Physiology-Reticular Formation Flashcards
Where is the reticular formation located?
The central core of the brainstem, anatomically around the central tegmental tract.
What different pathways does the reticular formation have?
Ascending Reticular Activating System (ARAS), Pain Suppression Pathway, Reticulospinal Motor Pathway and Descending Autonomic Pathway.
What spinal tracts contact the reticular formation?
Spinalthalamic tract, spinal Vth tract (ALSTT in brainstem) and pyramids (corticospinal tract)
What reticular pathway are the neurons indicated below a part of?
Note the gigantocellular neurons compared to the smaller neurons. These are characteristic of ARAS (anterior reticular activating system). Notice below how its dendrites project far into the brainstem to get input from various pathways and how its axons extend into the thalamus.
How do anesthetic depress stimuli from cutting skin so that patients don’t wake up?
They depress the reticular formation so signals don’t get relayed to the thalamus and cortex.
How is pain suppressed by the reticular formation?
The cortex, hypothalamus & amygdala send primary axons to the periaqueductal gray where they synapse -> secondary periaqueductal gray fibers travel to the reticular formation’s nucleus raphe magnus in the pons where they synapse -> the raphe sends tertiary fibers toward the pain fibers in the spinal cord to suppress pain stimulation.
How does the reticular formation increase muscle tone when you are running? How does the reticular formation prevent you from moving around a lot during REM sleep?
Pontine reticulospinal tract: + muscle tone. Medullary reticuolspinal tract: - motor activity.
How does the reticular formation play a role in increasing your heart rate when you are in a shootout?
Activation of the descending autonomic pathway via action on the intermediolateral cell column.
What neurotransmitters are associated with the reticular formation?
Many of the neurons in the reticular formation synthesize the classic neurotransmitters (ACh, NE, 5-HT, DA and Histamine).
What side effect come with drugs that work on neurotransmitters that are related to the reticular formation?
Arousal, attention and sleep.
What regions of the brain are responsible for producing neurotransmitters related to attention and learning new information?
Mesopontine cholinergic system (thalamus) and basal forebrain are responsible for synthesizing ACh. If you think about it, stimulation of the thalamus by ACh enhances sensory input and ACh stimulation of the cortex helps us organize the information we sense as we learn.
What regions of the brain are responsible for producing neurotransmitters related to pain and sleep suppression?
Raphe nuclei are responsible for synthesizing serotonin.
What regions of the brain are responsible for producing neurotransmitters related to focusing attention and arousal?
The Locus Ceruleus is responsible for synthesizing NE.
Why might a patient with high blood pressure take medication that causes him to lose his attention span?
Alpha-2 adrenergic agonists prevent NE release. NE plays a role in focusing attention.
What regions of the brain are responsible for producing neurotransmitters related to motor activation and behavior sequencing?
The substantia nigra and ventral tegmental area are responsible for synthesizing dopamine.
What regions of the brain are responsible for producing neurotransmitters related to CNS arousal when you are awake?
There is a small cell group outside of the hypothalamus in the reticular formation that synthesize histamine.
What are the two continuums that change as you move down the “coma” spectrum?
Normal: awake & aware. Coma/sleep/anesthesia: neither. Vegetative: Awakable, not aware. Locked-in: awake & aware.
What are the 3 major sources for coma and chronic loss of consciousness? Big 3 causes?
SOURCES: 1) Cortical/thalamic damage 2) Upper brainstem damage 3) Metabolic interruption of neurotransmission. CAUSES: 1) Head trauma 2) Intoxication 3) Stroke
