About The Brain And Spinal Cord
Together, the brain and spinal cord form the central nervous system. This complex system is part of everything we do. It controls the things we choose to dolike walk and talkand the things our body does automaticallylike breathe and digest food. The central nervous system is also involved with our sensesseeing, hearing, touching, tasting, and smelling as well as our emotions, thoughts, and memory.
The brain is a soft, spongy mass of nerve cells and supportive tissue. It has three major parts: the cerebrum, the cerebellum, and the brain stem. The parts work together, but each has special functions.
The cerebrum, the largest part of the brain, fills most of the upper skull. It has two halves called the left and right cerebral hemispheres. The cerebrum uses information from our senses to tell us what’s going on around us and tells our body how to respond. The right hemisphere controls the muscles on the left side of the body, and the left hemisphere controls the muscles on the right side of the body. This part of the brain also controls speech and emotions as well as reading, thinking, and learning.
The cerebellum, under the cerebrum at the back of the brain, controls balance and complex actions like walking and talking.
The brain stem connects the brain with the spinal cord. It controls hunger and thirst and some of the most basic body functions, such as body temperature, blood pressure, and breathing.
How The Peripheral Nervous System Works
Steven Gans, MD is board-certified in psychiatry and is an active supervisor, teacher, and mentor at Massachusetts General Hospital.
Verywell / Gary Ferster
What exactly is the peripheral nervous system and what role does it play in the body? First, it is important to realize that the nervous system is divided into two parts: the central nervous system and the peripheral nervous system.
The central nervous system includes the brain and spinal cord, while the peripheral nervous system includes all of the nerves that branch out from the brain and spinal cord and extend to other parts of the body including muscles and organs. Each part of the system plays a vital role in how information is communicated throughout the body.
Neural Precursors In Sponges
Sponges have no cells connected to each other by synaptic junctions, that is, no neurons, and therefore no nervous system. They do, however, have homologs of many genes that play key roles in synaptic function in other animals. Recent studies have shown that sponge cells express a group of proteins that cluster together to form a structure resembling a postsynaptic density . However, the function of that structure is currently unclear. Although sponge cells do not show synaptic transmission, they do communicate with each other via calcium waves and other impulses, which mediate some simple actions such as whole-body contraction .
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Who’s Running The Show
Your nervous system works both on autopilot and with you in control. A voluntary action is something that takes conscious thought, like when you walk or clap your hands. That uses the somatic nerves. Involuntary actions are things like your heartbeat that happen whether or not you’re thinking or doing anything about it. That’s the autonomic system.
Cerebral Hemisphere And Cerebral Cortex
The cerebrum has got right and left cerebral hemispheres. The right hemisphere controls and processes signals from the left side of the body, while the left hemisphere controls and processes signals from the right. The cerebral hemispheres and the cerebral cortex covering these hemispheres are located in the uppermost region. They work together and form the intellectual or cognition part of the brain. The three main functions are:
- conscious motor action
The cerebral cortex is the outer layer of cerebral hemispheres that consists of nerve cells. The cerebral cortex constitutes the rational or thinking part of our brain. This is the part where sensations are processed and conscious decisions are made. There are different cortices each associated with one or more sensations. The cerebral cortex is divided into four lobes: Frontal, Parietal, Occipital and Temporal lobes.
The frontal lobe includes the Prefrontal Cortex, premotor area and motor area of the brain. The frontal lobe is associated with executive functions and motor performance. Executive functions are some of the highest-order cognitive processes that humans have. Examples include planning, recognizing future consequences of current actions, choosing between good and bad actions, deciding socially unacceptable responses, determining similarities between objects or situations.
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Everyday Connection: How Much Of Your Brain Do You Use
Figure 6. fMRI This fMRI shows activation of the visual cortex in response to visual stimuli.
An easy way to see how much of the brain a person uses is to take measurements of brain activity while performing a task. An example of this kind of measurement is functional magnetic resonance imaging , which generates a map of the most active areas and can be generated and presented in three dimensions . This procedure is different from the standard MRI technique because it is measuring changes in the tissue in time with an experimental condition or event.
The underlying assumption is that active nervous tissue will have greater blood flow. By having the subject perform a visual task, activity all over the brain can be measured. Consider this possible experiment: the subject is told to look at a screen with a black dot in the middle . A photograph of a face is projected on the screen away from the center. The subject has to look at the photograph and decipher what it is. The subject has been instructed to push a button if the photograph is of someone they recognize. The photograph might be of a celebrity, so the subject would press the button, or it might be of a random person unknown to the subject, so the subject would not press the button.
How Does The Nervous System Work
The basic workings of the nervous system depend a lot on tiny cells called neurons. The brain has billions of them, and they have many specialized jobs. For example, sensory neurons send information from the eyes, ears, nose, tongue, and skin to the brain. Motor neurons carry messages away from the brain to the rest of the body.
All neurons, however, relay information to each other through a complex electrochemical process, making connections that affect the way we think, learn, move, and behave.
Intelligence, learning, and memory. As we grow and learn, messages travel from one neuron to another over and over, creating connections, or pathways, in the brain. It’s why driving takes so much concentration when someone first learns it, but later is second nature: The pathway became established.
In young children, the brain is highly adaptable. In fact, when one part of a young child’s brain is injured, another part often can learn to take over some of the lost function. But as we age, the brain has to work harder to make new neural pathways, making it harder to master new tasks or change set behavior patterns. That’s why many scientists believe it’s important to keep challenging the brain to learn new things and make new connections it helps keeps the brain active over the course of a lifetime.
Smell. Olfactory cells in the mucous membranes lining each nostril react to chemicals we breathe in and send messages along specific nerves to the brain.
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Judgment And Abstract Reasoning
Planning and producing responses requires an ability to make sense of the world around us. Making judgments and reasoning in the abstract are necessary to produce movements as part of larger responses. For example, when your alarm goes off, do you hit the snooze button or jump out of bed? Is 10 extra minutes in bed worth the extra rush to get ready for your day? Will hitting the snooze button multiple times lead to feeling more rested or result in a panic as you run late? How you mentally process these questions can affect your whole day.
The prefrontal cortex is responsible for the functions responsible for planning and making decisions. In the mental status exam, the subtest that assesses judgment and reasoning is directed at three aspects of frontal lobe function. First, the examiner asks questions about problem solving, such as If you see a house on fire, what would you do? The patient is also asked to interpret common proverbs, such as Dont look a gift horse in the mouth. Additionally, pairs of words are compared for similarities, such as apple and orange, or lamp and cabinet.
The Central Nervous System
The brain and spinal cord are the organs of the central nervous system. Because they are so vitally important, the brain and spinal cord, located in the dorsal body cavity, are encased in bone for protection. The brain is in the cranial vault, and the spinal cord is in the vertebral canal of the vertebral column. Although considered to be two separate organs, the brain and spinal cord are continuous at the foramen magnum.
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How Do I Keep My Nervous System Healthy
Your nervous system is the command center for your entire body. It needs care to keep working correctly. See your doctor regularly, eat a healthy diet, avoid drugs, and only drink alcohol in moderation. The best way to avoid nerve damage from disease is to manage conditions that can injure your nerves, such as diabetes.
The Spinal Cord Transmits Signals To And From The Brain And Commands Reflexes
The spinal cord is an elongated cylinder of neuron cell bodies, bundles of axons and other cells, protected by connective tissue and bone. It connects to the brain at the medulla oblongata and runs down the vertebral column, the hollow tunnel enclosed within the vertebrae of the spine. The spinal cord is part of the central nervous system and serves as a kind of superhighway. Sensory information and motor commands travel up and down, heading to and from the brain. These signals speed in and out of the spinal cord via spinal nervesthe on-ramps and off-ramps that branch out to supply the limbs, torso, and pelvis. Some incoming signals demand a simple, immediate response. The spinal cord can shoot out a reflex command without bothering the brain.
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Functions Of The Cerebral Cortex
The cerebrum is the seat of many of the higher mental functions, such as memory and learning, language, and conscious perception, which are the subjects of subtests of the mental status exam. The cerebral cortex is the thin layer of gray matter on the outside of the cerebrum. It is approximately a millimeter thick in most regions and highly folded to fit within the limited space of the cranial vault. These higher functions are distributed across various regions of the cortex, and specific locations can be said to be responsible for particular functions. There is a limited set of regions, for example, that are involved in language function, and they can be subdivided on the basis of the particular part of language function that each governs.
Figure 14.3.4 Types of Cortical Areas:
All Nerves Ultimately Connect To The Brain
There are basically two major types of nerves: sensory and motor. Sensory nerves send information such as touch, temperature, and pain to the brain and spinal cord. Motor nerves send signals from the brain back into the muscles, causing them to contract either voluntarily or reflexively.
The nerves of the peripheral nervous system extend down the spinal canal and branch out in 31 pairs at openings in the vertebrae called foraminae. They are messengers to and from your brain, sending pain signals and initiating movementlike, ‘Hey, take your hand off the stove, it’s hot!’ These nerves reflexively cause your spine to twist and turn when you walk to keep you in balance. And they keep you glued to your car seat as you turn a corner at high speeds!
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Cerebrum And Cerebral Cortex
The cerebrum makes up most of the brain. It is found in the cranial vault. The cerebrum consists of two cerebral hemispheres and five lobes. All lobes are named according to the cranial bones on which they lean: frontal, parietal, temporal, occipital and insular lobes. The insular lobe is hidden just beneath the frontal, temporal, and parietal lobes. Insula means island, which the insular lobe is indeedan isle of gray matter hidden under the surface of the cerebrum.
Youll probably encounter the termlimbic lobe as well, but this is not an actual lobe. Rather its a functional group of interconnected regions of the brain which together control emotions, memory and spatial perception. The cerebrum together with the hippocampus, amygdala, olfactory bulb, and basal ganglia comprise the telencephalon.
The most superficial layer of the cerebrum is the cerebral cortex. It is a layer of grey matter which displays numerous folds , can be categorization structurally or functionally , and is home to areas such as the primary motor cortex and the primary somatosensory cortex, both of which house a homunculus.
White matter connections extend between the cerebral cortex grey matter to other parts of the same cerebral hemisphere to the opposite hemisphere and to structures outside the cortex . Learn more about cerebral cortex and its structure with our study units:
Subdivisions Of The Peripheral Nervous System
The sensory division carries sensory signals by way of afferent nerve fibers from receptors in the central nervous system . It can be further subdivided into somatic and visceral divisions. The somatic sensory division carries signals from receptors in the skin, muscles, bones and joints. The visceral sensory division carries signals mainly from the viscera of the thoracic and abdominal cavities.
The motor division carries motor signals by way of efferent nerve fibers from the CNS to effectors . It can be further subdivided into somatic and visceral divisions. The somatic motor division carries signals to the skeletal muscles. The visceral motor division, also known as the autonomic nervous system, carries signals to glands, cardiac muscle, and smooth muscle. It can be further divided into the sympathetic and parasympathetic divisions.
The sympathetic division tends to arouse the body to action. The parasympathetic divisions tend to have a calming effect.
Nerve fibers of the PNS are classified according to their involvement in motor or sensory, somatic or visceral pathways. Mixed nerves contain both motor and sensory fibers. Sensory nerves contain mostly sensory fibers they are less common and include the optic and olfactory nerves. Motor nerves contain motor fibers.
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Functions Of The Cranial Nerves
Each of the 12 cranial nerves has a specific function within the nervous system.
- The olfactory nerve carries scent information to the brain from the olfactory epithelium in the roof of the nasal cavity.
- The optic nerve carries visual information from the eyes to the brain.
- Oculomotor, trochlear, and abducens nerves all work together to allow the brain to control the movement and focus of the eyes. The trigeminal nerve carries sensations from the face and innervates the muscles of mastication.
- The facial nerve innervates the muscles of the face to make facial expressions and carries taste information from the anterior 2/3 of the tongue.
- The vestibulocochlear nerve conducts auditory and balance information from the ears to the brain.
- The glossopharyngeal nerve carries taste information from the posterior 1/3 of the tongue and assists in swallowing.
- The vagus nerve , sometimes called the wandering nerve due to the fact that it innervates many different areas, wanders through the head, neck, and torso. It carries information about the condition of the vital organs to the brain, delivers motor signals to control speech and delivers parasympathetic signals to many organs.
- The accessory nerve controls the movements of the shoulders and neck.
- The hypoglossal nerve moves the tongue for speech and swallowing.
What Does The Nervous System Do
Your nervous system uses specialized cells called neurons to send signals, or messages, all over your body. These electrical signals travel between your brain, skin, organs, glands and muscles.
The messages help you move your limbs and feel sensations, such as pain. Your eyes, ears, tongue, nose and the nerves all over your body take in information about your environment. Then nerves carry that data to and from your brain.
Different kinds of neurons send different signals. Motor neurons tell your muscles to move. Sensory neurons take information from your senses and send signals to your brain. Other types of neurons control the things your body does automatically, like breathing, shivering, having a regular heartbeat and digesting food.
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What Are The Parts Of The Brain
The brain is made up of three main sections: the forebrain, the midbrain, and the hindbrain.
The forebrain is the largest and most complex part of the brain. It consists of the cerebrum the area with all the folds and grooves typically seen in pictures of the brain as well as some other structures under it.
The cerebrum contains the information that essentially makes us who we are: our intelligence, memory, personality, emotion, speech, and ability to feel and move. Specific areas of the cerebrum are in charge of processing these different types of information. These are called lobes, and there are four of them: the frontal, parietal, temporal, and occipital lobes.
The cerebrum has right and left halves, called hemispheres. They’re connected in the middle by a band of nerve fibers that lets them communicate. These halves may look like mirror images of each other, but many scientists believe they have different functions:
- The left side is considered the logical, analytical, objective side.
- The right side is thought to be more intuitive, creative, and subjective.
So when you’re balancing your checkbook, you’re using the left side. When you’re listening to music, you’re using the right side. It’s believed that some people are more “right-brained” or “left-brained” while others are more “whole-brained,” meaning they use both halves of their brain to the same degree.
In the inner part of the forebrain sits the thalamus, hypothalamus, and :