Parts of the brain that controls reflexes

Reflexes are the primitive action of the brain to warn us of danger in order not to harm us. 

In this article we will talk about the part of the brain that controls reflexes, we will explain what reflexes are, the reflex arc, the nervous system, and the brain itself. We will also talk about the kinds of reflexes and how this action is conducted.

Parts of the brain that controls reflexes

The part of the brain that controls reflexes is the cerebellum. The cerebellum regulates motor reflexes and is also involved in the synchronization of balance and muscles. The brainstem links and transmits messages to the spinal cord from the brain, regulating functions such as respiration, heart rate, and alertness.

The reflex arc is a neurophysiological mechanism of the nervous system that is activated in response to an external stimulus, such as when we give ourselves a strong blow or a source of heat is brought close to the body. 

Reflex movements are automatic and spontaneous, because, unlike other nerve pathways, sensory nerves transmit nerve impulses to the spinal cord without touching the brain, enabling a more rapid and efficient motor response.

What functions does the reflex bow have?

Most of the reflex arcs that exist in the human body aim to prevent us or respond quickly and effectively to potentially dangerous situations. For this reason they have been and are so necessary for our survival: they alert us when there is a risk of exposure to toxic elements, through smell receptors; or when we are about to burn, through the thermoreceptors.

However, some of the primary reflexes that we acquire at birth end up disappearing as we grow older. 

For example, the sucking reflex, which allows the child to feed and disappears at 4 months; or the Moorish reflex, which makes it easier for the baby to change position and protect itself against strident sounds, so necessary when we are newborns as it is dispensable after six months of life.

In short, there are different types of reflections with different functions; some are necessary from birth and become dispensable over time; and others remain for life because they fulfill an adaptive function essential for the survival and conservation of the human species itself.

 

How are reflexes classified?

In the human body there are various types of reflexes. Let’s review them:

1. Innate or congenital reflexes

They are common reflexes in all human beings. They are also called unconditioned or absolute, and their main characteristic is that no prior learning is necessary to acquire them, since they are an innate mechanism that protects us from potentially harmful external conditions (eg the withdrawal of the hand when feeling a source of heat).

2. Conditioned reflexes

Conditioned reflexes are the opposite of innate ones; that is, they are acquired as a result of learning and previous experiences in certain situations and external stimuli.

The best known is classical or Pavlovian conditioning, a type of learning according to which a stimulus with a neutral value, which initially does not elicit any response, ends up producing automatic responses by association with another stimulus that normally elicits them.

3. Myotatic reflex

The stretch reflex or stretch reflex occurs when we stretch a muscle and the muscle causes a contraction reaction opposite to stretching. The best known, perhaps, is the patellar reflex that is usually explored in the medical consultation and consists of percussing the patellar tendon with a reflex hammer, with the aim that the person responds with a sudden contraction of the quadriceps femoris muscle.

4. Reflex of spinal automatism

This type of reflex occurs when there is trauma and the spinal cord is injured. This is disconnected from the brain and the lower segment produces the reflex arc response. Some of these reflexes also intervene in the functioning of the bladder or rectum, in the reappearance of muscle tone or in the performance of certain involuntary movements

What does the brain do?.

Think of your brain as a large computer that controls all the functions of your body. The nervous system is a network that is responsible for sending messages to the brain and different parts of the brain. It is done through the spinal cord, which travels up the brain and down the back. It contains nerves inside, filaments that branch out to other parts of the body.

What pieces is the nervous system made up of?

The central nervous system and the peripheral nervous system make up the nervous system:

The central nervous system makes up the brain and spinal cord.

And the peripheral nervous system is made up of nerves that run across the body.

The human brain is remarkably lightweight and only weighs about three pounds (about 1,360 grams).

It has a lot of folds and grooves anyway. This gives you the additional surface you need for the body to store important data. 

A long mass of nerve tissue, about 18 inches (45 cm long) and 1/2 inch thick, is the spinal cord (just over 1 cm). It stretches to the end of the spine from the lower part of the brain. The nerves branch out to the remainder of the body during its entire journey.

Bones are covered by both the brain and the spinal cord: the brain, by the bones of the skull, and the spinal cord, by a collection of ring-shaped, interlocking bones called the vertebrae that make up the spinal column. By layers of membranes called meninges, as well as by a special fluid known as cerebrospinal fluid, all are covered and cushioned. This liquid helps to preserve nerve tissue, keep it safe, and extract waste products from it.

Types of reflex arcs

There can be two kinds of Reflex arcs: plain or compound. If the reflex arc mechanism includes only one sensory neuron and another motor neuron, we can talk of a basic reflex arc; if there are other types of neurons involved, on the other hand, we will be facing a compound reflex arc. 

Reflex arcs are usually compound or polysynaptic; that is, its circuit is made up of several synaptic connections.

On the other hand, there are reflex arcs in the autonomic nervous system, the part of the organism in charge of the control of the involuntary functions of the body and in the somatic nervous system, responsible for sending the information from sensory receptors to the central nervous system, as well as conducting nerve impulses to skeletal muscles to produce voluntary movements.

What is the difference between the neuronal circuits of the reflex arc of the somatic system and the autonomic system?

There are differences between the neuronal circuits of the reflex arc of the somatic system and of the autonomic system, mainly in the efferent part ; In the latter, the presence of a ganglion always mediates between the central nervous system and the effector organs, contrary to what occurs with the somatic efferent arc.

Through reflex arcs, our body sets in motion numerous nervous mechanisms and their existence seems to have been a determining factor at the evolutionary level, since it has been suggested that they are the original circuits from which the rest of the nervous structures of our body arose. 

Their value is undeniable, since without them we would not be able to face many dangerous everyday situations that we face in our daily lives.

What is the structure of the reflex arc? 

A reflex arc is made up of different parts that work in an integrated and coordinated way: receptors, sensory or afferent neurons, motor or efferent neurons, and effector organs. Let’s see what each one of them is made of.

1. The receptors

The sensory receptors located in the different nerve endings and distributed throughout the body are responsible for transmitting the information they receive from the outside in nerve impulses. 

These receptors are made up of specialized neurons that are responsible for transforming stimuli according to their modality, be it visual, olfactory, auditory, taste or touch (by grip, pain, temperature, etc.).

Among the most common receptors we can find photoreceptors, the cells in charge of detecting light intensity; thermoreceptors, responsible for detecting heat and temperature changes; or mechanoreceptors, neurons that react to mechanical pressure.

2. Sensory or afferent neurons

Once the receptors have captured the information from the outside, the sensory or afferent neurons are in charge of collecting it and transmitting it to the nerve centers (the gray matter) of the spinal cord, the place where the information will be processed in order to be able to elaborate the response that best adapts to environmental demands.

3. Motor or efferent neurons

The motor or efferent neurons conduct the nerve impulses of the orders that have been elaborated in the spinal cord and the integrating nerve centers to the effector organs that will produce the motor response.

The integrating nerve centers fulfill the function of connecting the sensory neurons with the motor neurons, thus allowing the transmission of information from one part to another and the consequent automatic response. The neurons that are responsible for this interconnection work are called interneurons.

4. Effector organs

The effector organs are the last component of the reflex arc. They are the structures in charge of executing the automatic and involuntary response that comes from the nerve centers of the spinal cord. There are different types: they can be exocrine glands (eg salivary glands or sweat glands) and muscles (eg skeletal muscles or heart muscle).

FAQS: Parts of the brain that controls reflexes

What part of the brain regulates reflexes and involuntary actions?

Brain stem

Consisting of the medulla (a swollen part of the upper spinal cord), pons and midbrain, the brain stem (lower animals have only a medulla). The reflexes and automatic functions (heart rate, blood pressure), limb movements and visceral functions are regulated by the brain stem (digestion, urination).

Are reflexes controlled by the brain?

A reflex arc is called the direction taken by the nerve impulses in a reflex. Most of the sensory neurons in higher animals do not move directly through the brain, but synapse through the spinal cord. … Reflexes do not require brain intervention, while reflex action can be stopped by the brain in some instances.

What is the part of the brain that controls behavior?

Frontal Lobe

Frontal Lobe: most anterior, right under the forehead; intellectual functions such as the ability to plan, as well as personality, conduct, and emotional control are regulated by the frontal lobe.

What are 3 reflexes in humans?

Kinds of human reflexes

Biceps reflex (C5, C6)

Brachioradialis reflex (C5, C6, C7)

Extensor digitorum reflex (C6, C7)

Triceps reflex (C6, C7, C8)

Patellar reflex or knee-jerk reflex (L2, L3, L4)

Ankle jerk reflex (Achilles reflex) (S1, S2)

Is it possible for humans to override reflex actions?

In order to protect the body, reflexes need to be swift. The reflex motion would make you drop it nearly instantly if you pick up a hot plate. We can actively override reflexes, though. You should try to fight the reflex to drop it so that you can comfortably put it down if the hot plate has your dinner on it.

In this article we talked about “Parts of the brain that control reflexes” and we discussed how reflexes work, the nervous system, the brain itself and the reflex arc. We also talked about the types of reflexes and how is the conduit between this action of the brain with the rest of the body.

If you have any questions or comments please let us know!

References

Castillo, G. D., & de Jorge, J. L. V. (2015). Anatomy and Physiology of the central nervous system. Univ. San Pablo Foundation.

Dewey, J. (1896). The reflex arc concept in psychology. Psychological review, 3 (4), 357.

Guyton, A. C., Hall, J. E., Zocchi, L., & Aicardi, G. (2006). Medical Physiology (Vol. 11). 

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