Download Central Nervous System

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.
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.
This brain is split in half to reveal the Limbic System.
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.
A simple diagram of a neuron.
Types of Neuroglial Cells
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.
 8 in the cervical region
 12 in the thoracic region
 5 in the lumbar
 5 in the sacral
 1 in the 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.
A diagram of spinal cord horns and their purposes.
Neural Examinations
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
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


afferent-sensory
efferent-motor.
The efferent nervous system is split into the autonomic and somatic nervous systems.


autonomic-controlled by the subconscious. Happens
"auto"matically. Can control all types of muscle
somatic-controlled by the conscious brain. Always effects
skeletal muscle.
The autonomic nervous system is split into the sympathetic and parasympathetic nervous systems.

sympathetic-"fight or flight" response. Responds in times of
stress.
 parasympathetic-controls the body in times of rest.
A diagram of the breakdown of the Peripheral Nervous System.
Disorders/Diseases
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.
Effects of Drugs
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.