Sensory function

Question 1

What are sensory pathways?

Answer 1

routes by which info received by different parts of the body are conveyed to the sensory cortex in the brain

Question 2

What are sensory pathways also known as?

Answer 2

Ascending pathways

Question 3

Where is the primary sensory cortex?

Answer 3

In the post-central gyrus

Question 4

What does the primary sensory cortex feel?

Answer 4

Pain, pressure, or temperature in the appropriate area of the sensory cortex

Question 5

What is a dermatome?

Answer 5

An area of skin innervated by a pair of left and right dorsal roots. Each segment of the spinal cord corresponds with one dermatome

Question 6

How can dermatomes be grouped?

Answer 6

By the region of the spinal cord that innervates them

Question 7

What is exteroception?

Answer 7

Sensation arising from outside the body

Question 8

How does the body sense exteroception?

Answer 8

1. somatosensory receptors on body surface or linings (touch, temp, pain, pressure)
2. special sensory receptors from special sense organs (tongue, nose, eyes, ears)

Question 9

What is proprioception?

Answer 9

Receptors in muscles, joints, and tendons which continuously convey info to the brain about location, orientation, and movement of the body

Question 10

What receptors sense viscerosensation?

Answer 10

1. mechanoreceptors
2. chemoreceptors
3. nociceptors (sense internal pain)

Question 11

What is the direction of the sensory pathways?

Answer 11

Always afferent and ascending from the receptor to the sensory cortex

Question 12

What are the neurons the somatosensory pathways use?

Answer 12

1. first order neurons
2. second order neurons
3. third order neurons

Question 13

What are first order neurons?

Answer 13

the sensory component of a spinal nerve which convey info from the receptor to the central nervous system

Question 14

What do second order neurons do?

Answer 14

convey info from lower areas of the CNS to the thalamus of the opposite side

Question 15

Where is the thalamus loocated?

Answer 15

in the diencephalon

Question 16

What is decussation?

Answer 16

Crossing over of neurons which allows contralateral control

Question 17

Where does sensory decussation occur?

Answer 17

in the medulla or spinal cord

Question 18

What do third order neurons do?

Answer 18

convey infofrom thalamus to the sensory cortex

Question 19

What happens when exteroceptive info reaches brain?

Answer 19

Sensory info that reaches consciousness without knowing the source. We are aware of it but need the sensory association cortex to interpret and make sense of it

Question 20

What happens when viscerosensation reaches the brain

Answer 20

May reach consciousness, but is poorly localised. Many aspects do not reach consciousness

Question 21

What is white matter made up of?

Answer 21

axons

Question 22

What is grey matter made up of?

Answer 22

cell bodies, dendrites, and synapses

Question 23

What does each spinal nerve consist of?

Answer 23

1. a dorsal root going to the dorsal horn
2. ventral root going out of ventral horn

Question 24

What does the dorsal root do?

Answer 24

Carries sensory neurons in from that region of the body. The cell bodies are outside the spinal cord and form the dorsal root ganglion

Question 25

What does the ventral root do?

Answer 25

Carries the motor neurons out of that region of the body

Question 26

What are the somatosensory pathways known as?

Answer 26

1. the anterolateral pathway
2. the dorsal column pathway

Question 27

What can the anterolateral pathway be broken down into?

Answer 27

1. the anterior and lateral spinothalamic tracts
2. the spinoreticular tracts

Question 28

What does the dorsal column pathway do?

Answer 28

Carry fine touch, texture, vibration, pressure, and proprioceptive info

Question 29

What does the anterior anterolateral spinothalamic tract do?

Answer 29

Carries info about non-discriminative touch and temperature

Question 30

What does the lateral anterolateral spinothalamic tract do?

Answer 30

carries info about sharp pain and temperature

Question 31

What does the spinoreticular tract do?

Answer 31

Carries info about pain perception

Question 32

What is the order of the spinothalamic pathways?

Answer 32

1. first order neurons synapse in dorsal horn of same side of spinal cord
2. second order decussate spinal cord to the white matter of the spinal cord on the other side
3. ascend to thalamus and synapse
4. go onto somatosensory cortex

Question 33

What is the order of the spinoreticular pathways?

Answer 33

1. first order neurons synapse in dorsal horn of same side of spinal cord
2. second order decussate spinal cord to the white matter of the spinal cord on the other side
3. ascend to reticular formation in medulla and synapse
4. ascend to thalamus and synapse
5. ascend to somatosensory cortex

Question 34

What is unique about the spinoreticular pathway?

Answer 34

it uses 4 order neurons instead of three

Question 35

What is the order of the dorsal column pathways?

Answer 35

1. primary afferent neurons pass into dorsal white matter on same side without synapsing
2. ascend to dorsal column nuclei in posterior aspect of medulla
3. synapses with an a neuron that will ascend to the thalamus
4. decussates to opposite side
5. ascends in the medial lemniscus tract
6. to the thalamus and synapses
7. then to the sensory cortex

Question 36

What happens if there is damage or disease to primary sensory neurons?

Answer 36

1. the region of the cortex that normally receives input doesn’t receive it
2. may result in loss of sensation from that area

Question 37

What is damage to primary sensory neurons known as?

Answer 37

peripheral nerve disease

Question 38

What happens if there is damage to brainstem neurons or second order neurons?

Answer 38

Causes loss of sensation from the body from below the lesion on the opposite side

Question 39

What happens if there is damage to the spinal cord?

Answer 39

1. if damaged only on one side, touch, pain, and temp is lost from the opposite side
2. proprioceptive info on the same side is also lost