Ch. 7 (p. 248 – 255)

PROTECTION OF THE CNS

OBJECTIVE CHECKLIST

Name the three meningeal layers, and state their functions.

Discuss the formation and function of the cerebrospinal fluid and the blood-brain barrier.

Compare characteristics of concussions and contusions.

Describe CVAs(strokes) and their impact on brain function.

PROTECTION OF THE CNS

Nervous tissue is very delicate and is easily damaged

Your body protects the brain and spinal cord by enclosing them within …

The skull and vertebral column

Membranes (meninges)

Cerebrospinal fluid

Protection from harmful substances in the blood is provided by the blood brain barrier.

THE MENINGES

There are three connective tissue membranes covering the CNS.

They serve several functions:

Cover and protect the CNS

Protect blood vessels

Contain cerebrospinal fluid

Form partitions in the skull

DURA MATER

Dura mater is the outermost and strongest membrane covering the CNS.

It is a double-layered external covering

Fused together and folds inward, partitioning the brain

DURA MATER

DURA MATER

We do not see this o

n the

sheep brain, but this is

what it WOULD look like…

It can divide up sections of the brain

ARACHNOID MATER

Arachnoid mater is the middle meningeal membrane covering the CNS

Beneath is the subarachnoid space

Thread-like extensions span this space and secure the arachnoid mater to the pia mater.

This space is filled with cerebrospinal fluid and blood vessels serving the brain.

ARACHNOID MATER

This is th

e only mater

visible on th

e sheep

brain

ARACHNOID MATER

PIA MATER

Pia Mater is the innermost meningeal membrane covering the CNS

Clings to the surface of the brain, following every fold

Very delicate and rich with blood vessels supplying the brain

MENINGITIS

Meningitis is the inflammation of the meninges.

It is caused by either bacteria or viruses that may spread into the nervous tissue.

The condition is usually diagnosed by taking a sample of CSF from the subarachnoid space in the lumbar region of the spine.

Video: Meningitis

CEREBROSPINAL FLUID (CSF)

Similar to blood plasma composition

Formed by the choroid plexus (of the epithalmus)

Forms a watery cushion to protect the brain

Circulated in arachnoid space, ventricles, and central canal of the spinal cord

Also helps supply brain with nutrients

VENTRICLES AND LOCATION OF CSF

VENTRICLES AND LOCATION OF CSF

CEREBROSPINAL FLUID (CSF)

CSF is absorbed into the venous blood in the dural sinuses through the arachnoid villi.

CEREBROSPINAL FLUID (CSF)

MRA is often used to evaluate the blood vessels of the neck and brain

HYDROCEPHALUS

Hydrocephalus occurs when CSF accumulates in and around the brain, exerting pressure.

In newborns, the entire cranium enlarges.

In adults, hydrocephalus can result in brain damage.

Treatment involves inserting a shunt into the ventricles that drains the fluid into a vein in the neck.

BLOOD-BRAIN BARRIER (BBB)

Includes the least permeable capillaries of the body (due to tight junctions)

Glucose, water, essential amino acids pass easily through the walls of the capillaries

Excludes many potentially harmful substances such as metabolic waste (urea, toxins, many proteins, and drugs)

BLOOD BRAIN BARRIER (BBB)

Useless against some substances

Fats and fat soluble molecules

Respiratory gases

Alcohol

Nicotine

Anesthesia

TRAUMATIC BRAIN INJURIES

Traumatic Brain Injuries are a leading cause of accidental death in the U.S.

A concussion occurs when the brain injury is slight but there is no permanent damage.

A contusion occurs when brain tissue is destroyed

A contusion of the brain stem results in coma. Why?

After head blows, death can result from bleeding or edema, why?

Vid

eo: C

on

cussio

ns

CEREBROVASCULAR ACCIDENTS (CVAS)

Cerebrovascular Accidents (CVAs), AKA: Strokes are the 3rd leading cause of death in the U.S.

CVAs occur when blood circulation to the brain area is blocked

Caused by either a blood clot or a ruptured blood vessel

When this occurs, brain tissue dies.

Temporary restriction of blood flow is known as Transient Ischemic Attach (TIA) and can last 5-50 minutes.

Defects are not permanent but serve as a warning for CVAs.

Vid

eo: S

trokes

OBJECTIVE CHECKLIST

Name the three meningeal layers, and state their functions.

Discuss the formation and function of the cerebrospinal fluid and the blood-brain barrier.

Compare characteristics of concussions and contusions.

Describe CVAs(strokes) and their impact on brain function.

QUESTIONS, COMMENTS?