Question

1. Describe the basic arrangement of a reflex. How does it differ depending on whether it is from the ANS or somatic NS?

Answer 1

Reflex is a protective mechanism of the body, exhibited in the form of a rapid involuntary motor response towards both the external and internal stimuli. There are two types of reflexes namely, autonomic and somatic reflexes. A reflex arc consists of the following parts.

• A sensory (receptor) organ (Eg: skin that contains thermoreceptors, nociceptors, pressure receptors etc.)
• A sensory nerve: (Afferent neuron) which terminates at the posterior nerve root of spinal cord. This neuron carries impulses from the effector organ towards the CNS.
• Spinal cord: In the gray matter, the sensory stimulus is converted into a motor impulse.
• Interneuron: Neurons present in the spinal cord, which connect the afferent and efferent neurons.
• A motor nerve: (Efferent nerve) it arises from the anterior horn cells of spinal cord, which transmits the impulses to the effector organ, in this case, the finger.

Autonomic reflexes are completely uncontrolled by the will. The components of an autonomic reflex arc include,

1. Receptor – The distal end of the sensory neuron
2. Sensory neuron – somatic or visceral sensory neuron that carry impulses towards the central nervous system (CNS)
3. Association neurons – Integrate and interpret the signals in the CNS
4. Autonomic motor neurons

• Preganglionic neuron – convey impulses from the CNS to the autonomic ganglion
• Postganglionic neuron – convey impulses from the autonomic ganglion to the effector organ

5. Visceral effector – Can be a smooth muscle, cardiac muscle, or gland, which produces response

The somatic reflexes can be controlled by will (for example, we can tolerate some heat to some extent if we are holding some precious material in our hands, though it is painful). Skeletal muscle reflex is a somatic reflex.