Neuro-endocrine interactions

Question 1

what is the significance of neurones-endocrine interactions?

Answer 1

Many physiological functions are dually regulated by the nervous and endocrine systems. (e.g. blood pressure)

Question 2

where do the nervous and endocrine systems interact at?

Answer 2

at the hypothalamus and the pituitary gland

Question 3

Describe the pituitary gland (aka hypophysis).

Answer 3

a small endocrine gland located in a bony cavity at the base of the brain just below the hypothalamus

Question 4

what are the two lobes of the pituitary gland ?

Answer 4

• posterior pituitary /neurohypophysis

- anterior pituitary/ adenohypophysis

Question 5

what makes up the two lobes?

Answer 5

• posterior - composed of nervous tissue

- anterior- consist of glandular epithelial tissue

Question 6

When is there an intermediate lobe in humans?

Answer 6

During fatal development -site of release of MSH

Question 7

How does the hypothalamus control the release of hormones from the posterior pituitary?

Answer 7

connects to the hypothalamus by a neural pathway

Question 8

How does the hypothalamus control the release of hormones from the anterior pituitary?

Answer 8

connects to the hypothalamus by a unique vascular link

Question 9

where does the hypothalamus lie?

Answer 9

lies at the base of the brain, just dorsal to the pituitary gland

Question 10

how does the pituitary connect to the base of the brain?

Answer 10

the infundibular stalk

Question 11

what are the 6 hormones released from the anterior pituitary and what are their functions?

Answer 11

-Growth Hormone (GH) - stimulates IGF-1 production

-Adrenocorticotrophic hormone- stimulates adrenal cortex to make corticosteroids
(ACTH, corticotrophin)

-Thyroid stimulating hormone
(TSH) - stimulates thyroid follicular cells to make thyroid hormone

• Prolactin (PRL) - initiates and maintains milk productions
• Luteinizing hormone (LH) - stimulates gonads (leydig cells/testosterone)
• Follicle stimulating hormone (FSH)-stimulates gonads

Question 12

what are the 2 hormones released from posterior pituitary and what are their functions?

Answer 12

• arginine vasopressin (ADH) - promotes water retention

- Oxytocin - stimulates uterus to contract and promotes milk ejection

Question 13

what two peptide hormones are classed as neuro hormones and why?

Answer 13

-Vasopressin and oxytocin - because they are synthesised and secreted by nerve cells

Question 14

where are vasopressin and oxytocin stored?

Answer 14

Stored in vesicles in nerve terminals

Question 15

How is the peptide hormones released?

Answer 15

action potential promotes exocytosis of hormone into the blood-directly released into systemic circulation

Question 16

what lobe stores the hormones and release the hormones?

Answer 16

posterior pituitary does not produce hormones

Question 17

what makes action potentials fire down nerves?

Answer 17

• during dehydration
• increased ECF osmolality
• hypothalamic osmoreceptors
• hypothalamic neurones fire
• posterior pituitary
• increased ADHp
• increased H20 permeability of kidney tubules
• increased H20 reabsorption in kidney
• decreased urine output

Question 18

how are anterior pituitary hormones specialised?

Answer 18

one cell type produces mainly one hormone

Question 19

what are the anterior pituitary cell types and what do they produce?

Answer 19

• Somatotrophs produce growth hormone
• Thyrotrophs produce thyroid stimulating hormone (TSH)
• Corticotrophs produce adrenocorticotrophic hormone (ACTH)
• Gonadotrophs produce FSH and LH
• Lactotrophs produce prolactin

Question 20

what is the specialised blood supply that links hypothalamus directly to anterior pituitary?

Answer 20

hypothalamic- hypophyseal portal system

Question 21

what hormones can stimulate and inhibit secretion?

Answer 21

hypophysiotropic hormones

Question 22

what is the releasing factor and inhibiting factor?

Answer 22

• Growth Hormone Releasing Hormone (GHRH)

- Somatostatin (SS)

Question 23

what is the releasing factor of the thyroid stimulating hormone?

Answer 23

Thyrotrophin releasing hormone (TRH)

Question 24

what is the releasing factor and inhibiting factor of the prolactin (PRL)?

Answer 24

• Prolactin Releasing Factor (PRF)

- Prolactin inhibiting factor (PIF – dopamine)

Question 25

what is the releasing factor of the adrenocorticotrophic hormone hormone (ACTH)?

Answer 25

Corticotrophin Releasing Hormone (CRH)

Question 26

what is the releasing factor of the LH/FSH?

Answer 26

Gonadotrophin Releasing Hormone (GnRH)

Question 27

what can overcome negative feedback of hormone secretion?

Answer 27

CNS via the hypothalamus

Question 28

what are the two types of negative feedback loops can be observed?

Answer 28

Long-loop feedback

Short-loop feedback

Question 29

what is the short feedback loop of hormone secretion?

Answer 29

inhibit hormone 2 by product of hormone 3

Question 30

what is the long feedback loop of hormone secretion?

Answer 30

hormone 3 inbits secretion of hypothalamus

Question 31

what causes leydigs cells to produce testosterone?

Answer 31

LH

Question 32

what cells do FSH stimulate?

Answer 32

Sertoli cells

Question 33

What are the effects of hypophysectomy of the anterior pituitary?

Answer 33

• Growth stops
• Thyroid hormone deficiency (myxoedema)
• Adrenal cortex atrophy (decreased production of cortisol & aldosterone)
• Loss of secondary sexual characteristics (beard, pubic hair)
• Atrophy of gonads
• Increased insulin sensitivity

Question 34

What are the effects of hypophysectomy of the posterior pituitary?

Answer 34

• Dehydration by polyuria, despite pronounced polydipsia
• Diabetes insipidus
• Main reason – deficiency of ADH
• (Little effect of oxytocin loss)