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Patho 2 > 1 - Endocrine Physiology > Flashcards

1 - Endocrine Physiology Flashcards

1
Q

What are neurotransmitters?

A

released by axon terminals of neurons into the synaptic junction

act locally to control nerve cell functions

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2
Q

What are endocrine hormones?

A

released by glands or specialized cells into the circulating blood

influence the function of target cells at another location in the body

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3
Q

What are neuroendocrine hormones?

A

secreted by neurons into the circulating blood

influence the function of target cells at another location in the body

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4
Q

What are paracrines?

A

secreted by cells into the ECF to affect neighboring target cells of a different type

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5
Q

What are autocrines?

A

secreted by cells into the ECF

affect the function of the SAME CELL that produced them

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6
Q

What are cytokines?

A

peptides secreted by cells into the ECF

function as autocrines, paracrines, or endocrines

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7
Q

Thyroxine has what effect on most of the body’s cells?

A

Increased rate of chemical reactions

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8
Q

What are the three classes of hormones?

A

Proteins and polypeptides

Steroids

Amino Acid Tyrosine Derivatives

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9
Q

Which class of hormone doe the majority of hormones in the body belong to?

A

polypeptides and proteins

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10
Q

What’s the difference between a protein and a peptide?

A

Just a difference of size

Proteins are composed of 100+ amino acids

peptides are composed of < 100 amino acids

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11
Q

Where are protein and peptide hormones synthesized?

A

The rough ER, just like all other proteins

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12
Q

Describe the genesis of a protein hormone in the cell

A
  1. Produced in the rough ER as a larger protein that is not biologically active (preprohormone)
  2. In the ER it is cleaved into a prohormones
  3. Prohormones are transferred to the golgi for packaging into vessicles
  4. Enzymes in the vessicles cleave the prohormone into biologically active hormones and inactive fragments
  5. Vesicle is stored in the cytoplasm until stimulated for exocytosis by calcium or cAMP
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13
Q

Are peptide hormones water or fat soluble?

A

Water soluble

can easily enter the circulatory system

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14
Q

Steroid hormones are synthesized from ___________

A

cholesterol

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15
Q

Are steroid hormones water or lipid soluble?

A

lipid soluble

can simply diffuse across the cell membrane into the interstitial fluid and the plasma

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16
Q

How are steroids stored?

A

They aren’t

BUT

large stores of cholesterol esters ARE stored in the cytoplasm vacuoles and the cells can use these to rapidly synthesize steroids

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17
Q

Amine steroids are derived from _______

A

tyrosine

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18
Q

The two groups of amine hormones are synthesized in the:

A

adrenal medulla

thyroid

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19
Q

Epinephrine and Norepinephrine are _____ hormones and are formed in the _________

A

Amine

Adrenal Medulla

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20
Q

Which does the adrenal medulla secrete more of: epinephrine or norepinephrine?

A

four times more epinephrine

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21
Q

How are the catecholamines stored and released from the adrenal medulla?

A

Just like peptides: stored in vesicles and released by exocytosis

22
Q

The concentrations of circulating hormones are extremely _____

A

low

23
Q

Most hormonal regulation is controlled by ______ feedback

A

negative

24
Q

How are peptides and catecholamines circulated in the blood?

A

Water soluble

dissolve in the plasma and are transported

25
Q

How are steroid and thyroid hormones transported in the blood?

A

Lipid soluble

mainly circulate bound to plasma proteins

More than 99% of thyroxine in the blood is bound to plasma proteins!

26
Q

How do protein-bound hormones diffuse?

A

Since they can’t easily diffuse, the large amount of hormone that is bound to proteins serves as a resevoir

when the concentration of free hormone decreases, hormone is able to detach and diffuse into the plasma to replenish the circulating concentration

27
Q

The concentration of hormone in the blood is determined by:

A

the rate of hormone secretion into the blood

the metabolic clearance rate

28
Q

How is metabolic clearance calculated?

A

rate of disappearance / concentration of hormone

29
Q

What are the four ways hormones are cleared from the body?

A
  1. Metabolic destruction by tissues
  2. Binding with tissues
  3. Excretion by the liver into the bile
  4. Excretion by the kidneys into the urine
30
Q

How are peptides and catecholamines cleared?

A

Rapidly. Short half-life.

Usually degraded by enzymes in the blood and tissue then excreted by the kidneys and liver

31
Q

How are protein-bound hormones cleared?

A

Slowly. Several hours or even days.

32
Q

Hormone receptors may be located in: (3)

A

the cell membrane

the cytoplasm

the nucleus

33
Q

Most hormones that open or close ion channels do so by:

A

coupling with G protein-linked or enzyme linked receptors

not the ion channel itself

34
Q

Explain the sequence of G protein activation by a hormone

A
  1. the hormone binds to the extracellular side of the receptor
  2. The intracellular side of the receptor phosphorylates GDP into GTP, causing the alpha unit of the G protein to dissociate from the beta and gamma subunits.
  3. The alpha subunit is the active portion. It goes off and interacts with the target protein as an enzyme
  4. When the hormone is removed, the receptor takes back its phosphate group and the two subunits reattach to the alpha subunit, inactivating it
35
Q

What are enzyme-linked hormone receptors?

A

receptor protein that either functions as the enzyme or is directly catalytic

the receptor is doing the work the hormone triggers. It’s not just signalling to another part of the cell.

36
Q

What receptor is a widely-used enzyme linked hormone receptor?

A

Tyrosine Kinase!

VEGF, inslin, ILGF, growth hormone and several others use these receptors

37
Q

Describe the adenyl cyclase - cAMP system

A
  1. Hormone binds with G protein receptor
  2. A subunit binds with adenylyl cyclase
  3. Adenylyl cyclase converts ATP into cAMP
  4. cAMP activates cAMP dependent protein kinase
  5. Prokein kinase does the work
38
Q

Catecholamine alpha receptors use the ___ second messenger system

Catecholamine Beta receptors use the ____ second messenger system

A

Phospholipase C

Adenylyl Cyclase - cAMP

39
Q

Which second messenger system operates in response to entry of calcium into the cell?

A

Calcium-Calmodulin

40
Q

Name one example of calcium-calmodulin action

A

myosin light chain kinase for muscle contraction in smooth muscle

41
Q

calmodulin is very similar to ________, its skeletal muscle counterpart

A

troponin C

42
Q

How does aldosterone cause sodium reabsorption and potassium secretion in the tubules?

A

It enters the cytoplasm of the tubular cells

Binds with mineralocorticoid receptor in the cytoplasm

Combined compound is transported to the nucleus

binds at specific points on the DNA and activates transcription of sodium and potassium transport proteins

43
Q

What are the two unique ways thyroid hormones effect the nucleus?

A
  1. Activate genetic mechanism to synthesize multiple (100+) proteins that serves to ramp up metabolic activity in virtually all cells
  2. Once bound the the nucleic receptors, the thyroid hormone stays bound for days or even weeks
44
Q

Low concentrations hormone increase the number of receptors per cell. This is known as:

A

upregulation

45
Q

High concentrations of hormones decrease the number or affinity of receptors. This is called:

A

downregulation

46
Q

Which type of hormone diffuses easily across the cell membrane: water soluble or lipid soluble?

A

Lipid soluble

Water soluble hormones are polarized and have a high molecular weight. Most of them require receptors.

Lipid soluble steroids diffuse freely across the membranes

47
Q

What are the four second messenger systems?

A
  1. cAMP
  2. cGMP
  3. IP3 - DAG
  4. Tyrosine Kinase
48
Q

Lipid-soluble homrones are synthesized from cholesterol. The only exception is:

A

thyroid hormones

49
Q

If steroids can diffuse across the cell membrane freely, what keeps them from diffusing back out before causing any sort of effect?

A

They bind with cytosolic or nuclear receptors

50
Q

What is the difference between direct and permissive effects of hormones?

A

Direct effects change the cell’s function from one thing to another

Permissive effects don’t change the actions of the cell, just make they cell do those actions more efficiently and at a greater rate etc.

51
Q

What is the neuroendocrine system?

A

the integration of the neural and endocrine systems

namely, the hypothalamic pituitary axis

Patho 2 (24 decks)

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