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KINE3650 > Lec 4-The spinal cord and reflexes > Flashcards

Lec 4-The spinal cord and reflexes Flashcards

1
Q

Where does the spinal cord begin and end in the vertebral column?

A

The spinal cord begins at the foramen magnum (base of the skull) and ends at the conus medullaris.

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2
Q

What is the lumbar cistern, and what is its significance?

A

The lumbar cistern is the region of the spine located below the conus medullaris and is filled with cerebrospinal fluid (CSF). It allows for spinal taps to be performed without damaging the spinal cord.

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3
Q

What is the cauda equina, and where is it located?

A

The cauda equina refers to bundles of nerve fibers below the conus medullaris, resembling a horse’s tail.

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4
Q

Correct order of these structures in the spine, from top to bottom, is as follows:

A

Conus Medullaris
Cauda Equina
Lumbar Cistern

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5
Q

What are the three meningeal layers surrounding the spinal cord?

A

The three meningeal layers are the dura mater, arachnoid mater, and pia mater.

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6
Q

What is the arrangement of the meningeal layers from outermost to innermost?

A

The dura mater surrounds the arachnoid mater, which in turn surrounds the pia mater.

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7
Q

What is the subarachnoid space, and what is it filled with?

A

The subarachnoid space is the area between the arachnoid mater and pia mater, and it is filled with cerebrospinal fluid (CSF).

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8
Q

What are denticulate ligaments?

A

Thin, band-like structures located within the spinal cord’s meninges, specifically the pia mater

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9
Q

What is the shape of denticulate ligaments and how do they extend within the spinal cord?

A

Denticulate ligaments extend laterally between the anterior and posterior nerve roots of the spinal cord, resembling a tooth-like shape.

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10
Q

What is the primary function of denticulate ligaments in the spinal cord?

A

Denticulate ligaments serve to anchor and stabilize the spinal cord within the vertebral column, preventing excessive movement or displacement.

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11
Q

What is the dorsomedian sulcus / posterior median / dorsal median , and how does it compare to the ventromedian fissure in terms of depth?

A

The dorsomedian sulcus is another division of the spinal cord, but it is much less deep than the ventromedian fissure.

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12
Q

What is the ventromedian/anteromedian / ventral median fissure, and where is it located in the spinal cord?

A

The ventromedian fissure is a division that divides the front of the spinal cord almost to the central canal.

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13
Q

What does the dorsomedian sulcus continue as, and what is its function?

A

The dorsomedian sulcus continues as the dorsal or median septum, which is a band of glial cells that extends almost to the central canal.

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14
Q

What is the location and significance of the dorsolateral or posterolateral sulcus in the spinal cord?

A

The dorsolateral or posterolateral sulcus extends almost to the dorsal horn of the spinal grey matter and serves as the point where the dorsal rootlets of the spinal nerves emerge.

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15
Q

Is the dorsointermediate sulcus found throughout the entire length of the spinal cord?

A

No, the dorsointermediate sulcus is only present in the cervical and upper thoracic levels of the spinal cord.

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16
Q

Where do the ventral rootlets of the spinal nerves emerge, and what is the anatomical term for this location?

A

The ventral rootlets emerge at the ventrolateral or anterolateral sulcus in the spinal cord.

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17
Q

What happens to the dorsal and ventral roots after they leave the dorsal ganglion?

A

Dorsal and ventral roots join together after exiting the dorsal ganglion to form the complete spinal nerve.

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18
Q

Through which anatomical structure do spinal nerves exit laterally?

A

Spinal nerves leave laterally through the intervertebral foramen.

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19
Q

Besides spinal nerves, what other structures utilize the intervertebral foramen as a pathway?

A

The intervertebral foramen serves as a pathway not only for spinal nerves but also for meningeal nerves, arteries, veins, and lymphatic vessels.

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20
Q
  • Cervical enlargement
A

Spinal cord is wider from C3 to T2, due to presence of nerves
terminating in upper limbs

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21
Q

Lumbar enlargement

A

From L1 to S3 due to
nerves terminating in lower limbs

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22
Q

What is the function of the dorsal root ganglion, and where is it located?

A

The dorsal root ganglion houses the cell bodies of sensory neurons and is located within the dorsal root.

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23
Q

How are spinal nerves protected as they pass through the intervertebral foramen?

A

Nerves passing through the intervertebral foramen are covered by the dura mater, providing protection as they exit the spinal cord.

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24
Q

What are the key steps in the transmission of sensory information from sensory receptors to the spinal cord and, potentially, to the brain?

A

1)Sensory receptors detect stimuli in the body.
2) Sensory neurons transmit signals to the spinal cord.
3) Sensory neurons enter the spinal cord through dorsal roots.
4) Sensory neurons pass through the dorsal root ganglion, containing cell bodies.
5) Sensory information is processed in the dorsal horn of the spinal cord.
Interneurons may modulate the sensory information.
6) Motor commands, if needed, are generated in the ventral horn.
7) Motor commands exit the spinal cord via ventral roots.
8) Dorsal and ventral roots merge to form spinal nerves.
9) Spinal nerves carry sensory and motor signals to specific body regions.
10) Some sensory information may be transmitted to the brain for conscious perception.

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25
Q

Foramen Occlusion

A

Narrowing or blockage of openings in the vertebrae, can compress and cause symptoms in the nerves passing through them.

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26
Q

What are the different types of neurons in the peripheral nervous system (PNS)?

A

PNS neurons can be sensory (afferent), motor (efferent), connecting (intercalated), somatic, or visceral (autonomic).

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27
Q

What is the function of the General somatic efferent (GSE) component of spinal nerves?

A

GSE components of spinal nerves innervate skeletal muscles.

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28
Q

What is the function of the General somatic afferent (GSA) component of spinal nerves?

A

GSA components of spinal nerves carry sensory information perceived in muscles and skin.

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29
Q

What is the function of the General visceral efferent (GVE) component of spinal nerves?

A

GVE components of spinal nerves innervate glands, cardiac muscle, and smooth muscle

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30
Q

What is the function of the General visceral afferent (GVA) component of spinal nerves?

A

GVA components of spinal nerves carry sensory information perceived in visceral organs

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31
Q

What are the components of a reflex?

A

1)Sensory receptor
2) Afferent limb - the peripheral process of a pseudounipolar neuron from the receptor to the synapse in the dorsal horn
3) Interneurons in grey matter (not present in a 2-reflex arc)
4) Efferent limb - motor neuron in the ventral horn and its axon
5) Effector in skeletal muscle

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32
Q

What are muscle spindles, and where are they located?

A

Muscle spindles are special sensors found between regular muscle fibers.

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33
Q

What are the two types of intrafusal fibers found in muscle spindles?

A

Muscle spindles contain “Nuclear Chain” and “Nuclear Bag” intrafusal fibers.

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34
Q

What does the “Nuclear Chain” fiber detect?

A

The “Nuclear Chain” fiber detects changes in muscle length.

35
Q

What do the “Static Nuclear Bag” fibers detect?

A

The “Static Nuclear Bag” fibers also detect changes in muscle lengt

36
Q

What do the “Dynamic Nuclear Bag” fibers detect?

A

The “Dynamic Nuclear Bag” fibers detect the rate of change of muscle length.

37
Q

What do extrafusal fibers do in skeletal muscles?

A

Extrafusal fibers contract to produce movement of the skeletal muscle. They receive alpha motor projections and send sensory projections via dorsal root neurons.

38
Q

What is the primary type of peripheral sensory ending for intrafusal fibers, and what does it do?

A

The primary type, called “Annulospiral” or “Type Ia,” wraps around non-contractile regions and gets activated at the start of a muscle stretch.

39
Q

What is the secondary type of peripheral sensory ending for intrafusal fibers, and what does it do?

A

The secondary type, called “Flower Spray” or “Type II,” terminates close to the ends of non-contractile regions and gets activated while the muscle stretch is in progress.

40
Q

What do Golgi tendon organs respond to?

A

Golgi tendon organs respond to the amount of tension or pulling placed on a muscle.

41
Q

What type of fibers project back to the spine from Golgi tendon organs?

A

Type Ib fibers project information back to the spine from Golgi tendon organs.

42
Q

Do Golgi tendon organs send signals out to muscles?

A

No, Golgi tendon organs do not send signals out (efferent); they react passively.

43
Q

What is the main purpose of the muscle stretch reflex?

A

The muscle stretch reflex is designed to protect muscles from over-stretching.

44
Q

How is the muscle stretch reflex initiated?

A

The muscle is passively stretched, often by tapping it or applying external force.

45
Q

What happens when intrafusal fibers are stretched in the muscle stretch reflex?

A

When intrafusal fibers are stretched, Type Ia fibers fire and create an excitatory synapse on alpha motor neurons that project to the extrafusal fibers of the same muscle.

46
Q

What is the result of the muscle stretch reflex?

A

The muscle contracts slightly, relieving tension on the intrafusal fibers and preventing overstretching.

47
Q

What are autonomic nerves?

A

Autonomic nerves are a part of the autonomic nervous system and are responsible for regulating involuntary bodily functions.

48
Q

How do spinal nerves (ventral rami) receive autonomic postganglionic fibers?

A

Spinal nerves receive autonomic postganglionic fibers from the grey ramus, which originates in sympathetic ganglia

49
Q

What does each spinal nerve innervate?

A

Each spinal nerve innervates a dermatome, which is a specific strip of skin.

50
Q

What is a myotome?

A

A myotome consists of all the muscles innervated by a specific nerve.

51
Q

What is a sclerotome?

A

A sclerotome comprises all the ligaments and bones innervated by a specific nerve.

52
Q

What are the different parts of the grey matter in the spinal cord?

A

The grey matter in the spinal cord has dorsal, lateral, and ventral horns, which are sometimes called columns.

53
Q

How should you distinguish between the grey matter columns and the dorsal columns of white matter?

A

Grey matter columns are found within the central part of the spinal cord and are responsible for processing information, while dorsal columns of white matter are located on the edges and primarily transmit sensory information to the brain.

54
Q

How do white matter tracts in the spinal cord typically run in relation to the spine?

A

White matter tracts in the spinal cord usually run parallel to the spine, while grey matter tracts run perpendicular to it, allowing for communication and processing at specific levels.

55
Q

What connects the two wings of the butterfly-like shape of grey matter in the spinal cord?

A

The two wings of grey matter are connected by the grey commissure, and the central canal runs through the middle.

56
Q

What separates the wings of grey matter in the spinal cord?

A

The wings of grey matter are separated by the small dorsolateral tract of Lissauer, which is part of the white matter.

57
Q

How is the grey matter in the spinal cord divided in terms of regions?

A

The grey matter in the spinal cord is divided into 10 distinct regions.

58
Q

What is the function of grey matter regions I to VI in the spinal cord?

A

Regions I to VI, called the dorsal column/root, receive afferent input from pseudo-unipolar dorsal ganglia. They run the entire length of the spine.

59
Q

What function does grey matter region VII serve in the spinal cord?

A

Region VII, known as the lateral column/root, is responsible for transmitting autonomic efferent signals.

60
Q

What do grey matter regions IX and X in the spinal cord contain?

A

Regions IX and X, identified as the ventral column/root, contain both motor neurons and interneurons. They consist of several distinct regions located at different heights within the spinal cord.

61
Q

What kind of sensory information do Rexed Laminae I-III in the dorsal columns process?

A

Rexed Laminae I-III process crude touch, pressure, and pain information.

62
Q

How does the sensory input reach these laminae (I-III)?

A

The sensory input travels from dorsal ganglia through Lissauer’s tract to reach Rexed Laminae I-III.

63
Q

What is the primary function of Lamina I (Dorsomarginal nucleus)?

A

Lamina I processes sensations related to crude touch, pressure, and pain, but it does not receive descending projections from the brainstem, so sensations are not modified here.

64
Q

Why does Lamina II (Substantia gelatinosa of Rolando) appear gel-like, and what type of pain sensations does it primarily process?

A

Lamina II appears gel-like due to very low myelin levels. It primarily processes pain sensations from C-fibers, which are slow and result in poorly localized pain.

65
Q

What type of pain sensations are primarily processed in Laminae III/IV (Nucleus proprius)?

A

Laminae III/IV, known as the Nucleus proprius, primarily process pain sensations from A-fibers, which transmit fast and sharp pains.

66
Q

What type of cells are found in Rexed Lamina VII of the spinal cord?

A

Contains sympathetic preganglionic cells (T1-L2/3) and parasympathetic preganglionic cells (S2-S4).

67
Q

How do sympathetic preganglionic cells in Rexed Lamina VII project their signals?

A

Sympathetic preganglionic cells in Rexed Lamina VII project their signals via the white ramus to postganglionic cells in sympathetic ganglia.

68
Q

How do parasympathetic preganglionic cells in Rexed Lamina VII project their signals?

A

Parasympathetic preganglionic cells in Rexed Lamina VII project their signals directly to their target tissues without an intermediate ganglion

69
Q

What types of motoneurons are found in the Ventral Columns of the spinal cord?

A

The Ventral Columns are full of alpha and gamma motoneurons.

70
Q

What is the primary function of large alpha motoneurons in the Ventral Columns?

A

Large alpha motoneurons in the Ventral Columns project to extrafusal fibers (muscle cells) that control the contraction of skeletal muscles.

71
Q

What is the primary function of smaller gamma motoneurons in the Ventral Columns?

A

Smaller gamma motoneurons in the Ventral Columns project to intrafusal fibers that control muscle spindle contraction, supporting and enabling skeletal muscle contraction without initiating it

72
Q

What are the main arteries that supply blood to the spinal cord?

A

The spinal cord is primarily supplied by two posterior spinal arteries along the dorsolateral sulcus and one anterior artery along the ventromedial fissure.

73
Q

How do the vertebral arteries contribute to the vascular supply of the spinal cord?

A

Vertebral arteries branch into radicular arteries and enter each foramen magnum, supplying the anterior and posterior arteries while arborizing into the spinal cord.

74
Q

Why are radicular arteries important for spinal cord blood supply?

A

Radicular arteries are crucial because without them, the anterior and posterior spinal arteries would not supply adequate blood to the spinal cord, ensuring its proper function.

75
Q

What is the significance of the great ventral radicular artery, also known as the artery of Adamkiewicz?

A

The great ventral radicular artery, sometimes present at the L2/3 level, is of particular importance as it serves as a vital supply route for the spinal cord

76
Q

What is Reciprocal Inhibition?

A

A mechanism that prevents antagonist muscles, those that bend joints in opposite directions, from operating at the same time.

77
Q

How does Reciprocal Inhibition work at the neural level?

A

Receptors from one muscle’s spindles create two excitatory connections. One connection projects to alpha motoneurons that innervate the same muscle, resulting in the stretch reflex. The other connection projects to an inhibitory interneuron that synapses on the alpha motoneuron projecting to the antagonist muscle.

78
Q

What is autogenic inhibition or the inverse myotatic reflex?

A

Autogenic inhibition occurs when Golgi Tendon Organs (GTOs) are sufficiently activated by muscle contraction.

79
Q

What is the purpose of autogenic inhibition?

A

To automatically release the muscle if tension becomes too high, acting as a protective mechanism against excessive muscle

80
Q

What triggers the flexor/withdrawal/nociceptive reflex?

A

Triggered by the activation of cutaneous or subcutaneous nociceptors, which are sensory receptors that respond to painful stimuli.

81
Q

How does the flexor/withdrawal/nociceptive reflex work?

A

Works by activating excitatory neurons that make the muscles move away from pain while inhibitory neurons stop unwanted muscle contractions.

82
Q

What is the purpose of the crossed extension reflex?

A

The crossed extension reflex helps maintain balance when a withdrawal reflex is triggered in one leg. It involves communication between both legs to support balanc

83
Q

How do nociceptors contribute to the crossed extension reflex?

A

Nociceptors in the leg that feels pain send signals to make that leg withdraw, and they also send messages through special fibers to the other leg, causing it to stay extended to help maintain balance.

84
Q

What happens in the contralateral leg during the crossed extension reflex?

A

In the other leg, the one not experiencing the pain, the crossed extension reflex works differently. Instead of bending like the painful leg, it actually stays straight to help keep us balanced.

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