General senses

Question 1

Sensory receptors

Answer 1

• adaptation: magnitude of response decreases over time in response to continuous stimulus
• perception: remaining aware of sensation over time and interpreting what that sensation means in larger context

Question 2

General senses

Answer 2

Microscopic receptors widely distributed in the skin, mucosa, connective tissues, mm, tendons, joints, and viscera
- somatic and visceral senses

Question 3

Special senses

Answer 3

Localized receptors for

• smell
• taste
• vision
• hearing/equilibrium

Question 4

Stimulation of the sensory receptor

Answer 4

Selectivity: a given receptor responds vigorously to one particular kind of stimulus (weakly or not at all to other stimuli) in its receptive field

Question 5

Transduction of the stimulus

Answer 5

Converts energy in stimulus into graded potential

Question 6

Generation of nerve impulses

Answer 6

Graded potential reaches threshold and triggers propagation toward CNS

Question 7

Integration of sensory input

Answer 7

Regions of CNS and post central gyrus receive and integrate impulses

Question 8

Classification of receptors

Answer 8

1. Location
   - exteroceptors - visceroceptors (interceptors) - proprioceptors
2. Stimulus
   - mechanoreceptors - chemoreceptors - thermoreceptors - nociceptors - photoreceptors - osmoreceptors
3. Structure
   - free nerve endings - encapsulated nerve endings

Question 9

Exteroceptors

Answer 9

• located on or very near the body surface
• respond most frequently to stimuli that arise external to the body itself
• sometimes called cutaneous receptors (detect pressure, touch, pain, and temperature)

Question 10

Visceroeptors (interoceptors)

Answer 10

Located internally

• primarily in blood vessels and viscera
• provide info regarding internal environment (usually not consciously perceived, if stimuli is strong may be perceived as pain or pressure)
• activated by pressure, stretching, and chemical changes
• involved in mediating sensations such as hunger, thirst, BP, full bladder

Question 11

Proprioceptors

Answer 11

1. Special type of visceroceptor
   - less numerous and more specialized than other visceroceptors
2. Located in skeletal mm, joint capsules, and tendons
3. Provide information regarding
   - body movement
   - orientation in space
   - mm stretch

Two types:

1. Tonic: provides information while the body is at rest, non-adapting
2. Phasic: provides information during movement. Rapidly adapting and triggered only when there is a change in position

Question 12

Mechanoreceptors

Answer 12

• detect mechanical stimuli that deform or change position of the receptor
• ex: pressure to skin, blood vessels, that results in stretch or pressure in mm, tendon, or lung tissue

Question 13

Chemoreceptors

Answer 13

• detect chemicals in the mouth, nose, and body fluids
• activated by either the amount or the changing concentration of certain chemicals
• ex: sense of taste, smell, pH homeostasis

Question 14

Thermoreceptors

Answer 14

Activated by changes in temperature

Question 15

Nociceptors

Answer 15

1. activated by intense stimulu that could result in tissue damage
   - chemical
   - intense light
   - sound
   - pressure
   - heat
2. The sensation produced is pain

Question 16

Photoreceptors

Answer 16

• found only in the eyes

- detect light that strikes the retina

Question 17

Osmoreceptors

Answer 17

• concentrated in the hypothalamus
• sense levels of osmotic pressure in body fluids
• activated by changes in concentration of electrolytes in extracellular fluids
• stimulate the hypothalamic thirst center

Question 18

Free nerve endings

Answer 18

• bare dendrites
• the simplest, most common, and most widely distributed sensory receptors
• include both exteroceptors and interoceptors

Question 19

Encapsulated nerve endings

Answer 19

have some type of connective tissue capsule that surrounds the terminal end or dendritic end

• usually mechanoreceptors (activated by mechanical or deforming stimulus)
• major types:
  
  1. Tactile/meissners corpuscle
  2. Lamellar/pacinian corpuscle
  3. Bulbous/ruffini cells
  4. Bulboid/Krause corpuscle

Question 20

Pic

Answer 20

Pic

Question 21

Sense of pain

Answer 21

Nociceptors-FREE nerve endings

• primary sensory receptors for pain
• 2 types: acute/fast pain and chronic/slow pain

Question 22

Pain A delta fibers

Answer 22

• concentrated in the skin, mucous membranes, and other superficial areas
• sharp, intense, localized fast/somatic pain
• “fast pain” travels over myelinated fibers (250 ft/sec)
• associated with superficial injury or trauma

Question 23

Pain C delta fibers

Answer 23

• originates in deeper/visceral regions (thoracic and abdominal regions)
• intense or less sever, but persistent, dull aching pain
• develops more slowly over time
• “slow pain” travels over unmyelinated fibers (3.5 ft/sec)

Question 24

Sense of temperature

Answer 24

1. FREE nerve endings
   - mediate sense of heat and cold
   - called thermoreceptors
2. Warm receptors
   - located in dermis
   - activated in temperature range of 77-114 degree F
   - >118 degrees = burning
3. Cold receptors
   - located in deepest layer of epidermis
   - activated in temperature range of 50-104 degrees F
   - <50 dramatic decrease in firing rate but activates nociceptors (freezing pain)

Question 25

Sense of touch

Answer 25

1. Types of touch sensations - skin movement - itch - tickles - light touch - deep touch 2. Free and encapsulated endings

Question 26

Touch-skin movement

Answer 26

Root hair plexuses - FREE nerve endings - activated with very slight movement on or in the skin - bends or deforms a hair follicle or shaft

Question 27

Touch - Itch

Answer 27

Free nerve endings - activated by chemical irritation - inflammatory chemicals (bradykinin or histamine)

Question 28

Touch - Tickle

Answer 28

Free nerve endings - activated by touch from an outside source - involves both thalamus and cerebellum before reaching the cerebral cortex

Question 29

Light/discriminative touch

Answer 29

Mediated by a variation of a FREE nerve ending - tactile or nerves disk: transmits compression of the outer layer of skin to the tactile disk neuron (mechanoreceptors) - detects discriminative touch and surface form and contours

Question 30

Deep touch

Answer 30

Encapsulated nerve endings 1. tactile/meissner corpuscles - enmeshed in connective tissue - located close to the dermal papillae in hairless skin areas like fingertips, lips, nipples, and genitals 2. Mediate light touch, textural sensations, and low frequency vibration

Question 31

Anatomical variants of meissner corpuscles

Answer 31

1. Bulboid/Krause corpuscle - more numerous in mucous membranes 2. Bulbous/ruffini corpuscle - crude, heavy, and persistnat touch 3. Lamellar/Pacini corpuscles - deep pressure, high frequency vibration, and stretch

Question 32

Sense of proprioception

Answer 32

- tells us level of contraction and stretch in each of our skeletal muscles - proprioceptors (muscle spindles and Golgi tendon receptors)

Question 33

Muscle spindles

Answer 33

Encapsulated nerve endings - discrete grouping of 5-10 modified mm fibers called intrafusal fibers surrounded by sensory nerve fibers - respond to mm stretch (stretch reflex and subconscious postural adjustments)

Question 34

Golgi tendon organ

Answer 34

Encapsulated nerve endings - located at the junction between mm tissue and tendon - stimulated by excessive stretch of a tendon (when pulling too great a load for the muscles to bear—tension) - protects mm from tearing