Organisation Of Brainstem And Cranial Nerves Flashcards
Definition of brainstem
Part of the CNS, exclusive of the cerebellum, that lies between the cerebrum and spinal cord
What are the 3 major divisions of the brainstem from top to bottom
Midbrain
Pons
Medulla
What is the floor of the 4th ventricle
Pons
Which gland is midline and releases melatonin and is important in circadian rhythm
Pineal gland
What is the superior colliculus important for?
Coordination of head and eye movements at the same time (watching tennis)
What is the inferior colliculus important for?
Auditory reflexes (if there is a loud bang, you will look towards it)
Which cranial nerve emerges from the back of the brainstem
Trochlear nerve (CN IV)
What does the CN IV supply
One of the extrinsic muscles of the eye
Which two main sensory pathways is the dorsal column involved in?
Touch and proprioception
Why is the pons very easy to identify
It has transverse fibres running across it which makes it easy to identify
What is at the top of the midbrain
Optic chiasm- where optic nerves converge
What is immediately behind the optic chiasm
Pituitary stalk (infundibulum)
What is behind the infundibulum
Inferior part of the hypothalamus- mamillary bodies
Which system do mamillary bodies belong to
Limbic system
Which cranial nerve emerges just above the transverse fibres of the pons
Oculomotor nerve (CN III)
What is the function of CN III
Main nerve involved in eye movements
What is the cerebral peduncle
The main motor fibres coming from the motor cortex down to the spinal cord
What is the only cranial nerve that emerges from the lateral part of the pons
Trigeminal (CN V)
What is the function of CN V
Touch and sensation throughout the head and neck
How many cranial nerves emerge at the pontomedullary junction
Three-
• Most medially (the long one in the middle) -Abducens (CN VI)
• Moving laterally (the nerve the arrow is pointing to) -Facial (CN VII)
. Most lateral of the three -Vestibulocochlear (CN VIII)
What is the role of the abducens (CN VI)
Supplies the laterus rectus muscle- last extrinsic muscle of the eye and causes abduction from the midline
What is the role of the facial (CN VII)
Innervates the facial muscles involved in expression
What is the role of the vestibulocochlear (CN VIII)
Involved in balance and hearing
What is Bell’s palsy
Dysfunction of the facial nerve causes a loss of facial muscle tone
What is the role of the glossopharyngeal (CN IX)
Sensory and motor innervation of the tongue and pharynx
What is the role of the vagus (CN X)
Main parasympathetic nerve that projects down into the viscera
What is the role of the accessory (CN XI)
Supplies the sternocleidomastoid (allows turning of the head) and trapezius
What is the role of the hypoglossal (CN XII)
Supplies the musculature of the tongue
What is the point where 90-95% of fibres cross over at the base of the medulla called?
Pyramidal decussation
What are the four functional subtypes of the cranial nerves
General somatic afferent
General visceral afferent
General somatic efferent
General visceral efferent
What is the general somatic afferent for?
Sensation from skin and mucous membranes
What is the general visceral afferent for?
Sensation from GI tract, heart, vessels and lungs
What is the general somatic efferent for?
Muscles for eye and tongue movements
What is the general visceral efferent for?
Preganglionic parasympathetic
Which spinal cord root does information go into and leave from
Enters- Dorsal
Leaves- Ventral
Are motor nuclei for cranial nerves medial or lateral>
Medial, sensory are lateral
What does the midbrain look like
Mickey mouse
What can you see that lets you know that you’re in the midbrain
Cerebral aqueduct
What is the most obvious sign that you’re in the midbrain (dopaminergic neurones)
Substantia nigra
Why is the substantia nigra black?
In normal metabolism, dopaminergic neurones produce neuromelanin which is a pigment that gives its black colour
What is just underneath the cerebellum
The pons- in the region of the 4th ventricle
What are cerebral peduncles for?
Holding cerebrum onto brainstem
What is the main cerebral peduncle?
Middle cerebellar peduncle
Which structure changes a lot as you go down the brain stem
Medulla
What is the main feature of the medulla
Pyramids
What is the inferior olivary nucleus
Bit of a bulge in the side of the medulla- connected to the cerebellum and involved in fine motor movements
At the junction of the medulla with the spinal cord, what is the cross section like?
Very round
What is the smaller dorsal column
Gracilis- sensory information from lower limb
What is the cuneatus
It is more lateral than the gracilis and provides sensory information from the upper limb
What can be seen in the cross section of the lower medulla (2 things)
Central canal and pyramidal decussation
What causes lateral medullary syndrome
Thrombosis of vertebral artery or posterior inferior cerebellar artery
What are the symptoms of lateral medullary syndrome
Vertigo, ipsilateral cerebellar ataxia, ipsilateral loss of pain and Horner’s syndrome
What is Horner’s syndrome?
Loss of sympathetic innervation to head and neck
