Lecture 5 Flashcards
Where is the best place to obtain a sample of cerebrospinal fluid?
Subarachnoid space, lumbar region
How much CSF is produced a day?
120 mL
Where is CSF produced?
Ventricles
What kind of cells produce CSF?
Ependymal cells
Where does CSF drain into?
Dural sinuses and dural lymph vessels
What is the function of CSF?
Provides watery protective cushion for CNS, absorbs neuron metabolites during sleep
What is it called if the ventricles fill with CSF because of a blockage somewhere?
Hydrocephalus (big head in a baby)
Want ______ and _______ of CSF to match
Production and Drainage
Ventricle should be _______
Symmetrical
What is the choroid plexus?
-Wrinkly structure found inside the brain ventricles
What is the choroid plexus composed of?
Ependymal cells (produces CSF)
What does the cerebral aqueduct conect?
The 3rd ventricle to the 4th ventricle
What is the flow of CSF through the ventricles?
L/R Lateral ventricles –> 3rd ventricle –> cerebral aqueduct –> 4th ventricle –> subarachnoid space –> dural sinuses
What are the 6 stages of the developmental process?
- Mitosis
- Migration
- Differentiation
- Synaptogenesis
- Apoptosis
- Myelination
In the mitosis stage, when do neurons stop dividing?
In the 5th prenatal month
*The only place neurons continue dividing throughout life is the olfactory bulb and hippocampus
In the mitosis stage, what do neuroblasts (immature cells) divide into?
Neurons or glial cells
What happens during the migration stage?
Neurons move to their correct locations
When does migration end?
by the 7th prenatal month
What can happen if neurons migrate to the wrong location?
Heterotopia (seizures)
What is differentiation based on?
Neuron location
When does differentiation occur?
Pre-natal
What is synaptogenesis and what does it require?
Synapse formation, requires gene expression
When does synaptogenesis occur?
Pre-natal to death
What is apoptosis?
Programed cell death
*Neurons that don’t form synapses are removed
When does myelination begin and when is it completed?
Begins: 4th pre-natal month (most by age 3)
Ends: early 20s (reigns in impulsive behaviors)
What increases myelination?
Stimulation of neurons
Which 3 stages are involved in neural plasticity?
Synaptogenesis, apoptosis, and myelination
What neuron types are seen in peripheral nerves?
- Voluntary motor neurons (skeletal muscle)
- Somatosensory neurons (skin, muscle, sub Q tissue)
- Autonomic neurons (smooth and cardiac muscle)
What are the three peripheral nerve plexuses?
- Cervical plexus (C1-C4): innervates neck and diaphragm
- Brachial plexus (C5-T1): innervates UE
- Lumbosacral plexus (L1-S5): innervates LE and pelvic floor
A typical peripheral nerve contains ______ (amount) of axons
Thousands
What is every axon (myelinated or unmyelinated) surrounded by?
Endoneurium (thin sheath of connective tissue)
Where is the endoneurium located in relation to the myelin sheath?
Endoneurium is external to the myelin sheath
What is a fasicle?
Cluster of axons
What is each fasicle surrounded by?
Perineurium (sheath of connective tissue)
What is the entire peripheral nerve surrounded by?
Epineurium (somewhat thicker sheath of connective tissue)
What increases blood flow to axons and fluid flow within axons?
Movement
In an injured peripheral nerve, what happens first motor loss or loss of sensation?
Loss of sensation
At what rate to axons regenerate in a peripheral nerve?
1 in/month
What helps guide axons regrowth?
Schwann cells –> they secrete growth factor that forms tunnels to guide axons
