**Question:** Korff's fibres are

A. sympathetic
B. parasympathetic
C. sensory
D. motor

**Core Concept:**
Korff's fibres refer to the sympathetic and parasympathetic nerves that play a crucial role in the autonomic nervous system (ANS). The ANS is responsible for the body's involuntary functions, such as digestion, heart rate, blood pressure, and sweating. These fibres are part of the peripheral nervous system (PNS) and originate from the spinal cord.

**Why the Correct Answer is Right:**
Korff's fibres are composed of two types of nerves: sympathetic and parasympathetic. The sympathetic fibres are responsible for the "fight or flight" response, increasing heart rate, blood pressure, and readying the body for action. The parasympathetic fibres, on the other hand, promote the "rest and digest" response, slowing down heart rate, lowering blood pressure, and facilitating digestion.

**Why Each Wrong Option is Incorrect:**

A. Sympathetic fibres: While sympathetic fibres are indeed part of Korff's fibres, they are not the entirety of them. Korff's fibres encompass both sympathetic and parasympathetic fibres.

B. Parasympathetic fibres: Similar to option A, parasympathetic fibres are part of Korff's fibres, but not the whole fibres.

C. Sensory fibres: Korff's fibres primarily involve the autonomic nervous system and its functions, not sensory nerves associated with pain or perception.

D. Motor fibres: Korff's fibres focus on the autonomic nervous system and its functions, not motor nerves responsible for muscle movement.

**Clinical Pearl:** Understanding Korff's fibres is essential for grasping the functioning of the autonomic nervous system and its roles in maintaining homeostasis and preparing the body for different physiological states.

**Correct Answer:** Korff's fibres consist of both sympathetic and parasympathetic fibres, contributing to the autonomic nervous system's functions in maintaining homeostasis and preparing the body for various physiological states.