16 - Anatomy of the hypothalamus and pituitary

Question 1

Where is the third ventricle?

Answer 1

In the forebrain, runs anterior-posteriorly along the midline above the midbrain, between the left and right thalamus

Question 2

Where is the hypothalamus located?

Answer 2

The sides of the anterior-most part of the third ventricle

Question 3

Label the thalamus, hypothalamus and pituitary gland on the diagram.

Answer 3

• Google Docs

Question 4

What connects the pituitary gland to the hypothalamus?

Answer 4

Pituitary stalk

Question 5

Label the hypothalamus, third ventricle and optic nerves on the the diagram.

Answer 5

• Google docs

Question 6

What is the hypothalamus sometimes known as?

Answer 6

The control centre for the autonomic nervous system

Question 7

What is the name of the nucleus beneath the 3rd ventricle in the hypothalamus?

Answer 7

Arcuate nucleus

Question 8

Where is the pituitary gland?

Answer 8

In the pituitary fossa in the sphenoid bone, below the hypothalamus

Question 9

What is the infundibulum?

Answer 9

The pituitary stalk - connecting the hypothalamus and pituitary gland

Question 10

What are the 2 outputs from the hypothalamus? Where do they project to?

Answer 10

Magnocellular neurones - Axons project down the pituitary stalk to the posterior lobe of the pituitary, release peptides into the capillaries in the posterior pituitary, these peptides circulate in the blood to other organs
Parvocellular neurones - Shorter axons, release peptides onto a capillary plexus in the neck of the pituitary stalk

Question 11

What is the difference between the anterior and posterior pituitary?

Answer 11

Anterior pituitary - Endocrine gland (Develops from the ectoderm in the roof of the mouth)
Posterior pituitary - Part of the brain

Question 12

What is the cavernous sinus?

Answer 12

A X venous sinus with nerves and the final part of the internal carotid artery running through it

Question 13

What cranial nerves run along the lateral border of the cavernous sinus?

Answer 13

3,4 and 6

Question 14

What are 5 homeostatic systems that the hypothalamus controls?

Answer 14

Temperature, body water, body weight, sleep-walking cycles and reproduction

Question 15

How does the hypothalamus detect changes in temperature?

Answer 15

• Blood temperature from thermoreceptors in the anterior nucleus of the hypothalamus
• Skin temperature from cutaneous thermoreceptors (C fibre endings)

Question 16

What are the effectors if body temperature is too high?

Answer 16

• Sweat glands secrete sweat = heat loss by evaporation
• Cutaneous vasodilation = redirects blood into superficial capillaries = heat loss by convection and conduction
• Inactive = Muscle activity generates heat = increases core temperature

Question 17

What are the effectors if body temperature is too low?

Answer 17

• Sweat stops being produced
• Erector pili muscles attached to hair follicles contract = hair on end = insulating layer = traps heat
• Arterioles carrying blood to superficial capillaries = constrict = blood towards warmer core = prevents blood from losing heat
• Shivering is triggered = increases heat production

Question 18

What are the names of the two nuclei in the hypothalamus that send axons down to the posterior pituitary to regulate water balance?

Answer 18

• Paraventricular nucleus

- Supraoptic nucleus

Question 19

What are the two hormones the posterior pituitary releases?

Answer 19

• Antidiuretic hormone

- Oxytocin

Question 20

What is the function of ADH?

Answer 20

Reduce water loss in urine by increasing water reabsorption in the kidney collecting ducts

Question 21

What is the function of Oxytocin?

Answer 21

• Milk let-down reflex in a lactating mother (neuro-hormonal reflex)
• Contractions of the pregnant uterus during childbirth

Question 22

What is the difference in amino acid sequence between ADH and OXT?

Answer 22

ADH: Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly
OXT: Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly
Both similar as are peptides

Question 23

Why are ADH and OXT found in the posterior pituitary?

Answer 23

Fast release system - to get peptide hormones to site of action ASAP

Question 24

In the anterior lobe of the pituitary, where do the axons with short axons from the hypothalamic nuclei end?

Answer 24

Capillaries in the neck of the pituitary

Question 25

What is the pathway of hormone release from the anterior lobe of the pituitary?

Answer 25

Involves two sets of peptide hormones
- Hypothalamic releasing hormones = released from the hypothalamic axons into the capillaries in the neck region
They travel down the portal vessels where they act on secretory cells in the anterior pituitary
The secretory cells release more peptide hormones into the venous blood leaving the pituitary

Question 26

What are the 6 hormones released from cells in the anterior pituitary?

Answer 26

Adrenocorticotrophic hormone (ACTH), 
Prolactin (PL), 
Lutenising hormone (LH) 
Follicle stimulating hormone FSH), 
Thyroid stimulating hormone (TSH) 
Growth hormone (GH).

Question 27

What are the 6 hypothalamic releasing hormones secreted by hypothalamic axons?

Answer 27

CRH (corticotrophin releasing hormone) releases
Adrenocorticotrophic hormone (ACTH)
GnRH (gonadotrophin releasing hormone) releases both Luteinising Hormone (LH) & Follicle stimulating hormone (FSH)
TRH (thyrotropin releasing hormone) releases Thyroid Stimulating Hormone (TSH) release stimulated by
GHRH (growth hormone releasing hormone) releases Growth Hormone (GH)
GHIH (growth hormone inhibiting hormone: somatostatin) inhibits release of Growth Hormone (GH)
PIF (prolactin inhibiting factor, i.e. dopamine) inhibits Prolactin release

Question 28

Why do we have a double hormone mechanism for releasing anterior pituitary hormones?

Answer 28

This enables dual feedback control for the anterior pituitary hormones
E.g Cortisol inhibits release of CRH from the anterior pituitary and also inhibits the release of the ACTH from the anterior pituitary
Allows anterior hormones to be released in a rhythmic fashion