Neuroendocrinology

Question 1

What do neuroendocrine cells do and where are they found?

Answer 1

Neuroendocrine cells receive neuronal input and secrete hormones in response to that input
Hypothalamus and Pituitary gland

Question 2

Where are parvocellular and magnocellular neurons found?

Answer 2

Hypothalamus

Question 3

Where do parvocellular neurons project to?

Answer 3

Parvocellular neurons –> Hypophyseal system –> Anterior pituitary

Question 4

Where do magnocellular neurons project to?

Answer 4

Posterior pituitary. (Larger neuronal axons than parvocellular neurons so can just project directly to posterior pituitary)

Question 5

From the anterior pituitary and posterior pituitary, where do hormones travel next?

Answer 5

General circulation –> target tissues, adrenal, thyroid, gonads

Question 6

What is the function of the hypothalamus?

Answer 6

Integrates ANS signals and endocrine function with behaviour. Regulates behaviour concerned with basic homeostatic requirements of everyday life

Question 7

What are the three types of processes by which homeostasis can be controlled?

Answer 7

• Behavioural responses​
• Neuronal control through ANS
• Hormonal control via the pituitary gland

Question 8

Give 6 homeostatic functions controlled by the hypothalamus

Answer 8

1) Blood pressure and electrolyte composition - control of drinking and salt appetite and control of blood osmolality and vasomotor tone​
2) Body temperature - metabolic thermoregulation and behaviours like seeking an appropriate environment​
3) Energy metabolism - feeding, digestion, metabolic rate​
4) Reproduction - hormonal control of mating, pregnancy and lactation​
5) Stress response - adrenal stress hormones​
6) Growth - growth hormone

Question 9

What does the paraventricular nucleus control? By secreting which hormones?

Answer 9

Stress (CRH)​
Metabolism (TRH)​
Osmoregulation (ADH)​
Blood pressure (ADH)​
Maternal control (Oxy.)​

Question 10

What does the arcuate nucleus control? By secreting which hormones?

Answer 10

Reproduction (GnRH) ​
Growth (GHRH)​
Lactation (Dopamine)​

Question 11

What does the supraoptic nucleus control? By secreting which hormones?

Answer 11

Osmoregulation (ADH)​
Blood pressure (ADH)​
Maternal control (Oxy.)​

Question 12

Where is the pituitary gland found?

Answer 12

Located in a cavity within the sphenoid bone at the base of the brain called the sella turcica. The pituitary gland is connected to the hypothalamus through the pituitary stalk (infundibulum)

Question 13

Describe some differences between anterior and posterior pituitary

Answer 13

• Anterior develops from pharyngeal epithelium/ Posterior develops from neuronal tissue
• Anterior contains glandular cells/ Posterior contains axon terminals
• Anterior receives signal from parvocellular neurons/ Posterior involves magnocellular neurons
• Anterior responds to factors from portal system/ Posterior does not have portal system

Question 14

What does Corticotropin releasing hormone (CRH) act on?

Answer 14

Acts on corticotrophins in anterior pituitary which then release ACTH which acts on adrenal gland.

Question 15

What does Thyrotropin releasing hormone (TRH) act on?

Answer 15

Acts on thyrotrophs in anterior pituitary which release TSH which acts on thyroid gland

Question 16

What does gonadotropin releasing hormone (GnRH) act on?

Answer 16

Acts on gonadotrophs in the anterior pituitary which then release LH, FSH which act on the gonads

Question 17

What does growth hormone releasing hormone (GHRH) act on?

Answer 17

Somatotrophs in anterior pituitary which then release growth hormone which acts on all tissues

Question 18

What does prolactin inhibiting hormone (dopamine) act on?

Answer 18

Lactotrophs in anterior pituitary which then release prolactin which act on breasts

Question 19

What determines release of growth hormone?

Answer 19

Release of growth hormone is determined by the balance between growth hormone releasing hormone (GHRH) and growth hormone inhibiting hormone (GHIH or somatostatin) received through the portal system

Question 20

What regulates the release of prolactin?

Answer 20

Regulation of prolactin release is through inhibition by dopamine, rather by a releasing hormone​
Prolactin itself enhances dopamine secretion, creating ‘short loop’ negative feedback (i.e. without a downstream hormone as in the three axes)​

Question 21

Describe the cell types found in the posterior pituitary

Answer 21

The posterior pituitary gland contains the unmyelinated axons of magnocellular neurones projecting down from the paraventricular and supraoptic nuclei​.
It also contains astrocyte-like neuroglial cells called pituicytes, with cytoplasmic processes that surround the axons.

Question 22

What hormones are released by the posterior pituitary?

Answer 22

The posterior pituitary gland releases antidiuretic hormone (arginine vasopressin) and oxytocin​.
Both hormones are produced by both hypothalamic nuclei (supraoptic nuclei and paraventricular nuclei) (to some extent), but they are produced by separate cell types​.

Question 23

How are posterior pituitary hormones processed?

Answer 23

Antidiuretic hormone and oxytocin are small peptide hormones synthesised as larger precursors in cell bodies in the hypothalamus​.
These are packaged into vesicles, processed into the mature hormone and bound to carrier proteins called neurophysins​.
The hormone-neurophysin complex is transported along the neuronal axon and temporarily accumulates at Herring bodies​.
The hormone-containing vesicles fuse with the cell membrane in response to action-potential associated Ca2+ influx, releasing the hormone​.
The hormone dissociates from the neurophysin (carrier), which has no further function​.

Question 24

How are posterior pituitary hormones processed?

Answer 24

Antidiuretic hormone and oxytocin are small peptide hormones synthesised as larger precursors in cell bodies in the hypothalamus​.
These are packaged into vesicles, processed into the mature hormone and bound to carrier proteins called neurophysins​.
The hormone-neurophysin complex is transported along the neuronal axon and temporarily accumulates at Herring bodies​.
The hormone-containing vesicles fuse with the cell membrane in response to action-potential associated Ca2+ influx, releasing the hormone​.
The hormone dissociates from the neurophysin (carrier), which has no further function​.