6

Question 1

CLASSIFICATION OF SOMATIC SENSES

Answer 1

According to Mode of stimulus
(1) The mechanoreceptive somatic senses
(2) The thermoreceptive senses
(3) The pain sense

According to the site of the receptors
1-Superficial sensations: From the surface of the body: as pain, touch &
temperature sensations.
2-Deep (Proprioceptive) sensations: Sense of position and movements of joints , pressure
sensation , tension, vibration & deep pain.
3-Visceral sensation (from the viscera): As visceral pain , sense of micturition and defecation.

According to pathway
1- Spino-thalamic sensations: Pain, temperature in lateral spino-thalamic cortex tract. Crude touch in ventral spino-thalamic
tract.
2- Dorsal column sensations:

Question 2

Temperature sensation

Receptors

Answer 2

Receptors (They are free nerve ending): p

a) Cold receptors.     b) Warm receptors.
c) Cold pain and hot pain receptors.

Question 3

Mechanism of stimulation of thermo-receptors:

Answer 3

They are stimulated chemically as a result of
changes in the concentration of metabolites in the
receptors.

Question 4

The major sensory tracts involve chains of neurons

Answer 4

First-order neuron

Question 5

Pathway of Thermal Sensations

Answer 5

First order neuron A delta & c fibers of cells in
dorsal root ganglion (DRG). end on the cells of
S.G.R in the posterior horn

Second order neuron: It arises from S.G.R.
crosses the midline in front of the central canal
and ascend in the opposite side of the spinal cord
as Lateral spinothalamic tract to reach the
PVNT.
Third order neuron : Neuron arise from PVNT
ascend in the posterior limb of the internal capsule to reach the sensory area of the cerebral
cortex

Question 6

Tactile Receptors Site, Types?

Answer 6

in the skin and subcutaneous tissue
Types -Free nerve endings -
- -Hair end organs: around roots of hairs.
-Pacinian corpuscles.

- merkel
Meissnes

Question 7

Crude touch Receptors

Answer 7

Receptors
Free nerve endings
Hair end organs

Question 8

Pathway of crude touch

Answer 8

Pathway of crude touch

Question 9

Fine touch
Type

Answer 9

Tactile localization:
Tactile discrimination C)Stereognosis

Question 10

Threshold distance of two point discrimination:
It is short about 2 mm in distal parts of fingers & long
about 4 cm in the back because the tips of fingers
show: in

Answer 10

1- more number of receptors. 2- more number of afferent from the area. 3- more area of representation in the c. cortex. 4- less convergence along the pathway

Question 11

Pathway of Fine touch

Answer 11

First order neuron First order neuron A-beta of cells in the DRG
fibers O
enter the spinal cord to arise in dorsal column
system (Gracile tract from lower limbs and cuneate
Iii
jade
no
own
tract from upper limbs)
m train
stems
I

Question 12

Deep sensations Their pathway is similar to that of fine touch. They include:

Answer 12

1- Pressure sense. 2- Tension sense. 3- Vibration sense.
4- Sense of position.
5- Sense of movement.

Question 13

Types of receptors: of deep

Answer 13

Slow : muscle spindle, golgi tendon, spray endings
Rapid : pacinian corpuscles 30-800

2-80 meissner’s corpuscles

Question 14

Important of deep sensations?

Answer 14

Co ordination movement ,, in loss of pro prioceptive sensory ataxia

Question 15

Coding of sensory information The brain must detect three things about
each sensation:
.

Answer 15

1. Modality (type) of sensation. muller’s
2. Locality (Site) of sensation. Specific projection
3. Intensity of sensation.: Detected by Weber Fechner low

Question 16

TICKLE AND ITCH

Answer 16

These sensations are transmitted by very
small type C, unmyelinated fibers similar to those that transmit the aching, slow type of pain.

Question 17

Position Senses Receptors

Answer 17

Muscle spindles, pacinian corpuscles, ruffinis

Question 18

Position Senses Types

Answer 18

1) static position sense, which means conscious perception of the orientation of the different parts of the body with respect to one another, 2) Rate of movement sense, also called kinesthesia or dynamic proprioception.

Question 19

Detection of Vibration

Answer 19

Vibration
Pacinian corpuscles can detect signal vibrations from 30 to 800 cycles per second