UOfT Physiology - SCS 2159 - Lecture 09 -

Neuro 06 Exam Study Guide

How many neurons and synapses in the CNS? - Answer 100 billion (10^11) neurons, 100

trillion (10^14) synapses.

Neuroglia compose (?)% of the CNS - Answer 75-90%

Subarachnoid Space - Answer Shock absorbing space filled with cerebrospinal fluid

(CSF)

CSF - Answer Cerebrospinal fluid, a clear, watery fluid, similar to plasma, cushions

brain and maintains a stable interstitial fluid environment.

Volume of CSF in adults - Answer 125mL-*150mL*.

Composition of CSF compared to plasma - Answer Less proteins, glucose and *K+*.

More sodium and chloride.

CSF circulation - Answer 1. CSF is secreted by ependymal cells of the choroid plexus

(Mostly in lateral ventricles).

2. CSF flows from lateral ventricles and 3rd ventricle through the cerebral aqueduct into

the 4th ventricle.

3. CSF in 4th ventricle flows into subarachnoid space by passing through openings in

the roof of the 4th ventricle. These openings are the paired lateral apertures and the

single median aperture. CSF also fills the central canal of the spinal cord.

4. As it travels through the subarachnoid space, CSF removes waste products and

provides buoyancy for the brain and spinal cord.

5. CSF is recycled when reabsorbed by arachnoid villi. It exits the subarachnoid space

and enters the bloodstream.

Blood-Brain Barrier - Answer Special anatomy within the subarachnoid space consisting

of capillaries with tight junctions that block the passage of larger substances that aren't

actively transported.

Astrocytes eliminate those substances that were "denied entry".

Spinal Nerve - Answer 31 pairs. C1-C8 cervical nerves. T1-T12 thoracic nerves. L1-L5

sacral nerves. Co Coccygeal nerve.

Dermatome - Answer Sensory area of skin supplied by a single spinal nerve

Function of dorsal grey matter - Answer Dorsal horn. Sensory function (*remember*)