#7. Brain stem Flashcards
What makes up the brain stem?
- medulla oblongata
- pons
- midbrain
Where is the medulla oblongata located?
it goes from the foramen magnum and goes to the pons
What is the medulla oblongata made of?
sensory (ascending) tracts and motor (descending) tracts
What are the pyramids?
- bulges of white matter on the anterior part of the medulla.
- formed by the corticospinal tracts
What is the crossing of axons in the pyramids called?
decussation of pyramids
What is the importance of the decussation of pyramids?
it explains why each side of the brain controls the opposite side of the body.
What percentage of axons cross at the decussation of pyramids?
90%
What does the cardiovascular center in the medulla do?
regulates the rate and force of the heartbeat and the diameter of BV’s
What does the medullary rhythmicity area of the respiratory center do?
adjusts the basic rhythm of breathing (along with areas in the pons)
What is the olive?
a oval-shaped swelling located lateral to each pyramid.
Which nucleus is located in the olive?
the inferior olivary nucleus
What does the inferior olivary nucleus receive input from?
-receives input from the cerebral cortex, the red nucleus (midbrain) and the spinal cord.
What does the olive deal with?
it mainly has to do with movement
Where do the neurons from the inferior olivary nucleus go?
- they extend into the cerebellum, where they regulate the activity of the cerebellar neurons
What does the inferior olivary nucleus do?
-it provides instructions that the cerebellum uses to make adjustments to mm activity as you learn new motor skills
What are the gracile nucleus and cuneate nucleus involved with?
-they are associated with sensations of touch, pressure, vibration and conscious proprioception
What is the gustatory nucleus for?
- receiving gustatory input from the taste buds of the tongue.
- relays from the tongue to the brain
What is the cochlear nuclei for?
- it is part of the auditory pathway from the inner ear to the brain
- receives auditory input from cochlea of the inner ear
What is the vestibular nuclei for?
-equilibrium pathway from inner ear to brain
Which cranial nerves have their nuclei located in the medulla?
VIII - vestibularcochlear nerve IX - glossopharyngeal nerves X - vagus nerve XI - accessory nerve XII - hypoglossal nerve
What are the nuclei located in the medulla?
- gracile nucleus
- cuneate nucleus
- gustatory nucleus
- cochlear nucleus
- vestibular nuclei
- CN VII, IX, X, XI, XII
- inferior olivary nucleus
- cardiovascular center
- medullary rhythmicity area of respiratory center
- vomiting center
- deglutition center
How can you injure the medulla?
a hard blow to the back of the head/upper neck
What does an alcohol overdose affect in the medulla?
the medullary rhythmicity area.
can result in death
What is the pons?
the bridge that connects parts of the brain with each other
What is the pons made of?
nuclei and tracts
What the pontine nucleus do?
-relays signals for voluntary movements from cerebral cortex to the cerebellum
Which nuclei are in the pons?
- pontine nucleus
- neclei for: pneumotaxic area and apneustic area
- CN V, VI, VII, VIII
what is the pneumotaxic area responsible for?
rhythm of breathing
What is the apneustic area responsible for?
inhale/exhale
Which cranial nerve has nuclei in both the pons and the medulla?
VIII - vestibulocochlear nerve
Where are the cerebral peduncles located?
anterior part of the midbrain
What are the cerebral peduncles?
- paired bundles of axons
- axons from corticospinal tracts, corticobulbar tracts, and corticopontine tracts.
Are the tracts in the cerebral peduncles efferent or afferent?
efferent
what is the corticospinal tract for?
the motor area in the cerebral cortex to the spinal cord
What is the corticobulbar tract for?
the motor areas in the cerebral cortex to the medulla
What is the corticopontine tract for?
motor areas in the cerebral cortex to the pons.
Where is the tectum?
the posterior part of the midbrain
What does the tectum contain?
superior colliculi and inferior colliculi
What does the superior colliculi do?
- nuclei in 2 superior elevations that coordinate movement of head, eyes, trunk in response to a visual stimulus
(ie. you see something in the corner of your eye and you turn towards it)
What does the inferior colliculi do?
- coordinates movements of the head, eyes, trunk in response to auditory stimuli
(ie. you hear something and you turn)
what is the startle reflex?
sudden movements of the head, eyes, and trunk that occur when surprised by a loud noise
What is the substantia nigra?
-neurons that release dopamine and help control the subconscious muscles activities
What is loss of the substantia nigra associated with?
Parkinson’s disease
What does the red nuclei do?
involved with voluntary muscle movements
Why is the red nuclei red?
it has a rich blood supply and iron-containing pigment
What nuclei are in the midbrain?
- substantia nigra
- red nuclei
- CN III and IV
What is the reticular formation?
a net like arrangment of grey and white matter that is located throughout the brain stem
What is the importance of the RAS?
-system that wakes you up.
What does RAS stand for?
reticular activating system
What makes up the RAS?
sensory axons that project to the cerebral cortex and motor axons connecting to the cerebellum and spinal cord
What activates the RAS?
- visual stimuli
- auditory stimuli
- mental activites
- pain, touch, pressure stimuli
- proprioceptive receptors
What does the RAS do?
- it is involved in consciousness
- active during arousal
- helps maintain attention and alertness
- prevents sensory overload
How does the RAS prevent sensory overload?
by filtering out insignificant information so the it does not reach consciouness (ie. pants, pants, pants.)
What does inactivation of RAS do?
produces sleep.
Define sleep
a stat of partial consciousness from which an individual can be aroused
What happens if the RAS is damaged?
-coma
Define muscle tone
the slight degree of involuntary contraction in normal resting skeletal muscles
What is the RAS involved in?
- regulating muscle tone
- regulation of heart rate
- regulation of BP
- regulation of respiratory rate
What sense does the RAS not receive sensory input from?
olfactory
