What Are the Different Types of Natural Stimulants?

Reflection is a natural phenomenon that manifests as the inverse response of a stimulus to a stimulus. . The extension of reflection is broad. The field of physics refers to the phenomenon in which sound waves, light waves or other electromagnetic waves encounter other media interfaces and are still propagating in the original material. In the field of biology, reflection is the rule of the body's internal and external environmental stimulation with the participation of the central nervous system. Sexual response. In the computer world, reflection is an object that provides encapsulated assemblies, modules, and types; in the electronic field, it is an echo on a transmission line. Studying the mechanism of reflection and grasping the law of reflection will help humans make better use of reflection for various related tasks. Its application fields are quite extensive.

Chinese name: reflection
Explain: A natural phenomenon

which performed: Adverse response to stimulus
Presenter: R. Descartes

Basic reflection concepts

First proposed by the French philosopher R. Descartes. He noticed that the body responded regularly to some environmental stimuli. For example, a foreign object touching the cornea causes a blink. He borrowed the concept of reflection in physics, thinking that the movement of animals is reflected as light is projected on a mirror, that is, the stimulus and the reaction of the body have a necessary causal relationship. Experimental analysis of the brain and spinal cord and clarification of the reflex patterns are CS Sherington in the United Kingdom and in Russia. M. Shechenov, . . Pavlov. Sherington made a detailed study of the reflexes in the lower parts of the central nervous system (including the brainstem and spinal cord), and clarified the basic laws of reflexes. However, he only called the body's involuntary actions caused by external stimuli as reflexes, and believed that the neural nucleus below the cortex was the center of reflexes at all levels. The concept of reflexes is generally not applied to the activities of the higher parts of the nervous system (the brain). Sechenov applied the concept of reflection to the activity of the human brain. Later, under the influence of Shechenov's thought, Pavlov further studied the function of the cerebral cortex. He understood the so-called psychological secretion of salivary glands as a special kind of reflex, the conditioned reflex, by using a famous experiment made by dogs, and objectively studied the law of the occurrence and regression of this activity, and put forward the theory of conditioned reflex, that is, Advanced Neural Activity Doctrine. This study tends to analyze more deeply the neural circuits of reflection and the production of transmitters. In general, the body's regular response to various external or internal stimuli through the nervous system is called reflection.

Reflection germline

The unicellular animal's nervous system responds to stimuli by protoplasts. Coelenterate animals begin to have nerve cells and form a network, but there is no central or peripheral distinction. When stimulated, they cause a systemic response. Link animals and arthropods have a chain-like nervous system. The pair of ganglia on the dorsal side of the pharynx are particularly large. Some people also call it the brain. These animals have complete reflex arcs, and the internal and external stimuli begin to have simple reflections. activity.

The front end of the central nervous system of vertebrates is the real brain, and the back end is the spinal cord; the peripheral nerves are composed of brain and spinal nerves, and mammals have a highly developed cerebral cortex. In higher animals and humans, the cerebral cortex has become an advanced part that controls the whole body's activities. The structures of the central nervous system are divided into high-level and low-level functions. The low-level central center can complete some basic and simple reflections, and the reflection under the high-level central adjustment is more complicated and perfect.

reflection

The human embryo begins to form a neural plate at the third week, and then develops into a neural tube. Then the head of the neural tube expands and develops into different parts of the brain, and the tail of the neural tube develops into the spinal cord. Because the basic structure of the fetal nervous system has been formed, newborns can complete some of the simplest unconditioned reflexes, such as sucking reflexes, swallowing reflexes, urination reflexes, defecation reflexes, and flexor reflexes. In the future, as the body continuously contacts the external environment, more and more conditioned reflections can gradually be formed after training. In the process of individual growth, various conditioned reflections are constantly established, so that the number of reflections is increasing, and the forms of reflections are becoming more and more complex.

The reflection arc is the structural basis for reflection activity. It is the whole path that the excitement follows in the nervous system from receiving the stimulus to reacting. Reflection generally requires a complete reflection arc. A complete reflex arc consists of five basic parts: the receptor, the afferent nerve, the nerve center, the efferent nerve, and the effector.

Receptors can transform internal and external stimuli into special structures for neural impulses; they are the beginning of reflex activity.

A process of afferent neurosensory neurons. The nerve impulses of the receptors are transmitted to the nerve center.

The neuron group involved in a certain reflex activity in the nerve center is the central integrated part of the reflex arc. For example, the central structure that participates in the pupil's reflection of light is called the light reflection center. The central range of simple reflexes is relatively limited, and afferent neurons in the nerve center can directly communicate with efferent nerves.

Animal reflection Form a single synaptic connection; most reflexes pass between more than one intermediate neuron between afferent and efferent neurons to form a multisynaptic reflex.

Axons of efferent neuromotor neurons. The nerve impulses that occur in the reflex center are passed to the effector.

In reflex activity, motor neurons receive the influence of afferent or intermediate neuron afferent impulses, as well as the control of descending fibers in the central nervous system at all levels. As a result, it became the last common, outgoing path to the effector on the reflected outgoing path, which Sherington called the final road.

Effector The organ or tissue that responds, including skeletal muscle, cardiac muscle and smooth muscle, various exocrine glands and some endocrine glands.

The interruption of any of the five components of the reflection arc will make the reflection disappear. In some reflex activities, the efferent nerve first acts on certain endocrine glands, causing the glands to release hormones for transport through the blood, and finally to effectors. The effect of this reflex activity involving the endocrine glands is often slower, but the effect is more extensive and lasting.

Basic classification of reflection

Classification by formation

According to the characteristics formed by reflection, it can be divided into two categories: non-conditional reflection and conditioned reflection: the former is born by animals and does not require subsequent training. It is established and consolidated by animals during germline evolution and can be inherited again. To future generations. Non-conditioned reflection arcs are fixed and their number is limited, such as stretch reflection, pupil reflection on light, etc. The latter is obtained by animals after learning and training in their individual lives, and is an advanced form of reflection. If the animal's living conditions change, the conditioned reflexes that have formed will fade away and new conditioned reflexes can be formed. Therefore, the reflection arc of conditional reflection is not fixed, its form is various and its number is infinite. It makes animals more adaptable to the ever-changing external environment.

Classification by sensor

According to the location of the receptor, it can be divided into external sensory reflection caused by external sensory receptors and internal sensory reflection caused by internal organs or proprioceptors.

Classification by effector properties

According to the nature of the effector, it can be divided into body reflection and visceral reflection. The former effects are skeletal muscle activities, such as postural reflexes; the latter effects include changes in cardiovascular, gastrointestinal, bronchial smooth muscle, bladder and ureter movements, and glandular secretion.

Classified by biological significance

According to the biological significance of reflection, it can be divided into defensive reflection or protective reflection, food reflection ingesting and digesting food, and sexual reflection related to extended race.

Classified by the number of synapses

According to the number of synapses in the reflection arc, it can be divided into single synaptic reflection and multi-synaptic reflection. The former is the reflection through a single synaptic reflection arc. Such as the knee jump reflex, that is, after the tendon below the knee joint is slammed, the sensory (muscle spindle) in the muscle is stimulated by the nerve impulse, which enters the spinal cord along the afferent nerve and directly causes the latter through synapses formed with motor neurons. Excitement, a process of muscle contraction. The latter is a reflection that occurs through the reflection arcs of two or more synapses. Most reflexes in the body are polysynaptic reflexes. For example, flexor reflex, which refers to pain or nociceptive stimulus that acts on the skin or subcutaneous tissue, can cause the flexion of the irritated limb to contract, and the extensor to relax, so that the retraction of the limb is the reflection of multiple synapses.

Classified by clinical perspective

From a clinical perspective, reflection can be divided into physiological reflection and pathological reflection. The former are various reflexes that occur during normal life, while the latter are abnormal reflexes that occur after lesions occur in certain parts of the nervous system. The pupil's reflection of light is a physiological reflex, while ankle clonus and Babinski sign appearing after the cone system is destroyed are pathological reflexes. Certain reflexes are often indicators that doctors use to determine whether the nervous system is functioning properly at a certain location.

Other taxonomy

There are also some special types of "reflection", such as "local reflection" and "axon reflection". Strictly speaking, they are not true reflections, that is, reflections that can be done without the involvement of the central nervous system. Such as the formation of lower animals through the neural network and ganglion some reactions are "local reflection." The ganglia and plexus in the intestinal wall of higher animals can also perform a certain "local reflex" (see enteric nervous system). "Axon reflex" is a phenomenon that can cause redness in the skin around the irritated area when the skin receptors are stimulated. When the skin receptor is excited, the nerve impulses pass along the other branches of the afferent neuron to the peripheral subcutaneous blood vessels in the reverse direction, which directly causes the skin vasodilation reaction without passing through the center (Figure 3).

Basic characteristics of reflection

During reflex activity, nerve impulses must pass through the central part of the reflex arc. There is no protoplasmic connection between central neurons, and the transmission of information between them is mainly accomplished by synapses or gap connections where the neurons are in contact. Therefore, the transmission of information through the center is already different from the peripheral conduction. In addition, the connection between neurons is complex and diverse. Therefore, the reflex activity has many characteristics that are different from the peripheral conduction:

Unidirectional transmission When the phrenic nerve impulse is transmitted in the central part, it can only be carried from the afferent neuron to the efferent neuron, and cannot be reversed. The characteristics of this one-way transmission are determined by the characteristics of synaptic transmission in the center. Therefore, excitement in the reflex arc can only be transmitted from the dorsal root of the spinal cord and from the ventral root, but not the other way round. That is, the dorsal root is sensory and the ventral root is mobile. .

Central excitation process and inhibition process is the two basic processes of central nervous activity. Both occur at the synapse. When a neuron is excited, transmission through synapses may have two effects on subsequent neurons: excitation or suppression (see Synapses). In addition to the simplest reflex arc consisting of two neurons, the complex reflex arc consists of many neurons, and each neuron can simultaneously accept many excitatory and inhibitory synapses. In addition, the intensity of these two types of post-synaptic potentials is constantly changed by the influence of various afferent impulses. Therefore, reflex activity is the result of the interaction between central excitation and inhibition processes. If the excitement of the center is dominant, a specific reflection occurs; if the inhibition of the center is dominant, then this reflection is weakened or absent, which is called the suppression of reflection.

Limitation and Diffusion: In the reflection activity, if the intensity of the stimulus given to the susceptor is appropriate, it generally causes more limited reflection instead of extensive activity, which is called the limitation of reflection. If the stimulus is too strong, it will cause a wide range of activities, called diffusion of reflection. The diffuse connection between neurons is the structural basis of reflection diffusion. The extent of the diffusion depends on the intensity of the stimulus and the different functional states of the center. For example, stimulating the skin of the toes of the lower limbs of one side of the animal only causes ankle flexion: if the intensity of the stimulus is increased, the excitement will spread in the center and the knee and even hip joints will also flex. Further strengthen the stimulation, the excitement can also spread to the contralateral center, causing the contralateral lower limbs to straighten. Therefore, when one side of the lower limb is damaged by stimulation, the excitatory process of the ipsilateral flexor center occurs, causing the limb to flex and retract to avoid the stimulus source; at the same time, the excitement spreads to the contralateral extensor center, causing contralateral extension. Muscle reflexes to support the body and maintain a certain posture. In this way, the lower limb flexed on the stimulated side and the contralateral lower limb straightened to complete a coordinated posture reflex.

Facilitation and obstruction In reflex activity, an impulse introduced by a single fiber can not cause post-synaptic neurons to generate neural impulses, that is, it cannot cause reflex effects. This is because the excitatory post-synaptic potential caused by an impulse introduced by a single fiber is small, which can only increase the excitability of neurons. However, if there are many afferent fibers transmitting impulses to the same neuron at the same time, the post-synaptic potential generated on each post-synaptic membrane can be superimposed, a phenomenon called spatial sum. It facilitates reflection. On the other hand, impulse can also cause blockage when it spreads in the central part of the reflection arc. For example, fiber A alone can cause 9 post-synaptic neurons to excite, and fiber B alone can cause other 9 postsynaptic neurons to excite. Because fiber A and fiber B dominate 6 neurons together, when fiber A and fiber B are excited, only 12 neurons will activate instead of 18 neurons. This phenomenon is called blocking. It can be seen that in the reflection activity, the reflection activity can be strengthened due to the facilitation of the center, or the reflection activity can be weakened due to the blockage of the center.

Central delay (central delay) In the reflex activity, the time between the start of the stimulus and the response of the effector is called the reflex time. It includes the time consumed by stimulation to induce sensory excitement and the production of nerve impulses; the conduction of nerve impulses on afferent and efferent nerves and the response of effectors caused by nerve impulses; and the consumption of impulses transmitted at the synapses in the central time. The latter takes much longer than the impulses to conduct on the corresponding length of nerve fibers. Therefore, it is called central delay or synaptic delay. It is determined that the time required for excitement to pass through a synapse is 0.3 to 0.5 milliseconds. It can be seen that the more synapses that pass through the reflex center, the longer the central delay time.

After-effect reflex activities are caused by stimulation, but when the stimulation is stopped, central excitement does not disappear immediately, efferent nerves still intermittently emit nerve impulses, allowing the reflex activity to continue for a period of time. This phenomenon is called post-reflex or central excitement. After discharge. Within a certain range, the stronger the stimulus, or the longer the duration of the stimulus, the longer the duration of the subsequent effect. The excitatory synaptic connection between the central neurons is the morphological basis of the post-acting effect. Nerve impulses pass through many side branches with different numbers of synapses in the reticular connection and reach the same efferent neuron one after another. The efferent neuron is continuously stimulated and discharged continuously, which is the main mechanism of post-effect.

Fatigue When the afferent nerve is repeatedly and rapidly stimulated, the initial firing frequency of the efferent neuron is very high, but after a few milliseconds or seconds, the firing frequency gradually decreases. This is called reflex fatigue. Reflex fatigue occurs at synaptic sites in the center. Therefore, reflex fatigue is essentially the fatigue of synaptic transmission. The mechanism of synaptic fatigue is related to the depletion of presynaptic peripheral transmitters. It is estimated that if the sources of neurotransmitters are not replenished in time, the neurotransmitters stored in the presynaptic terminals are only enough to carry out 10,000 synaptic transmissions, and the total amount can be depleted in seconds.

Reflection part reflection type

Reflex physiological reflex

Reflex:

With the participation of the central nervous system, the body responds regularly to internal and external environmental stimuli. The structural basis of reflective activity is the reflective arc. There are two kinds of reflections in higher animals and humans: one is formed and inherited during the phylogenetic process, so the innate reflection that is born is called unconditioned reflection. It is caused by direct stimulation of the receptors and is performed through the central subcortical reflexes. For example, a newborn baby will suckle when it touches the nipple. When a person eats, the mucous membranes of the tongue and mouth will cause food to cause saliva secretion. The other is conditioned reflection, which is an acquired reflection that is gradually formed on the basis of non-conditioned reflection when the individual animal adapts to environmental changes during the life process. It is caused by signal stimulation and is formed with the involvement of the cerebral cortex. Conditional reflex is an advanced regulatory function of the brain that improves the ability of animals and humans to adapt to the environment. According to different structural foundations, reflection can be divided into simple and complex. The simplest reflection is a single synaptic reflection. Complex reflections are widely distributed in nerve centers, and complex chains are formed by connecting neurons. Reflection is the basic way to achieve functional adjustment. If any part of the reflection arc is destroyed, reflection cannot be achieved. Due to the structural and functional characteristics of synapses, it is determined that the transmission of impulse on the reflex arc can only pass from the susceptor to the effector.

Reflection is the basic way of neural activity. The structural basis of reflection is the reflection arc. Reflection includes unconditional reflection and conditional reflection. The most prominent feature of human reflexes is the ability to establish conditioned reflexes on language stimuli.

Bioreflection

Whether it is simple or complex activities, they are mainly regulated by the nervous system. The basic way of neuromodulation is reflex.

What is reflection?

Knee jump reflex: Quickly tap the ligament below the knee, and some of the thigh muscles will quickly contract, causing the lower leg to suddenly lift. There are many similar examples. For example, when a hand touches a hot object, it will retract, an object blinks when it suddenly appears in front of the eyeball, a baby will urinate immediately when there is more urine in the bladder, etc. Like this, the body's regular response to various external or internal stimuli through the nervous system is called simple reflection.

The above-mentioned examples all have one thing in common: when people make these reactions, they are processed by the brain. Why are some reflections beyond the control of the brain? To understand this problem, we need to study the structural basis of reflection-reflex arc.

Analysis: After a student suddenly grabbed a hot hoe, he quickly released his reflection before he could think about it. While completing this reflex, the neurons in the spinal cord that lead to the brain also transmit nerve impulses to the brain, making people feel hot. But because of the longer path to the brain, the fingers were retracted before the brain could make a judgment. Analyzing this example, we can see that reflection is done through a certain neural structure, the reflection arc. The human body has many reflections, and there are many reflection arcs.

Hand-reflex, blinking reflex, urination reflex, and knee reflex are all simple, natural reflexes. As far as this type of reflection is concerned, the normal human body will respond accordingly whenever a stimulus occurs. Through the accumulation of long-term life experience, people can also form complex reflections. For example, classmates quickly enter the classroom when they hear the bell of the class; pedestrians quickly avoid the car horns behind them, and so on. For certain speech stimuli, complex reflections can also form. "Wangmei quenches thirst" is a typical example:

Wei Wu marched, lost his way, and the army was thirsty, but it was said that "there was a large plum forest, Rao Zi, and sour, which can quench thirst." Take this to get to the source. "The New Words of Shiyu · Fake "

Plums are sour, which can stimulate salivary glands to secrete saliva when eaten. This is a reflection. Anyone who has eaten plums can see this reflection when they see plums again-secretion of saliva. Saliva is also secreted when talking about plums, which is related to the nerves at the top of the tower in the cerebral cortex. Language-related reflections are complex and unique to humans.

In general, the human body can adjust its own life activities from simple or complex reflections, so that it can respond appropriately to internal and external stimuli. It can also be said that reflection is a survival method that humans have evolved for a better life and reproduction.

Psychological reflection

Here is an example of molars.

A person bruises his teeth after falling asleep. Bruxism is more common in children, but it is not uncommon among adults, and it is gradually increasing. The oral cavity is one of the first sources of excitement for the human body, a channel for communication with the outside world, and a function to express emotions such as tension and pessimism. when

reflection Today's people's pace of life is constantly accelerating, and competition is becoming more and more intense. Everyone tries to dissipate all kinds of pressures in life or work. One of the effective methods is physical exercise and mental transfer, and some people appear to be grinding teeth, leading to The psychological factors of bruxism often come first. Peking University School of Stomatology has performed a controlled study of 80 patients with bruxism between 16 and 45 years old and 80 people without bruxism. The results show that: introverted personality, depression, emotional instability, easy tension, excessive fatigue, jawbone Showing muscle tension is an important factor in bruxism. When people escape the subconscious psychological pressure, they will bruise their teeth in dreams or sleep. Molar grinding is a symptom of psychological frustration and evidence that a patient must see a psychologist. In addition, abnormal tooth arrangement and jaw shape, discomfort caused by bad tooth contact surface (occlusal disorder), and oral discomfort caused by periodontitis can also cause molars during sleep.

Molars in adults are often not valued. The reason is related to the misunderstanding of adult molars. Someone has done a survey. Of the 40 patients with bruxism and relatives of 60 patients, 62.3% of them think that bruxism does not need to see a doctor. They don't think molars are anything to worry about.

Occasionally, molars have little impact on health, but long-term molars or molars are too long and hard after falling asleep, and the teeth will gradually become loose. Elderly people may even split their teeth and cause gingivitis. The force used when grinding teeth can damage the tissues that support the teeth, and can affect the jaws and muscles, even leading to psychological and physical disorders.

Adults with bruxism should actively seek medical attention and should not be treated sloppy. After ruling out molars caused by a physical disease, one should consider whether there is a mental disorder. If you have a mental disorder, you should adapt yourself or seek treatment from a psychologist. Practice has proven that getting rid of psychological pressure and stabilizing emotions in various ways is the best way to treat bruxism.