sensory corpuscles, peripheral nerves, and neurotransmitters

Question 1

Free nerve endings: description, location, and senses

Answer 1

C fibers: slow, unmyelinated fibers
Adelta: fast, myelinated fibers
found in all skin, epidermis, and some viscera
mediates pain and temp

Question 2

Meissner corpuscles: description, location, and senses

Answer 2

large myelinated fibers that adapt quickly
found in glabrous (hairless) skin
sense dynamic, fine/light touch, and position sense

Question 3

Pacinian corpuscles: description, location, and senses

Answer 3

large myelinated fibers that adapt quickly
found in deep skin layers, ligaments, and joints
good at vibration and pressure

Question 4

Merkel discs: descripion, location, senses

Answer 4

large myelinated fibers that adapt slowly
found in the basal epidermal layer and hair follicles
sense pressure, deep static touch, and position sense

Question 5

What is the structure of a peripheral nerve?

Answer 5

endoneurium: single neurve fiber layers
perineurium: permeability barrier that surrounds a fascicle of nerve fibers and must be rejoined in microsurgery for limb reattachment
epineurium: dense CT that surrounds the entire nerve

Question 6

Norepinephrine: where is it synthesized and what are changes in disease?

Answer 6

made in the locus ceruleus

increased in anxiety and decr. in depression

Question 7

dopamine: where is it synthesized, and what are the changes in disease?

Answer 7

made in the ventral tegmentum and the SNc (substantia nigra compacta)
incr. in Huntington and decr. in Parkinson and depression

Question 8

Serotonin: synthesis location and disease

Answer 8

synthesized in the Raphe nucleus of the pons, medulla, and midbrain
incr. in Parkinson but decr. in anxiety and depression

Question 9

ACh: location of synthesis and change in disease

Answer 9

made in the basal nucleus of Meynert

incr. in PD, decr. in Alzheimer and Huntingtons

Question 10

GABA: location of synthesis and change in disease

Answer 10

made in the nucleus accumbens. nucleus accumbens also important for reward, pleasure, addiction, and fear.
decr. in anxiety and in huntington disease.

Question 11

What structures form the blood brain barrier?

Answer 11

tight junctions btw the nonfenestrated capillary endothelial cells, a tight basement membrane, and astrocyte foot processes

Question 12

How do glucose, amino acids, and lipid soluable products cross the BBB?

Answer 12

glucose and aa cross slowly via carrier-mediated transport

lipid soluable substances cross rapidly via diffusion

Question 13

What are areas of the brain withOUT a BBB? What makes them unique?

Answer 13

unique bc of fenestrated capillaries
example: area postrema, which causes vomiting after chemo; OVLT, which is a circumventricular organ that is important for osmotic sensing.
pineal gland (secretes melatonin)
The neurohypophysis also has no BBB- it is open to allow neurosecretory products to enter circulation

Question 14

What are other areas of the body with high notable barriers?

Answer 14

blood-testis barrier and maternal fetal blood barrier of the placenta.

Question 15

How can infarction or neoplasm change the BBB?

Answer 15

infarction and neoplasm destroys the endothelial tight junctions and causes vasogenic edema.