Mod 3

Question 1

Ascending sensory pathways

Answer 1

Spinothalamic (ALS)
DCML
Spinocerebellar

Question 2

Anterior and posterior spinocerebellar pathways

Answer 2

Carry subconscious proprioception
- receptors of muscles, joints, tendons, and skin
- ipsilateral trunk and lower extremity
First order neuron: carries signals from receptor to dorsal horn
- cell body in dorsal root ganglia
Second order neuron: carries signals from the dorsal horn to the cerebellum
- cell body in the dorsal horn

Question 3

Anatomy of the thalamus

Answer 3

Relay signals to the ipsilateral cerebral cortex
- specific relay nuclei
- sensory relay nuclei
- motor relay nuclei
- association nuclei
- nonspecific nuclei

Question 4

Vascular supply of the thalamus

Answer 4

Posterior cerebral artery
Anterior choroidal artery

Question 5

Function of the ALS

Answer 5

Carry sensory signals to the cerebral cortex
Neurons travel by the direct or indirect path.
Direct path carries pain, temperature, and crude touch to the thalamus.
Indirect path carries pain to others structures before they reach the thalamus.
- reticular formation
- hypothalamus
- superior colliculus
- brainstem

Question 6

Neurons of ALS

Answer 6

First order: receptor to dorsal horn
Second order: dorsal horn to thalamus
Third order: thalamus to cerebral cortex

Question 7

Indirect path of ALS

Answer 7

Reticular system: alerts patient to injury, elicits response –> evade injury
Mesencephalon: modulates pain reception
- transmits to the amygdala, emotional component of pain
Superior colliculus: turn head/eyes toward pain stimulus
Hypothalamus: autonomic response
- increases heart rate
- endocrine release of stress hormones

Question 8

DCML

Answer 8

In posterior funiculus
Fine touch, vibration, and proprioception
Fasciulus gracillis - on either side of midline carrying signals to LE
Fasciculus cuneatus - lateral to FG carrying UE signals

Question 9

Neurons of DCML

Answer 9

First order: receptor to medulla
Second order: dorsal horn to thalamus
Third order: thalamus to cerebral cortex

Question 10

Specificity theory

Answer 10

Proposed that the somatosensory system could be divided according to specific receptors for tactile, hot, cold, and pain

Question 11

Pattern theory

Answer 11

Suggested that in addition to the type of input (fibers, pathways, or anatomic structures), the pattern of impulses in the nervous system modulates pain perception

Question 12

Gate control theory

Answer 12

Endogenous pain modulatory mechanisms could enhance or reduce perception

Question 13

Diffuse noxious inhibitory controls

Answer 13

Observation that a localized nociceptive stimulation can produce a diffuse analgesic effect over the rest of the body, an analgesic approach known as counter-irritation.

Question 14

Path of light

Answer 14

Cornea
Anterior chamber
Pupil
Lens
Vitreous humor
Retina

Question 15

Neurons of the eyeball

Answer 15

Photoreceptors: light energy transduced to electrical energy
First order: bipolar cells
Second order: ganglion cells which form the optic nerve
Third order: in the thalamus which sends projections to the visual cortex

Question 16

Light stimulates a sensory signal which travels the following path

Answer 16

Optic nerve
Optic chiasm
Optic tract
LGN of the thalamus
Optic radiations
Visual cortex

Question 17

Secondary: subconscious vision

Answer 17

1. superior colliculus: saccadic eye movement
2. pretectal area: autonomic reflexes
3. hypothalamus: circadian rhythms
4. reticular formation: arousal/vision

Question 18

PLR: Constriction

Answer 18

Afferent: CN II
Efferent: CN III

1. light –> optic nerve/optic tract
2. pretectal midbrain —> bilateral EW nucleus
3. bilateral ciliary ganglia –> constrictor muscles

Question 19

PLR: Dilation

Answer 19

1. hypothalamus
2. spinal cord
3. superior cervical ganglia
4. internal carotid artery plexus
5. dilator muscles

Question 20

Convergence accommodation reflex

Answer 20

Light –> optic nerve –> optic tract –> visual cortex –> bilateral midbrain

1. Convergence: CN III to medial rectus
2. Accommodation: CN III to ciliary muscles
3. Constriction: CN III to pupillary sphincter

Question 21

Corneal blink reflex

Answer 21

Afferent: CN V1 (unilateral)
Efferent: CN VII (bilateral)

Question 22

Pathway of sound

Answer 22

Sound waves create oscillations
- external auditory canal
- tympanic membrane
- ossicles vibrate, pusing on the structures of the inner ear
- oval window
- scala vestibuli
- scala tympani
- round window

Question 23

Chochlea

Answer 23

The cochlear duct is between the scala vestibuli and the scala tympani.
It contains the receptors for transducing fluid wavs into electrical signals.

Question 24

Ascending auditory pathway

Answer 24

the auditory pathway travels along CN VIII to immediately become a bilateral signal which goes to the thalamus then the auditory cortical areas.

Question 25

Vestibular system

Answer 25

The bony labyrinth contains the organs of the vestibular system
Two sets of vestibular organs:
- semicircular canals
- otolith organs

Question 26

Semicircular canals

Answer 26

As the head moves, the fluid inside the canals moves, pushing on the ampulla of the canal.

Question 27

Otolith organs

Answer 27

In the vestibule
- saccule
- utricle
Function: respond to linear movement

Question 28

Receptors of the otolith organs

Answer 28

Hair cells embedded in a gelatinous membrane. Movement causes hair cells to bend, depolarizing sensory neurons.
Otoliths sit on top of the membrane, causing the membrane to move in response to gravity.

Question 29

Afferent projections to the vestibular nuclear complex

Answer 29

Vestibular nerve
Cerebellar nuclei
Contralateral vestibular nucleus
Spinal cord (spinovestibular fibers)
Pretectal nuclei (eye movement coordination)

Question 30

Efferent projections to the vestibular nuclear complex

Answer 30

Motor nuclei of CN III, IV, VI: extraocular movements and eye reflexes
Cerebellum: integrates sensory movement and coordinates movement
Reticular formation: reflex motor activity
Spinal cord: postural adjustments
Vestibular labyrinth: modulate the afferent signals