1

The nervous system is a com-

plex system that is mainly divid-

ed into two sections the Cen-

tral Nervous System (CNS)

which is the brain and spinal

cord and the Peripheral Nerv-

ous System (PNS) which con-

sists of the cranial nerves (1).

The nervous system

can be broken down into other divisions and sub divisions. Sen-

sory (afferent) division transmits

information from periphery to

CNS, contains receptors.

Somatic receives sensory

information from skin, fascia,

joints, skeletal, muscles, special

senses. Visceral receives senso-

ry information from viscera.

Motor (efferent) division trans-

mits information from body

CNS to the rest of the body,

send motor information to ef-

fectors. Somatic motor volun-

tary nervous system: innervates

skeletal muscle

Autonomic motor involun-

tary nervous system innervates

cardiac muscle, smooth muscle,

glands .

Organization of the Nervous System!! Written by— Agron

Nerve Impulses Part 1 Written by—Kamiera

Membrane potential is

when a neuron is adequately

stimulated , an electrical im-

pulse is generated and conduct-

ed along the length of its axon.

This is response , called the

action potential or nerve im-

pulse , is always the same re-

gardless of the source or type

of stimulus , and it underlies virtually all functional activities

of the nervous system. (2)

Membrane channels

are large proteins , often with

several subunits , whose amino

acid chains snake back and

forth across the membrane.

Some channels , leakage or no

leakage channels , are always

open. Channels include :

Chemically gate, Ligand-gated,

Voltage-gated, and Mechani-

cally gated . (2)

There is also Resting

Membrane Potential, which is The potential difference in a

resting neuron and the mem-

brane is said to be polarized.

The value of the resting mem-

brane potential varies from -

40mV to -90mV in different

types of neurons. The resting

potential exits only across the

membrane. (2)

ANATOMY &

PHYSIOLOGY

WEEKLY

10.17.2012 Volume 1, Issue 1 (Informational Section)

Anatomy and

Physiology Weekly Inside this issue:

Organization of

the Nervous

System

1

Nerve Impulses

Part 1

1

Nerve Impulses

Part 2

2

The Synapse 2

Cells of the

Nervous System

3

Reflex Arc 4

Picture is © (3) Get ready to learn all about the nervous system in this new issue of Anatomy and Physiology Weekly!

2

Membrane Potential: difference in electrical

charge across their plasma membranes.

Resting Membrane Potential: the mem-

brane potential maintained by a noncon-

ducting neuron’s plasma membrane.

Local Potential: A slight shift away from the

RMP in a specific region of the plasma mem-

brane.

Action Potential: is, as the term suggests,

the membrane potential of an active neu-

rons, that is, one that is conducting an im-

pulse. An example of this is shown below.

1. A stimulus triggers stimulus-gated Na+

channels to open and allow inward Na+

diffusion. This causes the membrane to de-

polarize.

2. As the threshold potential is reached,

voltage-gated Na+ channel open.

3. As more Na+ enters the cell through

voltage-gated Na+ channels, the membrane

depolarized even further.

4. The magnitude of the action potential

peaks (at +30 mV) when voltage-gated Na+

channels close.

5. Repolarization begins when voltage-gated

K+ channels open, allowing outward diffu-

sion of K+.

6. After a brief period of Hyperpolarization,

the resting potential is restored by the sodi-

um-potassium pump and the return of ion

channels to their resting state.

Neurotransmitters: chemicals that allow

the transmission of signals from one

neuron to the next across synapses.

They are found at the axon endings of

motor neurons, where they stimulate

the muscle fibers. They and their close

relatives are produced by some glands

such as the pituitary and the adrenal

glands . (1)

Synapse: Functional membrane to mem-

brane contacts of a nerve cell with an-

other nerve cell, muscle cell, gland, cell

or sensory receptor; functions in the

transmission of action potenitals from

one cell to another.

Summation: Phenomena in which the

degree of changing in membrane poten-

tial directly correlates with stimulation

frequently.

Nerve Impulses Part 2 Written by—Colton

The Synapse Written by—Jasmine

“Summation is a

phenomena in

which… degree of

changing membrane

potential directly

correlates with

stimulation”

Page 2 Anatomy and Physiology Weekly

© (4)

© (5)

3

The nervous system is

a complex structure

that is composed of

many different types of

cells. These all help

send out impulses and

the appropriate mes-sages in order for the

human body to move.

The nervous system is

made up of neurons

and non-neural cells.

Non-neural cells are also

called glial cells. Neurons

receive stimuli and con-

duct action potentials.

Glial cells support and

protect neurons and

perform other functions. There are five kinds of

glial cells; Astrocyte-

found on the surfaces of

neurons and blood ves-

sels, Microglia – found

within the central nerv-

ous system, Ependymal

–found lining the canals

of the spinal cord and

brain, Oligodendrocyte

– found around nerve

fibers in the CNS, Schwann – found

around nerve fibers in

the PNS, and Satellite –

found around the neu-

ron cell body. (1)

Cells of the Nervous System Written by—Ashley B.

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)

“Help send out

impulses… in

order for the

human body to

move.”

Page 3 Volume 1, Issue 1 (Informational Section)

Astrocyte(7) ©

Satelite © (10)

Microglia(8) ©

Ependymal (11) ©

Schwann(9) ©

Oligodendrocyte (below) (12)

©

4

An special

collaboration with students from NISD

ANATOMY AND

PHYSIOLOGY

WEEKLY

Reflex Arc Lab

How much do

you know about

Reflexes?

Some of our writers got the chance to go to a local high school and watched as

they did a lab on neuromuscular reflexes. They used an EKG sensor to compare

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

Graph 2

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

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

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.

Put together

by—Ashley B.

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