Pituitary Gland

Question 1

What is a hormone

Answer 1

A messenger that is carried from the organ where they are produced to the organ where they affected by means of bloodstream

Question 2

What are the two types of hormone

Answer 2

Peptide and steroid

Question 3

Peptide hormone synthesis

Answer 3

Synthesised as pro hormones requiring further processing for example cleavage to activate. So pro hormones are basically long peptide chains for example Insulin

Question 4

Steroid hormone synthesis

Answer 4

Synthesising a series of reactions from cholesterol

Question 5

Stores with peptide hormones

Answer 5

They are stored in vesicles just beneath the membrane of cells and these are only released when the vesicles fuse with the cell membrane

Question 6

Steroid home storage

Answer 6

Released immediately so it’s constitutive secretion

Question 7

Peptide hormone receptors

Answer 7

Find receptors on the cell membrane and transducer signal using second messenger system

Question 8

Steroid hormone receptors

Answer 8

Bind to intracellular receptors to change gene expression directly

Question 9

What is the name of the neurons that regulate anterior pituitary function

Answer 9

Parvocellular neurons

Question 10

Characteristics of hypothalamic parvocellular neurons

Answer 10

Short and terminate on median eminence
Release hypothalamic releasing – factors into capillary plexus and median Eminence
These hypothalamic regulatory factors are carried by portal circulation to anterior pituitary

Question 11

Name the anterior pituitary

Answer 11

Adenohypophysis

Question 12

Why is the anterior pituitary anatomically distinct from the hypothalamus

Answer 12

It’s not neuronal instead it has endocrine cells

Question 13

Five types of endocrine cells (cells which contain hormones)

Answer 13

Somatotrophs
Lactotrophs
Corticotrophs
Thyrotrophs 
Gonadotrophs

Question 14

What are the endocrine cells in the anterior pituitary gland controlled by

Answer 14

Regulated by hypothalamic releasing – inhibiting factors via hypophyseal- pituitary portal system

Question 15

Hypothalamus-pituitary portal system

Answer 15

) axon terminals of hypothalamic neurosecretory cells release hormones ( Releasing hormones and inhibitory hormones ) into the hypothalamo-pituitary portal system ( diffuse in as there are lots of fenestrations in the blood vessels)

These travel in the portal system to the anterior pituitary

The releasing hormones and inhibitory hormones stimulate or inhibit the release of hormones from the anterior pituitary cells

The anterior pituitary hormones leave the gland via the blood

Question 16

Thyroid hormone production

Answer 16

Axon terminals of hypothalamic neurosecretory cells release TRH into hypothalamic-hypophysial portal system

TRH travels in the portal system to the anterior pituitary

TRH stimulates the release of the Thyroid Stimulating Hormone ( thyrotrophin) from anterior pituitary thyrotrophs

TSH leaves the gland via the blood to travel to the thyroid gland to stimulate thyroid hormone release ( thyroxine )

Question 17

Somatotrophs

Answer 17

Growth hormone ( somatotrophin )

Question 18

Lactotrophs

Answer 18

Prolactin

Question 19

Thyrotrophs

Answer 19

Thyroid stimulating hormone ( TSH) Thyrotrophin

Question 20

Gonadotrophs

Answer 20

LH

FSH

Question 21

Corticotrophs

Answer 21

Adrenocorticotrophic hormone ( ACTH, corticotrophin )

Question 22

Growth hormone regulators

Answer 22

Growth hormone releasing hormone - on switch

Somatostatin - off switch

Question 23

Prolactin

Answer 23

Dopamine ( inhibitory )

Question 24

TSH ( thyrotrophin)

Answer 24

Thyrotrophin releasing hormone

Question 25

LH , FSH

Answer 25

Gonadotropin releasing hormone

Question 26

Adrenocorticotrophic hormone ( ACTH, corriocotrophin )

Answer 26

Corticotrophin releasing hormone

Question 27

Target cells of growth hormone

Answer 27

General body tissues in particular liver

Question 28

Prolactin target

Answer 28

BreastS of lactating women

Question 29

TSH target

Answer 29

Thyroid

Question 30

Gonadotrophs ( LH and FSH) target

Answer 30

Testes and ovaries

Question 31

Adrenocorticotrophic hormone target

Answer 31

Adrenal cortex

Question 32

What may cause a bitemporal hemianopia

Answer 32

Cannot see temporal aspects of visual field / outer aspects due to pituitary tumour which has grown out of sella tursica and onto optic chiasm ( supra sella) Fibres from the nasal ( medial) retinae cross at the optic chiasm and compression of the optic chiasm by a pituitary tumour prevents the transmission of sensory information from lateral visual fields to the occipital lobe

Question 33

Milk production ( reflex arc)

Answer 33

Mechanical stimulation of nipple and surrounding area activates afferent sensory pathways Afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurones Less dopamine in the hypothalamic pituitary portal system causes less inhibition of anterior pituitary lactotrophs Increased plasma prolactin increases milk secretion in mammary glands which travels by blood to nipple

Question 34

Mechanisms of growth hormone action

Answer 34

Direct secretion of somatotrophin onto body tissues Indirectly somatotrophin travels to liver where it stimulates Insulin like Growth factor ( somatomedin ) IGF-1 then binds to receptors on muscle and bone and can also stimulate growth

Question 35

Gigantism

Answer 35

Too much growth hormone release before puberty ends leads to gigantism as the femur / epiphyseal plates only fuse together after puberty has finished But if too much growth hormone happens after puberty has fished once the growth plates have fused , you can’t grow taller and this is called acromegaly. But get other physiological changes

Question 36

Physiological features of acromegaly

Answer 36

Coarsening of facial features Macroglossia ( increased size of tongue ) Prominent nose Large jaw - prognathism Increased hand and feet size and spade like hands Sweatiness Headache

Question 37

What is the posterior pituitary gland called

Answer 37

Neurohypophysis

Question 38

Hormones associated with the posterior pituitary gland

Answer 38

``` Arginine vasopressin ( AVP)/ ADH Oxytocin ```

Question 39

Why is the posterior pituitary gland anatomically continuous with the hypothalamus

Answer 39

Posterior pituitary gland is made of neuronal tissues and has hypothalamic magnocellular neurons These are long and originate in super optic ( AVP) and paraventricular (oxytocin ) hypothalamic nuclei Nuclei -> stalk -> posterior pituitary

Question 40

Regulation of the posterior pituitary gland

Answer 40

Two sets of hypothalamic neurosecretory cells produce AVP and oxytocin and transport them to the posterior pituitary Excitation of these hypothalamic magnocellular neurones stimulates the release of AVP or oxytocin onto the posterior pituitary where they diffuse into blood capillaries and then leave the posterior pituitary via the b Pod

Question 41

Physiological action of vaspressin

Answer 41

Stimulation of water reabsorption in the renal collecting duct This concentrates the urine Acts through the V2 receptor in the kidney Also a vasoconstrictor ( V1) Stimulates ACTH release from anterior pituitary

Question 42

Actions of oxytocin when delivering baby

Answer 42

Acts on uterus at parturition Causes myometrial cells to contract Delivery of baby Can use oxytocin analogue for women who need biological encouragement to contracts

Question 43

Oxytocin and lactation

Answer 43

Milk ejection is controlled by the posterior pituitary gland Oxytocin acts on breast during lactation Which causes myoepothelial cells to contract Milk ejection

Question 44

Milk ejection reflect arc

Answer 44

Mechanical stimulation of nipple and surrounding area causes afferent pathways Afferent signals integrated in the hypothalamus and stimulate oxytocin releasing neurone activity Action potentials travel down oxytocin neurones and oxytocin is secreted into the bloodstream Incradrf plasma oxytocin increases milk ejection in mammary glands