Arroyo: Posterior Pituitary Flashcards
1
Q
What are pituicytes?
A
- Packing and supporting cells in the posterior pituitary gland
- Compose most of the posterior pituitary
2
Q
What is the function of the posterior pituitary gland?
A
Stores and releases hormones into the close capillaries
3
Q
Main difference between anterior and posterior pituitary?
A
Pituitary hormones are produced in the hypothalamus but stored in and released from the posterior pituitary
NO ENDOCRINE CELLS
4
Q
What hormones are released by the posterior pituitary gland?
A
- Both are polypeptides - each have 9 amino acids
- Both are transported along the hypothalamo-hypophyseal tract in combination with neurophysin (carrier protein) to the nerve endings in the posterior pituitary gland where they are stored
-
ADH - antidiuretic hormone or vasopressin
- Decreased urine output
-
OT - oxytocin
- Initates labor, stimulates boobs to release milk, stimulates uterine contractions (when not in labor?)
5
Q
Where is ADH produced?
A
Hypothalamus
6
Q
What does ADH activate?
A
Second messenger systems
- cAMP
- IP3/Ca2+
7
Q
What are the two main effects of ADH?
A
- Increases water re-absorption (retention) by distal tubules and collecting ducts of kidneys = decrease osmotic pressure in blood
- Contraction of vascular SM = generalized vasoconstriction (regulated through action of IP3/Ca2+
8
Q
Factors controlling ADH release
A
- ↑ in pressure of ECF (increase in plasma osmolality) as in dehydration will stimulate hypothalamus to ↑ ADH secretion
- Decrease BV (³10%) ↑ ADH secretion
- Decrease arterial BP due to decrease BV ↑ ADH
- Age ↑ ADH secretion = water retention and hyponatremia
- Pain, emotional stress, physical trauma ↑ ADH
- Drugs (i.e. morphine, barbiturates, nicotine) ↑ ADH secretion
- Alcohol ↓ ADH secretion
9
Q
Abnormalities of ADH release: Hypo-/Hypersecretion
A
Hyposecretion: Diabetes insipidus
Hypersecretion: Syndrome of Inappropriate Anti-Diuretic Hormone (SIADH)
10
Q
Diabetes Insipidus
A
ADH hyposecretion = Diabetes Insipidus
- Enormous daily output of very dilute, watery urine
- Intense thirst: the patient drinks 2-20L of fluid/day
- Fluid intake cannot be limited or else you’d develop severe dehydration
11
Q
What are some causes of diabetes insipidus?
A
- Head trauma
- Brain tumor, irradiation of pituitary gland
- CNS infections (meningitis, encephalitis, tuberculosis)
12
Q
Syndrome of Inappropriate Anti-Diuretic Hormone (SIADH)
A
ADH hypersecretion = Syndrome of Inappropriate Anti-Diuretic Hormone (SIADH)
- Water retention causes dilutional decreased osmolality
- Decreased serum osmolality causes water to move into cells
- Decrease in Na+ and thirst can cause
- Weakness
- Muscle cramps
- Diarrhea
- If Na+ levels worsen, you develop neurological manifestations
- Lethargy
- Decrease in tendon reflexes
- Abdominal cramping, vomiting
- Coma
- Seizures
13
Q
Where is OT produced?
A
Paraventricular nucleus of the hypothalamus
14
Q
What are the actions of OT?
A
- Contraction of uterine SMs = enhances labor
- Contraction of mammary gland myoepithelial cells of the alveoli and ducts = ejection of milk in lactating women
- Milk let down
- Increases ejaculation in men
- Male/female SM contraction during orgasm
15
Q
OT vs. PRL?
A
Oxytocin is concerned with releasing or ejecting milk, while prolactin is concerned with synthesis and production of milk
16
Q
Control of OT release
A
- Control of oxytocin release - POSITIVE FEEDBACK
- Nipple stimulation (suckling reflex) ↑OT
- Visual or auditory stimuli from baby ↑OT
- Distension of uterus and cervix stretching during delivery ↑OT
- Psychological and emotional factors (fear, pain) ↓OT
- Alcohol ↓OT
- Hormones
- Progesterone ↓uterine sensitivity to OT
- Estrogen ↑uterine sensitivity to OT
17
Q
Pineal gland location
A
Part of the epithalamus
18
Q
What hormone(s) is/are produced by the pineal gland? What type of cell is producing that/those hormone(s)?
A
Pinealocytes produce melatonin (made from 5HT)
19
Q
What does melatonin do?
A
- Helps regulate circadian rhythm
- Protects against damage by free radicals
- Antioxidant
- Inhibits reproductive functions
- Inhibits GnRH
- Levels decrease at puberty
20
Q
What disorder can you develop during the winter, when the days are shorter and the nights are longer? Why?
A
Seasonal Affective Disorder (SAD)
- Melatonin is secreted in the dark, so people with SAD are sad (lol) because they have higher levels of melatonin
- Dysregulated circadian rhythm
21
Q
What effects might be observed if someone develops a pineal tumor?
A
Precocious puberty
22
Q
Thyroid gland appearance and location
A
- Butterfly shaped
- Inferior to larynx
- Largest pure endocrine gland
23
Q
Actions of the thyroid gland?
A
- Controls rate of metabolic processes
- Required for normal growth and development
24
Q
What hormone(s) does the thyroid gland produce? What is the action of that/those hormone(s)?
A
-
Thyroid hormone
- Increases metabolic rate
-
Calcitonin
- Lowers levels of blood Ca2+
- ↓ osteoclast activity
- ↑ osteoblast activity
25
What effects may be observed with **hyperthyroidism**?
* **Endemic goiter - lack of dietary iodine**
* High metabolic rate, weight loss, hyperactivity, always feeling hot, tachycardia
* Change in menstrual cycles
* Frequent BMs
* **Grave's disease - exophthalmos**
26
What effects may be observed with **hypothyroidism**?
* Hashimoto thyroiditis - adults
* Myxedema - adults
* Cretinism - children
27
Hashimoto thyroiditis
* Hashimoto thyroiditis - adults
* ↓TH
* Low metabolic rate, weight gain, fatigue, always cold
28
Myxedema
* Myxedema - adults
* Extreme hypothyroidism in adults
* General apathy, mental sluggishness, cold intolerance, decrease BMs
29
Cretinism
* Cretinism - children
* Extreme hypothyroidism in children
* Mental retardation, short stature, protruding tongue
30
Where are the **parathyroid glands** located?
4 on the posterior surface of the thyroid
31
What hormone(s) do/does the **parathyroid gland** produce?
PTH
32
**PTH** functions
* ↑ osteoclast activity
* ↓ osteoblast activity
* ↑ blood concentration of Ca2+
* Enhances reabsorption of Ca2+ at kidneys
33
What are the effects of **parathyroid** hyp**er**function?
Hyperfunction - **Moans, groans, stones, bones, and psychiatric overtones**
* **Osteoporosis** - lack of Ca2+ in bones; bone pain
* **Kidney stones** - caused by increased blood Ca2+; gets stuck in kidneys
* **Depression** - chemical imbalance
34
What are the effects of **parathyroid** hyp**o**function? What usually causes this?
* Usually caused by accidental removal of the parathyroid gland while removing the thyroid
* **Low blood Ca2+ levels**
* Muscle cramps
* Numbness and tingling
* Tetanus
* Weak
* Mood swings
* Brittle hair and nails
35
What organs have **secondary endocrine functions**?
* Gonads
* Intestines
* Kidneys
* Heart
* Thymus
* Adipose
36
What hormone(s) are produced by the **ovaries**?
* **Estrogens** - produced by _follicular cells_
* Targets **most cells**
* Support follicle maturation, secondary sex characteristics, behaviors
* **Inhibin** - produced by f_ollicular cells_
* Targets **pituitary** gland
* Inhibits secretion of FSH - **NEGATIVE FEEDBACK**
* **Progestins** - produced by _corpus luteum_
* Targets **uterus**, **mammary glands**
* Prepared uterus for implantation and mammary glands for secretion
* Used to initiate menses or not
37
What hormone(s) are produced by the **testes**?
Gonads: Testes
* **Androgens** - produced by _interstitial cells_
* Targets **most cells**
* Maturation of sperm, secondary sex characteristics
* **Inhibin** - produced by _nurse cells_
* Targets **pituitary** gland
* Inhibits secretion of FSH
38
What is observed when you have **hypersecretion of androgen hormones**?
Hirsutism or hypertrichosis
39
What hormone(s) are secreted by the intestines? What organs are targeted and what is/are its/their actions?
* Many hormones:
* **Secretin**
* **Gastrin**
* **Cholecystokinin**
* Target digestive organs
* Coordinate digestive activities
40
What hormone(s) are secreted by the kidneys? What does that/those hormone(s) do?
* **Renin**
* Targets adrenal and pituitary glands, kidneys
* Stimulates renin-angiotensin system
* Stimulates aldosterone and ADH release
* ↓water loss by kidney; ↑thirst and BP
41
What hormone(s) is/are secreted by the heart?
* **Natriuretic peptides**
* Stimulated by ↑BV, stretching heart tissues
* Targets kidneys, hypothalamus, adrenal glands
* ↑water and salt loss at kidneys, ↓thirst and secretion of ADH and aldosterone
42
What hormone(s) is/are secreted by the thymus?
* **Thymopoietin**
* **Thymosins**
* Target lymphocytes and other cells of the immune response
* Coordinate and regulate immune response
43
**Thymus** location
Yellow; right above heart; atrophies after puberty
44
What hormone(s) are secreted by adipose tissue?
* **Leptin**
* Targets hypothalamus
* ↓appetite; ↑gonadotropin synthesis
