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Gross Anatomy > Gross Anatomy TBL 8 > Flashcards

Gross Anatomy TBL 8 Flashcards

1
Q

Central Nervous System includes (2).

Peripheral Nervous System includes (4)

A
  • Brain and spinal cord

- Cranial nerves, spinal nerves, ganglia, autonomic nerves

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2
Q

Caudal –>
Cranial –>
Dorsal –>
Ventral –>

A

inferior, superior, closer to back, closer to front

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3
Q

Excitable and conductive nerve cells are designated

A

multipolar and pseudounipolar neurons and the single short stem of the pseudounipolar neuron divides into central and peripheral axons

Note psedounipolar because the cell apparently has one process but it is actually two processes. The peripheral axon goes to the cell body which is in the PNS and the the cell body branches back out into the central process that continues into the CNS.

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4
Q

The long peripheral axon of the pseudounipolar conveys (3) from (3).

A

Coveys touch, pain, temperature from bones, muscle, skin of the soma (body) and extremeties.

The information is conveyed to the pseudounipolar neuron residing in the spinal ganglia (Dorsal root ganglia “DRG”)

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5
Q

In the DRG sensory impulses pass from what to what?

A

peripheral to central axon

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6
Q

The central axons of pseudounipolar neurons collectively form?

A

Posterior roots of the spinal nerves, conduct impulses to the CNS and are called afferent nerves (somatic sensory axons).

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7
Q

In the spinal cord axons of the multipolar neurons form what which conducts impulses where and are called what which do what?

A

Anterior roots of the spinal nerves that conduct impulses away from the CNS and are called efferent nerves (somatic motor axons). The efferent voluntarily activate skeletal muscles of the soma (body) wall and extremeties.

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8
Q

Do cranial nerves provide somatic afferent or somatic efferent axons and to where?

A

Provide somatic afferent and efferent to skeletal muscles, bones, and skin of the HEAD and NECK!

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9
Q

Which neurons are affected by Amyotrophic Lateral Sclerosis (ALS) and why is this ultimately fatal?

A

Lou Gerig Disease is a motor neuron disease affecting the efferent nerves (somatic motor axons). The loss of nervous control of skeletal muscles lead to degeneration and atrophy of muscles fibers. The respiratory muscles are ultimately affected and death is due to inability to BREATHE.

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10
Q

Multipolar presynaptic neurons in the CNS and multipolar postsynaptic neurons neurons of the autonomic ganglia in the PNS serially comprise what ? and which contain what?

A

Autonomic nerves which contain visceral efferent axons that innervate organs (aka viscera), glands, and smooth muscle.

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11
Q

Autonomic system consists of what two divisions and what do they regulate?

A

Consists of sympathetic and parasympathetic division that INVOLUNTARILY regulate the viscera, glands, and smooth muscle in a contrasting way, YET COORDINATED manner

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12
Q

Pseudounipolar neurons occupy the DRG and the neurons are enclosed by what? The ganglion (DRG) is enclosed by a protected capsule of what?

A

rings of satellite cells and is enclosed by protective capsule of dense connective tissue.

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13
Q

Neurons of the sympathetic ganglia in the ANS lack?

A

a complete investment of satellite cells

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14
Q

incomplete layer of satellite cells allows presynaptic sympathetic fibers

A

to synapse with the postsynaptic neurons.

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15
Q

In week 3, the CNS originates as what? and what forms the neural tube?

A

As the neural plate, a slipper-shaped thickening of the ectoderm and indentation of the neural plate by the neural groove creates bilateral neural folds.

The free edges of the neural folds constitute the neural crests and the neural tube is formed by fusion of the neural folds.

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16
Q

Neuroepithelium, is derived from? What lines the neural tube?

A

ectoderm and neuroepithelium

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17
Q

As the neural tube differentiates into the spinal cord what forms the presynaptic sympathetic neurons, somatic motor neurons, and somatic interneurons

A

neuroepithelium-derived neuroblasts

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18
Q

During the closure of the neural tube, the neural crest cells migrate where? The migrating neural crest cells form what?

A

Laterally and they form neuroblasts that differentiate into the postsynaptic neurons of the sympathetic ganglia and the sensory neurons of the DRG.

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19
Q

When do neuroblasts lose their ability to divide and what is the clinical consequence of this loss?

A

Neuroblasts (primtive nerve cells) lose their ability to divide once the neuroblasts form. The neuroblast with further develop will become the adult nerve cell or neuron. After injury or degeneration of nerve cell the body has no capacity to proliferate more nerve cells from a neuron.

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20
Q

the gray matter of the spinal cord includes what?

A

the bilateral anterior horns and posterior horns.

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21
Q

Multipolar neurons reside in the gray matter and the surrounding white matter includes the

A

anterior and posterior roots of the spinal nerves.

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22
Q

the 8 cervical, 12 thoracic, 5 lumbar, and 5 sacral spinal segments of the spinal cord are associated with the respective?

A

vertebrae of the vertebral column

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23
Q

The tapering inferior end of the spinal cord is what and where is it positioned?

A

The conus medullaris is positioned between vertebrae L1-L2 in adults.

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24
Q

At what age does the conus medullaris ascend or descend and why?

A

The conus medullaris is between vertebrae L3-L4 at birth and with vertebral column elongation and the onset of erect posture, it ascends to the adult level (L1-L2) at age five.

25
Q

What constitues the cauda equina and how is it similar to the positioning of conus meullaris throughout life?

A

The long roots of the lumbar and sacral spinal nerves which also result (the long roots) from elongation of the vertebral column and the onset of erect posture

26
Q

The closely apposed dura and arachnoid of the spinal meninges are composed of dense or loose connective tissue?

A

Dura –> dense connective tissue

Arachnoid –> loose connective tissue

27
Q

The transparent meningeal pia consists of?

A

2-3 cell layers separated by loose connective tissue, follows the surface contours of the spinal cord.

28
Q

the subarachnoid space is between what two layers. What fluid is found in between and list a fxn of the fluid.

A

the arachnoid an pia mater with CSF which compresses the arachnoid against the dura mater.

29
Q

Where does the duraal sac end in the verterbal column?

A

At Vertebra S2

30
Q

Why is lumbar spinal puncture an important diagnostic tool, and why would different vertebral levels be used for newborn infants and adults?

A

Lumbar Spinal puncture (LP, spinal tap) is the withdrawal of CSF and important Dx tool for evaluating a variety of central nervous system disorders and can also determine if blood is present in the CSF.

In children different because the conus medullaris is between L3-L4 thus you would wish to do a spinal tap below L4.

Note: e.g. meningitis and diseases of CNS may alter the cells in the CSF or chagne the concentration of its chemical constituents.

31
Q

What arteries supply the superior portion of the spinal cord? What supplies most of the spinal cord with blood?

A

The anterior spinal artery and BILATERAL posterior spinal arteries.

The anterior and posterior segmental medullary arteries, which arise from arteries adjacent to the vertebral column

32
Q

What supplies about 2/3 of the spinal cord with blood?

A

The great anterior segmental medullary artery (of Adamkiewicz) i.e. is the largest segmental medullary artery

33
Q

In what space do the spinal arteries and veins reside in and where do the spinal veins drain into?

A

the arteries and veins of the spinal cord reside in the subarachnoid space.

the veins drain into the internal vertebral venous plexus that resides in the epidural space (i.e., the space between the dura and bony vertebral column).

34
Q

What is the clinical consequence of obstructive disease of the great anterior segmental artery (of Adamkiewicz)?

A

Patients may lose all sensation and voluntary movement inferior to the level of impaired blood supply to the spinal cord (parplegia). This is secondary to death of neurons in the part of the spinal cord supplied by the anterior spinal artery.

Note: Deficient blood supply (ischemia) of the spinal cord affects its function and can lead to muscle weakness and paralysis.

35
Q

What precedes the formation of spinal nerves.

A

the somatic sensory axons of the posterior roots and the somatic motor axons of the anterior roots join to form the spinal nerves

36
Q

The vertebral column protects (3)?

A

the sensory roots, DRG, and motor roots

37
Q

The spinal nerves divide into what immediately after emerging from the vertebral column? What do these divisions supply?

A

the spinal nerves divide into posterior and anterior rami (branches)

posterior rami supply the posterior body wall
anterior rami supply the anterolateral body wall and the extremities.

38
Q

central axons from the DRG synapse with multipolar neurons designated interneurons where?

A

in the posterior horn of the spinal cord.

39
Q

axons of the interneurons synapse with?

Most synapses in the CNS occur between

A

the motor neurons in the adjacent anterior horn

axons and dendrites (e.g., axon of the interneuron and dendrites of the motor neuron)

40
Q

How do action potentials conducted along the axon of the interneuron activate the conduction of action potentials along its efferent axon.

What does this activation process allow for a response of (2) things.

A

The AP conducted along the axon of the interneuron stimulate the release of neurotransmitters that bind to the dendrites of the adjacent motor neuron and activate the conduction of action potentials along its efferent axon.

  1. this synaptic activation causes the reflexive contraction of muscles that recoil the hand from the hot iron
  2. some of the activated interneurons contribute to the conduction of action potentials up the spinal cord to activate pain centers in the brain.
41
Q

Where do presynaptic sympathetic neurons reside? Describe the route taken for presynaptic sympathetic neurons.

A
  • presynaptic sympathetic neurons reside in the intermedio-lateral (aka lateral) horns of spinal cord segments T1-L2
  • the presynaptic sympathetic fibers exit the lateral horns to accompany the somatic motor fibers in the anterior roots of spinal nerves T1-L2 and briefly join spinal nerves T1-L2 before synapsing in the sympathetic ganglia.
42
Q

Describe what makes up the paravertebral ganglia

A

the sympathetic ganglia, which are linked along the vertebral column to form bilateral sympathetic trunks or chains, are called para-vertebral ganglia (i.e., the ganglia next to the vertebral column).

43
Q

Note there are ( ) thoracic, ( ) lumbar, and ( ) sacral paravertebral ganglia but only ( ) cervical paravertebral ganglia.

A

12, 5, 5

3

44
Q

Discuss the route of presynaptic to postsynaptic fibers concerning the sympathetic trunk.

A

The presynaptic fibers exit a spinal nerve (either and ONLY from T1-L2). The presynaptic fiber enters the white communicating rami and can travel C1-S5 and synapse with a post sympathetic fiber in a paravertebral ganglia and continues its course in a gray communicating rami. The postsynaptic fiber REJOINS the spinal nerve and can the exit via anterior or posterior ramus.

Note: synapse at sympathetic ganglia can correspond to the level of the presynaptic ganglia or not. The sympathetic ganglia superior to T1 and inferior to L2 provide postysynaptic sympathetic fibers to the corresponding cervical, lumbar, and sacral spinal nerves.

45
Q

Concerning the skin postsynaptic sympathetic fibers innervate (1).

sympathetic-mediated contraction of smooth muscle in the local arteries contributes to?

A
  • innervate the sweat glands in the skin of the body wall and extremities
  • the regulation of blood flow to the body wall and extremities.
46
Q

the somatic motor axons, somatic sensory axons, and postsynaptic sympathetic motor axons are bundled together in the spinal nerves by?

A

sleeves of connective tissue.

47
Q

Perineurium encloses what?
Epineurium binds together what?
Discuss the layers of wrapping in a peripheral nerve.

A

the outer epineurium forms a strong cylindrical sheath around the whole nerve and extends inward to bind bundles (aka fascicles) of the mixed axons together.

  • fascicles are enclosed by perineurium.
48
Q

How does perineum contribute to the blood-nerve barrier?

A

Perineurial cells are modified fibroblasts, most likely of mesenchymal origin, which are linked together by tight junctions and help contribute to a blood brain barrier between highly permeable blood vessels in the exterior of each fasicle and the interior tight capillaries.

49
Q

Why does a cutting nerve injury but not a crushing nerve injury require surgery?

A

If an axon is damaged but the cell body is intact then regeneration and return of function may occur because the entirety of the axon requires the cell body for survival.

  • With crushing injuries usually the cell body and nerve’s connective tissue usually survive/remain intact and the axons distal to the site of compression is damaged but theirs a chance of regeneration and thus does not require surgery. The intact connective tissue guides the regeneration of the axon to their destination.
  • With a cutting nerve injury regeneration is less likely to occur because of the axon separation from the cell body and severed connective tissue. Sprouting may occur at the axon’s proximal end but may not reach its destination. Thus lining of ends and epineurium via sutures is done as best as possible.
50
Q

Note axons are also called?

A

Fibers

51
Q

Are mixed nerve fibers (axons) of the spinal nerves myelinated or unmyelinated? What is the endoneurium made of and where is it positioned?

A

Both. The endoneurium is made of loose connective tissue between the fibers.

52
Q

A continuous series of Schwann cells form myelin sheaths (made of what?) around the longitudinal axes of the fibers.

Define nodes of Ranvier and the Schwann cells and the nodes of Ranvier are invested by what?

A
  • lipoprotein-rich
  • microscopic gaps between the cells
  • a basement membrane.
53
Q

Schwann cells can wrap around a SINGLE axon in a ( ) manner

A

a “jelly-roll-like”

54
Q

Which somatic and sympathetic axons are myelinated (3)?

A
  • somatic motor axons
  • somatic sensory axons that conduct TOUCH sensations
  • presynaptic sympathetic axons
55
Q

Schwann cells can engulf MULTIPLE unmyelinated axons WITHOUT wrapping them with MYELIN SHEATHS. Which somatic and sympathetic axons are unmyelinated?

A
  • somatic sensory fibers that conduct pain and temperature sensations
  • the fibers of interneurons
  • the postsynaptic sympathetic fibers are unmyelinated axons.
56
Q

In the CNS oligodendrocytes envelope multiple or single axon(s) to form myelin sheaths?

Oligodendrocytes engulf un/or -myelinated fibers and do basement membranes invest the oligodendrocytes?

A
  • Multiple up to 60 axons
  • Oligodendrocytes DO NOT engluf unmeylinated fibers
  • Basement membrane DO NOT invest the oligodendrocytes.
57
Q

Why is the speed of impulse conduction faster in myelinated fibers?

A

Myelin acts as an electrical insulator and permits nerve impulses to be transmitted rapidly by saltatory conductance along the nodes of ranvier.

58
Q

How do Schwann cells assist regeneration of damaged nerve fibers?

A

Schwann cells aid debris removal and serves as guides for sprouts of regenerating axons after injury.

59
Q

Why is the histological observation that basement membranes invest Schwann cells but not oligodendrocytes clinically relevant?

A

The absence of a basement membrane (basal lamina) investment of Oligodendrocytes may contribute to relatively poor regeneration after CNS injury.

-Remember induction of cell growth and proliferation are some of the properties of a basement membrane.

Gross Anatomy (3 decks)

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