Sensory Physiology

Question 1

Adequate Stimulus

Answer 1

Under normal circumstances a specific receptor is affected by only one stimulus modality –> adequate stimulus

Question 2

Receptor Specificity

Answer 2

Any one receptor type will normally respond to only one kind of physical stimulus

Question 3

Sensory transduction

Answer 3

process by which the energy of a physical stimulus is detected and converted into a form of energy used by the NS

Question 4

Physical stimulus is converted into a

Answer 4

receptor potential in a specialized cell or in the sensory receptor ending of the primary afferent

Question 5

Receptor potentials are

Answer 5

local, graded potentials

the size of the receptor potential is a function of the intensity of the stimulus

Question 6

If the receptor potential is a depolarization in primary afferent ending, it can cause

Answer 6

afferent to reach threshold and generate an AP

Question 7

Labeled Line Principle

Answer 7

chain of neurons from sensory receptor to higher brain areas, the line is labeled according to the physical or chemical stimulus that the receptor responds to

Question 8

Law of specific nerve endings

Answer 8

No matter where in the chain a neuron is stimulated, the sensation will be that evoked by the stimulating receptor

Question 9

Receptive field of a neuron

Answer 9

region of tissue within which a stimulus can evoke a change in the firing rate of a neuron

Question 10

Law of projection

Answer 10

If a neuron in a sensory pathway is stimulated the subject perceives the stimulus as being in the location of the sensory receptor for that pathway

Question 11

Tonic Receptor

Answer 11

good at signaling stimulus intensity but not good at signaling stimulus duration when the intensity is low

Question 12

Phasic Receptor

Answer 12

adapt very rapidly

Question 13

Tactile Sensations

Answer 13

touch or superficial touch or light touch
Pressure or deep touch
Flutter - vibration - rapid repeated touch or pressure

Question 14

How does the NS code for strength of stimulus

Answer 14

Frequency and population codes

Question 15

Frequency code

Answer 15

signal increasing stimulus strength by increasing frequency of nerve impulses

Question 16

POpulation code

Answer 16

signal increasing stimulus strength by increasing the number of fibers activated

Question 17

Adaptation

Answer 17

whan a maintained stimulus of constant strength is applied to a receptor, the frequency of the action potentials in the receptors sensory nerve decreases over time

Question 18

Non-adapting receptor

Answer 18

never completely adapt
ex = nociceptors
Often lump with slowly adapting receptors

Question 19

Slowly Adapting receptors

Answer 19

AKA tonic
Ex = merkel
useful for giving continuous into about stimulus strength and signaline not as useful for signaling stimulus duration at low intensity

Question 20

Rapidly Adapting Receptors

Answer 20

AKA phasic
Ex = meisner and pacinian
Cant give continuous signal in response to cont stimulu
Useful for signaling beginnin and end of stimulus
# of APs transmitted relates to rate at which change is taking place

Question 21

Receptors involved in tactile and vibratory sense

Answer 21

Free nerve endings - crude touch
High sensitivity (low thresh) mechanoreceptors
- merkel
- Slowly adapting afferent II 
- meissner
- pacinian
- hair end organ

Question 22

Merkel disks

Answer 22

found at base of epidermis
slowly adapting
static discrimination of shapes, edges and textures

Question 23

Meissners corpuscles

Answer 23

rapidly adapting
40% of mechanoreceptors of hand
closer to skin surface than merkel
basis for detection of slippage

Question 24

Pacinian

Answer 24

rapidly adapting
found deeply in subcutaneous tissue
sensitive to higher frequencies
Detect vibration through obkects held in hand

Question 25

Hair end organ

Answer 25

hair follicles in skin adapt rapidly detect movement of objects on body surface and initial contact of an object with the body

Question 26

Active Tactile Exploration

Answer 26

For accurate discrimination of texture, relative movement btw the skin and surface is required

Question 27

Cold thermal sensations

Answer 27

cold temperature receptors including TRPM8 receptor | cold nociceptor

Question 28

Warmth thermal sensation

Answer 28

warmth temperature receptors Hot/capsacin receptor Hot nociceptor include TRPV

Question 29

Locations of thermal receptors

Answer 29

peripheral - in or just under skin | deep body - in abdominal viscera and spinal cord

Question 30

Itch

Answer 30

independent sensory modality separate from pain | Sensed by free nerve endings of certain small unmyelinated C fibers

Question 31

Two point discrimination

Answer 31

Test of tactile acuity Good discrimination on lips and fingertips Poor on back and calf of leg High density in areas of good discrimination More cortical tissue devoted to analyzing signals from areas of good discrimination

Question 32

Proprioception

Answer 32

Sense of self important for maintaining balance Controlling limb movement Evaluating shape of a grasped object

Question 33

Types of proprioception

Answer 33

Joint position - static Joint movement - dynamic Conscious proprio - kinesthesia

Question 34

Receptors involved in proprioception

Answer 34

Joint receptors Muscle spindles and glogi tendon Skin tactile receptors (ruffini)

Question 35

Dorsal column is responsible for

Answer 35

fine tactile discriminations, two point discrimination, vibratory sense and proprioceptive sense

Question 36

Localization with dorsal column

Answer 36

precise loalization is possible because receptors have small receptive fields

Question 37

Lesion to dorsal column -->

Answer 37

Deficits in Tactile discrmination vibratory sense proprioception

Question 38

Clinical tests for dorsal column

Answer 38

``` Slightly bend patients finger or toe Romberg Test (pos if falls, pos) ```

Question 39

Dorsal column pathway

Answer 39

Goes up ipsilaterally to synapse in medulla and then 2nd one crosses --> arcuate fibers in medulla and then goes up to synapse in thalamus and then goes to somatosensory cortex

Question 40

Anterolateral System

Answer 40

Includes spinothalamic tracts Responsible for conveying nociceptive and thermal sensations Information crosses midline in the spinal cord!

Question 41

Somatosensory cortex located

Answer 41

parietal lobe primary - 3b, 3a, 1, 2 secondary - S2

Question 42

Somatotopic maps

Answer 42

foot area always in medial cortex | plasticity and reorganization

Question 43

Nerve pressure palsy

Answer 43

affected limb "falls asleep"

Question 44

Spinal root injuries

Answer 44

could cause impairment of cutaneous sensation over a dermatome Overlap of dermatomes so wont lose all sensation unless adjacent roots are impacted

Question 45

Sever one peripheral nerve

Answer 45

Sensory loss in fragments of adjacent dermatomes

Question 46

Peripheral neuropathies

Answer 46

stocking - glove pattern

Question 47

Infection of a DRG or CNG with vericalla zoster

Answer 47

chicken pox in latent form | painful eruptions fo the skin usually in one dermatome or branch of trigeminal nerve

Question 48

Hemisection of spinal cord

Answer 48

Brown sequard syndrome | both somatosensory and motor effects

Question 49

Classification of nerve fibers - myelination

Answer 49

Types I II and III are myelinated Type IV is not A and B are myelinated, C is not

Question 50

I average conduction velocity

Answer 50

100 meters per secong - A alpha

Question 51

II average conduction

Answer 51

50 meters per second A Beta

Question 52

III average conduction

Answer 52

20 meters per second A Delta

Question 53

IV average conduction

Answer 53

1 meter per second C

Question 54

Letter Classification scheme in order of dec speed of conduction

Answer 54

``` A alpha A beta A gamma A delta B C ```