5.2

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Questions and Answers

What is the main function of the tropic hormones of the anterior pituitary?

To regulate the secretion of growth hormone

To directly regulate physiological processes

To inhibit the production of hormones by the posterior pituitary

To stimulate the production of other hormones (correct)

What is the role of the hypothalamic-hypophysial portal system?

To stimulate the production of hormones by the posterior pituitary

To inhibit the production of hormones by the anterior pituitary

To transport hormones from the hypothalamus to the anterior pituitary (correct)

To regulate the secretion of growth hormone

What is the effect of insulin-like growth factor-1 (IGF-1) on growth hormone secretion?

It has no effect on growth hormone secretion

It increases growth hormone secretion

It only affects growth hormone secretion in children

It decreases growth hormone secretion (correct)

What is the physiological effect of antidiuretic hormone (ADH)?

It decreases urine production Signup and view all the answers

What is the main difference between the anterior and posterior pituitary glands?

The anterior pituitary produces hormones that stimulate other endocrine glands, while the posterior pituitary produces hormones that directly regulate physiological processes Signup and view all the answers

What is the primary function of the hormone produced by lactotropes in the anterior pituitary gland?

Promotion of mammary glands and milk production Signup and view all the answers

What is the name of the bony structure that the pituitary gland resides in?

Sella turcica Signup and view all the answers

What is the term for the hormones produced by the anterior pituitary gland that stimulate other endocrine glands?

Tropic hormones Signup and view all the answers

What is the name of the surgical procedure that removes pituitary tumors through the nose?

Transsphenoidal hypophysectomy Signup and view all the answers

What is the primary role of the hypothalamus in the endocrine system?

To coordinate the endocrine system via multiple mechanisms Signup and view all the answers

What type of hormones does the hypothalamic neurons synthesize?

Antidiuretic hormone and oxytocin Signup and view all the answers

What is the function of the hypothalamic-hypophysial portal system?

To transport regulatory hormones from the hypothalamus to the anterior pituitary Signup and view all the answers

What is the effect of releasing hormones on the anterior pituitary?

They stimulate hormone synthesis and secretion Signup and view all the answers

What is the function of the hypothalamic-pituitary axis?

To regulate the secretion of pituitary hormones and target glands Signup and view all the answers

What is the role of the median eminence in the hypothalamic-pituitary axis?

It is the site where releasing hormones are delivered to the anterior pituitary Signup and view all the answers

What is the difference between short-loop and long-loop feedback in the hypothalamic-pituitary axis?

Short-loop feedback is negative feedback from the pituitary, while long-loop feedback is negative feedback from the target gland Signup and view all the answers

What is the hypothalamic-neurohypophyseal axis responsible for?

Releasing posterior pituitary hormones Signup and view all the answers

What is the function of growth hormone-inhibiting hormone (GHIH)?

To inhibit the release of growth hormone Signup and view all the answers

Which hormone is predominantly under negative control from the hypothalamus?

Prolactin Signup and view all the answers

What is the primary function of Growth Hormone in early development?

To stimulate growth and mark specific developmental phases Signup and view all the answers

Which of the following is a characteristic of the somatotropic axis?

It has a single endocrine target, the liver Signup and view all the answers

What is the primary function of Insulin-Like Growth Factor-1 (IGF-1)?

To stimulate cell division and cell differentiation Signup and view all the answers

What is the result of excessive Growth Hormone secretion before the closure of epiphyses?

Gigantism Signup and view all the answers

What is the effect of Growth Hormone on glucose metabolism?

It promotes lipolysis and increases blood glucose levels Signup and view all the answers

Which of the following is a factor that increases Growth Hormone secretion? (2)

Deep sleep Signup and view all the answers

What is the result of Growth Hormone deficiency in childhood?

Pituitary dwarfism Signup and view all the answers

What is the primary function of Growth Hormone in adults?

To maintain normal blood glucose levels Signup and view all the answers

What is the effect of Insulin-Like Growth Factor-1 (IGF-1) on somatostatin neurons?

It stimulates somatostatin secretion Signup and view all the answers

What is the primary function of antidiuretic hormone (ADH) in the body?

Controlling water balance and promoting vasoconstriction Signup and view all the answers

Where are the peptide pre-hormones neurophysins processed into oxytocin and antidiuretic hormone?

Hypothalamic nuclei Signup and view all the answers

What is the result of a deficiency of antidiuretic hormone (ADH) in the body?

Excretion of large volumes of dilute urine Signup and view all the answers

What is the mechanism of secretion of antidiuretic hormone (ADH) in response to increased osmolality of blood?

Osmoreceptors in the hypothalamus stimulate the release of ADH through the hypothalamo-hypophyseal nerve tract Signup and view all the answers

What is the role of oxytocin in labor?

Potentiating smooth muscle contraction during labor Signup and view all the answers

What is the result of excess antidiuretic hormone (ADH) in the body?

Syndrome of inappropriate secretion of ADH Signup and view all the answers

What is the function of neurophysins in the transport of oxytocin and antidiuretic hormone?

Acting as carrier proteins for oxytocin and ADH Signup and view all the answers

What is the effect of oxytocin on the lactating breast?

Stimulating milk ejection Signup and view all the answers

What is the effect of antidiuretic hormone (ADH) on blood pressure?

Increasing blood pressure through vasoconstriction Signup and view all the answers

Study Notes

Posterior Pituitary Gland and Its Relation to the Hypothalamus

The posterior pituitary gland produces two hormones: ADH (antidiuretic hormone) and OT (oxytocin)
Both hormones are produced in the hypothalamic nuclei, specifically in the supraoptic nucleus (SON) and paraventricular nucleus (PVN)
ADH (arginine vasopressin) controls water balance in the body, concentrates urine, and promotes vasoconstriction
Oxytocin (OT) is a maternal hormone involved in parturition, lactation, and natriuretic peptide, and inhibits salt appetite

Hypothalamic Nuclei

Most cells in the hypothalamic nuclei express ADH or OT, with 2-3% expressing both hormones
The hormones are transported with neurophysins (carrier proteins) to the axon terminals and stored in the posterior pituitary gland
Both hormones are secreted by exocytosis

ADH (Antidiuretic Hormone)

Mechanism of secretion: osmoreceptors in the hypothalamus sense changes in blood osmolality, sending nerve impulses to the posterior pituitary to stimulate ADH secretion
ADH increases fluid retention in the kidneys, promotes vasoconstriction, and stimulates the insertion of aquaporins into the luminal membranes of the connecting tubule and collecting duct cells

Abnormalities of ADH

Deficiency: central diabetes insipidus, characterized by the excretion of large volumes of dilute urine (polyuria)
Excess: nephrogenic diabetes insipidus, characterized by ADH resistance in the kidneys, leading to polyuria

Physiological Effects of Oxytocin

Potentiates smooth muscle contraction during labor, stimulates milk ejection from the lactating breast, and promotes uterine contractions
Stimulates the incorporation of gap junctions between uterine smooth muscle cells

Growth Hormone (GH)

Produced by the anterior pituitary gland, regulates growth and development from infancy to adulthood
Stimulates the liver to produce insulin-like growth factor-1 (IGF-1), which promotes growth and development

The Somatotropic Axis

Regulates the release of GH, which stimulates the liver to produce IGF-1
IGF-1 directly inhibits GH release from the anterior pituitary, creating a negative feedback loop

Negative Feedback Regulation of GH

GH stimulates IGF-1 secretion, which directly inhibits GH release from the anterior pituitary
IGF-1 also indirectly inhibits GH secretion by suppressing GHRH secretion and increasing somatostatin secretion

Insulin-Like Growth Factor-1 (IGF-1) and Body Size

IGF-1 is primarily responsible for the effects of GH on growth and development
Stimulates cell division and differentiation, promoting linear growth in long bones and bone diameter

Stimulation of Growth by GH

GH works directly on specific tissues to produce acute metabolic effects that oppose the effects of insulin
Stimulates cell production, lipolysis, and glucose sparing in various tissues

Age and GH

GH secretion peaks during puberty and declines with aging
Effects on protein synthesis are most apparent in children, while in adults, GH helps maintain normal blood glucose and mobilize lipid stores

GH Secretion

Control of GH secretion is regulated by the hypothalamus, which releases GHRH and somatostatin to stimulate and inhibit GH secretion, respectively
Factors that increase GH secretion include hypoglycemia, increased plasma concentration of amino acids, deep sleep, acute physical stress, and starvation
Factors that decrease GH secretion include hyperglycemia, elevated plasma free fatty acids, aging, obesity, and exogenous GH

Alterations in GH lead to panhypopituitarism, a condition characterized by decreased secretion of all anterior pituitary hormones
Pituitary dwarfism is a result of GH deficiency in childhood, leading to growth cessation and lack of secondary sex characteristics

Alterations in GH lead to gigantism, a condition characterized by excessive growth and height
Acromegaly, a condition characterized by excessive bone growth and soft tissue growth after adolescence, leading to enlarged hands and feet, and soft tissue swelling

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5.2