Physiology 3120 Lecture Notes - Lecture 1: Ghrelin, Corepressor, Dihydrotestosterone
9 May 2018
School
Department
Course
Professor
Physiology 3120
Dr. Hardy
Introduction to Endrocrinology
Definitions
- Endocrine system:
o Tissues and cells capable of secreting and responding to hormones (signalling molecule)
o Communication system
o The 2 components communicate via chemical messenger called hormones
▪ Tissue/organ A will release a hormone – this hormone will travel through the
blood and target tissue/organ B to elicit a response/change in physiology to
tissue B
- Neural:
o Functions mediated by electrochemical conduction along nerves
o Nervous system allows for rapid communication bw the brain and other components of
the nervous system
- Endocrine:
o Functions are mediated by chemical messengers called hormones
- Hormone:
o Chemical substance, formed in one organ or part of the body and carried in the blood to
another organ or part
o Depending on the specificity of their effects, hormones can alter the functional activity
of just ONE organ or of various numbers of them (GnRH vs T3)
▪ GnRH produces and targets the pituitary whereas T3 is produced and targets
several organs of the body to target for ex: basal metabolic rate
▪ So one hormone can influence one organ or many organs
o Hormones are:
▪ Regulators of physiological events
▪ Effective in minute quantities (pg or ng or mg)
▪ Synthesized by a collection of cells/endocrine glands
▪ Greek= hormone = to rouse or set in motion
Not all hormones are the same
- Endocrine:
o chemical mediators produced in one part of the body which act on a
distant part.
o Remote control
- paracrine:
o chemical mediators produced in one cell that acts on a neighboring cell.
o Neighbourhood watch
- autocrine:
o chemical mediator produced in one cell and acts on that same cell.
o Self control
Nervous VS Endocrine System
- Physical form of information transfer
o Nervous system relies on action potentials to fire those nerve to elicit a response
o endocrine system which responds to chemicals (specifically hormones)
- Speed of information transfer
o Nervous system takes fractions of seconds to work
o hormones (depending on their properties) take minutes, hours, days
find more resources at oneclass.com
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- Mechanism of gradation (how do you stimulate the response of both of these communication
systems?)
o Nervous system: increase the firing (frequency) of an AP
o Endocrine system: amplitude modulation→receptor upon activation can activate
downstream effects
- Mechanism to achieve specificity
o Nervous system: due to the wiring (the actual nerves themselves and where they go to
o Endocrine system: how specific the receptors is to receive the hormone and elicit the
downstream effect
Hormone Types
- peptide/polypeptide
o Small monomers
▪ Ex: TRH (3 a.a)
o Large multimeric proteins
▪ Ex: TSH, FSH, LH (200+ a.a)
o Water soluble
▪ Can easily dissolve in the blood to travel from tissue A to tissue B
- steroid
o Derived from cholesterol metabolism
o 4 hydrocarbon rings with various side chains
o Lipid soluble (requires binding protein in serum)
▪ Aka water INsolubule
▪ These hormones need carrier proteins (binding serum proteins) to travel from
tissue A to tissue B
▪ eg. testosterone, estrogen, vitamin D
- amino acid derivatives
o derived from amino acids
o ex:. epinephrine,
o ex: thyroxine (T4)
▪ derived from tyrosine
▪ large aromatic structures
o difficulty dissolving in water (lipid soluble)
Human Endocrine System
- every tissue in the body produces some type of hormone
- The gut secretes its own series of hormones to regulate food intake and
digestion
o Ex: CCK, ghrelin, gastrin, secretin, NPY etc
- The heart secretes ANP, an important factor in regulating vascular tone
and volume
- The kidneys secrete EPO which increases erythrocyte formation
- The liver secretes angiotensinogen (angiotensin precursor), IGF-I and
thrombopoietin ↑ platelets
- Fat produces many adipokines e.g. leptin
- Most cells produce locally-acting growth factors and cytokines
find more resources at oneclass.com
find more resources at oneclass.com
Regulation of Endocrine Secretion I: Negative Feedback
1. Between 2 hormones:
o Organ A produces hormone A, this circulates in the blood, acts on tissue B receptor to
make tissue B produce hormone B
o When the levels of hormone B get too high in circulation, this has a –ive feedback effect
to shutdown the production of hormone A from tissue A
o E.g TSH and T3
▪ TSH is produced in the ant pituitary and acts on the thyroid to produce T3
▪ When levels of T3 are too hight, it shuts down production of TSH
2. Between a hormone and a metabolite:
o E.g PTH and Ca2+
▪ Parathyroid gland produces PTH which acts on bone
▪ Bone will increase intracellular Ca2+ this is not a hormone, its a metabolite
▪ When Ca2+ levels get too high in circulation, this shuts down the production of
PTH in parathyroid gland due to Ca2+ sensing receptors which detect high
levels of Ca2+
3. Between antagonistic pairs of hormones
o E.g insulin, glucose and glucagon
▪ We want to maintain our blood glucose at 5mmol
▪ This is regulated by insulin and glucagon
▪ When blood glucose levels get too high, insulin (produced by the beta cells of
the pancreas) will act to lower blood glucose
▪ When blood glucose levels get too high, glucagon (produced by the alpha cells
of the pancreas ) will act to raise blood glucose
▪ SO they do opposite things but end up working together to keep blood glucose
levels at a particular homeostatic level
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Neural: functions mediated by electrochemical conduction along nerves, nervous system allows for rapid communication bw the brain and other components of. Endocrine: chemical mediators produced in one part of the body which act on a distant part. (cid:523)(cid:498)remote control(cid:499)(cid:524) Paracrine: chemical mediators produced in one cell that acts on a neighboring cell. (cid:523)(cid:498)neighbourhood watch(cid:499)(cid:524) autocrine, chemical mediator produced in one cell and acts on that same cell. (cid:523)(cid:498)self control(cid:499)(cid:524) Physical form of information transfer: nervous system relies on action potentials to fire those nerve to elicit a response, endocrine system which responds to chemicals (specifically hormones) Speed of information transfer: nervous system takes fractions of seconds to work, hormones (depending on their properties) take minutes, hours, days. Mechanism of gradation (how do you stimulate the response of both of these communication systems?: nervous system: increase the firing (frequency) of an ap, endocrine system: amplitude modulation receptor upon activation can activate downstream effects.
