Spinal Cord and Periphery (neuroanatomy)

Question 1

Which type of neurone is in the sensory dorsal root?

Answer 1

Pseudounipolar

Question 2

Which type of neurone is in the sensory motor root?

Answer 2

Multipolar

Question 3

There are ascending and descending tracts in the spinal cord and brain.
They carry information.
How can you tell if a tract is an ascending tract?

Answer 3

Based on how it is named i.e. if it starts with spino- e.g. spinocerebellar tract

Question 4

There are ascending and descending tracts in the spinal cord and brain.
They carry information.
How can you tell if a tract is an descending tract?

Answer 4

Based on how it is named i.e. if it ends in -spinal e.g. corticospinal tract

Question 5

Do ascending tracts carry sensory or motor information?

Answer 5

Sensory

Question 6

Do descending tracts carry sensory or motor information?

Answer 6

Motor

Question 7

What does the corticospinal tract do?

Answer 7

Carries motor impulses from motor cortex to skeletal muscles.

Question 8

Which type of sensory impulses does the dorsal column carry?

Answer 8

Carries touch, tactile localisation, vibration sense and proprioception

Question 9

Which type of sensory impulses does the lateral spinothalamic tract carry?

Answer 9

Pain and temperature

Question 10

Where does the corticospinal tract pathway start from?

Answer 10

Motor cortex (area 4)

Question 11

Where do the corticobulbular fibres go?

Answer 11

Contralateral cranial nerve nuclei

Question 12

RECAP- which cranial nerves arise from the brainstem?

Answer 12

CN 3-12

Question 13

If you want to move your hands, which plexus of the upper limb will the nerves have to pass through?

Answer 13

Brachial plexus

Question 14

What is the root value of the brachial plexus?

Answer 14

C5-T1

Question 15

Which nerve plexus do nerves supplying the lower limb need to go through?

Answer 15

Sciatic plexus

Question 16

What is the root value for the sciatic plexus?

Answer 16

L4-S3

Question 17

When the motor fibres travel down the brainstem, where will they sit in the midbrain?

Answer 17

In the crus cerebri, part of the midbrain which sits anterior to the substancia nigra

Question 18

What happens to the bundle of motor fibres when it reaches the pons?

Answer 18

Motor fibres still remain anterior but broken into a number of different bundles.

Question 19

When the motor fibres reach the medulla, they come together again and form projections.
What are these projections called?

Answer 19

Pyramids

Question 20

What happens at the lower part of the pyramids?

Answer 20

Fibres cross over (decussation).

Question 21

How many motor neurons are in the motor pathway?

Answer 21

Two- we can call these the upper and lower motor neuron.

Question 22

Where would you find the cell body of the upper motor neuron?

Answer 22

Grey matter of the precentral gyrus

Question 23

The upper motor neuron travels down the corona radiata, internal capsules, brainstem before crossing over at the pyramidal decussation.

Where does the upper motor neuron eventually synapse?

Answer 23

Ventral horn of the grey matter in the spinal cord

Question 24

Where does the lower motor neuron start?

Answer 24

Ventral horn of the spinal cord

Question 25

What does the lower motor neuron travel out along to get to the skeletal muscle?

Answer 25

Spinal nerves

Question 26

Where is the dorsal column situated?

Answer 26

Posterior white matter of the spinal cord (can be known as the posterior column).

Question 27

Is the posterior/dorsal column a descending or ascending tract?

Answer 27

Ascending tract

Question 28

Where are the receptors for sensation found?

Answer 28

Skin

Question 29

If the touch receptor in your right index finger was stimulated, where would the sensory fibre go?

Answer 29

Would go through brachial plexus, through the dorsal roots, continues up the dorsal column until it reaches the medulla.

Question 30

What happens to the neuron when it reaches the medulla after travelling up the dorsal column?

Answer 30

Synapses. Another axon picks up tis impulse- this is known as the second order as it is the second nucleus. ->could be worth drawing this pathway out for the motor and sensory neurons and the ascending/descending trunks? Just a revision idea :)

Question 31

Which type of neuron was the: 1. First order neuron 2. Second order neuron

Answer 31

1. Pseudounipolar 2. Multipolar ->this is because...honestly I'm not sure. I looked it up and couldn't find much...sorry x

Question 32

What does the second order nucleus?

Answer 32

Crosses over (decussates) in the medulla

Question 33

After the crossing over of the second order neuron, the dorsal tract is no longer called this as it is not in the posterior column of the spinal nerve. What is it called after the decussation?

Answer 33

Medial lemniscus

Question 34

Where does the medial lemniscus pass through?

Answer 34

Medulla, pons and midbrain and then reaches the thalamus

Question 35

What happens in the thalamus after the second order nucleus has sent to information up?

Answer 35

Third order nucleus takes over

Question 36

Where does the third order nucleus go to and from?

Answer 36

From thalamus to the post-central gyrus

Question 37

RECAP- which areas cover the post-central gyrus?

Answer 37

Areas 3, 1, 2

Question 38

Why does the third order neuron take the impulse to the postcentral gyrus?

Answer 38

Site of the primary sensory area in the parietal lobe

Question 39

Is the lateral spinothalamic tract an ascending or descending tract?

Answer 39

Ascending tract as carries sensory info

Question 40

Why is there two sensory pathways?

Answer 40

Lateral spinothalamic tract carries pain and temperature info. Therefor, the body needs to respond more quickly to these as they could potentially be harmful, hence why there is another, quicker pathway

Question 41

Which type of neuron would carry sensation if the right index finger felt pain?

Answer 41

Pseudounipolar

Question 42

Describe the pathway taken by the pseudounipolar nucleus if carrying information due to pain?

Answer 42

Comes through brachial plexus, through dorsal root and dorsal ganglion and enters the spinal cord. (so far, same as the dorsal column route).

Question 43

What happens to the first order neuron when it reaches the spinal cord when carrying information responding to pain?

Answer 43

Axon enters grey matter of spinal cord and ends at the level at which it entered.

Question 44

In response to pain or temperature, what happens once the first order neuron ends?

Answer 44

Second order neuron picks up impulse and and crosses over the reach lateral spinothalamic tract

Question 45

What happens when the second order nucleus reaches the lateral spinothalamic tract?

Answer 45

Ascends up entire spinal cord and goes to brainstem.

Question 46

Where will the second order nucleus synapse when responding to pain or temperature?

Answer 46

Ventral posterolateral (VPL) nucleus of hypothalamus (same as dorsal column pathway).

Question 47

What happens after the second order neuron synapses in the thalamus after responding to pain?

Answer 47

Third order neuron picks up impulse and takes it the grey matte of the post-central gyrus. ->same as other route

Question 48

Where does the second order neuron come out of in the descending motor tract?

Answer 48

Comes out through ventral roots and goes through spinal nerves to the muscle

Question 49

Not all sensory information needs to be sent up to the brain. When is this the case?

Answer 49

When an immediate response is required e.g. after touching something hot.

Question 50

When an immediate response is required and sensory information is not passed up to the brain, what makes the decisions?

Answer 50

The spinal cord or other lower centres can make decisions, making up our reflexes.

Question 51

What is a reflex?

Answer 51

An involuntary stereotyped pattern of response brought about by a sensory stimulus.

Question 52

If reflexes are mediated at the level of the spinal cord, what type of reflex does this make them?

Answer 52

Spinal reflex.

Question 53

The stretch reflex can be demonstrated by which test?

Answer 53

Knee jerk reflex

Question 54

Which tendon is hit for the knee jerk reflex to occur?

Answer 54

Patellar tendon

Question 55

Which muscle contracts to cause the knee jerk movement?

Answer 55

Quadricepcs femoris

Question 56

What happens to the patellar tendon when it is hit?

Answer 56

The tendon stretches, causing muscle fibres within the quadriceps to also be stretched

Question 57

What do proprioceptors do?

Answer 57

Sensory receptor which responds to how stretched or relaxed a muscle is

Question 58

What is the quadriceps muscle innervated by?

Answer 58

Femoral nerve

Question 59

What is the root value of the femoral nerve?

Answer 59

L2-4

Question 60

Which plexus does the femoral nerve come from?

Answer 60

Lumbar plexus

Question 61

What happens when the patellar tendon gets hit?

Answer 61

Muscle stretches and this causes proprioceptor fibres from the femoral nerve to get activated.

Question 62

What happens after the proprioceptor fibres in the femoral nerve get activated?

Answer 62

Activated fibres are carried by the femoral nerve to lateral horns of L2-4. Motor neurons then come out via femoral nerve and act on the quadriceps muscle, making it contract.

Question 63

In order to stretch the quadriceps muscles, which muscles need to relax?

Answer 63

Hamstring muscles

Question 64

How is the hamstring relaxed at the same time as the quadriceps stretched?

Answer 64

In addition to fibres going to L2-4 to get motor neurons to leave and cause muscle contraction, some fibres go down to sacral segments of spinal cord and inhibit the neurons which innervate the hamstring muscles, causing them to relax.

Question 65

What type of reflex is the stretch reflex?

Answer 65

Monosynaptic arc reflex

Question 66

Describe what would happen if you stepped on a pin.

Answer 66

This might be wordy but read and try to understand x Pain receptors activated. Sensory nerves carry impulse through branches of the sciatic nerve and through dorsal grey matter of spinal cord. This acts on an inhibitory neuron, which stimulates a nerve in the ventral horn to go and contract hamstring and pull your foot away from the painful stimulus.

Question 67

Part 2 hehe... your foot is off the ground and off the pin...great! But now, describe what happens to maintain balance.

Answer 67

Crossed extensor response- stimulates femoral nerve which contracts the quadricep muscle, allowing you to gain balance.

Question 68

If you want to contract any muscle on the left side of your body, where do the impulses come from?

Answer 68

Precentral gyrus on left side

Question 69

What are reflexes mediated by?

Answer 69

Lower motor nerves

Question 70

If there is a lesion affecting the upper motor neuron but not the lower motor neuron, what will happen?

Answer 70

Paralysis- however, as LMN still working, you can still have reflexes.

Question 71

If the is an upper motor neurone lesion but still reflexes, what are these reflexes like?

Answer 71

Exaggerated, as if to compensate

Question 72

Does tonicity of muscle require upper or lower motor neurons?

Answer 72

Lower motor neurons

Question 73

Therefore, if there is an upper motor neuron lesion, what happens to the tone?

Answer 73

Also become exaggerated

Question 74

What is increased tone known as ?

Answer 74

Spasticity

Question 75

What happens if there is damage to the lower motor neuron?

Answer 75

Paralysis with lost reflexes and flaccidity

Question 76

What would happen in a patient with a left upper motor neuron lesion at the internal capsule?

Answer 76

Right sided paralysis Hyper-reflexia Increased tone

Question 77

What would happen in a patient with a left upper motor neuron lesion at the upper cervical spinal cord?

Answer 77

Left sided paralysis Hyper-reflexia Increased tone ->left not right because it is below the level of decussation

Question 78

What would happen in a patient with a left lower motor neuron lesion?

Answer 78

Left sided paralysis Absent reflexes Flaccid ->again, left paralysis not right as a lower lesion

Question 79

A patient presents with left sided paralysis. They still have reflexes but they are exaggerated. The muscles are very toned. What could this be?

Answer 79

Depending on location- could be either: -Right UMN lesion -Left UMN lesion but ultimately it's a upper motor nerve lesion. If above the level of decussation, it will be a R UMN lesion.

Question 80

Therefore, what do lesions above the level of decussation cause?

Answer 80

Contralateral paralysis

Question 81

Therefore, what do lesions below the level of decussation cause?

Answer 81

Ipsilateral paralysis

Question 82

Which group of diseases are caused by affected ventral horns of the spinal cord?

Answer 82

Motor neuron disease

Question 83

In terms of the lateral spinothalamic tract, is pain and temperature info going to be contralateral or ipsilateral?

Answer 83

Contralateral ->Level of decussation is so low, lesions are going to be above it and affect opposite side

Question 84

What happens in Brown-Sequard syndrome?

Answer 84

One side of the cervical vertebrae is affected resulting in weakness and paralysis on one side of the damage and loss of pain and temperature sensations on the opposite side.

Question 85

This lectures are confusing but Asha explains them well so just rewatch these lectures before any exams :)

Answer 85

okay boss