Which of the following statement's are true ?
(a) Saltatory conduction is seen in nonmyelinated nerve fibres
(b) Nissl granules synthesize protein to repair damaged part of neuron
(c) Neurofibrils helps in internal conduction
(d) Trigger zone trigger nerve impulse at base of dendron

Options

A. (a), (b)
B. (a) (c)
C. (b), (c)
D. (c), (d)

Answer

To determine which statements are true, let's analyze each one step by step:

### Step 1: Analyze Statement (a)
**Statement:** Saltatory conduction is seen in nonmyelinated nerve fibers.
**Analysis:** Saltatory conduction occurs in myelinated nerve fibers, where the action potential jumps from one node of Ranvier to another. In nonmyelinated fibers, the conduction is continuous.
**Conclusion:** This statement is **false**.

### Step 2: Analyze Statement (b)
**Statement:** Nissl granules synthesize protein to repair damaged part of neuron.
**Analysis:** Nissl granules are composed of rough endoplasmic reticulum and ribosomes, and they are involved in protein synthesis, which is crucial for repairing damaged neurons.
**Conclusion:** This statement is **true**.

### Step 3: Analyze Statement (c)
**Statement:** Neurofibrils help in internal conduction.
**Analysis:** Neurofibrils are filamentous structures in the cytoplasm of neurons that play a role in maintaining the shape of the neuron and facilitating intracellular transport, which is essential for internal conduction.
**Conclusion:** This statement is **true**.

### Step 4: Analyze Statement (d)
**Statement:** Trigger zone triggers nerve impulse at the base of dendron.
**Analysis:** The trigger zone, also known as the axon hillock, is located at the junction of the axon and the cell body, not at the base of the dendron. It is responsible for initiating the action potential.
**Conclusion:** This statement is **false**.

### Final Conclusion:
The true statements are **(b) and (c)**.

### Summary of True Statements:
- (b) Nissl granules synthesize protein to repair damaged part of neuron. **(True)**
- (c) Neurofibrils help in internal conduction. **(True)**