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Y1 physiology > organisation of the spinal cord > Flashcards

organisation of the spinal cord Flashcards

1
Q

reflex: define

A

an involuntary reaction to an external stimulus

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2
Q

2 types of reflexes:

A
  • monosynaptic: involves one central synapse

- polysynaptic: involves many central synapses

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3
Q

a reflex arc consists of:

A
  1. sensory element (receptor)
  2. afferent (sensory) nerve
  3. central processing unit
  4. efferent (command) nerve
  5. effector (eg. a muscle)
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4
Q

reflex latency: define

A

the time delay between the stimulus and the reaction

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5
Q

what does reflex latency consist of?

A
  1. afferent conduction delay
  2. central processing delay
  3. efferent conduction delay
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6
Q

what does the nervous system consist of?

A
  • central nervous system (brain & spinal cord)

- peripheral nervous system (somatic and autonomic systems)

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7
Q

what does the afferent division of the nervous system do?

A

it transmit sensory information from outside the body to the CNS. this is achieved with sensory receptors.

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8
Q

what does the efferent division of the nervous system do?

A

it transmits motor information to the periphery. The effects include:

  • contraction of skeletal muscles: movement through somatic NS
  • contraction of smooth muscle: activity of internal organs through autonomic NS.
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9
Q

2 main types of cells in the nervous system:

A

neurons and glial cells

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10
Q

nucleus, ganglion: define

A

nucleus: a group of neuron cell bodies that are next to each other in the CNS
ganglion: a group of neuron cell bodies that are located outside of the CNS

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11
Q

what are some types of glial cells, and what do they do?

A
  • oligodendrocytes: produce myelin in the CNS
  • Schwann cells: produce myelin in the PNS
  • astrocytes: only present in CNS. they give structural and metabolic support to neutrons, as well as act as resident immune cells, and help seal and nourish the blood-brain barrier.
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12
Q

what does the white matter in the spinal cord contain?

A

afferent and efferent axons (myelinated and unmyelinated)

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13
Q

what does the grey matter in the spinal cord contain?

A

nerve cell bodies ad unmyelinated axons

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14
Q

what are the 3 pairs of grey horns in the grey matter of spinal cord?

A
  • anterior (ventral) horns
  • posterior (dorsal) horns
  • lateral horns
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15
Q

what is the function of the anterior/ventral horn?

A

it receives information from the motor cortex of the brain, and then sends it to the skeletal muscles to trigger voluntary movement.

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16
Q

what is the function of the posterior/dorsal horn?

A

It takes sensory information from the outside world and sends it to the sensory cortex of the brain.

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17
Q

what is the function of the lateral horns, and with what nervous system is it involved?

A

it is mainly involved with the sympathetic division of the autonomic motor system, and helps regulate processes like urination, digestion, and heart rate.

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18
Q

what does the peripheral nervous system consist of?

A

the peripheral nervous system consists of nerves which are enclosed bundles of axons, that connect the central nervous system to every other part of the body.
- cranial nerves and spinal nerves

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19
Q

what are cranial nerves and how many are there?

A

they are nerves that exit from the skull and innervate the head and neck.
there are 12.

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20
Q

what are spinal nerves and how many are there?

A

nerves that exit various regions of the spinal cord and innervate the rest of the body.
31 pairs.

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21
Q

what is the somatic nervous system made up of?

A
  • afferent or sensory nerves: have axons that carry sensory information from the peripheral tissues like the skin, back to the cell bodies in the posterior horns of the spinal cord
  • efferent or motor nerves: contain the axons that carry motor information from the cell bodies in the anterior horns of the spinal cord to the neuromuscular junction, which is where these axons come into contact with the skeletal muscle cells.
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22
Q

what is the autonomic nervous system (sympathetic & parasympathetic) made up of?

A

the autonomic nervous system is made up of a relay that includes two neurons:

  • preganglionic neuron: have their cell bodies in nuclei throughout the spinal cord in the lateral horns,
  • postganglionic neurons: have their cell bodies in ganglia out of the spinal cord.
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23
Q

how is a signal transmitted in the autonomic nervous system?

A
  1. signals start in a hypothalamic center.
  2. Hypothalamic neurons carry signals down to the spinal cord nuclei where they synapse with preganglionic neurons.
  3. Axons of preganglionic neurons exit the spinal cord to reach the ganglia and synapse with postganglionic neurons.
  4. the axons of postganglionic neurons exit the ganglia to reach the organs and synapse with the target organ cells.
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24
Q

what is the function of the somatic nervous system?

A

controls skeletal muscles

25
Q

what is the function of the autonomic nervous system?

A

coordinates body systems by controlling smooth muscles and glands. it does so without conscious regulation.

26
Q

what is the sympathetic nervous system in control of?

A

the fight or flight response.

27
Q

what are the function and effects of the fight or flight response?

A 
functions to mobilise stored energy in times of need.
increases: 
- blood flow in the skeletal muscles
- heart rate
- blood pressure
- blood sugar level, etc.
decreases:
- blood flow to digestive tracts.
pupillary dilation.
28
Q

what is the parasympathetic nervous system in control of?

A

the rest and digest response.

29
Q

what are the function and effects of the rest and digest response?

A

functions to conserve and restore body energy.
decreases:
- heart rate
- blood pressure
increases:
- secretion by salivary and digestive glands
- blood flow in digestive tract.

30
Q

where are nerve cells of PNS located?

A

located in the cranial nerve nuclei and in the sacral region of the spinal cord.
therefore, the PNS is sometimes called the craniosacral division.

31
Q

functions of the spinal cord:

A
  • distribute motor fibres around the body
  • collect somatosensory information to be passed on to the brain
  • connects brain with the body
  • somatic and autonomic reflexes
  • sensory and motor modulation
32
Q

divisions of the spinal cord:

A
  • cervical (C1-C8)
  • thoracic (T1-T12)
  • lumbar (L1-L5)
  • Sacral (S1-S5)
33
Q

common features of ascending and descending tracts:

A
  • presence of synaptic relays
  • integration of information
  • topographic organisation
34
Q

funiculi: meaning

A

Both ascending and descending tracts are made up of neuronal axons that gather into long columns called funiculi.

35
Q

3 types of ascending tracts:

A
  • dorsal column-medial lemniscus system
  • spinothalamic (anterolateral) system
  • spinocerebellar system
36
Q

what are ascending tracts made up of?

A

4 successively connected neurons. (first order, second order, third order, fourth order)

37
Q

first order neuron (ascending): location and function

A

found inside dorsal root ganglions

gather sensory input from dorsal root ganglions and sent it to 2nd order neurons

38
Q

2nd order neurons (ascending): location

A

inside the spinal cord or brainstem

39
Q

3rd order neurons (ascending): location

A

inside thalamus

40
Q

4th order neurons (ascending): location

A

in the cerebral cortex

41
Q

decussations: meaning

A

the crossing over of spinal tracts through the spinal cord to the opposite side of the CNS.

42
Q

what information does the dorsal column-medial lemniscus system transmit?

A

it transmits delicate sensations like:

  • vibration
  • proprioception
  • two-point discrimination
  • touch
43
Q

process of dorsal column-medial lemniscus system transmission:

A
  1. receptors in the body are stimulated. they send sensory input through peripheral nerves that are made of the axons of first order neurons. these nerves travel to the dorsal root ganglion where the first order cell bodies reside.
  2. These ganglions send out short axons that enter the spinal cord and to the ipsilateral dorsal area, called the dorsal column. the dorsal column contains the gracilis fascicle and the cuneate fascicle.
  3. Both the gracilis fascicle and cuneate fascicle (1st order) ascend through the ipsilateral spinal cord all the way up to the medulla where we can find the gracilis nucleus and cuneate nucleus.
  4. Inside these two nuclei both fasciculi end by synapsing on the bodies of the second order neurons.
  5. Second order neuronal axons now decussate and form the pathway called medial lemniscus, which ascends to the contralateral thalamus, more specifically to its ventral posterolateral nucleus.
  6. Inside this nucleus is where medial lemniscus ends by synapsing on the third order neurons.
  7. the third order neuronal axons now ascend toward cerebrum, through the internal capsule to the primary somatosensory cortex which contains fourth order neurons, the final destination for the dorsal column.
44
Q

topographic organisation: meaning

A

the organization where the medial parts of the dorsal column transmit lower body sensation and the lateral parts of the dorsal column transmit sensation from higher body parts.

45
Q

what is the name of the medial part of the dorsal column, and what does it contain?

A

gracilis fascicle

it contains the axons that carry sensation from the lower parts of the body

46
Q

what is the name of the lateral part of the dorsal column, and what does it contain?

A

cuneate fascicle

it contains axons that carry sensation from the upper parts of the body

47
Q

what information does the spinothalamic (anterolateral, ALS) system transmit?

A

it transmits sensory information about:

  • crude touch
  • pain
  • pressure
  • temperature
48
Q

process of spinothalamic system transmission

A
  1. 1st order neurons travel from receptors to the dorsal root ganglion.
  2. info is then sent through another bundle of axons that enters the ipsilateral spinal cord. the axons synapse directly, or indirectly through the interneurons, on the 2nd order neurons, whose cell bodies are found inside the posterior, or dorsal horn of the spinal cord.
  3. the second order neuronal axons decussate and form the anterior spinothalamic tract that transmits crude touch and pressure sensory inputs, and the lateral spinothalamic tract that transmits pain and temperature sensory input.
  4. Both anterior and lateral spinothalamic tracts ascend through the contralateral spinal cord all the way up to the contralateral thalamus, to its ventral posterolateral nucleus, and end by synapsing on the third order neurons found inside this nucleus.
  5. Third order neuronal axons ascend toward the cerebrum through the internal capsule to the primary somatosensory cortex where they synapse on the fourth order neurons.
49
Q

what is the function of the spinocerebellar tract?

A

help coordinate the muscles in the trunk and the limbs by transmitting unconscious proprioceptive sensations about the position of body parts.

50
Q

process of spinocerebellar tract transmission:

A
  1. signals from proprioceptors travel through 1st order neurons that form peripheral nerves and enter the dorsal root ganglion which send out axons that enter the spinal cord and synapse on the second order neurons found inside the ipsilateral gray matter.
  2. Second order neuronal axons now make two spinocerebellar tracts. They either decussate right away and make the ventral spinocerebellar tract just lateral to the lateral spinothalamic tract, or they stay on the ipsilateral side and make the dorsal spinocerebellar tract.
  3. the ventral spinocerebellar tract ascending to the superior cerebellar peduncle, passing through it and then decussating again before arriving at the ipsilateral cerebellar cortex where it synapses on neurons inside the cortex. The dorsal spinocerebellar tract doesn’t decussate at all but ascends to the inferior cerebellar peduncle, passes through it and arrives at the ipsilateral cerebellar cortex as well, ending it’s journey by synapsing on the last neuron inside the cortex.
51
Q

what is the function of descending tracts?

A

descending tracts are motor pathways that control muscles of the trunk and extremities.

52
Q

what are the descending tracts made up of?

A

2 connected neurons: upper and lower motor neurons.

53
Q

location of upper motor neuron

A

inside the cerebral cortex or brainstem

54
Q

location of the lower motor neuron

A

inside the anterior (ventral) horns of the spinal cord.

55
Q

2 types of motor pathways, and their functions.

A
  • direct motor pathways/pyramidal tracts: initiate from the primary motor cortex that contains cells called pyramidal cells.
    functions: send the motor input necessary for fine, conscious muscle movements.
  • indirect motor pathways (extrapyramidal tracts): originate from the deep nuclei in the brain stem.
    functions: control balance, body posture and coarse movements.
56
Q

anterior corticospinal tract: function and transmission process

A

functions: control the muscles of the trunk
process:
1. descends through the internal capsule and cerebral peduncle to the spinal cord where it is positioned medial to the anterior spinothalamic tract.
2. Once it gets to the desired spinal segment it, decussates and synapses with lower motor neurons in the ventral horn.
3. Lower motor neurons axons leave the spinal cord through the ventral root and peripheral nerves and reach the muscles of the trunk.

57
Q

lateral corticospinal tract: function and transmission process

A

function: control muscles of the extremites
process:
1. descends through the internal capsule and cerebral peduncle.
2. once it gets to the medulla, it decussates at the place called decussation of pyramids.
3. Now it continues through the contralateral spinal cord where it descends medial to the posterior spinocerebellar tract, until it reaches the ventral horn where it synapses with lower motor neurons.
4. Lower motor neuron axons leave the spinal cord through the ventral root and peripheral nerves and reach the muscles of the extremities.

58
Q

vestibulospinal tract: function and transmission process

A

function: transmits motor input for the extensor muscles of the trunk and extremities, helping us maintain balance.
process:
1. the axons of the lateral vestibular nulei in the brainstem descend to the ipsilateral spinal cord and synapses with short interneurons that activate the lower motor neurons in the ventral horn.
2. Their axons leave the spinal cord through the ventral root, go through the peripheral nerves and reach the extensor muscles that they innervate.

Y1 physiology (5 decks)

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