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Anatomy?Physio > Ap hypothalamus > Flashcards

Ap hypothalamus Flashcards

1
Q

what is a hypothalamus

A

Hypothalamus controls the release of hormones from the pituitary

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2
Q

Hormones secreted by hypothalamus

A

ØThyrotropin-releasing hormone (TRH)

ØCorticotropin-releasing hormone (CRH)

ØGonadotropin-releasing hormone (GnRH)

ØGrowth hormone-releasing hormone (GHRH)

ØGrowth hormone-release inhibiting hormone (GHIH) (Somatostatin)

ØDopamine also called - Prolactin-inhibiting hormone (PIH)

Releasing hormones are synthesized in cell bodies of neurons in hypothalamus and delivered to the anterior pituitary via the hypothalamic-hypophysealportal system

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3
Q

Pituitary Gland (Hypophysis) [has anteiror and posterior sides]

what is the hormones secreted by anterior P gland

A

Anterior

Adenohypophysis

Secretes tropic hormones in a pulsatile fashion

True glandular structure

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4
Q

Pituitary Gland (Hypophysis) [has anteiror and posterior sides]

what is the hormone secreted by posterior P gland

A

Neurohypophysis

Extension of nervous tissue from hypothalamus

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5
Q

Describe the primary function of each hormone from posterior pituitary.

A

¢Hormones synthesized in the hypothalamus are transported down the axons to the posterior pituitary – “neuroendocrine secretion”

¢Hormones are stored in vesicles in the posterior pituitary until released into the circulation

¢Principal Hormones:

—Vasopressin

  • Anti diuretic Hormone (ADH)
  • Important role in body water regulation

—Oxytocin

-Acts primarily on the mammary gland and uterus

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6
Q

Describe the primary function of each hormone from anterior pituitary.

A
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7
Q

Negative Feedback Controls

A

Long Loop: Hypoth. and Ant. Pit. (AP) secretions are controlled by negative feedback inhibition by terminal target gland hormones (Primary)

  1. Short Loop: Secretions at pit. and hypo. are controlled by negative feedback by the AP gland hormone

(Secondary)

  1. Ultra short: Secretions at hypo. are controlled by the releasing hormone in a paracrine/autocrine fashion (Tertiary)
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8
Q

Anterior Pituitary Hormones

Pro-opiomelanocortin (POMC) and ACTH

A

—-POMC is the precursor for ACTH and MSH

—-Mutations in POMC gene leads to obesity and adrenal insufficiency

—-Melanocyte Stimulating Hormone (MSH)

—-ACTH triggers the synthesis and secretion of corticosteroids and adrenal androgens

  • ACTH is necessary for the adrenal gland otherwise atrophy of the gland takes place
  • Used in the diagnoses of adrenal insufficiency
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9
Q

Anterior Pituitary Hormones
The Glycoprotein Hormones

A

-TSH

—stimulates synthesis and secretion of the thyroid hormones- thyroxine and triiodothyronine

—chronic TSH stimulation can result in goiter

—TSH serum levels – good diagnostic test for thyroid disorders

-Gonadotropins (FSH and LH)

—pulsatile secretion

—growth and development of ovarian follicles and ovulation in females, sperm production and testosterone secretion in males

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10
Q

Anterior Pituitary Hormones
Growth Hormone

A
  • Positively regulated by GHRH and inhibited by somatostatin (GHIH)
  • Growth-promoting effects in a wide range of tissues
  • Direct effects :[Cartilage ossification}
  • Indirect effects
  • —via insulin like growth factor 1 (IGF-1)
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11
Q

Pulsatile Secretion of Growth Hormone

A

¢Factors that increase GH secretion:

—reduced blood glucose

—protein deficiency

—Deep sleep

—Stress

—Exercise

—GHRH

¢Factors that decrease GH secretion:

—Increased blood glucose

—Increased blood fatty acids

—Obesity

—GHIH

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12
Q

Growth Hormone…..cont’d

A

¢Effects on protein synthesis

—Anabolic effects

—Increases protein synthesis

¢Effects on fatty acid metabolism

—Increases lipolysis

—Anti-insulin effects

¢Effects on carbohydrate metabolism

—Decrease glucose uptake by tissue

—“Diabetogenic effect” (insulin resistance)

¢Effect on growth of bone & cartilage

—Increases conversion of chondrocytes to osteogenic cells

—Promotes growth in length of long bones in childhood

—Promotes thickness of bones in childhood & adulthood

Stimulates action of osteoblasts to deposit bone

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13
Q

Abnormal levels of growth hormone

A

-Elevated GH levels before epiphyseal closure in children – results in gigantism

—This is characterized by a generalized increase in body size with disproportionately long arms and legs.

-If the ↑ levels of GH are present after closure of the epiphyses, patients develop acromegaly

—In this condition, growth is most conspicuous in skin and soft tissues; viscera (thyroid, heart, liver, and adrenals); and bones of the face, hands, and feet.

-Deficiency in growth hormone or defects in its binding to receptor are seen as growth retardation or dwarfism

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14
Q

Anterior Pituitary Hormones
Prolactin

A

¢Primary role - to stimulate breast development and milk synthesis.

¢Prolactin secretion is negatively regulated by the neurotransmitter dopamine from the hypothalamus.

¢Pathologic processes that result in separation of the pituitary gland from the hypothalamus cause loss of all pituitary hormones except prolactin.

¢Loss of dopamine results in an increase in prolactinsecretion from specific anterior pituitary cells now freed of inhibition by dopamine.

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15
Q

explain the most common anterior pituitary disorder?

A

¢Hyperprolactinemia is the most common anterior pituitary disorder

¢Pathologic hyperprolactinemia

  • —prolactin-secreting adenomas (prolactinomas)
  • —primary hypothyroidism
  • —dopamine receptor–blocking drug therapy
  • Physiologic hyperprolactinemia
  • —pregnancy and lactation
  • Roughly 40% of pituitary adenomas found in autopsies are prolactinomas.
  • —Most patients had no symptoms from microadenomas
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16
Q

Posterior Pituitary Hormones
Vasopressin/Antidiuretic Hormone (ADH)

A

Secretion is Stimulated by:

-Large decreases in blood volume

  • —Plasma osmolality is monitored by osmoreceptors in the hypothalamus
  • —Increases in plasma osmolality stimulates secretion of vasopressin
  • Decreased osmolality results in decreased ADH release
  • Decreases in blood pressure
  • Pain, fear, trauma, and stress
17
Q

Vasopressin activity

A

-Decreases water excretion by kidneys

  • —Vasopressin increases the number of active water channels called aquaporins in the cell membranes of renal collecting duct cells, allowing conservation of free water. This increases the concentration of the urine.
  • —The actions of vasopressin on the collecting duct determine the finalosmolarity of the urine
  • Without vasopressin, the collecting duct is relatively impermeable to water
  • Constricts blood vessels - arteriolar smooth muscle
  • Increases ACTH secretion from the anterior pituitary
  • Receptors: V1 and V2 – both GPCR

—V2 receptor – drug target

18
Q

Posterior Pituitary Hormones
Oxytocin

A
  • Acts primarily on the mammary gland and uterus
  • Stimulates contraction of smooth muscle in uterus at end of gestation
  • —Initiates labor & promotes delivery of baby
  • Stimulates release of milk from mammary glands (“lactation”)
  • Increases contraction of smooth muscle of the vas deferens in males
19
Q

Hypothalamic & Pituitary Diseases

A

¢Pituitary Adenomas

¢Hypopituitarism

¢Diabetes Insipidus

¢Obesity

20
Q

Pituitary Adenomas

A

Microadenomas vs. Macroadenomas

  • —Micro – hormone excess, no local mass effect
  • —Macro – in addition to ↑ in hormone, may also impinge on optic chiasm

Prolactinoma (prolactin secreting adenoma)

  • —Most commonly seen pituitary adenoma
  • —Multiple causes

GH – secreting adenoma

  • —Gigantism or acromegaly

ACTH-secreting pituitary adenoma

  • —Most common cause of spontaneous Cushing’s syndrome
21
Q

Hypopituitarism

A

¢Hypopituitarism - loss of one or more pituitary hormones

¢Panhypopituitarism - complete loss of all of the hormones secreted by the pituitary gland

  • —sudden onset due to pituitary trauma
  • —life threatening due to loss of ACTH and ADH
22
Q

Diabetes Insipidus

A

-Syndrome of polyuria due to lack of vasopressin action

-Central diabetes insipidus

  • —Synthesis or secretion of vasopressin is affected
  • —Etiology: diseases of CNS
  • —Only about 15% of the vasopressin-secreting cells of the hypothalamus need to be intact to maintain fluid balance under normal conditions.
  • —Simple destruction of the posterior pituitary does not cause sufficient neuronal loss to result in permanent diabetes insipidus. Rather, destruction of the hypothalamus must also occur.
23
Q

aquaporin channels

A
24
Q

Diabetes Insipidus

¢Nephrogenic Diabetes Insipidus

A

—loss of the kidney’s ability to respond to circulating vasopressin

  • defect in vasopressin receptors or aquaporin-2 water channels
  • ability to form concentrated urine is impaired
  • normal ADH secretory response to changes in plasma osmolality is seen

-Distinguishing central from nephrogenic DI

Determine the responsiveness to injected vasopressin, with a dramatic decrease in urine volume and increase in urine osmolality in the central and little or no change in the nephrogenic

25
Q

Changes in plasma ADH and urine osmolality in patients with nephrogenic diabetes insipidus

A

In central diabetes insipidus, circulating vasopressin levels are low for a given plasma osmolality, whereas in nephrogenic diabetes insipidus, they are high.

26
Q

obesity

A
  • Body mass index (BMI) = weight (in kilograms) divided by height (in meters squared)
  • Obesity is associated with
  • Hypertension
  • Diabetes mellitus
  • Coronary artery disease
  • Sleep apnea
  • Osteoarthritis
  • Stroke
  • Cancer
27
Q

obesity is Controlled by a complex interaction of…

A

anorexigenic and orexigenic hormones that act on the hypothalamus

28
Q

Hormones that inhibit food intake and/or increase metabolism

A

—leptin, POMC and amylin

¢Promote weight loss in the face of excess weight gain

29
Q

Hormones that stimulate appetite and decrease metabolism

A

ghrelin and neuropeptide Y

30
Q

Control of energy homeostasis by orexigenicand anorexigenic peptides

A

Anorexigenic peptides

  • —Hormones that inhibit food intake and/or increase metabolism
  • —Leptin, POMC and amylin
  • Promote weight loss in the face of excess weight gain

Orexigenic peptides

  • —Hormones that stimulate appetite and decrease metabolism
  • —Ghrelin and neuropeptide Y
31
Q

obesity pathophysiology

A
32
Q

obesity health risks

A
  • heart failure
  • hypertension

gallbladder disease

  • renal failure
  • osteoporosis
  • type II dibetes

atherosclerosis

33
Q

Visceral vs. Subcutaneous Adipose Tissue

A

¢Where fat is deposited is more important than how much is deposited

¢Visceral or central obesity (omental fat) an important risk factor for obesity-related morbidity and mortality than subcutaneous (lower body) or peripheral fat.

¢Visceral fat is less sensitive to insulin, making it a marker of insulin resistance.

  • _—_obese individuals who engage in vigorous physical activity and whose obesity is largely due to high caloric intake (eg, sumo wrestlers) have subcutaneous rather than visceral fat and do not demonstrate substantially increased insulin resistance.
  • —obesity associated with a sedentary lifestyle is largely visceral obesity and is associated with a greater degree of insulin resistance
34
Q

Emerging Complexities of Adipocyte Identity

A
35
Q

Strategies for Converting White to Brown Fat: The New Pharmacology (FYI)

A

Current Agents: Thiazolidinediones

Future Agents: Beta agonists; Irisin

Cold Temperature!

PHYTOCHEMICALS ????

36
Q
A

Anatomy?Physio (11 decks)

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