Lewis triple response
The Lewis triple response, also known as the "triple response of Lewis," is a physiological reaction that occurs when the skin is subjected to mechanical stimulation or irritation. It consists of three distinct components that appear sequentially when the skin is stroked or scratched. The Lewis triple response is often used as a diagnostic tool to assess the integrity of the nervous system, particularly nerve reflexes and blood vessel responses.
The three components of the Lewis triple response are:
1. **Red Line (Axon Reflex):** The first component involves the immediate appearance of a red line along the path of stimulation. This red line is caused by the axon reflex, which is a rapid dilation of the small blood vessels (capillaries) in response to the mechanical stimulation. This dilation is mediated by local nerve reflexes that trigger the release of vasodilatory substances like histamine.
2. **Flare (Axon Flare):** After a short delay, a reddish flare or spreading of redness occurs around the area of the initial stimulation. This flare is the result of the dilation of arterioles (small arteries) and capillaries beyond the immediate area of stimulation. The axon flare is also a part of the local nerve reflex response.
3. **Wheal (Mechanical Response):** Following the red line and flare, a raised area called a wheal appears at the site of stimulation. The wheal is caused by the release of histamine and other vasoactive substances from local mast cells in response to the mechanical irritation. Histamine causes the blood vessels to become leaky, allowing fluid to accumulate in the interstitial tissue, leading to the raised appearance of the wheal.
The Lewis triple response is often observed when the skin is gently stroked with a blunt instrument, such as the edge of a coin. It is commonly used in medical practice to assess the integrity of nerve reflexes and blood vessel responses in dermatological examinations. The reaction can vary based on individual differences and certain conditions, such as allergies or hypersensitivity.
Overall, the Lewis triple response provides insight into the complex interplay between neural and vascular responses in the skin when subjected to mechanical stimulation or irritation.
Sure, here are 10 multiple-choice questions (MCQs) along with their answers related to the Lewis triple response:
1. **Question:** The Lewis triple response consists of three components that appear sequentially when the skin is subjected to mechanical stimulation. What are these components?
- A) Red, Blue, Green
- B) Line, Flare, Spike
- C) Red Line, Flare, Wheal
- D) Itch, Rash, Swelling
- **Answer: C) Red Line, Flare, Wheal**
2. **Question:** The immediate appearance of a red line along the path of stimulation during the Lewis triple response is primarily caused by:
- A) Local mast cell degranulation
- B) Release of histamine
- C) Dilation of arterioles
- D) Axon reflex-mediated vasodilation
- **Answer: D) Axon reflex-mediated vasodilation**
3. **Question:** What is the underlying cause of the reddish flare that spreads around the initial area of stimulation in the Lewis triple response?
- A) Local histamine release
- B) Axon reflex-mediated vasoconstriction
- C) Mast cell activation
- D) Dilation of capillaries
- **Answer: A) Local histamine release**
4. **Question:** The raised area that appears at the site of stimulation during the Lewis triple response is known as:
- A) Flare
- B) Spike
- C) Rash
- D) Wheal
- **Answer: D) Wheal**
5. **Question:** Which of the following substances is responsible for making blood vessels become leaky during the formation of the wheal in the Lewis triple response?
- A) Serotonin
- B) Dopamine
- C) Histamine
- D) Epinephrine
- **Answer: C) Histamine**
6. **Question:** The Lewis triple response is often used to assess the integrity of which systems?
- A) Digestive system
- B) Cardiovascular system
- C) Nervous system
- D) Immune system
- **Answer: C) Nervous system**
7. **Question:** When is the wheal component of the Lewis triple response typically observed?
- A) Immediately after mechanical stimulation
- B) After the axon flare
- C) After the red line appears
- D) Before the axon reflex
- **Answer: B) After the axon flare**
8. **Question:** The Lewis triple response is primarily triggered by:
- A) Chemical irritants
- B) Temperature changes
- C) Mechanical stimulation
- D) Electrostatic charges
- **Answer: C) Mechanical stimulation**
9. **Question:** Which of the following best describes the axon reflex?
- A) Rapid dilation of blood vessels in response to histamine release
- B) Nerve reflex that triggers the release of vasoactive substances
- C) Immediate redness and swelling caused by mechanical irritation
- D) Delayed allergic response to skin stimulation
- **Answer: B) Nerve reflex that triggers the release of vasoactive substances**
10. **Question:** What role does histamine play in the Lewis triple response?
- A) It causes vasoconstriction of blood vessels.
- B) It leads to the formation of the red line.
- C) It causes fluid accumulation and the formation of the wheal.
- D) It triggers itchiness and rash.
- **Answer: C) It causes fluid accumulation and the formation of the wheal.**
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