gland hypersecretion (leading to hormone excess)
Tumours (benign or malignant) of endocrine glands
Endocrine gland hyposecretion (leading to hormone deficiency)
Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine
common glandular disorder in cats.
Frequently caused by excessive concentration 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 leads to hypercortisolism.
The Cushing’s syndrome shows collections of external sign or symptom related to cortisol imbalance.