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BIOL 124 > 4 - Mammalian endocrine system I: The hypothalamus and pituitary gland > Flashcards

4 - Mammalian endocrine system I: The hypothalamus and pituitary gland Flashcards

1
Q

What are the endocrine glands?

A
  • Hypothalamus.
  • Pineal gland
  • Pituitary gland.
  • Thyroid gland.
  • Parathyroid gland.
  • Thymus.
  • Adrenal glands.
  • Pancreas.
  • Ovary (female).
  • Testes (male).
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2
Q

What is the Endocrine System?

A

• One of the body’s primary communicating, regulating, and coordinating systems.
• It works in conjunction with other body systems, such as the nervous, hepatic, and renal system.
• It helps to regulate and maintain:
1) Appropriate responses to the external environment, stress, and injury.
2) Body energy.
3) Growth and development.
4) Internal homeostasis.
5) Reproduction.

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3
Q

What are pathologies of the endocrine system?

A
  • In general, when there are pathologies of the endocrine system, there is either hyposecretion or hypersecretion of hormones.
  • The underlying pathology may be of the endocrine gland itself (primary) or from a source outside the gland (secondary).
  • Endocrine hormones affect every body system with a great range of diversity.
  • Skillful assessment of the endocrine system is necessary to detect endocrine disorders
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4
Q

Factors that can result in endocrine dysfunction

A

1) Autoimmune destruction.
2) Benign and malignant tumors.
3) Congenital or genetic defects.
4) Infectious destruction.
5) Surgery.
6) Traumatic injuries.

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5
Q

How do endocrine glands function?

A
  • They secrete their hormones into the interstitial fluid which surrounds these glands.
  • The hormones then diffuse into capillaries and blood carries them to their target tissues.
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6
Q

Exocrine glands

A

• Exocrine glands secrete substances into ducts emptying outside (exo) of the body or into the lumen of an organ

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7
Q

What is the hypothalamus?

A
  • The hypothalamus is a very small structure in the brain that lies above the pituitary gland.
  • It consists of numerous, poorly defined nuclei.
  • It receives input from almost every area of the brain and plays a major role in linking the nervous and endocrine systems.
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8
Q

Functions of the hypothalamus

A

1) Secretion of regulatory hormones to control the activity of the anterior pituitary.
2) Control of sympathetic output to adrenal medullae.
3) Production of ADH & Oxytocin.

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9
Q

How is the pituitary gland formed?

A
  • Two protrusions meet
  • Extension of roof of mouth breaks off and attaches to the extension of the hypothalamus.
  • Bone develops around to protect (sella turcica).
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10
Q

What is the pituitary gland (hypophysis)?

A
  • It’s located at the base of the skull in the sella turcica of the sphenoid bone.
  • The sphenoid bone also separates the pituitary gland from the oral cavity.
  • The hypophysis secretes seven different hormones and is divided into two lobes: posterior and anterior
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11
Q

Posterior pituitary (Neurohypophysis)

A
  • An extension of the hypothalamus.
  • Cell bodies of supraoptic and paraventricular neurosecretory cells release oxytocin & ADH.
  • ADH is a peptide that promotes retention of water by the kidneys and is regulated by a salt/water balance.
  • Oxytocin is a peptide that stimulates contraction of the uterus and mammary gland cells; it’s regulated by the Nervous system.
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12
Q

Anterior pituitary (Adenohypophysis)

A
  • Production and release of the anterior pituitary hormones are regulated by the hypothalamus.
  • Releasing and inhibiting factors are transmitted via the blood to the anterior pituitary: CRH, GnRH,GHRH, PRH, TRH, MSH, GHIH, PIH
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13
Q

Corticotropin-Releasing Hormone (CRH)

A
  • stimulates the secretion of Adrenocorticotropic Hormone (ACTH), which is a peptide that stimulates the adrenal cortex to secrete glucocorticoids; regulated by hypothalamic hormones.
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14
Q

Gonadotropin-Releasing Hormone (GnRH)

A

stimulates the secretion of:

  • Follicle-Stimulating Hormones (FSH) - a glycoprotein that stimulates ova/sperm production
  • Luteinizing Hormone (LH) - a glycoprotein that stimulates ovaries/testes; regulated by hypothalamic hormones.
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15
Q

Growth Hormone­­­-Releasing Hormone (GHRH)

A

stimulates secretion of Human Growth Hormone (GH), which is a protein that stimulates growth (especially bones) and metabolic functions; regulated by hypothalamic hormones

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16
Q

Prolactin-Releasing Hormone (PRH)

A

stimulates secretion of Prolactin (PRL), a peptide that stimulates milk production & secretion; regulated by hypothalamic hormones.

17
Q

Thyrotropin-Releasing Hormone (TRH)

A

stimulates secretion of Thyroid-Stimulating Hormone (TSH), a glycoprotein that stimulates the thyroid; regulated by thyroxine in blood and hypothalamic hormones

18
Q

Melanocyte stimulating hormone (MSH

A

regulates pigment containing cells, e.g. amphibians, fish, reptiles & some mammals; in mammals it acts on neurons to inhibits hunger.

19
Q

Growth Hormone-Inhibiting Hormone (GHIH)

A

suppresses secretion of GH

20
Q

Prolactin-Inhibiting Hormone (PIH

A

suppresses secretion of PRL.

21
Q

How does regulation by the hypothalamus & pituitary generally occur?

A
  • Releasing hormone (RH) causes Hormone 1 release from anterior pituitary.
  • Hormone 1 causes Hormone 2 release from target endocrine organ.
  • Hormone 2 inhibits release of RH and Hormone 1.
  • Hormone 2 has effect upon target cells.
22
Q

What is the circulatory system?

A
  • An organ system that consists of the heart, the blood vessels and the blood.
  • Its function is to transport materials around the body.
23
Q

What is the hypophyseal portal system?

A
  • System of blood vessels in the brain that connects the hypothalamus with the anterior pituitary.
  • Enables communication from the hypothalamus to the anterior pituitary gland.
  • Allows regulatory hormones to be transported from the hypothalamus to the adenohypophysis.
24
Q

How MSH & Ghrelin regulate appetite?

A
  • Corticotroph cells of the anterior pituitary secrete melanocyte-stimulating hormone (MSH).
  • MSH produces melanin, the pigment that gives color to the skin, hair, substantia nigra of the brain, and the choroid of the eye.
  • MSH receptors are present in the brain and influence brain activity.
  • POMC is processed into MSH & released in pars-intermedia to stimulate hypothalamic neurons and reduce appetite.
  • Ghrelin is released by the stomach to stimulate hypothalamic neurons in ARC to increase appetite.
25
Q

What is a tropic hormone?

A

• A hormone that has an endocrine gland as its target and controls the release of other hormones.

26
Q

What is TSH?

A
  • TRH controls release of TSH (a Glycoprotein)
  • TSH stimulates release of T3 and T4 from the thyroid
  • Thyroid hormones T3 and T4, inhibit release of TRH and TSH(negative feedback)
27
Q

Adrenocorticotropic hormone (ACTH)

A
  • ACTH is a peptide
  • CRH causes ACTH release from anterior pituitary
  • ACTH stimulates adrenal cortex to release glucocorticoids
  • Glucocorticoids have negative feedback effect on CRH and ACTH
28
Q

Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH) (gonadotropins)

A
  • FSH and LH are glycoproteins
  • Gonadotropin Releasing Hormone (GnRH) controls FSH and LH production.
  • Promote egg and sperm production and secretion of sex steroids
  • Inhibin inhibits FSH production (both sexes)
  • Inhibin may inhibit GnRH release
29
Q

Prolactin (mammotropin)

A
  • Prolactin is a peptide
  • Prolactin release is stimulated by prolactin releasing factor (PRF) and inhibited by prolactin inhibiting hormone (PIH, dopamine)
  • Stimulates milk production
30
Q

Growth hormone (GH) (somatotropin)

A
  • GH is a peptide
  • GH release stimulated by growth hormone-releasing hormone (GHRH)
  • GH release inhibited by growth hormone-inhibitory hormone (GHIH) (somatostatin)
  • Stimulates somatomedin (Insulinlike Growth Factor - IGF) production
  • Stimulates bone and cartilage growth; fat and glycogen breakdown, increasing blood glucose levels
31
Q

Growth hormone abnormalities

A
  • Pituitary Gigantism – excess GH before puberty
  • Acromegaly – excess GH after puberty
  • Pituitary growth failure – lack of GH
32
Q

Acromegaly

A

excess GH after puberty; bones of hands, feet, cheeks and jaws thicken.

33
Q

Pituitary growth failure

A

lack of GH

34
Q

Nephron function

A
  • ADH binds receptors in the DCT
  • Increases expression of the Aquaporin-2 channel and its insertion in the membrane of DCT cells = Increase in permeability = water retention
35
Q

How does ADH function?

A
  • ADH binds receptors in the DCT
  • This increases the expression of the Aquaporin-2 channel & its insertion in DCT cell membranes.
  • This causes an increase in permeability, which leads to water retention.
36
Q

How does Oxytocin function?

A

• It is a peptide that stimulates milk ejection by mammary glands and uterine contractions during childbirth via:

1) Contraction of the upper part of the uterus and relaxation of the lower part of the uterus.
2) Intermittent contractions. - It targets the brain, influencing behaviour e.g. pair bonding, maternal care and sexual activity.

BIOL 124 (12 decks)

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