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Anatomy > General features of the brain > Flashcards

General features of the brain Flashcards

1
Q

What are the 3 main parts of the brain?

A

Hindbrain - medulla oblongata, pons, cerebellum
Midbrain
Forebrain - cerebral cortex, deep nuclei, basal ganglia, thalamus and hypothalamus, connecting white matter tracts

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2
Q

What are the major planes of the brain?

A

Sagittal - vertical plane passing down the midline
Parasagittal - parallel to sagittal but away from the midline
Medial - close to the sagittal plane
Lateral away from the sagittal plane
Rostral - direction towards the front
Caudal - direction towards the tail
Coronal plane - vertical plane perpendicular to the sagittal plane
Horizontal plane - intersects both the coronal and sagittal planes at right angles
Transverse plane - at right angles to the long axis of the structure (top and bottom halves)

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3
Q

How do location labels differ in the brainstem, spinal cord and cerebral hemispheres?

A

In the brainstem and spinal cord Anterior = Ventral, Posterior = Dorsal
In the cerebral hemispheres Dorsal = superior Ventral = inferior

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4
Q

What is white matter?

A

White matter is formed by collections of nerve fibres (axons and dendrites) with few or no neuronal cell bodies.

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5
Q

What is grey matter?

A

Grey matter of the CNS is formed by aggregations of neuronal cell bodies and their local processes.

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6
Q

What is the neuropil?

A

Within grey matter the felt work of intermingled and interconnected neuronal processes which occupies the space between neuronal cell bodies is called the neuropil.

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7
Q

What is a nuclei?

A

Nuclei or ganglia are a collection of nerve cells within the brain.

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8
Q

What is the cortex?

A

The cortex is the outer surface of the brain and is formed by sheets of neurons.

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9
Q

What are the frontal lobes?

A

Contains primary motor cortex and prefrontal cortex
Involved in motor function, problem solving, spontaneity, memory, language, judgement, impulse control and social and sexual behaviour. Broca’s area (dominant hemisphere only) is found at the inferior frontal gyrus and is important for language production and comprehension.

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10
Q

What are the temporal lobes?

A

Contains primary auditory cortex, auditory association cortex (Wernicke’s area), hippocampus and amygdala
Wernicke’s area is located in the superior temporal gyrus of the dominant hemisphere and is concerned with understanding the spoken word.

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11
Q

What are the parietal lobes?

A

Contains primary somatosensory cortex and association cortex
Extends from the central sulcus anteriorly to the imaginary parieto-occipital fissure posteriorly. The dominant lobe (usually the left) is important for perception, interpretation of sensory information and the formation of the idea of a complex, meaningful motor response.

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12
Q

What are the occipital lobes?

A

Contains theprimary visual and visual association cortex

Located at the posterior aspect of the brain

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13
Q

What is the function of the cerebellum?

A

Motor control of equilibrium, posture and muscle tone and movement coordination

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14
Q

What important structures are part of the brain stem?

A

Ascending and descending tracts, cranial nerve nuclei and the reticular formation

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15
Q

What are the gyri?

A

The rolls of cerebral cortex

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16
Q

What are the sulci?

A

The grooves between the gyri

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17
Q

What is the central sulcus?

A

A large fissure separating the frontal from the parietal lobes

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18
Q

What is the longitudinal fissure?

A

A fissure in the midline separating right and left hemispheres

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19
Q

What is the lateral fissure?

A

A large fissure that separates the temporal lobe from the parietal and frontal lobes

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20
Q

What is the corpus callosum?

A

A large bundle of white matter connecting the two hemispheres

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21
Q

Where do the olfactory tracts run?

A

They run on the inferior surface of the frontal lobes

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22
Q

Where do the optic nerves run?

A

Seen passing backwards and medially converging in the midline to form the optic chiasma, then passing backwards and laterally as the optic tracts

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23
Q

What are the mamillary bodies?

A

Two rounded eminences behind the optic chiasma.

Part of the limbic system and located at the ends of the anterior arches of the fornix.

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24
Q

What are the boundaries of the hypothalamus?

A

Behind the optic chiasma up to and including the mammillary bodies (the only part of the diencephalon visible on the outside of the brain)

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25
Q

What are the crura cerebri of the cerebral peduncles?

A

Two large masses of white matter emerging, behind the mammillary bodies on each side from the cerebral hemisphere. They pass backwards, converging in the midline at the upper border of the pons.

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26
Q

What is the interpeduncular fossa?

A

Space between the crura roofed over by arachnoid

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27
Q

What are the pons?

A

Situated immediately behind the point where the crura meet in the midline. It forms a bridge of neural tissue between the midbrain and the medulla oblongata.

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28
Q

What are the major parts of the cerebellum?

A

Two lobes, one either side of the medulla and a central vermis joining the two hemispheres.

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29
Q

What makes up the limbic system?

A

Limbic system - surrounds the medial margin of the hemisphere.
Includes the hippocampus, fornix, amygdala etc and is involved in emotion, memory, behaviour and olfaction.

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30
Q

What function is the amygdala involved in?

A

Important in motivationally significant stimuli such as those related to fear or reward.
Operates by influencing the endocrine system and the autonomic nervous system and is highly interconnected with the brain’s pleasure centre (the nucleus accumbens - role in sexual arousal and the highs experienced with recreational drugs).

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31
Q

What are the features of the dura mater?

A

2 layers
Outer endosteal layer - lines the interior of the skull adhering to, and sending blood vessels and fibrous processes into the cranial bones
Inner meningeal layer - completely envelopes the CNS, continues as a tube of dura seen around the spinal cord and provides tubular sheaths for the cranial nerves
For the most part, these layers are fused, however in places the inner layer separates to form dural folds which support the subdivisions of the brain and partially the cranial cavity into three areas (right hemisphere, left hemisphere, posterior cranial fossa)

32
Q

What are the dural venous sinuses?

A

A system of communicating blood filled spaces where the dural folds attach to the skull
Clinically the most important sinus is the cavernous sinus.

33
Q

What are the features of the arachnoid mater?

A

This layer encloses the brain loosely following the contour of the meningeal layer of the dura.

34
Q

What are the subarachnoid cisterns?

A

Space exists between the arachnoid and the pia mater, full of CSF. Important in health and disease. Located close to vital structures and disease within the cisterns can lead to significant neurological damage.

35
Q

What are the two major subarachnoid cisterns?

A

Subarachnoid cisterns are named from their positions relative to the brain:
The cerebellomedullary cistern - lies in the angle formed by the dorsal surface of the medulla and the inferior surface of the cerebellum
Cisterna ambiens - group of subarachnoid cisterns which completely encircle the midbrain

36
Q

What is the foramen of magendie?

A

An irregular opening leading to the 3rd ventricle

37
Q

What is the foramen of luschka?

A

Pair of openings lateral to the fourth ventricle. CSF flows from the ventricular system into the subarachnoid space through here.

38
Q

What is the pia mater?

A

Closely adherent to the underlying nervous tissue and is indistinguishable with the naked eye. It forms part of the blood-brain barrier.

39
Q

What is the blood brain barrier?

A

On the surface of the brain the arteries lie in the subarachnoid space.
As vessels pass into the substance of the brain they take with them prolongations of the Pia Mater and some of the subarachnoid space, forming a layer around the vessel.
As the vessel penetrates deeper into the brain tissue the tunica media thins and the prolongation of the subarachnoid space narrows.
At the level of the capillary network, the basement membranes of the endothelial cells and of the pie fuse. The pia acts as a barrier between the circulating blood and the brain tissue (BBB).

40
Q

What is the function of the blood brain barrier?

A

Prevents passage of some substances from the circulation into the nervous tissue.
Retards or prevents the passage of some substances from the circulation into the nervous tissue.

41
Q

What are the 3 contributing elements to the blood brain barrier?

A

Endothelial cells of the capillaries
Basement membrane which lies between the endothelial cells and the astrocytic end-feet (formed from the true basement membrane and the pia)
Astrocytic end-feet themselves

42
Q

What is the falx cerebri?

A

An arched crescent of dura lying in the longitudinal fissure between the cerebral hemispheres

43
Q

What is the tentorium cerebelli?

A

Dura forming a thick fibrous roof over the posterior cranial fossa and the cerebellum

44
Q

Where do the transverse sinuses run?

A

Run along the line of attachment of the tentorium cerebelli to the occipital bone

45
Q

Where is the cavernous sinus located?

A

Lies lateral to the body of the sphenoid

46
Q

Where is the trigeminal cave?

A

Lies next to the apex of the petrous part of the temporal bone and envelops the roots of the trigeminal nerve

47
Q

What is the diaphragma sellae?

A

A small, circular, horizontal fold of dura mater which forms the roof of the pituitary fossa

48
Q

What is the falx cerebelli?

A

A small, vertical, sickle-shaped reflection of dura separating the two lobes of the cerebellum.

49
Q

Where are the cerebral veins and arteries?

A

The arteries and veins on the surface of the brain lie within the subarachnoid space, partially hidden by the arachnoid mater.

50
Q

How can you distinguish between the cerebral veins and arteries?

A

The superficial cerebral veins are easily distinguished by their dark colour - fixed and coagulated blood is visible through the thing, fragile walls.
The arteries look paler, having thicker, muscular walls and not so easily torn.

51
Q

What is the arterial supply to the brain?

A

Arterial blood to the brain arrives within the skull via two pairs of vessels - the internal carotid and the vertebral arteries.
The vertebral arteries provide about 20% of the total supply of the posterior cerebrum and the contents of the posterior cranial fossa.
The internal carotid arteries supply the remaining 80% and supply the anterior and middle parts of the cerebral hemispheres.

52
Q

What is the path of the internal carotid artery?

A

Internal carotid artery arises at the bifurcation of the common carotid at the level of the upper border of the thyroid cartilage and ascends to the base of the skull. It enters the temporal bone to lie in the carotid canal.
The artery pursues a tortuous course, piercing the dura forming the roof of the cavernous sinus to enter the cranial cavity. When it reaches the anterior perforated substance at the medial end of the lateral sulcus it divides into its terminal branches, the anterior and middle cerebral arteries.

53
Q

What does the internal carotid artery divide into?

A

Divides into its terminal branches the anterior and middle cerebral arteries

54
Q

What does the anterior cerebral artery supply?

A

Supplies the corpus callosum and the medial aspects of the hemispheres

55
Q

What does the middle cerebral artery supply?

A

Largest of the terminal branches, supplies the majority of the lateral surface of the hemisphere and the deep structures of the anterior part of the cerebral hemisphere via its anterior perforating branches.

56
Q

What do the anterior and posterior communicating arteries do?

A

Anterior communicating artery - connects together the two anterior cerebral arteries
Posterior communicating artery - connects the internal carotid and vertebro-basilar systems via the posterior cerebral artery

57
Q

Does the internal carotid artery pass through the foramen lacerum?

A

The internal carotid artery does not pass through the foramen lacerum itself. It enters the carotid foramen from below and passes through the petrous part of the temporal bone. It enters the cranium from the end of the carotid canal deep to where the foramen lacerum lies. In a dry skull the end of the carotid canal and the foramen lacerum form a hole from inside to out.

58
Q

What’s the path of the vertebral arteries?

A

The vertebral artery on each side arises from the first part of the subclavian artery. Frequently they are of markedly different diameter on the two sides. They enter the skull through the foramen magnum.
At the lower border of the pons the vertebral arteries unite in the midline to form the basilar artery lying in the anterior median fissure on the pons. The vertebral and basilar arteries, the branches from them and the posterior cerebral artery together are often referred to as the posterior circulation. The anterior and posterior circulation are linked via the Circle of Willis.

59
Q

What is a berry aneurysm?

A

A congenital sac-like outpouching of an intracranial artery. They progressively enlarge until then suddenly rupture resulting in a subarachnoid or intracerebral haemorrhage. Most commonly occur on the branching points around the circle of Willi, particularly the anterior communicating artery that lies in the subarachnoid space.

60
Q

What is a stroke?

A

Either ischaemic or haemorrhagic (intracerebral or subarachnoid haemorrhage). Rapid onset of focal neurological deficit lasting more than 24 hours. (TIA resolve within 24 hours). Third most common cause of death worldwide.

61
Q

What is Amaurosis fugax?

A

Temporary loss of vision to one eye. Part of a carotid plaque breaks off and occludes the central retinal artery. Gives warning of thrombus of the internal carotid artery, potential for impending stroke.

62
Q

What is an extradural haemorrhage?

A

Between the skull and the dura mater. Strips the dura from the bone and compresses the brain. Typically occurs after head injury. Haemorrhage comes from the meningeal arteries.

63
Q

What is a subdural haemorrhage?

A

Blood between the dura and the arachnoid. Appears as a crescent on the CT scan. Typically after a high impact injury e.g. road traffic accident. Haemorrhage is typically a result of tears in the bridging veins. Chronic subdural haemorrhage occurs 4-8 weeks following a mild/moderate head injury in the elderly.

64
Q

What is a subarachnoid haemorrhage?

A

Blood between the arachnoid and pia mater. Occurs after head injury. Traumatic sub arachnoid haemorrhage or after a rupture of a berry aneurysm. Blood surrounds the brain and fills the sulci, predominantly near the site of injury/aneurysm.
Pathognomonic symptom: sudden severe headache, high mortality rate!

65
Q

What is a intracerebral haemorrhage?

A

Rupture of small vessels and microaneurysms in perforating vessels leading to bleeding within the brain tissue. Classical location: internal capsule following rupture of the lenticulostriate artery due to high blood pressure.

66
Q

What is meningitis?

A

Inflammation of the meninges, typically caused by infection. Meningism is the triad of headache, neck stiffness and photophobia. Nausea/vomiting and fever are also present with meningitis. Viral meningitis is often mild and self-limiting, bacterial meningitis requires urgent treatment or will lead to brain damage or death.
The rash associated with bacterial meningitis is a sign of meningococcal septicaemia not meningitis, the infection is in the blood.

67
Q

What are the two types of cerebral veins?

A

Internal cerebral veins - run within the substance of the brain tissue and end when they reach the surface of the brain where they become external cerebral veins.
External cerebral veins - run on the surface of the brain crossing the subarachnoid space to drain into the dural venous sinuses

68
Q

What are the dural venous sinuses?

A

Sinuses connect the major cerebral veins to the internal jugular veins. The major venous sinuses can be easily identified in the attached borders of the falx cerebri, the tentorium cerebelli and also on the floor of the cranial cavity.

69
Q

What is the cavernous sinus?

A

Beside the body of the sphenoid bone contains five cranial nerves and the internal carotid artery. Blood from the face, upper teeth and nasal sinuses can drain into the cavernous sinus. These sites are common areas for infection and the infection can travel down the veins into the cavernous sinus and cause infection in the brain and thrombosis of the cavernous sinus.

70
Q

What is venous sinus thrombosis?

A

Possible causes include: rare complication of childbirth, clotting disorders and ear infection (septic venous thrombosis). Obstruction of venous drainage causes central oedema and a raised intracranial pressure. Resultant brain damage can present as a combination of headache with epileptic seizures, focal motor deficit and deterioration in consciousness.

71
Q

What are the emissary veins?

A

The intracranial venous sinuses and the veins outside the skull communicate via a variable number of emissary veins. These are important because they represent a possible route for infection and inflammation to spread into the cranial cavity from outside the skull.

72
Q

What are the ventricles?

A

The brain develops from a hollow neural tube and it remains hollow as the central spaces form the ventricles. These are important for the production and circulation of the CSF.

73
Q

Where is CSF produced?

A

The majority of the CSF is produced in the choroid plexus, the largest aggregation of choroid plexus is in the lateral ventricles.

74
Q

What is the pathway of the CSF?

A

CSF passes from the lateral ventricles into the third ventricle via the interventricular foramen. It then passes backwards through the cerebral aqueduct into the 4th ventricle. The 4th ventricle communicates with the Subarachnoid Space via the median Foramen of Magendie and the lateral Foramina of Luschka. Through these openings, the CSF passes out to occupy the Subarachnoid Space around the brain and the spinal cord.

75
Q

What is the choroid plexus?

A

The invagination of vessels into the ventricles produces a vascular fold of pia mater covered by an epithelium derived from the ependymal lining of the ventricle; this is the choroid plexus which produces CSF.

76
Q

How is CSF absorbed?

A

Resorption of the CSF into the venous drainage of the brain occurs via tufts of arachnoid mater, called arachnoid villi/granulations. These can be found along the superior sagittal sinus. With advanced age, these villi tend to calcify and can be visible on X-ray. Their presence tends to cause bone to be resorbed along the internal surface of the cranial vault near the midline causing small pit-like structures.

77
Q

What is hydrocephalus?

A

Blockage of CSF flow in ventricles (e.g. tumours) or subarachnoid space (e.g. adhesions following meningitis or trauma) leads to rise in fluid pressure causing the ventricles to swell. Symptoms and signs are of raised intracranial pressure: headaches, unsteadiness and mental impairment. Pressure can be relieved by insertion of a shunt connecting a ventricular system to the peritoneum or jugular vein.

Anatomy (29 decks)

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