[Biology Class Notes] on Types of Reflexes Pdf for Exam

The types of reflexes will be discussed after we make you familiar with a reflex or reflex action. Reflex is an involuntary or instantaneous action by our body parts in response to a stimulus. It is due to the numerous neural pathways known as reflex arcs that act on an impulse before it reaches the brain. For reflex to occur, there is no requirement of any conscious thought or awareness about the automatic response.

When you accidentally touch something hot, you quickly jerk your hand away to avoid being badly burned. Jerking our hands away is the cause of a complex framework of reflex arcs, which includes glandular processes like adrenalin release. You might be more badly injured if you had to think before acting. Reflexes protect us from danger and it works even if we are asleep. It safeguards our bodies against external and internal stimuli that can cause harm.

When a specialized tissue is receiving a stimulus, it may either directly or indirectly change the relation of other tissue or also the whole individual to the environment from where that stimulus arises. A few examples of the reflex action are the pupil of the eye changing its size where light acts as a stimulus; withdrawing our hands or legs suddenly when we touch something very hot and coughing or sneezing when dust or foreign particles enter our nasal passages. Our reactions are instantaneous, quick, and involuntary in these situations. It doesn’t require much of a thinking process and the action is called the reflex action. And here, the mechanism of reflex includes the roles of the spinal cord and the nerve pathway involved in this action including a sensory nerve, a synapse, and a motor nerve, which altogether is termed as a reflex arc. 

Classification of Reflexes

There are several ways to classify the reflexes of the body. Following is the classification of reflexes.

1. Based on the Type or Function

This is based on the movement of the organs or parts of the body that move due to the reflex. Some reflexes that move the skeletal muscles are extensor, flexor, locomotor, and statokinetic. Reflexes that involve the function of internal organs include cardiovascular, digestive, secretory, and excretory. 

2. Based on the Degree of Complexity

Reflexes can also be classified based on the degree of complexity of the neuron or nerve organization within the reflex arcs. Under this category, these can be monosynaptic or monosegmental reflexes that involve only one segment of the central nervous system and multisynaptic or intersegmental reflexes that involve more than one segment of the central nervous system.

3. Based on the Development

Reflexes can be innate reflexes and acquired reflexes where the former includes genetically determined and the latter type includes learned reflexes.

4. Based on the Response

Reflexes can be somatic reflexes that control skeletal muscle contractions and include superficial and stretch reflexes; the other one includes visceral or autonomic reflexes.

Importance of Reflexes

Reflexes are so important because it helps us to move our body and protect us from danger. There are two reflexes, good reflexes, and bad reflexes. Good reflexes help with exercise, sports, and everyday physical activities such as driving, crossing the road, and working, but bad reflexes can lead to injury and damage.

For example, when you fall, your reflexes tell your arms to reach out and break your fall, and your muscles throughout your body contract to minimize injuries. You may, however, increase your reflexes by undertaking workouts that target the specific reflex you want to strengthen.

Different types of reflex actions are known which are involuntary responses of effectors to the stimulus. It aids us in protection from any sudden stimulus that may harm us and therefore takes care of the survival of an organism. 

The significance of reflex action is due to the fact that reflex arcs are composed of major components creating a reflex. The function of each of these components is explained below:

1. Receptor- It receives the information and thus helps in generating impulses. 

2. Sensory Nerve- It transmits information from the receptor to the interneurons in the spinal cord. 

3. Interneuron- It generates effective responses by effectively processing the information.

4. Motor Nerve- It carries the respective information from the spinal cord to the effector organ. 

5. Effector Organ- It receives information from effector neurons and helps in generating the appropriate response (reflex). 

 

Some Common Types of Reflexes 

The types of reflexes include:

• Myotatic Reflexes: The myotatic reflex also called a muscle stretch reflex and also known as deep tendon reflexes, provides information on the central nervous system and peripheral nervous systems’ integrity. The contraction of a muscle in reaction to its lengthwise stretch is defined as stretch muscle.

• Tendon Reflexes: The contraction of a muscle in reaction to the striking of its tendon is known as a tendon reflex. The inverse of the stretch reflex is the Golgi tendon reflex.

• Reflexes that involve cranial nerves such as accommodation reflex, gag reflex, glabellar reflex, jaw jerk reflex, pupillary light reflex, blink reflex, and vestibulo-ocular reflex.

• The reflexes that are only observed in human infants and not in adults are known as primitive reflexes, which include rooting reflex, palmomental reflex, tonic labyrinthine reflex, moro reflex or startle reflex, asymmetrical tonic neck reflex, palmar grasp reflex, and sucking reflex.

• While various other kinds of reflexes are Muscular defense, Scratch reflex, Abdominal reflexes, Cough reflex, Sneeze, Gastrocolic reflex, Diving reflex, Withdrawal reflex, Baroreflex, Cremasteric reflex, Anocutaneous reflex, and Photic sneeze reflex.

We have briefly explained some reflex action examples in humans in the following points:

1. We close our eyes when a bright or shining light or torch hits our eyes.

2. We suddenly withdraw our hands or legs when they touch something sharp, hot, or pricking objects.

3. We cough or sneeze due to irritants, thread or foreign substances in the nasal passage.

4. We perform batting of eyelids frequently when something irritates our eyes.

5. We blink eyes when insects come in contact suddenly while driving.

6. There is a rooting reflex in infants where newborn babies automatically turn the face toward the stimulus to make sucking/rooting motions with the mouth whenever we touch the lip or cheek. The rooting reflex helps in ensuring successful breastfeeding.

7. Infants indulge in grasp reflex; it is such that when an object is kept in an infant’s hand and the child’s palm is stroked, the fingers will close reflexively and the object is grasped.

8. Muscular reflex can be seen in the abdominal region where abdominal muscles contract upon any force to the abdomen.

9. Also known as a patellar reflex, the Knee-jerk reflex makes the patellar tendon stretch, and this way the contraction of the quadriceps takes place.

Key Points Related to Reflexes:

• A reflex action is an automatic and a quick reaction to a sudden change in the environment known as stimuli.

• Reflex actions are an important aspect of our nervous system because they safeguard our bodies from injury caused by unexpected external and internal stimuli.

• The reflex arc is the path along which a reflex action travels. Autonomic and Somatic are two types of reflex arcs.

• The sensory neuron, motor neuron, receptor, interneuron, and effector organ are the components of the reflex arc.

• The function, types, degree of intricacy, and muscle effect are all used to classify reflexes.

• Accommodation reflex, corneal reflex, pupillary reflex, blushing, acoustic reflex, cough reflex, ankle jerk reflex, biceps reflex, cough reflex, and sneezing are all examples of reflex actions.