Nervous system cast of characters

Question 1

What three parts are there to neurons and what parts can be seen on Nissle staining?

Answer 1

Dendrites (receive input), cell bodies, axons (send output).
Dendrites and cell bodies can be seen on Nissle. Axons have no RER.

Question 2

What is Wallerian degeneration of neurons?

Answer 2

1. Degeneration distal to axon injury
2. Axonal retraction proximally, macs come clean up debris
3. Intact nerve fiber sprouts towards remnants of neurolemma, allows for slow regeneration (PNS>CNS).

Question 3

What are the most abundant cell type in the brain?

Answer 3

Astrocytes.

Question 4

What are some of the functions of astrocytes?

Answer 4

Physical support, blood brain barrier.
Repair, reactive gliosis in response to injury.
K+ metabolism, removal of excess NTs, glycogen fuel reserve buffer.

Question 5

What is the marker of astrocytes? What are they derived from?

Answer 5

GFAP. Neuroectoderm.

Question 6

Which cells are the phagocytic scavengers of the CNS? What is their lineage?

Answer 6

Microglia. Mesodermal, of mononuclear origin.

Question 7

What are microglia activated by? What happens with HIV infection?

Answer 7

Activated by tissue damage. When infected by HIV, fuse to form giant multinucleated cells.

Question 8

Can microglia be seen on Nissle stain?

Answer 8

Not really.

Question 9

What is the purpose of the myelin sheath?

Answer 9

To increase conduction velocity of signals transmitted down axons, via saltatory conduction of action potentials at the nodes of ranvier.

Question 10

What characterizes nodes of ranvier?

Answer 10

High concentration of sodium channels.

Question 11

What cells make up myelin sheath in CNS and PNS?

Answer 11

CNS: oligodendrocytes
PNS: Schwann cells.

Question 12

What are schwann cells derived from? How are they different from oligos?

Answer 12

Derived from neural crest, each schwann myelinates only 1 PNS axon. Promote axonal regeneration.

Question 13

What is bilateral acoustic schwannomas assciated with?

Answer 13

Internal acoustic meatus schwannomas, bilateral associated with neurofibromatosis type 2.

Question 14

What do oligodendrocytes look like histoligically? What are they derived from?

Answer 14

fried egg appearance. Derived from neuroectoderm. Each oligo can myelinate up to 30 axons.

Question 15

What type of sensory receptor is responsible for pain and temperature?

Answer 15

Free nerve endings.

Question 16

What kinds of free nerve ending sensory receptors are there?

Answer 16

C - slow, unmyelinated fibers.

Adelta - fast, myelinated fibers.

Question 17

What is the location of free nerve ending sensory receptors?

Answer 17

All skin, epidermis, some viscera

Question 18

What kind of receptors are meissner corpuscles?

Answer 18

Large, myelinated fibers that adapt quickly.

Question 19

What is the location of meissner corpuscles?

Answer 19

Glabrous (hairless) skin.

Question 20

What senses are meissner corpuscles responsible for?

Answer 20

Dynamic, fine/light touch, position sense.

Question 21

What kind of receptors are pacinian corpuscles?

Answer 21

Large myelinated fibers that adapt quickly.

Question 22

Where are pacinian corpuscles located?

Answer 22

Deep skin layers, ligaments, joints.

Question 23

What senses are pacinian corpuscles responsible for?

Answer 23

Vibration, pressure.

Question 24

What kind of receptors are merkel discs?

Answer 24

Large myelinated fibers that adapt quickly.

Question 25

Where are merkel discs located?

Answer 25

finger tips, superficial skin.

Question 26

What senses are merkel discs responsible for?

Answer 26

pressure, deep static touch (eg shapes, edges), position sense.

Question 27

What kind of receptors are ruffini corpuscles?

Answer 27

Dendritic endings with capsule. Adapt slowly.

Question 28

Where are ruffini corpuscles located?

Answer 28

Finger tips, joints.

Question 29

what senses are ruffini corpuscles responsible for?

Answer 29

Pressure, slippage of objects along surface of skin, joint angle change.

Question 30

What does endoneurium contain?

Answer 30

Single nerve fiber layers.

Question 31

What does perineurium contain?

Answer 31

Surrounds a fascicle of nerve fibers.

Question 32

What does Epineurium contain?

Answer 32

Dense connective tissue that surrounds entire nerve (fascicles and blood vessels).

Question 33

In which nerve cover layer does inflammatory infiltrate in GB syndrome collect?

Answer 33

Endoneurium

Question 34

What neurotransmitter is made in the locus ceruleus?

Answer 34

Norepinephrine

Question 35

Where is the locus ceruleus?

Answer 35

In the pons

Question 36

What change is there in norepi in anxiety, and in depression?

Answer 36

Incr in anxiety, decr in depression

Question 37

What neurotransmitter is made in the ventral tegmentum and substantia nigra pars compacta?

Answer 37

Dopamine

Question 38

Where is the ventral tegmentum and substantia nigra pars compacta?

Answer 38

Midbrain

Question 39

What changes are there in dopamine in 1. Huntingtons 2. Parkinsons 3. Depression?

Answer 39

1. Huntingtons - Incr 2. Parkinson's - Decr 3. Depression - decr

Question 40

What neurotransmitted is made in the raphe nuclei?

Answer 40

5-HT aka serotonin

Question 41

Where are the raphe nuclei located?

Answer 41

pons, medulla, and midbrain

Question 42

What changes are there in 5-HT with 1. anxiety 2. depression

Answer 42

Decr, decr

Question 43

What neurotransmitter is made in the basal nucleus of meynert?

Answer 43

ACh

Question 44

What changes are there in Ach in 1. Parkinson's, 2. Alzheimers 3. Huntingons

Answer 44

1. Parkinsons - Incr 2. Alz- Decr 3. Huntington's - Decr

Question 45

What neurotransmitter is made in the nucleus accumbens?

Answer 45

GABA

Question 46

What changes are there to GABA in 1. anxiety and 2. Huntington's?

Answer 46

1. Decr in anxiety | 2. Decr in huntington's

Question 47

What three structures form the blood brain barrier?

Answer 47

1. Tight junctions between non-fenestrated capillary endothelial cells 2. basement membrane 3. Astrocyte foot processes

Question 48

How do glucose and amino acids cross the blood brain barrier?

Answer 48

slowly, by carrier-mediated transport processes

Question 49

How do non-polar/lipid soluble substances cross the blood brain barrier?

Answer 49

Rapidly via diffusion

Question 50

What characterizes the area postrema re:blood/brain barrier?

Answer 50

Specialized brain region with fenestrated capillaries and no blood-brain barrier; this area is responsible for vomiting, thus explains vomiting after chemo.

Question 51

What is the OVLT, what characterizes it re:blood/brain barrier?

Answer 51

Organum vasculosum of lamina terminalis. Responsible for osmotic sensing, so also does not have intact blood-brain barrier.

Question 52

Why does the neurohypophysis not have a blood brain barrier?

Answer 52

To allow neurosecretory products such as ADH to enter circulation.

Question 53

How can the blood brain barrier be disrupted?

Answer 53

Infarction/neoplasm can destroy endothelial tight junctions --> vasogenic edema.