Lecture: Introduction to endocrine system Flashcards
Hypothalamus
contains
ADH, Oxytocin
Pineal
melatonin
Parathyroid
PTH
Pituitary
Anterior
ACTH, TSH, GH, PRL
FSH, LH, MSH,
Pituitary
posterior
ADH, Oxytocin
Thyroid
Thyroid
Thyroxine (T4)
Triodothyronine (T3)
Calcitonin
Thymus
Thymosins
Gonads
androgens (male)
Oestrogens, progesterone (female)
Adrenals- medulla
adrenaline, noradrenaline
endocrine glands
are ductless
secrete hormones into circulation
Adrenals
-cortex
Cortisol, corticosterone,
cortisone, aldosterone, androgens
Pancreas
Insulin, glucagon
Digestive tract
. gastrin, CCK, secretin
Kidney
renin, erythropoietin
Heart
Atrial natruiretic peptide
Parathyroid
PTH
cell to cell signaling
Intracrine
Autocrine
Paracrine
Endocrine
Neuroendocrine
Intracrine function
Intracrine signaling involves the production and action of signaling molecules within the same cell, without their release into the extracellular space or bloodstream.
Autocrine function
Autocrine signaling occurs when a cell produces signaling molecules that bind to receptors on its own surface, influencing its own behavior or function.
paracrine function
Paracrine signaling refers to the mode of cell communication where signaling molecules are secreted by one cell and act on neighboring cells in the local microenvironment.
endocrine cell function
Endocrine signaling involves the release of hormones into the bloodstream by specialized glands, which then travel to distant target cells to regulate various physiological processes.
neuroendocrine function
Neuroendocrine signaling involves the release of hormones from neurons into the bloodstream, regulating physiological processes and acting as a bridge between the nervous and endocrine systems.
Endocrine functions
Endocrine organs release hormones that are important in four broad areas:
Reproduction
Growth and development
Maintenance of internal environment
Regulation of energy
Hormones
Produced by glands and released directly into circulation
Present in low concentrations (10-7 - 10-12 M)
Bind to specific, high affinity recognition sites or receptors on/in target cells
Single hormone may have different tissue-specific effects
Single function may be regulated by different hormones
Hormones Structures and Synthesis
Three major chemical classes of hormones
Amino acids/Amines
Peptides and proteins
Steroids
Amine hormones
Catecholamines derived from tyrosine
adrenaline, noradrenaline
Thyroid Hormones also derived from tyrosine
thyroxine, triiodothyronine
(Indoleamines derived from tryptophan
Melatonin)
c…… derived from tyrosine
Catecholamines derived from tyrosine
adrenaline, noradrenaline
t…….. h…… also derived from tyrosine
Thyroid Hormones also derived from tyrosine
thyroxine, triiodothyronine
in…… derived from trypotophan
Indoleamines derived from tryptophan
Melatonin)
adrenal catecholamine synthesis
tyrosine- tyrosine hydroxylase- L-dopa- Dopa decarboxylase- Dopamine- (Dopamine - beta - hydroxylase)- noradrenaline- phenylethanolamine N-methyl transferase - Adrenaline
to make a thyroid hormone you need
an iodine molecule
tyrosine + 1
mono-iodotyrosine to di-iodotyrosine
(2+ tyrosine) + (2+ tyrosine)
DIT (di-iodotyrosine) x 2 = thyroxine T4
(1 + tyrosine)+ 2+ tyrosine
DIT + MIT = triiodothyronine
steroids
The structure common to all steroids is called a “steroid nucleus” or “steroid backbone.” It consists of three cyclohexane rings (designated as rings A, B, and C) and one cyclopentane ring (designated as ring D), fused together in a specific arrangement. This structure serves as the foundation for the diverse array of steroid hormones found in living organisms.
Steroid hormone synthesis is the process by which cells and glands in the body produce steroid hormones from cholesterol, involving multiple enzymatic reactions in various organs such as the adrenal glands, gonads, and placenta.
example
adrenal hormones
sex hormones
vitamin D ( calcitriol)
Peptide & protein hormones
Peptides
Short amino acid chains e.g.
ADH (9 AA)
Oxytocin (9 AA)
Polypeptides e.g.
Insulin (135 AA)
Prolactin (198 AA)
Proteins
Thyroid stimulating hormone
Follicle stimulating hormone
Growth hormone
Peptide & protein hormones: synthesis
Release by exocytosis as
prohormone or hormone into blood stream
Hormone Receptors
The ability of a cell to respond to a hormone depends upon the presence of receptors for that hormone on or in the target cell.
The number of receptors for a hormone can increase (up-regulation) or decrease (down-regulation).
May be
Cell surface receptors
Intracellular receptors
Endocrine communication
Messages disseminated from glands to effector via circulation
Relatively slow transfer of information
Can be long lasting
All cells contacted, specificity conferred by receptors
slow maintenance of cellular homeostasis
Positive and negative feedback loops
long-loop - neuro endocrine pathway
short-loop contractions in giving birth positive feedback
Endocrine disorders
Hypo-secretion
e.g. type I diabetes
Hyper-secretion
e.g. pancreatic endocrine tumour
Hypo-responsive
e.g. insulin resistant type II diabetes
Hyper-responsive
TSH receptor constitutive activation => hyperthyroidism
