Please enable JavaScript.
Coggle requires JavaScript to display documents.
Hormones and Endocrinology (Hormone regulation in insect development…
Hormones and Endocrinology
Hormones
Definition
Chemical signal secreted into the body fluid
to targeted cells and communicates regulatory messages within the body
Function
A method of communication between one body part to another
Coordinate the organ through action and feedback
Regulates
Metabolism
Growth
Development
Maturation
Reproduction
Signalling
Target tissue respond and resulted in feedback mechanism
Feedback reach gland to either stop or increase production of hormone
Hormones reach target tissue and bind to specific receptor
Blood transfers hormone throughout the body
Gland secrete hormone into extracellular fluid
Hormone produced by endocrine gland
Class
Protein-based hormone
Example
Glycoproteins
Large protein + carbohydrate: FSH, LH
Amines
Modified amino acids: Epinephrine, Melatonin
Polypeptides
Small proteins: Insulin, ADH
Classification
Trigger secondary messenger pathway
:star:
transmit “signal” across membrane
•“signal transduction”
:star:
usually activates a series of 2° messengers
• multi-step “cascade
Activate cellular response
-enzyme action, uptake or secretion of molecules, etc.
Hydrophilic & Not lipid soluble
-Cannot diffuse through membrane
Mechanism
Benefit of secondary messenger system
Lipid-based hormone
Classification:
Bind to receptor proteins in cytoplasm & then this hormone-receptor complex moves into nucleus
Bind to receptor proteins in nucleus & then bind to DNA as transcription factors
Lipid-soluble
Diffuse across membrane & enter cells
Activate genes that result in synthesis of new proteins
Mechanism
Example
Steroids
-Modified cholesterol: sex hormones, aldosterone
Eicosanoids
-Prostaglandins
Endocrine vs Exocrine system
Endocrine
Ductless
Each gland contained specialised cells to synthesize hormone
Blood stream
Hormone
Exocrine
Lumen and surface
Eg. Sweat and enzymes
Ducts
Endocrine Vs Nervous System
Endocrine
•Signal type → chemical (hormone)
•Transfer → blood circulation to whole body
• Action → Slow, Long-lasting response
Nervous
• Signal type → electrical + chemical (nerve impulse + neurotransmitter)
• Transfer → neuron network to target cells
• Action → fast, short-lasting response
Major Vertebrate Hormones
Homology in hormones
Hormone regulation in insect development
JH balance the effect of BH and ecdysone
Molting process
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
In larval molt and pupal molt, BH and ecdysone promote molting process by inducing development of adult characteristic
Juvenile hormone (JH) is secreted by a pair of small gland (corpora allata) promotes retention of larval characteristic
Ecdysone induces molting in moth
BH stimulates protoracic gland to secretes ecdysone
Neurosecretory cells in the brain produce brain hormone (BH)
Control & Feedback
Endocrine & nervous system 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
Pituitary glands & its network
Heural stimulation
Nerve impulses stimulate hormone release
Most are under control of the sympathetic nervous system
Hormone feedback mechanism
Positive feedback
Stimulus triggers control mechanism that amplifies effect : eg; lactation, labor contractions
Milk production
Frog metamorphosis
Labor contraction
Negative feedback
Stimulus triggers control mechanism that inhibits further change : eg; body temperature, sugar metabolism
Blood glucose
Blood osmolarity (If amount of dissolved material in blood too high, need to dilute blood)
Blood calcium
Metabolism & growth
Anterior pituitary
TSH (Thyroid Stimulating Hormone)
Thyroid
Produce thyroxine hormones
For metabloism & development
Bone growth
Mental development
Metabolic use of energy
Blood pressure & heart rate
Muscle tone
DIgestion
Reproduction
Hypothalamus
TRH (TSH - Releasing Hormone)
Humoral stimulation
Changing blood levels of certain ions stimulate hormone release
Hormonal stimulation
Endocrine glands are activated by other hormones
Hormone Disorder
Caused by endocrine disease or drugs interaction and if left untreated, can result in serious medical condition
Symptoms includes behavioral, physical or physiological changes
Unusual level of hormones in bloodstream can leads to hormone disorder
Endocrine DIsease
Endocrine gland hypersecretion (leading to hormone excess)
Hyperthyrodism
Common glandular disorder in cats
Frequently caused by excessive concentration thyroxine
Symptoms
Weight loss despite increase in appetite
Increased activity level / Rapid heart rate
Increased urination / Diarrhea
Aggression / Nervousness
Hypercortisolism
Prolonged exposure of cortisol
The Cushing’s syndrome
Tumours (benign or malignant) of endocrine glands
Goiter
Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine
Endocrine gland hyposecretion (leading to hormone deficiency)
