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 sympathetic nervous system consists of the brain, retina, and spinal cord; the parasympathetic, sensory neurons and the enteric nervous system (which controls the digestive system).


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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 at the anterior of the head. 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 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 behind the frontal lobe and above the occipital and temporal lobes. It gets its name from the bone that lies above it, the parietal bone.

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.

Temporal Lobe
The temporal lobe is responsible for visual memory/object recognition, processing sound and smell, and understanding language. It is located below the parietal lobe and is sandwiched 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 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. There are 8 in the cervical region, 12 in the thoracic region, 5 in the lumbar, and 5 in the sacral and 1 in the coccygeal. The spinal cord itself in an adult usually ends around the L1 or L2 vertebra, while the remaining axons form the cauda equina 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.

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

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
The most common form of dementia, affects memory and comprehension. Most often occurs in persons over 65

Multiple Sclerosis (MS)
An autoimmune disorder in which the myelin sheath is attacked.

Parkinson's Disease
Characterized by shaking (tremors), caused by a deficiency of L-Dopamine in the brain.

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 1mg 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.

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