Tag: coordination in human beings- chemical control

Luigi Galvani was an Italian physician who demonstrated what we now understand to be the electrical basis of nerve impulses when he made frog muscles twitch by jolting them with a spark from an electrostatic machine. So, the correct option is "D" (Luigi Galvani).

Reflex action is induced by the motor nerves. It is an involuntary and instant movement in response to a stimulus. A reflex action is done by neural pathway of reflex arc. In this, the action is done before the impulse reaches the brain. Out of the given options, sweating is not a reflex action. Salivation is a reflex action in which smell of food activate neural pathway and activates muscles and glands. This releases salivary juices. When someone is pinched by a needle, it activates neural pathway to evoke a response. The skin receptors quickly send nerve impulses to the spinal cord and response is relayed back. Apart from these, coughing, sneezing and blinking of eyes are also reflex actions.

Monosynaptic Reflex is a simple reflex that involves the transmission of an impulse from a sensory neuron to a motor neuron across a single synapse in the spinal cord. The knee-jerk reflex action is an example of such type of reflex.

• Involuntary actions in response to external or internal stimuli are termed as reflex actions. Peripheral nervous system and the spinal cord are involved in controlling the reflex actions. Here, the brain is not involved.
• The reflex action was discovered by Marshall. He proposed the theory explaining the body's reflex, or involuntary, actions.
  
• So, the correct answer is 'Marshall'.

• A stimulus is anything that can be perceived by a given organism including sight, sound, touch, smell, taste, etc.
•  A response is generally characterized as the behaviour proximal to the stimulus. So if a bell rings and a person jumps the stimulus is the bell and the response is the jump. 
• The ability of an organism or organ to respond to external stimuli is called sensitivity. When a stimulus is applied to a sensory receptor, it normally influences by a simple reflex. Hence, Simple reflex is best to characterize the simple response to simple stimuli. 

The reflex action is defined as the sudden and involuntary movements that are controlled directly by the spinal cord. These actions do not require memory generation most of the time, like blinking of the eyes when something comes close to them. These are called the unconditional reflexes. Some reflex actions may involve learning and these are call the conditional reflexes. For example release of saliva at the sight of the food. Obeying the orders is the voluntary set of actions performed under the command of the somatic nervous system. It involves memory generation so as to remember the tasks and voices.