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Types of Reflexes

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What is a Reflex?

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. 

  1. 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.

  1. 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.

  1. 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.

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FAQs on Types of Reflexes

1. What is a reflex action and what are the main components of a reflex arc?

A reflex action is an involuntary, rapid, and automatic response to a stimulus that occurs without conscious thought. It is mediated by a neural pathway called the reflex arc. The five essential components of a typical reflex arc are:

  • Receptor: Senses the stimulus (e.g., heat or pain receptors in the skin).
  • Sensory Neuron (Afferent Pathway): Transmits the nerve impulse from the receptor to the central nervous system.
  • Integration Centre: Located in the spinal cord or brainstem, it consists of one or more synapses where the sensory neuron communicates with a motor neuron, often via an interneuron.
  • Motor Neuron (Efferent Pathway): Carries the nerve impulse from the integration centre to the effector.
  • Effector: The muscle or gland that responds to the motor command (e.g., a muscle contracting to pull the hand away).

2. What are the two primary types of reflexes found in the human body?

The two primary types of reflexes are classified based on the part of the nervous system that controls them:

  • Somatic Reflexes: These reflexes involve the stimulation of skeletal muscles. They are typically responses to external stimuli and are responsible for voluntary muscle movements, although the reflex itself is involuntary. A classic example is the knee-jerk (patellar) reflex.
  • Autonomic (Visceral) Reflexes: These reflexes regulate the activity of smooth muscles, cardiac muscle, and glands. They control involuntary bodily functions such as heart rate, digestion, and blood pressure. An example is the pupillary light reflex, where the pupil constricts in response to bright light.

3. How are reflexes classified based on the number of synapses involved?

Reflexes can be classified based on the complexity of the neural circuit in the central nervous system:

  • Monosynaptic Reflexes: These are the simplest reflexes, involving only one synapse in the CNS. The sensory neuron synapses directly with the motor neuron. This results in a very fast response. The stretch reflex, such as the knee-jerk reflex, is a prime example.
  • Polysynaptic Reflexes: These are more complex and involve one or more interneurons that connect the sensory and motor neurons. This allows for more complex processing and responses. The withdrawal reflex (pulling your hand away from a hot object) is a polysynaptic reflex.

4. What is the difference between a conditioned and an unconditioned reflex?

The key difference lies in whether the reflex is innate or learned:

  • Unconditioned (Innate) Reflexes: These are genetically determined, inborn reflexes that do not require any prior experience or learning. They are present from birth and serve basic survival functions. Examples include sneezing, coughing, and the sucking reflex in infants.
  • Conditioned (Acquired) Reflexes: These reflexes are acquired through experience and learning. They develop when a neutral stimulus becomes associated with an unconditioned stimulus. The most famous example is Pavlov's experiment, where dogs learned to salivate (a conditioned reflex) at the sound of a bell that was repeatedly associated with food.

5. What are some key examples of somatic reflexes and their functions?

Somatic reflexes are crucial for protection, posture, and coordination. Key examples include:

  • Stretch Reflex (e.g., Knee-jerk): A monosynaptic reflex that causes a muscle to contract in response to being stretched. It is important for maintaining muscle tone and posture.
  • Flexor (Withdrawal) Reflex: A protective polysynaptic reflex that causes you to withdraw a limb from a painful or threatening stimulus, such as touching a hot surface.
  • Crossed Extensor Reflex: Often accompanies the flexor reflex. While one limb is withdrawn (flexed), the muscles in the opposite limb are stimulated to extend. This is vital for maintaining balance, for instance, when you step on a sharp object and need to shift your weight to the other leg.

6. Why is a reflex action significantly faster than a normal conscious action?

A reflex action is faster because its neural pathway, the reflex arc, is a direct and short route. The nerve impulse travels from the receptor to the spinal cord and then directly to the effector muscle. It bypasses the higher processing centres of the brain responsible for conscious thought and decision-making. This shortcut eliminates the time needed for deliberation, allowing for an immediate, protective response that is crucial for survival.

7. Can a reflex action be consciously controlled or stopped? Explain why or why not.

Yes, to a certain extent. While reflexes are fundamentally involuntary, they can be influenced or suppressed by the brain. Descending nerve pathways from the cerebral cortex can send inhibitory signals to the motor neurons in the spinal cord. This can override or dampen a reflex. For example, you can consciously prevent yourself from dropping a very hot plate if you know it's valuable. This demonstrates the brain's ability to modulate a basic reflex, although the initial impulse to react will still be felt.

8. How does the brain, specifically the cerebellum, influence reflex actions?

While many simple reflexes are managed by the spinal cord, the brain, particularly the cerebellum, plays a crucial role in modulating and coordinating them. The cerebellum is responsible for fine-tuning motor activity. It receives sensory information about the body's position and the status of reflex actions, and it adjusts motor output to ensure that movements are smooth, coordinated, and balanced. It does not initiate the reflex but acts as a control centre to perfect the resulting movement.

9. What is the clinical importance of testing a patient's reflexes?

Testing reflexes is a fundamental and powerful diagnostic tool in neurology. By observing a patient's reflex responses (like the knee-jerk or pupillary reflexes), doctors can assess the health of the nervous system. Abnormal reflex responses—such as being exaggerated (hyperreflexia), diminished (hyporeflexia), or absent—can pinpoint the location of neurological damage. For example, an absent reflex may indicate a problem with a specific spinal nerve, while exaggerated reflexes might suggest an injury to the brain or upper spinal cord.

10. Do all reflexes involve the spinal cord? Provide an example.

No, not all reflexes involve the spinal cord. Reflexes whose integration centre is in the brainstem are known as cranial reflexes. These involve the cranial nerves. A common example is the blinking reflex, which is triggered when an object rapidly approaches the eye or the cornea is touched. The sensory information is carried by a cranial nerve to the brainstem, which then sends a motor command via another cranial nerve to the eyelid muscles, causing them to contract and close the eye for protection.