The Brain Is Super Vulnerable
Your brain and your spinal cord together form what we call the central nervous system. Looking at a skeleton, have you ever asked yourself why the brain and spinal cord are the only organs in our body encased in bone? True, the lungs and the heart are also well protected by the rib cage. But when you look at the skull, it is basically a bony box with a few holes in it to let nerves leave the brain. The nervous system is unique compared to many other organs in that it does not expand or contract like your heart, lungs, and intestines do. Because there is no major movement, it is alright for the central nervous system to be entirely encased in bone. Why is the central nervous system so well protected? The answer is simple: because it is super sensitive and very vulnerable.
Which organ of your body do you think youre injuring most often? Probably, your skin. Think about a time when you fell, your skin broke open and you had a wound like a scrape or a cut for some time. If this injury happened a while ago, chances are you wont even see the spot on your skin any more. Or maybe you can see a scar, but basically your skin was able to repair itself almost perfectly. Unfortunately, the brain and spinal cord are fundamentally different. If your brain gets injured, some damage may persist throughout the rest of your life.
Central Nervous System: Brain And Spinal Cord
Our bodies couldnt operate without the nervous system – the complex network that coordinates our actions, reflexes, and sensations. Broadly speaking, the nervous system is organised into two main parts, the central nervous system and the peripheral nervous system .
The CNS is the processing centre of the body and consists of the brain and the spinal cord. Both of these are protected by three layers of membranes known as meninges. For further protection, the brain is encased within the hard bones of the skull, while the spinal cord is protected with the bony vertebrae of our backbones. A third form of protection is cerebrospinal fluid, which provides a buffer that limits impact between the brain and skull or between spinal cord and vertebrae.
Prenatal And Postnatal Development Of The Human Nervous System
Almost all nerve cells, or neurons, are generated during prenatal life, and in most cases they are not replaced by new neurons thereafter. Morphologically, the nervous system first appears about 18 days after conception, with the genesis of a neural plate. Functionally, it appears with the first sign of a reflex activity during the second prenatal month, when stimulation by touch of the upper lip evokes a withdrawal response of the head. Many reflexes of the head, trunk, and extremities can be elicited in the third month.
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Central Nervous System Definition
- The central nervous system consists of the brain and spinal cord.
- The brain plays a central role in the control of most bodily functions, including awareness, movements, sensations, thoughts, speech, and memory.
- Some reflex movements can occur via spinal cord pathways without the participation of brain structures.
- The spinal cord is connected to a section of the brain called the brainstem and runs through the spinal canal.
- Cranial nerves exit the brainstem.
- Nerve roots exit the spinal cord to both sides of the body.
- The spinal cord carries signals back and forth between the brain and the peripheral nerves.
- Cerebrospinal fluid surrounds the brain and the spinal cord and also circulates within the cavities of the central nervous system.
- The leptomeninges surround the brain and the spinal cord.
- The cerebrospinal fluid circulates between 2 meningeal layers called the
- pia matter and
- the arachnoid
Divisions Of The Nervous System
There are over 100 trillion neural connections in the average human brain, all in constant communication via synapses.
These synapses only take a fraction of a millisecond to transmit a given electrical impulse through the spinal cord its estimated to go at a speed of 268 mph!
The way these synapses are arranged and connected depends on the exact sub-system they fall under.
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How Then Does The Brain Repair Itself
Learning about the limitations of neurons compared to skin cells, you may be disappointed that an organ as important as the brain seems to be unprepared for damaging events. The truth is, the central nervous system has an ingenious strategy to repair itself that is entirely different from the strategy used by other organs. The brain will never be the same as before the damage, but it will try to compensate for its losses. Neurons in the brain are able to change their connections with each other. This process is called plasticity, and it helps the brain to adapt to the loss of neurons. Forget for a moment about dying cells, the responsibility for plasticity lies entirely with the surviving cells. How does this work?
- Figure 3
- In response to an injury, a brain cell can adapt by growing new arms and also by increasing or decreasing the strength of existing connections .
Lobes Of The Brain And What They Control
Each brain hemisphere has four sections, called lobes: frontal, parietal, temporal and occipital. Each lobe controls specific functions.
- Frontal lobe. The largest lobe of the brain, located in the front of the head, the frontal lobe is involved in personality characteristics, decision-making and movement. Recognition of smell usually involves parts of the frontal lobe. The frontal lobe contains Brocas area, which is associated with speech ability.
- Parietal lobe. The middle part of the brain, the parietal lobe helps a person identify objects and understand spatial relationships . The parietal lobe is also involved in interpreting pain and touch in the body. The parietal lobe houses Wernickes area, which helps the brain understand spoken language.
- Occipital lobe. The occipital lobe is the back part of the brain that is involved with vision.
- Temporal lobe. The sides of the brain, temporal lobes are involved in short-term memory, speech, musical rhythm and some degree of smell recognition.
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Other Cool Facts About The Brain
- The brain can’t multitask, according to the Dent Neurologic Institute. Instead, it switches between tasks, which increases errors and makes things take longer.
- The human brain triples in size during the first year of life and reaches full maturity at about age 25.
- Humans use all of the brain all of the time, not just 10% of it.
- The brain is 60% fat, according to Northwestern Medicine.
- The human brain can generate 23 watts of electrical power enough to fuel a small lightbulb.
Anatomy Of The Human Brain
The largest part of the human brain is the cerebrum, which is divided into two hemispheres, according to the Mayfield Clinic. Each hemisphere consists of four lobes: the frontal, parietal, temporal and occipital. The rippled surface of the cerebrum is called the cortex. Underneath the cerebrum lies the brainstem, and behind that sits the cerebellum.
The frontal lobe is important for cognitive functions, such as thought and planning ahead, and for the control of voluntary movement. The temporal lobe generates memories and emotions. The parietal lobe integrates input from different senses and is important for spatial orientation and navigation. Visual processing takes place in the occipital lobe, near the back of the skull.
The brainstem connects to the spinal cord and consists of the medulla oblongata, pons and midbrain. The primary functions of the brainstem include relaying information between the brain and the body supplying most of the cranial nerves to the face and head and performing critical functions in controlling the heart, breathing and levels of consciousness .
The cerebellum lies beneath the cerebrum and has important functions in motor control. It plays a role in coordination and balance and may also have some cognitive functions.
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Brain Stem Keeps You Breathing And More
Another brain part that’s small but mighty is the brain stem. The brain stem sits beneath the cerebrum and in front of the cerebellum. It connects the rest of the brain to the spinal cord, which runs down your neck and back. The brain stem is in charge of all the functions your body needs to stay alive, like breathing air, digesting food, and circulating blood.
Part of the brain stem’s job is to control your involuntary muscles the ones that work automatically, without you even thinking about it. There are involuntary muscles in the heart and stomach, and it’s the brain stem that tells your heart to pump more blood when you’re biking or your stomach to start digesting your lunch. The brain stem also sorts through the millions of messages that the brain and the rest of the body send back and forth. Whew! It’s a big job being the brain’s secretary!
The Central Nervous System In Your Body
Claudia Chaves, MD, is board-certified in cerebrovascular disease and neurology with a subspecialty certification in vascular neurology.
The central nervous system is comprised of the brain and spinal cord. The CNS receives sensory information from the nervous system and controls the body’s responses. The CNS is differentiated from the peripheral nervous system, which involves all of the nerves outside of the brain and spinal cord that carry messages to the CNS.
The central nervous system plays a primary role in receiving information from various areas of the body and then coordinating this activity to produce the body’s responses.
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What Is The Gray Matter And White Matter
Gray and white matter are two different regions of the central nervous system. In the brain, gray matter refers to the darker, outer portion, while white matter describes the lighter, inner section underneath. In the spinal cord, this order is reversed: The white matter is on the outside, and the gray matter sits within.
Gray matter is primarily composed of neuron somas , and white matter is mostly made of axons wrapped in myelin . The different composition of neuron parts is why the two appear as separate shades on certain scans.
Each region serves a different role. Gray matter is primarily responsible for processing and interpreting information, while white matter transmits that information to other parts of the nervous system.
Structure And Function Of The Spine
The spine is made up of 26 bones divided into 5 sections. These bones surround and protect the spinal cord. This includes 24 vertebrae , the sacrum and the coccyx.
Cervical region These are 7 vertebrae at the top of the spine that run from the base of the skull to the lowest part of the neck.
Thoracic region These are 12 vertebrae that run from the shoulders to the middle of the back.
Lumbar region These are 5 vertebrae that run from the middle of the back to the hips.
Sacrum This is a large section of fused vertebrae at the base of the spine.
Coccyx This is a small, thin section of fused vertebrae at the end of the spine.
Between the vertebrae are the discs .
Disc A layer of cartilage found between the vertebrae. Discs cushion and protect the vertebrae and spinal cord.
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Studies Of Desire And Reward
As previously discussed, different reward regions and pathways are activated when experiencing a pleasurable stimulus. Researchers have since expanded on this research to look into whether the stimulus needs to actually be experienced for these reward centers to be activated, or whether the anticipation of a reward triggers these areas.
Spreckelmeyer et al., used functional magnetic resonance imaging to investigate whether the anticipation of a monetary reward has a significant effect on the brain.
They found that through the fMRI data, there was activation of the neural structures relating to the reward system when anticipating a reward. It has also been found that the bigger the potential reward , the greater the brain activity in the reward areas.
These findings provide us with a better understanding of how reward systems work in the brain and that the brain areas can stimulate a reward response without experiencing a reward yet.
Sherman, Hernandez, Greenfield and Dapretto investigated the neural structures that are activated in terms of social media rewards. The âLikeâ option, which is prevalent on many social media platforms, is believed to give social rewards to those who receive them.
The researchers found this to be the case when the participants completed a task in an MRI scanner. This task was designed to mimic the social photo-sharing app Instagram.
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Nerve Cells Do Not Renew Themselves
Your skin cells keep dividing, they die and give birth to new cells all the time, even when youre not injured. After an injury, the skin makes a bunch of new cells and uses them to heal your wound. Yet, nerve cells in your brain, also called neurons, do not renew themselves. They do not divide at all. There are very few exceptions to this rule only two special places in the brain can give birth to new neurons. For the most part though, the brain cannot replenish dead neurons. This is especially worrisome because neurons are very sensitive cells and they die for all sorts of reasons. When you bump your head and suffer a concussion, neurons die. When there is a glitch in the blood supply to the brain, also called a stroke, neurons die. Neurons also die when faced with changes in their own functions, which happens in the so-called neurodegenerative diseases like Parkinsons disease and Alzheimers disease.
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Diagnosing Nervous System Conditions
There are a number of tests and procedures to diagnose conditions involving the nervous system. In addition to the traditional X-ray, a specialized X-ray called a fluoroscopy examines the body in motion, such as blood flowing through arteries, according to the NIH.
Other standard neurological exams include an MRI , CT scan, and an electroencephalogram , which records the brain’s continuous electrical activity. Positron emission tomography is a procedure that measures cell or tissue metabolism and brain activity to detect tumors or diseased tissue or tumors, the NIH noted.
A spinal tap places a needle into the spinal canal to drain a small amount of cerebral spinal fluid that is tested for infection or other abnormalities, according to the NIH.
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The Central Nervous System
The higher functions of the nervous system also referred to as the executive functions, are controlled by the brain. These include:
Cognition: thinking, learning, memory, language, insight, creating and planning goals. Cognition is primarily controlled in the frontal lobe and sets humans apart from all species on earth in its evolutionary development.
Emotions: controlled from many different structures, emotions can influence where in the brain memories are stored and the way theyre recalled. Emotions are controlled from many different organ systems as well, the CNS being only one. The hippocampus and amygdala are two of the nervous system structures involved in the regulation of emotions.
Consciousness: largely focused in the cerebellum, consciousness is a cognitive skill that is still very poorly understood by scientists, but central in what separates humans from many species.
The Cell Structure Of The Brain
The brain is made up of two types of cells: neurons and glial cells, also known as neuroglia or glia. The neuron is responsible for sending and receiving nerve impulses or signals. Glial cells are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin and facilitate signal transmission in the nervous system. In the human brain, glial cells outnumber neurons by about 50 to one. Glial cells are the most common cells found in primary brain tumors.
When a person is diagnosed with a brain tumor, a biopsy may be done, in which tissue is removed from the tumor for identification purposes by a pathologist. Pathologists identify the type of cells that are present in this brain tissue, and brain tumors are named based on this association. The type of brain tumor and cells involved impact patient prognosis and treatment.
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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.