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Lecture 5

PSYC 342 Lecture Notes - Lecture 5: Secretion, Semipermeable Membrane, Exocytosis

Course Code
PSYC 342
Jens C Pruessner

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PSYC 342 Lecture 5 - Jan. 24
The endocrine systems consists mostly of glands in the body which secrete specific hormones that
have a variety of effects throughout the body
These glands are mostly controlled by hormones from the Pituitary (certain glands are not con-
trolled by the Pituitary)
The Pituitary hormones are mostly controlled by hormones from the Hypothalamus
Differential Hormonal Action:
Two principal ways in which hormones exert their effects on behaviour:
Organizational Hormone Action:
Pre- and early postnatal development
Hormones ‘sculpt’ neural and behavioural systems
Permanent and irreversible
Can only occur during critical development periods
Lead to permanent structural and/or physiological changes
Asymmetric with regards to the sexes
Activational Hormone Action:
Later in development
Not permanent - only displayed when hormone is present
No critical development periods
More subtle changes
Example for Organizational Effect: Finger-length Ratio
Ratio of Index Finger (2) to Ring Finger (4)
Three possibilities 2 < 4, 2 = 4, 2 > 4
Determined during weeks 13 to 14 during gestation
Differences Between the Nervous System and the Endocrine System:
Nervous system use electricity (chemical) whereas endocrine uses hormones
Speed of nervous system is much faster than endocrine system
Hormones can attach to any part of the body through the bloodstream but to activate a specific re-
action, you must propel a specific nerve
Timing and duration of activation (hormone effects last longer)

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Nervous system acts on an on/off system based on action potential threshold, but even a small
amount of hormones can affect the body
Similarities Between the Nervous System and the Endocrine System:
They both have effects on behaviour
They both act through receptors (neurotransmitters and cell receptors)
Mechanism of Hormone Action: Mediated
Receptor action on outside membrane of cell
Induce change in cell through second messenger
Changes cell metabolism and gene expression
Is true for all polypeptide hormones, monoamines, prostaglandins
Mechanisms of Hormone Action: Direct
Hormone enters the cell (diffuse through cell membrane)
Intracellular receptors, form H-R (Hormone Receptor) complex
Penetrating the cell nucleus
Induce gene expression through messenger RNA
Protein synthesis at the endoplasmatic reticulum
Thyroid and steroid hormones (pass through cell membrane because of size)
Receptor Up-and-Down Regulation:
Too much hormone - down regulation of receptor (decrease sensitivity to detect hormone to return
back to normal)
Too little hormone - up regulation (increase sensitivity to detect hormone to return to normal)
No hormone - marked decline of receptors
Types of Hormones:
Vertebrate hormones fall into four chemical classes:
Amine-derived hormones are derivatives of the amino acids tyrosine and tryptophan
Peptide hormones consist of chains of amino acids. Examples of small peptide hormones are
TRH and vasopressin. Peptides composed of hundreds of amino acids are referred to as pro-
teins. Examples of protein hormones include insulin and growth hormone
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