The Brain and Cranial Nerves Concepts Flashcards
Connect the parts of the brain to their embryological origins
Telencephalon -> Cerebrum
Diencephalon -> Thalamus, hypothalamus, and epithalamus
Mesencephalon -> Midbrain
Metencephalon -> Pons, Cerebellum
Myelencephalon -> Medulla oblongata
Describe how the brain is protected, naming the important structures and their functions
The brain is protected by the cranial bones and meninges:
Dura mater splits into 2 layer= periosteal (superficial) and meningeal (deep)
Pia mater wraps around arteries and veins penetrating into the parenchyma of the cerebral cortex
Describe the blood supply of the brain and how the Blood Brain Barrier is formed (astrocytes) and maintained.
The Astrocytes of the brain tissue modify the capillaries feeding the brain to allow only the essentials to cross the blood-brain barrier
Blood vessels only allow oxygen and glucose to come in and CO2, Urea, and creatine to go out as waste.
Explain the formation of cerebrospinal fluid
CSF is a filtrate of blood. Arterial blood from the heart becomes CSF through the choroid plexuses and into the ventricles
Explain the circulation of cerebral spinal fluid through the ventricles
CSF circulates through the 4 ventricles and through the subarachnoid space of the CNS, then becomes venous blood through the arachnoid villa. The venous blood drains from the dural venous sinuses and joins blood in the cerebral veins and eventually drains into the internal jugular vein and back to the heart.
Lateral ventricles (through interventricular foramina) -> 3rd ventricle (through aqueduct of the midbrain) ->4th ventricle (through later and median apertures) -> subarachnoid space -> arachnoid villa
Discuss the decussation of sensory and motor pathways, pointing out some GENERAL ways that these pathways can decussate.
Sensory pathways
DCML pathway= neurons cross the midline at the Great Sensory Decussation (caudal part of medulla), go to the thalamus, then relay up to the cerebral cortex to the motor neuron
ALS pathway= decussate at the spinal level, stays ipsilateral all the way up the spinal cord to the cerebral cortex
Motor pathways
90% decussate at the decussation of the pyramids, 10% at the segmental level
Contrast contralateral sensory and motor pathways with ipsilateral pathways.
Contralateral sensory and motor pathways must decussate to the opposite side of the body (ex: DCML)
Ipsilateral pathways stay on the same side, and information stays ipsilateral (ex: spinocerebellar tract)
Discuss the connection between the hypothalamus and the Autonomic Nervous System
Within the supraoptic region of the hypothalamus, there is an anterior hypothalamic nucleus that connects axons directly to the parasympathetic arm of the ANS. Responsible for controlling all kinds of unconscious ANS activity in the “rest and recovery” mode.
Within the mammillary region, there is a posterior hypothalamic nucleus that connects axons directly to the sympathetic arm of the ANS. Responsible for controlling unconscious ANS activity in the “fight or flight” mode, including vasoconstriction to amp up body temperature.
Describe the cortex, gyri, fissures, and sulci of the cerebrum.
Cortex= gray matter that rolls and folds on itself to increase surface area
Gyri=bumps
Sulci=the grooves between gyri
Fissure= if the groove is very deep
List and locate the lobes of the cerebrum.
The parietal lobe, temporal lobe, frontal lobe, occipital lobe, and insula
All lobes correlate to cranial bones except for the insula, which is deep to all 4 lobes
Describe the tracts that compose the cerebral white matter.
Association tracts= run mostly anteriorly to posteriorly within the same hemisphere
Projection tracts= run mostly inferiorly and superiorly within the same hemisphere
Commissural tracts= connect the two hemispheres by running medially/laterally
Explain the significance of hemispheric lateralization.
Right hemisphere functions receive somatic sensory signals from and control muscles on the left side of the body. Artistic, creative, musical
Left hemisphere functions reives somatic sensory signals from and control muscles on the right side of the body. Rational, numerical, logical
Some people are more right brain than left brain, and vice versa. The different areas that control those different things are slightly more built up and developed in different people between the two.
Describe the functions of the reticular formation.
- Reads all the information available in the body and decides if you’re going to be: completely awake, asleep, transitioning from sleep to awake, in a coma
- Regulates muscle tone for posture and balance, heart rate, blood pressure, and respiratory rate
- Decides what you pay attention to and what to ignore
Describe the structures of the cerebellum
- Cerebellum has a right and left hemisphere, separated by the falx cerebelli
- The vermis separates the two hemispheres
- Each hemisphere has an anterior, posterior, and flocculonodular lobe
- White matter (called arbor vitae) connects the cerebellum to the midbrain via white matter tracts
- Gray matter increases the surface area
-Deep within the white matter are the cerebellar nuclei which relay info in and out of the cerebellum
Describe the functions of the cerebellum.
Minor= controlling posture, balance, and equilibrium
Major= evaluate and correct skeletal motor movement
