Sensory system

Question 1

List the 5 types of sensory receptors

Answer 1

Touch
Pressure
Temperature
Vibration
Proprioception

Question 2

What is a sensory receptor?

Answer 2

transducers
convert energy to action potentials
in a sensory neuron

Question 3

What is a sensory organ

Answer 3

A sensory receptor
associated with nonneuronal cells

Question 4

What is a Nociceptor?

Answer 4

Cutaneous free nerve endings
respond to stimuli
which are harmful or painful or extremes of temperature

Question 5

List 4 types of nociceptors and sensation

Answer 5

Mechanical - strong pressure
Thermal - Extreme temperature
Chemical - Bradykinin, Histamine, Acids, Irritants, Prostaglandins
Polymodal - Combination

Question 6

What are thermoreceptors?

Answer 6

skin
sensitive to the heat and cold

Question 7

The nerve fiber associated with warmth receptors and Cold receptors:

Answer 7

warmth: C fibers
Cold: A Delta and C fibers

Question 8

threshold for activation of warmth and cold receptors

Answer 8

warmth: 30C
cold: below 4C (inactive by 40C)

Question 9

What is sensory coding?

Answer 9

converting a stimulus to a recognizable sensation

Question 10

4 aspects of sensory coding

Answer 10

Sensory modality, intensity, location, and duration of the stimulus

Question 11

What is modality in sensory coding?

Answer 11

type of energy transmitted
high threshold for other forms of stimuli

Question 12

What is localization in sensory coding?

Answer 12

the site of the body from which the stimuli originate
based on the receptive field - spatial distribution from which a stimulus produces a peripheral impulse.
conscious sensation produced is always referred to the location of the receptor, even if we stimulate anywhere along this pathway

Question 13

Intensity in sensory coding

Answer 13

Amplitude of the Action potential generated
greater stimulus = greater potential amplitude = more amplitude frequency

Question 14

in signal intensity,
what is spatial summation and temporal summation?

Answer 14

Spatial Summation = Number of fibers stimulated
Temporal Summation = Frequency of action potential in each fiber (Signal strength and frequency of the AP)

Question 15

What is Duration in sensory coding?

Answer 15

time from start to end of the response in stimulus

Question 16

What is receptor adaptation?

Answer 16

Prolonged, constant stimulus decreases AP frequency over time.

Question 17

What is the response of receptors in adaptation/ desensitization?

Answer 17

1. Rapidly adapting (Pacinian and Meissner’s) = the frequency of action potentials decrease over
2. Slowly adapting (Pain) = impulses transmitted as long as the stimulus is present (awareness about the surroundings)

Question 18

What is the law of specific nerve endings?

Answer 18

sensation evoked for the receptor is specialized
regardless of modality and localization

Question 19

Law of projection (e.g Phantom Limb)

Answer 19

when a particular sensory pathway is stimulated
along its course from the receptor to the sensory cortex
conscious sensation is referred to the site of receptors

Question 20

2 point threshold test

Answer 20

Tactile activity varies with parts of the body, tests integrity of Dorsal column/ Medial lemnisci

Question 21

What is Pallesthesia?
tested by?

Answer 21

Vibratory sensibility
128Hz tuning fork on fingertips/bones

Question 22

Degeneration of Pacinian corpuscles, dorsal columns

Answer 22

in
Poorly controlled diabetes mellitus
Pernicious anemia/ B12 deficiency
Tabes dorsalis

decreased vibratory sense

Question 23

What is Stereognosis

Answer 23

Identifying objects by touch

Intact dorsal column and primary sensory cortex and somattesthetic association cortex is needed.