Adrenal Gland and Hormones Overview

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Questions and Answers

Which condition is characterized by an increase in aldosterone secretion?

Metabolic alkalosis (correct)

Metabolic acidosis

Hyperkalemia

Hypokalemia (correct)

What is the primary effect of aldosterone in the kidney?

Decrease Na+ absorption

Increase H+ excretion exclusively

Increase Na+ absorption in exchange for H+ or K+ (correct)

Increase K+ absorption

How does cortisol affect protein metabolism?

It enhances protein synthesis

It has no effect on protein metabolism

It decreases protein synthesis and increases protein catabolism (correct)

It decreases protein catabolism

What triggers the release of ACTH, which stimulates the adrenal glands?

Stress factors such as hypoglycemia Signup and view all the answers

Which glucocorticoid hormone is primarily produced by the zona fasciculata?

Cortisol Signup and view all the answers

What is the clinical picture of hypoaldosteronism?

Hyperkalemia and metabolic acidosis Signup and view all the answers

Which effect is associated with glucocorticoids on the blood cells?

Decrease in eosinophils and basophils Signup and view all the answers

What is one of the psychological effects of glucocorticoids?

Euphoria Signup and view all the answers

What is the primary effect of hypercortisolism on the body?

Cushing syndrome Signup and view all the answers

What is one of the main actions of catecholamine secreted by the adrenal medulla?

Bronchodilatation Signup and view all the answers

Which condition is associated with hypocortisolism?

Addison’s disease Signup and view all the answers

What effect does antidiuretic hormone (ADH) have during hypovolemic shock?

Vasopressor action Signup and view all the answers

What initiates the release of oxytocin during childbirth?

Stretching of cervix Signup and view all the answers

In the absence of antidiuretic hormone (ADH), what happens to urine output?

Larger volumes of diluted urine are excreted Signup and view all the answers

What enhances the contractile response of uterine muscles to oxytocin during labor?

Increased sensitivity to circulating oxytocin Signup and view all the answers

Which gland is referred to as the master gland of the endocrine system?

Pituitary gland Signup and view all the answers

Study Notes

Adrenal Gland

Located near the kidneys
Growth and hormone synthesis are stimulated by Pituitary ACTH
ACTH release is triggered by stress (e.g. hypoglycemia, low body temperature, shock)
Adrenal cortex is controlled by Pituitary gland ACTH
Adrenal medulla is part of the sympathetic nervous system

Adrenal Gland Hormones

Mineralocorticoid Hormones (zona glomerulosa):
- Aldosterone (95%) and Desoxycorticosteron (5%)
- Aldosterone is the primary mineralocorticoid secreted by the adrenal cortex
- Acts mainly in the kidneys (distal convoluted tubule) to increase sodium absorption in exchange for hydrogen or potassium
- Released in response to:
  - Low sodium levels (Hyponatremia)
  - High potassium levels (Hyperkalemia)
  - Angiotensin II
Hyperaldosteronism: Increased aldosterone secretion
- Clinical picture:
  - Low potassium levels (Hypokalemia)
  - Metabolic alkalosis
Hypoaldosteronism: Decreased aldosterone secretion
- Clinical picture:
  - High potassium levels (Hyperkalemia)
  - Metabolic acidosis
Glucocorticoid Hormones (zona faciculata):
- Cortisol (95%) and corticosterone (5%)
- Essential for life
- Influences various organs:
  - Metabolic Effects:
    - Carbohydrate Metabolism:
      - Anti-insulin effect
      - Increases blood sugar levels by:
        
        Increasing gluconeogenesis from amino acids
        
        Decreasing glucose utilization by peripheral tissues
    - Decreases protein synthesis and increases protein catabolism
    - Enhances lipolysis and causes fat redistribution
  - Circulatory Functions: Maintains normal circulatory functions and cardiovascular responsiveness to catecholamines
  - Hematological Effects:
    - Decreases all blood cells except red blood cells and platelets
    - Anti-inflammatory effect by decreasing eosinophils, basophils, and stabilizing their lysosomal membranes
  - Gastric Effects: Increases gastric hydrochloric acid (HCl) and decreases mucosal cell proliferation, leading to gastritis and peptic ulceration
  - Psychological Effects: Euphoria, psychosis, depression, paranoia
  - Lung Function: Increases lung surfactant in late pregnancy
  - Aldosterone-like Effect: Exerts aldosterone-like effects
  - Plasma Cortisol Levels: Follow a diurnal pattern or circadian rhythm (highest just before waking, lowest at midnight)
Hypercortisolism: Causes Cushing syndrome
- Clinical picture:
  - Moon face
  - Buffalo hump
  - Pendulous abdomen
  - Muscle wasting
  - Osteoporosis
  - Poor wound healing
Hypocortisolism: Causes Addison's disease

Adrenal Medulla

Secretes catecholamines (e.g. epinephrine, norepinephrine) in response to sympathetic nervous system stimulation during stress
Actions of catecholamines:
- Vasoconstriction and increased blood pressure
- Increased heart rate and cardiac output
- Bronchodilation
- Glycogenolysis
- Increased basal metabolic rate (calorigenic effect)
Tumors of the adrenal medulla lead to over-secretion of catecholamines, causing episodes of hypertension

Antidiuretic Hormone (ADH)

Functions:
- Regulation of Body Water Balance: In the absence of ADH, the distal nephron becomes impermeable to water, resulting in the excretion of large volumes of diluted urine (20 ml/minute).
- Vascular Smooth Muscle Contraction: High concentrations of ADH stimulate vascular smooth muscle contraction (pressor effect), which is a crucial compensatory reaction in hypovolemic shock.

Oxytocin

Synthesized by the hypothalamus as part of a prohormone
Transported to the posterior pituitary for storage
Release Triggered By:
- Stretch receptors in the cervix during labor
- Touch receptors in the nipple during suckling (milk let down reflex)
Functions:
- Initiation of Labor: Contractile response of uterine muscles to oxytocin is enhanced by estrogen and antagonized by progesterone levels. In late pregnancy, uterine smooth muscles become more sensitive to circulating oxytocin.
- Milk Ejection: Suckling stimulates touch receptors on the nipple, sending nerve signals to the hypothalamus, leading to oxytocin secretion and contraction of myoepithelial cells around the alveoli of the mammary gland.

Reminder

Endocrine glands are ductless glands that secrete regulatory molecules called hormones.
The pituitary gland is the master gland of the endocrine system.

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Description

Explore the structure and function of the adrenal gland, including the role of hormones produced by its cortex and medulla. Understand how ACTH influences hormone synthesis and the clinical implications of conditions like hyperaldosteronism and hypoaldosteronism. This quiz will test your knowledge of adrenal gland physiology and hormone regulation.