TEST 2/QUIZ 4 CH 9 - CEREBROSPINAL FLUID AND BBB

Describe a lumbar puncture and explain its purpose.

A lumbar puncture, also called a spinal tap, samples the cerebrospinal fluid from the subarachnoid space at the lower end of the spinal cord. This procedure is performed to sample the chemical environment of the brain and test for infection. An infection is indicated by proteins or blood cells found in the sample.

Cerebrospinal fluid is produced by the A) choroid plexus. B) arachnoid villi. C) frontal sinuses. D) pia mater. E) ventricles.

A) choroid plexus.

The ________ is a salty fluid continuously secreted into hollow cavities known as ________. This fluid is secreted into these cavities by the ________, a specialized tissue consisting of capillaries and transport epithelium.

Answer: cerebrospinal fluid (CSF), ventricles, choroid plexus

Extracellular fluid is a protective component of the CNS. The ________ fluid, found inside the pia mater, and the ________ fluid, found in ventricles between the pia mater and arachnoid membrane, make up the extracellular environment for neurons. They communicate across leaky junctions of the ________ membrane and the ________ cell layer that lines the ventricles.

Answer: cerebrospinal, interstitial, pial, ependymal

Two areas of the brain missing the blood-brain barrier are the ________ and ________.

Answer: posterior pituitary, the (vomiting center of the) medulla

Which of these has a higher concentration in cerebrospinal fluid than in the blood? A) K+ B) H+ C) Ca2+ D) HCO3- E) Na+

B) H+

Describe the physical protection afforded by the cerebrospinal fluid.

Because the brain floats on CSF there is less weight and, therefore, less pressure on the blood vessels and nerves attached to the CNS. The fluid also pads the brain so it is less likely to hit the cranium and risk bruising when there is a blow to the head.

Describe cerebrospinal fluid flow from secretion to absorption.

Cerebrospinal fluid is secreted from the choroid plexus. It flows into the subarachnoid space -between the pia mater and arachnoid membrane- to surround the brain and spinal cord. CSF is absorbed back into the blood at arachnoid villi -located in the cranium).

Parkinson's disease affects the cerebral basal ganglia, resulting in tremors in limbs, slowness in beginning and completing movements, and other abnormalities of muscle control. The specific population of neurons involved degenerates and thus fails to produce the neurotransmitter dopamine. An obvious treatment option to try is to administer dopamine, yet this is completely ineffective at alleviating the symptoms. Propose a reason why this treatment fails, and a related alternative to address the dopamine deficit. Hint: Think about how the brain protects itself from chemicals in the blood.

Dopamine administered to a Parkinson's patient fails to cross the blood-brain barrier. Treatment with the dopamine precursor l-dopa, however, is effective, as this molecule can cross the barrier.

If a diabetes mellitus patient continually has high blood glucose, what is likely to happen to the nervous system, and what are the possible outcomes?

With too much glucose present, the blood-brain barrier cells may remove glucose transporters from the patient's membranes. If blood glucose drops due to insulin therapy, the brain neurons may be unable to obtain sufficient glucose to function or remain alive. This can lead to a comatose state or even death.