Vet. Neuroanatomy

11/5/2014

Prof. Dr. Fawzy Elnady

Introducing Vet. Neuroanatomy

Function of the nervous system

1. The nervous system coordinates and controls body activity.

2. Receive information (from ext./int. environment)

3. Analyze and integrate that information.

4. Bring the appropriate response.

The Structures of the Nervous System

There are two major divisions of the nervous system:

The central nervous system (CNS) consists of the brain and spinal cord

The peripheral nervous system (PNS) consists of the cranial and spinal nerves, autonomic nervous system, and ganglia

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NervousSystem

Topographically Functionally

Type of Direction CNS PNS info of fibers

Autonomic Spinal Intramural Nn & their Brain Cr. Nn Sp. Nn Plexuses Somatic Visceral Afferent Efferent cord ganglia

Sympathetic Parasymphathetic

The building blocks of the Nervous system

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Somatic motor neuron

• Dendrites: transmit information toward the cell body

• Axons: transmit information away from the cell body

Neurons by function

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A neuron may synapse on another neuron’s dendrites, cell body, or synaptic ending.

The building blocks of the Nervous system

Supporting cells

Neuroglia or glial cells: • Glial cells (glue) are the supportive cells of the nervous system consist of – astrocytes – microglia – ependymal cells – oligodendrocytes – Schwann cells

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The Gap = synapse

The space between two neurons or between a neuron and receptor is the synapse Chemical substances called neuro‐transmitters are released into the space to allow information to be relayed

A neuron may synapse on another neuron’s dendrites, cell body, or synaptic ending.

Cells that produce the myelin sheath

Schwann cells

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Gaps in the myelin sheath that allow the passage of oxygen and nutrients Nodes of Ranvier

The part of the neuron that contain the nucleus

Cell body

The membrane surrounding the nerve cell

Neurilemma

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Dense connective tissue holding nerve fibers together

Neuroglia

Group of cell bodies found in the PNS

Ganglia

The space between two neurons Synapse

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The space between a neuron and a muscle fiber

Neuromuscular junction

The chemical that allows the transmission of a nervous impulse neurotransmitter

Short projections that receive impulses Dendrite

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Long projections that transmit impulses

Axons

Nerve Regeneration

Bony protection of CNS

SKULL

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Bony protection of CNS

Vertebral column

The Discs (intervertebral discs)

The vertebrae are protected from each other by IVD

IVD are layers of fibrocartilage that form pads separating and cushioning the vertebrae from each other

The Discs (intervertebral discs)

 Outer Annulus fibrosus

 Central Nucleus pulposus

 no innervation or possible that outer disc innervated

 Avascular

 Thicker in neck and lumbar regions

 Thickest in coccygeal

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Lumbar spinal cord after removal of vertebral laminae. dorsal view.

Severe compression of spinal cord by extradural malignant lymphoma. Cat.

The Spinal Meninges

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Meninges = membranes

 3 membranes surround CNS  The spinal and cranial (cerebral) meninges are continues at the foramen magnum.

Dura mater Arachnoid

Pia mater

Denticulate ligaments

 The pia mater is bilaterally thickened along the lateral surface of the spinal cord, Midway between successive spinal roots .  Extensions of the pia mater traverse the subarachnoid space, arachnoid mater and attach to the dura mater between the dorsal and ventral roots of spinal nerves.  Thus the denticulate ligaments suspend the SC laterally in the CSF within the subarachnoid space.

Arachnoid mater Def.

Thin transparent Avascular membrane between dura and pia maters. Shape: Spider‐web like appearance due to has numerous trabeculae & filaments.  It is pressed against the dura by CSF pressure. Separated from pia by SubArachnoid Space (SAS), which is filled with (CSF).

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Which layer of the meninges is present in the spinal cord but not in the brain?

Epidural space

Which one of the following statements concerning the meninges of the brain and spinal cord is true?

The meninges consist of three layers, which from superficial to deep are the dura mater, arachnoid membrane, and pia mater The superficial‐to‐deep sequence of the meninges on the brain is inverse to that of the spinal cord. The cerebrospinal fluid (CSF) is contained in the subdural space of both the brain and spinal cord. The arachnoid membrane is the finest, most delicate layer, of a spiderweb, that ﯾذﻛرﻧﺎ ﺑﺷﺑﻛﺔ اﻟﻌﻧﻛﺑوت reminiscent immediately surrounds the surface of the brain and spinal cord.

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Cauda Equina …. How it is formed?

 in the Adult horse:  the cauda equina starts @ the lumbosacral junction.

 the conus medullaris extends to S1

 the filum terminale extends to S4

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Structures forming the Cauda Equina:

1‐ Conus medullaris 2‐ Filum terminale 3‐ Spinal nerves (that flank 1 and 2)

Lumbosacral portion of spinal cord

Median section

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Which one of the following statements regarding the spinal cord is true?

It possesses neurons associated with the parasympathetic nervous system in the region of the intermediate horn.

It extends the length of the vertebral canal.

It receives sensory neurons through the dorsal horn.

It contains nerve cell bodies within its white matter and axonal processes within its grey matter.

Early SPINAL CORD Development

Regions of Developing Neural Tube

Alar Plate

Basal Plate

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Cs spinal cord

Arrangement of gray and white matter in the spinal cord:

(1) Dorsal gray column

(2) Lateral gray column (intermediate gray matter)

(3) Ventral gray column

(4) Dorsal funiculus

(5) Lateral funiculus

(6) Ventral funiculus.

The Mature Spinal Cord

Gray matter

Cervical enlargement ‐ C5 ‐ T2

Lumbar enlargement ‐ L4 –S2

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Model of sympathetic innervation. Preganglionic cells can synapse (A) on postganglionic cells a few segments cranial in the sympathetic trunk; (B) on a postganglionic cell at the segment where the postganglionic fiber emerges; (C) on a postganglionic cell caudal in the sympathetic trunk; (D) the preganglionic cell can bypass the sympathetic trunk ganglia and synapse in the prevertebral ganglia.

(1) Preganglionic cell body; (2) Spinal nerve; (3) Ramus communicans; (4) Postganglionic cell body; (5) Sympathetic trunk ganglion; (6) Sympathetic trunk.

Roots and branches of a spinal nerve

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The Mature Spinal Cord ‐ 3

White matter

Dorsal funiculus

Lateral funiculus

Ventral funiculus

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THE AUTONOMIC NERVOUS SYSTEM

‘NO ONE TELLS ME WHAT TO DO!’’

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Summary of major PNS subdivisions