structure and function of somatosensory system

Question 1

Ascending tracts

Answer 1

Carry info from pain, thermal, tactile, muscle and joint receptors to the cerebral cortex or cerebellum and brainstem

Question 2

Is cerebral cortex unconscious or conscious

Answer 2

CONSCIOUS

Question 3

Is cerebellym and brainstem conscious or unconscious

Answer 3

unconscious

Question 4

2 tracts that conscious level info travels in

Answer 4

1. dorsal column

2. anterolateral system tracts

Question 5

Endings of Peripheral receptors - DORSAL COLUMN

Answer 5

Unencapsulated/free nerve endings

Modified/encapsulated endings

Proprioceptors

Question 6

Free nerve endings of peripheral receptors

Answer 6

pain, temp, pressure

Merkels disk, hair follices, nociceptors

Question 7

Modified/encapsulated endings of peripheral receptors

Answer 7

Pressure, touch, vibration, stretch, pain

Pacinian corpusles

Question 8

Proprioreceptors - endings of peripheral receptors

Answer 8

Stretch, pressure, pain

Muscle spindles, golgi tendon organs

Question 9

What makes up the dorsal column POSTERIOR

Answer 9

Gracile fasiculus MORE CENTRAL (lower limb

Question 10

dorsal column Ascending tract ? first and secondary neurones

Answer 10

First order neurones synapse at gracile and cuneate

Syanpse on second order neurone in the medulla oblongata of the brain stem , CROSS OVER ( contralateral) as internal acuate fibers and ascend through brainstem as the medial leminus to the thyalamus

Question 11

Thalamus

Answer 11

Located EITHER SIDE of the 3rd ventricle
Receive info via second order neurones
Integrates, modulates and relays info
Multiple nuceli

Question 12

dorsal column 3rd order neurones

Answer 12

Syanpse in thalamus- at ventral posterior lateral nucelus – sensory motor cortex, travel via the posterior limb of internal capsule ( white matter tract)

Question 13

Thalamus

Answer 13

Located EITHER SIDE of the 3rd ventricle
Receive info via second order neurones
Integrates, modulates and relays info
Multiple nuclei

Question 14

Anterolateral system tract

Answer 14

SPINOTHALAMIC
ascending - sensory
Pain, temperature, light touch and pressure

Question 15

Polymodal nociceptors (pain)
ANTEROLATERAL

Answer 15

Respond to many different stimuli ( including tissue damage)
C fibre afferents- slow pain

Question 16

Mechanical nociceptors (pain)
ANTERIOLATERAL

Answer 16

Activated by high pressure, fast conducting A fibers - sharp pain

Question 17

thermal (pain) nociceptors

Answer 17

Extreme heat and cold

Question 18

2 classes of nociceptive fibers ( anterolateral ascending tract)

Answer 18

A delta fibers

C fibers

Question 19

A delta fibers

Answer 19

Small diameter, myelinated
Nociceptive specific- thermal or mechanical
Fast, sharp, well localised pain

Question 20

C fibers

Answer 20

Non myleinated
Nociceptive specific or polymodal
Dull, aching, burning pain

Question 21

A delta fibers

Answer 21

Small diameter, myelinated
Nociceptive specific- thermal or mechanical
Fast, sharp, well localized pain

Question 22

2 parts of the spinothalmic tracts

Answer 22

Direct tracts

Indirect tracts

Question 23

Direct tracts

Answer 23

Lateral spinothalmic tract - pain and temp

Anterior spinothalamic tract- crude touch and pressure

Question 24

Direct tracts

Answer 24

Lateral spinothalmic tract - pain and temp

Anterior spinothalamic tract- crude touch and pressure

Question 25

Indirect tracts

Answer 25

Spinothalamic Modulate pain and can terminate in other brain regions Spinorectular tract- reticular formation = CORTEX Spinocerebellar tract- cereballar peduncles= CEREBELLUM Spinotectal tract= orientates eyes and head towards stimulus

Question 26

Anterolateral system | Neurones

Answer 26

Axons from dorsal root ganglion enter and ascend/descend a few levels before synapsing in the SUBSTANTIA GELATINOSA Second order neurones form the reflex arc or immediately decussate and ascend in spinothalamic tract THROUHG BRAINSTEM Distinct tract alongside medial lemniscus Synapses in the VPL of the hypothalamus

Question 27

Spinorecticular tract

Answer 27

Send projections into reticular formations of brainstem DULL ACHING PAIN Alertness and arousal response to pain from reticular system then to thalamus and cerebral cortex

Question 28

First second third order neurones anterolateral pressure pain and temp

Answer 28

first = posterior root ganglion second =substantia gelatinosa third = ventral posterlateral nucleus of thalamus destination to posterior central gyrus

Question 29

Spinocerebellar tract

Answer 29

Anterolateral Second order neurones from spinal cord that go straight to the cerebellum to help integrate info about pain into the whole system

Question 30

Sensory inputs - HEAD pathway

Answer 30

Somatic sensation of face = trigeminal nerves , trigeminal ganglion facial, glossopharyngeal and vagus cranial nerves Synapse onto second order neurones in the ipsilateral trigeminal nucelus Axons descussate and project in the trigeminal lemniscus to the ventral posterior medial ( vpm) nucleus of the thalamus Fibers project to the sensory cortex ( parietal lobe)

Question 31

Trigeminal nerve nuceli - SENSORY NUCELI

Answer 31

Principle sensory nucleus - touch, pressure and conscious proprioception Spinal nucleus- pain and termperature Mesencephalic nucleus- non conscious proprioceptive info

Question 32

Motor nucleus- trigemial nerve nuceli

Answer 32

Innervates muscles of mastication

Question 33

Motor nucleus- trigemial nerve nuclei

Answer 33

Innervates muscles of mastication

Question 34

SENSORY from upper face, orbit and eye

Answer 34

Opthalmic

Question 35

Sensory from mid face, upper teeth

Answer 35

Maxillary

Question 36

Sensory from lower face, lower teeth

Answer 36

Mandibular

Question 37

Pain and temperature from face

Answer 37

Spinal nucelus

Question 38

Discriminative touch from face

Answer 38

Principle sensor nucleus

Question 39

Prioprioception from muscles of mastication - sensory from lower face, lower teeth

Answer 39

Mesencephalic nucelus

Question 40

Motor to muscles of mastication

Answer 40

Motor nucelus

Question 41

Homunclus ?

Answer 41

The cortical homunculus represents the importance of various parts of your body as seen by your brain Distribution on cerebral cortex

Question 42

PAIN

Answer 42

Detected by primary nociceptors pain afferent Signal relayed through anterolateral tract Input via thalamus- modulating, integrating

Question 43

Modulating perception of pain ASCENDING

Answer 43

Achieved by presynaptic inhibition | from touch or proprioceptive afferent - inhbit transmission of pain info through the spinal thalamic pathway

Question 44

Descending regulation of pain

Answer 44

Neurones from periventricular and periaqueductal grey matter project to the Raphe nuclei Medullary neurones project to dorsal horns Depress activity of nociceptive neurones