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Kin 267 (Phys. 1) > Endocrine System (Pt. 1) > Flashcards

Endocrine System (Pt. 1) Flashcards

1
Q

What two systems make up our body’s ‘communication system’?

A

The nervous system and the endocrine system

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2
Q

What is the “President” of the endocrine system?

A

The hypothalamus

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3
Q

What is the “Vice-President”

A

The pituitary gland

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4
Q

What does the endocrine system release to communicate?

A

Hormones

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5
Q

Define hormones in the context of the endocrine system

A

Hormones are substances secreted into the bloodstream which stimulate a response in another cell, tissue or organ

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6
Q

How does the nervous system communicate?

A

Quickly, using nerve impulses and neurotransmitters at synapses

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7
Q

How does the endocrine system communicate?

A

By releasing hormones that travel through the bloodstream to regulate activities in different body parts

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8
Q

What are the characteristics of hormones?

A

Released in one part of the body, regulate cells in another, Enter the bloodstream and affect target cells by binding to their receptor

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9
Q

Can some substances act as both neurotransmitters and hormones?

A

Yes, for example, norepinephrine can act as both

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10
Q

How fast are endocrine responses typically?

A

Generally slower, taking minutes or more

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11
Q

How fast are nervous system responses typically?

A

Quick but typically brief

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12
Q

How specific are the targets of the nervous system compared to the endocrine system?

A

The nervous system targets specific muscles and glands, while the endocrine system influences many body cells

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13
Q

Do the nervous and endocrine systems interact?

A

Yes, the nervous system can influence hormone release

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14
Q

List the main endocrine glands in the body.

A

Pituitary, thyroid, parathyroid, adrenal (suprarenal), and pineal glands

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15
Q

Can organs and tissues that are not part of the endocrine system secrete hormones?

A

Yes, if they contain secreting cells

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16
Q

Name at least 5 organs or tissues that contain hormone-secreting cells but are not primarily endocrine glands.

A

Any 5 of: hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart, adipose tissue, placenta

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17
Q

What are exocrine glands?

A

Glands that secrete products into ducts and deliver secretions to body cavities, organ lumens, or the body’s outer surface

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18
Q

Give examples of exocrine glands.

A

Sudoriferous (sweat), sebaceous (oil), mucous, and digestive glands

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19
Q

How do endocrine glands secrete hormones?

A

They secrete hormones directly into interstitial fluid, which then diffuse into blood capillaries

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20
Q

What is a characteristic of endocrine glands related to blood supply?

A

They are extremely vascular, relying on the cardiovascular system for hormone distribution

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21
Q

What is typically true about hormone levels in circulation?

A

They are typically low

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22
Q

What is the study of the structure, function, and disorders of endocrine glands called?

A

Endocrinology

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23
Q

How do most hormones exert their effects?

A

They circulate in the blood and bind to receptors on target cells.

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24
Q

What determines the specificity of hormone-receptor interaction?

A

Each hormone has specific receptors; only the correct hormone will “fit” the correct receptor.

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25
Q

How many receptors can a single cell have?

A

Between 2,000 to 100,000 specific receptors.

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26
Q

What factors influence how a target cell responds to a hormone?

A
  • Hormone concentration in the blood
  • Number of hormone receptors on the target cell
  • Influences from other hormones (permissive effects)
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27
Q

What is the permissive effect of hormones?

A

Some hormones require another hormone’s presence for full effectiveness.

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28
Q

Give an example of a synergistic effect among hormones.

A

Glucagon and epinephrine together increase blood glucose levels more than either hormone alone.

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29
Q

What is an antagonistic effect?

A

One hormone counteracts the action of another, such as insulin (which promotes glycogen synthesis) vs. glucagon (which stimulates glycogen breakdown).

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30
Q

How does receptor abundance influence hormone response?

A

More receptors on target cells (up-regulation) enhance sensitivity to the hormone.

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31
Q

What is an example of how certain hormones work together?

A

Epinephrine’s effect on lipolysis is amplified by the presence of thyroid hormones (T3 and T4).

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32
Q

How does hormone concentration affect cell response?

A

Higher hormone levels in the blood lead to a stronger response from target cells.

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33
Q

What is the ongoing process for hormone receptors?

A

Receptors are continually being synthesized and broken down

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34
Q

What is receptor down-regulation?

A

When receptors become less sensitive (less effect) in the presence of high hormone concentrations

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35
Q

Give an example of receptor down-regulation.

A

Insulin receptors in type 2 diabetes

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36
Q

What is receptor up-regulation?

A

When receptors become more sensitive (more effect) in the presence of low hormone concentrations

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37
Q

Give an example of receptor up-regulation.

A

Testosterone receptors with aging

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38
Q

Give an example of hormone-induced down-regulation.

A

High levels of luteinizing hormone (LH) can lead to a reduction in LH receptors in certain testicular cells

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39
Q

What happens in up-regulation when there’s a hormone deficiency?

A

The number of receptors may increase, enhancing the cell’s sensitivity to that hormone

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40
Q

Explain the process of circulating hormones:

A

endocrine cells release hormones into the bloodstream. These hormones travel through blood capillaries to reach distant target cells, where they bind to specific hormone receptors, triggering a response.

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41
Q

What are hormones that act on nearby cells called?

A

Paracrines

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42
Q

Give an example of a paracrine hormone and its action

A

Interleukin-2 (IL-2) produced by T cells, which helps activate other nearby immune cells

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43
Q

What are hormones that act on the same cell that secretes them called?

A

Autocrines

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44
Q

Provide an example of autocrine signaling.

A

Interleukin-2 (IL-2) stimulating the T cell that produced it to generate more T cells

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45
Q

How do circulating hormones differ from local hormones?

A

Circulating hormones enter the bloodstream to affect the whole body, while local hormones act near their origin without entering the blood

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46
Q

What is an example of a local hormone?

A

Nitric oxide (NO)

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47
Q

What effect does nitric oxide have on blood vessels?

A

It relaxes nearby muscles, leading to vasodilation (increased vessel diameter), affecting blood pressure and contributing to penile erection

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48
Q

What are the two main categories of hormones based on solubility?

A

Lipid-soluble hormones and water-soluble hormones

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49
Q

List four types of lipid-soluble hormones.

Hint: S.T.N.E

A

Steroid hormones, thyroid hormones, nitric oxide, and eicosanoids

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50
Q

What are two main types of water-soluble hormones?

A

Amine hormones and peptide/protein hormone

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51
Q

How do water-soluble hormones circulate in the blood?

A

They circulate freely

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52
Q

How do water-soluble hormones interact with target cells?

A

They must bind to cell-surface receptors on the plasma membrane and need help from ‘messengers’

53
Q

What are steroid hormones derived from?

A

Cholesterol

54
Q

What makes thyroid hormones (T3 and T4) unique among lipid-soluble hormones?

A

They contain iodine, making them highly lipid-soluble

55
Q

Name three examples of amine hormones

A

Catecholamines (epinephrine, norepinephrine, dopamine), histamine, serotonin, and melatonin

56
Q

What’s the difference between peptide and protein hormones?

A

Peptide hormones have 3-49 amino acids, while protein hormones have 50-200 amino acids

57
Q

Give examples of peptide and protein hormones.

A

Peptide: antidiuretic hormone, oxytocin. Protein: growth hormone, insulin

58
Q

How do most lipid-soluble hormones circulate in the blood?

A

Bound to transport proteins made in the liver

59
Q

List three functions of transport proteins for lipid-soluble hormones.

A
  1. Make lipid-soluble hormones temporarily water soluble
  2. Slow the passage of small hormones to the kidney for excretion
  3. Provide a reserve for hormones in blood

Note: soluble, passage, reserve

60
Q

What percentage of lipid-soluble hormones are typically free in the blood?

A

About 10%

61
Q

How do free lipid-soluble hormones interact with target cells?

A

They penetrate the plasma membrane and typically enter the nucleus to cause a reaction

62
Q

How do lipid-soluble hormones enter target cells?

A

They diffuse from the blood through the cell’s plasma membrane

63
Q

Where do lipid-soluble hormones bind in target cells?

A

To receptors in the cytosol or nucleus

64
Q

How do lipid-soluble hormones alter gene expression?

A

The receptor-hormone complex turns specific DNA genes on or off, leading to mRNA creation

65
Q

What happens after mRNA is created in response to lipid-soluble hormones?

A

mRNA moves to the cytoplasm, guiding ribosomes to make new proteins

66
Q

How do the new proteins affect the cell?

A

They modify the cell’s activity, generating the hormone’s intended response

67
Q

Do all lipid-soluble hormones bind inside the cell?

A

No, eicosanoids bind to receptors on the cell’s surface, similar to water-soluble hormones

68
Q

what percent of hydrophobic (lipid soluble) hormones are free in the blood?

A

10 %

69
Q

How does free lipid-soluble hormone move from the blood to the target cell?

A

It diffuses from the capillary into interstitial fluid, then across the plasma membrane

70
Q

Where does a lipid-soluble hormone typically bind in the target cell?

A

With a receptor, often in the nucleus

71
Q

What is the immediate effect of a lipid-soluble hormone binding to its receptor?

A

It causes gene expression

72
Q

What happens to DNA in response to lipid-soluble hormone binding?

A

DNA is transcribed to mRNA

73
Q

How does the cell produce new proteins in response to lipid-soluble hormones?

A

mRNA and ribosomes make new proteins

74
Q

How does a water-soluble hormone (1st messenger) reach its target cell?

A

It diffuses from the capillary into interstitial fluid, then to the receptor on the plasma membrane

75
Q

What happens when a water-soluble hormone binds to its receptor?

A

It activates G proteins, which then activate adenylyl cyclase

76
Q

What does adenylyl cyclase do?

A

It converts ATP to cAMP (2nd messenger)

77
Q

What is the role of cAMP in the cell?

A

cAMP activates many protein kinases

78
Q

What do protein kinases do?

A

They add phosphate groups to proteins

79
Q

What is the effect of phosphorylated proteins?

A

They stimulate many cellular reactions

80
Q

What enzyme inactivates cAMP?

A

Phosphodiesterase

81
Q

Why is it important that cAMP is inactivated?

A

To get the cell ready for the next response from the hormone

82
Q

Why can’t water-soluble hormones cross the cell membrane?

A

They are not lipid-soluble, so they can’t pass through the lipid bilayer

83
Q

What is the role of G proteins in water-soluble hormone action?

A

They are activated by the hormone-receptor complex and stimulate adenylyl cyclase

84
Q

Why is cAMP called a “Second Messenger”?

A

It transmits the signal from the hormone-receptor binding (first messenger) inside the cell to initiate the cellular response

85
Q

What is the amplification mechanism in hormone signaling?

A

A single hormone-receptor interaction can activate numerous G proteins, leading to a cascade effect that massively amplifies the initial signal

86
Q

What is the result of the amplification mechanism?

A

It results in a significant cellular response

87
Q

Name some other examples of second messengers besides cAMP

A

Calcium ions, cGMP, IP3, and DAG

88
Q

What determines which second messenger is used in hormone signaling?

A

It depends on the specific hormone and target cell type

89
Q

In the context of hormone signaling, what is considered the “first messenger”?

A

The hormone-receptor binding on the cell surface

90
Q

How does cAMP contribute to signal amplification?

A

By activating multiple protein kinases, which can then phosphorylate many proteins, leading to a cascade of cellular reactions

91
Q

How are hormones typically released?

A

In short bursts, with secretion increasing when an endocrine gland is stimulated and decreasing in the absence of stimulation

92
Q

What is the purpose of regulated hormone release?

A

To ensure balanced hormone levels for maintaining homeostasis

93
Q

List the three main mechanisms of hormone secretion control.

A
  1. Nervous system signals
  2. Chemical changes in the blood 3. Other hormones
94
Q

Give an example of nervous system control of hormone release.

A

Nerve impulses to the adrenal medulla regulate the release of epinephrine

95
Q

Provide an example of one hormone controlling the release of another.

A

Adrenocorticotropic hormone (ACTH) from the anterior pituitary stimulates cortisol release from the adrenal cortex

96
Q

What type of feedback mechanism is most commonly used in hormone regulation?

A

Negative feedback

97
Q

Why is negative feedback used in hormone regulation?

A

To prevent overproduction of hormones

98
Q

Give an example of a hormone system that uses positive feedback

A

Oxytocin during childbirth

99
Q

What is the purpose of positive feedback in hormone regulation?

A

To enhance the response

100
Q

What is the primary mechanism for most hormone regulation?

A

Negative feedback

101
Q

Why are negative feedback loops important in hormone regulation?

A

They prevent excessive fluctuations in hormone levels, which can lead to disorders

102
Q

Give an example of how hormone imbalance can affect health

A

Too little insulin leads to high blood sugar (diabetes), while too much can cause hypoglycemia (low blood sugar)

103
Q

What is the main purpose of negative feedback in the body?

A

To maintain a stable internal environment despite external changes, promoting overall health and function

104
Q

In a blood pressure regulation example, what detects changes in blood pressure?

A

Receptors in blood vessels

105
Q

What acts as the control center in the blood pressure regulation example?

A

The brain

106
Q

What are the effectors in the blood pressure regulation example?

A

The heart and blood vessels

107
Q

How do effectors respond to high blood pressure in this example?

A

The heart rate decreases and blood vessels dilate

108
Q

What is the end result of this negative feedback loop?

A

A reduction in blood pressure and a return to homeostasis

109
Q

How does negative feedback contribute to overall bodily function?

A

It helps maintain homeostasis, or a stable internal environment

110
Q

How common is positive feedback in hormone regulation?

A

Only a few hormones operate via positive feedback

111
Q

What types of processes are positive feedback loops ideal for?

A

Processes that need to be decisively completed once initiated, often involving rapid and irreversible changes

112
Q

How does positive feedback differ from negative feedback in terms of system stability?

A

Unlike negative feedback which maintains stability, positive feedback thrusts the system toward a culmination

113
Q

In the childbirth example, what initiates the positive feedback loop?

A

The stretching of the cervix as the baby moves down the birth canal

114
Q

What detects the cervix stretching during childbirth?

A

Stretch-sensitive nerve cells in the cervix

115
Q

What hormone does the brain release in response to cervix stretching?

A

Oxytocin

116
Q

What is the target of oxytocin during childbirth?

A

The muscles of the uterine wall

117
Q

How does oxytocin affect uterine muscles?

A

It causes them to contract more forcefully

118
Q

How do stronger contractions contribute to the positive feedback loop?

A

They push the baby further down the birth canal, increasing the stretching of the cervix

119
Q

What interrupts the positive feedback loop in childbirth?

A

The birth of the baby, which stops the stretching of the cervix and breaks the cycle

120
Q

What are the three main steps in how negative feedback works?

A
  1. Detection of change
  2. Hormone secretion adjustment
  3. Return to set point
121
Q

How does the endocrine system respond to high hormone levels in negative feedback?

A

The glands reduce hormone output

122
Q

In the thyroid hormone example, what hormone does the hypothalamus release?

A

Thyrotropin-releasing hormone (TRH)

123
Q

What hormone does TSH stimulate the thyroid gland to produce?

A

Thyroid hormones (T3 and T4)

124
Q

How do insulin and glucagon work together in blood sugar regulation?

A

Insulin lowers blood sugar when it’s high, while glucagon raises it when it’s low

125
Q

What is the main difference between negative and positive feedback?

A

Positive feedback amplifies changes, while negative feedback reduces them

126
Q

What are two key characteristics of positive feedback?

A

Amplification and a self-enhancing cycle

127
Q

How does oxytocin contribute to positive feedback during childbirth?

A

It stimulates uterine contractions, which trigger more oxytocin release, intensifying contractions

128
Q

Give an example of positive feedback in blood clotting.

A

Platelets adhere to a damaged site and release chemicals attracting more platelets, continuing until a clot forms

129
Q

Why is positive feedback less common in the body’s regulatory systems?

A

It’s used only in specific situations where a rapid outcome is needed

Kin 267 (Phys. 1) (14 decks)

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