4.7 Special Sensory

Question 1

What are the 4 types of sensory-receptor cells?

Answer 1

mechanoreceptors: movement, touch, pressure, vibration, sound waves
nociceptors: pain, tissue damage
photoreceptors: light
chemoreceptors: specific molecules

Question 2

What is somatic sensation? What forms does it take?

Answer 2

Somatic Sensation is the sensation of body surfaces, including skin, muscle and joint sensation.

Touch:
light touch, deep touch, vibration, pressure
Temperature:
heat, cold
Pain:
tissue damage, extreme heat, extreme cold, mechanical
Musculoskeletal:
muscle stretch, muscle contraction, joint position

Question 3

What does the spinothalamic pathway do?

Answer 3

SENSORY- Pain and Temperature (less: crude touch, pressure)

Question 4

What kinds of receptors are used in the spinothalamic pathway?

Answer 4

mechanoreceptors, thermoreceptors, nociceptors in skin areas

Question 5

What is the pathway for the spinothalamic tract? Where does it cross over?

Answer 5

Spinal nerve to dorsal spinal cord, crosses over (decussation) to white matter of spinal cord to thalamus  to primary somatosensory cortex

Question 6

What is nociceptive pain? what two types of fibers are involved?

Answer 6

pain due to activation of bare nerve endings (nociceptors) that sense noxious thermal, mechanical, and chemical stimuli
A-delta fibers: fast, sharp pain sensation
C-fibers: slow, dull pain

Question 7

What is neuropathy?

Answer 7

– pain due to direct damage to nerves

Question 8

What is referred pain?

Answer 8

pain in organs/viscera perceived as originating from body surface due to shared input region

Question 9

What does the medial lemniscus pathway do?

Answer 9

SENSORY- 2-point discrimination, fine touch, vibration, pressure, proprioception

Question 10

What kinds of receptors are used in the medial lemiscus pathway?

Answer 10

mechanoreceptors in skin, proprioceptors in muscles, joints

Question 11

What is the pathway of the medial lemiscus? Where does it cross over?

Answer 11

Spinal nerves, to
Doral root gangion, to
Posterior white column, to
Medulla where CROSSES OVER to medial lemiscus in brainstem, to
Thalamus, to
primary somatosensory cortex

Question 12

What are the special senses?

Answer 12

Olfactory (nose)
Gustatory (tongue)
Auditory (ear, cochlea)
Vestibular (ear, vestibule)
Visual (eye)

Question 13

What is the pathway for the olfactory system?

Answer 13

Chemicals in through air stick to olfactory mucosa, where dissolve  contact olfacotry receptors  nerves pass through cribriform plate of the ethmoid bone  CN I  nerves contact olfactory bulb (in CNS)

Question 14

Where in the CNS do olfactory signals go?

Answer 14

hypothalamus, limbic system, olfactory cortex for integration of smell recognition, memory, association.

Question 15

What anatomical structures are involved in the gustatory sense?

Answer 15

tongue/taste buds
facial nerve CN VII, glossopharyngeal nerve CN IX, vagus nerve CN X
medulla oblongata, thalamus, Gustatory Cortex

Question 16

What 3 types of taste buds are used for gustatory sensation?

Answer 16

circumvallate papilla
fungiform papilla
filiform papilla

Question 17

What is the pathway of the gustatory sense?

Answer 17

Facial Nerve (VII), Glossopharyngeal nerve (IX), and vagus nerve (X) contact the gustatory cells on the tongue 
signals from the cranial nerves travel to the CNS for integration: medulla oblongata, then to the thalamus, then to the Gustatory Cortex.

Question 18

What is the general pathway of the auditory sense?

Answer 18

Stimulus, to
CN VIII, to
Thalamus, to
Auditory cortex

Question 19

How does sound travel through outer ear to CN VIII?

Answer 19

Outer ear, to 
Middle ear, to
TM, to
Bones, to
Oval window, to
Inner ear, WHERE
Little hairs vibrate --> CN VIII

Question 20

What is the organ of corti?

Answer 20

The part of the cochlea that houses the hair cells that turn the physical movement of sound waves into electrical impulses

Question 21

What is conduction deafness? Some causes?

Answer 21

soundwaves are not properly conducted to the inner ear
cerumen impaction
tympanic membrane perforation
chronic otitis media (ear infection)
auditory tube dysfunction
otosclerosis of the ossicle joints
congenital malformation of external ear

Question 22

What is sensorineural hearing loss? Some causes?

Answer 22

neural transmission from cochlea to CNS is impaired
acoustic trauma
ototoxic drugs (certain antibiotics, aspirin, chemotherapeutic agents…)
viral infections affecting cochlea, CN VIII
basilar skull fracture
tumors

Question 23

Which auditory test is for conduction? Localization?

Answer 23

Conduction= Rinne (tuning fork in air vs mastoid)
Localization= Weber (tuning fork on top of head)

Question 24

What is tinnitus?

Answer 24

Tinnitus is the perception of sound, when no sound is present, patient will report “ringing, buzzing, or noise” in the ears
can be caused by a wide range of pressure changes in the conductive pathways, or by neural or pressure changes in the transduction pathways, lesion in any place along the pathway
can precede or be associated with hearing loss

Question 25

What is the function of the vestibular system? What anatomical structures are involved?

Answer 25

The special sense of balance and equilibrium is in the Vestibular System.
stimulus: head movement (rotation, acceleration, position) fluid movement in inner ear
receptors: hair cells in semicircular canals and otolith organs
anatomical structures:
inner ear
Vestibulocochlear Nerve (CN VIII)
dorsal pons, medulla oblongata
cerebellum
cerebral cortex (somatosensory cortex, parieto-insular vestibular cortex, periarcuate area of frontal lobe)

Question 26

What is the function of the vestibule, otolith, and semicircular canals?

Answer 26

Vestibule/otolith organs: respond to gravity and acceleration of head
Semicircular canals: respond to rotation of the head in 3 planes

Question 27

What is notable about the tonic action potentials of the vestibular system?

Answer 27

always a small amount of electrical activity (unusual).. Can lead to unusual effects.

Brain is always comparing R/L side. So, if one side changes activity level, body sends signal, then strange effect

Question 28

What is the vestibular pathway?

Answer 28

vestibular hair cells send signals along the vestibulocochlear nerve (VIII)
to the pons and medulla oblongata, then to the cerebellum, and cerebral cortex