Neuroendocrinology

Question 1

What is the definition of a hormone?

Answer 1

→ a cell secretes a hormone
→ not targeted
→ has an effect on target cells depending on whether they have the receptor or not

Question 2

How do neurotransmitters work?

Answer 2

→ nerve cell secretes NTs
→ across a spatially restricted area
→ acts on an effector cell

Question 3

What is paracrine secretions?

Answer 3

→ secreted from cells

→ exerts effects at local interstitial fluid

Question 4

What is autocrine signalling?

Answer 4

→ The cell has receptors for a hormone that it secretes

Question 5

What are neuroendocrine cells?

Answer 5

→ neurosecretory cells that release signal molecules from their synaptic terminals into the blood

Question 6

What are neuroendocrine cells controlled by?

Answer 6

→ synaptic transmission from presynaptic neurons

Question 7

What are 3 examples of neuroendocrine cells?

Answer 7

→ chromaffin cells of adrenal medulla
→ hypothalamic magnocellular neurons
→ hypothalamic parvocellular neurons

Question 8

How does neuroendocrine transmission work?

Answer 8

→ Nerve cell releases NT
→ NT acts on a neuroendocrine cell
→ Releases a signalling molecule from axonal end
→ it doesn’t synapse
→ terminals target capillaries
→ substance diffuses and acts as a hormone

Question 9

What is the pituitary made from?

Answer 9

→ 2 independent structures

Question 10

How does the pituitary form in the embryo?

Answer 10

→ Evagination of the floor of 3rd ventricle
→ Evagination of oral ectoderm
→ Rathkes pouch pinched off

Question 11

What is the posterior lobe of the pituitary an extension of?

Answer 11

→ The hypothalamus

Question 12

What are the two nuclei of the hypothalamus?

Answer 12

→ Parvocellular nuclei

→ Magnocellular nuclei

Question 13

Where do the parvocellular nuclei project to?

Answer 13

→ small neurons with small axons
→ project to the median emininence
→ release hormones to the capillary network
→ carried by hypophyseal portal veins
→ to anterior pituitary

Question 14

What is the posterior pituitary supplied and drained by?

Answer 14

→ Inferior hypophyseal artery

→ Inferior hypophyseal vein

Question 15

What is the anterior pituitary supplied and drained by?

Answer 15

→ Superior hypophyseal artery
→ forms a network at the base of the hypothalamus
→ Portal veins - a second capillary network

Question 16

Where do the magnocellular nuclei project ?

Answer 16

→ Project to the posterior pituitary

→ release capillaries supplied by inferior hypophyseal artery

Question 17

What is the pathway of ADH?

Answer 17

→ Synthesized in the magnocellular nuclei
→ packaged into vesicles and transported along the axons
→ stored in axon terminals
→ released into the hypophyseal capillaries

Question 18

What kind of hormones do the parvocellular nuclei release?

Answer 18

Trophic hormones

→ Hormone releasing hormones

Question 19

What hormones does the posterior pituitary release?

Answer 19

→ Oxytocin

→ ADH

Question 20

What hormones does the anterior pituitary release?

Answer 20

→ TSH
→ ACTH
→ FSH + LH
→ Growth hormone
→ Prolactin
→ Endorphins

Question 21

How does ADH get regulated?

Answer 21

→ Sensory neurons in the hypothalamus detect changes in ECF osmolality
→ passed on to magnocellular neurons (supraoptic)
→ increase or decrease in firing of magnocellular neurons
→ + or - in the release of ADH into the posterior pituitary

Question 22

Describe the cascade of TRH

Answer 22

→ Hypothalamic hormone TRH
→ changed into TSH in the anterior pituitary
→ stimulates thyroid
→ thyroid produces thyroid hormones

Question 23

Where are the parvocellular and magnocellular nuclei found?

Answer 23

→ in the hypothalamus

Question 24

What is the brain dependent on?

Answer 24

→ obligatory dependent on glucose

Question 25

In the absence of circulating glucose where does glucose come from?

Answer 25

→ glycogen stores

Question 26

When glycogen runs out where does glucose come from?

Answer 26

→ Gluconeogenesis

Question 27

What does growth hormone stimulate?

Answer 27

→ Lipolysis → Promotes release of fatty acids → so tissues use fat → glucose can be used in the brain

Question 28

What are the 7 factors that stimulate growth hormone?

Answer 28

``` → GHRH → Ghrelin- secreted by endocrine cells of the stomach → Hypoglycaemia → Decreased fatty acids → Fasting → Exercise, sleep highest at night → stress ```

Question 29

What is ghrelin and where is it released from?

Answer 29

→ Hunger hormone | → Released by endocrine cells of the stomach

Question 30

What are the 5 factors that inhibit growth hormone?

Answer 30

→ Somatostatin , from hypothalamic parvocellular neuroendocrine cells → GH → Hyperglycemia → Increased fatty acids → IGF-1- released by liver in response to GH

Question 31

What are somatotropes?

Answer 31

→ endocrine cells in the anterior pituitary that secrete GH

Question 32

How does IGF get produced?

Answer 32

→ GH released from somatotropes → GH acts on liver and increases gluconeogenesis → Increases IGF

Question 33

What does IGF from the liver promote?

Answer 33

→ Increase somatic cell growth → Increase chondrocyte function (cartilage in bones) → Increase bone modelling

Question 34

What does GH do in the muscle?

Answer 34

→ Increases protein synthesis

Question 35

What does GH do in adipose tissue?

Answer 35

→ Promotes lipolysis so does fat can be used for energy and glucose can be stored and used for the brain Muscle protein is not then needed for gluconeogenesis.

Question 36

What are GH concentrations like during life?

Answer 36

→ birth is low → increases and stays constant at childhood → Increases dramatically during puberty → decline during adult life and old age

Question 37

What does GH deficiency during childhood result in?

Answer 37

→ dwarfism

Question 38

What is the condition with excess hormone called?

Answer 38

→ Acromegaly

Question 39

What is acromegaly caused by?

Answer 39

→ pituitary adenoma

Question 40

What are metabolic effects of acromegaly?

Answer 40

→ Insulin resistance → Impaired glucose tolerance and hyperinsulinemia →dyslipidaemia →hypertriglyceridemia due to inhibition of lipoprotein lipase

Question 41

What doe supraoptic nucleus contain?

Answer 41

magnocellular neurones

Question 42

Where does oxytocin and vasopressin release into?

Answer 42

hypophysial capillaries, inferior hypophysial vein

Question 43

Where do the cell bodies of oxytocin cells lie?

Answer 43

mainly in the supraoptic and paraventricular in the hypothalamus

Question 44

Where is the anterior part derived from?

Answer 44

up growth from the oral ectoderm of the primitive oral cavity called Rathke's pouch

Question 45

Where is the origin of the posterior part of the pituitary?

Answer 45

→origins in nervous tissue. | →It is formed from a downgrowth of the diencephalon that forms the floor of the third ventricle.

Question 46

What is the difference between GH levels in older adults and younger adults?

Answer 46

Older adults have much smaller levels than young adults