Neuroendocrine regulation and pituitary

Question 1

Overview of neuroendocrine regulation

Answer 1

Hypothalamus secretes stimulating factors (on) or inhibiting factors (off) which act on the anterior and posterior pituitary gland
Pituitary gland secretes trophic factors/hormones which act on gonads, thyroid and adrenal. These release primary hormones into circulation that target tissues

Question 2

How does hypothalamus act on the pituitary gland

Answer 2

Synapses with the posterior pituitary gland and releases adh and oxytocin

Causes the anterior pituitary gland (by release of regulatory hormones) to release primary hormones including GH and prolactin (during pregnancy makes mammary glands develop milk ducts)
The anterior pituitary gland targets endocrine glands

Question 3

Where is the hypothalamus located

Answer 3

at the base brain

Question 4

What does the hypothalamus use the pituitary gland as

Answer 4

output organ

Question 5

Hypo to posterior

Answer 5

Hypothalamus has modified neurosecretory cells, modified nerve endings which release ADH directly into circulation and act on the posterior pituitary gland

Question 6

Hypo to anterior and

Answer 6

Hypo releases trophic hormone into median eminence and the Hypothalamo-pituitary portal vessel to anterior pituitary
Blood flow 1 direction, only hypo signals to anterior pituitary
Means small amounts of hormone needed to bring about response in anterior
Anterior v vascularised- easily secrete hormones into blood

Question 7

Hypothalamic nuclei

Answer 7

have diverse functions
Areas for neuroendocrine control: 
paraventricular nucleus (oxytocin release- lactation) 
Supraoptic (vasopressin/release)
Arcuate nucleus and periventricular zone (neuroendocrine control)

Question 8

Cells in the periventricular zone

Answer 8

They are suprachiasmatic neurones- receive retinal innervation and synchronize circadian rhythms (based on daylight). Light/dark cycle drives neuroendocrine signals

Send output to sympathetic and parasympathetic output neurones in spinal cord to control activity of ANS

Question 9

Neurosecretory cells

Answer 9

responsible for release of regulatory hormones to control pituitary gland

Question 10

Hypo regulatory hormones: releasing/stimulating factors

Answer 10

CRF- corticotropin releasing factors
TRH- thyrotropin releasing hormone
GHRH- growth hormone releasing hormone
GnRH- gonadotropin releasing hormone
PRF- prolactin releasing factor

Question 11

Hypo regulatory hormones: Inhibiting factors

Answer 11

GHIH- growth hormone inhibiting hormone
PIH- prolactin inhibiting hormone
MSH-IH- melanocyte stimulating hormone inhibiting hormone

Question 12

Anatomy of pituitary gland

Answer 12

Different sorts of tissues
Pars nervosa- posterior, nerve like
Pars distalis- anterior, has secretory vesicles with hormones
Pars intermedia in the middle, has neither anterior nor posterior, releases MSH

Question 13

Anterior pituitary hormones, four trophic hormones

Answer 13

Thyroid Stimulating hormone
AdrenoCorticoTrophic Hormone
Follicle Stimulating Hormone
Lutenizing hormone

Question 14

Anterior pituitary hormones: two primary hormones

Answer 14

Growth Hormone
PRoLactin

caps intentional

Question 15

GnRH from hypo triggers release of

Answer 15

LH, FSH from pituitary

Which acts on testes, ovary

Question 16

TRH

Answer 16

TSH

Thyroid

Question 17

CRF

Answer 17

ACTH

adrenal

Question 18

GHRH

Answer 18

GH (somatotropin)

multiple tissues

Question 19

SRIF

Answer 19

GH

multiple tissues

Question 20

PRF and PIH

Answer 20

Prolactin

Breast

Question 21

Negative feedback control

Answer 21

In loops

Hormone released from endocrine gland switches off its own production and feeds back onto anterior pituitary- inhibits release of pituitary hormones

Pituitary hormones feed back onto anterior pituitary and hypothalamus to switch off production of hormones

hypo- releasing hormone- AP-Pituitary hormone- endocrine gland- hormone

Question 22

Effects of growth hormone (somatotropin,/somatotrophin)

Answer 22

Incr cell size, number and differentiation
Stimulate proteinsynthesis
incr bone growth
Stimulate fat utilization (breakdown)
Alter carbohydrate metabolism (growth requires energy, release of glucose)

Question 23

GH main role

Answer 23

Regulator of post natal growth

Question 24

GH acts at … and how?

Answer 24

receptor tyrosine kinase

Binds, triggers phosphorylation of TK residues inside the cell, activates kinase cascade (activation of MAP kinases etc)

Question 25

Effects of GH on proteinsynthesis

Answer 25

First GH acts on liver to bring about production of somatomedins (insulin-like growth factors) GH and somatmedins act on the nucleus to incr transcription, and acts on ribosomes to incr translation. They also incr uptake of amino acids via transporters into the cell- building blocks Overall incr PS

Question 26

Somatomedins

Answer 26

small proteins produced by the liver in response to GH At least 4 produced- somatomedin C most important Long half life vs GH (20h vs <20 mins)

Question 27

GH released in response to

Answer 27

GHRH

Question 28

Release of GH decr by

Answer 28

GHIH or somatostatin

Question 29

GH secretion control

Answer 29

GHIH and GHRH released from ventromedial hypothalamus | GH regulated by short feedback loop

Question 30

What factors is GH controlled by

Answer 30

sleep, exercise, stress

Question 31

somatomedins feed back onto

Answer 31

GHIH production positively | GHRH production negatively

Question 32

Deficit of GH

Answer 32

dwarfism, may be: - anterior pituitary dysfunction - GH deficit - normal GH by hereditary somatomedin deficit Accelerated ageing- loss of GH after adolescence - decr PS

Question 33

Excess GH

Answer 33

Gigantism- early life pituitary tumour | Acromegaly- pituitary tumour after adolescence

Question 34

Acromegaly

Answer 34

``` excess production GH Most affects middle aged Premature death Slow onset so freq incorrectly diagnosed Most common symptoms are abnormal growth of hands and feet ```

Question 35

Acromegaly: treatment

Answer 35

Aim to reduce GH production: - surgical removal of tumour drug therapy: octrotide and lanreotide (somatostatin analogues), bromocriptine -Radiation therapy

Question 36

Daily Pattern of GH release

Answer 36

Surge overnight | Shows circadian rhythm

Question 37

GH secretion is episodic

Answer 37

in bursts surge at birth, puberty Stable at adulthood Decline in old age

Question 38

insulin induced hypoglycaemia

Answer 38

stimulated GH secretion decr glucose, FAs, AAs Incr GH