In knee jerk reflex, A functions as receptor organ while B functions as effector organ, Choose the option which gives the correct answer for the blanks in above statement.

Options

A. A-Patella bone B-Biceps muscles
B. A-Quadriceps femoris muscle B-Hamstring muscle
C. A-Hamstring muscle B-Quadricep femoris muscle
D. A-Patellar tendon B-Quadriceps femoris muscle

Answer

To solve the question regarding the knee-jerk reflex, we need to identify the receptor organ (A) and the effector organ (B) involved in this reflex action. Here’s a step-by-step solution:

### Step 1: Understand the Knee-Jerk Reflex
The knee-jerk reflex, also known as the patellar reflex, is an involuntary response that occurs when the patellar tendon (located just below the kneecap) is tapped. This action stretches the tendon and the quadriceps muscle, leading to a reflexive contraction.

**Hint:** Remember that reflexes involve a stimulus that triggers a response without conscious thought.

### Step 2: Identify the Receptor Organ (A)
In the knee-jerk reflex, the receptor organ is the part of the body that detects the stimulus. When the patellar tendon is tapped, the stretch receptors (muscle spindle fibers) in the quadriceps muscle sense this stretch. Therefore, the receptor organ (A) is the **patellar tendon**.

**Hint:** Think about what part of the body is responsible for sensing the stretch when the knee is tapped.

### Step 3: Identify the Effector Organ (B)
The effector organ is the part of the body that carries out the response to the stimulus. In the knee-jerk reflex, the contraction of the quadriceps muscle causes the leg to kick out. The muscle that is primarily responsible for this movement is the **quadriceps femoris** muscle, which acts as the effector organ (B).

**Hint:** Consider which muscle is responsible for the movement that occurs after the reflex is triggered.

### Step 4: Formulate the Answer
Based on the above analysis, we can fill in the blanks in the statement:
- A (receptor organ) = **Patellar tendon**
- B (effector organ) = **Quadriceps muscle**

### Final Answer
In knee jerk reflex, **patellar tendon** functions as receptor organ while **quadriceps muscle** functions as effector organ.

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