DR. T.C. MATHEW, Kuwait University

PERIPHERAL PERIPHERAL NERVOUS SYSTEM NERVOUS SYSTEM

AND THEAND THESPECIAL SENSES

DR. T.C. MATHEW, Kuwait University

MENINGES OF THE BRAIN AND SPINAL CORD

The brain and spinal cord is covered by three layers of membranes called the meninges. The outermost membrane is the dura mater. Below the dura is the arachnoid mater. The space that separates these two is called the subdural space. The innermost layer is the pia mater. Between the arachnoid and pia is the subarachnoid space, within which the cerebrospinal fluid circulates.Cerebrospinal fluid (CSF) provides a liquid cushion for the brain and spinal cord. CSF is formed by choroid plexuses in the brain ventricles

DR. T.C. MATHEW, Kuwait University

Anatomy of the Spinal CordAnatomy of the Spinal Cord

DR. T.C. MATHEW, Kuwait University

The Spinal CordThe Spinal Cord It extends from the medulla oblongata Extends from the foramen magnum to the level of

the vertebra L1 or L2

The spinal cord does not extend the entire length of the vertebral column.

The spinal cord shows two enlargements. They are the Cervical enlargement (from 4th

cervical to the first thoracic vertebra) and Lumbar enlargement (from ninth to the 12th thoracic vertebra)

The conical tapering of the spinal cord is called conus medullaris.

Conus medullaris – the inferior end of the spinal cord

Filum terminale – long filament of connective tissue Attaches to the coccyx inferiorly

Cervical and lumbar enlargements Where nerves for upper and

lower limbs arise

Cauda equina – collection of nerve roots

DR. T.C. MATHEW, Kuwait University

Gray Matter of the Spinal Cord and Gray Matter of the Spinal Cord and Spinal RootsSpinal Roots

Shaped like the letter H Gray commissure – contains the central canal Anterior horns – contain cell bodies of motor neurons Posterior horns – consist of interneurons

DR. T.C. MATHEW, Kuwait University

Spinal Nerves Posterior ViewSpinal Nerves Posterior View

31 pairs – contain thousands of nerve fibers

Connect to the spinal cord Named for point of issue from the

spinal cord 8 pairs of cervical nerves (C1-C8)

12 pairs of thoracic nerves (T1-T12)

5 pairs of lumbar nerves (L1-L5)

5 pairs of sacral nerves (S1-S5)

1 pair of coccygeal nerves (C0)

DR. T.C. MATHEW, Kuwait University

Spinal NervesSpinal NervesThe spinal nerve has two major branches. The posterior (dorsal) ramus that innervate the deep muscles and skin of the dorsal surface of the trunk and anterior (ventral) ramus that innervate the muscles and structures of the upper and lower limb and skin of the lateral and ventral surface of the trunk.

DR. T.C. MATHEW, Kuwait University

DISTRIBUTION OF SPINAL NERVES AND PLEXUSES

Except for spinal nerves T1-T12, the anterior rami do not go direcly to the body structures.

Instead they form network by joining the anterior rami of adjacent nerves.

A network of such axons is called a plexus.

They are:Cervical plexusBrachial plexusLumbar plexusSacral plexus Coccygeal plexus

DR. T.C. MATHEW, Kuwait University

The Cervical PlexusThe Cervical Plexus

Formed by ventral rami of first four cervical nervesMost are cutaneous nervesSome innervate muscles of the anterior neckPhrenic nerve – the most important nerve of the cervical plexus

DR. T.C. MATHEW, Kuwait University

The Brachial Plexus and Innervation of the Upper LimbThe Brachial Plexus and Innervation of the Upper Limb

Formed by ventral rami of C5-C8

Cords give rise to main nerves of the upper limb

DR. T.C. MATHEW, Kuwait University

The Lumbar Plexus and Innervation of The Lumbar Plexus and Innervation of the Lower Limbthe Lower Limb

Lumbar plexus Arises from L1-L4

Smaller branches innervate the posterior abdominal wall and psoas muscle

Main branches innervate the anterior thigh

Femoral nerve – innervates anterior thigh muscles

Obturator nerve – innervates adductor muscles

DR. T.C. MATHEW, Kuwait University

The Sacral PlexusThe Sacral Plexus Arises from

spinal nerves L4-S4

Caudal to the lumbar plexus

Often considered with the lumbar plexus Lumbosacral

plexus

DR. T.C. MATHEW, Kuwait University

Sciatic nerve – the largest nerve of the sacral plexus Actually two nerves in

one sheath Tibial nerve –

innervates most of the posterior lower limb

Common fibular (peroneal) nerve – innervates muscles of the anterolateral leg

Innervation of the Lower LimbInnervation of the Lower Limb

DR. T.C. MATHEW, Kuwait University

The Sacral PlexusThe Sacral Plexus

DR. T.C. MATHEW, Kuwait University

AUTONOMIC NERVOUS SYSTEM (ANS)

The ANS is concerned with the innervation of viscera, glands, blood vessels and the heart.

Their regulatory actions are considered to be automatic or autonomous.

The autonomic nervous system is divided into the sympathetic nervous system (SNS) and the parasympathetic nervous system (PSNS).

DR. T.C. MATHEW, Kuwait University

The Sympathetic Nervous System

The SNS generally excites the nervous system. It increases blood flow to the heart, muscles and brain but

decreases functions in the viscera that are not needed for fight or flight.

The most common neurotransmitter used by the SNS is norepinephrine.

The Parasympathetic Nervous System

The PSNS generally inhibits the nervous system. It has a localized and narrow effect, slows the heart rate and

increased intestinal and digestive activities. The most common neurotransmitter used by the PSNS is

acetylcholine (ACh).

DR. T.C. MATHEW, Kuwait University

The Special SensesThe Special Senses

Taste – gustation Smell – olfaction Receptors – classified as chemoreceptors Respond to chemicals

Taste, smell, sight, hearing, and balance

Touch – actually a large group of general senses

DR. T.C. MATHEW, Kuwait University

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