Physiological response to hormones depends on
- Concentration of hormone
= free, biologically active fraction - Sensitivity of target cell
Endocrine diseases
- Too little hormone activity
- Hyposecretion
- Increased clearance
- Tissue resistance (insensitivity) - Too much hormone activity
- Hypersecretion
- Reduced plasma protein binding
- Reduced clearance
- Excessive response at target tissue
Hypothalamus
Made up of
* Nuclei (concentrations of neuronal cell bodies)
* Nerve tracts (axons)
- Regulates and coordinates responses to changes in the external and internal environment
- Regulates behaviour
e.g. reproductive, feeding, rage - Vegetative role - maintains homeostasis
e.g. body temperature
metabolism (hunger, satiety, body mass, metabolic rate)
water balance (blood volume, thirst/intake, urine output)
growth
stress
reproduction
Inputs neural humoral ->
Hypothalamus integrates ->
Outputs neural humoral
Posterior Pituitary Gland
2 main neurohormones:
- Vasopressin
(aka Anti-diuretic Hormone - ADH)
- Oxytocin
Both are peptides with 9 amino acid residues
Oxytocin and vasopressin are
expressed in both the SON and PVN
A single neuron only expresses one of these peptides
Vasopressin
Actions
* Decrease water excretion kidneys
“anti-diuretic”
* Vasoconstriction
Secretion is regulated by
* [solute] in ECF
* blood volume
Oxytocin
Actions
* Parturition: stimulates contraction of uterine smooth muscle
* Lactation: milk ejection during breastfeeding due to contraction of smooth muscle
Secretion is stimulated by;
* Pressure of baby in birth canal
* Sucking baby
Secretion is inhibited by fear, anxiety
May also play important roles in males
Milk ejection reflex
- Auditory and optic input
- down the hypothalamo-hypophyseal tract
- increased firing rate causes increased oxytocin secretion
- oxytocin conc increases
- to myoepithelial cells
- milk release
Oxytocin signal transduction
in myoepithelial cells
diagram
If we wanted to determine one of your hormones and whether it was in the normal range, what would be do?
and why?
we would take a blood sample
- and measure (ideally) the free biologically active fraction of that hormone
this is because this is the fraction that binds to receptors and has physiological effects
hormone level testing lingo
hyper - high secretion
hypo - low secretion
what are some main lipophilic hormones?
steroid hormones e.g. testosterone, estrogen, progesterone
- they are made from cholesterol, are water insoluble and fat soluble
where are the major groups of oxytocin neurons in the hypothalamus
supraoptic nucleus
and the paraventricular nucleus
hypothalamus summary
- neural tissue and endocrine gland
- secretes neurohormones
- functional division of endocrine output
- posterior pituitary gland
(oxytocin and vasopressin) - anterior pituitary gland
(prolactin and mammary gland)
(growth hormone and the control of growth)
- posterior pituitary gland
vasopressin (aka ADH) and
oxytocin
short peptides (9aa)
half life of 5-10 minutes
synthesised in paraventricular and supraoptic nucleuses of the hypothalamus
vasopressin
actions:
- decrease water excretion in kidneys “anti-diuretic”
- vasoconstriction
secretion is regulated by:
- [solute] (conc) in extracellular fluid (ECF)
- blood volume
(affects kidney function (Anti diuretic hormone = ADH)
and blood pressure control (vasopressin) (constricts)
oxytocin
actions:
parturition - stimulates contraction of uterine smooth muscle
lactation - milk ejection during breastfeeding due to contraction of smooth muscle
secretion is stimulated by:
- pressure of baby in birth canal
- sucking baby
secretion is inhibited by:
- fear or anxiety
somatotrophs
growth hormone (GH)
lactotrophs
prolactin
gonadotrophs
LH (luteinising hormone)
FSH (follicle stimulating hormone)
“gonadotrophins:
thyrotrophs
TSH (thyroid stimulating hormone)
corticotrophs
ACTH (adrenocorticotrophic hormone)
