The Pituitary Gland

Question 1

Two classes of hormones?

Answer 1

Peptide and steroid.

Question 2

How are peptide hormones synthesised?

Answer 2

Synthesised as pro hormones. Further processing such as cleavage to activate.

Question 3

How are peptides hormones stored?

Answer 3

Stored as vesicles.

Question 4

How do peptides hormones create a signal?

Answer 4

Transduce signal using 2nd messenger systems.

Question 5

How are steroids synthesised?

Answer 5

Synthesised from cholesterol.

Question 6

How are steroids released compared to peptides?

Answer 6

Released immediately while peptide secretion is regulated.

Question 7

How do steroids create a signal?

Answer 7

Bind to intracellular receptors and alter gene expression directly.

Question 8

What bone holds to pituitary gland?

Answer 8

Sella turcica of sphenoid bone.

Question 9

Another name for the anterior pituitary?

Answer 9

Adenohypophysis.

Question 10

Another name for the posterior pituitary?

Answer 10

Neurohypophysis.

Question 11

What is the optic chiasm?

Answer 11

Optic nerve crossover. Where neurones from the nasal retina cross over.

Question 12

Where does the anterior pituitary gland grow from during fetal development?

Answer 12

Upgrowth from oral ectoderm.

Question 13

Where does the posterior pituitary gland grow from during fetal development?

Answer 13

Downwards growth from diencephalon.

Question 14

What is Rathke’s pouch?

Answer 14

Is an ectodermal invagination of the roof of the developing embryonic mouth.

Question 15

What controls the anterior pituitary?

Answer 15

Hypothalamus.

Question 16

What endocrine cells are present in anterior pituitary?

Answer 16

Somatotrophs, Lactotrophs, Corticotrophs, Thyrotrophs and Gonadotrophs.

Question 17

What hormones are secreted by the anterior pituitary gland?

Answer 17

Growth hormone. Prolactin, TSH, LH and FSH, Adrenocorticotrophic hormone.

Question 18

What hormones are secreted by the hypothalamus?

Answer 18

GHRH, Somatostatin, Dopamine, Thyrotrophin releasing hormone, Gonadotrophin releasing hormone and Corticotrophin releasing hormone.

Question 19

What does growth hormone do?

Answer 19

Body tissues growth and release of IGF-1 from liver.

Question 20

What does somatostatin do?

Answer 20

Inhibit release of growth hormone.

Question 21

What does a decrease in dopamine do?

Answer 21

Increase in prolactin.

Question 22

What can a pituitary tumour result in?

Answer 22

Compression of optic chiasm can lead to bitemporal hemianopia. Prevents transmission of information from lateral visual fields to occipital lobes.

Question 23

What is acromegaly?

Answer 23

Excess growth hormone production.

Question 24

Symptoms of agromegaly?

Answer 24

Increased hand and feet size. Macroglossia. Prominent nose.

Question 25

Key difference between posterior pituitary gland and anterior?

Answer 25

Posterior doesn't produce hormones.

Question 26

What hormones does the posterior pituitary gland store?

Answer 26

Oxytocin and arginine vasopressin.

Question 27

Where are oxytocin and arginine vasopressin produced?

Answer 27

Hypothalamus.

Question 28

Explain the release of thyroxine

Answer 28

Axon terminals of parvocellular neurones release thyrotrophin releasing hormone (TRH) into hypophyseal portal system. TRH travels through the capillaries of the portal system to anterior pituitary gland. TRH binds to thyrotrophs and stimulates release of TSH. TSH leaves pituitary gland via the blood and travels to thyroid gland to stimulate release of thyroid hormone.

Question 29

Explain release of arginine vasopressin and oxytocin

Answer 29

Arginine vasopressin produced in supraoptic nucleus. Oxytocin produced in paraventricular nucleus. Hormones travel down neuronal axons in pituitary stalk. Enter posterior pituitary and stored. Excitation of hypothalamic magnocellular neurones releases AVP or oxytocin. These diffuse into capillaries.

Question 30

Physiological action of arginine vasopressin?

Answer 30

Anti-diuretic hormone, vasoconstrictor and stimulates ACTH release from anterior pituitary.

Question 31

Arginine vasopressin anti diuretic mechanism?

Answer 31

AVP binds to V2 receptor. Leads to aquaporin-2 channels bind to apical membrane of kidney duct cell. Allows water to move into duct cell from urine and so this leads to more concentrated urine.

Question 32

Physiological action of oxytocin?

Answer 32

Causes contraction of myometrial and myoepithelial cells leading to delivery of baby and milk ejection.

Question 33

Explain process of lactation?

Answer 33

Mechanical stimulation of nipple. Action potentials in ascending sensory pathway, inhibit dopamine release from dopaminergic neurones and stimulate oxytocin releasing neuron activity. Inhibition of dopamine leads to less inhibition of anterior pituitary lactotrophs. Oxytocin produced in hypothalamus and released from posterior pituitary. Increased plasma prolactin leads to increased milk production in mammary glands. Increased plasma oxytocin leads to increased milk ejection.

Question 34

What is T3?

Answer 34

Triiodothyronine.

Question 35

Description of parvocellular neurones?

Answer 35

Short hypothalamic neurones that release stimulatory/inhibitory factors into capillary plexus.

Question 36

What nuclei is AVP produced in?

Answer 36

Supraoptic nucleus.

Question 37

What nuclei is oxytocin produced in?

Answer 37

Paraventricular nucleus.