Advanced Pathophysiology > Endocrine System > Flashcards

Endocrine System Flashcards

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1
Q

What are the main functions of the endocrine system?

A
  • Guides brain and reproductive organ development in the fetus
  • Controls growth and development during childhood and adolescence
  • Coordinates male and female reproductive systems for reproduction
  • Maintains a stable internal environment throughout life
  • Helps the body adapt and respond to emergencies or stress

These functions highlight the endocrine system’s role in overall body regulation.

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2
Q

Define autocrine signaling.

A

A cell releases a hormone that acts on itself

This is one of the three types of hormone signaling.

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3
Q

Define paracrine signaling.

A

Hormones act on nearby cells

This is one of the three types of hormone signaling.

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4
Q

Define endocrine signaling.

A

Hormones travel through the blood to distant target cells

This is one of the three types of hormone signaling.

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5
Q

What are the patterns of hormone secretion?

A
  • Diurnal: follows a daily cycle
  • Pulsatile or cyclic: released in bursts
  • Substrate-dependent: changes based on blood levels of substances

These patterns influence how hormones are released and their effects.

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6
Q

What is negative feedback in hormone regulation?

A

High hormone levels stop further release

This is the most common feedback mechanism in hormonal regulation.

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7
Q

What is positive feedback in hormone regulation?

A

Hormone release increases further secretion

This mechanism is less common and often involved in processes like childbirth.

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8
Q

What triggers the release of hormones?

A
  • Chemical factors (e.g., blood glucose)
  • Endocrine factors (e.g., TSH controlling another gland)
  • Neural control (e.g., nerve signals stimulating secretion)

These factors ensure proper timing and balance of hormone actions.

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9
Q

What are water-soluble hormones?

A

Hormones that circulate freely and act quickly

Examples include insulin.

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10
Q

What are lipid-soluble hormones?

A

Hormones that bind to carrier proteins and have longer half-lives

Examples include cortisol and thyroid hormones.

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11
Q

What is the half-life of water-soluble hormones?

A

Seconds to minutes

Example: insulin lasts 3–5 minutes before breakdown.

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12
Q

What is the half-life of lipid-soluble hormones?

A

Hours to days

They remain in blood longer because they bind to carrier proteins.

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13
Q

What is the role of binding proteins for lipid-soluble hormones?

A

Keep hormones stable in circulation

If binding proteins drop, hormone levels may fall, causing deficiency symptoms.

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14
Q

What are the two key functions of hormone receptors?

A
  • Recognize and bind specifically to their hormone
  • Activate intracellular signals to cause a cellular response

The number and strength of receptors determine cell sensitivity to hormones.

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15
Q

What is up-regulation?

A

Low hormone levels increase receptor number or sensitivity

This allows cells to adjust their response to hormone levels.

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16
Q

What is down-regulation?

A

High hormone levels decrease receptor number or sensitivity

This allows cells to adjust their response to hormone levels.

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17
Q

Where are water-soluble hormone receptors located?

A

On the cell membrane

They cannot cross the membrane and bind to surface receptors.

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18
Q

Where are lipid-soluble hormone receptors located?

A

Inside the cytoplasm or nucleus

They can cross the cell membrane and directly influence gene expression.

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19
Q

What are direct effects of hormones?

A

Immediate changes caused by a hormone acting on its target cell

Example: Insulin promotes glucose uptake by muscle and fat cells.

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20
Q

What are permissive effects of hormones?

A

One hormone enhances the action of another

Example: Thyroid hormone increases the number of epinephrine receptors.

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21
Q

What is the Hypothalamic–Pituitary Axis (HPA)?

A

Links the nervous and endocrine systems, controlling vital body functions

It regulates hormone secretion in the body.

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22
Q

What hormones does the hypothalamus produce?

A
  • TRH
  • GnRH
  • GHRH
  • Somatostatin
  • CRH
  • PIH (Dopamine)
  • PRH
  • ADH
  • Oxytocin

These hormones control pituitary hormone secretion.

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23
Q

What is the function of ADH (antidiuretic hormone)?

A

Maintains water balance and plasma osmolality

It increases water reabsorption in kidney tubules.

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24
Q

What is the function of Oxytocin?

A

Causes uterine contractions during labor and milk ejection during breastfeeding

It also helps prevent postpartum bleeding.

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25
What does the **thyroid gland** control?
The body’s metabolic rate ## Footnote It plays a crucial role in energy balance and metabolism.
26
What do **follicular cells** in the thyroid gland do?
Synthesize thyroid hormones and secrete them into the bloodstream ## Footnote They are essential for regulating metabolism.
27
What is the role of **calcitonin**?
Helps maintain calcium balance and lowers blood calcium levels ## Footnote It is used to treat osteoporosis and hypercalcemia.
28
How is **thyroid hormone secretion** regulated?
Through a negative feedback loop between the hypothalamus, pituitary, and thyroid ## Footnote High TH levels inhibit TRH and TSH release.
29
What regulates **Thyroid Hormone Secretion**?
A negative feedback loop between the hypothalamus, pituitary, and thyroid ## Footnote TRH from the hypothalamus stimulates the pituitary to release TSH, which stimulates the thyroid to release T3 and T4.
30
What does **TSH** do?
* Increases thyroid hormone release from stored colloid * Stimulates iodide uptake and oxidation * Promotes synthesis of new thyroid hormone * Stimulates thyroid growth through cell enlargement and division ## Footnote TSH is crucial for thyroid function and hormone production.
31
List the steps in **Thyroid Hormone Synthesis**.
* Thyroglobulin is made in follicular cells * Tyrosine is incorporated into thyroglobulin * Iodide is actively transported into the follicle * Iodide is oxidized and binds to tyrosine * Coupling forms T3 and T4 * T3 and T4 remain stored in colloid until released into blood ## Footnote These steps are essential for the production of thyroid hormones.
32
What percentage of thyroid hormones produced is **T4** and **T3**?
* 90% T4 * 10% T3 ## Footnote T4 is converted to T3 in tissues, which is more potent.
33
What are the **actions of thyroid hormones**?
* Increase metabolic rate * Increase oxygen use * Increase heat production * Essential for growth and brain development * Affect protein, fat, and carbohydrate metabolism * Regulate heart rate, respiration, skin, hair, and bone health ## Footnote Thyroid hormones play a vital role in overall metabolism and health.
34
What effect does **T3** have on the heart?
Increases heart rate and cardiac output ## Footnote T3 is crucial for maintaining cardiovascular function.
35
What do the **parathyroid glands** produce?
Parathyroid hormone (PTH) ## Footnote PTH is the main regulator of blood calcium levels.
36
What are the actions of **PTH**?
* Stimulates osteoclast activity to release calcium into blood * Increases calcium reabsorption in kidneys * Works with vitamin D to enhance calcium absorption in intestines ## Footnote PTH plays a critical role in calcium homeostasis.
37
What is the role of **Vitamin D₃ (calcitriol)**?
Enhances calcium absorption ## Footnote It is activated in the kidneys and works closely with PTH.
38
What is **PTHrP**?
Parathyroid Hormone–Related Protein ## Footnote Acts locally and has effects similar to PTH, important for bone formation and remodeling.
39
What is the **endocrine function** of the pancreas?
Regulates glucose, fat, and protein metabolism ## Footnote The pancreas has both endocrine and exocrine functions.
40
What are the **islet cell types** in the pancreas?
* Alpha cells: secrete glucagon * Beta cells: secrete insulin and amylin * Delta cells: secrete somatostatin * F (PP) cells: secrete pancreatic polypeptide ## Footnote Each cell type has a specific role in glucose metabolism.
41
What triggers **insulin secretion**?
* Rising blood glucose * Parasympathetic input * Selected amino acids * Gut hormones ## Footnote Insulin secretion is inhibited by hypoglycemia and sympathetic drive.
42
What are the **core actions of insulin**?
* Promotes glucose uptake in muscle, fat, and liver * Stimulates glycogen, protein, and fat synthesis * Supports cellular uptake of K⁺, phosphate, and magnesium ## Footnote Insulin has significant anabolic effects on metabolism.
43
What is the effect of **glucagon**?
Raises blood glucose during fasting, exercise, and hypoglycemia ## Footnote It is stimulated by low glucose and certain amino acids.
44
What does **somatostatin** do?
Inhibits secretion of insulin, glucagon, and pancreatic polypeptide ## Footnote It modulates islet balance and fine-tunes metabolism.
45
What are **incretins**?
* GIP * GLP-1 ## Footnote They enhance glucose-dependent insulin secretion and suppress glucagon.
46
What do **catecholamines** do?
* Bind to α₁, α₂, β₁, β₂, β₃ receptors * Activate adenylyl cyclase * Produce the 'fight or flight' response ## Footnote Catecholamines increase heart rate, blood pressure, and glucose levels.
47
What is the **main glucocorticoid**?
Cortisol ## Footnote It is essential for life and stress response.
48
What are the **zones of the adrenal cortex**?
* Zona glomerulosa: makes aldosterone * Zona fasciculata: secretes cortisol * Zona reticularis: produces androgens and estrogens ## Footnote Each zone has distinct hormone production roles.
49
What is the effect of **glucocorticoids**?
* Increase blood glucose via liver gluconeogenesis * Reduce glucose uptake by muscle and fat * Promote protein breakdown and lipolysis ## Footnote Chronic stress can lead to muscle wasting and insulin resistance.
50
What are the **glands** throughout the body responsible for?
Making and releasing chemical messengers called hormones ## Footnote Hormones are crucial for various bodily functions and processes.
51
Hormones act only on **target cells** that have what?
Special receptors for them ## Footnote This specificity is essential for hormonal function.
52
What do hormones guide in the **fetus**?
* Development of brain * Development of reproductive organs ## Footnote Hormones play a critical role in fetal development.
53
During which life stages do hormones control **growth and development**?
* Childhood * Adolescence ## Footnote Hormonal regulation is vital during these formative years.
54
What systems do hormones coordinate in the body?
* Male reproductive system * Female reproductive system ## Footnote Hormones are essential for reproductive health and function.
55
What do hormones help the body adapt to?
Emergencies/stress ## Footnote Hormonal responses are crucial for survival in stressful situations.
56
Define **autocrine** communication in the endocrine system.
Releases a hormone that acts on itself ## Footnote This type of signaling is important for self-regulation.
57
Define **paracrine** communication in the endocrine system.
Hormones act on nearby cells ## Footnote This allows for localized hormonal effects.
58
Define **endocrine** communication in the endocrine system.
Hormones travel through the blood to distant target cells ## Footnote This is the classic mode of hormonal action.
59
What do the effects of hormones depend on?
How long they stay active in the bloodstream ## Footnote The duration of hormone activity influences physiological responses.
60
What is a **diurnal** pattern of secretion?
Follows a daily cycle, e.g., cortisol rises in the morning ## Footnote This pattern is important for maintaining circadian rhythms.
61
What is a **pulsatile/cyclic** pattern of secretion?
Released in bursts, e.g., reproductive hormones ## Footnote This pattern is crucial for reproductive function.
62
What is a **substrate-dependent** pattern of secretion?
Changes based on blood levels of substances, e.g., glucose, calcium ## Footnote This allows for precise hormonal regulation based on physiological needs.
63
What type of feedback loop is most common in hormonal regulation?
Negative feedback ## Footnote This mechanism helps maintain homeostasis.
64
What happens in a **positive feedback** loop?
Hormone release increases further secretion ## Footnote This is less common and often involved in processes like childbirth.
65
What is the role of **TSH** in thyroid feedback?
Stimulates thyroid to release T4 (thyroxine) and T3 (triiodothyronine) ## Footnote TSH is crucial for regulating metabolism.
66
What triggers hormone release in the body?
* Chemicals (e.g., blood glucose or calcium levels) * Endocrine signals (one hormone controlling another gland) * Neural control (nerve signals stimulating hormone secretion) ## Footnote These mechanisms ensure appropriate hormonal responses.
67
How do **water-soluble hormones** like insulin circulate?
Freely and act quickly ## Footnote They have short half-lives, typically seconds to minutes.
68
How do **lipid-soluble hormones** like cortisol circulate?
Bind to carrier proteins ## Footnote They have longer half-lives, hours to days, due to this binding.
69
What keeps lipid-soluble hormones stable in circulation?
Binding proteins ## Footnote Only free hormones can enter cells and trigger a response.
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