Download Nerve Flash Cards

What are the three Parts of the Nervous System?
Central Nervous System (CNS): brain and spinal cord.
1. Peripheral Nervous System (PNS): nerves of the body
2. Autonomic Nervous System (ANS): has parts of the CNS and
PNS. Controls autonomic function (blood pressure, digestion, etc).
a. Sympathetic division
b. Parasympathetic division
Which system is made up of more cell than any other system?
Nervous System
About how many cells does the brain have?
A trillion cells
What is the main and most important cell type of the nervous system?
Neuron
What are three things that all neurons do?
1. Receive a signal. Can be any type of stimulus (change in
environment, signal from another neuron, etc).
2. Transmit a signal to another location. E.g. finger touching
something  signal to spinal cord or brain.
3. Stimulate another cell
a. Another neuron  transmit signal
b. Muscle  contraction
c. Gland  secretion
What are some other special characteristics of neurons?
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Longevity – can live and function for a lifetime
Do not divide – fetal neurons lose their ability to undergo
mitosis; neural stem cells are an exception
High metabolic rate – require abundant oxygen and glucose
How many types of neurons exist?
There are hundreds of different types of neurons.
What is the function of each type of neuron?
Each one is specialized for a particular task (e.g. sensory nerves receive
and transmit sensory information, and there are several different types of
them, with receptors for touch, light, smell, etc). Motor neurons transmit
signals for muscle contraction, etc.
What characteristics do all neurons share?
They all share certain characteristics. They have longevity (can last a
lifetime), they have a high metabolic rate, they cannot divide to reproduce,
and they cannot survive without oxygen.
Neuron
Describe the function of DENDRITES?
They function to receive the signal and carry the nerve conduction toward
the cell body.
What is the CELL BODY?
It’s where the nucleus, ribosomes, and most organelles are located
Describe the function of an AXON?
The function of an axon is to transmit signals. Some cells have many
axons, some have one, some are short, and some are long.
Describe the function of SYNAPTIC KNOBS?
They function to stimulate another cell. Neurons may have a couple of
synapses, or hundreds.
Axon of presynaptic neuron  SYNAPTIC CLEFT  dendrite of post synaptic
neuron
How does the signal go through the space?
By a chemical transmission. The synaptic knob has vesicles filled with a
neurotransmitter that carries the signal. Each type of neuron used
particular types of neurotransmitters, so there are 100’s of types.
What is a type of cell in the nervous system other than neurons, that are
supporting cells of the nervous system? Most tumors of the brain
originate from these cells.
GLIA (neuroglia)
These are found in the CNS, and are very large and complex cells. They
form myelin sheaths.
OLIGODENDROCYTES (“few branches”)
This sheath is a covering around an axon to speed up the nerve
conduction.
MYELIN SHEATHS
Describe myelin sheaths.
A sheet of paper is like one of these cells, and it wraps itself around a pencil
(axon), so there are many layers. The myelin sheath is an electrical
insulator. BETWEEN the sheaths are nodes = NODES OF RANVIER;
these are BARE regions of axonal membranes only found in myelinated
axons.
What are the bare regions of axonal membranes only found in
myelinated axons?
NODES OF RANVIER
Describe the function of myelinated axons and Nodes of Ranvier.
The action potential jumps from one Node of Ranvier to the next Node
of Ranvier, speeding up the overall nerve conduction. Therefore, a
myelinated axon conducts impulses faster than an unmyelinated axon.
An unmyelinated axon can travel 1-20 meters per second. A myelinated
axon can travel 20-100 meters per second.
Why would you want any unmyelinated axons?
They are not necessary for things like digestion to start at 1/10 of a
second rather than one second, or start sweating in 1/20 of a second
rather than 1 second. Walking and thinking are things that need to be
quick.
An oligodendrocyte can wrap around one nerve cell in many locations,
and nerve cells can have many oligodendrocyes on their axons.
Describe MULTIPLE SCLEROSIS.
It is an autoimmune disease where the oligodendrocytes (the myelin
sheaths) are destroyed, interfering with the neuron functions in the CNS
and brain. It is the most common neurological disease of young adults.
Starts to manifest in late teens and early 20’s. It progresses to paralysis
and sometimes death. One in 1000 people get it. There are treatments,
but no cure.
Which type of cell is another cell that forms myelin sheaths, but in
the PNS? Each cell only forms one myelin sheath.
SCHWANN CELL
What is another very large, complex cell, in the CNS, whose
function is to wrap around capillaries while it also is physically
supporting and wrapping around neurons?
ASTROCYTE
Describe the function of astrocytes.
a. Physically supports the neurons
b. Transmits materials from capillaries to neurons
c. Forms blood-brain barrier (BBB)
Describe the blood brain barrier.
The BBB prevents a lot of certain types of materials from leaving the
blood and entering the brain (e.g. hormones, drugs). The brain still gets its
nourishment from the blood, without the toxins. The continuous capillaries
have leakage, but are surrounded by astrocytes, so not everything can leak
out. Certain antibiotics can’t cross the BBB, so they can’t be used for
brain infections. The only function of the blood-brain barrier is to help
protect the central nervous system.
What is the only function of the blood brain barrier?
To help protect the central nervous system.
These are not micro, nor are they glia. They are macrophages, the
same size as everywhere else in the body. They are called micro
because they are much smaller than real glia cells. They pick up
bacteria and dead cell, etc.
MICROGLIA (one word, two errors!).
What is the portion of the CNS that is unmyelinated (cell bodies of
neurons, glia, and dendrites)?
GREY MATTER
What is the portion of the CNS with myelin (axons)?
WHITE MATTER
What makes the white matter look white?
Myelin
A collection of axons in the PNS. No cell bodies, dendrites, or synapses;
just axons.
NERVE
A collection of axons in the CNS e.g. conveys information (axons) from
the left to the right side of the brain.
TRACT
Where information is processed. Most synapses are in the CNS.
SYNAPSES
A collection of cell bodies in the PNS.
GANGLION
A network of nerves (nerves don’t run by themselves, they go in groups).
NERVE PLEXUS
Nerves that leave the CNS to effect a muscle or gland.
MOTOR NEURON
This type of cell goes from body to CNS, carrying sensory information.
SENSORY NEURON
This is a small neuron found only in the CNS; it connects two other
neurons. There are a large number of interneurons in the CNS; this is
what makes the CNS complex.
INTERNEURON