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By the end of this section, you will be able to:
  • Describe the structures found in the PNS
  • Distinguish between somatic and autonomic structures, including the special peripheral structures of the enteric nervous system
  • Name the twelve cranial nerves and explain the functions associated with each
  • Describe the sensory and motor components of spinal nerves and the plexuses that they pass through

The PNS is not as contained as the CNS because it is defined as everything that is not the CNS. Some peripheral structures are incorporated into the other organs of the body. In describing the anatomy of the PNS, it is necessary to describe the common structures, the nerves and the ganglia, as they are found in various parts of the body. Many of the neural structures that are incorporated into other organs are features of the digestive system; these structures are known as the enteric nervous system    and are a special subset of the PNS.

Ganglia

A ganglion is a group of neuron cell bodies in the periphery. Ganglia can be categorized, for the most part, as either sensory ganglia or autonomic ganglia, referring to their primary functions. The most common type of sensory ganglion is a dorsal (posterior) root ganglion    . These ganglia are the cell bodies of neurons with axons that are sensory endings in the periphery, such as in the skin, and that extend into the CNS through the dorsal nerve root. The ganglion is an enlargement of the nerve root. Under microscopic inspection, it can be seen to include the cell bodies of the neurons, as well as bundles of fibers that are the posterior nerve root ( [link] ). The cells of the dorsal root ganglion are unipolar cells, classifying them by shape. Also, the small round nuclei of satellite cells can be seen surrounding—as if they were orbiting—the neuron cell bodies.

Dorsal root ganglion

This micrograph shows the structure of the dorsal root ganglion. The cell bodies of the neurons and the axon bundles are also labeled.
The cell bodies of sensory neurons, which are unipolar neurons by shape, are seen in this photomicrograph. Also, the fibrous region is composed of the axons of these neurons that are passing through the ganglion to be part of the dorsal nerve root (tissue source: canine). LM × 40. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Spinal cord and root ganglion

This micrograph shows a magnified view of the dorsal root ganglion, showing the satellite cells and the cell bodies of sensory neurons.
The slide includes both a cross-section of the lumbar spinal cord and a section of the dorsal root ganglion (see also [link] ) (tissue source: canine). LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

View the University of Michigan WebScope at (External Link) to explore the tissue sample in greater detail. If you zoom in on the dorsal root ganglion, you can see smaller satellite glial cells surrounding the large cell bodies of the sensory neurons. From what structure do satellite cells derive during embryologic development?

Another type of sensory ganglion is a cranial nerve ganglion    . This is analogous to the dorsal root ganglion, except that it is associated with a cranial nerve    instead of a spinal nerve    . The roots of cranial nerves are within the cranium, whereas the ganglia are outside the skull. For example, the trigeminal ganglion    is superficial to the temporal bone whereas its associated nerve is attached to the mid-pons region of the brain stem. The neurons of cranial nerve ganglia are also unipolar in shape with associated satellite cells.

Questions & Answers

normal blood volume in our body
pankaj Reply
5Litres
Albert
what are the advantages of the concave shape of red blood cells?
Amy Reply
This structure is VERY flexible. It can allow these cells to get into the most tiny places in our bodies. a VERY good design! The advantage of red blood cells' biconcave shape is that the surface area is increased to allow more haemoglobin to be stored in the cell.
Saafi
They can stack so that they can move to capillaries
Nejat
action of gluteus medius and minimus
Green Reply
Lateral rotation of the hip joint
Hertzo
Briefly explain location of ecg on a patient
Prince Reply
it is a machine that gives a graphical representation of heart beat
Nani
Briefly explain location of ecg leads on a patient?
Prince
in ecg we use electrical leads over the chest ,ancle and wrist
Nani
what is the anatomical and function difference between paravertebral and prevertebral ganglia ?
Rada Reply
types of tissue in human
Preety Reply
charactetistic Of cartilaginous tissue
Preety
what is theRecurrent infection?
pankaj Reply
what do you mean about recurrent infection
pankaj
Recurrent or persistent infection is a manifestation of primary immuno deficiency
Kedha's
weakens the immune system, allowing infections and other health problems to occur more easily
Kedha's
lysis of RBC
Abdirizack
What is barometric pressure
Kedha's Reply
what is the agglutination advantage
Gopal Reply
the functions of the liver
Nana Reply
it produces bile juice which is used to make the food smaller
Kedha's
it also plays an important role in conversion of amino acid into urea
Komal
it also has role in gluconeogenesis in which amino acids and lipids convert into glucose.
Komal
during fetal life it's a center for hemopoiesis (formation of blood cells)
Komal
it filters, or removes, harmful substances from the blood
Kedha's
It stores nutrients, such as vitamins and iron,for the body
Kedha's
what is the largest gland in human body
Shahid Reply
liver
rachna
correct
Said
correct
dominic
thyroid gland
Kedha's
thyroid is largest endocrine gland
Komal
describe microscopic structures of the kidney
Nana Reply
kidney is covered by fibrous capsule, consists of an outer cortex and inner medulla with medullary pyramids. The microscopic structure is seen as 1-2 millions of nephrons and collecting tubule.
Komal
identify the four major tissue types
Binkheir Reply
connective epithelial
Nana
two ramining
Binkheir
muscle nervous
Nana
epithelial, connective, muscle, and nervous tissue
Mel
tell me about urine formation
Nana Reply
it includes three steps. ultrafiltration selective reabsorption tubular secretion
Komal
ultrafiltration also known as glomerular filteration. All solutes up to 4nm size and water can freely pass through the filtering membrane.
Komal
selective reabsorption : About more than 99% of water ,electrolytes and other substances are reabsorbed by the tubular epithelial cells. The reabsorbed subtances move into interstitial fluid and then into blood of peritubular capillaries .
Komal
The substances like water ,glucose,amino acids and electrolyte are reabsorbed
Komal
tublar secretion: the substances are transported from blood to again into the renal tubules
Komal
and then those are excreted out as urine
Komal
internal and external structures of the kidney
Nana Reply
how the kidney works
Nana
on the bases of pressure and filtration
Said
General
Nana
excretion of wasts, role in hb, role in vit D synthesis
Said
care to explain?
Okoye
yes plx
Nana
difference between apocrine sweat glands and merocrine sweat glands
Binkheir Reply
I believe the apocrine sweat gland uses a sac under the hair follicle and the merocrine sweat gland releases directly on to the surface of the skin
Mark

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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