Types of neurons

The nervous system consists of the central
nervous system (the brain and spinal cord), the
peripheral nervous system (the sensory and
motor neurons), and the autonomic nervous
system
. All nervous systems in all animal species have 
four basic types of functional cells:
 Sensory neurons

 Motor neurons

 Interneurons

 Computation neurons

 The nervous system has many types of sensory neurons. Nerve endings
on one end of each neuron are encased in a special structure to sense a
specific stimulus

 Chemoreceptor's sense chemicals.). Taste buds have chemoreceptor's to
detect chemicals dissolved in liquids. Chemoreceptor's in the brain also monitor the
concentration of carbon dioxide in the blood and cerebrospinal fluid to help control
your rate of breathing.
 Mechanoreceptors sense touch, pressure and distortion (stretch). Stretch
receptors in your muscle tendons are the first link in the knee-jerk reflex.
 Photoreceptors, which sense light, are found in the retinas of your eyes.
 Thermo receptors are free nerve endings that sense temperature, but we're
not sure exactly how they do this. Changes in temperature could affect the
movements of ions across the cell membrane and influence action potentials in that
way.
 Nociceptors are free nerve endings that sense pain. They respond to a variety
of stimuli (heat, pressure, chemicals) and sense tissue damage.
 Auditory receptors in the i006Ezner ear sense vibrations from sound
waves.

 A motor neuron is a type of cell in the nervous
system that directly or indirectly controls the
contraction or relaxation of muscles,
 Somatic motorneurons are directly involved in the
contraction of skeletal muscles and are typically
involved in locomotion.
 -Special visceral motorneurons are involved in the
motion of gills in fish and the motion of neck and
facial muscles in vertebrates.
 -General visceral motorneurons are directly involved
in the contractions of the heart, the muscles of the
arteries, and other viscera that are not consciously
controlled.

 inteneurons a neuron, or nerve cell, located entirely
within the central nervous system . The
central nervous system (CNS) consists of nerve
cells within the brain and spinal cord
 An interneuron acts as a “middle-man” between
afferent,neurons, which receive signals from the
peripheral nervous system, and efferent neurons,
which transmit signals from the brain. It also
connects to other interneurons, allowing them to
communicate with one another.
 CNS interneurons are typically inhibitory, and use
the neurotransmitter GABA or glycine. However,
excitatory interneurons using glutamate also exist,
as do interneurons
releasing neuromodulators like acetylcholine.

 The vast majority of neurons in vertebrates are
computation neurons. Computation neurons
extract and process information coming in from
the senses, compare that information to what’s
in memory, and use the information to plan
and execute behavior

 Unipolar cells have one primary process that give rise to
several branches. One of these is the axon and the rest serve
as dendritic receiving structures. Unipolar cells have no
dendrites arising directly from the cell's soma. These cells
occur in certain ganglia of the autonomic nervous system of
vertebrates

Bipolar cells have two processes emerging from the cell
soma: a peripheral process or dendrite, the axon, which
carries information toward the brain. These cells have
mainly sensory functions: retina, olfactory epithelium and
sensory cells of the spinal ganglia
 Multipolar neurons have a single axon and one or more
dendritic branches emerging from all parts of the cell body.
Multipolar cells vary in the number and length of their
dendrites and the length of their axons. The number and
extent of dendritic processes depend on the number of
synaptic contacts that other neurons make onto it.

 People with AD gradually suffer memory loss and a decline in
thinking abilitiesThese losses in cognitive function are accompanied
by changes in the brain, including the build-up of amyloid plaques
and tau-containing neurofibrillary tangles, which result in the death
of brain cells and the breakdown of the connections between them.

 Amyloid plaques and neurofibrillary tangles are the primary
hallmarks of Alzheimer's disease. Plaques are dense deposits of
protein and cellular material outside and around the brain's nerve
cells. Tangles are twisted fibers that build up inside the nerve cells.
Scientists have known about plaques and tangles since 1906, when a
German physician, Dr. Alois Alzheimer, first identified them in the
brain of woman who had died after suffering paranoid delusions
and psychosis. Intensive research efforts of the last two decades
have revealed much about their composition, how they form, and
their possible roles in the development of Alzheimer's disease. The
deposition of amyloid in the form of plaques is thought by many
scientists to trigger the cascade of events leading to Alzheimer's
pathology. The best evidence that amyloid causes the disease comes
from the genetic studies in which mutations of APP, PS1, PS2 and
APOE e4 (the genes so far identified as causing some cases of
Alzheimer's) all facilitate amyloid accumulation

 Are older. However, developing AD is not a part of normal aging.
 Have a close blood relative, such as a brother, sister, or parent with AD.
 Have certain genes linked to AD, such as APOE epsilon4 allele
 The following may also increase your risk, although this is not well
proven:
 Being female
 Having high blood pressure for a long time
 History of head trauma
 There are two types of AD:
 Early onset AD: Symptoms appear before age 60. This type is much less
common than late onset. However, it tends to get worse quickly. Early
onset disease can run in families. Several genes have been identified.
 Late onset AD: This is the most common type. It occurs in people age 60
and older. It may run in some families, but the role of genes is less clear.
 The cause of AD is not clear. Your genes and environmental factors seem
to play a role. Aluminum, lead, and mercury in the brain is no longer
believed to be a cause of AD.

 The early symptoms of AD can include:
 Difficulty performing tasks that take some
thought, but used to come easily, such as balancing
a checkbook, playing complex games (such as
bridge), and learning new information or routines
 Getting lost on familiar routes
 Language problems, such as trouble finding the
name of familiar objects
 Losing interest in things previously enjoyed, flat
mood
 Misplacing items
 Personality changes and loss of social skills

 As the AD becomes worse, symptoms are more obvious and
interfere with your ability to take care of yourself. Symptoms can
include:
 Change in sleep patterns, often waking up at night
 Delusions, depression
 Difficulty doing basic tasks, such as preparing meals, choosing
proper clothing, and driving
 Difficulty reading or writing
 Forgetting events in your own life history, losing awareness of who
you are
 Hallucinations, arguments, striking out, and violent behavior
 Poor judgment and loss of ability to recognize danger
 Using the wrong word, mispronouncing words, speaking in
confusing sentences
 Withdrawing from social contact
 People with severe AD can no longer:
 Understand language
 Recognize family members
 Perform basic activities of daily living, such as eating, dressing, and
bathing

 here is no cure for AD. The goals of treatment are:
 Slow the progression of the disease (although this is
difficult to do)
 Manage symptoms, such as behavior problems,
confusion, and sleep problems
 DRUG TREATMENT
 Medicines for AD include:
 Donepezil (Aricept), rivastigmine (Exelon), and
galantamine
 , Some people believe certain vitamins and herbs
may help prevent or slowdown AD
 There is no strong evidence that Folate (vitamin
B6), vitamin B12, and vitamin E prevent AD or slows
the disease once it occurs.

By farah adulkadir
Mira mohamed
Nablia adam
Yasmeen abdelhameed

Types of neurons

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