IC1- CNS Flashcards

1
Q

What are the 3 parts the brain is divided into?

A

Forebrain, Midbrain and Hindbrain

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2
Q

The forebrain includes? (2)

A
  • Cerebrum
  • Diencephalon
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3
Q

The hindbrain includes? (3)

A
  • Medulla oblongata
  • Pons
  • Cerebellum
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4
Q

The brainstem includes? (3)

A
  • Midbrain
  • Pons
  • Medulla oblongata
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5
Q

How many pairs of cranial nerves and spinal nerves are there?

A
  • Cranial nerves: 12 pairs
  • Spinal nerves: 31 pairs
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6
Q

The cerebrum consists of 2 cerebral hemispheres. What are they separated by?

A

Longitudinal fissure

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7
Q

What are the 4 lobes of the brain?

A
  1. Frontal
  2. Parietal
  3. Temporal
  4. Occipital
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8
Q

The midbrain contains what cranial nerves (2)?

A

III and IV

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9
Q

What cranial nerves are the nuclei associated within the midbrain? (3)

What else are the nuclei associated with within the midbrain?

A

III, IV, V

Also associated with visual and auditory pathways

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10
Q

What are the cranial nerves of the hindbrain? (4)

A

V, VI, VII, VIII

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11
Q

The hindbrain contains which cranial nerves? (4)

A

V, VI, VII and VIII

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12
Q

What cranial nerves are the nuclei associated within the hindbrain? (4)

A

V, VI, VII and VIII

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13
Q

What are the 2 types of cells in the brain? Elaborate.

A

Neurons and non-neuronal cells (glial cells)

Neurons:
- Structural and functional
- Generate/ conduct impulses, are excitable

Non-neuronal cells:
- Non-conducting
- Support and protect neurons
- 10x no. of neurons

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14
Q

Does the cell body of neurons contain a nucleus, golgi complex and mitochondria?

A

Yes

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15
Q

Does the axonal cytoplasm contain ribosomes, RER and Golgi apparatus?

A

No

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16
Q

Describe the function of the fast component (50 - 400mm/day) and slow (1 - 4mm/day) component of the axon

A

Fast component (50 - 400mm/day):
- Transports cytoplasmic proteins and macromolecules required for metabolic and synaptic activity

Slow component (1 - 4mm/day):
- Transports cytoskeleton components down axon

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17
Q

What is the difference between anterograde and retrograde transport?

A

Anterograde transport:
- From cell body to axon

Retrograde transport:
- Waste materials from axon to cell body for removal

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18
Q

Dendrites conduct impulses ___ (toward/away) the cell body?

A

Toward

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19
Q

Compare dendrites to axons in terms of physical features and cellular components

A

Dendrites are relatively short and highly branched. Majority of cytoplasmic components present in dendrites except for Golgi apparatus.

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20
Q

What is the role of dendritic spines?

A

To increase surface area -> increase ability of dendrites to receive more information

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21
Q

The presynaptic membrane contains voltage-gated Ca2+ channels. Describe how an action potential triggers exocytosis of neurotransmitter into synaptic cleft

A
  • Arrival of an action potential at an axon terminal ->
    opening of Ca2+ channels -> influx of Ca2+ ions ->
    rise in the cytosolic Ca2+ level
  • Triggers exocytosis of the neurotransmitter into
    the synaptic cleft
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22
Q

Explain what happens upon binding of neurotransmitter to receptors on excitatory synapse

A

Binding of neurotransmitter
to its receptors -> opening of Na+ channels in the postsynaptic membrane -> depolarization* of the membrane -> action potential in the postsynaptic cell

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23
Q

Explain what happens upon binding of neurotransmitter to receptors on inhibitory synapse

A

Neurotransmitter binding ->
opening of K+ or Cl- channels in the postsynaptic membrane -> hyperpolarization* of the membrane ->
no action potential in the postsynaptic neuron

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24
Q

What receptors are typically found on inhibitory synapses?

A

GABA receptors

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25
Q

What are the 3 types of glial cells in the CNS?

A
  1. Astrocytes (25%)
  2. Oligodendrocytes (60-80%)
  3. Microglia (5-10%)
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26
Q

Function of oligodendrocytes? (1)

A

Myelin sheath formation

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27
Q

Function of astrocytes? (8)

A
  • Blood-brain barrier (regulate composition of intercellular envt and entry of substances into it)
  • Structural support to neurons and ESPECIALLY synapses
  • Scar formation
  • Secretion of nerve growth factors
  • Metabolize neurotransmitters (eg glutamate glutamine shuttle)
  • Tripartite synapse
  • Water transport
  • Excess transport (cerebral edema)
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28
Q

What are the 2 types of astrocytes?

A

Fibrous astrocytes and protoplasmic astrocytes

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29
Q

Difference between fibrous astrocytes and protoplasmic astrocytes?

A

Fibrous astrocytes:
- Primarily in white matter
- Long
- Spindly processes with few branches

Protoplasmic astrocytes:
- Gray matter
- Thick
- Lightly branched processes
- Close to neuron cell bodies

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30
Q

What are the difference in functions of oligodendrocytes in white matter vs gray matter?

A

White matter:
- They are the predominant neuroglial cell
- Product myelin sheath around myelinated fibers in white matter

Gray matter:
- Closely associated with neuron cell bodies, function as satellite cells

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31
Q

What is a cell marker of oligodendrocytes?

A

CNPase

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32
Q

What is the difference between oligodendrocytes in CNS and in PNS?

A

In the CNS, individual
oligodendrocytes myelinate portions of several axons

In the PNS, oligodendrocytes are known as Schwann cells. Individual Schwann cells myelinate
portions of only a single axon

33
Q

What is Nogo-A produced by oligodendrocytes and its function?

A

Nogo-A is a myelin associated neurite-outgrowth inhibitor.

It inhibits axonal regeneration following injury and ischemia in the CNS.

34
Q

Describe microglia

A

Small phagocytic cells that enlarge and
become mobile after injury to the CNS

35
Q

What are the functions of microglia? (5)

A
  • Brain macrophages
  • Immunocompetent
  • Phagocytosis
  • Involved in neuroinflammation: secretes proinflammatory mediators TNF-α, IL-1β
  • Antigen-presentation (MHCII antigen)
36
Q

In what diseases are microglia implicated in?

A

Alzheimer’s disease, Parkinson disease, cerebral ischemia (stroke)

37
Q

What is the marker for microglia?

A

Lectin, OX42 (complement type 3 receptor)

38
Q

What are the 3 connective tissue elements in the peripheral nerve structure?

A
  1. Epineurium
  2. Perineurium
  3. Endoneurium
39
Q

Describe the epineurium

A

Connective tissue surrounding the entire nerve

40
Q

Describe the perineurium

A

A layer of dense connective tissue around each fascicle of nerve fibres

41
Q

Describe the endoneurium

A

A thin, reticular layer that surrounds each individual nerve fibre and contains Schwann cells

42
Q

What do ganglia (located outside CNS) contain?

A

They contain satellite cells and connective tissue elements along with neurons

43
Q

What are satellite cells (amphicytes)?

A

Satellite cells (amphicytes) form a capsule of cells around neuron cell bodies located in peripheral ganglia

44
Q

What are the 2 pairs of arteries that supply blood to the brain?

A
  • Left and right internal carotid arteries
  • Left and right vertebral arteries
45
Q

Where does the vertebral artery originate? How does it enter the skull?

A

Subclavian artery in the neck.
It enters the skull through the foramen magnum

46
Q

The vertebral artery supplies which 3 parts of the nervous system through which 3 arteries?

A

Vertebral artery supplies blood to spinal cord, medulla oblongata and cerebellum.

Via the anterior spinal artery, posterior spinal artery and posterior inferior cerebellar artery.

47
Q

The 2 vertebral arteries join to form a single artery in the midline called?

A

The basilar artery

48
Q

The basilar artery gives off branches to supply which 3 parts? Through which 4 arteries?

A

Basilar artery supplies blood to the pons, cerebellum, and inner ear.

Via the anterior inferior cerebella artery, pontine branches, labyrinthine artery and superior cerebellar artery.

49
Q

The basilar artery ends by dividing into?

A

The 2 posterior cerebral arteries

50
Q

Where does the posterior cerebral artery supply blood to? (4)

A
  1. Midbrain
  2. Medial aspect of occipital lobe
  3. Base of temporal and occipital lobe
51
Q

Where does the internal carotid artery originate from?

How does it enter the skull and where is it situated?

A

The common carotid artery in the neck

It enters the skull through the carotid canals and is situated within cavernous sinus

52
Q

The internal carotid ends by dividing into?

A

The anterior cerebral artery and middle cerebral artery

53
Q

Describe the anterior cerebral artery. (Where and function)

A
  • Passes forward into the medial
    longitudinal fissure and then sweeps back to the parieto-occipital sulcus
  • Supplies most of the medial surface of the hemisphere (except medial aspect of occipital lobe)
54
Q

Describe the middle cerebral artery. (Where and function)

A
  • Pass laterally between temporal and frontal lobes
  • Emerges at lateral fissure, fans out to supply most of the lateral surface of the hemisphere (frontal, parietal, temporal and occipital lobes)
55
Q

What is the Circle of Willis?

A

An anastomosis (connection) between the left and right arteries supplying the brain

56
Q

Benefits of the Circle of Willis?

Limitation of this benefit?

A

Helps to supply blood to the opposite side if there is SLOW occlusion of artery on one side -> allows time for communicating arteries to enlarge and accomodate increased blood flow

Limitation: only works for SLOW occlusion, NOT fast occlusion

57
Q

What does the anterior communicating artery help to connect?

A

Connects the anterior cerebral artery of both sides

58
Q

What does the posterior communicating artery help to connect?

A

Connects the middle cerebral artery with the posterior cerebral artery

59
Q

What medical condition can typically occur at the circle of Willis?

A

Aneurysms (abnormal out-pocketing of wall of a blood vessel) -> which can lead to stroke if it ruptures

60
Q

Where does blood from the superficial part of the superior aspect of the brain drain into?

A

Into the superior sagittal sinus

61
Q

Where does blood from the inferior part of the brain drain into?

A

Into the transverse sinus and superficial middle cerebral vein

62
Q

Where does the superficial middle cerebral vein drains into?

A

The cavernous sinus

63
Q

What is the cavernous sinus closely related to? (hint: includes cranial nerves)

A

Cranial nerves III, IV, V, and VI
and
A part of the internal carotid artery

64
Q

Where does blood from the centre of the brain drain into?

A

The deep cerebral veins which drain into the venous sinus

65
Q

Where does blood at the superior sagittal and straight sinuses flow into?

A

The transverse sinus -> sigmoid sinus -> internal jugular vein of neck

66
Q

How does a subdural hemorrhage occur?

A

When cerebral vein ruptures at the superior cerebral vein as it drains into superior sagittal sinus

67
Q

What is the SSx of subdural hemorrhage? How long does it take to occur and why?

A

SSx: dizziness,
headaches, apathy, falling,
confusion, and drowsiness

Takes weeks to occur as the venous pressure is low hence seepage is low

68
Q

How does the brain capillaries form the BBB?

Function of BBB?

A

Brain capillaries have tight junctions between endothelial cells which form the BBB

BBB prevents the random entry of water soluble substances into the brain parenchyma

69
Q

How are metabolites removed from the brain?

A

By the CSF

70
Q

What produces CSF?

A

A delicate, lacelike structure called the choroid plexus in cerebral ventricles

71
Q

How does CSF travel from the choroid plexus to bathe the brain and spinal cord?

A
  • It flows from the lateral ventricle -> 3rd ventricle, via the cerebral aqueduct -> the 4th ventricle
  • It then flows out of the 4th ventricle to bathe the whole brain and spinal cord
72
Q

How is the CSF absorbed into the superior sagittal sinus?

A

By arachnoid granulations

73
Q

What is the most inferior portion of the brain?

A

Medulla oblongata

74
Q

What are the cranial nerves of the medulla oblongata? (4)

A

IX, X, XI, XII

75
Q

What cranial nerves are the nuclei associated within the medulla oblongata? (5)

What else is the nuclei also associated with in the medulla oblongata?

A

V, IX, X, XI, XII

Also associated with cardiovascular and respiratory function

76
Q

What does the cerebellum consist of?
What is it connected to?

A

A midline portion (vermis) and 2 hemispheres

Connected to the brainstem

77
Q

Where does the spinal cord taper off into?

A

The conus medullaris

78
Q
A