Name: Control and Coordination
Uploaded: 2019-07-19
Duration: 38 min 51 s
Description: There are various systems in our body that help in running it. Let's learn about our body's chemical and electrical messengers, which govern the multiple sys...

Question

Describe all parts of the reflex arc with a suitable diagram.

Accepted Answer

A chain of neurons, which is present between the receptor and effector organ that forms an arc-like neural pathway through which reflex action occurs, is called the reflex arc. A reflex arc consists of five parts: receptor, afferent neuron, brain/spinal cord, efferent neuron, and effector organ.

Receptor: The receptor is the specialised structure of the sensory ending of the neuron. Receptors can be stimulated by environmental changes as well as by the changes within the body. Some examples of receptors are Pacinian corpuscle (found in the skin), Meissner's corpuscle (found in the upper dermis of the skin), end-organ of Ruffini (found in a deep layer of the skin), etc.

Sensory neuron/Afferent neuron: These neurons originate from the receptors and form the afferent limb of the reflex path. The afferent neuron consists of dendrites, cell body and axon. The dendrites originate from the receptors, the cell body lies in the dorsal root ganglion, and the short axon (afferent neuron) enters the spinal cord through the dorsal root of the spinal cord. Afferent neuron transmits the sensory impulse to the centre from the receptors.

Centre: Spinal cord or brainstem acts as the centre for reflex actions. In the centre, the afferent neuron makes synaptic connections (synapses) with the efferent neuron either directly or through internuncial neuron or connecting neurons. Sensory impulse is converted into a motor impulse in the centre.

Efferent neuron/Motor neuron: It originates either from the brain stem or from the anterior horn cell (grey matter) of the spinal cord. It forms an efferent limb of the reflex arc. The efferent neuron leaves the spinal cord through the ventral root. But the efferent neuron leaves the brain stem as cranial nerve as their cell bodies are located in the motor nuclei of the cranial nerves. Efferent neuron carries motor impulse from the centre to the effector organs.

Effector organ: It is the structure (organ) that executes the directives carried by the efferent (motor) neuron. Contraction of muscles or secretion of various types of glands occur. Examples of effector organs include skeletal muscle, smooth muscle, glands, etc.

Describe all parts of the reflex arc with a suitable diagram.

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