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Malika Biology MCAT > Chapter 5 - Endocrine System > Flashcards

Chapter 5 - Endocrine System Flashcards

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1
Q

Hormones are classified according to 3 identities:

A

Peptides, steroids, or amino acid derivatives

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2
Q

Characteristics of peptide hormones

A

-made of amino acids
-Charged
-Cannot pass through the cell membrane
-Can cause signal amplification
-travel freely through the bloodstream
-Effects are rapid but short-lived

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3
Q

How are peptide hormones made?

A

They are derived from large precursor polypeptides, which are made on ribosomes. After they are cleaved during post-translational modifications and then transported to the Golgi for further modification, this allows them to be activated and packaged into vesicles for exocytosis.

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4
Q

What is the mechanism of action for peptide hormones?

A

Since they can’t pass through the cell membrane, they bind to a receptor on the plasma membrane and trigger the transmission of a second messenger signal, resulting in a signaling cascade.

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5
Q

What are steroid hormones?

A

They are hormones that are derived from cholesterol and produced, primarily by gonads and the adrenal cortex.

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6
Q

Characteristics of steroid hormones

A

-Can cross the plasma membrane
-Made of lipids, so can’t travel freely in the bloodstream
-Effects are slower, but longer lasting

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7
Q

What is the mechanism of action of steroid hormones?

A

They cross the plasma membrane, bind to an intracelular receptor either in the cytoskeleton or nucleus, and form a steroid hormone-receptor complex which binds to DNA directly.

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8
Q

___________ hormones participate in the regulation of genes.

A

Steroid

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9
Q

How do the level of carrier proteins affect the level of active steroid hormones?

A

If there are more carrier proteins in the bloodstream, the steroid hormones remain inactive. As the level of carrier proteins decrease, the level of active hormones increase.

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10
Q

What are amino acid hormones?

A

A class of hormones that is less common. They are made of usually one or two types of amino acids, unlike peptide hormones which are made of polypeptide chains.

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11
Q

Examples of amino acid hormones

A

Epinephrine, norepinephrine, triiodothyronine, and thyroxine

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12
Q

What is the mechanism of action of amino acid hormones?

A

Some bind intracellularly (slower onset).
Some bind to receptors on the cell membrane (faster onset, but short lived).

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13
Q

What is the difference between tropic hormones and direct hormones?

A

Tropic hormones don’t act directly on the target tissue, rather they require an intermediary.
Direct hormones are secreted and act directly on the target tissue.

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14
Q

Tropic hormones usually originate in what part of the body?

A

In the brain.

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15
Q

Name some examples of tropic hormones

A

GnRH and LH

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16
Q

What are the main endocrine organs?

A

Hypothalamus, pituitary gland, thyroid, parathyroid glands, adrenal glands, pancreas, gonads, pineal gland

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17
Q

Main functions of the hypothalamus

A

Control sleep-wake cycles, regulate appetite and satiety, regulate blood osmolarity

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18
Q

The posterior pituitary is made of _________, while the anterior pituitary is made of _______.

A

neural tissue, endocrine tissue

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19
Q

How does the hypothalamus control the anterior pituitary gland?

A

Via paracrine release of hormones into a portal vein that travels directly to the anterior pituitary. This is called the hypophyseal portal system.

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20
Q

The hypothalamus secretes the following hormones:

A

Gonadotropin-releasing hormone
Growth hormone-releasing hormone
Thyroid releasing hormone
Corticotropin-releasing factor
Prolactin-inhibiting hormone

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21
Q

The secretion of hormones from the hypothalamus is controlled by ________ feedback.

A

Negative

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22
Q

How does the hypothalamus control the posterior pituitary?

A

It send neuron axons down which terminate in the posterior pituitary. When stimulated these neurohormones are released by exocytosis from the axons into small blood vessels.

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23
Q

Which 2 hormones are released by the posterior pituitary?

A

Anti-diuretic hormone (ADH) and oxytocin

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24
Q

True or false:
The hormones released by the posterior pituitary, ADH and oxytocin, are synthesized in the hypothalamus.

A

True, ADH and oxytocin aren’t synthesized by the posterior pituitary, they are just released by the posterior pituitary. The posterior pituitary doesn’t synthesize any hormones itself.

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25
Q

ADH is secreted in response to what to factor?

A

Blood volume and blood osmolarity (high solute concentration)

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26
Q

Low blood volume is detected by what kind of receptors in the body?

A

Baroreceptors

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27
Q

If blood osmolarity increases, the level of ADH ________. This causes ________ aquoporin water channels on the collecting duct of the kidneys.

A

Increases, more

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28
Q

If blood osmolarity increases, the level of ADH ________. This causes ________ aquaporin channels on the collecting duct of the kidneys.

A

Increases, more

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29
Q

If blood volume is high, the level of ADH __________. This causes __________ aquaporin channels on the collecting duct of the kidneys.

A

Decreases, less

30
Q

Oxytocin has two functions, what are they?

A

Promotes uterine contraction in childbirth and promotes milk ejection through the nipple by contraction of smooth muscle in the breast.

31
Q

Which hormones are released by the anterior pituitary?

A

FLAT PEG:
Follicle-stimulating hormone
Luteinizing hormone
Adrenocorticotropic hormone
Thyroid stimulating hormone
Prolactin
Endorphins
Growth hormone

32
Q

Prolactin is released by which endocrine organ? What is the function of prolactin?

A

Anterior posterior pituitary; prolactin stimulates milk production in the mammary glands, BUT it ISN’t responsible for milk ejection. Oxytocin causes milk ejection.

33
Q

Endorphins are one of the direct hormones released by the anterior pituitary. What are their function?

A

They are natural painkillers which decrease the perception of pain and induce a sense of euphoria.

34
Q

Growth hormone is one of the direct acting hormones released by the anterior pituitary. What is its function?

A

It’s responsible for promoting the growth of bone and muscle. It prevents glucose uptake in tissues that aren’t growing, thus increasing glucose availability overall, to allow muscle and bone to use it.

35
Q

What are the main functions of the thyroid?

A
  1. Setting basal metabolic rate
  2. Promoting calcium homeostasis
36
Q

Which two hormones produced by the thyroid are capable of resetting the basal metabolic rate? How do they get the metabolic rate to reset?

A

Triiodothyronine (T3) and thyroxine (T4)
They increase/decrease cellular respiration, alter the utilization of glucose and fatty acids, and increase protein & fatty acid turnover.

37
Q

Symptoms of hypothyroidism

A

Lethargy, decreased body temp, slowed HR & respiratory rate, cold intolerance, weight gain

38
Q

Symptoms of hyperthyroidism

A

Heightened activity level, increased body temp, increased HR & respiratory rate, heat intolerance, and weight loss

39
Q

What is the role of calcitonin which is produced by the thyroid?

A

Calcitonin controls calcium homeostasis in the body. It decreases the level of calcium in the blood plasma.

40
Q

How does calcitonin decrease the level of calcium in the blood plasma?

A
  1. Increasing calcium excretion from the kidneys
  2. Decreasing calcium absorption from the gut
  3. Increasing storage of calcium in the bone
41
Q

What is the parathyroid gland?

A

It is 4 small pea sized structures which sit on the posterior surface of the thyroid.

42
Q

What is the function of the parathyroid gland?

A

It releases parathyroid hormone which raises blood calcium levels. It does this by three ways:
1. Decreasing excretion of calcium by the kidneys
2. Increasing absorption of calcium in the gut
3. Increasing bone reabsorption of calcium

43
Q

Where are the adrenal glands located?

A

They sit on top of the kidneys.

44
Q

The adrenal cortex produces three classes of steroid hormones. What are they?

A

Glucocorticoids, mineralocorticoids, and cortical sex hormones

45
Q

What are the functions of glucocorticoids?

A

They raise blood glucose levels by increasing gluconeogenesis and decreasing protein synthesis. They also decrease inflammation and immune responses.

46
Q

What are the two glucocorticoids that are usually tested on the MCAT?

A

Cortisol and cortisone

47
Q

Which hormone released by the anterior pituitary controls the release of glucocorticoid hormones?

A

Adrenocorticotropic hormone (ACTH)

48
Q

What is the adrenal gland made of?

A

It is made of a cortex and a medulla.

49
Q

Aldosterone is a mineralocorticoid that is secreted by the adrenal cortex. What are the two main functions of this hormone?

A

Regulate blood pressure and regulate blood volume

50
Q

True or false:
Aldosterone is signaled to be released if blood pressure or blood volume is low.

A

True, aldosterone is released when blood pressure is low.

51
Q

What is the mechanism of action of aldosterone?

A

Aldosterone increases the reabsorption of sodium in the distal convoluted tubule and collecting duct by adding Na channels which allow water to to flow in with sodium ions to be reabsorbed. This causes blood pressure and blood volume to increase, but has NO effect on osmolarity of blood.

52
Q

Endocrine pathway causing the release of glucocorticoids

A

Hypothalamus releases corticotropin releasing factor (CRF) —> anterior pituitary releases adrenocorticotropic hormone —> adrenal cortex releases glucocorticoids such as cortisol

53
Q

Aldosterone is controlled by the renin-angiotensin aldosterone pathway. Describe it.

A

Blood pressure is decreased —> juxtaglomerular baroreceptors in the kidney secrete renin —> renin is an enzyme which cleaves angiotensinogen —> angiotensinogen is converted to its active form: angiotensin I —> ACE enzyme converts angiotensin I to angiotensin II —>finally angiotensin II stimulates the adrenal cortex to secrete aldosterone

54
Q

What hormones does the adrenal medulla release?

A

It releases catecholamines: epinephrine and norepinephrine. They are regulated by the sympathetic NS.

55
Q

When epinephrine or norepinephrine is released, through a process called ________, blood flow to the skeletal muscle, heart, lungs, and brain is increased.

A

Vasodilation

56
Q

When epinephrine or norepinephrine is released, through a process called ________, blood flow to the gut, kidneys, and skin is decreased.

A

Vasoconstriction

57
Q

What hormones do the gonads secrete?

A

The testes secrete testosterone and the ovaries secrete estrogen.

58
Q

The pineal gland releases _______.

A

Melatonin

59
Q

The pancreas contains Islet of Langerhans cells which secrete hormones into the bloodstream. The cells are divided into three distinct types which are:

A

Alpha - secrete glucagon
Beta - secrete insulin
Delta - secrete somatostatin

60
Q

Type I diabetes

A

Caused by autoimmune destruction of the B-cells of the pancreas which results in very low or absent levels of insulin production.

61
Q

Type II diabetes

A

Caused by glucose receptors on the membrane being resistant to insulin release, so glucose is not taken in properly by the cell. Caused by genetics and environmental factors such as diet.

62
Q

When blood glucose levels are high, ________ is secreted.

A

Insulin

63
Q

When blood glucose levels are low, __________ is secreted.

A

Glucagon

64
Q

What is the function of somatostatin?

A

Produced by the delta cells of the pancreas, it inhibits both insulin and glucagon secretion.

65
Q

The kidney secrete a hormone called erythropoietin. What is its function?

A

It stimulates bone marrow to increase production of red blood cells in response to low oxygen levels.

66
Q

The heart releases, a hormone called ________. What is its function?

A

It’s function is to decrease blood volume in the atria which therefore decrease blood pressure (as they are directly proportional).

67
Q

If you want to increase blood volume, but maintain blood osmolarity would you use aldosterone or ADH as the hormone?

A

Aldosterone

68
Q

What is the mechanism of action of atrial natriuretic peptide?

A

It helps to regulate blood pressure by increasing vasodilation of the arteries. It also lowers blood volume by promoting excretion of sodium and therefore water at the kidney, therefore increasing urine volume.

69
Q

What is the main function of cortisol?

A

Cortisol stimulates gluconeogenesis (creation of glucose by the liver) by breaking down protein & fat as metabolites to create that glucose.
It also blocks the uptake of glucose in the non-vital tissues (other than the CNS). Thus, causing increased glucose in the blood.
High levels of cortisol can cause muscle weakness and decreased WBCs.

70
Q

Epinephrine and norepinephrine are what kind of hormones? What is their mechanism of action?

A

They are amino acid derivative hormones which are peptide soluble meaning they can’t cross the plasma membrane. They instead bind to a receptor on the plasma membrane and activate a G proteins signaling cascade.

71
Q

If blood osmolarity increases, blood pressure (increases/decreases).

A

Increases

Malika Biology MCAT (12 decks)

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