L5 Flashcards
what are the structures in the brain stem
the midbrain, pons and medulla
where is the brainstem located
between the forebrain and the spinal cord. it is also connected to the cerebellum dorsally
what is the function of the brain stem
it provides a pathway for axonal tracts running between the forebrain, cerebellum and spinal cord
what structures are associated with the brainstem
the 10 pairs of cranial nerves
are the cranial nerves part of the CNS or the PNS
the are peripheral nerves therefore they are part of the PNS
the cerebral peduncles (or crus cerebri) are part of what brainstem structure
the midbrain
cerebral peduncles are cuolquly known as….
the little feet of the cerebrum
what are the cerebral peduncles
they are white matter tracts (axons) that descend from the cerebral cortex to the brainstem and spinal cord
these pass logitudional through the ventral surface of the midbrain which gives it a stripy appearance
what is the role of the cerebral peduncles
they help anchor the cerebrum to the brainstem
the midbrain contains 2 cranial nerves. which are these
the 3rd (anteriorly) and the 4th (posteriorly)
what are the colliculi
they are 2 pairs of mounds on the 4th cranial nerve
what are the names of the colliculi of the 4th crainial nerve
the superior colliculis and the inferior colliculus
these can also be known as the higher and lower hill
there is a superior, middle and inferior cerebellar peduncle. where are theses located
superior is the midbrain
middle is the pons
inferior is the medulla
what is the superior colliculis involved in
it is the visual relay and reflex centre
concerned with the detection of movement of
objects in the visual field
it relays vision information to neurons innervating
the muscles that control eye movement
what is the inferior colliculis involved in
it is the auditory relay and reflex nuclei
relaying auditory information from hearing
receptors of the ear to the sensory cortex
act in reflexive responses to sound (e.g., startle reflex)
what is anterior to the superior and inferior colliculis
the cerebral aqueduct
where does the superior colliculis receive inputs from
the retina/visual cortex
where does the superior colliculis project to
project to vision-related areas in cortex
what colour is the substantia nigra. why
black because it contains melanin pigment which is the precursor of dopamine
where is the substantia nigra located
deep to the cerebral peduncle
what structure is the substantia nigra functionally linked to
the basal ganglia/nuclei
what causes Parkinson’s disease
dopamine neuron degeneration
what are the 2 parts of the substantia nigra
pars compacta (SNpc)
pars reticular (SNpr). this is ventral to SNpc
which part of the substantia nigra contains the dopamine neurons
pars compacta (SNpc)
which part of the substantia nigra acts as the break for unwanted movement
pars reticular SNpr
how does pars reticular (SNpr) act as a brake for unwanted movement
SNpr has connections similar to the internal division of the globus pallidus (GPi) therefore it causes inhibitory input to the thalamus
where is the red nucleus located
it lies deep to the substantia nigra
why is the red nucleus known as the red nucleus
it has a rich blood supply and contains ion pigment
what is the function of the red nucleus
it is a relay nucleus in some descending motor pathways
what is the name of the 3rd cranial nerve
oculomotor
what is the name of the 4th cranial nerve
trochlear
what are the structures of the midbrain
Cerebral peduncles
Colliculi
- superior colliculi
- inferior colliculi
Substantia nigra
Red nucleus
Cranial nerves
- oculomotor (III)
- trochlear (IV)
Cerebral aqueduct
Superior cerebellar peduncle
Mammillary bodies
what are the mammillary bodies
the are related to the hippocampus
what cranial nerves extend from the pons
5, 6, 7, 8
the trigeminal
abducens
facial
vestibulocochlear
what structures are part of the pons
trigeminal, abducens, facial and vestibulocochlear cranial nerves
the 4th ventricle
and the middle cerebellar peduncle
what is the pons composed of
conduction tracts - both ascending sensory and descending motor tracts
it is also composed of pontine nuclei
what is an example of a pontine nuclei
the pneumotaxic centre
also known as the respiratory centre
what is the role of the pneumotaxic centre
it helps to maintain normal rhythm of breathing
it does this together with the medullary centre (this is to do with the medullary neurons)
where is the 4th ventricle in relation to the pons
the 4th ventricle is posterior to the pons
what cranial nerves are associated with the medulla
9, 10, 11, 12
glossopharyngeal
vagus
accessory
hypoglossal
what structures are associated with the medulla
Pyramids
Olives
Cranial nerves
- glossopharyngeal (IX)
- vagus (X)
- accessory (XI)
- hypoglossal (XII)
4th ventricle
Inferior cerebellar peduncle
what are the pyramids formed by
formed by the large
pyramidal (corticospinal)
tracts descending from the
motor cortex
what is the pyramidal decussation
it is where axons of pyramidal tracts cross over to the opposite side at
the level just above the medulla-spinal junction (at the level of the
foramen magnum)
what are the olives
The olive are protrusions out from the pyramids
what do the olives contain
inferior olivary nuclei
what is the role of the inferior olivary nuclei
they relay sensory information to the cerebellum
what makes the floor of the 4th ventricle
the medulla and the pons
what is the fasciculus gracilis
it is a medial fiber tract which carries sensor information from the upper limb
what is the fasciculus cuneatus
it is the lateral fiber tract which carries sensory information from the lower limb
what are the roles of the medulla
Role in maintaining body homeostasis
Cardiovascular centre
- Cardiac centre adjusts rate and force of heart
beat to meet the body’s needs
- Vasomotor centre adjusts blood vessel diameter
to regulate blood pressure
Respiratory centres
- control rate and depth of breathing (together with
centre in pons)
Other reflex centres
- controls activities such as coughing, sneezing,
gagging, swallowing, vomiting, sweating
what happens if you have a stroke in the medulla or the pons
you will die because this is where the cardiac and respiratory centres are
therefore if those aren’t working, you can’t beat your heart and can’t breath you will die
what is the medullas role in homeostasis
The hypothalamus is an important autonomic control centre. It sends its instructions to the medullary reticular centres (networks of neurons), which carry them out by synapsing with the target structure(s)
what happens to the anatomy of the medulla as it goes into the spinal cord
Segmental arrangement of spinal cord ceases ( the spinal cord has levels eg C1 to L2, this is not the case for the medulla)
you also have the reorganisation of white and grey matter
- Columns of white matter become distinct tracts
- Grey matter arranged into distinct nuclei
how many pairs of cranial nerves are there
12
how many pairs of cranial nerves are associated with the brainstem
10
how many pairs of cranial nerves are associated with the forebrain
2
what kind of nerves are the cranial nerves
the are peripheral nerves
these nerves can either be pure sensory, pure motor or mixed
what are some of the sensory functions of the crainial nerves
- touch, pain for face
- hearing, vision, smell
- visceral organs
what are some of the motor functions of the cranial nerves
eye movement
jaw & tongue muscles, facial expression
visceral organ activity
what are the names of the cranial nerves
Old Opie occasionally tries trigonometry and
feels very gloomy, vague and hypoactive
I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlear
V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal
which cranial nerves are sensory, motor and mixed
“Some Say Money Matters But My Brother Says
Big Brains Matter Most”
I. Olfactory = s
II. Optic = s
III. Oculomotor = m
IV. Trochlear = m
V. Trigeminal= mixed (both)
VI. Abducens = m
VII. Facial = mixed
VIII. Vestibulocochlear = s
IX. Glossopharyngeal = mixed
X. Vagus = mixed
XI. Accessory = m
XII. Hypoglossal =m
which cranial nerves are located in the forebrain
I. Olfactory
II. Optic
which cranial nerves are located in the midbrain
III. Oculomotor
IV. Trochlear
which cranial nerves are located in the pons
V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear
which cranial nerves are located in the medulla
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal
what are the olfactory nerves
tiny sensory nerves called filaments
where are the olfactory nerves located
run from the nasal mucosa, pass through cribriform plate of ethmoid bone to synapse with the olfactory bulb
the olfactory nerves are sensory. what sensation do they provide
sense of smell
how would you damage the olfactory nerve and what would this damage cause
Damage causes impaired sense of smell (anosmia)
you could do this by fracture of ethmoid bone
describe the visual projection pathway
optic nerve -> optic chiasm ->optic tract -> superior colliculis -> lateral geniculate nucleus of the thalamus -> optic radiation -> occipital lobe
