REFLEX ACTION

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When you touch a hot object or when a pin pricks your finger, what is your immediate reaction? Of course, you remove your hand away from the source of pain, either the hot object or the pin. In situations like these, your reactions are always immediate, involuntary and sudden. They happen without much of a thinking process. In scientific terms, this action is called the reflex action.

DEFINITION 
A reflex is a rapid,  predictable response to a stimulus.

TYPES
 There are two types
➡️AUTONOMIC: Autonomic  reflexes  regulate the activity of smooth muscles,  the heart,  and glands.  Secretion of saliva (salivary reflex) and changes in the size of the eye pupils (pupillary reflex) etc.  Autonomic reflexes regulate such body functions as digestion,  elimination,  blood pressure,  and sweating.

➡️ SOMATIC :Somatic  reflexes  include all reflexes that stimulate the skeletal muscles.  When you quickly pull your hand away from a hot object, somatic reflex is working.  

COMPONENTS OF A REFLEX ARC
➡️Receptor
➡️sensory
➡️ Control center
➡️ Motor neuron
➡️ Effector Organ

EXAMPLES OF REFLEX ACTION
➡️ The sudden removal of the hand from a hot 🔥 object. 

➡️ When light acts as a stimulus, the pupil of the eye changes in size.

➡️ Sudden jerky withdrawal of hand or leg when pricked by a pin.

➡️ Coughing or sneezing, because of irritants in the nasal passages.

➡️ Knees jerk in response to a blow or someone stamping the leg.

➡️ The sudden removal of the hand from a sharp object.

➡️ Sudden blinking when an insect comes very near to the eyes.

PHYSIOLOGY OF REFLEX ACTION
The reflex action requires the 5 component of reflex arc to function.

➡️ A sensory receptor which is located at the peripheral of the skin. eg touching a hot object. Function : perceives sensory stimulus of pain.

➡️ Motor neuron receives this stimulus and convey it to the control center for necessary action. 

➡️ Control center which is usually the brain stem and the spinal cord receives this stimulus and sends motor stimulus to remove hand. 

➡️ Motor neuron conveys the motor stimulus to the effector organ. 

➡️ The effector organ is usually the muscles of the affected part. eg bicept muscles of the arm.

NOTE: Many spinal reflexes involve only spinal cord neurons and occur without brain involvement.  As long as the spinal cord is functional,  spinal reflexes,  such  as  the  flexor  reflex,  will  work.  By  contrast,  some  reflexes  require  that  the  brain  become involved because  many  different  types of  information have to be evaluated to arrive at the  “right” response.  The response of the pupils of the eyes to light is a reflex of this type.

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