Mod8-Obj3: Hypothalamus & Pituitary Gland

Question 1

Hypothalamus

Answer 1

Overseas the regulation of both the nervous and endocrine systems.

• Integrates the activities of both the nervous and endocrine systems in three ways
  1. ) Acts as an endocrine organ
  2. ) Secretes regulatory hormones
  3. ) Contains autonomic centres

Question 2

1.) The hypothalamus acts as an endocrine organ

Answer 2

Acts as an endocrine organ producing the hormones oxytocin and antidiuretic hormone (ADH). These two hormones are transported from the hypothalamus to the posterior pituitary where they are secreted into the blood

Question 3

2.) The hypothalamus secretes regulatory hormones

Answer 3

Secretes regulatory hormones that act on the anterior lobe of the pituitary stimulating it to produce and secrete its own hormones into the blood, to act on distant target cells

Question 4

3.) The hypothalamus contains autonomic centres

Answer 4

Contains autonomic centres that exert direct neural control on the adrenal cortex and reproductive organs stimulating them to release their own hormones

Question 5

The pituitary gland

Answer 5

The pituitary gland (hypophysis) is located at the base of the brain, belove the hypothalamus. The stalk, connects the hypothalamus to the pituitary gland. The pituitary gland has two lobes (anterior and posterior)

Question 6

Anterior pituitary (adenohypophysis)

Answer 6

The anterior pituitary is comprised of endocrine cells that produce and secrete hormones into the circulation in response to releasing hormones secreted from the hypothalamus

Question 7

Posterior pituitary (neurohypophysis)

Answer 7

The posterior pituirary is made up of neurons that originate in the hypothalamus and project via the pituitary stalk into the posterior pituitary.

• Contains no hormone producing cells
• It secretes neuro-hormones, produced in the hypothalamus, from nerve endings, into the circulation.
• Technically not an endocrine gland

Question 8

Posterior pituitary-hypthalamic relationship

Answer 8

The posterior pituitary is an outgrowth of the hypothalamus and is composed of neural tissue. It maintains a neural connection with the hypothalamus via a nerve bundle called the hypothalamic-hypophyseal tract.

Question 9

hypothalamic-hypophyseal tract

Answer 9

The cell bodies of the neurons originate in the hypothalamus and their axons project down through the pituitary stalk and terminate in the posterior pituitary where they can release hormones into the blood

Question 10

Hormone secretion from the posterior pituitary

Answer 10

Hormones of the posterior pituitary are produced and packaged into vesicles in the hypothalamus. Vesicles are transported down through the axons (hypothalamic-hypophyseal tract) to the posterior pituitary, where they are stored in the axon terminals, until and action potential, allows it to be secreted into the blood

Question 11

The posterior pituitary secretes two hormones into the blood stream…

Answer 11

1. ) Antidiuretic hormone (ADH)
2. ) Oxytocin

Question 12

Hormone secretion from the anterior pituitary

Answer 12

The release of hormones from the anterior pituitary is regulated by hypothalamic releasing hormones.

• Hypothalamic releasing hormones are produced in neurons in the hypothalamus and are released into the hypophyseal portal system (vascular connection) and travel down the anterior pituitary.
• Once at the anterior pituitary, the hypothalamic releasing hormones directly affect the secretion of the hormone from the endocrine cells in the anterior pituitary

Question 13

Hypothalamic releasing hormones that act on the anterior pituitary

Answer 13

(TSH – thyroid stimulating hormone, ACTH – adrenocorticotropic hormone, GH – growth hormone)

Question 14

Hypothalamic releasing hormones that act on the anterior pituitary:

Gonatotropin-releasing hormone (GnRH)

Answer 14

Stimulates LH and FSH secretion

Question 15

Hypothalamic releasing hormone: Thyrotrophin-releasing hormone (TRH)

Answer 15

Stimulates TSH (thyroid stimulating hormone) secretion

Question 16

Hypothalamic releasing hormone: Corticotopin-releasing hormone (GHRH)

Answer 16

Stimulates ACTH (adrenocorticotrophic hormone) secretion

Question 17

Hypothalamic releasing hormone: Growth hormone-releasing Hormone (GHRH)

Answer 17

Stimulates GH (growth hormone) secretion

Question 18

Hypothalamic releasing hormone: Somastostatin (SS)

Answer 18

Inhibits GH (growth hormone) secretion

Question 19

Hypothalamic releasing hormone: Dopamine (DA)

Answer 19

Inhibits Prolactin secretion

Question 20

Hypothalamic release-inhibiting hormones

Answer 20

Prevents the release of a hormone. This is important in processes such as growth (GH) and milk production (prolactin) to ensure that they occur at the correct stage of life and not all the time.

Question 21

Releasing hormones

Answer 21

Hormones whose primary function is to control the release of other hormones secreted by the hypothalamus. Then shows how they affect the release of hormones from the anterior pituitary, where those hormones act.

(+ indicates the releasing hormone increases the release of the anterior pituitary hormone)

(- indicates a decrease)

Question 22

Hypothalamic-Pituitary Axis

Answer 22

The hypothalamus releases a releasing hormone which acts on endocrine cells of the anterior pituitary.

The anterior pituitary releases Hormone 1, which travels through the bloodstream, acting on the endocrine gland.

The endocrine gland responds by releasing hormone 2.

• Negative feedback results in decreased synthesis and secretion of the releasing hormone from the hypothalamus
• Negative feedback can also make the anterior pituitary gland less responsive to releasing hormones, with the net effect of a reduction in the secretion of hormone 1

Question 23

Summary of anterior pituitary regulation

Answer 23

1. ) Releasing hormones (and release inhibitinf hormones) from the hypothalamus
2. ) Negative feedback (mostly) from target organs or glands