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PHGY 209 > CNS/Sensory II > Flashcards

CNS/Sensory II Flashcards

1
Q

Describe the structure of the spinal cord from inside to outside:

A

Central canal, grey matter, white matter, dorsal and ventral roots/ganglia

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2
Q

What is role of the gray matter in the spinal cord?

A

This is where the neurons are.

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3
Q

What is the role of the white matter in the spinal cord?

A

This is where the axons travel.

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4
Q

How does the structure of grey and white matter vary in the spinal cord as compared to the brain?

A

In the brain, grey is on the outside and white is on the inside. In the spinal cord, white is on the outside of the grey.

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5
Q

What is the role of the central canal in the spinal cord?

A

It is where cerebral spinal fluid (CSF) circulates

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6
Q

What are the two main segments of the grey matter in the spinal cord? Describe their functions.

A

There is the dorsal horn and the ventral horn. The dorsal horn receives sensory inputs, while the ventral horn sends out signals.

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7
Q

What is the difference between the dorsal root and the ventral root of the spinal tract?

A

The ventral roots carry axons from motor neurons in the CNS. The dorsal roots are the way through which afferents send their axons into the dorsal horn.

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8
Q

What is the purpose of the dorsal root ganglion?

A

Carries information about sensory inputs into the spinal cord.

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9
Q

What is the other way that information gets in and out of the CNS aside from the spinal cord?

A

The cranial nerves.

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10
Q

Where are cranial nerves located?

A

They all go into and out of the brain stem except for two: the olfactory nerve and the optic nerve.

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11
Q

Describe the development of the nervous system in week 1.

A

We start as a single cell that divides several times, forming a blastocyst.

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12
Q

Describe the development of the nervous system in week 2.

A

We are still a blastocyst, but an inner cell mass starts developing some structure.

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13
Q

Describe the development of the nervous system in week 3.

A

The inner cell mass of the blastocyst takes on an important structure and forms the embryonic disk. The neural tube starts to form from the disk.

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14
Q

The top of the embryonic disk is called […]

A

The neural plate.

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15
Q

Describe the structure of the neural tube as of week 3 of development. Include the embryonic disk.

A

It consists of the ectoderm on top, the mesodorm in the middle, and the endoderm below. The ectoderm and the mesoderm comprise the embyronic disk.

The neural groove also forms at the top in the ectoderm.

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16
Q

Describe how the neural tube develops during week 4 (start)

A

The ectoderm of the neural plat (the neural groove) forms the neural tube. The neural tube becomes the CNS (and part of the PNS). Some cells also pinch off to form neural crest cells. The mesoderm becomes the dura, which is one of the coverings of the CNS.

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17
Q

The neural crest cells formed during week […] become […]

A

4, PNS

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18
Q

Describe how the neural tube develops during week 4 (end).

A

It develops 3 vesicles on one side that go on to form the forebrain, the midbrain, and the hindbrain.

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19
Q

Describe how the different segments of the neural tube develop into different parts of the CNS.

A

From bottom to top:
The tail side (no vesicles) -> spinal cord
Cavity -> ventricles and central canal
Hindbrain -> cerebellum, medulla, pons
Midbrain -> Midbrain
Forebrain -> Thalamus and cerebral hemispheres

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20
Q

What is the function of the ventricles in the brain?

A

They contain the cerebral spinal fluid.

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21
Q

How much cerebral spinal fluid do the ventricles contain?

A

150 ml

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22
Q

Name the 3 major types of ventricles and their defining characteristics.

A

Lateral ventricles: the largest ventricles
Third ventricle
Fourth ventricle: goes into the central canal of the spinal

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23
Q

How is the cerebrospinal fluid formed?

A

It is produced by the choroid plexus in the four ventricles, but mainly in the two laterial ventricles.

24
Q

What is the rate of production of CSF per day?

A

500 ml/day

25
Q

Name the 3 functions of the CSF.

A
  1. Supports and cushions the CNS, as the specific gravity of the CSF and brain are equal (allows brain to float)
  2. Provides nourishment to the brain
  3. Removes metabolic waste through absorption at the arachnoid villi.
26
Q

What is the composition of the CSF?

A

It is sterile, colourless, acellular fluid that contains glucose.

27
Q

What type of circulation does CSF undergo?

A

Passive circulation (not pumped)

28
Q

Describe the route of CSF to the spinal cord after its production.

A

Starts in the lateral ventrical, where it is produced. Enters the third ventricle through the foramen of monroe. Goes from third ventricle into cerebral aqueduct. Travels through midbrain and ends up in fourth ventricle between brainstem and cerebellum. Continues into the central canal of the spinal cord.

29
Q

When CSF leaves the ventricles, it ends up in […]

A

The subarachnoid space.

30
Q

What is the subarachnoid space?

A

It is the area on the outside of the brain and spinal cord.

31
Q

The CSF can enter the subarachoid space via what 2 methods?

A

Through one of the foramens below the cerebellum or by the arachnoid villi.

32
Q

Name the 3 foramens below the cerebellum that allow the exit of CSF.

A

Two Lushka and one Magendie

33
Q

What are arachnoid villi and where are they located?

A

The arachnoid villi line the very top of the brain right at the midline. Right there, there’s a cavity that contains venous blood (heading back to the heart). The villi are dumping fluid from the arachnoid space into the venous blood supply.

34
Q

What is hydrocephalus?

A

It occurs when there is a problem with CSF circulation, which creates a buildup of intracranial pressure, since the fluid can’t leave. This can compress the brain.

35
Q

What are the 2 types of hydrocephalus? Explain the difference between them.

A

Communicating: there’s a problem on the outside (not with the ventricles), such as with the arachnoid villi.
Noncommunicating: there’s a blockage in one of the four ventricles.

36
Q

What are the 3 meninges of the CNS?

A

From outside to inside: dura mater, arachnoid membrane, pia mater

37
Q

Where are the meninges of the CNS located with respect to skin and bone?

A

They are located below skin and bone.

38
Q

Describe each of the 3 meninges of the CNS.

A

Dura mater: leatherlike piece that covers the CNS
Arachnoid membrane: forms the subarachnoid space
Pia mater: thin membrane stuck to grey matter

39
Q

CSF returns to the blood at the […]

A

Dural sinus

40
Q

Where is the dural sinus located?

A

It is formed by a small space in the dura along the midline

41
Q

Explain the process by which CSF gets mixed back into the blood and returns to the heart.

A

it goes through the arachnoid villi and dumps into the dural sinus.

42
Q

What is the major substrate metabolized by the brain?

A

Glucose

43
Q

The brain needs a constant supply of […]

A

Glucose and oxygen

44
Q

Does the brain require insulin to receive nutrients?

A

No

45
Q

What are the possible consequences of a blood supply interruption to the brain?

A

A few seconds can lead to loss of consciousness. A few minutes can lead to stroke.

46
Q

The brain receives […]% of total blood and is […]% of total mass.

A

15, 2

47
Q

Describe the path that blood takes from the heart to the brain.

A

After being pumped the blood goes through the aorta and can then take one of two paths. First, is can go up through the common carotid artery. Second, it can go up through the smaller vertebral artery. The common carotid artery then splits into an external part, which takes blood to the outside of the head, adn an internal part, which takes blood to the base of the brain. So blood reaches the brain either by the vertebral artery or by the internal carotid artery.

48
Q

How many vertebral arteries and internal carotid arteries do we have?

A

2 of each.

49
Q

Describe the structure of the arteries that carry blood to the brain once arrived at the base of the brain.

A

They come together to form the circle of willis.

50
Q

What is the purpose of the circle of willis?

A

It is a safety feature to allow blood to go to the other side if one side gets blocked (by an artery getting compressed, for example)

51
Q

What is the blood brain barrier?

A

If you want a blood to get into the brain, it has to get past the blood brain barrier, which is formed by capillaries. The capillaries have endothelial cells lining them, but these capillaries form tight junctions. This is unlike the rest of the body, where things can get in and out of the spaces in the capillaries.

52
Q

What types of substances can cross the blood brain barrier?

A

Lipid soluble substances or very small substances. There is also active transport of glucose and some amino acids.

53
Q

Give 3 examples of substances that can pass the blood brain barrier.

A

Alcohol, caffeine, and heroine.

54
Q

Explain why heroine is so harmful.

A

Because it is based on morphine. It crosses the blood brain barrier very quickly, and once it does, it gets converted back to morphine. After this conversion, it can’t cross back and gets stuck in the CNS.

55
Q

What are astrocytes?

A

The astrocytes help the tight junctions in the blood brain barrier. They’re not neurons, but they’re important for regulating the environment in which the neurons operate.

56
Q

Name 3 functions of astrocytes.

A
  • They provide structural support, they take up excess neurotransmitters floating around outside the synapses.
  • They regulate ion concentrations, which is important for the resting membrane potential.
  • They also clean up debris.
57
Q

When travelling up to the circle of Willis, the vertebral arteries unite to form the […]

A

Basilar artery

PHGY 209 (33 decks)

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