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Flashcards in Intro Deck (60)
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1
Q

What are the three parts of the forebrain and what do they do?

A
  1. Cerebrum - 85%: hemispheres and underlying specialist areas
  2. Thalamus - processing centre for sensory information
  3. Hypothalamus - the control centre for ANS
2
Q

What is unique about the hypothalamus?

A

Connected to the pituitary’s so plays a major role in hormonal release

3
Q

Where is the midbrain? Name three things that help compose it

A

The connection between forebrain and hindbrain, located at the topmost part of the brainstem and includes the colliculi, tegmentum and peduncles

4
Q

What are the roles of the 3 parts of the midbrain?

A
  1. Colliculi: audio and visual processing
  2. Tegmentum: plane circulatory
  3. Peduncles: connection between the brainstem and cerebellum
5
Q

What are the three parts of the hindbrain and what are their functions?

A

Pons: connects brain with the spinal chord and cranial nerve nuclei

Medulla oblongata: autonomic vital functions like HR, breathing, sneezing and digestion. Receives afferent pathways which descend from the upper cortex on their way to the spinal cord

Cerebellum: coordination

6
Q

What is so significant about the cortex? Name five major features that rely on this region

A

It is the largest site of neural integration (has the most neural connections)
Attention, perception, awareness, consciousness, memory language

7
Q

What is the difference between white and grey matter and how might communication occur between them?

A

Grey matter on the outside: neuronal cell bodies
White matter on the inside: myelinated axons

Axons descend from the grey matter to the white matter (which is known as corona radiata), they then bunch together in the internal capsule and continue down the brainstem to the spinal cord

8
Q

Name four major subcortical structures

A

Basal ganglia, thalamus, hypothalamus, hippocampus

9
Q

What is a common indicator of frontal-temporal dementia?

A

Personality changes (due to loss of function in the frontal lobe, a region that processes attention, planning, decision making)

10
Q

What are the main roles of the following lobes of the cerebral cortex?

a) occipital
b) parietal
c) temporal

A

a) visual processing
b) sensory processing
c) auditory and advanced visual processing

11
Q

Describe the general structure of the cerebral cortex, why is it like this?

A

There are folds in the cerebral cortex organized into sulci (grooves/depressions) and gyrus (ridges/hills). They increase the surface area and help distinguish important landmarks on the brain’s surface

12
Q

Name four important landmarks that can be visualized on the brain’s surface and their respective functions

A

Precentral gyrus: motor processing

Central gyrus: runs ‘central’ along the top of the brain

Post central gyrus: sensory processing area

Lateral fissure

13
Q

Which gyrus separates the frontal and parietal lobe?

A

Central gyrus

14
Q

Which structures are separated by the lateral fissure?

A

Temporal and frontal lobes of the cerebral cortex

15
Q

What is the corpus callosum and what is its function?

A

A thick bundle of myelinated axons that provides a connection between the R and L halves of the cerebral hemisphere

16
Q

Where might you be likely to see atrophy in the brain in dementia?

A

The hippocampus as it is largely responsible for memory

17
Q

What structures does the spinal cord begin and end with?

A

Begins at the foramen magnum (a large oval opening/foramen in the occipital bone in the skull) to vertebral level L1

18
Q

What lies directly underneath vertebral level L1?

A

The cauda equina; a collection of nerves at the base of the spinal cord (resembles a horse’s tail)

19
Q

Describe the location of the sensory and motor neurones in the spinal cord, how might assess the likelihood of each becoming damaged?

A

Sensory neurones enter the spinal cord dorsally (through the dorsal horns), and motor neurones are ventral

The dorsal and ventral regions of the spinal cord have a different blood supply, so it is possible to assess whether vascular damage (i.e a clot) will affect sensory or motor capabilities

20
Q

What is the role of the meninges? Name its three layers

A

Protective layers

  1. Dura mater
  2. Arachnoid mater
  3. Pia mater
21
Q

Describe the dura mater and its function

A

Has two layers: which connect superiorly to the skull and inferiorly to the arachnoid mater underneath

Thick and tough

Plays a role in venous drainage

22
Q

Name two internal extensions of the dura mater, what is their function?

A

Tentorium cerebelli and falx cerebri; they help maintain the structure of the brain

23
Q

Which aspect of the meninges creates cisterns (spaces for CSF) when enlarged in size

A

The arachnoid space (although CSF lies in the subarachnoid space)

24
Q

Describe the structure of the arachnoid and pia mater

A

Arachnoid: thinner with ‘spidery-like’ protrusions that descend and make contact with the pia mater

Pia: ‘silky covering’ that envelops the contours of the brain and spinal chord

25
Q

What are the two main paired arteries supplying the brain? Which ‘circulations’ do they compose? Which supplies more blood?

A

Vertebral arteries: posterior circulation

Internal carotid: anterior circulation - supplies 80% of of blood

26
Q

Describe the pathway of the internal carotid artery :)

*including the two major arterial branches they give rise to

A
  1. Arises at the bifurcation of the L and R common carotids at C4
  2. Moves superiorly within the carotid sheath and enters the brain via the carotid canal, emerging and coursing superiorly to foramen lacerum
  3. They pass anteriorly through the venous cavernous sinus, and once distal give rise to two major branches
    a) anterior cerebral artery
    b) continues as the middle cerebral artery
27
Q

Which cranial nerves is the internal carotid artery closely related to?

A

CN 3,4,6

28
Q

What do the anterior and middle cerebral arteries supply?

A

Anterior: superior-medial parietal lobes and portions of the frontal lobe

Middle: portions of the frontal lobe and lateral surface of the temporal and parietal lobe

29
Q

Which vessel connects the two anterior cerebral arteries and where does it arise from?

A

The anterior communicating artery that arises from the anterior cerebral artery

30
Q

What does the posterior communicating artery do and where does it arise from?

A

Connects the middle cerebral artery (which makes up the end of the internal carotid) to the posterior cerebral arteries (vertebral)

Arises off the ICA (distal to the cavernous sinus)

31
Q

Describe the pathway of the vertebral arteries

A

L and R vertebral artery aries from the subclavian arteries

  1. they ascend through the posterior part of the neck through holes in the transverse processes called foramen transversarium
  2. They enter the cranial cavity via foramen magnum, and within the cranial vault five off the meningeal branch, spinal arteries (two posterior ones and one anterior one) and the posterior inferior cerebellar
  3. At the lower pons, the R and L CONVERGE to form the basilar artery
32
Q

What can cause pinching of the vertebral arteries on their way up to the brain?

A

Arthritis or any kind of ‘crumbling’ bone condition may pinch the vertebral arteries as they ascend through the foramen transversarium

33
Q

Describe how the spinal arteries supply the spinal cord, where do they arise from?

A

Branches of the vertebral arteries once inside the cranial vault

2 posterior arteries: supply posterior 1/3 of cord
1 anterior artery: supplies anterior 2/3 of cord

34
Q

What are the branches of the basilar artery?

*note the two major ones and other three

A
  1. Posterior cerebral arteries
  2. Posterior communicating arteries
  3. Superior cerebellar arteries
  4. Pontine arteries
  5. Anterior inferior cerebellar (AICA)
35
Q

Name the terminal branch of the basilar artery and what does it supply?

A

Posterior cerebral arteries: supply the occipital lobe, inferior part of the temporal lobe and deep structures

36
Q

Provide a summary of the structures supplied by the following vessels

a) internal carotid
b) vertebral
c) basilar

A

a) Majority of cerebral hemisphere and eye
b) Meninges and cerebellum; including the proximal and inferior parts of the cerebral hemisphere and parts of the occipital and temporal lobes
c) brainstem and cerebellum

37
Q

Describe how the following vessels generally supply the cerebrum

a) ACA
b) MCA
c) PCA

A

Of the anterior cerebrum:

a) anteromedial portion
b) lateral portion

Of the posterior cerebrum:
c) lateral and medial parts

38
Q

Where is the internal capsule and what happens if this region is damaged?

A

It is the white matter within the inferomedial part of each cerebral hemisphere

As you trace finer arteries into the depths of the brain there are more consequences as

a) these are end arteries (such as in the internal capsule)
b) neurons are so tightly packed that a small stroke/bleed can cause extensive irreversible damage
* AND reminder neurons don’t regenerate

39
Q

What kinds of things can compromise arterial supply to the CNS?

A
  1. vessel occlusion: thrombi, emboli
  2. Hemorrhage: burst aneurysm, degeneration of vessel wall
  3. Aneurysm
40
Q

Where do aneurysms tend to occur?

A

At vessel branching sites

41
Q

How common are ischemic vs hemorrhagic strokes and what does each involve?

A

Ischemic strokes: 85%, involve a clot or thrombus occluding an artery

Hemorrhagic: an artery in the brain leaks or bursts
5% bleed around the brain and into the subarachnoid space - causing a subarachnoid hemorrhage
10% bleed into the brain

42
Q

Describe the kinds of paralysis that might be caused by a stroke?

A

Paralysis in…
Hemiplegia: 1 arm and 1 leg on the same side
Monoplegia: 1 arm OR 1 leg
Paraplegia: BOTH legs

43
Q

Describe the kinds of consequences that may arise due to a stroke other than paralysis

A

Cranial nerve dysfunction, aphasia (inability to understand or express speech), memory loss

44
Q

Describe the venous drainage of the cerebrum, cerebellum and brainstem

A

All empty into the dural venous sinuses which ultimately drain into the internal jugular veins

-> Brachiocephalic -> R heart

45
Q

Where are the dural venous sinuses?

A

Between the periosteal and meningeal layers of the dura mater

46
Q

What does the ‘superficial system’ of veins primarily drain? Describe the drainage pathway

A

Drains the cerebral cortex

  1. Superior cerebral veins
  2. Superior sagittal sinus
  3. Straight sinus
  4. Confluence -> Transverse sinus which continues bilaterally until it curves down into the sigmoid sinus which empties into the internal jugular
47
Q

What is the straight sinus a continuation of?

A

The great cerebral vein and inferior sagittal sinus

48
Q

What drains into the cavernous venous sinus and where does it go from there?

A

The middle and inferior cerebral veins + the ophthalmic vein drain into the cavernous sinus

From there blood drains either via the inferior or superior petrosal sinuses to the internal jugular vein (may use sigmoid on its way down)

49
Q

Where are the internal cerebral veins? Describe their venous drainage

A

They are under the corpus callosum and splenium

The great cerebral vein and inferior sagittal sinus drain into the straight sinus -> confluence -> transverse -> sigmoid -> internal jugular vein!

50
Q

What is the splenium?

A

The thickest and most posterior portion of the corpus callosum

51
Q

Describe the locational aspect of the ventricular system of the brain

A

There are four interconnected fluid-filled ventricles

  • 2 lateral ventricles within the cerebral hemisphere
  • a third in the middle
  • a fourth ventricle inferior to the third
52
Q

How do the third ventricle and lateral ventricles communicate?

A

Via the interventricular foramina

53
Q

How do the lateral ventricles change with age?

A

They increase in size

54
Q

What lines each of the brain’s ventricles?

A

Within each ventricle is a…
Choroid plexus; a network of blood vessels
A layer of ependyma; lining of specialized epithelia called ependymal cells which produce CSF

55
Q

What is the structure of ependymal cells and where are they found?

A

Simple cuboidal, line the ventricles and the central canal

56
Q

Describe the pathway of CSF as it cycles to and from the heart and lungs

A
  1. Arterial blood enters the fourth, third and lateral ventricle’s choroid plexus
  2. CSF travels from the lateral ventricles to the third ventricle via the intraventricular foramina
  3. CSF travels from the third to the fourth ventricles through the cerebral aqueduct
  4. CSF travels from the fourth ventricle to the subarachnoid space through the lateral and median apertures and may cycle around the subarachnoid space
  5. Eventually, CSF is absorbed into the arachnoid villi of dural venous sinuses and is returned through venous drainage to the heart and lungs
57
Q

Name three roles of the Blood-brain barrier

A
  1. Prevents neurotransmitters from escaping
  2. Protects the brain from pathogens in the blood
  3. Maintains CNS homeostasis (i.e hormones, nutrients and water)
58
Q

Describe the basic layouts of the Blood-brain barrier and the Blood-CSF barrier

A

Blood-brain barrier:
1. cerebral endothelial cells line the capillary and are connected through TIGHT junctions

  1. BM: consists of the basal lamina of endothelial cells and underneath a basal lamina of astrocytes
  2. Astrocyte pedicles protrude into the BM

Molecules then pass through a layer of ependymal cells that line a ventricle and into the CSF…

Blood-CSF barrier:
1. choroid plexus epithelial cells with fenestrations (more permeable than cerebral endothelial cells) and have microvilli

  1. BM
  2. Endothelium of pia mater capillaries also contain fenestrations -> Blood
59
Q

What molecules are capable of diffusion across the blood-brain barrier and what must be transported across?

A

Diffusion: CO2, O2, water, free forms of steroid hormones

Glucose is transported (GLUT1)

60
Q

What are the circumventricular areas/organs (CVOs)?

A

Areas of the brain without a BBB

LAMP: lamina terminalis, area prostrema, median eminence, posterior pituitary (neurohypophysis)