The human body consists of organs of the body which each have a certain function. In order for the organs of the body to work together properly, coordination is required. In humans and most animals, coordination is done by the nervous system, the sensory system, and the hormonal system. In this chapter will only be discussed two of them, namely the nervous system and the sensory system.
A. NUTS SYSTEM
The nervous system plays a role in the irritability of the body. Do you know what is irritability? Irritability allows living things to adapt and respond to changes in their environment. Thus, irritability is the ability to respond to stimuli.
The nervous system has three main functions: receiving information in the form of stimuli or stimuli; process the information received; as well as giving response (response) to the stimulus.
The smallest unit of the nervous system is a neuron called a neuron. Each one nerve cell (neuron) consists of a major part of the body of nerve cells, dendrites, and axons.
The body of a nerve cell is the largest part of the nerve cell. Inside is the nucleus and cytoplasm. Inside the cytoplasm there is a functioning mitochondrial to generate energy to bring stimulation.
The nervous system plays a role in the irritability of the body. Do you know what is irritability? Irritability allows living things to adapt and respond to changes in their environment. Thus, irritability is the ability to respond to stimuli.
The nervous system has three main functions: receiving information in the form of stimuli or stimuli; process the information received; as well as giving response (response) to the stimulus.
The smallest unit of the nervous system is a neuron called a neuron. Each one nerve cell (neuron) consists of a major part of the body of nerve cells, dendrites, and axons.
The body of a nerve cell is the largest part of the nerve cell. Inside is the nucleus and cytoplasm. Inside the cytoplasm there is a functioning mitochondrial to generate energy to bring stimulation.
Dendrites are fibers that are cytoplasmic bulges and serve to pass nerve impulses to the body of nerve cells. Dendrites are branches of nerve cell bodies that usually amount to more than one in each neuron. Axons or neurites are long cytoplasmic bulges (longer than dendrites), serve to pass nerve impulses leaving nerve cell bodies to neurons or other tissues. The number of axons is usually only one on each neuron. In it there are fine threads called neurofibrils. At the far end of the nerve cell body there are branches associated with dendrites from other nerve cells. Axons are encased by several layers of myelin membranes that contain lots of fat. Myelin membranes are composed by Schwann cells. The outer myelin layer is called neurilema. The layer serves to protect the axon from damage. Schwann cells form a network that helps provide food for neurites and helps regenerate neurites. Myelin envelope segment-segmented. The indentation between two segments is called the ranvier node. The ranvier node works to speed up the transmission of nerve impulses. The existence of the ranvier node allows the nerve to jump from one node to another, so that the impulse is faster to the destination.
The encounter between the nerve fibers of one nerve cell and the nerve fibers of another is called a synapsesis. In each synapse there is a synaptic cleft. Synapses also act as a link between the end of the axon of one nerve cell with the other end of the dendrites of another. At the end of the axon there is a bag called a bulbus axon. The bag contains a chemical called a neurotransmitter. Neurotransmitters may be acetylcholine and cholinesterase which function in the delivery of nerve impulses in synapses.
Types of Neurons
According to its function, neurons are divided into three kinds: sensory neurons, motor neurons, and association neurons. Sensory neurons are also called sensory neurons, because they function to pass the stimuli from the senses to the central nerves (brain and spinal cord). This nerve cell bodies clustered into ganglia, short axons, and long dendrites. Motor neurons (nerve cell drive) serves to carry impulses from the central nerves (brain) and spinal cord to the muscles. These nerve cells have short dendrites and long axons. Associated neurons or connecting nerve cells are present in the brain and spinal cord. The neurons function to connect or forward the impulses from the sensory nerve cells to the motor nerve cells.
Human Neural Arrangement
The human nervous system is like a telephone network that functions as a communication tool. If you call someone your voice will propagate through the phone cord to the phone control center. Here your voice is moved to another cable that connects it with the phone of the person you are headed to. In the same way an impulse that travels through the nerve to the central nervous system as a controller will coordinate the activity of the body.
According to its function, neurons are divided into three kinds: sensory neurons, motor neurons, and association neurons. Sensory neurons are also called sensory neurons, because they function to pass the stimuli from the senses to the central nerves (brain and spinal cord). This nerve cell bodies clustered into ganglia, short axons, and long dendrites. Motor neurons (nerve cell drive) serves to carry impulses from the central nerves (brain) and spinal cord to the muscles. These nerve cells have short dendrites and long axons. Associated neurons or connecting nerve cells are present in the brain and spinal cord. The neurons function to connect or forward the impulses from the sensory nerve cells to the motor nerve cells.
Human Neural Arrangement
The human nervous system is like a telephone network that functions as a communication tool. If you call someone your voice will propagate through the phone cord to the phone control center. Here your voice is moved to another cable that connects it with the phone of the person you are headed to. In the same way an impulse that travels through the nerve to the central nervous system as a controller will coordinate the activity of the body.
In order to more easily understand the human nerves, consider the following chart.a. Central nerve systemThe central nervous system consists of the brain and spinal cord.
1) BrainThe brain is the center of coordination within the human body. The brain is in the cranial cavity, precisely in front of the spinal cord, and is covered by a membrane. The membranes that envelop the brain are called membranes of the membranes. This membrane is divided into three parts, namely the outermost layer attached to the bone (Duramater), the middle layer in the form of spider web (arachnoid), and the inner layer that is attached to the surface of the brain (piamater). Between arachnoid and piamater there is a space filled with fluid that is the protector of the brain, in case of a collision. The parts of the brain include the cerebrum (cerebrum), cerebellum (cerebellum), middle brain (mesensefalon), and marrow advanced (medulla oblongata). The large brain has multiple surfaces and has two layers, the thin layer on the outside (the cortex) and the thick layer on the inside (medulla). Gray cortex contains the body of nerve cells, while the white medulla contains dendrites and axons. Large human brains have several parts with their respective functions. The large brain of the back is the center of vision, while the side is the center of hearing. The middle of the cerebrum is the central regulator of skin and muscle sensitivity associated with heat, cold, touch, and pressure stimuli. In the center and back of the cerebrum there are regions as central to the development of intelligence, attitude, personality, and memory.
1) BrainThe brain is the center of coordination within the human body. The brain is in the cranial cavity, precisely in front of the spinal cord, and is covered by a membrane. The membranes that envelop the brain are called membranes of the membranes. This membrane is divided into three parts, namely the outermost layer attached to the bone (Duramater), the middle layer in the form of spider web (arachnoid), and the inner layer that is attached to the surface of the brain (piamater). Between arachnoid and piamater there is a space filled with fluid that is the protector of the brain, in case of a collision. The parts of the brain include the cerebrum (cerebrum), cerebellum (cerebellum), middle brain (mesensefalon), and marrow advanced (medulla oblongata). The large brain has multiple surfaces and has two layers, the thin layer on the outside (the cortex) and the thick layer on the inside (medulla). Gray cortex contains the body of nerve cells, while the white medulla contains dendrites and axons. Large human brains have several parts with their respective functions. The large brain of the back is the center of vision, while the side is the center of hearing. The middle of the cerebrum is the central regulator of skin and muscle sensitivity associated with heat, cold, touch, and pressure stimuli. In the center and back of the cerebrum there are regions as central to the development of intelligence, attitude, personality, and memory.
The function of the human small brain is as a regulator of the balance of the body and as the center of coordination of muscle work when moving. Small brain consists of two parts, namely the left and right. Both sections are connected by a varol bridge. Varol bridge serves to deliver the impulse muscles of the right and left body.
The middle brain is located in front of the cerebellum and the varol bridge. The upper half of the midbrain is the center of the eye reflex and the hearing center. Advanced marrow is also called the marrow or brainstem. Further marrow has several functions, namely as a central regulator of breathing, heart rate, body temperature, and the center of dilation and constriction of blood vessels. Advanced marrow or marrow connective tissue is the link between the brain and the spinal cord.
The middle brain is located in front of the cerebellum and the varol bridge. The upper half of the midbrain is the center of the eye reflex and the hearing center. Advanced marrow is also called the marrow or brainstem. Further marrow has several functions, namely as a central regulator of breathing, heart rate, body temperature, and the center of dilation and constriction of blood vessels. Advanced marrow or marrow connective tissue is the link between the brain and the spinal cord.
2) Spinal cordThe spinal cord has two main functions, namely as a connective impulse coming from the brain as well as the center of reflex motion. The spinal cord (spinal cord) occupies the spinal cavity and is elongated. The membrane lining is the same as the brain, consisting of duramater, arachnoid, and piamater. The cross section of the spinal cord is divided into two parts, namely the inside and the outside. The inside is gray, many contain nerve cells and connecting nerve cells. The outside is white, and contains many nerve fibers.
The peripheral nervous system
According to its origin or relationship, the peripheral nervous system is distinguished into the brain's nerves and spinal cord nerves. The brain's nerves are the nerves that go from the brain to the sensory devices, such as the eyes, ears, nose, or to certain muscles and glands. The brain nerve consists of 12 pairs. The spinal cord's nerves are the nerves that come out of the spinal cord to the body's alatalate, such as the arms and legs, and other body muscles such as the chest and neck muscles. The nerve consists of 31 pairs. This nerve is a combination of sensory and motor neurons
In addition to these two nerves, the nervous system also has an unconscious nerve. Unconscious nerves are nerves that function to regulate the activities of organs that work out of consciousness. Unconscious nerves are often called autonomic nerves. The unconscious nerve consists of the sympathetic nervous system and the parasympathetic nervous system. Both nervous systems work against each other.
The sympathetic nervous system has a nerve or ganglion node along the front of the spine, starting at the bottom of the neck to the coccyx. Each nerve node is interconnected, making it into two rows, the left and right rows. Each knot is connected by the spinal cord. From each node there are nerves that go to the kidneys, lungs, heart, and other organs. Sympathetic nerve function, among others, wrinkle the hair skin, speed up the heartbeat, widen the blood vessels, and increase blood pressure.
The parasympathetic nervous system is a web of interconnected ganglions scattered throughout the body. The function of the parasympathetic nerve goes against the sympathetic nervous function. Parasympathetic nerve function, among others, develops hair skin, slows the heart rate, narrows the blood vessels, and lowers blood pressure.
The peripheral nervous system
According to its origin or relationship, the peripheral nervous system is distinguished into the brain's nerves and spinal cord nerves. The brain's nerves are the nerves that go from the brain to the sensory devices, such as the eyes, ears, nose, or to certain muscles and glands. The brain nerve consists of 12 pairs. The spinal cord's nerves are the nerves that come out of the spinal cord to the body's alatalate, such as the arms and legs, and other body muscles such as the chest and neck muscles. The nerve consists of 31 pairs. This nerve is a combination of sensory and motor neurons
In addition to these two nerves, the nervous system also has an unconscious nerve. Unconscious nerves are nerves that function to regulate the activities of organs that work out of consciousness. Unconscious nerves are often called autonomic nerves. The unconscious nerve consists of the sympathetic nervous system and the parasympathetic nervous system. Both nervous systems work against each other.
The sympathetic nervous system has a nerve or ganglion node along the front of the spine, starting at the bottom of the neck to the coccyx. Each nerve node is interconnected, making it into two rows, the left and right rows. Each knot is connected by the spinal cord. From each node there are nerves that go to the kidneys, lungs, heart, and other organs. Sympathetic nerve function, among others, wrinkle the hair skin, speed up the heartbeat, widen the blood vessels, and increase blood pressure.
The parasympathetic nervous system is a web of interconnected ganglions scattered throughout the body. The function of the parasympathetic nerve goes against the sympathetic nervous function. Parasympathetic nerve function, among others, develops hair skin, slows the heart rate, narrows the blood vessels, and lowers blood pressure.
Ordinary Motion and Reflex MotionA movement occurs usually begins with a stimulus. Movements that occur there are we realize before and there are we realize after the movement. Based on this, the motion can be divided into two, namely the usual motion and reflex motion.a. Ordinary motionIn the rainy season, you often rain and feel cold. In order not to rain, you often carry an umbrella before traveling.
How does the umbrella open in the rain? The process starts from the presence of rain dots that affect the receptors on the skin. The receptor then sends impulses of raindrops along the sensory neuron to the neurons of the association within the spinal cord, then proceeds to the brain. The brain processes impulse "raindrops" and then decides to open the umbrella. From the brain the impulse "open the umbrella" is sent through the neurons of the association to the next spinal cord into the motor neurons in your hand. Finally your hand immediately moves open the umbrella.
The movement to open the umbrella, as exemplified in the above description is a movement that you have noticed before. In other words the motion occurs because of the command of the brain. Such motion is called ordinary motion. The course of the usual motion stimuli can be summarized as follows.
Stimulants - Receptors - Sensory nerves - Brain - Motor nerves - Effects - Movementb. Reflex motionWhen walking, accidentally your feet punctured a sharp nail. What do you do when your foot is punctured by a sharp nail while walking? The nails on your feet are the stimuli (impulses) received by the skin of the foot. The impulse is transmitted by the sensory neuron to the spinal cord which immediately passes it on to neurons
association. From the neurons of the association, the impulse moves into the motor neuron which then passes it on to your leg muscles. Finally you pull your legs up quickly. The movement of your foot is only controlled by the spinal cord, while your brain is not involved. So, you do not realize when lifting the pierced leg. This kind of movement is called reflex motion. Reflex motion occurs rapidly as an automatic reaction to stimuli from the environment. The way through which stimulation of reflex motion is as follows.Stimulants - Receptors - Sensory nerves - Spinal cord - Motor nerves - Efektor - Movement
In general, reflex motion is our body's effort to avoid danger. One time when the impulse has reached the spinal cord, the neuron association sends another impulse to the brain. When the impulse reaches the brain, you realize that you have lifted your legs because of the pain of nails.
According to the center of the occurrence of reflexes, reflex motion is divided into two, namely the brain reflex and spinal cord reflex. Brain reflexes, such as the blink of the eye. The path of the eye reflex is not through the spinal cord, but directly to the brain. As for, the brain responds beyond the control of the human conscious will. Spinal cord reflex, for example knee reflex. The reflex motion is centered on the spinal cord.
INDRA TOOLS Learning ObjectivesHumans as a member of the mammalian class have five senses, namely the sense of sight, listener, touch, smell, and taste. By having these senses, man is able to recognize his environment and respond to changes that occur. Indra is the "window" for the body to know the outside world. In addition, with the receptors that exist in each sensory device, humans are able to conduct a response that can be used as an effort to protect against disturbances from outside the body
1. The sense of sightThe human eye vision. At the time of science class VIII, you have studied the eyes as an optical tool. As for, the eye as the sense of vision has certain parts that make up the vision system.
According to the center of the occurrence of reflexes, reflex motion is divided into two, namely the brain reflex and spinal cord reflex. Brain reflexes, such as the blink of the eye. The path of the eye reflex is not through the spinal cord, but directly to the brain. As for, the brain responds beyond the control of the human conscious will. Spinal cord reflex, for example knee reflex. The reflex motion is centered on the spinal cord.
INDRA TOOLS Learning ObjectivesHumans as a member of the mammalian class have five senses, namely the sense of sight, listener, touch, smell, and taste. By having these senses, man is able to recognize his environment and respond to changes that occur. Indra is the "window" for the body to know the outside world. In addition, with the receptors that exist in each sensory device, humans are able to conduct a response that can be used as an effort to protect against disturbances from outside the body
1. The sense of sightThe human eye vision. At the time of science class VIII, you have studied the eyes as an optical tool. As for, the eye as the sense of vision has certain parts that make up the vision system.
a. Parts of the eyeBall-shaped eyes, slightly flat from front to back. Eyeball or eyelids are located in the eye socket and covered by skull bones. The outside of the eyeball is protected by the eyelid. Just above the outer corner of the eye there is a tear gland that serves to wet and clean the surface of the eye.Eyeballs attached to the eye cavity wall through three pairs of muscles. The three pairs of muscles that serve to move the eyeball. If working the right eye muscles and left eye muscles mismatched there will be an abnormality called juling.
The basic parts of the eye are briefly described as follows.
1) CorneaThe sclera is the outermost, hard and white wall, usually called the white part. The front is protruding and translucent (transparent) is called the cornea. The cornea helps to focus the shadow of objects on the retina. The cornea has a thin membrane called the conjunctiva.
2) PupilThe second layer of the eyeball is the choroid. The layer is the middle layer called the blood membrane because there are many blood vessels except at the front. At the front of the layer is slightly open called pupils. Pupils are located just behind the center of the cornea. Pupils can change in size depending on the intensity of light entering the eye. This change occurs reflexively. When light is very bright or strong, the pupil will narrow or experience the contraction, otherwise when the light is dim, the pupils will dilate or dilate. Around the pupil there is an area containing pigment and called iris. Pigment is what causes the difference in eye color, until there are people with blue eyes, black, brown, green, and so forth.
3) EyepieceAt the back of the pupil there is a convex section, the lens. The lenses are supported by muscles called ciliary muscles (circular flesh muscles). If the muscle is experiencing contraction will change the lens size. It happens when you make a careful observation that is fixed on a particular object either at a distance or near. Note Figure 3.11. The ability of the eyepiece is called the eye accommodation power. Of course you still remember this term while studying science in class VIII.
The space between the lens and cornea contains a dilute fluid called aqueous humor. On the inside of the eyeball filled with viscous and transparent liquid. Substance (material) is what causes the eyeball becomes strong. This fluid is called vitreous humor. The fluid present between the cornea and the lens is usually more dilute, while between the lens and the retina resembles gelatin. If too much fluid in the eye will occur disorders called glaucoma. This disease can cause blindness if not treated.4) RetinaThe retina is the deepest, very complex, and soft layer of the eye. In the deepest part of the retina there are several layers of cells, namely receptors, ganglia, and nerve fibers. Retina contains receptors to receive light stimuli, so this receptor is called photoreceptors. In the retina there is a point or spot that has no stem cells or cones called blind spots.
2) PupilThe second layer of the eyeball is the choroid. The layer is the middle layer called the blood membrane because there are many blood vessels except at the front. At the front of the layer is slightly open called pupils. Pupils are located just behind the center of the cornea. Pupils can change in size depending on the intensity of light entering the eye. This change occurs reflexively. When light is very bright or strong, the pupil will narrow or experience the contraction, otherwise when the light is dim, the pupils will dilate or dilate. Around the pupil there is an area containing pigment and called iris. Pigment is what causes the difference in eye color, until there are people with blue eyes, black, brown, green, and so forth.
3) EyepieceAt the back of the pupil there is a convex section, the lens. The lenses are supported by muscles called ciliary muscles (circular flesh muscles). If the muscle is experiencing contraction will change the lens size. It happens when you make a careful observation that is fixed on a particular object either at a distance or near. Note Figure 3.11. The ability of the eyepiece is called the eye accommodation power. Of course you still remember this term while studying science in class VIII.
The space between the lens and cornea contains a dilute fluid called aqueous humor. On the inside of the eyeball filled with viscous and transparent liquid. Substance (material) is what causes the eyeball becomes strong. This fluid is called vitreous humor. The fluid present between the cornea and the lens is usually more dilute, while between the lens and the retina resembles gelatin. If too much fluid in the eye will occur disorders called glaucoma. This disease can cause blindness if not treated.4) RetinaThe retina is the deepest, very complex, and soft layer of the eye. In the deepest part of the retina there are several layers of cells, namely receptors, ganglia, and nerve fibers. Retina contains receptors to receive light stimuli, so this receptor is called photoreceptors. In the retina there is a point or spot that has no stem cells or cones called blind spots.
Eye astigmatismThe eye of the astigmatism is an eye defect caused by an uneven corneal congestion, so that the parallel rays that come can not be focused to a single point. To help astigmatism sufferers wear cylindrical goggles.
5) Hemeralopi (night blindness)Hemeralopi is an eye disorder caused by lack of vitamin A. Patients with night blindness can not see clearly at dusk. Circumstances like that if allowed to continue to cause cornea the eyes can be damaged and can cause blindness. Therefore, adequate vitamin A is necessary.
6) CataractsCataracts are eye defects caused by calcification of the lens of the eye so that the vision becomes blurred and the power of accommodation is reduced. Generally, cataract attacks elderly people.
7) Color blindnessColor blindness is a diminished eye vision disorder. Color blind people are not able to distinguish certain colors, such as red, green, or blue. Color blind can not be repaired or cured.
2. Indra of Listener and Tool of BalanceThe human ear is a very complex organ. The human ear is an open channel on the outside and united with the skull bone. The ear is an organ that functions to hear sounds or sounds. The sounds we can hear are voices that have frequencies between 20 Hz-20,000 Hz.a. Parts of the earThe human ear consists of three parts: the outer ear, the middle ear, and the inner ear. The outer ear consists of earlobes, outer ear canal, and eardrum (tympanic membrane). The ear leaves are composed of cartilage. The outer ear canal of the wall can produce serum oil. The function of the outer ear is to catch the sound vibration.
The middle ear has a wide range of bones, namely the hammer bone, the base bone, and the stoop bone. These three bones form a series across the middle ear and unite with the tympanic membrane. At the end of the middle ear, the stirrup bones unite with the membrane, called a round window. This round window covering the inner ear. The inner ear is composed of two important parts, namely: snails and ducts. The snail house is a spiral channel that resembles a snail's house. This channel contains fluid and the inner surface is a place of nerves. The nerve endings are very sensitive to the vibrations generated by the liquid. All these nerve endings coalesce into the listener's nerve that connects the snail's house with the brain. The bracket consists of three interconnected channels, and has a role in maintaining balance.
5) Hemeralopi (night blindness)Hemeralopi is an eye disorder caused by lack of vitamin A. Patients with night blindness can not see clearly at dusk. Circumstances like that if allowed to continue to cause cornea the eyes can be damaged and can cause blindness. Therefore, adequate vitamin A is necessary.
6) CataractsCataracts are eye defects caused by calcification of the lens of the eye so that the vision becomes blurred and the power of accommodation is reduced. Generally, cataract attacks elderly people.
7) Color blindnessColor blindness is a diminished eye vision disorder. Color blind people are not able to distinguish certain colors, such as red, green, or blue. Color blind can not be repaired or cured.
2. Indra of Listener and Tool of BalanceThe human ear is a very complex organ. The human ear is an open channel on the outside and united with the skull bone. The ear is an organ that functions to hear sounds or sounds. The sounds we can hear are voices that have frequencies between 20 Hz-20,000 Hz.a. Parts of the earThe human ear consists of three parts: the outer ear, the middle ear, and the inner ear. The outer ear consists of earlobes, outer ear canal, and eardrum (tympanic membrane). The ear leaves are composed of cartilage. The outer ear canal of the wall can produce serum oil. The function of the outer ear is to catch the sound vibration.
The middle ear has a wide range of bones, namely the hammer bone, the base bone, and the stoop bone. These three bones form a series across the middle ear and unite with the tympanic membrane. At the end of the middle ear, the stirrup bones unite with the membrane, called a round window. This round window covering the inner ear. The inner ear is composed of two important parts, namely: snails and ducts. The snail house is a spiral channel that resembles a snail's house. This channel contains fluid and the inner surface is a place of nerves. The nerve endings are very sensitive to the vibrations generated by the liquid. All these nerve endings coalesce into the listener's nerve that connects the snail's house with the brain. The bracket consists of three interconnected channels, and has a role in maintaining balance.
b. Mechanism of hearingWhen it comes to our ears, sound waves will enter the outer ear through the auditory canal and eventually reach the tympanic membrane. These sound waves vibrate membranes and hammer bones. Furthermore, the ground bone and the stirrup bones come shaking. Finally the round window shook as well. This vibration will vibrate the fluid inside the snail's house. The vibrating fluid stimulates the nerve endings. The impulse of this nerve endings is transmitted to the listener's nerves in the cerebrum. The peculiarity of the impulse pattern is determined by the received sound wave pattern. Big brain receives this impulse, then translates it and we perceive it as sound.
c. Abnormalities and diseases of the sense of hearing
The ears as the senses of the listener may be impaired by an abnormality or disease. Disturbance to the sense of hearing may cause hearing to become less sensitive. These conditions include, among others, the thickening of the tympanic membrane due to recurrent infections in the middle ear, rupture of the tympanic membrane, calcification of the hearing bone, and auditory nerve damage (auditory nerve).
The ears as the senses of the listener may be impaired by an abnormality or disease. Disturbance to the sense of hearing may cause hearing to become less sensitive. These conditions include, among others, the thickening of the tympanic membrane due to recurrent infections in the middle ear, rupture of the tympanic membrane, calcification of the hearing bone, and auditory nerve damage (auditory nerve).
3. Indra Touch
The sense of touch in the human body is the skin. In the skin there are some special sensory organs called receptors. The receptor is the final branching of the dendrites of the sensory neurons. Some receptors are composed of several dendrites and some have specialized cells. Each receptor is only suitable for certain types of stimuli only. If the receptor is stimulated, impulse occurs along the dendrites passed to the central nervous system. There are five kinds of receptors on the skin, which is a special receptor to respond to excitations in the form of touch, pressure, pain, heat, or cold.
For example, pain receptors are receptors with bare dendrites, present all over the skin surface. If the stimuli are strong enough, such as mechanical stimuli, temperature, electric or chemical, then these receptors will react. The sensation of pain that arises is an attempt to protect (protect themselves). This is a signal (sign) that there is a threat to the body that can cause injury.
The sense of touch in the human body is the skin. In the skin there are some special sensory organs called receptors. The receptor is the final branching of the dendrites of the sensory neurons. Some receptors are composed of several dendrites and some have specialized cells. Each receptor is only suitable for certain types of stimuli only. If the receptor is stimulated, impulse occurs along the dendrites passed to the central nervous system. There are five kinds of receptors on the skin, which is a special receptor to respond to excitations in the form of touch, pressure, pain, heat, or cold.
For example, pain receptors are receptors with bare dendrites, present all over the skin surface. If the stimuli are strong enough, such as mechanical stimuli, temperature, electric or chemical, then these receptors will react. The sensation of pain that arises is an attempt to protect (protect themselves). This is a signal (sign) that there is a threat to the body that can cause injury.
4. Scrub Indra
The sense of smell in our body is the nose. In the upper nasal cavity there are nerve fibers of the smell with the cells of the smell at the end. The nerve fibers merge into the nerves of the scaffolding that goes to the brain's central smell. Smell cells have fine hairs on their ends and are covered with mucous membranes that serve as a moisturizer. The smell cells are sensitive to chemicals in the air (in the form of gas or steam). At the time of the body the flu is usually accompanied by a cold. Colds cause the respiratory tract to become blocked, especially in the nose. At the time of the cold, the nose is not sensitive to the smell (smell) and the appetite is reduced because the tongue is not sensitive to taste. Is there a connection between the sense of smell (smell) and the sense of taste.
As we inhale, air enters into the nasal cavity. The gas enters the nasal cavity mixed with the mucus, then stimulates the nerve endings. These impulses are passed on to the nerve nerves in the central nerves, and are eventually interpreted as odors. This sense of smell (smell) is related to the sense of taste. If there is interference with the sense of smell, we can not taste well.
5. Taste SenserHumans sometimes prefer some foods rather than other foods. That's because they can sense the difference in the chemical substance in the food. Like other senses, tasting is the result of stimulation of certain nerve endings.
In humans, the taste nerve ends are located in the taste buds on the tongue. Taste buds have a pumpkin-like shape, located on the tongue on the front to the back. Food chewed with saliva enters the tasting bud through the upper pores. In the mouth, food will stimulate the nerve endings that have hair. From the end the message will be brought to the brain, then interpreted and as a result we can taste the food that goes into our mouth
Humans are only able to taste four kinds of flavors, namely sour taste, salty, sweet, and bitter. Taste buds on the tongue for each flavor are located in different areas. For the sweet taste is at the tip of the tongue while the front of the tongue to taste salty. Taste buds for sour taste are on the side of the tongue. As for, the taste buds for the bitter taste are on the back of the tongue. This is why when you eat foods that have a sweet and bitter taste at once, then that feels earlier is a sweetness then taste bitter.
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