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Lecture 14

HLSC 1F90 Lecture Notes - Lecture 14: Insulin Receptor, Parathyroid Gland, Thyroid


Department
Health Sciences
Course Code
HLSC 1F90
Professor
Dr.Kelli-an Lawrance
Lecture
14

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Topic 14 Introduction to Endocrinology
RESEARCH READING
Detours o the Road to Diagosis of Grave’s Disease Sis et al 
LECTURE READING
Introduction to the Endocrine System (Chapter 7 from Silverthorn Human Physiology 6th Edition)
LECTURE NOTES
Lecturer: E. L. Tsiani
Hormones and Human Body Function
January 19, 2017
Hormones
cell to cell communication molecules
secreted by endocrine glands/cells into the blood
only target cells with receptors for the hormone will respond to the signal
Classical Endocrine Definition:
Chemical signal package in granules or secretory vesicles
Secreted by a cell or a group of cells
Transported by blood
Act on distant target tissues (receptors)
Neurohormones
Chemicals released by neurons into the blood for action at distant targets
Autocrine signals act on same cell that has secreted the hormone
Paracrine signals act on the cell next to the cell that secreted the hormone
What determines whether a cell in our body is a target for the hormone insulin?
A. Nothing. All cells in our body are insulin targets
B. The presence of insulin receptor in the cell*
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Hormone Function
Cellular mechanism of action
o Depends on binding to target cell receptors
o May have different actions depending on the tissue and stage of development
o Controls biochemical and translational and transcriptional events
Rate of enzymatic reactions
Transport of ions or molecules across cell membranes
Gene expression and protein synthesis
Hormone Half-Life
The length of activity
Measure of the time needed to decrease its concentration in the circulation by 50%
Three Classes of Hormones
1. Peptide or Protein Hormones
a. Glucagon, insulin and GH
b. Protein synthesis and exocytosis
c. Water soluble
2. Steroid Hormones
a. Cholesterol-derived
b. Produced in adrenal gland
c. Lipid soluble
d. Testosterone, estrogen, cortisol
3. Amino Acid-Derived or Amine Hormones
a. Catecholamines which are like peptide hormones
b. Thyroid hormones which are like steroid hormones
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Peptide/Protein Hormones
Bind to surface membrane receptors
Cellular response through signal transduction system
Steroid Hormones
Bind to carrier proteins in blood which increases their half-life
Cytoplasmic or nuclear receptors (cytoplasmic receptors give rise to a faster response)
Steroid hormones act primarily on intracellular receptors
Amino Acid-Derived/Amine Hormones
Derived from one of the two amino acids
o Tyrosine
o Tryptophan
Characterized by a ring structure
Insulin (protein hormone) is administered by injection and not in pill form because:
A. Injection will get into target cells faster
B. It is more expensive to produce a pill
C. Oral consumption will digest the protein hormone and never allow the insulin to reach target
cells*
Hormones play an important role in Homeostasis
Homeostasis
Maintenance of static, or constant conditions of the internal environment
Feedback-control mechanisms
Control mechanisms involved in the regulation of body functions to maintain homeostasis
Negative feedback control mechanisms oppose a change by creating a response that is opposite
to the stimulus
o In blood glucose homeostasis the stimulus is an increase in blood glucose levels, the
response is reducing the levels by secreting insulin
o In blood calcium concentration homeostasis, the stimulus is a decrease in calcium blood
levels, the response is an increase in calcium blood levels by secreting parathyroid
hormones (PTH)
Positive feedback control mechanisms accelerate a change
o I ervial streth regulatio durig hild irth, the stiulus is the ay’s head, the
response is cervical stretching by secretion of oxytocin from the pituitary which
increases contraction of the uterus
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