WVU PHYSIO 241 EXAM 7
3 ways to trigger hormone release
1. Neural Stimulation: ex. Neuroendocrine reflex
2. Hormonal Stimulation: A hormone stimulates release of another hormone
3. Humoral Stimulation: a substance in body fluid stimulates release of a hormone
Negative Feedback
output counteracts a change in input
Positive Feedback
amplifies initial effect of hormone
Neuroendocrine Reflexes
produce sudden increase in hormone secretion
Diurnal Rhythms
Hormone fluctuation over 24 hours
Hyposecretion
1degree = less secretion due to glandular abnormality: genetic, dietary, chemical,
immunologic, 2nd to disease process, iatrogenic, idiopathic
2degree = less secretion as result of less stimulus by tropic hormone
Hypersecretion
1degree = more secretion due to glandular abnormality
2degree = more secretion due to more stimulation of gland
Possible Causes-tumors, immunologic factors, substance abuse
Lack of Receptors
Ex: testicular feminization syndrome
Lack of cellular component in response pathway
Ex: enzyme, 2nd messenger
Permissiveness
one hormone must be present for full effect of another hormone
Synergism
several hormone are complimentary; combines effect greater than that of one (not
additive
Antagonism
inhibition of or interference with the action of one substance or organism by another
Integration Center of the Hypothalamus
-body temp
-thirst & urine output
-appetite
emotions and behaviors
, -sleep-wake cycles
-uterine contraction and milk ejection
Anterior Pituitary Hormones & Posterior Pituitary Hormones
-Bridge to endocrine system
-stimulates or inhibits A.P. hormone secretion via releasing and inhibiting hormones
-synthesizes P.P. hormones
Anterior Lobe
true glandular tissue
-Adenohypophysis
Posterior Lobe
Extension of hypothalamus
-Neurohypophysis
Two Populations of Neurosecretory Neurons
-Terminals of posterior lobe
-Hormones
Terminals
supported by pituicytes
Hormones
1. Vasopressin
2. Oxytocin
Vasopressin aka Antidiuretic Hormone
Its release is triggered by hypothalamic osmoreceptors (dominant factor) and it targets
the kidney (increases H2O permeability) and arteriolar smooth muscle (causes
contraction)
Oxytocin
Its releases is triggered by stimulation of cervical mechanoreceptors and
mechanoreceptors in the nipple.
It contracts the myometrium at the uterus and myoepithelial at breast.
Hypothalamic Releasing Hormones (AP hormone secretions regulation)
stimulates release of hormone from anterior pituitary cells
Hypothalamic Inhibiting Hormones (AP hormone secretions regulation)
inhibits release of hormone from anterior pituitary cells
Hypothalamic-Hupophyseal Portal System
-Capillary-to-capillary link (direct route from hypothalamus to pituitary)
-Neurosecretory neurons terminate on the capillaries of portal system
Lactotropes
Prolactin (PRL)
-Target: mammary gland
-Effect: Breast growth and milk secretion
Somatotropes
growth hormone (GH)
Target: Bones/muscles
Effect: growth development
Thyrotropes
3 ways to trigger hormone release
1. Neural Stimulation: ex. Neuroendocrine reflex
2. Hormonal Stimulation: A hormone stimulates release of another hormone
3. Humoral Stimulation: a substance in body fluid stimulates release of a hormone
Negative Feedback
output counteracts a change in input
Positive Feedback
amplifies initial effect of hormone
Neuroendocrine Reflexes
produce sudden increase in hormone secretion
Diurnal Rhythms
Hormone fluctuation over 24 hours
Hyposecretion
1degree = less secretion due to glandular abnormality: genetic, dietary, chemical,
immunologic, 2nd to disease process, iatrogenic, idiopathic
2degree = less secretion as result of less stimulus by tropic hormone
Hypersecretion
1degree = more secretion due to glandular abnormality
2degree = more secretion due to more stimulation of gland
Possible Causes-tumors, immunologic factors, substance abuse
Lack of Receptors
Ex: testicular feminization syndrome
Lack of cellular component in response pathway
Ex: enzyme, 2nd messenger
Permissiveness
one hormone must be present for full effect of another hormone
Synergism
several hormone are complimentary; combines effect greater than that of one (not
additive
Antagonism
inhibition of or interference with the action of one substance or organism by another
Integration Center of the Hypothalamus
-body temp
-thirst & urine output
-appetite
emotions and behaviors
, -sleep-wake cycles
-uterine contraction and milk ejection
Anterior Pituitary Hormones & Posterior Pituitary Hormones
-Bridge to endocrine system
-stimulates or inhibits A.P. hormone secretion via releasing and inhibiting hormones
-synthesizes P.P. hormones
Anterior Lobe
true glandular tissue
-Adenohypophysis
Posterior Lobe
Extension of hypothalamus
-Neurohypophysis
Two Populations of Neurosecretory Neurons
-Terminals of posterior lobe
-Hormones
Terminals
supported by pituicytes
Hormones
1. Vasopressin
2. Oxytocin
Vasopressin aka Antidiuretic Hormone
Its release is triggered by hypothalamic osmoreceptors (dominant factor) and it targets
the kidney (increases H2O permeability) and arteriolar smooth muscle (causes
contraction)
Oxytocin
Its releases is triggered by stimulation of cervical mechanoreceptors and
mechanoreceptors in the nipple.
It contracts the myometrium at the uterus and myoepithelial at breast.
Hypothalamic Releasing Hormones (AP hormone secretions regulation)
stimulates release of hormone from anterior pituitary cells
Hypothalamic Inhibiting Hormones (AP hormone secretions regulation)
inhibits release of hormone from anterior pituitary cells
Hypothalamic-Hupophyseal Portal System
-Capillary-to-capillary link (direct route from hypothalamus to pituitary)
-Neurosecretory neurons terminate on the capillaries of portal system
Lactotropes
Prolactin (PRL)
-Target: mammary gland
-Effect: Breast growth and milk secretion
Somatotropes
growth hormone (GH)
Target: Bones/muscles
Effect: growth development
Thyrotropes
