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Brain and Behavior > Neuroanatomy > Flashcards

Neuroanatomy Flashcards

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1
Q

What is the pia and what does it contain?

A

The pia is a thin membrane that covers the contours of the brain. It encloses all but the largest blood vessels which form an anastomotic network over the surface and send fine branches into the underlying cerebrum, brainstem, and spinal cord.

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2
Q

What is the arachnoid and what does it contain?

A

The arachnoid is the middle layer of tissue covering the brain. The space between the arachnoid and the pia is called the subarachnoid space which contains CSF. The large cerebral blood vessels and their major branches also lie within the subarachnoid space.

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3
Q

What is the dura and what is it’s role?

A

The dura is the outer layer of tissue surrounding the brain and is closely adherent to the bone. It is tough and protective of the underlying brain parenchyma.

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4
Q

Label the ventricles and trace the path of circulation of CSF:

A

A: Lateral ventricles

B: Third ventricle

C: Cerebral aqueduct

D: Fourth ventricle

The CSF is produced by specialized secretory epithlia within each ventricle called the choroid plexus. CSF circulates from the lateral ventricles through the foramina of Monro into the third ventricle, through the cerebral aqueduct into the fourth ventricle. It escapes the ventricular system through three apertures in the walls of the fourth ventricle into the subarachnoid space and then bathes the brain and spinal cord. CSF escapes through arachnoid granulations into dural sinuses which drain out of the brain.

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5
Q

What happens if intracerebral flow of CSF is obstructed?

A

Hydrocephalus: expansion of the ventricles can compress and damage the brain tissue

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6
Q

What are the three major types of hematomas?

A
  1. Epidural hematomas: bleeds between the dura and the skull which can be caused by fracture of the pterion which can lacerate the middle meningeal artery (responsible for supplying blood to the meninges)
  2. Subdural hematoma: bleeds underneath the dura which is often caused by shearing injuries (linear or rotational forces) that tear small bridging veins in this space (drain underlying tissue and empty into the dural sinuses).
  3. Subarachnoid hematoma: bleeds beneath the arachnoid which are often caused by rupture of a cerebral aneurysm.
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7
Q

Label the lobes and their major functions:

A

Blue: frontal lobe (executive function, working memory, motor control)

Green: temporal lobe (audition, memory, vision)

Yellow: parietal lobe (language, bodily sensation)

Red: occipital lobe (vision)

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8
Q

What are the sheets of dura that:

a. separate the two hemispheres of the brain
b. separate the cerebellum from the cerebrum

A

a. Falx cerebri
b. Tentorium cerebelli

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9
Q

What are the major venous drainages of the brain? Describe the flow through the dural venous sinuses.

A

The major drainages are the superior and inferior sagittal sinuses which are at the top and bottom of the falx cerebri.

Path of drainage:

  • Inferior sagittal sinus drains to the straight sinus
  • Superior sagittal sinus becomes the right transverse sinus via the confluence of sinuses
  • Straight sinus becomes the left transverse sinus via the confluence of the sinuses
  • Occipital sinus drains to the confluence of the sinuses
  • The confluence of the sinuses splits into right and left transverse sinuses
  • The sphenoparietal sinuses drain to the cavernous sinuses
  • The cavernous sinuses drain to the superior and inferior petrosal sinuses
  • The superior petrosal sinus drains to the transverse sinuses
  • Transverse sinuses drain to the sigmoid sinus
  • The inferior petrosal sinus drains to the sigmoid sinus
  • The sigmoid sinus drains to the internal jugular vein
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10
Q

What is the purpose of arachnoid granulations?

A

They are responsible for recycling CSF back into the venous system via the superior sagittal sinus.

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11
Q

What are the potential spaces within the arachnoid and where are they?

A
  1. Interpeduncular cistern: situated between the two cerebral peduncles
  2. Prepontine cistern: surrounds the ventral aspect of the pons
  3. Quadrigeminal (superior) cistern: situated dorsal to the midbrain
  4. Cerebellomedullary cistern: lies between the cerebellum and the medulla
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12
Q

Which fissue separates the two hemispheres and what major internal structure joins the two hemispheres?

A

a. Longitudinal fissure (where the falx cerebri resides)
b. Corpus callosum: a large commissural band of white matter that connects corticl areas of one hemisphere with functionally similar or symmetrical areas of the other hemisphere

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13
Q

What is the lateral fissure?

A

Also called the Sylvian fissure–it separates the temporal lobe from the frontal and parietal lobes.

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14
Q

What is the central sulcus?

A

A major fissure that separates the frontal lobe and parietal lobe.

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15
Q

What is the “fifth” cerebral lobe and what does it do?

A

The insula is a phylogenetically old cortex with more primitive functions including taste.

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17
Q

The telencephalon becomes the:

A

Cerebral hemispheres, basal forebrain, basal ganglia, hippocampus, and amygdala

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18
Q

The diencephalon becomes the:

A

Thalamus, hypothalamus, epithalamus, and subthalamus

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19
Q

The mesencephalon becomes the:

A

Midbrain

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20
Q

The metencephalon becomes the:

A

Pons and cerebellum

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21
Q

The mylencephalon becomes the:

A

Medulla

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22
Q

What is white matter?

A

Myelinated axons

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23
Q

What is gray matter?

A

Nerve cell bodies

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24
Q

What is a group of cell bodies found in the PNS?

A

Ganglia

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25
Q

What is a group of cell bodies found in the CNS?

A

Nuclei

26
Q

What is a bundle of fibers in the PNS?

A

Nerve

27
Q

What is a bundle of fibers in the CNS?

A

Tract

28
Q

What are sulci and gyri?

A

Inward grooves and outward folds, respectively

29
Q

What colors are bone, CSF, brain matter, and blood on a CT?

A

Bone is white, CSF is black, brain matter is grey, blood is white

30
Q

What color is CSF on an MRI T1 scan? What is this type of scan best for?

A

CSF is black on T1–this scan is best used to demonstrate anatomy.

31
Q

What colors are CSF, grey matter, and white matter on an MRI T2 scan? What is this type of scan best used to demonstrate?

A

CSF is white, grey matter is grey, and white matter is black on a T2 scan–this scan is best used to demonstrate abnormal pathology because fluid and inflammation shows up white.

32
Q

What two signaling molecules/inhibitors are critical for the formation of the neural tube?

A

BMP inhibitors permit development of the nervous system and a Wnt gradient specifies anterior to posterior position along the ectoderm.

33
Q

What is spina bifida?

A

Spina bifida is a defect in vertebral arch formation or neural tube closure which results in an exposure of the spinal cord and its surrounding tissues.

34
Q

What is meroanencephaly?

A

Meroanencephaly is a defect in cranial neural tube closure that results in a partial absence of the brain.

35
Q

What is anencephaly?

A

Anencephaly is a defect in neural tube closure that results in an absence of the brain.

36
Q

What is exencephaly?

A

Exencephaly is a defect in cranial neural tube closure that results in exposure of the brain.

37
Q

What supplement reduces neural tube closure defects?

A

Folic acid

38
Q

Give two examples of segmentation in the developing brain?

A

Formation of the primary/secondary vesicles and formation of the rhombomeres are examples of segmentation along the anterior posterior axis.

39
Q

Which signaling molecule and transcription factor is responsible for the formation of anterior brain structures? What happens if it is missing?

A

Wnt induces otx2 which is a master control gene for all anterior neural structure specification. Anencephaly results if missing.

40
Q

Anterior-posterior patterning in the forebrain is controlled by which signaling molecule and which counter gradient?

A

FGF incudes expression of Pax6 and represses Emx2. Pax6 and Emx2 mutually repress each other and their expression pattern defines neuronal identity in the telencephalon along the A-P axis.

41
Q

Which genes control anterior-posterior axis differentiation in the hindbrain?

A

Hox genes are expressed in an A-P gradient which controls cell differentiation and rhombomere identity in the hindbrain.

42
Q

Which two signaling molecules are responsible for dorsal-ventral patterning of the neural tube?

A

The ectoderm and roofplate secrete BMPs to specify dorsal cells while the notochord and floorplate secrete Shh to specify the ventral cells.

43
Q

What is holoprosencephaly and what can cause it?

A

Holoprosencephaly is a defect in the bifurcation of the forebrain into two lobes which results from a loss of Shh signaling components.

44
Q

What are the two ways of determining cell lineage?

A

Intrinsic: partitioning of cytoplasm Extrinsic: instructive signals from the environment

45
Q

What are the two migratory pathways and fates of neural crest cells?

A

Those that remain near the ectoderm will receive cues to become melanocytes while those that migrate next to the neural tube will be instructed to differentiate into sensory ganglia.

46
Q

How do external cues control cell fate?

A

Different combinations of signals induce different cell fates through the induction of specific transcription factors. Transplantation of neural crest cells from one location to another can alter the fate of their progeny which suggests that environment determines identity.

47
Q

How does the fate of progeny change temporally? (“birth date of cell”)

A

Different cells types are produced along a temporal line based on the transcription factors expressed over time. For example, retinal progenitor cells produce all types of neurons in the eye, ganglion cells first, followed by horizontal cells, then amacrine cells, etc.

48
Q

What is the major pattern of cell migration during population of the cortex? What cell type undergoes this? What is the alternative form of migration?

A

Cells are born in the ventricular zone and migrate out past the final layer of neurons to assume more superficial positions–“inside-out” maturation. Excitatory cells undergo this radial migration while inhibitory cells are produced in the ventral telencephalon (lateral and medial ganglionic eminence) and migrate tangentially into the cortex.

49
Q

Improper migration of excitatory cells can result in what cortical defects?

A

Cortical lamination defects like double cortex and lissencephaly result from improper migration of excitatory cells.

50
Q

Failure to produce inhibitory cells causes:

A

Epilepsy

51
Q

What is the growth cone and what does it respond to?

A

The growth cone is the motile structure at the tip of the neuron which responds to secreted and transmembrane environmental cues.

52
Q

Give examples of common chemoattractants, chemorepulsants, contact attractants, and contract repulsants:

A

Chemoattractants: netrins and semaphorins Chemorepulsants: semaphorins, netrins, and slits Contact attractants: Ig CAMs, cadherins, ECM Contact repulsants: Eph ligands, transmembrane semaphorins, ECM

53
Q

What determines how an axon will respond to environmental signals?

A

Specific receptors for these environmental cues determine how a growth cone will respond to the signaling molecules.

54
Q

Topographic maps are important in brain organization. What are the roles of EphrinAs and EphBs in the tectum and how does this affect axon regeneration?

A

EphrinAs are repellant and are expressed in the posterior tectum so only nasal retinal axons which don’t express the EphA receptor can migrate into this region. EphBs are attractant and are expressed in the ventral tectum so retinal axons expressing ephrinBs are drawn to the ventral tectum.

55
Q

What role do trophic factors play in neuronal survival?

A

Neurotrophins are generated by the target cell and are required for survival of the presynaptic cell. There is a limited amount of neurotrophin so the axons that are larger or arrive sooner survive while those that don’t die by apoptosis, ex: NGF (nerve growth factor), NT-3, GDNF

56
Q

Is all neural circuitry developed prenatally?

A

No, much of the circuitry is not developed until the structure is being used during life. The nervous system takes a long time to mature and many of the same processes that are important in development are important for promoting and limiting plasticity and repair.

57
Q

Questions for thought: Do you think alterations in homeotic gene expression can result in missing or duplicated cranial nerves? What clinical consequences could you imagine if axon guidance in the visual system were not tightly regulated? Do you think disruption of the Shh signaling pathway has its most obvious effects on midline structures?

A

Think about this

58
Q

What is the primary underlying defect in spina bifida?

A

Failure of neural tube closure

59
Q

The navigation of an axon to its appropriate target can involve which of the following: ECM molecules Cell surface receptors Secreted repellent proteins

A

All of the above

60
Q

Lissencephaly results from?

A

Defective cortical cell migration

Brain and Behavior (10 decks)

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