Posterior Pituitary (ARROYO) Flashcards
The posterior pituitary gland is composed mainly of cells called “_______”, which act as packing and supporting cells.
Pituicytes: act as packing and supporting cells
- stores and releases hormones into the close capillaries
- these hormones are produced in hypothalamus
What two hormones does the Posterior Pituitary release?
ADH (vasopressin) and Oxytocin
note: these two hormones are produced in the hypothalamus and secreted from the posterior pituitary
_______ and _______ are manufactured in the hypothalamus, but released in the posterior pituitary.
Oxytocin and Vasopressin
What type of hormones is vasopressin and oxytocin?
Polypeptide hormones
note: both are transported slowly along the ‘hypothalamo-hypophyseal tract’ in combination with carrier protein called ‘neurophysin’, to the nerve endings in the posterior pituitary gland where they are stored
Antidiuretic hormone (ADH) is produced in the hypothalamus and activates what two second messenger systems?
- cAMP
- IP3/Ca2+
What are the 2 main effects of ADH?
- increases water re-absorption (retention) by distal tubules and collecting ducts of the kidneys, which decreases osmotic pressure of the blood
* this effect is regulated through the action of cAMP - Contraction of vascular smooth muscles —> generalized vasoconstriction
* this effect is regulated through the action of IP3/Ca2+
Discuss the control of ADH:
- Increase in osmotic pressure of the ECF (increase in plasma molality), as in dehydration which will stimulate the hypothalamus to increase ADH
- A decrease in blood volume > 10% causes an increase in ADH
- decrease in arterial blood pressure due to decreased blood volume causes an increase in ADH
- Age causes an increase in ADH secretion —> water retention and hyponatremia
- Pain, emotional stress and physical trauma —> increase ADH secretion
- Drugs, e.g. morphine, barbiturates and nicotine increase ADH secretion
- Alcohol causes an increase in ADH secretion
Hypersecretion of ADH can lead to ________.
Syndrome of inappropriate Anti-Diuretic Hormone (SIADH)
- occurrs when there is over secretion of ADH from posterior pituitary
- causes a decrease in Na+
Symptoms include:
- thirst
- muscle weakness
- muscle cramps
- diarrhea
If Na levels worsens, development of neurological manifestations:
- lethargy
- decrease tendon flexes
- abdominal cramping, vomiting
- coma
- seizures
Hyposecretion of ADH, which causes a lack of ADH can lead to ________.
Diabetes insipidus
__________ is produced mainly in the paraventricular nucleus of the hypothalamus.
Oxytocin
What is the function of Oxytocin?
Function of oxytocin:
- contraction of smooth muscles of the uterus to enhance labor
- contraction of mammary gland myoepithelial cells of the alveoli and the ducts —> ejection of milk as a reflex in lactating women
- increases ejaculation in men
Remember: oxytocin is concerned w/ releasing or ejection of milk, while prolactin is concerned with synthesis and production of milk
What type of feedback is observed with the hormone Oxytocin?
A. Positive feedback
B. Negative feedback
A. Positive feedback
- Uterine contractions
- Pitocin
- Male/female smooth muscle contraction during orgasm
- Milk let-down
The more the baby sucks on the nipples the more oxytocin is released (positive-feedback)
Discuss the control of oxytocin release (6):
- stimulation of nipple (suckling reflex) = increases oxytocin secretion
- visual or auditory stimuli from the baby = increases oxytocin secretion
- distension of uterus and stretching of cervix during delivery = increases oxytocin release
- psychological and emotional factors e.g. fear, anxiet, pain = decrease in oxytocin secretion
- alcohol = decrease oxytocin secretion
- Hormone:
- progesterone = decreases uterine sensitivity to oxytocin
- estrogen causes an increase in uterine sensitivity to oxytocin
Discuss the Pineal gland:
- part of the ________.
- what type of cells and what do they produce?
- made from ______.
- Helps regulate ________
- SAD?
- Protects against damage by free radicals:
- Inhibits what 3 reproductive functions?
Pineal gland:
- part of the epithalamus
- Pinealocytes produce melatonin
- made from seratonin
- helps regulate circadian rhythm
- increased secretion in the dark can lead to seasonal affective disorder (SAD)
- Protects agains damage by free radicals (antioxidant)
- inhibits reproductive functions
- inhibits release of HnRH
- levels decrease at puberty
- pineal tumors can cause precocious puberty
What hormone does the Pineal gland produce?
Melatonin
Discuss the thyroid gland:
- What shape is it?
- Where is it located?
- known as the _______.
- What are its actions?
Thyroid gland
- Butterfly shaped
- inferior to larynx
- largest pure endocrine organ
- Actions:
- controls metabolic rate
- required for normal growth and development
What two hormones does the Thyroid gland produce and what do those hormones do?
Thyroid hormone = increases metabolic rate
Calcitonin = lowers level of blood Ca by decreasing osteoclast activity and increasing osteoblast activity
What does Calcitonin do to blood Ca levels?
decreases it
Lack of dietary iodine can result in _______.
goiter
Discuss Hyperthyroidism:
Hyperthyroidism:
- excessive TH production
- High metabolic rate, weight loss, hyperactivity, always feeling hot, tachycardia
- Grave’s disease
- Exopthalmos (bulging eyes)
- Enlargement of thyroid gland (goiter)
- Change in menstrual cycles
- Erectile dysfunction or libido
- Frequent bowel movements
- Bulging eyes (Graves’ ophthalmopathy)
Discuss Hypothyroidism:
Hypothyroidism
- Hashimoto thyroiditis
- decreased production of TH
- low metabolic rate, weight gain, fatigue and always feeling cold
- Myxedema
- extreme hypothyroidism in adults
- general apathy, mental sluggishness, cold intolerance, obese, decreased bowel activity
Hypothyroidism in adults is termed:
A. Myxedema
B. Cretinism
A. Myxedema
Hypothyroidism in children is termed:
A. Myxedema
B. Cretinism
B. Cretinism
Cretinism:
- extreme hypothyroidism in children
- retardation of mental faculties, short stature, and protruding tongue
Discuss the Parathyroid gland:
Parathyroid gland
- four glands on the posterior surface of the thyroid gland
- produces PTH (parathyroid hormone)
- Functions:
- increases osteoclastic activity and decreases osteoblast activity
- increases blood concentration of Ca2+
- Enhances reabsorption of Ca2+ at kidneys
