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MCAT Biology > C5 - Endocrine System > Flashcards

C5 - Endocrine System Flashcards

1
Q

What are the 3 types of hormones based on chemical identities?

A

Peptide, amino acid derivatives, and steroids

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2
Q

What are peptide hormones all derived from? How do they get to the release stage?

A

Larger precursor polypeptides that are cleaved during post transitional modification. Smaller units are transported to the Golgi apparatus for further modifications that activate the hormones and direct to correct location. Such hormones are released by exocytosis after being packaged into vesicles

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3
Q

How come peptide hormones cant enter the cell? And what must happen instead for it to reap its effects?

A

Peptide hormones are charged and cannot pass through the PM, instead they bind to an extracellular receptor triggering a signal known as the second messenger (peptide hormone is considered the first messenger)

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4
Q

What does a signaling cascade refer to?

A

The connection of the hormone at the surface of the cell and the effect brought about by second messengers within the cell.

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5
Q

Common second messengers are cAMP, IP3, and calcium. What does the first 2 stand for?

A

cAMP - cyclic adenosine monophosphate

IP3 - inositol triphosphate

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6
Q

What is the process that happens when a peptide hormone binds to a G protein-coupled receptor?

A

It triggers the receptor to either activate or inhibit an enzyme called adenylate cyclase, raising or lowering the levels of cAMP. cAMP can bind to intracellular targets, such as protein kinase A, which phosphorylates transcription factors like cAMP response element-binding protein (CREB) to exert the hormones ultimate effect

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7
Q

In terms of length and speed how do these peptide hormones act?

A

They act usually rapid but short lived

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8
Q

Because peptide hormones are generally water soluble what does this mean for travel in the bloodstream?

A

They can travel freely and usually do not require carriers

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9
Q

Steroid hormones are derived from what? Produced primarily by what structures?

A

Cholesterol. Produced mostly by the gonads and adrenal cortex

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10
Q

In terms of the cell membrane since steroid hormones are derived from nonpolar molecules what does this mean? Hence, where are their receptors?

A

They can easily cross the cell membrane, receptors are usually intracellular or intranuclear

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11
Q

Upon binding to receptors what do steroid hormones cause? What process proceeds? How does it inflict its effects?

A

The steroid hormone-receptor complex undergoes conformational changes. The receptor can then bind directly to DNA, resulting in either an increase or decrease of transcription of particular genes

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12
Q

What is dimerization?

A

A form of conformational change that involves the pairing of two receptor-hormone complexes

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13
Q

How do steroid hormones act in terms of length and speed of onset? Why is this?

A

They are slow but longer lived than peptide hormones because steroid hormones participate in gene regulation. Causing alterations in the amount of mRNA and protein present in a cell by direct action on DNA

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14
Q

In terms of transportation what does steroid hormones being non water soluble mean?

A

They must be carried by proteins in the bloodstream to travel around the body

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15
Q

When hormones are attached to carrier proteins what does this mean for their activity levels? For example some conditions cause an increase of proteins that carry thyroid hormones, how would this affect an outcome?

A

They are generally inactive and must dissociate from the carrier to function.

When there are more protein carriers for thyroid hormones (thyroxine-binding globulin (TGB)) this causes the body to perceive a lower level of thyroid hormone because the increased quantity of TGB binds to the hormones rendering them inactive

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16
Q

Name the 2 main catacholamines and what class of hormones are they in of the big 3? (Of chemical makeup)

A

Epinephrine and norepinephrine and are amino acid derivative hormones

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17
Q

What are amino acid derivative hormones made of? What adjustments are made?

A

They are derived from one or two amino acids, usually with a few modifications like the thyroid hormones are made from tyrosine modified by the addition of several iodine atoms

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18
Q

What is hard about the pathway that amino acid derivative hormones take in inflicting their effects?

A

They are less predictable than the other types of hormones. Rote memorization is advised for this concept.

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19
Q

What length and intensity do the catecholamines and thyroid hormones have?

A

Epinephrine and norepinephrine have extremely fast onset but are short lived, like peptide hormones, think of an adrenaline rush

Thyroxine and triiodothyronine have a slower onset but a longer duration, like steroid hormones, think they regulate metabolic rate over a long period of time

Keep in mind these hormones are ALL amino acid derivative hormones

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20
Q

What do most peptide and amino acid derivative hormones names end in? What about steroid hormones?

A

Peptide and amino acid derivative hormones usually end in (-in, -ine)

Steroid hormones have names that end in (-one, -ol, -oid)

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21
Q

Difference between direct and tropic hormones?

A

Direct hormones are secreted and then act directly on a target tissue

Tropic hormones stimulate the production of another hormone by which it then induces its effects

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22
Q

The hypothalamus secretes hormones where? Where does it go and what is it?

A

It secretes hormones into the hypophyseal portal system, it is a blood vessel system that directly connects the hypothalamus to the anterior pituitary

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23
Q

What structure is known as the bridge between the nervous and endocrine system?

A

The hypothalamus

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24
Q

What part of the hypothalamus receives light signals and what does it do with it?

A

The suprachiasmatic nucleus receives some of the light input from the retinae and helps to control sleep-wake cycles

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25
The hypothalamus contains a number of nuclei in its three sections. Name the 3 sections and list some roles it plays a factor in?
3 sections - lateral, ventromedial, and anterior Roles -emotional experience -aggressive behavior -sexual behavior -metabolism -temperature regulation -water balance
26
What is the release of hormones by the hypothalamus regulated by?
Negative feedback system which occurs when a hormone (or product) later in the pathway inhibits hormones (or enzymes) earlier in the pathway this helps maintain homeostasis and conserve energy A way of self regulation when there is already sufficient quantities present of the product
27
List all the hormones released by the hypothalamus that directly cause the release of hormones in the anterior pituitary. Also list the hormones the hypothalamus causes the release of in the anterior pituitary.
-Gonadotropin-releasing hormone (GnRH) stimulates follicle-stimulating hormones (FSH) and luteinizing hormone (LH) -Growth hormone-releasing hormone (GHRH) stimulates growth hormone (GH) -Thyroid-releasing hormone (TRH) stimulates thyroid-stimulating hormone (TSH) -Corticotropin-releasing factor (CRF) stimulates adrenocorticotropic hormone (ACTH) -Prolactin-inhibiting factor (PIF) which is actually just dopamine, stimulates a DECREASE in prolactin secretion (the one exception in the stimulation pattern)
28
Three organ systems (like the ones involved of the interplay between hormone release and regulation) that are involved in similar productions and regulations of each other are referred to as what? Name a BIG example seen in hormones?
They are called axes Examples: -Hypothalamic-pituitary-adrenal (HPA) axis -Hypothalamic-pituitary-ovarian (HPO) axis
29
How does the hypothalamus cause the posterior pituitary to release hormones? How is it different from the anterior pituitary? What hormones does it release?
It does not use the hypophyseal portal system, instead neurons in the hypothalamus send their axons down the pituitary stalk directly into the posterior pituitary, which can then release the 2 hormones (oxytocin, and antidiuretic hormone (ADH) also called vasopressin)
30
What are the functions oxytocin has?
-stimulates uterine contractions during labor -milk letdown during lactation -also linked in bonding behavior
31
Functions of ADH, when is it released?
Functions to increase reabsorption of water in the collecting ducts of the kidneys. It is released in response to increased plasma osmolarity, or increased concentration of solutes within the blood
32
What does TSH, ACTH, and both FSH, and LH act on? (Structures)
TSH acts on the thyroid ACTH acts in adrenal cortex TSH, and ACTH acts on the gonads (testes, and ovaries)
33
Breakdown the mnemonic FLAT PEG. What does it stand for? What does each word represent?
Represents all the hormones released from the anterior pituitary gland First word FLAT stands for the 4 tropic hormones, PEG stands for the 3 direct hormones Stands for: Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Adrenocorticotropic hormone (ACTH) Thyroid-stimulating hormone (TSH) Prolactin Endorphins Growth hormone (GH)
34
What does prolactin do?
Stimulate milk production in the Mary glands. Milk production in males is always pathologic
35
How does the release of dopamine from the hypothalamus effect prolactin?
When dopamine is released from the hypothalamus, prolactin secretion is decreased
36
What needs to happen for lactation to begin? When does this happen in pregnancy?
It is not until shortly after the expulsion of the placenta, when estrogen, progesterone, and dopamine levels drop, this removed the block in milk production and lactation begins
37
What physical connection causes the release of milk? What process happens?
Nipple stimulation causes activation of hypothalamus, oxytocin is released from the posterior pituitary, resulting in contraction of the smooth muscle of the breast and ejecting the milk through the nipple, also the hypothalamus stops releasing dopamine into the anterior pituitary, allowing prolactin to release and cause production of milk
38
What function do endorphins have?
They decrease the perception of pain
39
What does growth hormone do? What molecule aids it? How does it help increase the quantities it can use of this molecule?
GH promotes the growth bone and muscle, this sort of growth needs a lot of glucose. GH prevents glucose uptake in certain tissues (those not growing) and stimulates the breakdown of fatty acids. This increases the availability of glucose overall, allowing muscle and bone to use it
40
Where does bone growth occur? What effects does too much/little of GH cause in children and in audits?
Bone growth occurs on the epiphyseal plate (closes during puberty) excess of GH in childhood causes gigantism and a deficit causes dwarfism. In adults GH excess can still effect the smaller bones (usually those in the hands, feet, and head) making them bigger, this known as acromegaly
41
What 2 receptors notify the hypothalamus and cause the release of ADH? What is the end goal of this hormone for the body?
Baroreceptors, and osmoreceptors. End goal is to increase blood volume and BP
42
How many hormones does the posterior pituitary synthesize?
None. (ADH, and oxytocin) are actually made in hypothalamus. They are just released in the posterior pituitary gland
43
What type of feedback loop does oxytocin have?
A positive feedback loop. More oxytocin promotes more oxytocin release until ultimately delivery.
44
Where is the thyroid gland located?
On the front of the trachea
45
What hormones does the thyroid make? What is there chemical makeup?
T3 - triiodothyronine (made of 3 iodine atoms attached to a tyrosine) T4 - thyroxine (made of 4 iodine atoms attached to a tyrosine) Calcitonin - made of 32 amino acids
46
What are the 2 major functions of the thyroid?
Setting basal metabolic rate and promoting calcium homeostasis
47
T3 and T4 have what function?
(METABOLISM) They set the basal metabolic rate and are capable of resetting it, altering the utilization of glucose and fatty acids
48
What cells make the thyroid hormones (T3, and T4) and what cells make calcitonin?
Calcitonin is made by C-cells (also called parafollicular cells) in the thyroid Thyroid hormones are made by follicular cells in the thyroid
49
A deficiency vs an excess of thyroid hormone is known as what? What are the symptoms?
Deficiency (could be of iodine) or inflammation of the thyroid maybe result in hypothyroidism- symptoms are lethargy, decreased body temp, slow respirations and HR, cold intolerance, and weight gain Excess is hyperthyroidism and characterized by the opposite of the symptoms above
50
What does calcitonin do? And what ways does it do it? What is it stimulated by?
It decreases the plasma calcium levels in three ways -Increasing calcium excretion from the kidneys -Decreasing calcium absorption from the gut -Increasing storage of calcium in the bone Stimulated by high levels of calcium in the blood
51
Calcium is an exceptionally important ion, name as many important functions of calcium as you can
-bone strength and structure -release of neurotransmitters from neurons -regulation of muscle contractions -clotting of blood (calcium is a cofactor) -cell movement and exocytosis of cellular materials
52
What does the parathyroid gland look like? Where is it? What hormone(s) does it make?
There are 4 parathyroid glands that are small pea sized structures sitting in the posterior surface of the thyroid. It makes PTH (parathyroid hormone)
53
What is PTH function? What does it serve as an antagonist to? (Name all the different things it does
It is an antagonist to calcitonin, therefore it increases serum calcium levels. -PTH promotes phosphorus homeostasis by increasing resorption of phosphate from bone and reducing reabsorption of phosphate in the kidney (thus promoting excretion through urine) - notice how both these processes somewhat cancel each other -PTH also activates vitamin D - which is required for the absorption of calcium and phosphate in the gut
54
Where are the adrenal glands located? What do they secrete? Name all 3 functional classes (hint: the 3 S’s)
They are located by the kidneys and secrete corticosteroids 3 classes: (Sugar, salt, sex) -glucocorticoids -mineralcorticoids -cortical sex hormones
55
What do glucocorticoid play roles in? How do they perform these roles? What are the main hormones?
Main hormones are cortisol, and cortisone. They regulate glucose levels by increasing gluconeogenesis and decreasing protein synthesis. They also decrease inflammation and immunologic responses -cortisol is known as the stress hormones because it is released in times of physical or emotional stress
56
What is the most noteworthy mineralocorticoid, and what does it do, and how does it do it?
Aldosterone is the main one, it increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron. Water follows sodium cations into the bloodstream, increasing blood volume and pressure. (Osmolarity remains unchanged, contrast from ADH) -it also decreases the reabsorption of potassium and hydrogen ions in these segments of the nephron (excreted through urine)
57
Aldosterone is primarily under the control of what system? Describe how this system works systematically? (In order)
Primarily under the control of the renin-angiotensin-aldosterone system -decrease in BP causes the juxtaglomerular cells of the kidney to secrete and enzyme called renin which cleaves and inactive plasma protein called angiotensin often to form its active form angiotensin 1. It is then converted to angiotensin 2 by angiotensin converting enzyme (ACE) in the lungs. Angiotensin stimulates the adrenal cortex to secrete aldosterone -controlled by negative feedback (increase of BP stops the release of renin)
58
Other than angiotensin 2 stimulating the adrenal cortex to make aldosterone how else does it increase blood pressure?
It does it directly through a powerful vasoconstriction effect and increases HR
59
ACE inhibitors would be used for what type of patients? What do these drugs usually end in?
Usually end in -pril. Would be prescribed for hypertensive patients
60
What are examples of the cortical sex hormones. Why is it more alarming in females than males disorder wise?
Examples are androgens and estrogens. Because the testes already make large quantities of androgens, adrenal testosterone plays a small role. For females the ovaries severely far smaller amounts of androgens rendering them more sensitive to disorders in these production of cortical sex hormones -males could be effected by similar disorders if they produce excess estrogen
61
What class of hormones does the adrenal medulla release? List some of these specific hormones and what chemical class of hormones they are.
They are responsible for releasing sympathetic hormones like epinephrine and norepinephrine, these are known as the catecholamines and are amino acid-derivative hormones
62
What does epinephrine do that norepinephrine does not?
It increases the breakdown of glycogen to glucose (glycogenolysis) in both liver and muscles Also increases the basal metabolic rate
63
What do both epinephrine and norepinephrine do?
-Increase heart rate -Dilate the bronchi -Shunt blood flow to the systems that would be used in a sympathetic response (thus vasodilation of blood vessels leading to increased blood flow to skeletal muscles, heart, lungs, and brain. AND decrease blood flow (vasoconstriction) to gut, kidneys, and skin)
64
In terms of longevity and onset how does cortisol and catecholamines work?
Catecholamines are short term but fast onset in response to stress Cortisol mediates long term stress responses with slow onset
65
What does cortisol increase the synthesis of in terms of stress?
The catecholamines
66
Exocrine tissues secrete substances where?
Into ducts
67
Small clusters of hormone producing cells are grouped together into what in the pancreas’s and dispersed throughout it?
The islets of langerhans
68
The islets of langerhands contain what three distinct cell type? What does each cell type release? (Hormones)
Alpha - secretes glucagon Beta - secretes insulin Delta - secretes somatostatin
69
When is glucagon secreted?
During times of fasting (when glucose is low in the blood) -also certain GI hormones (such as cholecystokinin and gastrin) increase glucagon release form alpha cells)
70
How does glucagon increase glucoses production?
By triggering glycogenolysis, gluconeogenesis, and the degradation of protein and fat
71
What is antagonistic to glucagon? When is this hormone secreted and what does it do?
Insulin, its secreted when blood glucose levels are high inducing the muscle and liver cells to take up glucose and store it as glycogen for later use -also insulin stimulates anabolic processes such as fat and protein synthesis
72
Excess insulin causes what condition?
Hypoglycemia
73
What general causes result in diabetes mellitus?
-underproduction -insuffifcient secretion -insensitivity to insulin
74
Hyperglycemia causes what in the kidneys? What does this result in?
Excessive glucose in the filtrate will overwhelm the nephrite ability to reabsorb glucose, resulting in the presence of glucose in the urine
75
Patients who have diabetes often resemble what 2 main symptoms in terms of volume excretion? And why is this?
This is because the presence of glucose in the filtrate leads to excess excretion of water and an increase in the urine volume. Therefore, patients who have diabetes often report polyuria and polydipsia
76
Type 1 diabetes Miletus is caused by what? What do they need?
It’s known as the insulin-dependant type and is caused by autoimmune destruction of the beta cells of the pancreas, resulting in low or absent insulin production -they need regular injections of insulin
77
Type 2 diabetes Miletus is the result of what? What factors play a role in its causation? And when do these patients need insulin?
It is known as the non-insulin-dependent type and is the result of receptor level resistance to the effects of insulin. Type 2 is partially inherited, and partially due to environmental factors, such as high carb diets and obesity They require insulin’s only when their bodies can no longer control glucose level’s
78
What other hormones (other than glucagon) are capable of increasing plasma glucose?
GH, glucocorticoids, and epinephrine They are called counterregulatory hormones
79
What does somatostatin do? What stimulates its secretion? Where is it produced?
It is an inhibitor of both glucagon and insulin, also decreases growth hormone secretion High glucose and amino acid concentrations stimulate its secretion Produced by the hypothalamus
80
What do the testes secrete, also what stimulates them to do so? What does this hormone that they secreted cause?
They secrete testosterone in response to stimulation by gonadotropins (LH, FSH). Testosterone causes sexual differentiation of the male during gestation and promotes development along with maintenance of secondary sex characteristics in makes (axillary and public hair, deepening of the voice, and muscle growth)
81
Ovaries secrete what hormones? Also in response to what? And what do they do?
Ovaries secret estrogen and progesterone in response to gonadotropins. Estrogen is involved in development of the female reproductive system during gestation along with development and maintenance of secondary sex characteristics in females like axillary and pubic hair, breast growth c and body fat redistribution Estrogen and progesterone also govern the menstrual cycle as well as pregnancy
82
Where is erythropoietin secreted? What does it do? And what is it caused by?
It is secreted by the kidneys and stimulates the bone marrow to increase production of ethryocytes (red blood cells) Secreted in response to low oxygen level in the blood
83
The heart releases a hormone called ANP, what does it stand for and what does it do? Also what stimulates its production
It’s called atrial natriuretic peptide and helps regulate salt and water balance promoting excretion of sodium and therefore increases urine volume. (Lowers blood volume and pressure, basically antagonistic of aldosterone) When cells in the atria are stretched from excess blood volume, they cause the release of ANP
84
Where is the thymus located, and what hormone does it release? What effects does it have?
It is located directly behind the sternum, it releases thymosin which is important for proper T-cell development and differentiation Thymus atrophied by adulthood, thus thymosin levels drop

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