Elizabeth's AP Blog

Friday, April 07, 2006

New Blog Site

I made a new blog because this one is too slow.

http://elizabethanatomy3.blogspot.com

posted by Elizabeth @ 10:09 AM 0 comments

Tuesday, March 07, 2006

Peripheral Nervous System, Peripheral Nerves & Structure Of The Vertebrae


Peripheral Nervous System


The Peripheral Nervous System (PNS) contains
only nerves and connects the brain and spinal cord
(CNS) to the rest of the body.

The PNS includes the cervical, thoracic, lumbar and
sacral nerves that extend to the rest of the body from
the spinal cord.

The PNS consists of the neurons not included in the
brain and spinal cord.

- Two Main Componens of the PNS -

1. Sensory (afferent) = Pathways that provide input
from the body and transmit it toward the CNS
(Central Nervous System).
These are called Afferent Neurons.

2. Motor (efferent) = Pathways that transmit
information away from the CNS. These are called
Efferent Neurons.


 - The PNS Is Divided Into 2 Major Parts -

Somatic Nervous System and Autonomic Nervous System

1. Somatic Nervous System

The somatic nervous system regulates activites
that ARE under conscious control, movement
of skeletal muscles. The somatic nervous system
consists of peripheral nerve fibers that send sensory
information to the central nervous system AND
motor nerve fibers that project to skeletal muscle.

2. Autonomic Nervous System

The Autonomic Nervous System regulates activites
that are automatic or involuntary. The nerves of the
autonomic nervous system control functions of the
body that are NOT under consious control.
Examples would be :: contractions of the heart,
heart rate, digestion, breathing and salavation.



The Neuron


Neurons are cells that carry messages
throughout the nervous system. The neuron is
the basic functional unit of the nervous system.


- A Neuron Consists Of 3 Main Parts -

1. Cell Body = Largest part. Consists of nucleus
and most of the cytoplasm, synthesizes protein.

2. Dendrites = Short branch extensions spreading
out from the cell body. Receives stimulus and carries
impulses from the environment or other neurons and
carry them toward the cell body.

3. Axon = A long fiber that carries impulses away
from the cell body.

A. Myelin Sheath

The axons of most neurons are covered with a lipid
layer called the Myelin Sheath. The myelin sheath helps
speed up nerve impulse.

B. Schwann Cells

In the PNS myelin is produced by Schwann Cells,
which surround the axon.
















Photo from :: http://en.wikipedia.org/wiki/Neuron



The Spinal Cord


1. The spinal cord acts like a communication link
between the brain and the peripheral nervous system.

2. The spinal cords starts at an opening at the base
of the skull, it stretches downward through the vertebral
column.

3. There are 31 pairs of spinal nerves, which are part of
the PNS, that emerge from the spinal cord












Photo from :: http://staff.washington.edu/chudler/introb.html



Structure of The Vertebrae


1. The vertebral column provides protection to
the spinal cord, which runs through its central cavity.

2. There are a total of 24 individual vertebrae in
the spinal column, plus the fused vertebrae that
make up the coccyx and sacrum.

3. The vertebrae are divided into regions, and
there are a specific number in each region.

















Photo from :: http://staff.washington.edu/chudler/introb.html


Cervical - towards the top, near the skull. The cervical
region has 7 vertebrae







Photo Of Cervical Bone
Photo from :: http://www.crnasomeday.com/anatpages/spinal.htm


Thoracic - is under the cervical region and has 12 vertebrae.









Photo Of Thoracic Bone
Photo from :: http://www.crnasomeday.com/anatpages/spinal.htm



Lumbar - is under the thoracic region and has 5 vertebrae








Photo Of Lumbar Bone
Photo from :: http://www.crnasomeday.com/anatpages/spinal.htm



Sacral - is under the lumbar region and has 5 vertebrae











Photo Of The Sacrum - Anterior View
Photo from :: http://www.crnasomeday.com/anatpages/spinal.htm


Coccyegeal - has 4 vertebrae, is located at the bottom
part of the sacrum


- Intervertebral Discs -

Intervertebral discs are located between each
vertebrae. These discs form strong joints and
absorb spinal compression shock


- Ligaments -

Ligaments hold the vertebrae in position and
connect bones to bones


- Facet Joints -

Facet Joints allow for movement between the
individual vertebrae of the spine.


















Photo From ::
http://www.familydoctor.co.uk


- General Characteristics Of A Typical Vertebra -

Laminae = extends from the body to cover the spinal
canal, which is the hole in the center of the vertebrae.

Spinous Process = is the bony portion opposite the
body of the vertebra. You feel this part if you run your
hand down a person's back.

Transverse Process = There are two transverse
processes, where the back muscles attach to the
vertebrae.

Pedicle = is a bony projection that connects to both
sides of the lamina.

Body = the largest part of a vertebra

Vertebral Formen = The opening formed by the
union of the vertebral arch with its body
















Photo From :: www.uhn.ca/programs/spine/understanding.asp



Peripheral Nerves


1. The peripheral nerves branch off of the cervical,
thoracic, lumbar and sacral regions of the vertebral
column, exiting through holes in the vertebral column.

Cervical Nerves (C1-C8) - controls signals to the
arms, neck and hands

Thoracic Nerves (T1-T12)- controls signals to the
torso and parts of the arms

Lumbar Nerves (L1-L5)- relays signals to the legs
and hips

Sacral Nerves (S1-S5) - controls signals to the toes,
groin and parts of the legs


2. The nerves that exit the spinal column are labelled
according to the level of the hole from which they
emerge.

This can get confusing because there are eight
cervical nerves – as a result, the first seven nerves
(C1-C7) exit from the holes above the first seven
vertebrae (C1-C7); however, the eighth nerve (C8)
emerges from the hole below C7. All of the remaining
nerves exit from the hole below their corresponding
vertebra.













Cervical nerves and how they fit into the vertebral column
photo drawn by me










Photo From ::
http://www.backrack.co.uk/nervous_index.shtml

posted by Elizabeth @ 6:41 PM 5 comments