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INTS > INTS9 - Motor and Sensory Pathways > Flashcards

INTS9 - Motor and Sensory Pathways Flashcards

1
Q

Where do the principle descending motor pathways originate from.

A

Originate from the cerebral cortex and the brainstem.

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2
Q

What are the names of the two motor pathways originating from the primary motor cortex.

A

Corticobulbar tract and corticospinal tract.

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3
Q

What are the fewest number of neurons involved in a motor response, connecting the brain to a muscle. Give name for this pathway.

A
  1. Upper motor neuron at the brain and lower motor neuron at the spinal cord. Referred to as a monosynaptic pathway.
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4
Q

What is the motor homunculus.

A

Somatic representation that maps body regions to corresponding, region on primary motor cortex, indicating how much cortical space is required per type of movement.

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5
Q

Briefly discuss corticobulbar tract.

A

Originate from primary motor cortex located near pre central and central Gyri. Goes to muscles in the face and neck, aiding various movements of these body regions.

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6
Q

Where is the primary motor and primary sensory cortex located.

A

In between the pre central and post central gyri.

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7
Q

What are the four pathways originating from the brainstem.

A

Vestibulospinal. Recticulospinal. Rubrospinal. Tectospinal.

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8
Q

Which body regions mapped to the motor homunculus take up more space than others.

A

Face and hands map to a leader region of the brain than the foot and tongue do.

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9
Q

What are the two regions of the corticospinal tract.

A

Lateral and anterior corticospinal tract.

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10
Q

What is controlled by the lateral and anterior corticospinal tract respectively.

A

Lateral tract - skilled voluntary movements.

Anterior tract - postural adjustments following limb movements.

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11
Q

Where do corticospinal fibres originate from and how do they form the anterior and lateral corticospinal tracts.

A

Originate in the primary motor cortex in the brain. 85-90% DecussAte in the medulla to form the lateral corticospinal tract. Remaining 10-15% form the anterior corticospinal tract.

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12
Q

Where do the anterior and lateral corticospinal tracts terminate.

A

Anterior tract - terminate on the lower motor neurons, at the same level where the fibres cross.
Lateral tract - terminate on the lower motor neurons in the anterior horn of the spinal cord.

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13
Q

Four motor tracts are under voluntary control. True or false.

A

False - involuntary control. On trolls vestibulospinal, reticulospinal, tectospinal and rubrospinal.

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14
Q

Where does the rubrospinal tract originate from.

A

Red nucleus.

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15
Q

Where do the reticulospinal, tectospinal and vestibulospinal tracts originate from.

A

Superior colliculus. Vestibular nuclei.

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16
Q

Discuss role of vestibulospinal tract. Mention origination.

A

Conveys signals from inner ear to muscles allowing the maintenance of balance by providing information on head movement and position. Controls movement of neck and postural adjustments.
Originate from lateral and medial vestibular nuclei.

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17
Q

What are the two classifications of the vestibulospinal tract. What does each do.

A

Medial and lateral.
Medial - bilateral to neck muscles. Axons terminate on cervical and thoracic motor neurons.
Lateral - ipsilateral excitatory to extensors. Inhibitory to flexors. Axons terminate at all levels of the spinal cord. Mediate postural adjustments.

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18
Q

Discuss origin and role of rubrospinal tract.

A

Originate from red nucleus in midbrain. Travel through brainstem and synapse onto lower motor neurons supplying flexor muscles of upper limbs with nerves. Mainly taken over by the corticospinal tract in humans,

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19
Q

What does the brainstem consist of.

A

Midbrain, pons and medulla.

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20
Q

Discuss origin and role of reticulospinal tract.

A

Originate from reticular formation of pons and medulla. Control orientation of body towards or away from stimuli. Mainly ipsilateral with motor neuron axons terminating at any level of the spinal cord.

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21
Q

Discuss origin and function of tectospinal cord.

A

Fibres originate from superior colliculus of Brain. Fibres descend bilaterally through brainstem and innervate lower motor neurones of the neck. Aid orientation of head and neck during eye movements.

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22
Q

Give the names of the 7 overall tracts observed in a axial cut of a spinal column section

A 
Lateral and anterior corticospinal. 
Medial and lateral reticulospinal. 
Rubrospinal. 
Vestibulospinal. 
Tectospinal.
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23
Q

Where do somatosensory pathways carry information to and from.

A

Carry information from the periphery (skin and joints) into the central nervous system.

24
Q

What types of stimuli are relayed as information in the somatosensory pathways.

A

Fine touch. Pressure. Vibration. Crude touch. Pain. Temperature.

25
Q

What are the three types of neurons present in somatosensory pathways.

A

Primary. Secondary. Tertiary.

26
Q

What are the two somatosensory pathways.

A

Dorsal column pathway.

Spinothalamic pathway.

27
Q

What is the dorsal column pathway used to relay information regarding.

A

Discriminative touch. Vibration. Proprioception.

28
Q

What is the spinothalamic pathway used to relay information regarding.

A

Pain and temperature.

29
Q

Discuss pathway for touch and proprioception.

A

Primary neurons enter spinal cord and ascend ipsilaterally to the medulla. At the medulla, primary neurons synapse onto secondary neurons whilst decussating. Secondary neurons ascend contralaterally to the thalamus. At the thalamus, secondary neurons synapse onto tertiary neurons, which project to the relevant area in the primary somatosensory cortex.

30
Q

What types of receptors are involved in the dorsal column pathway.

A

Mechanoreceptors - detection of mechanical stimuli e.g

Touch, pressure, vibrations.

31
Q

Where are mechanoreceptors located in the dorsal column pathway.

A

Peripheral axons of primary sensory neurons.

32
Q

Define decussation.

A

Crossing over of fibres from one side to another to form an X.

33
Q

Where are cell bodies in the peripheral nervous system located for the body and head.

A

Body - dorsal root ganglia.

Head - trigeminal ganglia.

34
Q

Where do fibres from the dorsal column pathway enter the ascending dorsal column pathway.

A

Dorsal horn,

35
Q

What is the contralateral medial lemniscus tract.

A

Fibres which go from the medulla to the thalamus in the dorsal column pathway after primary neurons have synapses onto secondary neurons.

36
Q

How is the intensity of a stimulus translated to action potentials.

A

Increased stimulus means the firing frequency of action potentials in increased, not the amplitude of the action potential itself.

37
Q

Difference between gracile and cuneate tract.

A

Gracile tract takes information from legs through Primary neuron to medulla.
Cuneate tract takes information from arms through primary neuron to medulla.

38
Q

What is the name of the location of the first synapse in the dorsal column pathway,

A

Gracile nucleus - information from legs.

Cuneate nucleus - information from arms.

39
Q

Give brief description as to purpose of lateral inhibition.

A

Enhancing difference between adjacent inputs allowing pin point accuracy.

40
Q

What is the name of the pathway for pain and temperature detection.

A

Spinothalamic pathway. Split into lateral and anterior.

41
Q

Discuss pathway for spinothalamic pathway.

A

Primary neurons enter spinal cord and synapse onto Secondary neurons and decussate immediately. Secondary neurons ascend contralaterally up to the medulla. Synapse onto tertiary neurons which project to relevant area of the primary somatosensory cortex.

42
Q

What are the differences between the anterior and lateral spinothalamic tract.

A

Anterior - information about crude touch.

Lateral - information about pain and temperature.

43
Q

What are the types of receptors involved in the spinothalamic pathway.

A

Polymodal free nerve endings. Can detect mechanical, thermal or chemical stimuli.

44
Q

Where does decussation of the spinothalamic pathway occur for the body and head respectively.

A

Body - spinal cord.

Head - brainstem.

45
Q

What are the different modalities of sensation.

A

Touch. Pain. Temperature. Taste. Hearing.

46
Q

Name for sensations from outside world and within body respectively.

A

Outside world - exteroception.

Inside body - enteroception.

47
Q

What are conscious and non conscious sensations.

A

Conscious - can be felt.

Non conscious - cannot be felt e.g. homeostasis inside the body.

48
Q

Define proprioception and nociception.

A

Proprioception - perception/awareness of position/movement of the body.
Nociception - sensory nervous systems response to harmful stimuli.

49
Q

Define receptive field of a neuron.

A

Region of skin which is supplied by a single sensory neuron.

50
Q

What influences how ability of the CNS to localise the stimulus.

A

Size of receptive field of the neuron and degree of overlap with receptive fields of other neurons.

51
Q

If stimulus lies within the overlapping area of two receptive fields, is the accuracy improved or not improved.

A

Accuracy improved - able to detect clearly where the stimulus has arisen from.

52
Q

How can overlapping areas between receptive fields be benficial. Link to injury or disease.

A

Receptive field of damaged neuron will still have some area covered by receptive fields of nearby neurons ensuring a stimulus in that area can still be detected with accuracy.

53
Q

Discuss process of lateral inhibition.

A

Primary neuron response is proportional to the strength of the stimulus. Pathway closest to the stimulus then laterally inhibits surrounding neurons. This enhances the perception of the stimulus. Action potential frequency of neighbouring neurons is reduced due to lateral inhibition, aiding accurate location of stimulus.

54
Q

Describe lateral inhibition in one sentence.

A

Inhibitory region around excitatory region created aiding accurate pin pointing of location of stimulus.

55
Q

Discuss what two point discrimination is.

A

The smallest distance between two points can actively be determined as two different points, instead of being felt as one point.

56
Q

What can the two point discrimination test be used to determined.

A

Progression or treatment of various neurodegenerative disease.

57
Q

Areas with highly packed neurons would have a larger two point discrimination. True or false.

A

False. More neurons means two distinct signals can be sent to the brain, allowing the determination to two points.

INTS (11 decks)

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