Anatomical Basis Of Homeostasis: Overview Of Hormonal Secretion Flashcards
Charcteristics of their nervous system
Always working
Discrete, localised
Rapid control
Interact to coordinate organ and tissue activity in response to physiological needs
Regulate activities of body, maintain homeostasis
Characteristics of the endocrine system
Functions intermittently
Exert diffuse control
Often prolonged control
Interact to coordinate organ and tissue activity in response to physiological needs
Regulate activities of body, maintain homeostasis
How does the endocrine system function
Specific stimulus Specific endocrine cell activated Hormone released into blood/ICS Target tissue responds Reduces incoming stimulus Negative feedback loop
Functions of hormones
Development
-Proliferation, growth, differentiation, organogenesis
Metabolism
-Carbohydrate, energy storage, metabolic rate, temp
Reproduction
-Sexual maturation and behaviour, pregnancy maintenance, lactation
Fluid balance
-Water balance, salt levels, blood volume, pressure
Name the endocrine glands
Pituitary (anterior, posterior) Thyroid Parathyroid Islets of Langerhans Adrenals Gonads
What hormone is released from the pineal gland
Melatonin
What hormone is released from the hypothalamus
GnRH CRH GHRH TRH Somatostatin Dopamine
What hormones are released from the pituitary
FSH LH GH TSH ACTH Prolactin Oxytocin ADH
What hormones are released from the thyroid
T4
T3
Calcitonin
What hormones are released from the parathyroid
Parathyroid hormone
What hormones are released from the thymus
Thymosin
What hormones are released from the adrenals
Cortisol Aldosterone Androgens Adrenaline Noradrenaline
What hormones are released from the pancreas
Insulin
Glucagon
Somatostatin
What hormones are released from the gonads
Oestrogen
Testosterone
Progesterone
What tissues also secrete hormones
Kidney Heart Vascular endothelium Gut cells Adipocytes Placenta Thymus
What hormones are released from the kidney
Erythropoietin, increase RBC production
What hormones are released from the heart
Atrial natriuretic peptide, increase Na+ kidney excretion, decrease BP
What hormones are released from the vascular endothelium
Von Willebrand factor, aids clotting
What hormones are released from the gut cells
Gastric
Secretin
What hormones are released from the adipocytes
Leptin, suppresses appetite
What hormones are secreted from the placenta
Lactogen
hCG
How are hormones delivered
Endocrine, from endocrine cell=>blood
Neuroendocrine, from nerve cell=>blood
Paracrine, hormone released locally, acts on nearby cells
Autocrine, hormone released locally, acts on itself
Describe neuroendocrine secretion from the neurohypophysis
Secretory neurones have specialised nerve endings that store hormones in vesicles (Herring bodies)
AP generation causes hormones to be released into capillaries from the axo terminals
Types of hormones
Proteins/peptides
Steroids
Amines
Why is the type of hormone important
Biochemical structure dictates
- Mechanism of action at target cell
- How hormone is carried in blood
- Circulating half life
Examples of small peptides
ADH
TRH
Examples of long chain polypeptides
GH
Insulin
Examples of glycoproteins
LH
How are protein and peptide hormones synthesised
By DNA transcription, translation mainly as preprohormones
Preprohormones => cleaved by proteolysis enzymes => prohormones
Prohormones stored in secretory vesicles
Release of active hormone by executors is when cytosol is [Ca2+] is high
Diffuses into leaky capillaries, circulate unbound, short half life
All hormones of hypothalamus, pituitary, parathyroid, GI and pancreas
Synthesis of steroid hormones
All structures based on 3 6C rings and 1 5C ring, derived from cholesterol
Synthesised in mitochondria and SER
Not stored in gland, hormones release dependent on synthesis rate
Diffuses across plasma membrane
Circulate in blood, albumin bound, long half life
Produced by adrenals, gonads, placenta
Properties of amine hormones derived from tyrosine in the thyroid
Lipid soluble, cross cell membrane
Circulate protein bound, long half life
Stored in thyroid bound to thyroglobulin
Properties of catecholamines, derived from tyrosine
Water soluble, don’t cross cell membranes
Circulate unbound in blood, short half lives
Stored intracellularly in secretory granules
What are eicosanoids
How do they act
What are they derived from
Local chemical messengers that exert wide variety of effects in many different organs and tissues
Autocrine, paracrine
Derived from arachidonic acid
Effects of eicosanoids such as prostaglandins
Immune system, promote inflammatory process
Reproductive system, play role in ovulation
Digestive system, inhibit gastric secretion
Generally, what do kind of hormones come from neurosecretory cells
Proteins
Catecholamines
Generally, what kind of hormone comes from epithelial tissues
Steroid
Thyroid hormones
What controls the plasma concentration of a hormone in the blood
Depends on rate of secretion and rate of removal
How are hormones removed
By the liver and kidneys
Excrete and metabolise hormones
Mechanism of steroid and thyroid hormone action
Intracellular cytoplasm/nucleus
Alter gene transcription
Mechanism of peptides, proteins, glycoproteins, catecholamines
Cell surface, plasma membrane
Secondary messengers to change enzyme activity
Describe the process by which steroid hormones act
Steroid diffuses through cell membrane, binds to cytoplasmic or nuclear receptor
Receptor hormone complex translocates to nucleus
Dimerisation occurs on hormone response element (HRE) of DNA
DNA binding stimulates transcription of specific genes
Describe the process by which lipid insoluble hormones act
Hormone binding to extracellular domain changes receptor conformation
Causes changes to intracellular domain in cell=>signalling cascades leading to cells repose
Types of receptors for lipid insoluble hormones
Monomeric receptor, EGF
Multimeric receptor, insulin
Receptors with 7 spanning domains, B adrenergic
How is hormone secretion controlled, describe the types of stimulus
Changes in plasma conc of mineral ions
Changes in plasma conc of organic nutrients
Neurotransmitters released from neurones contacting endocrine cells
Upstream hormone/paracrine agent acting on endocrine cell
Describe the structure of the pituitary
Structure of neurohypophysis
Median eminence
Infundibular process, both of these make up the infundibulum
Par nervosa
Structure of adenohypophysis
Pars tuberalis
Pars intermedia
Pars distalis
Describe the the embryonic development of the pituitary
Downgrowth of the floor of the diencephalon (hypothalamus)
Upgrowth of the roof of the mouth to form Rathke’s pouch
Rathke’s pouch separates from mouth and forms the adenohypophysis
Downgrowth of hypothalamus forms neurohypophysis
Both pituitaries surrounded by sella turcica
Describe the process by which the neurohypophysis functions
Specific neural stimuli causes ADH/oxytocin synthesis in cell bodies
Hormones travel down axons from either the supraoptic nucleus/paraventricular nucleus
Stored in nerve terminals
Released into pituitary vein
Which nucleus is oxytocin released from
Paraventricular
What nucleus is ADH released from
Supraoptic
Paraventricular
Describe how the adenohypophysis functions
Specific neural stimuli causes hypothalamic hormone synthesis and release
Released at the median eminence from the nuclei
Travel down portal blood vessels
Control release of anterior pituitary hormones
Describe the pituitary portal blood system
Blood that reaches the adenohypophysis passes via the capillary loops through long/short hypophyseal portal vessels
Long hypophyseal portal vessel connects from superior hypophyseal artery to capillary loops in adenohypophysis
Short hypophyseal portal vessels connect capillaries in the adenohypophysis and neurohypophysis
Superior hypophyseal artery supplies median eminence and stalk
Inferior hypophyseal artery supplies posterior lobe directly and anterior lob via short portal vessels
Both lobes drain into venous sinuses
Adenohypophysis function
Cell types here
Gonadotroph cells Corticotroph cells Somatotroph cells Lactotroph cells Thyrotroph cells, all these cells release 6 fully establishes hormones
TSH, ACTH, LH, FSH are trophic to other endocrine glands
GH stimulates stomatomedins, trophic
Prolactin doesn’t stimulate production/secretion
Control of adenohypophysis
Hypothalamic hypophysiotrophic hormones
Feedback by target hormones
Describe the use of hypophysiotrophic hormones
Released into pituitary portal system from nerve terminals in median eminence of hypothalamus
Stimulate release of specific hormones from anterior pituitary
Not present at detectable levels in wider circulation
Trophic secreting cells in anterior pituitary
Describe a short loop feedback system
Negative feedback of the hormone released from the pituitary on the hypothalamus
Decrease amount of hypophysiotrophic hormone released
Describe a long loop feedback system
Target gland releases a hormone that acts on the pituitary/or the hypothalamus
Decrease the amount of hypophysiotrophic hormone/hormone released
Describe an ultra short feedback loop system
Hormone released from target gland acts in an autocrine manner
Decreases amount of hormone released from the target hormone
Action of dopamine on the lactotroph cells
Inhibits the release of prolactin
Inhibits effect on mammary glands
Action of somatostatin on somatotroph cells
Inhibits the release of GH
Inhibits growth
