Lecture 5: Brainstem and Cranial Nerves (I) Flashcards
Brainstem consists of the
Consists of the
midbrain, pons and medulla
Brainstem is positioned between
Positioned between
the forebrain and spinal cord, and connected to the cerebellum dorsally
Brainstem provides a pathway for
Provides a pathway for axonal tracts running between the forebrain, cerebellum and spinal cord
Brainstem is associated with
Associated with 10 pairs of cranial nerves
Ventral =
anterior
Dorsal =
posterior
Cranial nerves - PNS or CNS?
Considered a part of the PNS rather than the CNS as they are considered peripheral nerves
Cerebral peduncles translation
little feet of the cerebrum
Cerebral peduncles other name
crus cerebri
What are the cerebral peduncles?
Collection of axonal tracts that connects one major brain region to another
white matter that connects brainstem to the cerebrum
What do the cerebral peduncles include?
includes axons that descend from the cerebral cortex to the brainstem and spinal cord
(passing longitudinally on the ventral surface of the midbrain)
What does the cerebral peduncle help to do?
help to anchor the cerebrum to the brainstem
III cranial nerve and cerebral peduncles
anterior
IV cranial nerve and cerebral peduncles
posterior
Colliculus define
any of a number of small swellings in the roof of the midbrain, involved in vision and hearing.
Superior cerebellar peduncle associated with
midbrain
Middle cerebellar peduncle associated with
pons
Inferior cerebellar peduncle associated with
medulla
How many mounds make up the mid brain
4 colliculi
What should you find in order to visualise the superior colliculus and the inferior colliculus?
Find the cerebral aqueduct
Superior colliculi =
visual relay & reflex centres
Functions of the superior colliculi
• receive inputs from the retina (anteriorly)/visual cortex (posteriorly going forward) &
project to vision-related areas in cortex
• concerned with the detection of movement of
objects in the visual field - track objects with eyes and to do so need to move eyes therefore muscles of the eye are innervated
• relay vision information to neurons innervating
the muscles that control eye movement
part of the visual pathway therefore relay information and also involved in reflexes
Inferior colliculi =
auditory relay and reflex nuclei
Functions of the inferior colliculi
- relaying auditory information from hearing receptors of the ear to the sensory cortex - in particular on the primary auditory cortex which is the transverse temporal gyrus
- act in reflexive responses to sound (e.g., startle reflex)
Substantia nigra location
located deep to the cerebral peduncle
internal structure in the midbrain
consists of two parts
Substantia nigra contains
contains melanin pigment which is the precursor of dopamine and gives the dark colouring
Function and damage to the substantia nigra
functionally linked to the basal nuclei/ganglia**
dopamine neuron degeneration-Parkinson’s disease - part of the substantial nigra contains dopamine neurons and these die in Parkinson’s disease
Two parts of substantia nigra
pars compacta (SNpc) and pars reticulata (SNpr)
SNpr is ventral/anterior to SNpc
SNpc dopamine neurons are located here
SNpr is between the cerebral peduncle and compacted
SNpr
pars reticulata
SNpc
pars compacta
SNpr has connections similar to ….
SNpr has connections similar to the internal division of the globus pallidus (GPi) = inhibitory input to the thalamus
Red nucleus in relation to substantia nigra
deep to substantia nigra
Why is the red nucleus red?
rich blood supply and contains iron pigment therefore red due to lots of erythrocytes and the presence of iron pigment
Red nucleus function
relay nucleus in some descending motor pathways therefore part of the movement pathway
Cerebral peduncle and red nucleus and substantia nigra named most anterior to most posterior
cerebral peduncle is most anterior then substantia nigra and then the red nucleus
Parts of the midbrain
• Cerebral peduncles • Colliculi (superior colliculi and inferior colliculi) • Substantia nigra • Red nucleus • Cranial nerves - oculomotor (III) - trochlear (IV)
- Cerebral aqueduct
- Superior cerebellar peduncle • Mammillary bodies
Pons - cranial nerves associated
5-8 5 = trigeminal 6 = abducens 7= facial 8=vestibulocochlear
Other structures that the pons is associated with
4th ventricle and middle cerebellar peduncle
Mamillary body is associated with
the hippocampus
What are mammillary bodies in the brain?
The mammillary bodies are a pair of small round bodies, located on the undersurface of the brain that, as part of the diencephalon, form part of the limbic system. They are located at the ends of the anterior arches of the fornix.
Pons composed of
Composed of conduction tracts - both ascending sensory & descending motor tracts
Composed of pontine nuclei e.g. pneumotaxic centre - not only composed of tracts also have specific clusters of neuronal cell bodies called nuclei (pontine nuclei)
Pons (bridge)
fibres forming a bridge from the pons into the cerebellum but also it is a bridge between the cerebrum and going down to the medulla and spinal cord
Pneumotaxic centre (respiratory centre)
Part of the pons, example of pontine nuclei
helps to maintain normal rhythm of breathing
(together with medullary centre ) - groups of neurons controlling breathing in the pons AND the medulla
4th ventricle and pons relationship
4th ventricle is posterior to the pons, 4th ventricle is associated with the pons
Components of the medulla
• Pyramids
• Olives
(these two sit in the medulla)
• Cranial nerves
- glossopharyngeal (IX)
- vagus (X)
- accessory (XI)
- hypoglossal (XII)
• 4th ventricle
• Inferior cerebellar peduncle
(these two are associated with the medulla)