Hormones or Psychoneuroendocrinology
Most of the behaviours are influenced by hormones.
Sexual behaviour is one kind of motivated behaviour.
- Motivated behaviour: they do not have to engage in it in order to survive. Driving force
needed to engage a task or a specific activity. It is a behaviour in which an animal will
work for or will try to access in order to engage in a behaviour.
Hormones act through the brain enhancing that acting force. Behaviour itself will initiate the
release of hormones.
- Androgen: important for male sexual behaviour. There is much more androgen in males
than in females. In human females, androgen is very important for sexual levity. An
animal that engages in sexual behaviour, undergoes an increase in hormones. Hair
growth in men are a very good demonstration of the presence of androgens.
Melatonin: is released in the pineal gland. Pineal gland: was considered the seed of the soul.
Pituitary gland: located below the hypothalamus. Releases the master hormones needed for the
regulation of other hormones.
Adrenal cortex: releases the stress hormones.
Pancreas: releases insulin, glucagon, and somatostatin.
Testosterone, androgen and estrogen: released by ovaries and/or testes.
Hormones act on the brain or other structures of the body. Hormones are chemicals secreted
by endocrine organs in the body into the circulatory system, act at a distance from where they
are released, act on receptors in other organs and in the brain, act on general metabolism,
arousal, and growth, and act in the brain to regulate behaviour. Hormones are released through
the blood and will affect every place in your body. Their effect is slower than the effect of
neurotransmitters. Neurotransmitters: are released from the pre-synaptic cell and affects (in
Angstroms) the postsynaptic cells. In the brain, we have receptors that bind specific hormones.
- Chemicals that act both as neurotransmitters and hormones. ex. Neuropeptides (Y, CCK
- released by the gut, is a chemical that is in the brain and affects behaviour through
action in the brain -, oxytocin)
Thyroid releases its hormones in response to the TSH, released in the pituitary gland, which
then is released by TRH.
- The regulation of hormones is ultimately by the brain. The message starts at the brain.
- The anterior pituitary have different cell groups within the pituitary which release the pituitary
hormones. They release the ACTH (adreno-corticotropic hormone --> induce growth in the
adrenal gland). TSH also comes from the anterior pituitary.
- Gonads: are testes and ovaries. They release their hormones due to hormones coming from
the anterior pituitary called LH (stimulates the release of androgen and estrogen from the
gonads) and FSH (stimulates the follicles in the ovaries which synthesize and release estrogen).
- The pituitary releases TSH because it requires the stimulation from the TRH.
- Hormones are synthesized in cells in the base of the brain, they are released in a vascular
system in the base of the brain, which then are released through the vascular system.
- If the person is anxious, the level of adrenal hormones increases.
- The stressor can influence how can the pituitary gland can release its hormones. It can create
arousal state, responses to inflammation, and others.
Follicle-stimulating hormones and the luteinizing hormones stimulate the gonads. Anterior Pituitary
Hormones released here are under the control of releasing hormones from the hypothalamus;
Anterior pituitary secretes 6 main tropic hormonesLH: stimulates testes to produce
testosterone, the ovaries to produce eggs, and uterus to prepare for implantation; FSH:
stimulates ovulation, and sperm production in testes & important for synthesizes and release of
estrogen from the ovaries; TSH: stimulates thyroid to produce hormones; ACTH: stimulates
adrenal cortex to release hormones; Prolactin: milk let down; GH: general body growth
Stores and releases Oxytocin & Arginine Vasopressin (AVP), produced by hypothalamus and
transported to posterior pituitary from pituitary stalk then released to enter the circulation
AVP: related to thirst & water regulation; Increases blood pressure; Inhibits formation of urine;
Conserves water Oxytocin: triggers milk let-down Both have been implicated in social
Classification of Hormones: Steroid Hormones: composed of 4 strings of carbon atom that are
interconnected; 2 Types: A) Gonadal (estrogen & testosterone) B) Adrenal (cortisol)
Adrenal Cortex & Medulla
Produces Adrenocorticoids (i.e. Glucocorticoids) – accelerates breakdown of protein, has anti-
inflammatory effect, high levels can destroy brain cells (stress)
Produces Mineralocorticoids (i.e. aldosterone) – acts on kidney to retain Na+ and reduce
amount of urine produced
Produces sex hormones (i.e. androstenedione) – over-activity causes congenital adrenal
Releases adrenaline (epinephrine) & noradrenaline (norepinephrine)
- Negative feedback: two adrenal glands pump out cortisol (hormones) when there is an
increase in ACTH coming from the pituitary gland. The pituitary gland is stimulated to release
ACTH by cells in hypothalamus, at the base of the base, which release their hormones CRH into
- Positive feedback: High levels of CRH, produce high levels of ACTH, and these produce high
levels of cortisol.
- High levels of cortisol act back on the brain and turn off CRH. When CRH is turned off
(inhibited), and then ACTH goes down. When this happens, cortisol goes down again. What
happens to the negative feedback is that it is reduced (the inhibition is reduced). CRH goes up
- Study that was done to demonstrate the principle of negative feedback: we have 2 adrenal
glands (each about 10g) & they each pump out the same amount of cortisol. One adrenal gland
is removed, and half of the cortisol is removed. CRH is then increased, and ACTH again which
acts on the remaining adrenal gland causing it to release cortisol. The other adrenal gland will
double in size (20g). It shows that a king of negative feedback has just happened. A person
with low cortisol levels have problems sleeping.
Two systems work in stress:
1. Fast-acting pathway: Involves the epinephrine system. The adrenal medulla involves the
synthesizes epinephrine. Epinephrine activates very fast your arousal response.
2. Slow-acting pathway: The adrenal gland sit right away the kidney. A person who suffered
from trauma, their cortisol levels are very low. The system is exhausted and the person is at
risk because they do not have immune system function. The adrenal system gets messed up.
Hypophysectomy: procedure in which we removed the pituitary gland. We would have reduced
cortisol and a reduction in ACTH. Physiological Effects of glucocorticoids Behavioral Effects of glucocorticoids
1) direct control of glucose