Anatomy/Nervous System

The nervous system is a focus topic of the event Anatomy. It comes into rotation for the 2013 season. The nervous system consists of your brain and all the nerves throughout your body. It is responsible for regulating the body's response to external and internal stimuli. It can be divided into the central and peripheral nervous systems. The central nervous system or CNS includes the brain, cranial nerves, and the spinal cord; the peripheral nervous system or PNS, includes all nerves outside of the spinal region.


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Brain and Sense Organs
There are a wide variety and a vast number of parts in the Nervous System, but the major regions are the brain, nerves, and spinal cord, all of which contribute to the great capabilities of the human body.

The Brain
Your brain is arguably the most important organ in your body. It controls all actions, stores memory, and processes the 5 senses. It has many important parts, each with a unique and vital role.



The brain is divided into four main lobes: the frontal lobe, the parietal lobe, the occipital lobe, and the temporal lobe. Each has a specific function.

Frontal Lobe
The frontal lobe is responsible for conscious thought; damage to it can result in severe personality changes. It is positioned anterior to the central sulcus. It is generally responsible for recognizing future consequences resulting from current actions, choosing between good and bad actions (or better and best), overriding and suppressing socially unacceptable responses, and determining similarities and differences between things or events. In the posterior portion of the frontal lobe lies the precentral gyrus which is also known as the somatomotor or primary motor cortex. This is where voluntary motions are processed. The motor homunculus (little person) represents the portions of the body which the motor cortex controls. The foot lies inside the medial longitudinal fissure,the leg lies up against the medial longitudinal fissure, and traveling outward from there follow the arm and the head. While this cortex does control other regions of the body, there aren't enough controls in those regions to warrant a position in the homunculus. Different hemispheres of the brain control the body contralaterally.

In humans, the frontal lobe generally reaches maturity around 20 years old. This explains why, in most societies, people are considered to be an adult around this age.

Parietal Lobe
The parietal lobe is associated with spatial processing and navigation abilities. It is positioned posterior to the central sulcus and thereby the frontal lobe, anterior and superior of the parieto-occipital sulcus and superior of the lateral sulcus or sylvian fissure. It gets its name from the bone that lies above it, the parietal bone. In the anterior portion of the parietal lobe lies the somatosensory or primary sensory cortex which has nearly the same organization as the somatomotor cortex, just with more concentration in the genitalia and breasts.

Occipital Lobe
The occipital lobe is the section in which your brain processes visual images that come from your eyes. It is positioned in the back of the head, which gets it its name, since in Latin, 'oc' means back and 'caput' means head. It is positioned posterior and inferior of the parieto-occipital sulcus.

Temporal Lobe
The temporal lobe is responsible for visual memory/object recognition, processing sound and smell, and understanding language. It is located inferior to the lateral sulcus or sylvian fissure, and is positioned between the frontal and occipital lobe.

Other Divisions of the Brain

 * The Cerebrum- The Cerebrum controls perception, imagination, thought, judgement, and decision. The Cerebrum basically consists of the outer surface of the brain. It is further divided into lobes, such as the occipital lobe (processes vision) and the frontal lobe (processes voluntary movement and planning). | General Psychology: Cerebrum


 * The Cerebellum- The Cerebellum is located under the Cerebrum, at the back of the brain. It controls balance, movement, and coordination. It is also involved in attention and language. | Neuroskills


 * The Brain Stem- The Brain Stem is located under the Cerebrum, and in front of the Cerebellum. It mainly controls involuntary functions such as respiration, digestion, circulation, and moving involuntary muscles such as the heart. Basal ganglia connected to the brain stem function as switching centers. | Brain Stem


 * The Pituitary Gland- The Pituitary gland is responsible for controlling the release of hormones throughout the body. It is important in growth especially puberty. It can also be considered part of the Endocrine System. | U of Maryland Med. School


 * The Hypothalamus- The Hypothalamus's most important function is to regulates your body's temperature using thermoreceptors and osmoreceptors. This is called homeostasis. If your body is too hot, the hypothalamus makes you sweat to lower your temperature. If your body is too cold, the hypothalamus makes you shiver to increase your body temperature. | Biology: Hypothalamus


 * The Limbic System- The Limbic System is located in the middle of the brain. It consists of structures such as the hippocampus (processes short term memory into long term memory). It is important for memory, learning, and emotion. | UCSD: Limbic System


 * Cerebrospinal Fluid - cerebrospinal fluid is a colorless fluid that flows through the brain and spinal cord. It acts as a barrier to prevent wastes from damaging the brain and to maintain homeostatic conditions. When there is too much cerebrospinal fluid, hydrocephalus (or hydrocephaly) results, causing swelling in the head. This can be reversed to an extent by tubes draining the excess fluid.

The Nerves
The nerves are the body's messengers. The send the brain's messages and commands to the corresponding parts of the body. The spinal cord is the long bundle of nerves running through the back of your body. It connects with the brain, and all the other nerves. The spinal cord is supported by your backbone. The nerves are made of cells called neurons bound together in bundles called fascicles, nerves, peduncles, or tracts and surrounded by the endoneurium, perineurium, and epineurium membranes. Neurons connect with each other to communicate. Electrochemical waves travel along the axon of one neuron, then move across a gap called a synapse. Sodium and potassium ions are pumped across the synapse to the dendrite of another neuron in a nerve impulse.



CNS

 * astrocyte - named so because it resembles a star. These are the support cells of the CNS, they help form the blood-brain barrier, supply nutrients to neurons, and help regulate the extra cellular chemical environment most notably, removing potassium ions, in order to keep the concentration gradient. These are the most numerous of th CNS glial cells.
 * oligodendrocyte - these are similar to Schwann cells, but in the CNS. Like Schwann cells, they provide myelination to axons. However, they are able to myelinate many axons around they instead of just one.
 * microglia-these are the macrophages of the CNS. They protect the neurons from bacteria and viruses through phagocytosis. These are the least numerous of the CNS glial cells.
 * ependymal cells - also called ependymocytes. These line the walls of the ventricular and produce cerebrospinal fluid. They also have cilia that they beat in order to move CSF. Also, they make up the blood CSF barrier. Lastly, they also are believed to be neuronal stem cells.

PNS

 * schwann cells-these cells myelinate PNS axons. All cells-even the unmyelinated ones- in the PNS are surrounded by schwann cells. When myelinating, Schwann cells can only surround 1 axon, however, they can surround many unmyelinated axons at once. They also undergo a small amount of phagocytotic activity and they clear debris.
 * satellite cells-these cells are similar to astrocytes in that they regulate the extracellular chemical environment. They are different in that that is their only main job.

Spinal Cord
Along with the brain, the spinal cord makes up the central nervous system. It is divided into 31 pairs of nerves, making 62 nerves composed of sensory and motor neurons. The nerves are named off of where they leave the spine. They are divided into 5 groups, cranial, thoraic, lumbar, sacral, and coccygeal. The spinal cord itself in an adult usually ends around the L1 or L2 vertebra, while the remaining axons, formin the cauda equina, continue headin down through the spine and exit where they are supposed to. This happens because the spinal cord stops growing at 4 years of age, while the spine continues to grow. The spinal cord contains both white and gray matter. The white matter travels in tracts to and from the brain. The gray matter forms a sort of h, with 3 horns on either side of the spinal cord. The ventral horn contains somatic motor nuclei, the lateral horn contains autonomic motor nuclei. The dorsal horn is divided, with the farthest back being the somatic sensory portion and the other portion being the visceral sensory portion.
 * 8 in the cervical region
 * 12 in the thoracic region
 * 5 in the lumbar
 * 5 in the sacral
 * 1 in the coccygeal.

Encephalography
A neural examination/radiography in which a small amount of cerebrospinal fluid is replaced with a gas.

Magnetic Resonance Imaging (MRI)
A scan of the brain which uses magnets to show images of the body with sharp contrast of soft tissue, air, and bone. This has advantages because it doesn't use radiation.

Neural Impulses
Ionic basis of the cellular membrane potential When a neuron is not sending a signal, the inside of the neuron is negative relative to the outside. Although the concentrations of the different ions attempt to balance out on both sides of the membrane, they cannot because the cell membrane allows only some ions to pass through channels (ion channels). At rest, potassium ions (K+) can cross through the membrane easily. Also at rest, chloride ions (Cl-) and sodium ions (Na+) have a more difficult time crossing. The negatively charged protein molecules (A-) inside the neuron cannot cross the membrane. The sodium- potassium pump removes 3 sodium ions for every 2 potassium ions it lets in. When all forces balance out, and the difference in the voltage between the inside and outside of the neuron is measured. That is the resting potential. The resting membrane potential of a neuron is about -70 mV. At rest, there are more sodium ions outside the neuron and more potassium ions inside that neuron. Action Potential: Generation and Propagation

An action potential (spike/ impulse) occurs when a neuron sends information down an axon, away from the cell body. 1. Generation- A stimulus causes the resting potential to move toward 0 mV. When the depolarization reaches about -55 mV a neuron will fire an action potential. If the neuron does not reach this critical threshold level, then no action potential will fire. "ALL OR NONE" principle- The neuron either does not reach the threshold or a full action potential is fired. All sizes of action potentials are the same. Action potentials are caused when different ions cross the neuron membrane. A stimulus first causes sodium channels to open. Because of the concentration gradient, and the inside of the neuron is negative relative to the outside, sodium ions rush into the neuron. Sodium has a positive charge, so the neuron becomes more positive and becomes depolarized. It takes longer for potassium channels to open. When they do open, potassium rushes out of the cell, reversing the depolarization. Sodium channels start to close. This causes the action potential to go back toward -70 mV (a repolarization). The action potential actually goes past -70 mV (a hyperpolarization) because the potassium channels stay open a bit too long. Gradually, the ion concentrations go back to resting levels and the cell returns to -70 mV. 2. Propagation- action potentials are carried from the axon of one neuron to the dendrite of another neuron by synapses and neurotransmitters. Positively charged ions in the fluid outside of the cell flood into the cell and the charge on the inside changes from negative to positive. The electrical impulse moves down the axon.

Impulses From Axon to Dendrite Synapses- junctions where neurons pass signals to other neurons, muscle cells, or gland cells. When a charge reaches a synapse, it may trigger release of tiny bursts of chemicals called neurotransmitters. The synapse contains a small gap separating neurons. The synapse consists of: 1.a presynaptic ending that contains neurotransmitters, mitochondria and other cell organelles 2.a postsynaptic ending that contains receptor sites for neurotransmitters 3.a synaptic cleft or space between the presynaptic and postsynaptic endings. Neurotransmitters- used to restart impulse in the dendrite of the second neuron. They are chemicals in junctions.

For communication between neurons to occur, an electrical impulse must travel down an axon to the synaptic terminal. At the synaptic terminal, an electrical impulse will trigger the migration of vesicles containing neurotransmitters toward the presynaptic membrane. The vesicle membrane will fuse with the presynaptic membrane releasing the neurotransmitters into the synaptic cleft. The neurotransmitter molecules diffuse across the synaptic cleft where they can bind with receptor sites on the postsynaptic ending to influence the electrical response in the postsynaptic neuron. When a neurotransmitter binds to a receptor on the postsynaptic side of the synapse, it changes the postsynaptic cell's excitability: it makes the postsynaptic cell either more or less likely to fire an action potential. If the number of excitatory postsynaptic events is large enough, they will add to cause an action potential in the postsynaptic cell and a continuation of the "message." Excess neurotransmitters are broken down by enzymes. If they are not, paralysis will occur. One example of a neurotransmitter is acetylcholine. The enzyme that breaks it down is acetylcholinesterase.

Central Nervous System
Consists of the Brain and Spinal Cord.

Peripheral Nervous System
Nerves and ganglia not including the CNS (see above) Split into afferent and efferent nervous systems The efferent nervous system is split into the autonomic and somatic nervous systems. The autonomic nervous system is split into the sympathetic and parasympathetic nervous systems.
 * afferent-sensory
 * efferent-motor.
 * autonomic-controlled by the subconscious. Happens "auto"matically. Can control all types of muscle
 * somatic-controlled by the conscious brain. Always effects skeletal muscle.
 * sympathetic-"fight or flight" response. Responds in times of stress.
 * parasympathetic-controls the body in times of rest.

Epilepsy
Epilepsy can be described as a "seizure disorder," or a disorder that causes a person to have unprovoked or unexpected seizures. THese seizures can seem to have absolutely no cause whatsoever, and after two of these "unprovoked seizures" a person is considered to have epilepsy. Epilepsy can have a varying amount of mental and physical incapacitations, all depending on the person and the severity of the seizures caused by it. | Epilepsy Foundation

Seizures
Caused by a period of disturbed electrochemical activity in the brain during which the body ususally spasms.

Alzheimer's Disease
A progressive, degenerative disorder that attacks the neurons, resulting in loss of memory, thinking and language skills, and changes in behavior.The most common form of dementia, it affects memory and comprehension. Most often occurs in people over 65.

Multiple Sclerosis (MS)
A chronic, often disabling disease that attacks the Central Nervous System (CNS). Myelin (fatty substances that surrounds and protects the nerve fibers) is damaged, as well as the nerve fibers themselves. The damaged myelin forms scar tissue (sclerosis), which gives the disease its name. When any part of the myelin sheath or nerve fiber is damaged or destroyed, nerve impulses traveling to and from the brain and spinal cord are distorted or interrupted, producing the variety of symptoms that can occur. Symptoms may be mild, such as numbness in the limbs, or severe, such as paralysis or loss of vision.Considered as an autoimmune disease,

Parkinson's Disease
A chronic and progressive movement disorder which involves malfunction and death of neurons. Some of the neurons create dopamine (chemical that sends messages to brain that controls movement and coordination). As Parkinson's Disease progresses, the neurons die, therefore the amount of dopamine decreases. Primary motor signs include: tremors, bradykinesia (slowness of movement), rigidity, and postural instability (impaired balance and coordination)

Shingles (Herpes Zoster)
Caused by varicella (same virus that causes chickenpox), it mostly occurs in a band or strip on one side of the body called a dermatome, the area where one of the nerves from your spinal cord connects with the skin.

Cerebral Palsy
A disorder that affects muscle tone, movement, and motor skills; usually caused by prenatal brain damage or during first 3-5 years of a child’s life. The brain damage may lead to other health issues including vision, hearing, speech problems, and learning disabilities.

There are three types: spastic cerebral palsy– stiffness and movement difficulties, athetoid cerebral palsy– involuntary and uncontrolled movements, ataxic crebral palsy– disturbed sense of balance and depth perception

Glaucoma
Glaucoma is a group of diseases that can damage the eye's optic nerve and result in vision loss and blindness. While glaucoma can strike anyone, the risk is much greater for people over 60. The most common type of glaucoma is called open-angle glaucoma. In the normal eye, the clear fluid leaves the anterior chamber at the open angle where the cornea and iris meet. When fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye.

Sometimes, when the fluid reaches the angle, it passes too slowly through the meshwork drain, causing the pressure inside the eye to build. If the pressure damages the optic nerve, open-angle glaucoma -- and vision loss -- may result.

Pink Eye (Conjunctivitis)
Pink eye (conjunctivitis) is an inflammation or infection of the transparent membrane (conjunctiva) that lines your eyelid and covers the white part of your eyeball. When small blood vessels in the conjunctiva become inflamed, they're more visible. This is what causes the whites of your eyes to appear reddish or pink.

Pink eye is commonly caused by a bacterial or viral infection, an allergic reaction, or — in babies — an incompletely opened tear duct.

Alcohol
Alcohol is a central nervous system depressant. It acts at many sites, including the reticular formation, spinal cord, cerebellum and cerebral cortex, and on many neurotransmitter systems. Alcohol is a very small molecule and is soluble in "lipid" and water solutions. Because of these properties, alcohol gets into the bloodstream very easily and also crosses the blood brain barrier. In low doses, alcohol: produces a relaxing effect, reduces tension, lowers inhibitions, impairs concentration, slows reflexes, impairs reaction time, and reduces coordination.

In medium doses, alcohol: slurs speech, causes drowsiness, and alters emotions.

In high doses, alcohol: induces vomiting, creates breathing difficulties, unconsciousness, and comas.

Caffeine
Caffeine is a alkaloid which acts as a stimulant drug. In humans, it temporarily stimulates the central nervous system, increasing alertness and attention. However, it can cause addiction. If one takes in too much caffeine, they can develop a buildup, called tolerance, in which the caffeine's effects are reduced, and therefore more is needed to create the same effects as when there was less tolerance.

Nicotine
Nicotine (also spelled nicotene) is a alkaloid which constitutes about 0.6-3% of tobacco plants. As well as being a chemical, which, when contained in plants, resists animal consumption, it is also a stimulant for mammals. About 1 milligram is contained in the average cigarette, and it is responsible for the addiction to smoking. When nicotine enters the body, it quickly enters the bloodstream. When it binds to receptors in the central nervous system, they "turn up the volume" on neurotransmitters.

Marijuana
Marijuana comes from a plant called "cannabis sativa"; the chemical in the plant that produces the altered states of consciousness is called "delta-9 tetrahydrocannabinol" or "THC". THC acts on cannabinoid receptors, which are found on neurons in many places in the brain. These areas are involved in memory (hippocampus), concentration (cerebral cortex), perception (sensory portions of the cerebral cortex), and movement (cerebellum, substantia nigra, globus pallidus).

In low-medium doses, marijuana: causes relaxation, reduces coordination, reduces blood pressure, induces sleepiness, disrupts attention, and creates an altered sense of time and space.

In high doses, marijuana – induces hallucinations, creates delusions, impairs memory, and provokes disorientation.

Links

 * http://yucky.discovery.com/flash/body/pg000136.html


 * http://kidshealth.org/kid/htbw/brain.html


 * http://www.albany.edu/faculty/cafrye/apsy601/Ch.02cellsofthenervoussystem.html

Official Information 2013
These are all safe, downloadable files from http://www.soinc.org.

Official Training Handout 2013
http://www.soinc.org/sites/default/files/ANATOMY_HANDOUT_2013.doc

Official Training PowerPoint 2014
http://www.soinc.org/sites/default/files/uploaded_files/A%26P-2014.ppt