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Lecture 14

HLSC 1F90 Lecture Notes - Lecture 14: Pituitary Gland, Anterior Pituitary, Peptide Hormone


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

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Topic 14: Introduction to Endocrinology Dr. E. L. Tsiani ltsiani@brocku.ca
Hormones and Human Body Function
Hormones
Are molecules that produced by endocrine cells and are found in different regions in our
body.
Cell to cell communication molecules
Classical Endocrine definition
Chemical signals packaged in granules or secretory vesicles
Secreted by a cell or group cells
Transported by blood
Act on distant target tissues (receptor)
Active physiological response at low concentrations
Endocrine glands or cells into the blood secrete hormones. Only target cells with receptor for the
hormones and the signal.
Neurohormones are chemicals released by neurons into the blood for action at distant targets.
Clicker Q: what determines whether a cell in our body is a target for the hormone insulin?
A: The presence of the insulin receptors in the cells.
Hormones: Functions
Half-life: indicates the length of activity
Typically as a measure of the time needed to decrease its concentration in the circulation
by 50 %
Hormones: classification by chemical class
Peptide hormone synthesis and processing
Hormones that are peptide proteins are destined to get out of the endocrine cells
so they are exported
Preprohormone: large, inactive precursor
Prohormone: smaller, inactive
Peptide/protein hormones: bind surface membrane receptors
Cellular response through signal transduction.
They act through plasma membrane receptors
Water soluble
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Steroids
Cholesterol-derived
Bind carrier proteins in blood: lengthens their half-life
Cytoplasmic or nuclear receptors
Adrenal gland (cortex) can produce hormones that are steroids
Primarily act on intracellular receptors
Amine- amino acid-derived
Most amine hormones come from the amino acid tyrosine
Clicker Q: Insulin (protein hormones) is administered by injection and not in a pill form bc:
A: C
Hormones play an important in homeostasis
Control mechanisms in homeostasis are:
Negative feedback control mechanism
Positive feedback control mechanism
Negative:
A rise in blood glucose is directly stimulates insulin release from the pancreatic beta cells: this is
simple endocrine reflex
Parathyroid cells in 4 small parathyroid glands next the thyroid, monitor blood calcium
concentration vis a cell surface calcium ion receptor.
Low blood calcium levels allows the parathyroid to release calcium receptors.
Positive:
Acceltrates a change: positive feedback during childbirth
Cervical stretch caused by the baby’s head causes release of oxytocin by the pituitary.
Endocrine Reflex Pathways
The Pituitary Gland:
Also called hypothesis (hypothalamus)
The anterior pituitary is a true endocrine gland that secretes six classic hormones.
Neurohormones control release of the anterior pituitary.
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