the brain and meninges Flashcards
telencephalon
cerebrum
diencephalon
thalamus and hypothalamus
mesencephalon
midbrain
rhombencephalon
cerebellum, pons, medulla oblongata
cerebrum
- 80% of brains mass
- 2 hemispheres, left and right
- incompletely separated by longitudinal cerebral fissure
4 lobes of the cerebrum
frontal, parietal, temporal, occipital
- partially underlie bones of the same name
cerebral convolutions - gyri and sulci
gyri - the folds
sulci - the grooves
cerebral convolutions - central sulcus
separates frontal and parietal lobe
cerebral convolutions - lateral sulcus
separates frontal and temporal lobe
cerebrum - grey and white matter
grey matter - neuronal cell bodies
white matter - tracts with glial support
frontal lobe
- anterior to central sulcus
- in dominant hemisphere: Broca’s motor speech area
- prefrontal areas: personality and initiative
- non dominant hemisphere - visual and spatial perception
precentral gyrus
primary motor area of cerebral cortex
frontal lobe - paracentral lobule
medial surface posterior to central sulcus
- inhibition of voiding bladder and bowels
parietal lobe
primary somatic sensory area of the cerebral cortex
- receives afferent pathways for touch, posture and passive movement
parietal lobe - dominant and non dominant
dominant lobe - number handling
non dominant lobe - important for body image and awareness of external environment
temporal lobe - superior temporal gyrus
auditory cortex
dominant and non dominant hemisphere of temporal lobe
dominant - important for hearing language
non dominant - hearing sounds, Rhythm, and music
temporal lobe - wernickes area
superior temporal gyrus - in dominant hemisphere
temporal lobe - middle and inferior gyri
learning and memory
occipital lobe
visual cortex is situated in this lobe
Broca’s area
- in dominant hemisphere
- superior to lateral sulcus
- for expressive/ motor speech
Wernicke’s area
dominant superior temporal gyrus
perception of language
aphasia
problems with speech
- Broca’s aphasia
- Wernicke’s aphasia (word salad)
- conductive aphasia
global aphasia
- dysarthria - loss of articulation
conductive aphasia
Conductive aphasia - damage to arcuate fasciculus
- Trouble communicating between wernickes area and broca’s area
corpus callosum
links the 2 cerebral hemispheres together
thalamus
main sensory relay centre
All sensory pathways project neurons to the thalamus
hypothalamus
hormones
amygdala
emotional behaviour
memory
midbrain
structures involved in initiating movement
- affected in Parkinsonism, chorea and schizophrenia
hindbrain - archicerebellum
- balance
- linked to vestibular nuclei
hindbrain - palaeocerebellum
(vermis, paravermis, and globose and emboliform nuclei)
- muscle tone and posture
- spinocerebellar tracts
hindbrain - neocerebellum
coordination of skeletal muscles
typical pathologies resulting from cerebellar impairment
Dyskinesia
Ataxia
Nystagmus
Intention tremor
Slurred speech
Hypotonia
DANISH
hindbrain - pons
- between midbrain and medulla oblongata
contains nuclei of:
- trochlear nerve
- trigeminal nerve
- abducens nerve
- facial nerve
hindbrain - medulla oblongata
- most inferior structure of the brainstem
- continuous with pons anteriorly and spinal cord inferiorly
- contains nuclei of cranial nerves, 8,9,10,11,12
brain - sagittal section
groups of neurons in brain stem that send impulses to muscles of ventilation
dorsal respiratory group
- sets rhythm, 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
the meninges
3 layers:
- dura mater
- arachnoid mater
- pia mater
protective connective tissue membranes that surround the CNS
potential space
- Something which has the potential to become an actual space
- Potential spaces are interesting anatomically because they exist in the body and they formed normally because we have 2 structures, which due to the normal pressures exerted by other structures in the body, are pressed together but aren’t joined together
And if we have an accident or some kind of pathology where something gets introduced into that potential space, it can force those 2 layers apart and form an actual space there
actual space
- E.g. oral cavity
- Ventricles of the heart
Blood vessels
meningeal spaces
extradural space - potential space in the skull
subdural space - a potential space
subarachnoid space - actual space - contains CSF
dura mater
- outermost layer
- toughest membrane
- made of collagenous connective tissue
- the dural sheaths of cranial nerves fuse with the dura that surrounds the brain
layers of cranial dura
- inner meningeal layer: continuous with spinal dura
- outer periosteal layer: not found around spinal cord
dural venous sinuses
the outer layer and the inner layer have split
- Theres a big blue triangle - contains deoxygenated blood
We call these natural separations of the layers of cranial dura, dural venous sinuses
dural reflections
gray sheets of tissue
Dural reflections exist to stabilise the brain
- Sit between parts of the brain to keep them from rotating in the skull
falx cerebri
This dural reflection comes down between your 2 hemispheres to separate them and we call that the falx cerebri
diaphragm sellae
In between the hypothalamus and the pituitary gland there is a diaphragm separating those 2 structures, called diaphragm sellae
falx cerebellar
Posteiror to the vermis - between the vermis and the skull
- Theres another small dural reflection which is called the falx cerebellar
cerebellar tentorium - dural reflection
Separates cerebellum from occipital lobe
- Slopes down and forms a tent over the cerebellum
tentorial notch
increased intracranial pressure can lead to herniation of the temporal lobe and midbrain through the tensorial notch
compresses oculomotor nerve
eyes deviate laterally
dural venous sinuses
between periosteal and meningeal layers of dura
- lined with endothelium
- drain blood from cranial and orbital cavities
- contain no valves
- receives tributaries from the brain, orbit, ear
- drain to internal jugular vein
dural venous sinuses examples
- superior sagittal sinus
- inferior petrosal sinus
- sigmoid sinus
- transverse sinus
- superior sagittal sinus
- cavernous sinus
- superior petrosal sinus
- straight sinus
arterial supply of the dura
middle meningeal, internal carotid, vertebral, occipital, maxillary
venous drainage of the dura
middle meningeal
(joins pterygoid plexus)
nerve supply of the dura
sensory supply from branches of trigeminal nerve and cervical nerves C2 and C3
period
- Area where 4 bones meet- Weak part of the skull
- Might be at risk of damage
- Running deep to the pterion is the anterior part of the middle meningeal artery
○ Might get rupture
○ Could leak into cranial cavity and can’t escape
so Pressure on the brain
arachnoid mater
looks like a spiders web (arachnoid trabecular bridge subarachnoid space
- delicate
- transparant
- impermeable because it contains CSF
- avascular
CSF
- in subarachnoid space
- maintains balance of ECF in the brain, provides nutrients for it and cushions it
- arachnoid granulations allow CSF to transfer to venous system
what produce CSF
choroid plexuses of ventricles produce CSF
ventricles
paired lateral ventricles and single midline 3rd and 4th ventricles
- lateral ventricles inferior to corpus callosum
- inter ventricular foramen from lateral to 3rd ventricle
what is 3rd ventricle surrounded by
thalamus and hypothalamus
what connects 3rd and 4th ventricles
cerebral aqueduct
where is the 4th ventricle
in the posterior part of the pons and medulla
- continuous with central canal of spinal cord (until adulthood)
where does CSF drain from
drains from the 4th ventricle to the subarachnoid space through a single median aperture and paired lateral apertures
- if blocked ventricles distend and cerebrum compressed
what does increasing CSF pressure do
increasing CSF pressure around the optic nerve slows venosu return and results in oedema of the retina
optic disc becomes swollen = papilloedema
pia mater
has a rich vascular supply
- adheres closely to the surface of the brain
- loose connective tissue membrane
- cerebral veins run on the pia mater within the subarachnoid space
