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MCAT Biology > The Endocrine System > Flashcards

The Endocrine System Flashcards

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0
Q

What portal system connects the hypothalamus to the ANTERIOR pituitary?

A

Hypophyseal portal system

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1
Q

Define the differences between autocrine, paracrine, and endocrine signaling.

A

Autocrine-the same cell releases the signal and is stimulated.
Paracrine-neighboring cells release the signal and are stimulated.
Endocrine-signal release and stimulation happens over long distances (ie: hypothalamus signals to the anterior pituitary, via paracrine signaling, to release FSH or LH to the gonads, via endocrine signaling).

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2
Q

What are 5 hormones released by the hypothalamus, and what 7 hormones does each cause the anterior pituitary to release? REMEMBER FLATPEG

A 
GnRH➡️FSH/LH
GHRH➡️GH
PIF➡️Prolactin
TRH➡️TSH
CRF➡️ACTH
The ant pit also releases endorphins.
F-FSH
L-LH
A-ACTH
T-TSH
P-PROLACTIN
E-ENDORPHINS
G-GH
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3
Q

Both the hypothalamus and anterior pituitary operate using what kind of feedback?

A

Feedback inhibition.

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4
Q

What 2 hormones does the posterior pituitary release and how are signals sent from the hypothalamus?

A

Signals are sent using neurons.

Oxytocin and ADH

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5
Q

What is the difference between a direct and tropic hormone? Which anterior pituitary hormones are direct and which are tropic?

A

Direct: bind to a receptor on a target cell and cause immediate effects
PEG=direct

Tropic: binds to a receptor but results in the release of effector hormones.
FLAT=tropic

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6
Q

What does ACTH do?

A

ACTH causes the adrenals to increase the levels of cortisol in the blood.

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7
Q

What does growth hormone do?

A

GH promotes growth of bone and muscle.

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8
Q

Where does Growth in bone occur?

A

At the epiphyseal plates of long bone, which seal during puberty.

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9
Q

What does prolactin do?

A

Stimulates milk production in mammary glands

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10
Q

What does TSH do?

A

Stimulates the thyroid to release thyroid hormone (TH) and to take up iodine.

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11
Q

What does oxytocin do?

A

Released during childbirth and allows for contractions of the uterus. It can also be released in response to sucking which will cause milk production.

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12
Q

What are the 2 major functions of the thyroid?

A 
Setting basal metabolic rate (TH)
Calcium homeostasis (calcitonin)
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13
Q

What do increased levels of T3 and T4 (thyroid hormones) result in?

A

Increased cellular respiration, increased protein and fatty acid turnover. *WORKS ON A NEGATIVE FEEDBACK LOOP

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14
Q

What is hypothyroidism characterized by and how does it occur?

A

It comes from a deficiency in iodine or inflammation of the thyroid. Results in a slowed metabolic rate, characterized by lethargy, decreased body temp, slowed heart rate, slowed respiration, cold intolerance, and weight gain.

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15
Q

What is hyperthyroidism characterized by and how does it occur?

A

It occurs from an excess of TH, causing a tumor or overstimulation. Increased metabolic rate and exactly the opposites of hypothyroidism.

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16
Q

What is the role of calcitonin?

A

Decreases plasma calcium levels by:

1) increase excretion from the kidneys
2) decrease absorption from the gut
3) increase storage in bone

So, high levels of calcium in the blood will induce the release of calcitonin.

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17
Q

What does the parathyroid release and what does it do?

A

Parathyroid hormone (PTH)-antagonistic hormone to calcitonin and acts to increase bold calcium levels by doing exactly the opposite of calcitonin. Namely, it increases bone resorption, which frees up calcium, and activates vitamin D which allows for absorption of calcium in the gut.

18
Q

What hormones does the adrenal cortex release?

A

Corticosteroids (in response to ACTH stimulation).

  1. Glucocorticoid (sugar)
  2. Mineralcorticoid (salt)
  3. Cortical sex hormones (sex)
19
Q

What are two types of glucocorticoids and what does each do?

A

Cortisol and cortisone-both raise blood glucose by increasing gluconeogenisis and decreasing protein synthesis. Also decrease inflammation and immunological responses.

20
Q

What is a type if mineralcorticoid?

A

Aldosterone

21
Q

What is an example if a cortical sex hormone?

A

Androgens

22
Q

What does the adrenal medulla release?

A

Epinephrine and norepinephrine (AKA catecholamines)

23
Q

What do the alpha, beta, and delta cells of the pancreas release?

A

Alpha-glucagon
Beta-insulin
Delta-somatostatin

24
Q

What does glucagon and insulin do?

A

Glucagon is an Antagonist to insulin. Released in times of low blood glucose and is responsible for raising blood glucose levels.

Insulin is released in response to high blood glucose and is responsible for lowering blood glucose levels.

25
Q

Excess insulin is called

A

Hypoglycemia (low blood sugar)

26
Q

Insufficient insulin is called…

A

Diabetes (hyperglycemia) or excess blood sugar.

27
Q

Diabetes can cause…

A

Polyuria- or increase frequency of urination

Polydipsia-increased thirst

28
Q

What is the difference between Type I and Type II diabetes?

A

Type I: insulin dependent:autoimmune destruction of beta cells. Requires injections
Type II: insulin independent: body resists the effects of insulin. Can be inherited or due to high sugar diets.

29
Q

What does somatostatin do?

A

Inhibits both glucagon and insulin

30
Q

What is the site if soermatogenesis?

A

Testes

31
Q

FSH is necessary in males for…

A

Stimulating Sertoli cells, which is necessary for sperm maturation.

32
Q

LH is important in males for…

A

Causing interstitial cells to release testosterone

33
Q

What does testosterone do?

A

1) make embryonic differentiation
2) make sexual development at puberty
3) maintenance of secondary sex characteristics

34
Q

What is androgen insensitivity syndrome?

A

A genetic male displays female secondary sex characteristics

35
Q

What two hormones do the ovaries produce and what do they do?

A

1) Estrogen- secreted in response to high levels if LH and FSH. Responsible for secondary sex characteristics and for thickening of the endometrium each month to prepare for zygote implantation. Also stimulate the development of the female reproductive tract.
2) Progesterone- secreted in response to high levels if LH and is responsible for the development and maintenance of the endometrium.

36
Q

Describe the Follicular phase of the menstrual cycle.

A

Begins when menstrual flow begins. Characterized by low levels of estrogen and progesterone. These low levels cause increased secretion of GnRH, which leads to increased secretion of FSH and LH, creating ovarian follicles that level off concentrations. Estrogen then works to regrow the endometrial lining.

37
Q

Describe the second phase of the menstrual cycle, ovulation.

A

There is a surge in LH (due to increased estrogen levels) that induces ovulation.

38
Q

Describe the third phase of the menstrual cycle, the luteal phase.

A

Post ovulation, LH causes the ruptures follicle to become the corpus luteum, which secretes progesterone which maintains the uterine lining (which is partly regenerated using estrogen). While we have both high estrogen and progesterone, this causes negative feedback of GnRH, LH, and FSH to prevent multiple ova in one cycle.

39
Q

Describe the fourth phase of the menstrual cycle, menstruation.

A

If implantation does not occur, human chorionic gonadotropin (hCG) can’t stimulate the corpus luteum, causing progesterone levels to fall and the uterine lining to be shed.

40
Q

What gland secretes melatonin?

A

Pineal gland

41
Q

What does erythropoietin do and what secretes it?

A

The kidneys-it stimulates bone marrow to produce more erythrocytes in response to low blood O2.

42
Q

What is a peptide hormone?

A

Made up of amino acids, charged so they can’t cross the phospholipid bilayer and bind to the outer receptor if the cell to cause a signaling cascade. Short lived effects!

43
Q

What is a steroid hormone?

A

Derived from cholesterol and can easily cross the cell membrane. Have intracellular receptors. Once bound, they dimerize and alter transcription. Long lived effects but takes longer to see the effects.

MCAT Biology (7 decks)

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