1. The document summarizes key aspects of the nervous system, including its organization into the central nervous system (CNS) and peripheral nervous system (PNS). 2. It describes the generation and conduction of nerve impulses, known as action potentials, and how they are triggered by the opening and closing of ion channels in the neuron's membrane. 3. Synapses, the junctions between neurons, are explained as the sites of neurotransmitter release that allow signals to be transmitted from one neuron to the next.

1. ANATOMY &
PHYSIOLOGY
WEEKLY
Anatomy and
Physiology Weekly
Volume 1, Issue 1 (Informational Section) 10.17.2012
Inside this issue:
Organization of the Nervous System!!
Organization of 1 The nervous system is a com- CNS to the rest of the body,
the Nervous plex system that is mainly divid- send motor information to ef-
System ed into two sections the Cen- fectors. Somatic motor volun-
tral Nervous System (CNS) tary nervous system: innervates
which is the brain and spinal skeletal muscle
cord and the Peripheral Nerv-
Nerve Impulses 1 Autonomic motor involun-
ous System (PNS) which con-
Part 1 tary nervous system innervates
sists of the cranial nerves (1). cardiac muscle, smooth muscle,
The nervous system glands .
can be broken down into other
Nerve Impulses 2 divisions and sub divisions. Sen-
Part 2 sory (afferent) division transmits
information from periphery to
CNS, contains receptors.
The Synapse 2
Somatic receives sensory
information from skin, fascia,
joints, skeletal, muscles, special Picture is © (3)
senses. Visceral receives senso- Get ready to learn all about
Cells of the 3
ry information from viscera. the nervous system in this
Nervous System Motor (efferent) division trans- new issue of Anatomy and
mits information from body Physiology Weekly!
Reflex Arc 4
Nerve Impulses Part 1
Membrane potential is acid chains snake back and potential exits only across the
when a neuron is adequately forth across the membrane.
stimulated , an electrical im- Some channels , leakage or no membrane. (2)
pulse is generated and conduct- leakage channels , are always
ed along the length of its axon. open. Channels include :
This is response , called the Chemically gate, Ligand-gated,
action potential or nerve im- Voltage-gated, and Mechani-
pulse , is always the same re- cally gated . (2)
gardless of the source or type
There is also Resting
of stimulus , and it underlies
Membrane Potential, which is
virtually all functional activities
The potential difference in a
of the nervous system. (2) resting neuron and the mem-
brane is said to be polarized.
The value of the resting mem-
Membrane channels brane potential varies from -
are large proteins , often with 40mV to -90mV in different
several subunits , whose amino types of neurons. The resting
1

2. Page 2 Anatomy and Physiology Weekly
Nerve Impulses Part 2 Written by —Colton
Membrane Potential: difference in electrical
charge across their plasma membranes. 3. As more Na+ enters the cell through
Resting Membrane Potential: the mem- voltage-gated Na+ channels, the membrane
brane potential maintained by a noncon- depolarized even further.
ducting neuron’s plasma membrane. 4. The magnitude of the action potential
Local Potential: A slight shift away from the peaks (at +30 mV) when voltage-gated Na+
RMP in a specific region of the plasma mem- channels close.
brane. 5. Repolarization begins when voltage-gated
© (4) Action Potential: is, as the term suggests, K+ channels open, allowing outward diffu-
the membrane potential of an active neu- sion of K+.
rons, that is, one that is conducting an im-
6. After a brief period of Hyperpolarization,
pulse. An example of this is shown below. the resting potential is restored by the sodi-
1. A stimulus triggers stimulus-gated Na+ um-potassium pump and the return of ion
channels to open and allow inward Na+ channels to their resting state.
diffusion. This causes the membrane to de-
polarize.
2. As the threshold potential is reached,
voltage-gated Na+ channel open.
The Synapse
Synapse: Functional membrane to mem- Neurotransmitters: chemicals that allow
brane contacts of a nerve cell with an- the transmission of signals from one
© (5) other nerve cell, muscle cell, gland, cell neuron to the next across synapses.
or sensory receptor; functions in the They are found at the axon endings of
transmission of action potenitals from motor neurons, where they stimulate
one cell to another. the muscle fibers. They and their close
relatives are produced by some glands
“Summation is a Summation: Phenomena in which the
such as the pituitary and the adrenal
phenomena in
degree of changing in membrane poten-
tial directly correlates with stimulation glands . (1)
which… degree of
frequently.
changing membrane
potential directly
correlates with
stimulation”
2

3. Volume 1, Issue 1 (Informational Section) Page 3
Cells of the Nervous System
The nervous system is Non-neural cells are also within the central nerv-
a complex structure called glial cells. Neurons ous system, Ependymal
that is composed of receive stimuli and con- –found lining the canals
many different types of duct action potentials. of the spinal cord and “Help send out
cells. These all help Glial cells support and brain, Oligodendrocyte
send out impulses and protect neurons and – found around nerve impulses… in
the appropriate mes- perform other functions. fibers in the CNS, order for the
sages in order for the There are five kinds of Schwann – found
human body to move. glial cells; Astrocyte- around nerve fibers in human body to
found on the surfaces of the PNS, and Satellite –
The nervous system is move.”
neurons and blood ves- found around the neu-
made up of neurons
sels, Microglia – found ron cell body. (1)
and non-neural cells.
Bipolar neuron – two nerve
fibers
Unipolar neuron – one nerve
fiber
Multipolar neuron – multiple
nerve fibers
Neurons carry nerve impulses
from body parts to the brain
and spinal
cord
(Picture left
is a neuron
©) (6)
Satelite © (10)
Ependymal (11) ©
Oligodendrocyte (below) (12)
Astrocyte(7) ©
©
Microglia(8) © Schwann(9) © 3

4. Reflex Arc Lab
ANATOMY AND Some of our writers got the chance to go to a local high school and watched as
PHYSIOLOGY they did a lab on neuromuscular reflexes. They used an EKG sensor to compare
WEEKLY the speed of voluntary vs a reflex muscle action and to measure the speed of the
impulse. Here is the information that they collected!
Graph 1
An special 50
collaboration with 45
40
students from NISD 35
30
25 Series2
20 Series1
15
10
5
How much do 0
1 2 3 4 5
you know about
Reflexes? Graph 2
60
50
40
30 Series2
Series1
20
10
0
1 2 3 4 5
After the lab was completed the students were able to answer some ques-
tions, here are their answers! 1.) The contraction wasn’t as high in the volun-
tary activation as in the involuntary activation because you were voluntarily
contracting your muscle. 2.) 0.097 m/s is the speed at which the stimulus
traveled in Agron’s leg. 3.) What could account for the differences is the
measurements of the person, having the electrodes not directly on the
nerves and the force of the hit from the hammer could differ. 4.) The speed
Put together of a nerve impulse is a lot slower than the speed of electricity because it has
many things to go through within the body while electricity in a copper wire
by—Ashley B.
just goes straight from end to end with no interruptions. 5.) The size of a
person can effect the time it takes for the nerve pulses to get to the brain.
4