Pituitary Gland and Hypothalamus Function
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Questions and Answers

What is the primary function of the hormones secreted by the anterior lobe of the pituitary gland?

  • Regulate the secretion of ADH and oxytocin from the posterior pituitary.
  • Directly regulate blood pressure by controlling ADH secretion.
  • Stimulate the release of epinephrine and norepinephrine from the adrenal medulla.
  • Control the activity of other endocrine organs. (correct)

Which of the following structures is directly controlled by the hypothalamus?

  • Anterior lobe of the pituitary gland (correct)
  • Adrenal medulla
  • Pars intermedia
  • Adrenal cortex

If the connection between the hypothalamus and the posterior pituitary gland is severed, which of the following would be directly affected?

  • Secretion of epinephrine from the adrenal medulla
  • Activity of the adrenal cortex
  • Release of ADH and oxytocin (correct)
  • Production of hormones by the anterior pituitary gland

What is the hypothalamic control mechanism over the adrenal medulla?

<p>Preganglionic motor fibers directly stimulate the adrenal medulla (B)</p> Signup and view all the answers

What primarily governs the rate of hormone secretion in the anterior pituitary lobe?

<p>Negative feedback mechanisms. (D)</p> Signup and view all the answers

How does the hypothalamus regulate the anterior pituitary gland?

<p>By secreting regulatory hormones into the hypophyseal portal system. (D)</p> Signup and view all the answers

How do releasing hormones (RH) from the hypothalamus affect the anterior pituitary?

<p>They stimulate the synthesis and secretion of one or more hormones. (D)</p> Signup and view all the answers

Which region of the pituitary gland is also known as the adenohypophysis?

<p>Anterior lobe (B)</p> Signup and view all the answers

What would be the expected outcome of damage to the preganglionic motor fibers that innervate the adrenal medulla?

<p>Decreased secretion of epinephrine and norepinephrine. (A)</p> Signup and view all the answers

What is the role of hypophyseal veins in the context of the pituitary gland?

<p>They carry hormones synthesized in the pituitary to the cardiovascular system. (C)</p> Signup and view all the answers

If a patient has a tumor that is constantly secreting an inhibiting hormone (IH) targeting the anterior pituitary, what would be the expected outcome?

<p>Decreased hormone production in the anterior pituitary. (B)</p> Signup and view all the answers

Which of the following lists includes structures that are all part of the anterior lobe of the pituitary gland?

<p>Pars distalis, pars intermedia, and pars tuberalis (C)</p> Signup and view all the answers

Which of the following best describes the interaction between the hypothalamus and the anterior pituitary gland?

<p>The hypothalamus uses releasing and inhibiting hormones to control the anterior pituitary. (D)</p> Signup and view all the answers

In males, what is the primary effect of luteinizing hormone (LH)?

<p>Stimulating the production of androgens. (C)</p> Signup and view all the answers

What directly stimulates the production of FSH and LH?

<p>Gonadotropin-releasing hormone (GnRH) (A)</p> Signup and view all the answers

Which of the following conditions is caused by low production of gonadotropins?

<p>Hypogonadism (D)</p> Signup and view all the answers

How does the hypothalamus communicate with the anterior pituitary gland to control hormone release?

<p>The hypophyseal portal system (B)</p> Signup and view all the answers

Which pituitary hormone primarily targets the adrenal cortex?

<p>ACTH (Adrenocorticotropic hormone) (D)</p> Signup and view all the answers

What is the role of somatomedins, which are stimulated by GH (Growth Hormone)?

<p>To promote growth in bone, muscle, and other tissues (C)</p> Signup and view all the answers

Which of the following hormones, produced by the anterior pituitary, has uncertain significance in healthy adults?

<p>MSH (Melanocyte-stimulating hormone) (C)</p> Signup and view all the answers

What is the primary effect of thyroid hormones (T3, T4) on the body?

<p>Regulating metabolic rate and growth. (A)</p> Signup and view all the answers

What is the role of inhibin in hormonal regulation?

<p>To inhibit FSH production. (A)</p> Signup and view all the answers

Which hormones are directly controlled by the nervous system via the adrenal medulla?

<p>Epinephrine and norepinephrine (C)</p> Signup and view all the answers

Prolactin (PRL) production by the anterior lobe is unique because it involves:

<p>Regulation by both a releasing hormone (PRH) and an inhibiting hormone (PIH) from the hypothalamus. (D)</p> Signup and view all the answers

If the hypothalamus is stimulated to release PRH, what corresponding change would likely occur with PIH?

<p>PIH release would be inhibited to prevent overstimulation of mammary glands. (B)</p> Signup and view all the answers

How do somatomedins, released by liver cells due to growth hormone stimulation, affect skeletal muscle fibers?

<p>They cause skeletal muscle fibers to increase uptake of amino acids. (C)</p> Signup and view all the answers

Which of the following is NOT a direct effect of growth hormone (GH)?

<p>Increase in insulin production by the pancreas. (C)</p> Signup and view all the answers

The diabetogenic effect of growth hormone is related to:

<p>Breakdown of glycogen by liver cells, increasing blood sugar levels. (D)</p> Signup and view all the answers

How does the regulation of growth hormone (GH) differ from that of prolactin (PRL)?

<p>GH is regulated by both releasing (GH–RH) and inhibiting (GH–IH) hormones, while PRL is regulated by both releasing (PRH) and inhibiting (PIH) hormones. (B)</p> Signup and view all the answers

What is the 'glucose-sparing effect' of growth hormone?

<p>Shift in energy source from glucose to fatty acids through breakdown of triglycerides. (C)</p> Signup and view all the answers

If GH-IH release is stimulated, what effect does this have on GH-RH release?

<p>GH-RH release will be inhibited, reducing overall GH production. (B)</p> Signup and view all the answers

What physiological effect would you expect to observe in an individual with a tumor that excessively secretes melanocyte-stimulating hormone (MSH)?

<p>Increased melanin production leading to darker skin pigmentation. (D)</p> Signup and view all the answers

How does the release of somatomedins from the liver contribute to the regulation of growth?

<p>They inhibit the release of growth hormone (GH) from the anterior pituitary via negative feedback. (B)</p> Signup and view all the answers

Which of the following best describes the interaction between growth hormone (GH) and somatomedins in stimulating tissue growth?

<p>GH stimulates the liver to produce somatomedins, which then promote the growth of cartilage, skeletal muscle, and other tissues. (B)</p> Signup and view all the answers

A patient is diagnosed with a lesion affecting the supra-optic nuclei of the hypothalamus. Which of the following hormonal imbalances is most likely to occur as a direct result?

<p>Deficient production of antidiuretic hormone (ADH) leading to diabetes insipidus. (B)</p> Signup and view all the answers

How do unmyelinated axons from the hypothalamus contribute to the function of the posterior pituitary gland (neurohypophysis)?

<p>They transport hormones produced in the hypothalamus for storage and release in the posterior pituitary. (B)</p> Signup and view all the answers

Which of the following accurately describes the role of thyroglobulin in thyroid hormone synthesis?

<p>It serves as a scaffold for the iodination of tyrosine residues to form thyroid hormones. (A)</p> Signup and view all the answers

What is the primary mechanism by which T3 and T4 hormones are transported from the follicle cells into the bloodstream?

<p>Diffusion across the cell membrane. (D)</p> Signup and view all the answers

What would be the likely outcome if lysosomal enzymes within the thyroid follicle cells were inhibited?

<p>Reduced release of T3 and T4 into the bloodstream. (B)</p> Signup and view all the answers

How does TSH (thyroid-stimulating hormone) primarily influence the production of thyroid hormones?

<p>By promoting the activity of ion pumps responsible for iodide transport into follicle cells. (A)</p> Signup and view all the answers

Which of the following is the immediate precursor to the formation of T3 and T4 hormones within the thyroid follicle?

<p>Iodinated thyroglobulin. (B)</p> Signup and view all the answers

Why is the binding of T3 and T4 to transport proteins like TBG important?

<p>It increases the hormones' solubility and half-life in the bloodstream. (A)</p> Signup and view all the answers

Which step of thyroid hormone synthesis is directly affected by the diffusion of iodide ions to the apical surface of follicle cells?

<p>The iodination of tyrosine residues on thyroglobulin. (D)</p> Signup and view all the answers

How would a deficiency in the TSH-sensitive ion pumps of the follicle cells directly impact thyroid hormone synthesis?

<p>Reduced iodine availability for iodination. (A)</p> Signup and view all the answers

Following a traumatic brain injury, a patient exhibits symptoms of dehydration and electrolyte imbalance. Damage to which area would most likely explain these symptoms?

<p>Posterior lobe of the pituitary gland (C)</p> Signup and view all the answers

In a pregnant woman, which hormone release would be most affected if the neurons of the paraventricular nucleus in the hypothalamus were damaged?

<p>Oxytocin (OXT) (A)</p> Signup and view all the answers

A researcher is studying the effects of a drug that specifically targets osmoreceptors in the hypothalamus. Which of the following hormonal changes would most likely be observed?

<p>Decreased secretion of antidiuretic hormone (ADH) (A)</p> Signup and view all the answers

A patient presents with increased muscle contractions in the uterus and milk ejection from mammary glands. Which hormonal imbalance is most likely contributing to these symptoms?

<p>Excessive secretion of oxytocin (OXT) (B)</p> Signup and view all the answers

A lesion in the posterior pituitary affects the secretion of ADH. Which of the following symptoms would you expect to observe in a patient with this condition?

<p>Increased urine volume and increased blood osmolarity (B)</p> Signup and view all the answers

How would a decrease in the concentration of releasing hormones (RH) from the hypothalamus most likely affect hormone levels in the anterior pituitary?

<p>Decrease the synthesis and secretion of specific anterior pituitary hormones. (D)</p> Signup and view all the answers

A researcher discovers a new hormone that is released from the hypothalamus and inhibits the release of a specific hormone from the anterior pituitary. How would the hypothalamus primarily exert this inhibitory effect?

<p>By preventing the synthesis and secretion of the specific anterior pituitary hormone. (D)</p> Signup and view all the answers

If negative feedback control of the anterior pituitary is disrupted, what is the most likely outcome?

<p>Hormone levels will fluctuate erratically. (D)</p> Signup and view all the answers

What is the functional significance of the hypophyseal veins in the context of the pituitary gland's role in endocrine regulation?

<p>They carry pituitary hormones into the cardiovascular system for distribution to target tissues. (B)</p> Signup and view all the answers

What is the functional significance of the pituitary gland's location within the sella turcica?

<p>It isolates the pituitary gland from the cranial cavity, providing protection. (C)</p> Signup and view all the answers

How does the binding of pituitary hormones to extracellular receptors initiate a response in target cells?

<p>By activating intracellular enzyme cascades via cAMP as a second messenger. (C)</p> Signup and view all the answers

How does the regulation of anterior pituitary hormone secretion illustrate the concept of homeostasis within the endocrine system?

<p>The hypothalamus detects changes in internal conditions and adjusts anterior pituitary secretion to maintain balance. (D)</p> Signup and view all the answers

If the infundibulum connecting the hypothalamus and pituitary gland is compressed, which of the following is the most likely immediate consequence?

<p>Disrupted communication between the hypothalamus and pituitary gland. (A)</p> Signup and view all the answers

A researcher discovers a new compound that prevents cAMP formation in pituitary cells. How would this compound likely affect the function of the pituitary gland?

<p>It would impair the ability of pituitary cells to respond to hypothalamic releasing hormones. (A)</p> Signup and view all the answers

Which structural feature directly facilitates communication between the hypothalamus and the pituitary gland?

<p>The infundibulum. (A)</p> Signup and view all the answers

If a tumor developed in the sella turcica and began to compress the pituitary gland, which of the following would be the most likely initial effect?

<p>Decreased secretion of one or more pituitary hormones due to impaired function. (A)</p> Signup and view all the answers

What is the primary role of the hypophyseal portal system in the context of pituitary function?

<p>Transport releasing and inhibiting hormones from the hypothalamus to the anterior pituitary. (B)</p> Signup and view all the answers

How does the anatomical arrangement of the pituitary gland within the sella turcica contribute to its functional integrity?

<p>It provides physical protection against mechanical damage. (B)</p> Signup and view all the answers

Which of the following is a direct effect of hormones released from the posterior pituitary gland?

<p>Increased water reabsorption in the kidneys. (C)</p> Signup and view all the answers

How would the removal of the anterior lobe of the pituitary gland affect the function of the adrenal cortex?

<p>It would lead to decreased production of glucocorticoids. (C)</p> Signup and view all the answers

What is the functional consequence of severing the hypophyseal portal system?

<p>Disrupted communication between the hypothalamus and the anterior pituitary. (D)</p> Signup and view all the answers

How does the presence of iodine affect the production of thyroid hormones?

<p>Iodine is directly incorporated into T3 and T4 during their synthesis. (C)</p> Signup and view all the answers

If a person has a genetic mutation that impairs the production of thyroglobulin, what impact would this have on thyroid function?

<p>Decreased production of T3 and T4 because thyroglobulin is essential for their synthesis. (B)</p> Signup and view all the answers

How does the hypothalamus respond to an increase in thyroid hormone levels in the blood?

<p>By decreasing the release of TRH to reduce TSH secretion from the pituitary. (C)</p> Signup and view all the answers

What effect would increased levels of somatomedins have on the release of growth hormone (GH) from the anterior pituitary?

<p>Decreased GH release, due to negative feedback on the pituitary and hypothalamus. (B)</p> Signup and view all the answers

How does the secretion of ADH from the posterior pituitary affect blood volume and osmolarity?

<p>Increases blood volume and decreases blood osmolarity. (D)</p> Signup and view all the answers

How would damage to the paraventricular nuclei of the hypothalamus most likely affect the body?

<p>Impaired uterine contractions during labor. (C)</p> Signup and view all the answers

What is the primary role of thyroglobulin within the thyroid follicle?

<p>To act as a storage molecule for tyrosine, the precursor to thyroid hormones. (A)</p> Signup and view all the answers

Which of the following best describes the role of inhibin in a male?

<p>Inhibits the production of FSH by the anterior pituitary. (B)</p> Signup and view all the answers

How does iodide contribute to the production of thyroid hormones?

<p>It is attached to tyrosine residues on thyroglobulin to form T3 and T4. (A)</p> Signup and view all the answers

What would be the likely effect of a genetic defect that impairs the production of thyroglobulin?

<p>Reduced or absent production of both T3 and T4 hormones. (B)</p> Signup and view all the answers

What distinguishes T3 from T4 chemically?

<p>T3 contains three iodine atoms, while T4 contains four. (B)</p> Signup and view all the answers

A pharmaceutical company is developing a drug to treat hypothyroidism. Which of the following mechanisms of action would be most effective in increasing thyroid hormone levels?

<p>Enhancing the iodination of tyrosine residues on thyroglobulin. (C)</p> Signup and view all the answers

Which structural aspect of the thyroid follicle is critical for the efficient production and storage of thyroid hormones?

<p>The presence of a colloid-filled cavity within the follicle. (A)</p> Signup and view all the answers

If a patient's thyroid gland is biopsied and the cells are found to have an abnormally high concentration of thyroglobulin within the follicle cells themselves (rather than in the colloid), what might this suggest?

<p>The patient's follicle cells are not effectively secreting thyroglobulin into the colloid. (A)</p> Signup and view all the answers

A researcher is investigating a new drug that selectively targets and destroys C cells in the thyroid gland. What direct effect would this drug have on thyroid hormone production?

<p>No direct impact on T3 and T4 production. (A)</p> Signup and view all the answers

Which of the following would result from chronic overstimulation of the thyroid follicle cells by TSH?

<p>Increased endocytosis of thyroglobulin and elevated levels of T3 and T4 in the bloodstream. (B)</p> Signup and view all the answers

What effect would a genetic defect that impairs the production of thyroglobulin have on thyroid hormone synthesis?

<p>Impaired synthesis of both T3 and T4 due to lack of a scaffold for iodine attachment. (C)</p> Signup and view all the answers

How does the binding of T3 and T4 to transport proteins in the bloodstream affect their availability to target tissues?

<p>It provides a reservoir of T3 and T4, maintaining stable hormone levels and preventing rapid fluctuations. (C)</p> Signup and view all the answers

If a drug inhibits the conversion of iodide ions to iodine atoms within the thyroid follicle cells, what direct effect would it have?

<p>Reduced iodination of tyrosine residues on thyroglobulin. (C)</p> Signup and view all the answers

A patient presents with elevated levels of TBG (thyroxine-binding globulin). How will this likely affect the total and free T4 levels in their blood?

<p>Decreased free T4 and increased total T4. (A)</p> Signup and view all the answers

What is the primary role of lysosomal enzymes in the production of thyroid hormones?

<p>To break down thyroglobulin and release T3 and T4. (A)</p> Signup and view all the answers

If the TSH-sensitive ion pumps on thyroid follicle cells malfunction, what would be the most immediate consequence?

<p>Inability to concentrate iodide within the follicle cells. (B)</p> Signup and view all the answers

How does diffusion contribute to the overall process of thyroid hormone production and release?

<p>Diffusion allows T3 and T4 to move from follicle cells into the bloodstream after thyroglobulin breakdown. (A)</p> Signup and view all the answers

Flashcards

Antidiuretic hormone (ADH)

A hormone that helps regulate water balance in the body by promoting water reabsorption in the kidneys.

Oxytocin (OXT)

A hormone involved in childbirth and lactation, promoting uterine contractions and milk ejection.

Pituitary gland

A small gland at the base of the brain that regulates various hormonal functions through its anterior and posterior lobes.

Anterior lobe of pituitary gland

Also called adenohypophysis; secretes hormones that regulate other endocrine organs.

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Posterior lobe of pituitary gland

Stores and releases ADH and OXT, produced by the hypothalamus.

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Epinephrine (E)

A hormone released by the adrenal medulla, also known as adrenaline, that increases heart rate and energy in response to stress.

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Norepinephrine (NE)

A hormone and neurotransmitter similar to epinephrine, involved in the body's response to stress and low blood pressure.

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Hypothalamus

A brain region that controls the pituitary gland and regulates many bodily functions, including hormone release.

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Hypothalamic Regulatory Hormones

Hormones produced by the hypothalamus that control the pituitary gland's activity.

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Releasing Hormones (RH)

Hormones that stimulate the anterior lobe to produce and release hormones.

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Inhibiting Hormones (IH)

Hormones that prevent the synthesis and release of hormones from the anterior lobe.

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Negative Feedback in Hormone Regulation

A regulatory mechanism where increased levels of a hormone inhibit further secretion.

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GH-RH

Growth Hormone-Releasing Hormone; stimulates the anterior pituitary to release growth hormone.

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Somatomedins

Hormones produced by the liver that stimulate growth of muscle and cartilage in response to GH.

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Melanocyte-stimulating hormone (MSH)

Hormone secreted by the pars intermedia that stimulates melanin production in skin cells.

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Neurohypophysis

Another name for the posterior lobe of the pituitary gland, containing axons from hypothalamic neurons.

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Prolactin (PRL)

A hormone produced by the anterior pituitary that stimulates mammary glands.

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Feedback Control

Regulation of hormone secretion by stimulating or inhibiting hormones.

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Growth Hormone (GH)

Stimulates growth, cell reproduction, and regeneration in humans.

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Growth Hormone-Releasing Hormone (GH-RH)

A hormone that promotes the release of growth hormone from the pituitary gland.

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Growth Hormone-Inhibiting Hormone (GH-IH)

A hormone that inhibits the release of growth hormone from the pituitary gland.

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Diabetogenic Effect

The effect of growth hormone that raises blood sugar levels by breaking down glycogen.

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PIH and PRH

Prolactin-inhibiting hormone (PIH) and prolactin-releasing hormone (PRH) control prolactin secretion.

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Gonadotropins

Hormones that stimulate gonadal function, including FSH and LH.

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Follicle-stimulating hormone (FSH)

A gonadotropin that stimulates follicle development in females and spermatogenesis in males.

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Luteinizing hormone (LH)

A gonadotropin that triggers ovulation in females and androgen production in males.

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Gonadotropin-releasing hormone (GnRH)

Hormone from the hypothalamus that stimulates FSH and LH production.

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Hypogonadism

A condition caused by low levels of gonadotropins, leading to underperformance of gonads.

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Thyroid-stimulating hormone (TSH)

Hormone that stimulates the thyroid gland to produce thyroid hormones.

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Adrenocorticotropic hormone (ACTH)

Hormone that stimulates the adrenal cortex to release corticosteroids.

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Follicle

Structure in the thyroid gland that contains T3 and T4 hormones.

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Thyroglobulin

A protein that binds iodine atoms to form thyroid hormones.

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Iodine conversion

Iodide ions diffuse and are converted into iodine (I0) in follicle cells.

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Endocytosis in thyroid

Process by which follicle cells take up thyroglobulin from the follicle cavity.

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T3 and T4

Thyroid hormones that regulate metabolism and energy levels in the body.

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Lysosomal digestion

Breakdown process where lysosomal enzymes digest thyroglobulin inside follicle cells.

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Transport proteins for T3 and T4

Proteins like TBG and transthyretin that carry T3 and T4 in the bloodstream.

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Diffusion of T3 and T4

The process by which T3 and T4 hormones move from follicle cells to the bloodstream.

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Pituitary Gland Location

Situated within the sella turcica and below the hypothalamus, connected by the infundibulum.

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Function of Pituitary Hormones

The pituitary gland releases nine important peptide hormones that bind to extracellular receptors using cAMP as a second messenger.

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Sellar Diaphragm

A structure that isolates the pituitary gland from the cranial cavity, ensuring proper function.

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Infundibulum

The connecting stalk between the hypothalamus and the pituitary gland, vital for hormone transport.

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Anterior Pituitary Lobe

Also named adenohypophysis; secretes hormones that regulate other glands, such as growth hormone.

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Posterior Pituitary Lobe

Stores and releases hormones like ADH and OXT, produced by the hypothalamus.

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Peptide Hormones

Hormones released by the pituitary gland that are made of amino acids and use cAMP as a second messenger.

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Hypophysis

Another term for the pituitary gland, reflecting its role as a key endocrine organ.

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Hypothalamic control of anterior lobe

Regulation of the anterior pituitary's hormone secretion by hypothalamic hormones.

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Negative feedback

A regulatory mechanism where an increase in hormone levels leads to reduced secretion of that hormone.

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Hypophyseal veins

Veins carrying pituitary hormones to the cardiovascular system for distribution in the body.

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ACTH

Adrenocorticotropic hormone; stimulates adrenal cortex to release corticosteroids.

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TSH

Thyroid-stimulating hormone; stimulates the thyroid gland to produce thyroid hormones.

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Thyroid hormones

Chemical messengers, specifically T3 and T4, regulating metabolism produced from thyroglobulin.

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Follicle of the thyroid gland

Small spherical structures in the thyroid that contain thyroglobulin and are involved in hormone synthesis.

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Colloid

Substance inside thyroid follicles where thyroglobulin is stored, facilitating hormone production.

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T3 (Triiodothyronine)

Thyroid hormone that contains three iodine atoms and regulates various physiological processes.

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T4 (Thyroxine)

Thyroid hormone containing four iodine atoms, important for metabolism and growth functions.

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C cells (Parafollicular cells)

Cells in the thyroid that produce calcitonin, involved in calcium regulation in the blood.

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Iodine absorption

Process where iodide ions are taken from the digestive tract into the bloodstream for thyroid hormone synthesis.

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Follicle Cavity

The space within a follicle that contains thyroid hormones T3 and T4.

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Endocytosis

Mechanism by which follicle cells absorb thyroglobulin from the follicle cavity.

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T3 and T4 Diffusion

The process of T3 and T4 hormones moving from follicle cells into the bloodstream.

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Iodide Ion Pump

A sensitive ion pump that facilitates iodide ion diffusion in follicle cells.

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Hypophyseal Portal System

A network of blood vessels that delivers regulatory hormones from the hypothalamus to the anterior pituitary.

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Regulatory Hormones

Hormones released by the hypothalamus that control the secretion of hormones from the pituitary gland.

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Thyroid Follicles

Hollow spheres within the thyroid gland lined with epithelium and involved in hormone synthesis.

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Iodide Ions (I–)

Elements absorbed by thyroid follicle cells necessary for the production of thyroid hormones.

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Thyroid Gland Structure

Gland located below the larynx that consists of two lobes connected by an isthmus.

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Adrenal Cortex

Outer region of the adrenal glands that produces steroid hormones like cortisol.

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Study Notes

Pituitary Gland

  • The pituitary gland, also known as the hypophysis, is located within the sella turcica.
  • A sellar diaphragm separates the pituitary gland from the cranial cavity.
  • The pituitary gland hangs inferior to the hypothalamus.
  • It's connected to the hypothalamus by the infundibulum.
  • It releases nine peptide hormones that bind to extracellular receptors.
  • These hormones use cAMP as a second messenger.

Hypothalamus

  • The hypothalamus regulates the pituitary gland's functions.
  • It synthesizes and transports antidiuretic hormone (ADH) and oxytocin (OXT) to the posterior pituitary.
  • It secretes regulatory hormones that control the anterior pituitary's secretory activity.
  • The hypothalamus includes autonomic centers that control the adrenal medulla.

Anterior Pituitary Lobe

  • Also called the adenohypophysis, this lobe's hormones control other endocrine glands or support functions in other organs.
  • It has three regions: pars distalis, pars tuberalis, and pars intermedia.

Median Eminence

  • The median eminence is a swelling near the infundibulum's attachment.
  • Hypothalamic neurons release regulatory hormones into interstitial fluids.
  • These hormones then enter the bloodstream via fenestrated capillaries.

Portal Vessels

  • Portal vessels connect two capillary networks.
  • The entire system is a portal system.
  • The hypophyseal portal system ensures that regulatory hormones reach cells in the anterior pituitary before general circulation.

Hypothalamic Control of Anterior Lobe

  • Two classes of hypothalamic regulatory hormones: releasing hormones (RH) and inhibiting hormones (IH).
  • Releasing hormones stimulate synthesis and secretion of anterior pituitary hormones.
  • Inhibiting hormones prevent the synthesis and secretion of hormones from the anterior lobe.
  • Secretion rates are controlled by negative feedback.

Hormones of Anterior Lobe

  • Thyroid-stimulating hormone (TSH)
  • Adrenocorticotropic hormone (ACTH), released due to corticotropin-releasing hormone (CRH)
  • Prolactin (PRL), release inhibited by prolactin-inhibiting hormone (PIH) and stimulated by prolactin-releasing hormone (PRH)
  • Growth hormone (GH), or somatotropin
  • Gonadotropins (FSH and LH), stimulated by gonadotropin-releasing hormone (GnRH)

Pars Intermedia

  • Secretes melanocyte-stimulating hormone (MSH).
  • Stimulates melanin production.
  • Mostly nonfunctional in adults, except in pregnant women or those with certain diseases.

Posterior Lobe of Pituitary Gland

  • Also called the neurohypophysis.
  • Contains unmyelinated axons of hypothalamic neurons (supraoptic and paraventricular nuclei).
  • Produces antidiuretic hormone (ADH) and oxytocin (OXT).
  • ADH stimulates water reabsorption in the kidneys.
  • Oxytocin stimulates uterine contraction and milk ejection.

Thyroid Gland

  • Lies inferior to the thyroid cartilage of the larynx.
  • Consists of two lobes connected by an isthmus.
  • Thyroid follicles are hollow spheres lined with cuboidal epithelium.
  • Surrounded by capillaries, follicle cells absorb iodide ions from the blood.
  • Follicle cavities contain viscous colloid (containing thyroglobulin).
  • C cells (parafollicular cells) secrete calcitonin.

Thyroglobulin

  • A globular protein synthesized by follicle cells.
  • Secreted into thyroid follicle colloid.
  • Contains tyrosine, the building blocks of thyroid hormones.

Thyroid Hormones

  • Thyroxine (T₄), or tetraiodothyronine, contains four iodine atoms.
  • Triiodothyronine (T₃), contains three iodine atoms.

Thyroid-stimulating Hormone (TSH)

  • Absence of TSH causes thyroid follicles to become inactive.
  • Neither synthesis nor secretion occurs.
  • Binds to plasma membrane receptors, activating key enzymes in thyroid hormone production.

Thyroid Hormones' Effects

  • Affect almost every cell in the body.
  • Enter target cells via transport systems.
  • Bind to cytoplasmic and mitochondrial receptors or in the nucleus.
  • In children, essential for normal development of skeletal, muscular, and nervous systems.
  • Increase cellular metabolism (calorigenic effect).
  • Increase energy consumption and heat generation.

C Cells (Parafollicular Cells)

  • Produce calcitonin (CT).
  • Regulates calcium (Ca²⁺) concentrations in bodily fluids.
  • Stimulates Ca²⁺ excretion by kidneys.
  • Prevents Ca²⁺ absorption by the digestive tract.

Effects of Thyroid Hormones

  • Elevates oxygen and energy consumption, affecting body temperature
  • Increases heart rate and strength of contraction
  • Enhances sympathetic stimulation responsiveness
  • Maintains normal respiratory function
  • Stimulates red blood cell formation
  • Affects other endocrine tissues
  • Speeds up bone mineral turnover

Thyroid-binding Globulins (TBGs)

  • Proteins that bind 70-75% of T₃ and T₄ as they enter the bloodstream.

Growth Hormone

  • Stimulates liver cells to release somatomedins stimulating tissue growth.

  • Somatomedins increase amino acid uptake in skeletal muscle and other cells.

  • Stimulates stem cells in connective and epithelial tissues to divide.

  • Promotes fat breakdown (glucose sparing).

  • Causes glycogen breakdown, having a diabetogenic effect.

  • Growth hormone's production is regulated by growth hormone-releasing hormone (GH-RH) and growth hormone-inhibiting hormone (GH-IH).

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Ch 18 Lecture Presentation (Pituitary Gland) PDF

Description

This quiz focuses on the relationship between the pituitary gland and hypothalamus, exploring the function of the hormones secreted by the anterior lobe, the structures controlled by the hypothalamus, and the mechanisms of hypothalamic control over the adrenal medulla. It also covers the regulation of hormone secretion in the anterior pituitary lobe.

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