Hypothalamus – Pituitary Loop

Question 1

true or false:

the hypothalamus is where the nervous, endocrine, and circulatory systems interface.

Answer 1

true. Shared boundary for all

Question 2

Hypothalamus and stucture

Answer 2

lies under the thalamus

Forms from the floor and part of the roof of the third ventricle (space in the brain)

Brain tissue therefore its nervous and neural tissue

Pituitary Gland hangs below the Hypothalamus and is connected to it by the infundibulum or pituitary stalk (1cm in dia)

Rests in a small depression in the sphenoid bone called the sella turcica

Question 3

The pituitary is also know as

Answer 3

hypophysis

Question 4

Anterior pituitary

Answer 4

derived from roof of mouth and composed of glandular tissue which produces and secretes hormones

Known as adenohypophysis (“adeno” meaning gland)

Produces mainly tropic hormones

Question 5

Posterior pituitary

Answer 5

derived from the brain and is composed of nerve tissue. Functions as a storage silo.
Known as neurohypophysis (“neuro” meaning nerve)
Functions as a storage silo

Question 6

Anterior pituitary hormone release

Answer 6

is controlled by hypothalamus:
5 realsesing hormones
and 2 inhibiting hormones

Question 7

5 Releasing hormones (releasing factors) of the hypothalamus

Answer 7

• TRH (Thyroid Releasing Hormone) turns on* (stimulates, releases) TSH (Thyroid Stimulating Hormone)
• CRH (Corticotropin Releasing Hormone) turns on ACTH (Adrenocorticotropic Hormone)
• GnRH (Gonadotropin Releasing Hormone) turns on FSH (Follicle-stimulating Hormone) and LH (Luteinizing Hormone)
• PRH or PRF(Prolactin Releasing Hormone/Factor) turns on PRL (Prolactin)
• GHRH (Growth Hormone Releasing Hormone) turns on GH (Growth Hormone or Somatotrophic Hormone or Somatotropin)

Question 8

2 Inhibiting hormones of hypothalmus

Answer 8

• PIH or PIF (Prolactin Inhibiting Hormone/Factor) turns off PRL (Prolactin)
• GHIH (aka SS or somatostatin) Growth Hormone Inhibiting Hormone turns off GH (Growth Hormone)

Question 9

anterior pituitary secretes…

Answer 9

TSH stimulates the thyroid to produce thyroid hormone

ACTH stimulates the adrenal cortex to produce corticosteroids: aldosterone and cortisol

FSH stimulates follicle growth and ovarian estrogen production; stimulates sperm production and androgen-binding protein

LH has a role in ovulation and the growth of the corpus luteum; stimulates androgen secretion by interstitial cells in testes

GH (aka somatrotropic hormone) stimulates growth of skeletal epiphyseal plates and body to synthesize protein

PRL stimulates mammary glands in breast to make milk

MSH stimulates melanocytes to produce and release melanin (pigmentation of the skin)

Question 10

Posterior pituitary secretes…

Answer 10

Secretes two hormones that have been produced in the hypothalamus
From Paraventricular Hypo nucleus:
Oxytocin
From Supraoptic Hypo nucleus:
ADH (Antidiuretic Hormone) aka Vasopressin

Question 11

Release of Oxytocin

Answer 11

Stimulating stretch receptors in the cervix and uterus and suckling of the breast

No known conditions that result from hypo or hypersecretion of oxytocin

Release is subject to both positive and negative feedback control

Question 12

Release of ADH

Answer 12

ADH (Antidiuretic Hormone) causes reabsorption of water in the distal convoluted tubules of the kidneys

Stimulus for its release is an increase in the osmotic pressure of the blood, so is subject to both positive and negative feedback control
as detected by osmoreceptors in the hypothalamus

ADH also reduces the rate of sweat formation

ADH = Vasopressin. Also causes vasoconstriction of arterioles following major fluid loss such as haemorrhage

Question 13

Hyposecretion of ADH

Answer 13

• Diuresis: very large quantity of dilute urine is produced.
• Depletion of body water
• Thirst
• Fluid & electrolyte Imbalance
• Medical condition – Diabetes -Insipidus

Question 14

Hypersecretion of ADH

Answer 14

-Neurosurgery or hypothalamic injury
-Ectopic secretion of ADH by cancer cells (rare – making and secretion of ADH by cells in other parts of the body)
especially lung cancer
-General anaesthesia
-Administration of certain drugs

Question 15

Effects of hypersecretion

ADH

Answer 15

• Fluid retention and sodium dilution
• Hyponatraemia
• Hypo-osmolarity of the blood
• Weight gain
• Brain oedema: Headache and disorientation leading to Coma and death

Question 16

FSH

Answer 16

(Follicle Stimulating Hormone)

Stimulates the development of the ovarian follicle in females leading to oestrogen production.

Stimulates the Sertoli cells in the seminiferous tubules in males leading to sperm production.

Question 17

LH

Answer 17

(Luteinising Hormone)
In females, triggers ovulation and stimulates production of oestrogen and progesterone by ovaries.

Is involved in the formation of the corpus luteum.

In males, stimulates testosterone production by the interstitial (Leydig) cells

Question 18

FSH and LH Hyposecretion

Answer 18

Can cause sterility and lack of sexual development and maturity
Can cause gonadal atrophy

Question 19

FSH and LH Hypersecretion

Answer 19

There are NO IMPORTANT EFFECTS of HYPERSECRETION of these hormones.

Question 20

Growth Hormone (Somatostatin)

Answer 20

-Promotes increase in cell size and cell division especially in:
Bone cells, Skeletal muscle cells and Cartilage cells.
-Regulates growth of the viscera.
-These are anabolic effects.
-Many effects on metabolism

Question 21

hypersecretion of Growth Hormone (Somatostatin)

Answer 21

Depending on what age/stage the surplus GH is produced, the person may develop either: Gigantism or
Acromegaly.

Question 22

Pituitary Gigantism

Answer 22

Very rare
-Results from hypersecretion of GH before epiphyseal closure
Bone overgrowth with both length and width of bone increased
Body is in correct proportions
Height may be more than 8 feet

Question 23

Acromegaly

Answer 23

-Results from hypersecretion of 
GH after epiphyseal closure 
-ages of 20-40
-usually caused by an adenoma of the pituitary gland
-Leads to periosteal overgrowth
-Overgrowth of the mandible 
Bone overgrowth and soft tissue thickening lead to coarsening of facial features and deepening of voice
-Barrel chest
-Hands and feet widen and enlarge

Question 24

Growth Hormone - Hyposecretion

Answer 24

Pituitary dwarfism:
Small size but normal proportions, unlike cretinism where proportions are infantile
It is sometimes hereditary

Question 25

Hyposecretion

Prolactin

Answer 25

Leads to poor milk production

Question 26

Hypersecretion

prolactin

Answer 26

Leads to Glactorrhoea –a milky nipple discharge unrelated to breastfeeding