Brainstem Function Flashcards
(32 cards)
What are the 3 functional classifications of the brainstem?
- Conduit - transmits info to higher centers and to cord via tracts.
- Cranial nerve functions
- Integrative - some motor, regulation of respiratory and CV function, consciouness and pain.
What is the quality of organization in the reticular formation?
Poorly organized.
What are of the brainstem does the reticular formation make up?
The core of the brain stem.
There is a lot of convergence and divergence in the reticular formation. What does this mean?
CONVERGENCE
-a single cell responds to several different sensory input
DIVERGENCE
-a single cell projects to several different targets through collaterals
Do related cells form discrete nuclei in the reticular formation?
No, they are spread diffusely throughout.
Cells in the reticular formation have complex connections and can innervate several levels of the spinal, brainstem and higher centers. What mechanisms enable divergence and convergence?
Divergence = collaterals.
Convergence = large dendritic fields.
Both ascending and descending portions.
Describe the 3 zones of the reticular formation.
- The raphe (seam)
- groups of cells on either side of midline - Medial Zone
- large and small neurons - Lateral Zone
- prominent in rostal medulla and caudal pons
- cranial nerve reflexes and visceral function
- receiving zone
- blended nuclei
What system allows you to orient to visual stimuli?
Tectospinal tract.
In non-conscious awareness, can the brainstem all you to feed, swallow, yawn and stretch?
Yes.
Referring to the motor component of the reticular formation, what 3 tracts does it contain? In what function are these most important?
- Lateral (medullary) reticulospinal tract
- Medial (pontine) reticulospinal tract
- Vestibulospinal (medial and lateral) tracts
Important in walking.
Can produce complex motor patterns without a cortex
The brain needs to deal with stimuli from many different sources at all times. What role does the RF play here?
Responsible for withdrawal from noxious stimuli.
-With damage, non-noxious withdrawal can be seen.
RF helps modulate nociception. Which sections in particular are involved?
Raphe nuclei (either side of midline of pons and medulla).
Also periaqueductal and periventricular gray substance
-contain high levels of endorphins
Which visceral centers are controlled by the RF in the medullary and pontine formation?
Respiratory
-input from chemoreceptors (re: pH, blood O2, stretch)
Pacemaker
-CPG for breathing
How would a phrenic nerve (C3-5) lesion effect breathing?
Depends on level; each distinct
-the further down you go, the more irregular the irregular pattern (as opposed to regularly irregular).
How are cardiovascular centers controlled in the brain (medulla)? Where do they project?
Baroreceptors (CN IX, X), stretch receptors in aorta.
-in ventrolateral
Autonomic nuclei.
The vagus nerve is sympathetic (T/F)?
False.
The CV system has reciprocal connections with the limbic system and may play a role in brainstem malfunction causing panic attacks. What expresses this limbic response (e.g. anger)?
Autonomic centers in the medulla.
What areas are associated with the CV control center in the medulla?
coughing hiccuping sneezing yawning shivering gagging swallowing laughing crying
The hypothalamus projects to areas of the brainstem that influence the sympathetic system. Does it descend and synapse in the RF?
Yes.
What diseases can damage to these descending fibers cause?
Horner’s syndrome
miosis
ptosis
flushing and lack of sweating of the ipsilateral face
What is the projection pathway that is essential for normal consciousness?
Portion of midbrain and rostal pontine RF projects to intralaminar nuclei of thalamus which projects to widespread areas of the cortex.
-known as Ascending Reticular Activating System (ARAS)
What is the result of interruption to the ARAS pathway?
Coma, respiratory and cardiovascular disturbances.
What pathway is involved in sleep (and needs to be calmed before that’s possible)? What other system does it work with?
ARAS.
Works with axons from the locus ceruleus in modulating activity of cerebral cortex.
What neurotransmitter is used in the Specific Transmitter Systems? Where is it located?
Norepinephrine (noradrenaline) or Dopamine.
NOREPINEPHRINE
Located in the locus ceruleus near the PAG (peri-aquiductal grid) in the midbrain and rostral pons.
Projects to widespread areas of the cortex (diverse projections).
