Brain and Cranial Nerves Flashcards
Name the parts of the brain:
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Cerebrum: split into right and left hemispheres
Cerebellum: small part at back/base of brain - fine motor control
Brainstem: midbrain, pons, medulla oblongata –> spinal cord
Label and describe the function of each:
What are meninges?
Name the three layers of membrane, superficial to deep:
Meninges are protective coverings for the brain and spinal cord.
- Dura mater
- Arachnoid mater
- Subarachnoid space
- Pia mater
Give some features of dura mater:
Give some features of arachnoid mater:
What does the subarachnoid space contain?
What is the pia mater?
Dura mater: very tough and fibrous, innervated and vascular, consists of 2 layers: periosteal (in contact with skull) and meningeal (in contact with meninges). These two layers may come apart to form dural venous sinuses
Arachnoid mater: spider web consistency, contain arachnoid granulations which reabsorb cerebral spinal fluid back into venous blood supply
Subarachnoid space contains cerebral spinal fluid (CSF)
Pia mater: follows contours of the brain exactly and coats the blood vessels/nerves entering/leaving the brain
Name the sheaths of dura mater which extend across different parts of the brain:
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- Falx cerebri: sits between left and right cerebral hemispheres
- Tentorium cerebelli: sits between cerebral hemispheres (above) and cerebellum (below)
- Diaphragm selli: sits over sella turcica
Name the two sources of blood supply to the brain and how they enter the brain:
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Vertebral artery: supply posterior part of brain - branch of subclavian artery, travles via transverse foramina of cervical vertebrae and enters cranial cavity via foramen magnum
Both vertebral arteries join together and become the basilar artery
Internal carotid artery: supplies anterior part of brain - branch of common carotid artery, travel within the neck and enter cranial cavity via carotid canal
What is the communication between vertebral and internal carotid arteries referred to as?
Name the arteries involved in this:
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The circle of Willis
- vertebral arteries
- basilar artery
- posterior cerebral artery
- posterior communicating artery
- internal carotid artery
- middle cerebral artery
- anterior communicating artery
- anterior cerebral artery
What do dural venous sinuses do?
Dural venous sinuses drain blood back towards jugular foramen and into internal jugular vein.
How is blood from the brain drained back towards the dural venous sinuses?
Cerebral veins extend directly from brain tissue back towards dural venous sinuses.
Name the system of spaces within the brain and what they are filled with:
What does the system consist of?
What does this fluid do and how is it recycled?
The ventricular system of the brain, filled with cerebro-spinal fluid.
Consists of 4 ventricles/spaces.
Cerebro-spinal fluid protects and nourishes the brain and is recycled via arachnoid granulations into dural venous sinuses, in order to be recycled into venous blood.
Name and describe the different cranial nerve modalities:
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- Somatic sensory nerve fibres: sensory from body wall/skin/mucosa
e. g. mental nerve - Somatic motor nerves: motor nerve to a body wall muscle
e. g. spinal accessory - Parasympathetic: autonomic nervous system - rest and digest
e. g. to glands - mucous, lacrimal, salivary - Special sensory: from organs of special sense
e. g. optic nerve - Mixed: contains a mix of any of the above
e. g. trigeminal nerve - Visceral sensory (afferent): sensory nerve from an organ (from carotid body/sinus, pharynx, larynx)
e. g. glossopharyngeal and vagus nerves
Name the nerve and its associated modalities/function:
a) CN I
b) CN II
c) CN III
d) CN IV
e) CN V
f) CN VI
a) Olfactory - special sensory - smell
b) Optic - special sensory - sight
c) Oculomotor - mixed - somatic motor (eye muscles), parasympathetic (contraction of iris)
d) Trochlear - somatic motor - eye uscle
e) Trigeminal - mixed - somatic sensory (face), somatic motor (muscles of mastication)
f) Abducent - somatic motor - eye muscles
Name the nerve and its associated modalities/function:
a) CN VII
b) CN VIII
c) CN IX
d) CN X
e) CN XI
f) CN XII
a) Facial - mixed - somatic motor (muscles of facial expression), somatic sensory (external ear), special sensory (taste), parasympathetic (sublingual/submandibular glands)
b) Vestibulocochlear - special sensory - hearing and balance
c) Glossopharyngeal - mixed - somatic motor (muscle of pharynx), somatic sensory (posterior 1/3 of tongue), special sensory (taste posterior 1/3), parasympathetic (parotid gland)
d) Vagus - mixed - somatic motor (muscles of palate/pharynx), somatic sensory (ear canal), special sensory (taste), parasympathetic (organs to mid-gut)
e) Spinal accessory - somatic motor - trapezius, sternocleidomastoid
f) Hypoglossal - somatic motor - muscles that control the tongue
Where does crossing over of information occur in the visual field?
Explain how vision is relayed to the brain on the LHS in terms of nasal and temporal parts:
- At the optic chiasm
Nasal part of visual field is perceived by temporal part of retina, which is relayed without crossing over, back towards the brain on the LHS.
Temporal part of visual field is perceived by nasal part of retina and information is crossed over at optic chiasm over onto the opposite side so information on left temporal visual field is perceived by nasal part of retina and crosses over to be perceived by RHS of brain
Which muscles does the somatic motor fibres of oculomotor nerve supply?
Parasympathetic?
Somatic Motor:
- 4 extra-ocular skeletal muscles which control eye movement
- levator palpebral superioris ehich raises eyelids
Parasympathetic:
- sphincter pupillae muscle - responsible for contracting sphincter pupillae which reduces size of pupil –> reducing amount of light entering eye
What is the single muscle the trochlear nerve supplies?
What is a unique feature of this nerve?
The superior oblique muscle, which apsses through the trochlea (pulley)
Only nerve to emerge from the posterior aspect of midbrain
Explain the 3 divisions of the trigeminal nerve:
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Where does the motor root join?
What is unique about this nerve?
- Va: sensory to skin of upper face
- Vb: sensory to skin of mid-face
- Vc: sensory to skin of most of lower face and motor to muscles of mastication
- separate motor root joins with sensory part of Vc at foramen ovale
- only nerve to emerge directly from pons
What single muscle does the abducent nerve supply?
- lateral rectus muscle, located at the junction between the pons and medulla
Name the nerves which pass through each of the fossae:
- Anterior: CN I
- Middle: CN II, III, IV, Va, Vb, Vc, VI
- Posterior: CN VII, VIII, IX, X, XI, XII
What does the trigeminal sensory ganglion contain?
Where does each part of CN V exit?
- all sensory fibres from Va, Vb and Vc join together here and the cell bodies of CN V peripheral sensory neurones are found here
- Va: superior orbital fissure
- Vb: foramen rotundum
- Vc: foramen ovale
What structures are contained within the cavernous sinus?
Deep:
Wall:
Deep contains: CN VI and internal carotid artery
Wall contains: CN III, CN IV and CN Va, Vb
