Lecture 18

Question 1

Mechanosensitive ion channels convert….

Answer 1

mechanical force into change of ionic current

Question 2

Mechanical stimuli may trigger release of….

Answer 2

second messengers

Question 3

Two-point discrimination varies at least _____ across the body

Answer 3

twenty fold

Question 4

Two-point discrimination:
Higher density of mechanoreceptors
Enriched in receptor types that have small receptive fields
More brain tissue
Maybe special neural mechanisms for high-resolution discriminations

Answer 4

Fingertip for braille reading

Question 5

Primary afferent axons enter the spinal cord through the ___ _____; their cell bodies lie in the…..

Answer 5

dorsal root;
dorsal root ganglia

Question 6

Types of primary afferent axons and their groups, ordered in size from largest to smallest and fastest to slowest

Answer 6

A(alpha); Group I
A(beta); Group II
A(delta); Group III
C; Group IV

Question 7

C fibers (3)

Answer 7

Mediate pain, temperature, and itch.

Have no myelin and are about 1 μm in diameter.

The slowest axons, conducting at about 0.5–1 m/sec

Question 8

A(beta) mediates….

Answer 8

touch sensations

Question 9

Each spinal segment is named after the….

Answer 9

vertebra adjacent to where the nerves originate

Question 10

How many spinal segments are there, divided into ___ divisions of spinal cord?

Answer 10

30, 4 divisions of spinal cord

Question 11

Four spinal segments and their numbers (top to bottom)
Cervical (C)
Thoracic (T)
Lumbar (L)
Sacral (S)

Answer 11

Cervical (C) 1–8, thoracic (T) 1–12, lumbar (L) 1–5, and sacral (S) 1–5

Question 12

Dermatomes:

Answer 12

the area of skin innervated by the right and left dorsal roots of a single spinal segment

Question 13

Dermatomes-
___ to ___ correspondence with spinal segments

Answer 13

one to one

Question 14

Shingles

Answer 14

A type of herpes virus commonly known as chickenpox
The virus remains in our primary sensory neurons and revives
Restricted to the skin innervated by the axons of the affected dorsal root.

Question 15

Aβ axons have 2 branches: on _____-order sensory neurons, rapid _____ _____; ascending input is responsible for ______

Answer 15

second-order;
unconscious reflexes;
perception

Question 16

Dorsal column–medial lemniscal pathway (copy down)

Answer 16

The ascending branch of the large sensory axons (Aβ) enters the ipsilateral dorsal column of the spinal cord,
The axons of the dorsal column terminate in the dorsal column nuclei, at the junction of the spinal cord and medulla. some of the longest axons
From this point onward, decussate to ventral posterior (VP) nucleus of the thalamus, and primary somatosensory cortex, or S1

Question 17

Adjacent somatic sensory areas: (2)

Answer 17

Postcentral gyrus: 3a, 1, 2
Posterior parietal cortex: areas 5, 7

Question 18

Primary somatosensory cortex (S1)= Brodmann’s area __ lies on the _____ ______

Answer 18

Brodmann’s area 3b;
postcentral gyrus

Question 19

Area 3b is the primary somatic sensory cortex because: (4)

Answer 19

1) It receives dense inputs from the VP nucleus
2) Very responsive to somatosensory stimuli
3) Lesions here impair somatic sensation
4) Electrically stimulated, it evokes somatic sensory experiences

Question 20

3b projection to area 1 sends _____ _____, 3b projection to area 2 emphasizes _____ and ______

Answer 20

texture information;
size and shape

Question 21

Wilder Penfield:

Answer 21

Electrical stimulation of the S1 surface can map somatic sensations localized across the body

Question 22

Somatotopy:

Answer 22

mapping of the body’s surface sensations onto the brain

Question 23

Cortical somatotopy guy is named…

Answer 23

Homunculus

Question 24

Somatotopic maps are ____, they can change with things like _____ and ______

Answer 24

dynamic;
amputation and overstimulation

Question 25

sensory signals from each vibrissa follicle go to one clearly defined cluster of S1 neurons

Answer 25

Barrel cortex in mice

Question 26

S1 neurons with similar inputs and responses are stacked ______ into _____ extend across cortical layers

Answer 26

vertically into columns

Question 27

Thalamic inputs to S1 terminate mainly in layer ____

Answer 27

IV