L3 & L4 - Brain and meninges

Question 1

The brain

Answer 1

Telencephalon - cerebrum

Diencephalon - thalamus and hypothalamus

Mesencephalon - midbrain

Rhombencephalon - cerebellum, pons, medulla oblangata (hindbrain)

Question 2

Cerebrum

Answer 2

80% of the brain’s mass, contains two hemispheres - one left and one right, incompletely separated by longitudinal cerebral fissure

Contains four lobes that partially underlie bones of similar names:
* frontal - at the front
* parietal - between frontal and occipital and above temporal)
* temporal - inferior part
* occipital - posterior part

Question 3

The folds of the brain

Answer 3

Gyri are the folds
Sulci are the grooves
Central sulcus separates frontal and parietal lobes
Lateral sulcus separates frontal and temporal lobes

Question 4

Grey matter in the brain: what is it?

Answer 4

Neuronal cell bodies

Question 5

White matter in the brain: what is it?

Answer 5

Tracts with glial support

Question 6

Frontal lobe: what are the structures present in it?

Answer 6

Precental gyrus - the primary motor area of the cerebral cortex - It lies anterior to the central sulcus

In the dominant hemisphere, Broca’s motor speech can be found
In the non-dominant hemisphere, visual and spatial perception occurs here

Paracentral lobule - found on the medial surface posterior to the central sulcus, it inhibits voiding the bladder and bowels

Prefrontal areas - personality and initiative (phinease gage)

Question 7

Parietal lobe: what are the structures present in it?

Answer 7

Postcentral gyrus - the Primary somatic sensory area of cerebral cortex, it receives afferent pathways for touch, posture and passive movement

Dominant angular gyrus - just above the lateral sulcus and behind the central sulcus
Supramarginal gyrus - just above the lateral sulcus and behind the central sulcus

Dominant lobe - number handling
Non dominant lobe - important for body image
and awareness of external environment

Question 8

Temporal lobe: what are the structures present in it?

Answer 8

Superior temporal gyrus - Auditory cortex

Dominant hemisphere - important for hearing language
Non-dominant - hearing sounds, rhythm
and music

Wernicke’s speech area - superior temporal gyrus

Middle and inferior temporal gyri - learning and memory

Question 9

Occipital lobe: what structures are present here?

Answer 9

Visual cortex is situated in occipital lobe

Question 10

Speech areas in the brain: what are they and what connects them?

Answer 10

In dominant hemisphere - Broca’s area, superior to lateral sulcus and used for expressive/motor
speech

In dominant superior temporal gyrus - Wernicke’s area, ingerior to lateral sulcus, used for perception of language, both spoken and written

arcuate fasciculus is the line connecting them

Question 11

Aphasia: what is it, what occurs in Broca’s and Wernicke’s aphasia, what is conductive aphasia and dysarthria?

Answer 11

Problems with speech

Broca’s aphasia - can perceive language fine but reduced motor speech

Wernicke’s aphasia - struggle to perceive language fine but can do motor speech fine

Conductive aphasia - damage to arcuate fasciculus, repeating what someone has said proves difficult as the communication between the areas struggles

Dysarthria - motor damage to tongue muscle nerves - struggle to articulate

Question 12

Sagittal section of the brain: what can be seen and what do these structures do?

Answer 12

• Corpus callosum - Links the two cerebral hemispheres together
• Thalamus - main sensory relay centre
• Hypothalamus - hormones
• Amygdala - emotional behaviour and memories
• Midbrain - structures involved in initiating movement and affected in parkinsonism, chorea, and schizophrenia
• Dorsal respiratory group - sets rhythm and stimulates muscles of quiet inspiration
• Ventral - respiratory group - involved in forced inspiration and expiration
• Pneumotaxic area (pons) - influences dorsal respiratory group by regulating the duration of inspiration

Question 13

Hindbrain/cerebellum: where is it located in relation to the lobes, what structures do they contain, and what do they do

Answer 13

Separated from the occipital lobe by cerebellar tentorium

Contains two hemispheres and the vermis centrally

Superior, middle, and inferior cerebellar peduncles connect it to the brainstem

Gyri and sulci

Grey and white matter

Fastglial, globose, emboliform, and dentate nuclei in white matter

Question 14

Cerebellum: name three structures that are present and describe their uses (A/P/N)

Answer 14

Archicerebellum (including the flocculonodular lobe) - linked to vestibular nuclei and balance

Palaeocerebellum (vermis, paravermis, globose, and emboliform nuclei) - muscle tone and posture and spinocerebellar tracts

Neocerebellum (most of the cerebellar hemisphere and dentate nuclei) - co-ordination of skeletal muscles

Question 15

DANISH: what is it and what does it stand for?

Answer 15

The typical pathologies of cerebellar impairment

• Dyskinesia - movement problems
• Ataxia - motion issues (google difference between two)
• Nystagmus - orbital muscle issues
• Intention tremor - tremor when initiating movement (skeletal muscle contraction is over-inhibited)
• Slurred speech - Articulation issues
• Hypotonia - Weak,l floppy muscles

Question 16

Pons: where is it located and does it contain any cranial nerves?

Answer 16

‘bridge’ between midbrain and medulla oblangata

Cranial nerves IV-VII

Part of the hindbrain

Question 17

Medulla oblangata: where is it located and does it contain any cranial nerves?

Answer 17

Most inferior structure of the brain stem and is continuous with the pons anteriorly and the spinal cord inferiorly

Contains cranial nerves VIII-XII

Part of the hindbrain

Question 18

The meninges: what is it and what are its layers?

Answer 18

Protective connective tissue layer that surrounds the CNS

Three layers:
* Dura mater
* Arachnoid mater
* Pia mater

Question 19

Meningeal spaces

Answer 19

• Extradural - potential space
• Subdural - potential space
• Subarachnoid space - actual space - contains csf

Question 20

Dura mater: what is it, how do cranial nerves interact with it, and what are its two layers?

Answer 20

Outermost layer - toughest membrane, made of collagenous connective tissue

The dural sheaths of cranial nerves fuse with the dura that surround the brain

• Inner meningeal layer - continuous with spinal dura
• Outer periosteal layer - not found around spinal cord

Question 21

Dural reflections:

Answer 21

Reflection in anatomy - a reflection is when something is modified from its original plane, ie

The dura folding around the spinal dura (? cord?)

Diaphragma sellae - separates brain and stalk of pituitary gland

Cerebella falx - separates the two cerebella hemispheres

Cerebral falx - seperates the cerebellum and cerebrum

Cerebri falx -

Tentorial notch

Cerebellar tentorium - ‘tents’ over the cerebellum, separating the cerebrum and cerebella

Google these

Question 22

Tentorial notch: what can occur when pressure is applied?

Answer 22

Increased intracranial pressure can lead to herniation of the temporal lobe and midbrain through the tentorial notch

This results in oculomotor nerve compression and lateral eye deviation

Question 23

Dural venous sinuses

Answer 23

Between periosteal and meningeal layers of dura

Lined with epithelium

Drain blood from cranial and orbital cavities - drain to internal jugular vein

Contain no valves

Receives tributaries from the brain - orbit, ear, etc

Question 24

Neurovascular dura supply

Answer 24

Arterial Supply: MIDDLE MENINGEAL, internal carotid, vertebral, occipital, maxillary

Venous drainage: MIDDLE MENINGEAL
(joins pterygoid plexus)

Nerve supply: sensory supply from branches of TRIGEMINAL NERVE (V) and cervical nerves C2 and C3 (fibres of cervical nerves may be transferred by CNs X and XII)

Question 25

Pterion: what is it and what occurs when it is fractured?

Answer 25

Location where four bones meet - weak part of the skull

Running deep to the pterion is the middle meningeal artery - damage may pierce the artery and cause intracranial pressure build-up

Question 26

Arachnoid mater

Answer 26

Spider-web structure

Arachnoid granulations - how csf leaves the subarachnoid space into the dural venous sinuses

Delicate
Transparent
Impremeable
Avascular

Question 27

What bridges the subarachnoid space?

Answer 27

arachnoid trabeculae bridge subarachnoid space

Question 28

CSF

Answer 28

Cerebrospinal fluid is found in subarachnoid space

Maintains balance of extracellular fluid in
the brain, provides nutrients for it and cushions it.

Arachnoid granulations (in dural venous sinuses) allow CSF to transfer to venous system

Choroid plexuses of ventricles produce CSF

Question 29

Ventricles

Answer 29

Lateral ventricles (inferior to corpus callosum) drain stuff, then drainage into the Third occurs, and lastly the Fourth ventricle (in posterior part of the pons and medulla) transports CSF through the central canal of the spinal cord

CSF drains to the subarachnoid space from the Fourth ventricle through a single median aperture and paired later apertures

If these ventricles are blocked, they distend and the cerebrum gets compressed

Question 30

Papilloedema: what is it and what causes it?

Answer 30

Swelling of the optical disc

Increased CSF pressure around the optic nerve slows venous return and results inretinal oedema

Question 31

Pia mater

Answer 31

Has a rich vascular supply

Adheres closely to the surface of the brain

Has loose connective tissue membrane

Cerebral veins run on the pia mater within the subarachnoid space