NERVOUS SYSTEM L2,3 Topography of CN… · neurons of the dorsal horns receive sensory information...

NERVOUS

SYSTEMDr. Amani A. Elfaki

Associate Professor

Department of Anatomy

LEARNING OBJECTIVESBy the end of the lesson the students will be able to:

• Describe the general structure of the brain.

• Identify the cerebrum, the lobes of the cerebrum,the cerebral cortex, and its majorregions/divisions.

• Describe the primary functions of the lobes andthe cortical regions of the brain.

• Identify the dural venous system of the brain.

• Describe the general structure of the spinal cord.

THE NERVOUS SYSTEM

Anatomically Can be Divided into:-

– Central Nervous System

– Peripheral Nervous System

Physiological Can be Divided into:-

– Somatic Nervous System

– Autonomic Nervous System

N.S

C.N.SP.N.S

BRAIN SPINAL CORD CRANIAL

NERVES

SPINAL

NERVES

A.N.S

CNS Cells

• Two cell types

– Neuron

• Conducts nerve impulses

• Cannot be replaced if destroyed

– Neuroglia

• Supports, nourishes, and protects the neurons

• Includes astrocytes, oligodendrocytes, and microcytes

Cerebrum

Each cerebral hemisphere contains of four lobes:

• The frontal lobe controls cognitive ability,memory, behavior, and the ability to speakand write.

• The parietal lobe controls sensorydiscrimination and body orientation.

• The occipital lobe controls the understandingof visual images.

• The temporal lobe controls hearing and theability to understand the spoken word.

Cerebellum, Brain Stem

C71.7 C71.6

Parts of Brain Stem

Midbrain

Pons

Medullaoblongata

Brain Stem/Anterior View

Midbrain

Pons

Medullaoblongata

• The cerebellum: is the second largest area ofthe brain. It is involved with musclecoordination, walking, and speech.

• The brain stem: is at the bottom of the brainand connects the spinal cord to the cerebrum.The pons, midbrain, and medulla oblongataare part of the brain stem. The brain stemcontrols blood pressure, heart beat, breathing,consciousness, and eating and sleepingpatterns.

BRAIN

forebrain midbrain hindbrain

diencephalontelencephalon

medulla

oblongata

pons cerebellumcerebrum

thalamushypothalamussubthalamusepithalamusmetathalamus

Ventricular System

• The ventricles are cavities within the brainthat contain cerebrospinal fluid.

• There are two lateral ventricles, one in eachcerebral hemisphere.

• The third ventricle is located near thehypothalamus and thalamus.

• The fourth ventricle is located between themedulla oblongata and the pons and thecerebellum.

Cerebrospinal Fluid

• Formed in the ventricles of brain

• Weight of brain outside CSF = 1500gms

• Weight of brain inside CSF = 50gms

• Stabilizing brain during head movement

• Shock absorber.

Pineal and Pituitary Glands

• The pineal gland: is a small endocrine gland inthe vertebrate brain. The pineal glandproduces melatonin, a serotonin derivedhormone which modulates sleep patterns inboth circadian and seasonal cycles.

• The pituitary gland: is located at the base ofthe brain. The pituitary gland produces severalhormones including growth hormone. Thepituitary gland also regulates and controlsother hormone-secreting glands.

Cranial Nerves

The cranial nerves named as follow:-

1. Olfactory (Sensory)

2. Optic (Sensory)

3. Oculomotor (Motor)

4. Trochlear (Motor)

5. Trigeminal (Mixed)

6. Abducent (Motor)

7. Facial (Mixed)

8. Vestibulocochlear (Sensory)

9. Glossopharyngeal (Mixed)

10. Vagus (Mixed)

11. Accessory (Motor)

12. Hypoglossal (Motor)

Meninges

Definition

• Outer coverings of brain &

spinal cord

• Dura mater, arachnoid mater

& pia mater

Meningeal Spaces

• Epidural space

• Subdural space

• Subarachnoid space

• Intracerebral

Dural Reflections

• Falx cerebri

• Tentorium cerebelli

• Diaphragma sellae

• Falx cerebelli

Dural Reflections

Dural Reflections

Spinal Cord

External features Internal features

External Features

• Cylindrical in shape, which runs in thevertebral canal

• Surrounded by three meninges<pia,arachnoid, dura mater>

• Formed of 31 spinal segments were eachsegment provide a pair of spinal nerve.

• Length 45 cm• Weight 35 grams• Diameter is about I cm

Spinal Cord

Spinal Segments

Spinal segments are:• 8 cervical

• 12 thoracic

• 5 lumber

• 5 sacral

• 1 coccygeal

SPINAL NERVES

• 8 cervical

• 12 thoracic

• 5 lumber

• 5 sacral

• 1 coccygeal

VERTEBRAE

• 7 cervical

• 12 thoracic

• 5 lumber

• 5 sacral

• 4 coccygeal

Internal Features• The arrangement of gray and white matter in the spinal cord is

relatively simple: The interior of the cord is formed by gray matter,which is surrounded by white matter.

• In transverse sections, the gray matter is conventionally divided intodorsal (posterior), lateral and ventral (anterior) “horns.” Theneurons of the dorsal horns receive sensory information that entersthe spinal cord via the dorsal roots of the spinal nerves. The lateralhorns are present primarily in the thoracic region, and contain thepreganglionic visceral motor neurons that project to thesympathetic ganglia. The ventral horns contains the cell bodies ofmotor neurons that send axons via the ventral roots of the spinalnerves to terminate on striated muscles.

• The white matter of the spinal cord is subdivided into dorsal (orposterior), lateral, and ventral (or anterior) columns, each of whichcontains axon tracts related to specific functions

Internal Features