Lecture 6 & 7 - Brainstem & Cranial Nerves Flashcards
Where is the brainstem positioned?
The brainstem is positioned between the forebrain and the spinal cord
Where is the brainstem connected to the cerebellum?
The brainstem is connected dorsally/posteriorly to the cerebellum
How many cranial nerves are associated with the brainstem?
10 pairs of cranial nerves
What is the midbrain comprised of?
The midbrain is comprised of the cerebral peduncles (crus cerebri), colliculi, substantia nigra, red nucleus, cranial nerves (oculomotor and trochlear), cerebral aqueduct, superior cerebellar peduncle, and mamillary bodies
What is the function of the cerebral peduncle?
The cerebral peduncle helps anchor the cerebrum to the brainstem
Where do the axons associated with the cerebral peduncles travel?
The cerebral peduncle includes axons that descend from the cerebral cortex to the brainstem and spinal cord. These axons pass longitudinally on the ventral surface of the midbrain.
What is the other name from the cerebral peduncles?
Crus cerebri
What cranial nerves innervate the cerebral peduncles and where?
The cerebral peduncle is innervated by the III cranial nerves (oculomotor) anteriorly and the IV cranial nerves (trochlear) posteriorly.
What is the general function of the colliculi (as a whole)?
To connect cerebellum to the brainstem
What are the two divisions of the colliculi?
The colliculi are divided into the superior and inferior colliculi.
What is the superior colliculi associated with?
The superior colliculi is associated with visual relay and reflex centres.
What does the superior colliculi do with sensory input?
The superior colliculi receives inputs from the retina and projects it to vision related areas in the cortex
What is the function of the superior colliculi?
The superior colliculi detects the movement of objects in the visual field and relays information to neurons innervating the muscles that control eye movement.
What is the inferior colliculi associated with?
The inferior colliculi is associated with auditory relay and reflex nuclei.
What is the function of the inferior colliculi?
Hearing:
The relay of auditory information from hearing receptors of the ear to the sensory cortex.
Generating reflex response to sound.
Where is the colliculi located?
Posterior to the cerebral aqueduct
Inferior to thalamus
Where is the substantia nigra located?
The substantia nigra is located deep to the cerebral peduncle.
What gives the substantia nigra its colour?
The substantia nigra gets it colour from melanin pigment, a precursor of dopamine.
What is the substantia nigra made of?
The substantia nigra is made of the pars compacta (SNpc) and pars reticulata (SNpr)
What does the SNpr inhibit and why?
The SNpr of the substantia nigra inhibits input to the thalamus as it has connections similar to the internal division of the globus pallidus.
Where is the red nucleus located?
The red nucleus lies deep to the substantia nigra
What gives the red nucleus its colour?
The rich blood supply and iron pigment in the red nucleus gives it its colour
What is the function of the red nucleus?
To act as a relay nucleus in some descending motor pathways
What is associated with the pons?
The pons are associated with 4 cranial nerves (V-VIII), the 4th ventricle, as well as the middle cerebellar peduncle.
What does the pons act as?
The pons acts as a conduit that contains both ascending sensory and descending motor tracts.
What is the pontine nucleus?
The pontine nucleus is a collection of nerves in the pons that makes up the pneumotaxic centre
What is the pneumotaxic centre?
The pneumotaxic (respiratory) centre works together with the medullary centre to maintain normal rhythm of breathing
Where is the pons located?
Superior to the medulla oblongata
Inferior to cerebellum
Anterior/Inferior to 4th ventricle
What is associated with the medulla?
The medulla is associated pyramids, olives, cranial nerves (IX-XII), 4th ventricle, and inferior cerebellar peduncle.
Where are the medulla pyramids and olives located relative to each other?
Pyramids medially
Olives laterally
Describe the axons of the medulla pyramids
The medulla pyramid contains motor axons that are a part of the corticospinal (pyramidal) tract. The axons of the pyramidal tracts, the pyramidal decussation, cross over to the opposite side at the level just above the medulla-spinal junction (at the level of the foramen magnum).
What does the medullary olives contain?
The olives contain the inferior olivary nuclei.
What does the inferior olivary nuclei do?
The inferior olivary nuclei relay the sensory information to the cerebellum
What is found superior to the medulla?
The floor of the 4th ventricle and the superior cerebellar peduncle
What two tracts are found at the medulla?
The fasciculus cuneatus (medial) and the fasciculus gracilis (lateral). These are also known as the dorsal columns in the spinal column.
What is the location of the fasciculus cuneatus and fasciculus gracilis relative to each other?
Fasciculus cuneatus (medial)
Fasciculus gracilis (lateral)
What centres does the medulla have control over?
The medulla has a role of maintaining homeostasis in the cardiovascular centre, respiratory centre, and other reflex centres
What is the role of the medulla in the cardiovascular system?
Cardiac centre - adjusts rate and force of heart beat to meet the body’s needs.
Vasomotor centre - change blood vessel diameter to regulate blood pressure.
What is the role of the medulla in respiratory centres?
The medulla acts on the respiratory centre to control the rate and depth of breathing (along with the pons).
What is the role of the medulla in other reflex centres?
On our other reflex centres, the medulla controls activities such as coughing, sneezing, gagging, swallowing, vomiting, and sweating.
Describe the functional association between the medulla and the hypothalamus
The medullary reticular centres receives input from the hypothalamus and then carries it to target structure(s)
How does cross-sectional anatomy in the medulla differ from that of the spinal cord?
When we reach the medulla, the segmental arrangement of the spinal cord stops. Instead, the columns of white matter become distinct tracts and the grey mater is arranged into distinct nuclei.
What are our cranial nerves?
From most anterior to posterior:
I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlear
V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal
What cranial nerves are associated with the forebrain?
I. Olfactory
II. Optic
What cranial nerves are associated with the midbrain?
III. Oculomotor
IV. Trochlear
What cranial nerves are associated with the pons?
V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear
What cranial nerves are associated with the medulla?
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal
What is the olfactory nerve (1)?
The olfactory nerves (I) are tiny sensory nerves (filaments) that provide our sense of smell
Where do the olfactory nerves run?
The olfactory nerves run from the nasal mucosa and pass-through cribriform plate of ethmoid bone to synapse with the olfactory bulb.
Describe the course of information in the olfactory tract
The olfactory tract receives input from the olfactory receptor cells which collate in the olfactory bulb. From here the tract goes to various parts of the brain.
What parts of the brain does the olfactory tract go to? (5)
Olfactory cortex of the temporal nerve
Hippocampus
Amygdala
Hypothalamus
Reticular formation
What does the optic nerves enable?
Vision
Describe the course of optic tract
The optic nerve axons arise from the retina of the eye. Each optic nerve passes through a hole in the back of our orbit (optic foramen). From here the optic nerves converge to form the optic chiasm and continues on as the optic tracts.
What do nasal retina see?
Temporal visual field
What do the temporal retina see?
Nasal visual field
What does the optic nerve refer to?
Axons of the retinal ganglion cells
What happens at the optic chiasm?
Fibres that originated from nasal retina can cross over to the opposite side
What does the optic tract contain?
contains crossed axons from nasal
retina & uncrossed axons from
temporal retina
What does the lateral geniculate nucleus of the thalamus do?
Processes & relays visual
information to visual cortex