SENSORY SYSTEMS, SPINAL CORD AND BRAIN STEM

Question 1

in the CNS where do we find cell bodies and axons?

Answer 1

cell bodies in grey matter

axons in white matter

Question 2

in the PNS where do we find cell bodies and axons?

Answer 2

cell bodies in ganglia

axons in nerves

Question 3

what are the 4 main types of sensation?

Answer 3

superficial, deep, visceral and special

Question 4

what is superficial sensation?

Answer 4

crude touch, pain, temperature and 2 point discriminative touch

Question 5

what is deep sensation?

Answer 5

muscle and joint position sense and deep muscle pain

Question 6

what is visceral sensation?

Answer 6

sensations arising from the viscera: hunger, nausea, visceral pain

Question 7

what is special sensation?

Answer 7

senses: smell, vision, hearing, taste and balance

Question 8

where does the length of the spinal cord run from and too?

Answer 8

from the foramen magnum until L1/L2

Question 9

what are the 2 vertebral enlargements? why do we have them?

Answer 9

cervical and lumbar

due to an increased number of nerves coming out of these locations

Question 10

describe the layers of the meninges?

Answer 10

spinal cord surrounded by Pia matter which is surrounded by the subarachnoid space and arachnoid matter which is surrounded by the dura matter which is surrounded by the epidural space and this is finally surrounded by the vertebral canal.

Question 11

where do we find the cerebral spinal fluid?

what is its function?

Answer 11

in the sub-arachnoid space

to cushion the brain and spinal cord from trauma, to supply them with nutrients and to remove waste

Question 12

what is the lumbar cistern?

Answer 12

the sub-arachnoid space in the low lumbar spinal canal

Question 13

why are lumbar punctures done below L1/L2

Answer 13

as the spinal cord has ended so you can gather CSF without damaging the spinal cord

Question 14

what is the conus medullaris?

Answer 14

the tapered lowers end of the spinal cord at L1/L2

Question 15

what is the film terminali?

Answer 15

delicate strand of fibrous tissue in length, proceeding downward from the apex of the conus medullaris. it anchors the spinal cord at S2

Question 16

what is the cauda equine?

Answer 16

the sack of nerve roots at the lower end of the spinal cord.

Question 17

what is the central canal in the centre of grey matter?

Answer 17

the cerebrospinal fluid-filled space that runs through the spinal cord.

Question 18

what are the lateral horns of the spinal cord?

Answer 18

small lateral projections of grey matter located between the dorsal and ventral horns that contain the neuronal cell bodies of the sympathetic nervous system

Question 19

what is the ventral median fissure of the spinal cord?

Answer 19

the gap in the white matter between the right and left sides

Question 20

what are the dorsal median septum and sulcus?

Answer 20

a dent and a septum at the back of the spinal cord that runs between the right and left sides

Question 21

what is the ventral white commissure?

Answer 21

a collection of nerve fibers that cross the midline of the spinal cord and transmit information from or to the contralateral side of the brain. It is present throughout the length of the spinal cord and lies behind the ventral median fissure

Question 22

describe how the white matter is divided into columns?

Answer 22

we have dorsal, ventral and lateral columns.

they all contain axon tracts related to a specific function.

Question 23

what are the dorsal columns of the spinal cord?

Answer 23

they contain ascending sensory pathways that carry information about tactile sensations and proprioception

Question 24

what do ventral columns of the spinal cord carry?

Answer 24

carry both ascending information about pain and temperature, and descending motor information.

Question 25

what are lateral columns of the spinal cord?

Answer 25

travel from the cerebral cortex to contact spinal motor neurons.

Question 26

what are funiculi?

Answer 26

bundles of axons within white matter of the spinal cord

Question 27

what does ipsilateral mean? | what does contralateral mean?

Answer 27

ipsilateral: occurring on the same side of the body contralateral: occurring on the opposite side of the body

Question 28

what are the 2 conscious sensation spinal cord pathways called?

Answer 28

dorsal column pathway | spinothalamic tract

Question 29

what are the 4 unconscious sensation spinal cord pathways called?

Answer 29

spinocerebellar tract spinotectal tract spinoreticular tract spino-olivary tract

Question 30

what is the spinocerebellar tract?

Answer 30

a spinal cord pathway for unconscious proprioception and movement coordination

Question 31

what is the spinotectal tract?

Answer 31

a spinal cord pathway for unconsciously turning towards the source of sensory auditory and visual stimulation

Question 32

what is the spinoreticular tract?

Answer 32

the spinal cord pathway to induce and maintain wakefulness

Question 33

what is the spino-olivary tract?

Answer 33

the spinal cord pathway for modified cerebellar activity in response to environmental change/ reaction to pain

Question 34

where is the dorsal column pathway located? | what is its function?

Answer 34

in the dorsal column of the spinal cord | to carry discrimitve touch. pressure, vibration and proprioception signals to the cerebral cortex

Question 35

roughly describe the somatotropic arrangement of the dorsal column?

Answer 35

from medial to lateral; we have axons from sacrum, lumbar region, thoracic region and cervical region

Question 36

describe the purpose of T6 in the dorsal column pathway?

Answer 36

Axons from the upper body enter at or above T6 and travel in the cuneate fasciculus. axons from the lower body enter below T6 travel in the gracile fasciculus.

Question 37

describe the dorsal column pathway?

Answer 37

A sensory receptor in the body detects a stimulus and produce an impulse which enters the dorsal column of the spinal cord. It will enter the gracile/cuneate fasciculus in the spinal cord (depending on it relative position to T6) and then it will head to its corresponding nucleus in the medulla oblongata. Then synapses with a 2nd neurone which will travel from the nucleus in the medulla and will decussate. It will then enter the thalamus and synapse to a 3rd neurone. This then carries the sensory information from the thalamus to the somatosensory cortex in the post-central gyrus

Question 38

where is the spinothalamic tract located? what are its functions?

Answer 38

within the ventral portion of the lateral column of the spinal cord. it carries impulses of crude touch, pain and temperature to the somatosensory cortex

Question 39

what is the function of the anterior spinothalamic tract?

Answer 39

it carries impulses of crude touch to the somatosensory cortex

Question 40

what is the function of the lateral spinothalamic tract?

Answer 40

it carries impulses of pain and temperature to the somatosensory cortex

Question 41

describe the somatotropic arrangement of the spinothalamic tract?

Answer 41

sacral is more lateral and cervical more medial.

Question 42

describe the spinothalamic tract pathway?

Answer 42

wherThe 1st order neurone from a sensory receptor somewhere in the body enters the dorsal horn of the spinal cord and ascends 1-2 segments in the dorsolateral fasciculus. It synapses with a 2nd order neurone (by release of substance P) which then decussates and travels through the ventral white commissure and ascends in the ventrolateral fasciculus of the spinal segment up to the thalamus- via the spinothalamic tract. It synapses here with a 3rd order neurone which travels to the somatosensory cortex. This is where the perception of pain/touch/temperature can be perceived.

Question 43

where does the dorsal column tract decussate?

Answer 43

in the medulla

Question 44

where does the spinothalamic tract decussate?

Answer 44

in the spinal cord 2 segments higher than entry level via the anterior white commissure

Question 45

what is dissociated sensory loss?

Answer 45

A pattern of sensory loss with selective loss of touch sensation and proprioception without loss of pain and temperature, or vice-versa.

Question 46

what do brainstem lesions cause?

Answer 46

contralateral sensory loss

Question 47

what do spinal cord lesions cause?

Answer 47

dissociated sensory loss