**Question:** Parasympathetic ganglion in head are:

A. Spinal Ganglia
B. Preganglionic neurons
C. Autonomic Ganglia
D. Postganglionic neurons

**Core Concept:**

The parasympathetic nervous system is part of the autonomic nervous system, which is responsible for maintaining homeostasis and regulating involuntary functions in the body. In the head, parasympathetic ganglia are located primarily within the cranial nerves. These ganglia are involved in the transmission of impulses in the parasympathetic pathway.

**Why the Correct Answer is Right:**

The correct answer is **D. Postganglionic neurons**. Postganglionic neurons are the final component of the parasympathetic pathway, carrying the information from the ganglia to the target organs. In the head, these neurons are responsible for the parasympathetic control of various functions like salivation, lacrimation, pupillary dilation, and smooth muscle relaxation.

**Why Each Wrong Option is Incorrect:**

A. **Spinal Ganglia** are part of the sympathetic nervous system, which is different from the parasympathetic system. They are located in the spinal cord and are involved in various cardiovascular, respiratory, and gastrointestinal functions.

B. **Preganglionic neurons** are the first component of the parasympathetic pathway, originating from the brainstem and transmitting the impulses to the ganglia. They are not considered as a part of the parasympathetic ganglia.

C. **Autonomic Ganglia** is a broader term referring to both sympathetic and parasympathetic ganglia. While this is true, the question specifically asks for the parasympathetic ganglia in the head, making option D the correct answer.

**Clinical Pearl:**

Understanding the difference between sympathetic and parasympathetic ganglia is crucial for understanding the functioning of the autonomic nervous system. The parasympathetic ganglia play a vital role in maintaining homeostasis and regulating involuntary functions in the head and neck region. Understanding this relationship will help students in interpreting clinical scenarios related to autonomic dysfunction and in formulating appropriate treatment strategies.