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Case 2 > Endocrine Physiology Part I > Flashcards

Endocrine Physiology Part I Flashcards

1
Q

Intercellular Communication

A

Through the bloodstream.
Hormones
Target cells are primarily other tissues and organs and must have appropriate receptors.

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2
Q

What are the several major processes controlled by hormones?

A 
Reproduction
Growth and development
Mobilization of body defenses
Maintenance of much of homeostasis
Regulation of metabolism
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3
Q

What are target cells?

A

Peripheral cells that can respond to a particular
hormone.
Hormones circulate to all tissues but only activate
target cells.

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4
Q

What are receptors?

A

A protein in the cell membrane, or within the
cytoplasm or nucleus.
Target cells must have specific receptors to which
the hormone binds to trigger its action.

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5
Q

What are the major regulatory functions of the endocrine system?

A 
Growth, metabolism, tissue maturation
Blood glucose and other nutrients in blood
Blood ion concentrations (Ca2+, Na+, K+)
Water balance
Heart rate and blood pressure
Immune function
Reproductive function
Uterine contraction and milk release
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6
Q

What is an endocrine gland?

A

It is a ductless gland which secretes hormones directly into the bloodtsream.

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7
Q

What is an exocrine gland?

A

It is a gland which secerets subtances into ducts. It is not part of the endocrine system. substances leave the body (sweat/sebaceous glands) or into an internal space or lumen (digestive glands).

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8
Q

What do ductless glandular epithelial cells do?

A

They secrete hormones into extracellular fluid for transport by the bloodstream.

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9
Q

What are the two groups of endocrine organs?

A

Primary organs - only have endocrine functions.

Secondary organs - have both endocrine and non-endocrine functions.

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10
Q

List the primary endoctine organs.

A 
Anterior pituitary gland
Thyroid gland
Parathyroid gland
Adrenal cortices
Endocrine pancreas
Thymus
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11
Q

What is the position of the anterior pituitary gland?

A

In the sphenoid bone of the skull.

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12
Q

What is the position of the thyroid gland?

A

In anterior neck.

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13
Q

What is the position of the parathyroid gland?

A

On the posterior side of the thyroid gland.

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14
Q

What is the position of the adrenal cortices?

A

On the superior side of each kidney.

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15
Q

What is the position of the endocrine pancreas?

A

In the left side of the abdominal cavity mostly posterior to the stomach.

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16
Q

What is the position of the thymus?

A

In the superior mediatinum.

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17
Q

List some examples of secondary endocrine organs.

A 
Heart
Kidneys
Small intestines
Testes
Ovaries
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18
Q

Outline the neuroendocrine organs.

A

Hypothalamus and pineal gland in the brain and adrenal mudella in the core of the adrenal gland. They consist of vervous tissue but secrete chemicals which act as hormones - neurohormones.

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19
Q

List some general characteristics of hormones.

A

Secreted into the blood
Acts on target cells
Binds to receptors
Potent: needed in very small amounts
Produce long-lasting effects in the target cells
Regulate metabolic processes (maintain homeostasis)
Action must be terminated
Regulated primarily by negative-feedback mechanisms

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20
Q

What are the three groups into which hormones can be classified?

A

Amino acid derivatives
Peptide hormones
Lipid derivatives

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21
Q

List examples of amino acid derivative hormones.

A

Derivatives of tyrosine: thyroid hormones and catecholamines (epinepherine and norepinephrine)
Derivatives of trytophanL dopamine, seratonin and melatonin.

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22
Q

What is the structure of amino acid derivative hormones?

A

Small and structurally related to amino acids.

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23
Q

What is the structure of peptide hormones?

A

Chains of amino acids.

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24
Q

How are peptide hormones sythesised?

A

They are synthesised as prohormones. Inactive molecules converted to active hormones
before or after they are secreted.

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25
Q

List some examples of peptide hormones?

A

Glycoprotiens

Short polypeptides/small proteins

26
Q

Describe glycoproteins?

A

Glycoproteins are more than 200 amino acids long and have carbohydrate side chains. Examples are TSH, LH and FSH.

27
Q

Describe small polypeptides/small proteins

A

Short chain polypeptides: ADH and OXT

Small proteins: GH and PRL

28
Q

What is the structure of lipid derivatives?

A

Steroid hormones derived from cholesterol.

29
Q

Where are lipid derivative formones released?

A

Reproductive organs (androgens by testes and oestrogens and progestins by ovaries)
Cortex of adrenal glans (corticosteroids)
Kidneys (calcitriol)

30
Q

Explain what eicosanoids are.

A

They are lipid derivative hormones but are not derived from cholesterol. They are derived from arachindonic acid (a fatty acid). They include lukotrines and prostaglandins. They are paracrine factors which coordinate cellular activities and affect enzymatic processes (e.g. blood clotting) in ECF.

31
Q

What are the two major classes of hormones?

A

Water soluble - Polar

Lipid soluble - Non-polar

32
Q

Are water soluble hormones hydrophilic or hydrophobic

A

They are hydrophilic. THey are higly water soluble and have a low solubility in lipids. They can thus be transported quickly through the bloodtream.

33
Q

Do water-soluble hormones have a long or short half-life.

A

They have a short half-life.

34
Q

What are some examples of water-soluble hormones?

A

Proteins, peptides and amino acid derivatives.

Amino acid based and molecular size varies (peptides and proteins).

35
Q

Are lipid soluble hormones hydrophilic or hydrophobic?

A

They are hydrophobic. They are highly soluble in lipids and have a low solubility in water.

36
Q

Do lipid-soluble hormones have a long or short half-life?

A

They have a long half-life (60-90 minutes or more).

37
Q

What are some examples of lipid-soluble hormones?

A

Steroids, thyroid hormones and eichsanoids.

38
Q

How are lipid-soluble hormones transported?

A

They are bound to protein carrier molecules in blood. The protein carrier protects the hormone from enzynatic dergradation hence a long half life. Protein carrier dissociates before hormone enters cell.

39
Q

What does the mechanism of hormone action depend on?

A 
Chemical nature (water or lipid soluble)
Cellular location of receptor (on plasma membrane on intracellular)
40
Q

What is the hormone action of water soluble hormones?

A

They act on receptors on the plasma membrane. Coupled via regulatory molecules (G proteins) to
one or more intracellular second messengers.

41
Q

What is the hormone action of water lipid hormones?

A

Steroid and thyroid hormones can act on the plasma membrane or can act on intracellular receptors directly activating genes.

42
Q

How do cell membrane receptors work?

A

Lipophobic ligand cannot enter the cell. It binds to an outer surface receptor for a fast response.

43
Q

How do cytosolic or nuclear receptors work?

A

Lipophillic ligand enters the cell and often activates genes. This is a slower response.

44
Q

What are the two mechanisms hormones act by?

A

Second messenger system (non-steroid hormone action)

Direct gene activation (steroid hormone action)

45
Q

What is the process of non-steroid hormone action (second messenger system)?

A 
Hormone binds receptor on
cell membrane and acts as
first messenger
Result is either increase or
decrease in some second
messenger
Second messenger
activates protein cascade,
leading to cellular changes
Commonly G-protein
regulated using cyclic AMP
as the second messenger
46
Q

What is the process of steroid hormone action (direct gene activation)?

A

Most hyrdophobic steroids are bound to protein carriers and must unbind befored diffusing into the target cell. Steroid hormone receptors are found in the cytoplasm or nucleus. The receptor hormone complex (lock-key) binds to DNA and activates or represses one or more genes causing the formation of new mRNA and hence translation produces new proteins for cell processes. Some steroid hromones bind to membrane receptors which sue second messenger systems to create a rapid cellular response.

47
Q

What are the two different types of receptor numbers?

A

Down Regulation

Up Regulation

48
Q

What is down regulation?

A

Presence of hormone triggers a decrease in the
number of hormone receptors
Cells become less sensitive to the hormone
Prevents cell from overreacting to high hormone
levels

49
Q

What is up regulation?

A

Absence of a hormone triggers increase in number of hormone receptors
Cells become more sensitive to low levels of
hormone

50
Q

Do hormones follow a specific pattern of release?

A

Yes. They follow a circadian rhythm (a pattern over a 24 hour period). This is usually linked to day and night. E.g. cortisol levels rise at night and are highest in the morning, falling through the day.

51
Q

What are blood hormone levels determined by?

A

The rate of secretion
The rate of metabolic activation or conversion
Mode of transport
Excretion
Inactivation - binding to cell receptos; removal by liver or kidney cells; breakdown by extracellular enzymes

52
Q

What are the categories into which stimuli that endocrine glands fall into?

A

Hormonal
Humoral
Neural

53
Q

Outline hormonal stimulus.

A

Endocrine organs are activated by other hormones. This is the most common stimulus. Examples include the anterior pituitary gland which produces hormones which stimulate the thyroid gland, adrenal cortex and gonads.

54
Q

Outline humoral stimulus.

A

Changing levels of certain ions and nutrients stimulate hormone release. Examples include the parathyroid hormone and calcitonin which are produced in response to changing levels of blood calcium levels. Insulin also responds to changes in blood glucose levels.

55
Q

Outline neural stimulus.

A

Nerve impulses stimulate hormone release (mostly the sympathetic nervous system). An example is the release of epinephrine and nroepinephrine by the adrenal medulla.

56
Q

What are the different types of hormone effects/interactions?

A

Permissive Effect
Synergistic Effect
Antagonistic Effect

57
Q

Outline the permissive effect.

A

One hormone cannot fully exert its effect unless a second hormone is present, One hormone may enhance the responsiveness of a target tissue to a second hormone or may increase the activity of a second hormone

58
Q

Give an example of the permissive effect.

A

Reproductive and thyroid hormones - Maturation of reproductive system delayed if reproductive hormones are present but thyroid hormones not present.

59
Q

Outline the synergistic effect.

A

Two or more hormones interact. Their combined effect is greater than the sum of each individual effect. An example is a combination of glucagon, cortisol and epinephrine.

60
Q

Outline the anatgonistic effect.

A

One hormone diminishes the effect of another. An example is insulin which opposes the effect of glucagon.

61
Q

How do anatgonistic hormones work?

A

They may compete for the same receptor.
They may act through different metabolic pathways.
They may down-regulate receptors.

62
Q

What are the effects of hormone stimulation?

A

Alter membrane potential or plasma membrane permeability
Stimulate synthesis of proteins or regulatory molecules e.g. enzymes
Activate or deactivate enzymes
Induce secretoryactivity
Stimulate mitosis

Case 2 (5 decks)

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