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Biology Kaplan MCAT > Ch. 5: The Endocrine System > Flashcards

Ch. 5: The Endocrine System Flashcards

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1
Q

Hormones

A

Endocrine signaling involves the secretion of hormones directly into the bloodstream. The hormones travel to distant target tissues, where they bind to receptors and induce a change in gene expression or cell function

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2
Q

Peptide Hormones

A

Composed of amino acids and are derived from larger precursor proteins that are cleaved during post translational modification; polar and cannot pass through plasma membrane; bind to extracellular receptors, were they trigger the transmission of a second messenger; each step of the signaling cascade can demonstrate amplification of the signal; peptide hormones usually have rapid onset but are short lived; travel freely in the bloodstream and do not require a special carrier

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3
Q

Steroid Hormones

A

Derived from cholesterol; minimally polar and can pass through the plasma membrane; bind to and promote a conformational change of intracellular or intranuclear receptors; the hormone-receptor complex binds to DNA, affecting the transcription of a particular gene; slow onset but long-lived; cannot dissolve in the bloodstream and must be carried by specific proteins

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4
Q

Amino acid-derivative hormones

A

Modified amino acids; chemistry shares some features w peptide hormones and some features w steroid hormones; diff amino acid-derivative hormones share diff features w these other hormone classes; common examples include epinephrine, norepinephrine, triiodothyronine, and thyroxine

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5
Q

Hormone classification by target tissues

A

Direct Hormones: Major effects in non-endocrine tissues

Tropic Hormones: major effects in other endocrine tissues

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6
Q

Hypothalamus

A

Bridge between the nervous and endocrine systems

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7
Q

Release of hormones from hypothalamus

A

Mediated by a number of factors including projections from other parts of the brain, chemo- and baroreceptors in the blood vessels, and negative feedback from other hormones

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8
Q

Negative Feedback

A

The final hormone (or product) of a pathway inhibits hormones (or enzymes) earlier in the pathway, maintaining homeostasis

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9
Q

Hypophyseal Portal System

A

Directly connects the hypothalamus and anterior pituitary gland. Hypothalamus stimulates the anterior pituitary gland through paracrine release of following hormones into the hypophyseal portal system:

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10
Q

Gonadotropin-releasing hormone (GnRH)

A

Promotes the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

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11
Q

Growth hormone-releasing hormone (GHRH)

A

Promotes the release of growth hormone

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12
Q

Thyroid-releasing hormone (TRH)

A

Promotes the releasing thyroid-stimulating hormone (TSH)

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13
Q

Corticotropin-releasing factor (CRF)

A

Promotes the release of adrenocorticotropic hormone (ACTH)

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14
Q

Prolactin-inhibiting factor (PIF or dopamine)

A

Inhibits the release of prolactin

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15
Q

Interactions with the Posterior Pituitary

A

Occur via the axons of the nerves in the hypothalamus. Antidiuretic hormone (ADH or vasopressin) and oxytocin are synthesized in the hypothalamus and then travel down these axons to the posterior pituitary, where they are released into the bloodstream

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16
Q

Anterior pituitary

A

Releases following hormones in response to stimulation from the hypothalamus: FSH, LH, ACTH, and TSH are tropic hormones and prolactin, endorphins and growth hormone are direct hormones

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17
Q

Follicle stimulating hormone (FSH)

A

Promotes the development of ovaries and follicles in females and spermatogenesis in males

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18
Q

Luteinizing hormone (LH)

A

Promotes ovulation in females and testosterone production in males

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19
Q

Adrenocorticotropic hormone (ACTH)

A

Promotes synthesis and release of glucocorticoids from the adrenal cortex

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20
Q

Thyroid stimulating hormone (TSH)

A

Promotes synthesis and release of triiodothyronine and thyroxine from the thyroid

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21
Q

Prolactin

A

Promotes milk production

22
Q

Endorphins

A

Decrease perception of pain and can cause euphoria

23
Q

Growth hormone (GH)

A

Promotes growth of bone and muscle and shunts glucose to these tissues. It raises blood glucose concentrations.

24
Q

Posterior pituitary

A

Releases 2 hormones produced in the hypothalamus (ADH and oxytocin)

25
Q

Antidiuretic hormone

A

ADH or vasopressin, secreted in response to low blood volume or increased blood osmolarity and increases reabsorption of water in the collecting duct of the nephron, increasing blood volume and decreasing blood osmolarity

26
Q

Oxytocin

A

Secreted during childbirth and promotes uterine contractions. Also promotes milk ejection and may be involved in bonding behavior. It is unusual in that it has a positive feedback look, not negative

27
Q

Thyroid

A

Located at the base of the neck in front of the trachea; produces 3 key hormones: 1. triiodothyronine and 2. thyroxine and 3. Calcitonin

28
Q

Follicular cells

A

Cells of the thyroid; produce triiodothyronine (T3) and thyroxine (T4) which increase basal metabolic rate and alter the utilization of glucose and fatty acids. Thyroid hormones are required for proper neurological and physical development in children

29
Q

Parafollicular (C) cells

A

Cells of the thyroid; produce calcitonin which decreases calcium concentration by promoting calcium excretion in the kidneys, decreasing calcium absorption in the gut, and promoting calcium storage in bone

30
Q

Parathyroid Glands

A

Release parathyroid hormone (PTH) which increases blood calcium concentration

31
Q

Parathyroid Hormone (PTH)

A

Decreases excretion of calcium by the kidneys and increases bone resorption directly to increase blood calcium concentration; activates vitamin D, which is necessary for calcium and phosphate absorption from the gut; promotes resorption of phosphate from bone and reduces reabsorption of phosphate in the kidney, but vitamin D promotes absorption of phosphate from the gut; these 2 effects on phosphate concentration somewhat cancel each other

32
Q

Adrenal cortex

A

Produces 3 classes of steroid hormones: 1. Glucocorticoids, 2. Mineralocorticoids 3. Cortical Sex hormones

33
Q

Glucocorticoids

A

Ex. cortisol and cortisone; increase blood glucose concentration, reduce protein synthesis, inhibit the immune system, and participate in the stress response. Glucocorticoid release is stimulated by ACTH

34
Q

Mineralocorticoids

A

Ex. aldosterone; promote sodium reabsorption in the distal convoluted tubule and collecting duct, thus increasing water reabsorption. Aldosterone also increases potassium and hydrogen ion excretion. It is regulated by the renin-angiotensin-aldosterone system, not ACTH

35
Q

Cortical Sex Hormones

A

Include androgens (like testosterone) and estrogens in both males and females

36
Q

Adrenal Medulla

A

Derived from the nervous system and secretes catecholamines into the bloodstream

37
Q

Catecholamines

A

Include epinephrine and norepinephrine, which are involved in the fight-or-flight (sympathetic) response; promote glycogenolysis, increase the basal metabolic rate, increase heart rate, dilate the bronchi, and alter blood flow

38
Q

Pancreas

A

Produces hormones (Glucagon, Insulin, Somatostatin) that regulate glucose homeostasis

39
Q

Glucagon

A

Produced by alpha cells and raises blood glucose levels by stimulating protein and fat degradation, glycogenolysis, and gluconeogenesis

40
Q

Insulin

A

Produced by beta cells and lowers blood glucose levels by stimulating glucose uptake by cells and anabolic processes, like glucogen, fat and protein synthesis

41
Q

Somatostatin

A

Produced by delta cells and inhibits insulin and glucagon secretion

42
Q

Gonads

A

Testes and Ovaries; Produce hormones that are involved in development and maintenance of the reproductive systems and secondary sex characteristics

43
Q

Testes

A

Secrete testosterone

44
Q

Ovaries

A

Secrete estrogen and progesterone

45
Q

Pineal Gland

A

Releases melatonin

46
Q

Melatonin

A

Helps to regulate circadian rhythms

47
Q

Other organs release hormones…

A

Even though they are not primarily considered part of the endocrine system

48
Q

Secretin, Gastrin, and Cholecystokinin

A

Cells in the stomach and intestine produce these

49
Q

Erythropoietin

A

Stimulates bone marrow to produce erythrocytes (red blood cells) in response to low oxygen levels in the blood

50
Q

Atrial natriuretic peptide (ANP)

A

The atria of the heart secrete this hormone; promotes excretion of salt and water in the kidneys in response to stretching of the atria (high blood volume)

51
Q

Thymosin

A

Secreted by the thymus, important for proper T-cell development and differentiation

Biology Kaplan MCAT (12 decks)

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