The pituitary gland

Question 1

What are the 2 principal organisers of the endocrine system?

Answer 1

hypothalamus

pituitary

Question 2

What are chemicals called that are released into the blood by the hypothalamus?

Answer 2

neurohormones as the hypothalamus is made up of neural tissue

Question 3

What is the stalk called that connect the hypothalamus to the pituitary?

Answer 3

Infundibulum

Question 4

Where do hypothalamic axons and nerve terminals project to and from?

Answer 4

The posterior pituitary

Question 5

Connection between the anterior pituitary and the hypothalamus is via what?

Answer 5

neurohormones via capillary portal system

Question 6

What type of tissue is the anterior pituitary made up of

Answer 6

Endocrine tissue of epithelial origin

Question 7

What type of tissue is the posterior pituitary made up of

Answer 7

it is an extension of the neural tissue

Question 8

What lies between the anterior and posterior pituitary releasing melanin?

Answer 8

Pars intermedia

Question 9

What sorts of stimuli does the hypothalamus respond to? (11)

Answer 9

cold
stress
metabolic demand
hydration status
exercise
day/night
menstrual cycle
sleep
breastfeeding 
pregnancy
puberty

Question 10

What types of hormones do the hypothalamus and the anterior pituitary release?

Answer 10

tropic and non-tropic hormones

Question 11

What is a tropic hormone?

Answer 11

One that governs the release of another hormone - so the tropic hormone travels elsewhere and turns another hormone on/off

Question 12

What is a non-tropic hormone

Answer 12

A hormone that travels straight to target tissue to elicit a response - there is no intermediate hormone

Question 13

What types of hormones does the anterior pituitary release?

Answer 13

Classic endocrine hormones

Question 14

Hypothalamus: tropic and non-tropic hormone functions

Answer 14

Non-tropic – neurohormones produced in the hypothalamus and travel to posterior pituitary (via axons of hypothalamic neurons) where they are released into blood.

Tropic – neurohormones secreted into capillaries travelling to anterior pituitary. Govern release of anterior pituitary hormones

Question 15

What are magnocellular neurons?

Answer 15

Neurons that have their cell bodies in the hypothalamus.

They are within the posterior pituitary however - once the hormones are synthesised in the hypothalamus they are transported to nerve terminal in post. pituitary where they are stored until needed

the terminals end directly on capillaries

Question 16

Which peptide neurohormones do magnocellular neurons release

Answer 16

Vasopressin i.e ADH
Oxytocin

different subsets of neurons make either vasopressin or oxytocin

Question 17

What is the function of vasopressin?

Answer 17

maintains water balance

Question 18

What is the function of Oxytocin? (2)

Answer 18

Stimulates uterine contraction at birth

Aids expression of milk in lactating breast

Question 19

All hypothalamic neurohormones acting on anterior pituitary cells are of what type?

Answer 19

tropic hormones, i.e. stimulate/inhibit release of AP hormones

Question 20

What are the 5 hypothalamic ‘releasing hormones’ ie when they reach anterior pituitary they stimulate the release of another hormone

Answer 20

Thyrotropin Releasing Hormone (TRH)

Corticotropin Releasing Hormone (CRH)

Growth Hormone Releasing Hormone (GHRH)

Gonadotropin 
Releasing Hormone (GnRH)

Prolactin Releasing Hormone (PRH)

Question 21

What are the 2 hypothalamic ‘inhibiting hormones’ in the anterior pituitary

ie when they reach anterior pituitary they inhibit the release of another hormone

Answer 21

Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin

Dopamine aka Prolactin Inhibiting Hormone (PIH) (amine not peptide)

Question 22

What is the median eminence?

Answer 22

1st capillary bed that collects the trophic hormone from the hypothalamus

Question 23

Where is the 2nd capillary bed?

Answer 23

within the anterior pituitary

Question 24

What is the hypothalamo-hypophyseal portal system?

Answer 24

Network of tiny vessels which transfer trophic hormones from hypothalamus to anterior pituitary - 2 capillary beds connected in series

Question 25

What is the production of anterior pituitary hormones controlled by?

Answer 25

the hypothalamic “releasing” or “inhibiting” trophic hormones

Question 26

What are the 6 hormones released from the anterior pituitary if stimulated?

Answer 26

Thyroid Stimulating Hormone (TSH) aka thyrotropin

Adrenocorticotrophic Hormone (ACTH) aka corticotropin

Follicle Stimulating Hormone (FSH)

Luteinising Hormone (LH)

Growth Hormone (GH)

Prolactin

All but prolactin are tropic hormones (targets are in distal areas) Prolactin directly stimulates milk production from the breast during lactation.

Question 27

Why is growth hormone produced throughout life even after we have stopped growing?

Answer 27

For the general repair of tissue

Question 28

In anterior pituitary feedback control what are the 3 integration centres

Answer 28

hypothalamus
anterior pituitary
target endocrine cell

Question 29

What act as the negative feedback signal?

Answer 29

hormones themselves

Question 30

Describe a long-loop feedback

Answer 30

feedback from endocrine target

end endocrine target hormone feeds back and inhibits activity in hypothalamus and anterior pituitary

Question 31

Describe a short-loop feedback

Answer 31

feedback from anterior pituitary to hypothalamus

Question 32

Result of hormone disorders (4)

Answer 32

hyposecretion: too little hormone secreted
hypersecretion: too much hormone secreted

Hyporesponsiveness relates to alterations in receptor for hormone, disordered post-receptor events, failure of metabolic activation of hormone, (where this is required for function) or antagonistic effects.

Hyperresponsiveness: could be due to permissive effects e.g. Thyroid hormone and adrenaline. Thyroid hormone causes increase in response of our tissues to adrenaline.

Question 33

Primary disorders

Answer 33

those in which the defect is in the cells that secrete the hormone (e.g end endocrine gland – generally most common)

Question 34

Secondary disorders

Answer 34

those in which there is too little or too much tropic hormone from pituitary

Question 35

Tertiary disorders

Answer 35

relate to hypothalamic defects - much less common

Question 36

What homeostatic responses are initiated to reduce impact on end function when normal plasma hormone concentration is disrupted?

Answer 36

Prolonged exposure to low [hormone] in plasma often leads to up-regulation of receptor number (increases tissue sensitivity/response to hormone).

Conversely, prolonged exposure to high [hormone] in plasma typically leads a decrease in the number of receptors on the surface of target cells (decreases tissue sensitivity/response to that hormone).

Question 37

Define the term permissive effects

Answer 37

the presence of one hormone enhances the effect of another

best example is adrenaline and thyroid hormone - thyroid hormone increases expression of adrenaline (epinephrine) receptors on adipocytes. Thyroid itself has no effect on lypolysis but affects adrenaline which affects lypolysis

Question 38

Give an example of antagonistic effects

Answer 38

growth hormone impairs glucose uptake in response to insulin by decreasing the number of insulin receptors on muscle and adipose tissue