4.1: The pituitary gland

Question 1

What is a hormone?

Answer 1

A messenger carried by the blood stream

Question 2

Two main hormone classifications

Answer 2

Peptide and Steroid

Question 3

Synthesis of Peptide hormones

Answer 3

synthesised as prohormones (long inactive chain) requiring further processes to activate

Question 4

Storage of Peptide hormones

Answer 4

Stored in vesicles, released by stimulus

Question 5

Receptors of peptide hormones

Answer 5

On cell membrane, then transducer signal using 2nd messenger (intracellular signal cascade)

Question 6

Synthesis of steroid hormones

Answer 6

Synthesised in series of reactions from cholesterol

Question 7

Storage of steroid hormones

Answer 7

Released immediately (constitutive secretion)

Question 8

Receptors of steroid hormones

Answer 8

Bind to intracellular receptors, change gene expression directly

Question 9

What bone does the pituitary gland sit in

Answer 9

Stella turcica of sphenoid bone

Question 10

Another name for anterior pituitary gland, and cell type

Answer 10

Adenohypophysis
Epithelial

Question 11

Origin of anterior pituitary gland

Answer 11

Upgrowth from oral ectoderm of primitive oral cavity - Rathkes pouch (in embryo)

Question 12

Another name of posterior pituitary gland and cell type

Answer 12

Neurohypophysis
Neural origin

Question 13

Where is the posterior pituitary gland derived from

Answer 13

Down growth of diencephalon that forms floor of the third ventricle (in embryo)

Question 14

What regulates anterior pituitary function

Answer 14

Hypothalamic-pituitary portal system

Question 15

How is the anterior pituitary gland regulated

Answer 15

Parvocellular neurones in the hypothalamus release signals which terminate at the median eminence.
Median eminence released hypothalamic releasing/inhibiting factors into capillary plexus in median eminence.
Factors carried by portal circulation to anterior pituitary.

Question 16

5 endocrine cells making up anterior pituitary

Answer 16

Somatotrophs
Lactotrophs
Corticotrophs
Thyrotrophs
Gonadotrophs

Question 17

Hypothalamo-pituitary portal system

Answer 17

Hypothalamic neurosecretory cells release hormones into hypothalamo-pituitary portal system
RHS and IHs travel in portal system to anterior pituitary
Stimulate or inhibit hormone release from anterior pituitary cells
Anterior pituitary hormones leave gland via blood

Question 18

Somatotrophs release

Answer 18

Growth hormone

Question 19

Lactotrophs release

Answer 19

Prolactin

Question 20

Thyrotrophs release

Answer 20

Thyroid stimulating hormone (TSH)

Question 21

Gonadotropins release

Answer 21

Luteinising hormone (LH)
Follicle stimulating hormone (FSH)

Question 22

Corticotrophs release

Answer 22

Adrenocorticotrophic hormone (ACTH)

Question 23

What regulates growth hormone

Answer 23

Releasing - growth hormone releasing hormone
Inhibiting - somatostatin

Question 24

What regulates prolactin

Answer 24

Inhibiting- dopamine

Question 25

What regulates thyroid stimulating hormone (TSH)

Answer 25

Releasing - thyrotrophin releasing hormone

Question 26

What regulates LH and FSH

Answer 26

Gonadotrophin releasing hormone

Question 27

What regulates Adrenocorticotrophic hormone (ACTH)

Answer 27

Release - corticotrophin releasing hormone

Question 28

Target of GH

Answer 28

General body tissues (liver)

Question 29

Target of prolactin

Answer 29

Breasts (lactating women)

Question 30

Target of TSH

Answer 30

Thyroid

Question 31

Target of Gonadotrophins (LH & FSH)

Answer 31

Testes and ovaries

Question 32

Target of ACTH

Answer 32

Adrenal cortex

Question 33

What sits above the pituitary gland

Answer 33

Optic chiasm

Question 34

What happens if a pituitary tumour compresses the optic chiasm

Answer 34

- bitemporal hemianopia Fibres from nasal retinae which cross at optic chiasm are compressed, preventing transmission of sensory information from lateral (temporal) visual fields to occipital lobe

Question 35

Mechanism of growth hormone action

Answer 35

Acts directly on body tissues but also stimulates insulin-like growth factor (IGF-1 and 2) which also acts

Question 36

Excess growth hormone can lead to

Answer 36

(ADULTS) - ACROMEGALY Coarsening of facial features (macroglossia and prominent nose) Prognathism: large jaw Increased hand and feet size Sweatiness Headache (CHILDREN) GIGANTISM

Question 37

2 posterior pituitary hormones

Answer 37

Arginine vasopressin (AVP) : Anti-diuretic hormone Oxytocin (Produced by hypothalamus put stored in posterior pituitary)

Question 38

Anatomy of posterior pituitary

Answer 38

Continuous with hypothalamus

Question 39

What is controlled in posterior pituitary regulation

Answer 39

Hypothalamic magnicellular neurons Supraoptic - AVP Paraventicular - oxytocin

Question 40

Regulation of posterior pituitary gland

Answer 40

Two sets of hypothalamic neurosecretory cells produce AVP and oxytocin and transport them to posterior pituitary Excitation of hypothalamic magnocellular neurones stimulates release of AVP or oxytocin, they diffuse into blood

Question 41

Physiological action of vasopressin (AVP / ADH)

Answer 41

Stimulation of water reabsorption in renal collecting duct, concentrating urine Vasoconstrictor, stimulating ACHT release from anterior pituitary

Question 42

How does vasopressin concentrate urine

Answer 42

AVP from blood binds to V2 receptor on cells lining lumen of collecting duct, Triggers intracellular signalling cascade Allows insertion of aquaporin-2 to membrane Water reabsorbed unit lumen Aquaporin-3 added to membrane to allow water to be reabsorbed into blood stream

Question 43

2 physiological actions of oxytocin

Answer 43

Uterus at parturition - myometrial cells - contraction - baby delivery Breast during lactation - myoepithelial cells - contraction- milk ejection

Question 44

2 physiological actions of oxytocin

Answer 44

Uterus at parturition - myometrial cells - contraction - baby delivery Breast during lactation - myoepithelial cells - contraction- milk ejection

Question 45

Role of anterior pituitary in lactation

Answer 45

Mechanical stimulation activates afferent pathways Signals integrated in hypothalamus and inhibit dopamine release from dopaminergic neurons Less dopamine = less inhibition of anterior pituitary Lactotrophs Increased plasma prolactin increases milk SECRETION in mammary glands

Question 46

Role of posterior pituitary in lactation

Answer 46

Mechanical stimulation activates afferent pathways Stimulate oxytocin in hypothalamus releasing neuron activity Action potentials travel down oxytocin neurons and oxytocin into blood Increased plasma oxytocin increases milk ejection in mammary glands