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D.5 Hormones and Metabolism (Regulation of milk secretion (Prolactin…
D.5 Hormones and Metabolism
Injection of growth hormone by athletes
effects
increase in muscle mass
greater muscle strength
tired muscle recover quickly
train harder
train often
risky in health (banned by most international federation)
Availability
genetically modified
produced in large quantity
mechanism
1) Growth hormone binds to liver cells
2) stimulates the release of insulin like growth factor
3) circulates in blood
4) stimulates bone and cartilage growth
Regulation of milk secretion
Prolactin Hormone
produced by anterior pituitary in vertebrae species
stimulates mammary gland to grow
stimulate production of milk
During Pregnancy
High level of Estrogen
increase prolactin production
inhibit prolactin effect on mammary gland
Abrupt decline in estrogen and progestone
removes the inhibition on prolactin
begin milk production
Nursing by an infant
release of milk depends on hormone oxytocin
stimulate the continued creation of prolactin
stimulate oxytocin release
Oxytocin Hormone
produced by neurosecretory cells in hypothalamus
stores in posterior pituitary gland
stimulates contraction of cells that surround the holding of milk leading to ejection of milk
Role of Hypothalamus
links the nervous system to endocrine system via pituitary gland
secretes releasing factor
1) releasing factors are carried from the hypothalamus to the anterior pituitary gland by portal vein
2) branches into anterior pituitary capillaries
3) releasing factors leave blood across the capillaries and control the release
4) stimulation by appropriate releasing factor or hormone, a given anterior pituitary hormone is secreted into the capillaries
5) the anterior pituitary capillaries rejoin to form vein through which the pituitary hormones leaves to body parts by blood
Examples
Hypophysiotropic hormones
Thyrotropin-releasing Hormone (TRH)
Negative feedback
blood solute concentration monitored by osmoreceptors in hypothalamus
high solute concentration
impulse sent cause ADH secretion increase
blood solute concentration drops
Low solute concentration
few impulse sent cause ADH secretion decrease
blood solute concentration rise
Pituitary Hormone
anterior pituitary synthesized and secretes number of hormones
control growth - Growth Hormone (GH)
control reproduction
Follicle Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
control Homeostasis
posterior pituitary synthesize hormone
1) synthesized in neurosecretory cells found in the hypothalamus
2) hormones travel down the axons of neurosecretory cells
3) hormones are stored at the end of axons until impulse passes down the axon from hypothalamus
4) stimulating secretion
e.g Oxytocin and ADH