What is the dorsal surface of the mesencephalon referred to as?
tectum
What is another name for the tectum of the mesencephalon?
quadrigeminal plate
What is the ventral portion of the mesencephalon called?
cerebral peduncle
The tectum is which part of the mesencephalon?
dorsal aspect
What makes up the tectum of the mesencephalon?
4 round swellings called colliculi
How many inferior colliculi are there?
2
Where are the inferior colliculi?
w/in brain (include cell bodies of neurons)
part of tectum of mesencephalon
What pathway are the inferior colliculi involved with?
auditory pathway and auditory reflexes
What do the inferior colliculi do?
relay auditory info to medial geniculate body of thalamus
thalamus receives sensory info to send to cortex so we can hear
What is the posterior side of the thalamus associated with?
pulvinar nuclei
R/L Brachium of inferior colliculi:
lateral structure, contains neurons from inferior colliculi to medial geniculate body
How many superior colliculi are there?
2
Where are the superior colliculi?
w/in the brain
What are the superior colliculi involved with?
visual pathway and visual reflexes
What do the superior colliculi do?
relay visual info to lateral geniculate body of thalamus
R/L Brachium of superior colliculi:
contain neurons for communication b/w superior colliculi and LG body
What does the tectum form?
roof of cerebral aqueduct
Where are most nuclei of the mesencephalon found?
in cranial nerves
What are the two main types of nuclei?
sensory
motor
Where are cell bodies of the initial sensory neurons (1st order) located?
in various ganglia of head and neck
Where are the cell bodies of the 2nd order sensory neurons located?
sensory nuclei of brain stem
1st order and 2nd order sensory neurons synapse where?
somewhere in sensory nucleus
What do the motor nuclei contain?
cell bodies of LMN (alpha and gamma motor nuerons) which are going to exit via cranial nerves and innervate skeletal muscle fibers (extrafusal)--this goes back tot he neuromuscular junction
Where are the cerebral peduncles of the mesencephalon?
ventral structures
Where are the cerebral peduncles in relationship to the cerebral aqueduct?
ventral to cerebral aqueduct
Are the cerebral peduncles a bilateral structure?
yes
What are the 3 major parts of the cerebral peduncles?
crus cerebri
tegmentum
substantia nigra
Where is the crus cerebri?
most ventral portion of peduncle
What does the crus cerebri contain?
corticofugal fibers
Are corticofugal fibers motor or sensory?
motor fibers
Where is the tegmentum of the cerebral peduncles?
most dorsal portion of peduncle
What is the tegmentum?
continuous elongated mass of gray matter extending from upper midbrain caudally through pons and medulla
What does the tegmentum contain?
cranial nerve nuclei and ascending sensory systems
The tegmentum forms the floor of which structure?
cerebral aqueduct
What does the substantia nigra separate?
crus cerebri from tegmentum
What is the substantia nigra?
area of gray matter involved w/ extrapyramidal system
What disease does the substantia nigra deteriorate in?
Parkinson's
What are the structures of the tegmentum of the cerebral peduncle?
motor nucleus of trochlear nerve
tegmental nuclei
mesencephalic nucleus
oculomotor nuclear complex
Edinger-Westphal nucleus
red nucleus
retincular formation
descussation of superior cerebellar peduncles
lateral lemniscus
trigeminal lemniscus
medial lemniscus
spinal lemniscus
medial longitudinal fasciculus (MLF)
What cranial nerve is the motor nucleus of trochlear nerve associated w/?
CN IV
Where is the motor nucleus of trochlear nerve located?
tegmentum
What does the motor nucleus of trochlear nerve innervate?
superior oblique extrinsic eye muscle
Which cranial nerves are found in the midbrain?
3 and 4
Which cranial nerves are found in the pons?
5-8
Which cranial nerves are found in the medulla?
9-12
What is the tegmental nuclei?
small diffuse nuclei
Where is the tegmental nuclei?
surrounding cerebral aqueduct
The tegmental nuclei is part of which system?
limbic system communication
Which cranial nerve is the mesencephalic nucleus associated w/?
CN V
What is the mesencephalic nucleus?
sensory nucleus that technically belongs to CN V (trigeminal)
Where is the mesencephalic nucleus located?
caudal midbrain and rostral pons
What is the mesencephalic nucleus involved with?
proprioceptive pathway of mm of mastication (head, neck, and face)
What does the mesencephalic nucleus receive?
sensory input from muscle spindles
What is the exception of mesencephalic nucleus?
contains cell bodies of 1st order sensory neurons
Only cranial sensory cell bodies 1st order all from NS, normally from:
ganglia
Which cranial nerve is the oculomotor nuclear complex associated with?
CN III
How many nuclear structures does the oculomotor nuclear complex have w/in it?
several
Each extrinsic eye muscle is innervated by which CN?
III
What are the extrinsic eye muscle controlled by the oculomotor nuclear complex?
inferior oblique
medial rectus
superior rectus
inferior rectus
What other muscle does the oculomotor nuclear complex innervate?
levator palpebral superioris
Each eye muscle has its own:
nucleus
Which cranial nerve is associated w/ Edinger-Westphal nucleus?
CN III
What NS is involved with Edinger-Westphal nucleus?
parasympathetic motor nucleus
What type of neuron pathway is the Edinger-Westphal nucleus?
2 neuron pathway
What is a 2 neuron pathway?
pre communicate w/ postganglionic neurons
What is the function of Edinger-Westphal nucleus?
causes pupilla sphincter muscle constriction (part of iris)
innervates ciliary body
Where is the pupilla sphincter muscle?
part of iris
Miosis:
pupil smaller
Where is the ciliary body?
surrounds lens of eye
What does the ciliary body do w/ help of Edinger-Westphal nucleus?
causes shape of lens to change (accommodation)
What is the most conspicuous structure in the midbrain?
red nucleus
What is the red nucleus encapsulated by?
connective tissue
What was the red nucleus histologically?
oval column of cells, tube runs up and down
starts level superior colliculi, extends up into diencephalon
The red nucleus is functionally part of:
extrapyramidal system
The red nucleus communicates w/ what structures as part of extrapyramidal system?
cerebellum
cerebral cortex
basal ganglia
spinal cord
What happens if the red nucleus is damaged?
causes various forms of involuntary skeletal muscle activity
What makes up the reticular formation?
diffuse small nuclei
What does the reticular formation deal with?
sleep
consciousness
alertness
What is the reticular formation involved with?
limbic activity
pain inhibition
refinement of motor activity
What is the decussation of superior cerebellar peduncles?
three sets of peduncles that attach cerebellum to brain stem
What are the three sets of peduncles of the decussation of superior cerebellar peduncles?
superior
middle
inferior
Where are the superior set of peduncles?
attach cerebellum to midbrain
Where are the middle set of peduncles?
attach cerebellum to pons
Where are the inferior set of punduncles?
attach cerebellum to medulla
peduncles have information that cross over in the:
tegmentum of midbrain
What are the lateral lemniscus?
collection of axons (ascending)
The lateral lemniscus is part of what pathways?
ascending sensory pathway
auditory pathway
What does the lateral lemniscus contain?
2nd and 3rd order sensory neurons
Is the trigeminal lemniscus ascending or descending?
ascending
The trigeminal lemniscus is part of:
ascending general sensation pathway of head and neck
What does the trigeminal lemniscus contain?
2nd order sensory neurons
Which cranial nerve does the trigeminal lemniscus belong to?
CN V
Is the medial lemniscus ascending or descending?
ascending
The medial lemniscus is part of:
ascending dorsal column pathway
What does the medial lemniscus contain?
2nd order sensory neurons
Where do the 2nd order sensory neurons of the medial lemniscus originate?
in nucleus cuneatus and nucleus gracilus
What is the medial lemniscus involved with?
conscious proprioception
fine touch
2 point discrimination
discriminative touch
the medial lemniscus is part of:
pathway of which this involvement will ascend
What does damage to the medial lemniscus do?
damages dorsal column pathway
Is the spinal lemniscus ascending or descending?
ascending
What is the spinal lemniscus?
collection of 2nd order sensory neurons of spinothalamic pathway
What does the spinothalamic pathway do?
conduction of:
pain
temperature
proprioception
crude touch
What type of pathways does the medial longitudinal fasciculus have?
ascending sensory pathways
descending pathways
What do the ascending sensory pathways of the medial longitudinal fasciculus control?
eyeball movement
What are the descending pathways of the medial longitudinal fasciculus involved with?
equilibrium reflexes
What are the 3 major descending pathways of the medial longitudinal fasciculus?
tectospinal tract
reticulospinal pathway
medial vestibulospinal tract
Where is the tectospinal tract?
tectum of midbrain
The tectospinal tract descends through what, towards what?
descends through MLF towards spinal cord
What is contained in the tectospinal tract?
auditory and visual reflexes
Where is the reticulospinal pathway?
reticular formation through spinal cord
What is contained in the reticulospinal pathway?
motor activities
Where is the medial vestibulospinal tract?
vestivular system toward spinal cord
What is contained in the medial vestibulospinal tract?
skeletal muscle reflexes
What type of matter makes up the substantia nigra of the cerebral peduncle?
gray matter (cell bodies of neurons)
Where is the substantia nigra located?
b/w crus cerebri and tegmentum
Where does the substantia nigra extend to?
full length of midbrain
Which system is the substantia nigra a part of?
extrapyramidal system
What is the extrapyramidal system involved with?
inoluntary skeletal muscle activity
What does the substantia nigra do?
communicates w/ basal ganglia (dopamine transported to basal ganglia through projection neurons)
What disease is associated w/ the substantia nigra?
Parkinson's disease
Where is the crus cerebri of the cerebral peduncle?
most ventral portion of peduncle
What does the crus cerebri contain?
corticofugla fibers (UMN)
Is the crus cerebri a motor or sensory structure?
motor
What do the corticofugal fibers (UMN) synapse with?
LMN of brain stem (motor nuclei of CNs) or ventral horns of spinal cord.
What do the LMN do?
tell skeletal muscle what to do at NMJ
How is the crus cerebri organized?
somatotopically
How is the crus cerebri sectioned?
lateral third
middle third
medial third
Which of the thirds of the crus cerebri is further divided into three sections itself?
middle
Somatotopic organization of middle 3rd of crus cerebri:
Lateral 3rd of middle 3rd:
corticospinal going to LMN of skeletal muscle of lower extremities (paralysis occurs here if lesion)
Somatotopic organization of Crus cerebri:
Middle 3rd of middle 3rd:
corticospinal fibers on way to LMN innervate skeletal muscle of upper extremities
Somatotopic organization of crus cerebri:
medial 3rd of middle 3rd:
corticobulbar fibers on way to motor nuclei of CN w/ motor functions
Somatotopic organization of crus cerebri:
Lateral 3rd:
occipitaltemporal pontine fibers
occipital pontine: occipital lobe to pons
temporal pontine: temporal lobe to pons
Somatotopic organization of crus cerebri:
Medial 3rd:
Frontopontine fibers: frontal lobe to pons (pass through middle 3rd of crus cerebri)