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LU9: HORMONES AND ENDOCRINOLOGY (Hormone Signaling (Blood transfers…
LU9: HORMONES AND ENDOCRINOLOGY
Hormones
: A chemical signal that secreted into body fluid (often blood), & communicate regulatory messages within the body.
Functions:
Coordinate the organs through action and feedback
Regulates;
metabolism, growth, development, maturation, reproduction
A method of communication between one body part to another
Hormone Signaling
Blood transfers hormones
to whole body.
Hormone reaches target tissue and bind to specific receptor.
Gland secrete hormones into extracellular fluid.
Target tissue responds and resulted in
feedback mechanism
.
Hormones produced by
endocrine gland
.
Feedback reach gland to either stop or increase production of hormones.
Classes of Hormones
Protein-based hormones
Glycoproteins
(large proteins + carbohydrate: eg., FSH, LH)
Amines
(modified amino acids: eg., epinephrine, melatonin)
Polypeptides
(small proteins: eg, insulin, ADH)
Hydrophilic & not lipid soluble
(can't diffuse across membrane)
Trigger secondary (2°) messenger pathway
(signal transduction & multi-step "cascade")
Activate cellular response
(enzyme action, uptake or secretion of molecules, etc.)
Lipid-based hormones
Steroids
(modified cholesterol: eg., sex hormones, aldosterone)
Eicosanoids
(prostaglandins)
Lipid -soluble
(diffuse across membrane & enter cells)
Bind to receptor proteins (cytoplasm) & then hormone-receptor complexes moves into nucleus.
Bind to receptor proteins (nucleus) & then bind to DNA (as transcription factors)
Activate genes
(result in synthesis of new proteins)
Endocrine System
: System of ductless glands (Each gland contain specialized cells that synthesizes Hormone)
Endocrine vs Exocrine
Endocrine
: Ductless, Blood stream, & Hormone
Exocrine
: Ducts, Lumen and surfaces, and Eg: enzyme & sweat
Endocrine vs Nervous Signaling
Endocrine system
Transfer:
blood circulation to whole body
Action:
slow, long-lasting response
Signal type:
chemical (hormone)
Nervous Signaling
Transfer:
neuron network to target cells
Action:
fast, short-lasting response
Signal type:
electrical + chemical
(nervous impulse + neurotransmitter)
Hormones Regulation in Insect
Ecdysone
induces molting in moth.
Juvenile hormone (JH)
: Promotes retention of larval characteristic (secreted by a pair of small gland/corpora allata)
BH stimulates protoracic gland
(produced by Neurosecretory) to secrete ecdysone.
JH balances the effect of BH and ecdysone
Control & Feedback
Humoral stimulation
: Changing blood levels of certain ions stimulate hormone release.
Heural stimulation
: Nerve impulses stimulate hormone release (Most are under control of the sympathetic nervous system)
Hormonal stimulation
: Endocrine glands are activated by other hormones
Endocrine & Nervous Signaling links
Hypothalamus
("master control center")
Nervous system (receives information from nerves around body about internal conditions)
Regulates release of hormones from pituitary
Pituitary gland
("master gland")
Endocrine system (secretes broad range of hormones regulating other glands)
Hormones Feedback Mechanism
Negative Feedback
Stimulus triggers control mechanism that inhibits further (body temperature, sugar metabolism)
Eg:
blood glucose, blood osmolarity, blood calcium, metabolism & growth
Positive Feedback
Stimulus triggers control mechanism that amplifies effect (lactation, labor contractions)
Eg:
milk productions, frog metamorphosis
Hormones Disorder
Caused by endocrine disease/drugs interaction and can result in serious medical condition (if left untreated)
Symptoms include behavioral, physical or physiological changes.
Unusual level of hormones in bloodstream can leads to hormone disorder.
Goiter
: Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine
Endocrine Disease
Endocrine gland hypersecretion
(leading to hormone excess)
Endocrine gland hyposecretion
(leading to hormone deficiency)
Tumours
(benign or malignant)
of endocrine glands
Hormonal Imbalance
Hyperthyrodism
Caused by excessive concentration thyroxine-a thyroid hormone in the bloodstream
Symptoms
: Weight loss despite increase in appetite, increased activity level, rapid heart rate, increased urination, diarrhea, aggression, nervousness
Hyperthyroidism
(common glandular disorder in cats)
Hypercortisolism
Prolonged exposure of cortisol leads to hypercortisolism
The
Cushing's syndrome
shows collection of external sign or symptom related to cortisol imbalance