When the danger is gone, the parasympathetic nervous system lets the person "rest and digest," "feed and breed. The parasympathetic nervous system has many different effects. It affects every part of the body, including:. The heart: The heart relaxes and beats slower. This makes the heart rate and blood pressure lower.
The lungs: Breathing slows down. The bronchi the tubes that bring air to the lungs also get narrower. The eyes: The pupils get smaller. The digestive system: Extra blood is sent to the stomach and intestines. The stomach and intestines also work faster. This helps the person digest the food in their stomach. The blood vessels: The blood vessels in the parts of the body that are far away from the heart, lungs, and brain get wider.
This is called vasodilation. This helps make the blood pressure lower. It also makes the skin warmer, and can cause a man to have an erection. Because of these effects, the parasympathetic nervous system always has to balance with the sympathetic nervous system. For example, if only the parasympathetic nervous system was working, a person's heart rate and breathing would keep getting lower and lower. Eventually the person would stop breathing or their heart would stop beating. However, in a healthy person, the brain realizes when the parasympathetic nervous system's effects are getting too strong.
For example, the brain may realize that the person is breathing too slowly, or that their heart rate is too low. The brain reacts by making the sympathetic nervous system kick in. Because the sympathetic nervous system has the opposite effects, it will make the person breathe faster and raise their heart rate. These two systems have to balance each other constantly for a person to stay healthy.
The parasympathetic nervous system is controlled mostly by the vagus nerve. The vagus nerve sends out chemical messengers called neurotransmitters - mostly one called acetylcholine. The somatic nervous system SNS is part of the peripheral nervous system. The SNS controls voluntary body movements by skeletal muscles.
Its outgoing efferent nerves stimulate muscle contraction. Its incoming afferent nerves relay sensation from the skin, and sense organs to the central nervous system. This includes touch, hearing, and sight. Eyes are the organs that provide the sense of sight are delicate instruments resting in protective sockets at the front of the skull.
Front of the eyeball is constantly bathed with a watery liquid referred to as tears it comes from tear glands. The eyelids are small windshield wipers spread this fluid over the eyeballs with a frequent blinking action it keeps the eyeballs clean and moist.
The liquid contains chemicals that kill harmful bacteria that may be present. The tear gland are stimulated either by emotion or by a speck of dust or other foreign particle in the eye to produce more liquid than can be drained off. The eye is like a video camera that is supplying the brain with pictures of everything that is in front of it. The outside of the eyeball is a white except for a transparent window at the front the cornea.
Behind the thin clear covering is the iris is the colored part of the eye that opens and closes like a diaphragm camera.
- Bad Kitty: Paranormal Shifter Romance (Southern Shifters Book 4);
- Navigation menu.
- Time and Relative Dimension in Lace - A Gallifreyan-Irish crochet shawl pattern.
- Boundary Methods: Elements, Contours, and Nodes (Mechanical Engineering).
Behind the iris is a convex lens and the opening in the center of iris is called pupil. Light passes through the lens which bends the light and focuses it onto the back of the eyeball. The lining of the back of the eyeball is the retina is filled with light sensitive nerve endings that are connected to the optic nerve it carries the impulses to the brain and it converts these impulses to images and we experience sigh. The retina contains cones that respond to color and objects in bright light and the rods respond to objects in dim light but they do not respond to color it explains why the things we see in dim light appear only in shades of black and white.
The significance of the auditory canal must not be overlooked because in a distance of about 2. The wax also protects against infection and should not be removed with toothpicks or other instruments. The process of hearing really takes place inside the head. The outer ear the body auditory apparatus includes structures within the middle ear and inner ear.
- Age of Satan (The Pantheon Series).
- Human nervous system.
- Respiratory System;
The middle ear consists of the eardrum and three small bones called hammer and stirrup. The hammer is connected to the inside of the eardrum and sound waves cause the eardrum to vibrate the hammer vibrates also. Some may be quite small while others may be up to one meter long.
Similarly, nerves can vary in size as well. As your PNS branches out, your nerves tend to get smaller. The sciatic nerve is the largest nerve in your body. It begins in your lower back and travels all the way down to the heel of your foot.
You may have heard of a condition called sciatica in which painful sensations radiate from your lower back and down your leg. This happens when the sciatic nerve is compressed or irritated.
A Nurse's Guide to the Human Body | Regis College Online
They can travel at a speed of up to meters per second. Your brain is divided up into different parts , each with different functions. Integration of these functions helps us to perceive and react to internal and external stimuli. Your brain weighs about three pounds.
How Many Nerves Are in The Human Body?
This is small in comparison to your overall body weight, but according to the Smithsonian Institute, your brain gets 20 percent of your oxygen supply and blood flow. A special barrier called the blood-brain barrier prevents harmful substances in the blood from entering your brain. Since the first neurotransmitter was discovered in , more than substances have been implicated in signal transmission between nerves.
A couple that you may be familiar with are dopamine and serotonin.
Researchers are hard at work to develop ways to repair damage to the nervous system. This is accomplished using a device that sends electrical signals to your vagus nerve. This, in turn, sends signals to specific parts of the brain. Vagus nerve stimulation can help to lower the number of seizures in people with some types of epilepsy. Its effectiveness is being assessed for conditions like headaches and rheumatoid arthritis as well.
A study in mice used imaging to visualize nerve cells surrounding fat tissue. Researchers found that stimulating these nerves also stimulated the breakdown of fat tissue. Additional research is needed, but this could have implications for conditions like obesity. The system is able to collect information on applied pressure and convert it into electric impulses that can be integrated on a transistor.
This transistor then releases electrical impulses in patterns consistent with those produced by neurons. This vast system of nerves works together as a communication network.
Related The Nervous System (The Human Body, How It Works)
Copyright 2019 - All Right Reserved