Nervous system cast of characters Flashcards
What three parts are there to neurons and what parts can be seen on Nissle staining?
Dendrites (receive input), cell bodies, axons (send output).
Dendrites and cell bodies can be seen on Nissle. Axons have no RER.
What is Wallerian degeneration of neurons?
- Degeneration distal to axon injury
- Axonal retraction proximally, macs come clean up debris
- Intact nerve fiber sprouts towards remnants of neurolemma, allows for slow regeneration (PNS>CNS).
What are the most abundant cell type in the brain?
Astrocytes.
What are some of the functions of astrocytes?
Physical support, blood brain barrier.
Repair, reactive gliosis in response to injury.
K+ metabolism, removal of excess NTs, glycogen fuel reserve buffer.
What is the marker of astrocytes? What are they derived from?
GFAP. Neuroectoderm.
Which cells are the phagocytic scavengers of the CNS? What is their lineage?
Microglia. Mesodermal, of mononuclear origin.
What are microglia activated by? What happens with HIV infection?
Activated by tissue damage. When infected by HIV, fuse to form giant multinucleated cells.
Can microglia be seen on Nissle stain?
Not really.
What is the purpose of the myelin sheath?
To increase conduction velocity of signals transmitted down axons, via saltatory conduction of action potentials at the nodes of ranvier.
What characterizes nodes of ranvier?
High concentration of sodium channels.
What cells make up myelin sheath in CNS and PNS?
CNS: oligodendrocytes
PNS: Schwann cells.
What are schwann cells derived from? How are they different from oligos?
Derived from neural crest, each schwann myelinates only 1 PNS axon. Promote axonal regeneration.
What is bilateral acoustic schwannomas assciated with?
Internal acoustic meatus schwannomas, bilateral associated with neurofibromatosis type 2.
What do oligodendrocytes look like histoligically? What are they derived from?
fried egg appearance. Derived from neuroectoderm. Each oligo can myelinate up to 30 axons.
What type of sensory receptor is responsible for pain and temperature?
Free nerve endings.
What kinds of free nerve ending sensory receptors are there?
C - slow, unmyelinated fibers.
Adelta - fast, myelinated fibers.
What is the location of free nerve ending sensory receptors?
All skin, epidermis, some viscera
What kind of receptors are meissner corpuscles?
Large, myelinated fibers that adapt quickly.
What is the location of meissner corpuscles?
Glabrous (hairless) skin.
What senses are meissner corpuscles responsible for?
Dynamic, fine/light touch, position sense.
What kind of receptors are pacinian corpuscles?
Large myelinated fibers that adapt quickly.
Where are pacinian corpuscles located?
Deep skin layers, ligaments, joints.
What senses are pacinian corpuscles responsible for?
Vibration, pressure.
What kind of receptors are merkel discs?
Large myelinated fibers that adapt quickly.
Where are merkel discs located?
finger tips, superficial skin.
What senses are merkel discs responsible for?
pressure, deep static touch (eg shapes, edges), position sense.
What kind of receptors are ruffini corpuscles?
Dendritic endings with capsule. Adapt slowly.
Where are ruffini corpuscles located?
Finger tips, joints.
what senses are ruffini corpuscles responsible for?
Pressure, slippage of objects along surface of skin, joint angle change.
What does endoneurium contain?
Single nerve fiber layers.
What does perineurium contain?
Surrounds a fascicle of nerve fibers.
What does Epineurium contain?
Dense connective tissue that surrounds entire nerve (fascicles and blood vessels).
In which nerve cover layer does inflammatory infiltrate in GB syndrome collect?
Endoneurium
What neurotransmitter is made in the locus ceruleus?
Norepinephrine
Where is the locus ceruleus?
In the pons
What change is there in norepi in anxiety, and in depression?
Incr in anxiety, decr in depression
What neurotransmitter is made in the ventral tegmentum and substantia nigra pars compacta?
Dopamine
Where is the ventral tegmentum and substantia nigra pars compacta?
Midbrain
What changes are there in dopamine in 1. Huntingtons 2. Parkinsons 3. Depression?
- Huntingtons - Incr
- Parkinson’s - Decr
- Depression - decr
What neurotransmitted is made in the raphe nuclei?
5-HT aka serotonin
Where are the raphe nuclei located?
pons, medulla, and midbrain
What changes are there in 5-HT with 1. anxiety 2. depression
Decr, decr
What neurotransmitter is made in the basal nucleus of meynert?
ACh
What changes are there in Ach in 1. Parkinson’s, 2. Alzheimers 3. Huntingons
- Parkinsons - Incr
- Alz- Decr
- Huntington’s - Decr
What neurotransmitter is made in the nucleus accumbens?
GABA
What changes are there to GABA in 1. anxiety and 2. Huntington’s?
- Decr in anxiety
2. Decr in huntington’s
What three structures form the blood brain barrier?
- Tight junctions between non-fenestrated capillary endothelial cells
- basement membrane
- Astrocyte foot processes
How do glucose and amino acids cross the blood brain barrier?
slowly, by carrier-mediated transport processes
How do non-polar/lipid soluble substances cross the blood brain barrier?
Rapidly via diffusion
What characterizes the area postrema re:blood/brain barrier?
Specialized brain region with fenestrated capillaries and no blood-brain barrier; this area is responsible for vomiting, thus explains vomiting after chemo.
What is the OVLT, what characterizes it re:blood/brain barrier?
Organum vasculosum of lamina terminalis. Responsible for osmotic sensing, so also does not have intact blood-brain barrier.
Why does the neurohypophysis not have a blood brain barrier?
To allow neurosecretory products such as ADH to enter circulation.
How can the blood brain barrier be disrupted?
Infarction/neoplasm can destroy endothelial tight junctions –> vasogenic edema.
