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Molecular + Cellular Neuro > Neuroanatomical Concepts > Flashcards

Neuroanatomical Concepts Flashcards

1
Q

How do we keep our brains safe? (7)

A
  • Skull (cranium/calvaria)
  • Meninges

Main functions:
1. To provide a supportive framework for the blood vessels of the brain.

  1. To form a series of distinct compartments, that in combination with cerebrospinal fluid (CSF), protect the brain from mechanical injury.
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2
Q

Name what the meninges is made up of (3)

A
  • Dura mater (tough and fibrous)
  • Arachnoid mater (delicate lining of the dura) -> looks like a spider’s web
  • Pia mater (delicate lining adhering to brain) -> looks like clingfilm covering the brain
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3
Q

Explain what is meant by the phrase ‘Brain areas are named after adjacent bones of skull’ (4)

A

Lobes:
Frontal
Parietal
Occipital
Temporal

Bones:
Frontal
Parietal
Occipital
Zygomatic
Mandible
Lacrimal
Maxilla
Nasal
Ethmoid
Sphenoid

important for diagnosing TBI or injuries in general

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4
Q

Define the meninges (1)

A

The meninges are the coverings of the brain.

They protect the brain by housing a fluid-filled space, and they function as a framework for blood vessels

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5
Q

Describe the dura mater compartments (8)

A

Scalp (skin)
Skull
Periosteal dura mater
Meningeal dura mater
Arachnoid dura mater
Subarachnoid space
Pia mater
Cerebral cortex

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6
Q

Summarise the layers of the 3 meninges (6)

A
  1. Dura mater
    * Outermost
    * Tough and fibrous
    * Loose-fitting
  2. Arachnoid mater
    * Beneath the dura
    * Separated by the subdural space
    * Collagenous and translucent
    * Loose-fitting
  3. Pia mater
    * Innermost
    * Separated by the subarachnoid space (blood vessels and
    cerebrospinal fluid)
    * Microscopic thickness
    * Firmly adhered to the surface of the brain and spinal cord
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7
Q

Are the 3 meninges present in the spinal cord? (3)

A

Yes alongside other layers (ventral root of spinal nerve, denticulate ligament, spinal nerve)

Pia mater
Subarachnoid space
Arachnoid mater
Dura mater (protecting the spinal cord)

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8
Q

What are the 2 distinct layers of the dura mater? (3)

A
  • Periosteal (superficial) and meningeal (deep) layers
  • Both layers follow the contours of the internal surface of the skull
  • The meningeal layer invests in and reflects inwards at the cranial sutures creating partitioning ‘walls’ that compartmentalise the brain.
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9
Q

What compartments do the meningeal folds divide the brain into? (4)

A
  • Falx cerebri – divides the cerebral hemispheres (biggest) - VERTICAL
  • Tentorium cerebelli – divides the cerebrum from the cerebellum, creating the supratentorial and infratentorial compartments - HORIZONTAL
  • Falx cerebelli – divides the cerebellar hemispheres
  • Diaphragm sellae – covers the pituitary gland
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10
Q

Describe the dural venous sinuses (3)

A
  • The two layers of the dura mater are separated in certain locations forming spaces called the dural venous sinuses
  • Dural venous sinuses serve as channels for the venous drainage of the brain

The main dural venous sinuses include:
- Superior sagittal sinus.
- Transverse sinus.
- Straight sinus

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11
Q

What does SCALP stand for in a dissected human brain? (5)

A

Layers of the brain:
Skin
Connective tissue (dense)
Aponeurotic layer
Loose connective tissue
Pericranium

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12
Q

Why are the meninges studies so much in regards to physical trauma? (1)

A

Meninges are the 1st and 1 of the easiest areas to become disturbed as a result of trauma and disorders

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13
Q

Name and explain some trauma/infections caused to the meninges (4)

A
  • Meningitis is a disease process where the protective
    layers that cover the brain and spinal cord become inflamed (infection)
  • Meningeal lymphatic dysfunction – TBI : Key role in the clearance mechanism of the brain for tau, amyloid-B, A-syn (injury)
  • Meningioma is the most common a primary brain
    tumour - begins in the brain or spinal cord
  • Classified depending on location, type, extent of spread, genetic findings, and patient age.
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14
Q

is TBI reversible? (3)

A

Mild traumatic brain injury to meninges may be reversible:

-One day after head injury (left), bright dye along the edge of the brain suggests damage (blood leakage) to the meninges, or the brain’s protective lining. After 35 days (right), the dye no longer appears, indicating the meninges may have healed.

-One day after injury (left), vessels in the meninges are
extensively damaged and blood-derived materials leak out
into the surrounding tissue (indicated by the white stain).
Within seven days, blood vessels are rebuilt (area inside
dotted line) and fully functional.

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15
Q

Describe Meningitis in detail, including causes+clinical features (4)

A

A a life-threatening condition in which the pia and arachnoid mater become acutely inflamed

CSF in meningitis shows many neutrophils and numerous microorganisms (bacteria, viruses, fungi)

Causes:
- Sepsis due to a bacterial infection (hemophilus influenzae and
streptococcus pneumoniae)
- Viral infection (varicella-zoster virus and herpes simplex virus) an adverse drug reaction or other systemic diseases.

Clinical features:
* Headache and fever
* Neck stiffness
* Photophobia
- brain is covered in yellowy substance = inflammation

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16
Q

Give an overview of the Cisterns, and its roles (4+1)

A

Cisterns are enlarged subarachnoid spaces that collect cerebrospinal fluid (CSF)

  • Act to cushion the brain
  • Facilitate distribution of neurochemicals
  • Provide a reservoir for CSF
  • Cerebral autoregulation of cerebral blood flow.
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17
Q

Basal Cisterns - Subarachnoid cisterns specifics (5)

A

The subarachnoid cisterns are formed where significant depressions or fissures in the brain are spanned by the arachnoid mater (@ base of brain):

Cisterna magna:
* Located between the cerebellum and the dorsal surface of the medulla.
* CSF flows from the fourth ventricle

Interpeduncular cistern:
* Located at the base of the brain between the two temporal lobes
* Contains the optic chiasm.

Superior cistern:
* Located between the posterior part of the corpus callosum and the cerebellum.

Pontine cistern:
* Contains the basilar artery

18
Q

Name the components and importance of the ventricular system in human brain (4)

A

ventricles = spaces in the centre of the brain:
- lateral ventricle (biggest one)
- 3rd
- 4th (runs down cerebral aqueduct + into cisterna magna)

  • intraventricular foramen (foramen of Monro) -> choroid plexus here too
  • plays a KEY ROLE in CSF circulation
19
Q

Describe Cerebrospinal Fluid (CSF) (5)

A
  • Colourless fluid
  • Contains little protein and few cells
  • Total volume 150 mL (ventricular + subarachnoid) at any one time, 500 mL per day.
  • Produced continuously (active secretion and passive diffusion): lateral -> third -> fourth ventricle
  • CSF is generated in the choroid plexus
20
Q

Explain the Choroid Plexus (6)

A

The choroid plexus acts as a blood-CSF barrier by filtering the plasma from the fluid with the help of epithelial cells.

It is located in the third, fourth and lateral ventricles

-CSF is generated here + secreted via ependymal cells

  • Enters the third and fourth ventricles though the roof
  • Enters the lateral ventricles along the fimbria/fornix

-It is formed by an invagination of the pia mater

-It has a spongy-like appearance

-BVs, small blood vessels (capillaries)

21
Q

How is the CSF maintained in the choroid plexus? (1)

A

An osmotic gradient is maintained by the vascular structure which has the ability to transport oxygen, glucose, sodium, chloride and bicarbonate ions into the ventricles.

22
Q

Explain the arachnoid granulations (6)

A

Arachnoid granulations assist drainage to venous system

  • The CSF is reabsorbed in the venous sinuses (mainly superior sagittal sinus)
  • Reabsorption occurs at the arachnoid villi
  • Arachnoid villi are invaginations of the arachnoid matter through the dura into the lumen of the sinus
  • They allow CSF to exit the subarachnoid space and enter
    the blood stream
23
Q

Summarise the CSF journey (4)

A

Choroid plexus -> lateral v-> 3rd v -> aqueduct -> 4th -> subarachnoid spaces

-> CSF drains into superior sagittal sinus via arachnoid granulations
-> into transverse sinus
-> spinal cord
-> then bought back up + reabsorbed

24
Q

CSF Functions (6)

A
  • Buoyancy -> brain weighs 1.5kg but net weight when suspended in CSF = 25-30g
  • Protection (shock absorber)
  • Prevention of brain ischemia (decreases CSF in limited space in skull = homeostatic control)
  • Homeostasis

*Clearing waste (waste products diffused rapidly into CSF + removed)

  • Neurologic disease biomarkers eg small molecules in CSF from AD patients indicate the diagnosis of AD + it’s stage (via lumbar puncture).
25
Q

What are clinical significant dysfunctions seen with of CSF + it’s clearance mechanism? (4)

A
  • Enlargement or obliteration of cisterns can indicate raised intracranial pressure or mass effect (easily confused by headaches, confusion, shallow breathing increase blood pressure symps)
  • Arachnoid cysts – can develop within cisterns and potentially cause pressure symptoms or hydrocephalus
  • A sample of CSF can be taken via lumbar puncture. This can reveal changes in the intracranial pressure, as well as indicate diseases including infections of the brain or its surrounding meninges.
  • Blood in the cisterns can indicate ruptured cerebral aneurysms or arteriovenous malformations -Subarachnoid Haemorrhage
26
Q

Explain how enlarged ventricles -hydrocephalus comes about + the 4 classifications (1+4)

A
  • Hydrocephalus is a condition where there is an unusual build-up of CSF inside the ventricles inducing an excess of pressure that damages the brain

There are 2 main types of hydrocephalus based on aetiology:

  • Congenital hydrocephalus - present at birth, caused by spina bifida or infections
  • Acquired hydrocephalus - develops after birth, caused by an injury or other diseases

Hydrocephalus can also be divided into:
* Communicating - the ventricles of the brain are still open, and CSF can still flow inside them. However, the CSF can’t flow out of the ventricles because the exits are somehow blocked/narrowed.
* Non-communicating - the flow of CSF along the narrow passages that connect the ventricles is completely blocked

27
Q

Hydrocephalus – Symptoms and
Treatment (3)

A

The main symptoms of hydrocephalus are:
* headache
* nausea (feeling sick)
* vomiting (being sick)
* confusion, and
* problems with vision (for example, blurred or double vision)

Adults with hydrocephalus might also experience:
* balance problems
* poor coordination
* shuffling when they walk
* urinary incontinence (a loss of control passing urine)

treatment:
- drainage of CSF using a shunt system: shunt tube is placed in the ventricles which will allow for the drainage and flow of the excess CSF

28
Q

Define Cerebrovascular diseases (1)

A

A stroke, or cerebrovascular accident, is an emergency
medical condition characterised by a sudden impairment
in arterial blood flow

(brain/part of the brain, experiences a restriction in flow of blood)

29
Q

How might Cerebrovascular diseases come about? (3)

A
  • The ways in which that can happen are a vessel narrowing, a clot forming, a complete blockage, or the rupture of a blood vessel
  • The most common cerebrovascular disorder is a stroke, although other cardiovascular conditions include aneurysms and subarachnoid haemorrhages
  • In 2018, cerebrovascular diseases accounted for 15.4k deaths in the UK, making it the fifth leading cause of death that year
30
Q

Describe the arterial supply of the brain (5)

A

The brain receives blood from 2 sources:
* 2x internal carotid arteries
* 2x vertebral arteries

  • The internal carotid arteries branch to form 2 major cerebral arteries:
    -Anterior cerebral arteries
    -Middle cerebral arteries
  • The right and left vertebral arteries come together (@
    level of the pons) on the ventral surface of the brainstem to form the midline basilar artery
  • The basilar artery joins the blood supply from the internal carotids in an arterial ring at the base of the brain= the circle of Willis
  • The posterior cerebral arteries arise at this confluence,
    as do two small bridging arteries, the anterior +
    posterior communicating arteries.

-end arteries in the brain + the heart -> the blood has nowhere to go

31
Q

Why is the blood supply to the circle of willis important? (1)

A

The two major sources of cerebral vascular supply via the circle of Willis improves the chances of any region of the brain continuing to receive blood if one of the major arteries becomes occluded

32
Q

State what the 3 cerebral arteries innervate (3)

A
  • Most of the lateral surface of the cerebrum is supplied by the middle cerebral artery
  • This artery also feeds the deep structures of the basal forebrain
  • Most of the medial wall of the cerebral hemisphere is supplied by the anterior cerebral artery
  • The posterior cerebral artery feeds the medial wall of the occipital lobe and the inferior part of the temporal lobe
33
Q

Describe and explain the Microvasculature - Capillaries (5)

A
  • The total length of capillaries in the human brain is ~400 miles
  • It is the primary site of oxygen and nutrient exchange= is dependent on the path length + transit time of RBC’s
  • In brain, all capillaries perfused w/blood at all times, and estimated that nearly every neuron in the brain has its own capillary
  • densities of brain capillaries varies sig within the brain depending on location and energy needs w/higher capillary density in grey vs. white matter
  • Pathological, physiological, and environmental states can influence or promote changes in capillary density.eg chronic hypoxia increases capillary density through activation of angiogenic pathways.
34
Q

Describe the Veins of the CNS (8)

A
  • The veins of the CNS drain deoxygenated blood from the cerebrum, cerebellum, brainstem and spinal cord, and empty into the dural sinuses e.g. superior sagittal sinus
  • Most cerebral venous blood flows into the internal jugular veins before it is returned to the heart
  • Veins draining the brain may be divided into superficial and deep veins
  • Deep veins drain the deep structures within the hemispheres – internal structures of forebrain
  • Thalamostriate vein & choroidal vein are the two main deep cerebral veins.
  • They merge into the internal cerebral brain vein on each hemisphere
  • The two internal cerebral veins merge into the great cerebral vein of Galen.
  • The great cerebral vein of Galen is continuous with the straight sinus.
35
Q

Describe Superficial cerebral veins (4)

A
  • Superficial veins lie within the subarachnoid space
  • They drain the lateral surface of the cerebral hemispheres and empty into the superior sagittal sinus
  • The superficial middle cerebral vein runs along the line of the lateral fissure and empties into cavernous sinus
  • The superior anastomotic vein and the inferior anastomotic vein drain into the superior sagittal sinus and transverse sinus
36
Q

Name the main spinal Arteries (3)

A
  • anterior spinal artery
    -posterior spinal artery
    -radicular arteries (supplement anterior and posterior arteries)
37
Q

Name the main spinal Veins (4+1)

A

-anterior spinal vein
-posterior spinal vein
-anterolateral spinal vein
-posterolateral spinal vein

they drain via anterior + posterior radicular veins into internal vertebral venous plexus (epidural venous plexus)

38
Q

Explain the clinical significance of cerebrovascular disease by explaining the causes (4)

A
  • Arterial occlusion by blockage/embolus is often followed by infarction of the part of the brain supplied. Illicit drug abuse is a common cause in younger populations.
  • Thickening (stenosis) of the arteries supplying the brain (carotid or vertebral arteries).

*Cerebral haemorrhage, especially in the basal ganglia, may be caused by hypertension and degenerative changes(amyloidosis).

*An aneurysm at the site of branching of an artery at the base of the brain may cause bleeding into the brain (haemorrhages)

39
Q

Name and explain the different types of haemorrhages (4)

A

Epidural haematoma: bleeding into the epidural + arachnoid mater, above the dura

Subdural haematoma: bleeding below the dura

Subarachnoid haemorrhage: bleeding into the subarachnoid space

Intracerebral haemorrhage: bleeding directly into the brain/ cerebral hemispheres

40
Q

Summary (7)

A
  1. The protective coverings of the brain within the skull include the dura mater, arachnoid mater and pia mater
  2. There are four cisterns within the brain: two lateral ventricles, a third and fourth ventricle, all of which are interconnected
  3. The CSF provides buoyancy and nutrients
  4. There are four arteries supplying blood to the brain, two carotid and two vertebral arteries. Together these form an anastomosis at the base of the brain which helps to ensure equal pressure in the vasculature
  5. Deoxygenated blood drains from the brain via superficial and deep veins which drain into sinuses, the largest of which is the superior sagittal sinus. Venous blood drains into the jugular vein where it flows to the heart and is reoxygenated in the lungs
  6. CSF may be obtained via lumbar puncture and may contain biomarkers of neurologic disease and infection
  7. Damage or disease to the blood supply to the brain may cause haemorrhage or ischemia and have sudden clinical consequences which require prompt attention to avoid irreversible brain damage.

Molecular + Cellular Neuro (21 decks)

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