The reflex action - class-VI

Reflex actions are rapid, involuntary responses to stimuli that are primarily processed by the spinal cord, allowing for a faster reaction time than if the signal had to travel to the brain.

An automatic (involuntary) neuromuscular action excited by a defined stimulus is called reflex action. Sweating is not a reflex action. It is primarily a means of temperature regulation. But, Salivation and hand withdrawal because of the needle both are reflex actions.

Option 'D' is correct

Voluntary movements are movements that are in direct control of the will of a person. These are controlled by skeletal muscles. For example walking, talking, dancing, etc. Involuntary movements are movements that are not in control of a person. They are generated by smooth striated muscle. For example, heart pumping, digestion, etc. 

Medulla oblongata is the part of hindbrain. It is located in the brainstem, anterior to the cerebellum. It controls the involuntary functions . It is linked to the autonomic system and has cardiac, respiratory, vomiting and vasomotor centres. It also controls breathing heart rate and blood pressure.

Each kind of a change in the environment evokes an appropriate movement in
response. When we want to talk to our friends in class, we whisper, rather than shouting
loudly. So, the movement to be made depends on the event triggering it. Hence, such
controlled movement must be connected to the recognition of various events in the
environment, followed by only the correct movement in response. Therefore, the correct answer is option A.

Reflex action is an action which is given in response to something in the environment. It is an immediate action taken without much thinking and it does not have our control. The spinal cord is responsible for the response of the body because the impulse has not reached the brain till then. Therefore, the correct answer is option A.

• Voluntary actions are those which can be controlled by us like clapping, dancing, jumping, running, etc. 
• Whereas, involuntary actions are those which cannot be regulated or stopped by us like the circulation of blood, heartbeat, etc. Hence, reflex actions are involuntary actions that are done to save oneself from danger. 

• The best-known reflex is the pupillary light reflex. If a light is flashed near one eye, the pupils of both eyes contract.
•  Light is the stimulus, impulses reach the brain via the optic nerve, and the response is conveyed to the pupillary musculature by autonomic nerves. 

Swallowing food is a complex process involving both voluntary and involuntary muscle coordination, but it is not classified as a simple reflex action in the same way as blinking or shivering.

Ivan Pavlov is famous for his experiments on classical conditioning, which involves the formation of conditioned reflexes in dogs.

A reflex arc follows the pathway: Stimulus -> Receptor -> Sensory neuron -> Integration center (spinal cord) -> Motor neuron -> Effector -> Response.

Involuntary actions are the actions which are happening without the conscious choice of an organism. The examples for involuntary actions are: Vomiting, yawning, salivation, heart beats, coughing, sneezing, etc.  Whereas chewing is a voluntary action, which is controllable.

Reflex action is an involuntary action and it is a sudden reaction against the stimulus. e.g. removal of hand on being touched by hot or insertion of a pin in a skin, coughing, closing of the eyelid when any object enters in the eye

There are two types of reflex arcs namely, autonomic (visceral) reflex arc, affecting inner organs and somatic reflex arc, affecting muscles. 

• A simple reflex arc consists of only one sensory neuron and one motor neuron, hence the name is the monosynaptic reflex. A complex reflex arc or polysynaptic reflex is formed when the sensory neuron influences several motor neurons through intermediate (association) neurons of the spinal cord. Complex reflex arc consisting of two sensory neurons and one motor neuron.

A sleeping cat suddenly gets up and chases a rat. The movement involved is similar to the movement of train on green signal, because it is involuntary action.

So, the correct option is ‘the
movement of train on green signal’.

The somatic reflex arc affects the muscles and the receptor organ is skin whereas, the effector organ is skeletal muscles. The visceral reflex arc affects the internal organs and the receptor organ is epithelial lining of the gut whereas, the effector organ is smooth muscles.