Chr. 14 - The Brain and Cranial Nerves Flashcards
[14.1] List the major parts of the brain.
Brainstem, cerebellum, diencephalon, cerebrum.
[14.1] What are the cranial meninges?
The dura mater, arachnoid mater, and the pia mater.
[14.1] List the extensions of the dura mater and which parts of the brain they separate.
Falx cerebri, separates the two hemispheres of the cerebrum.
Falx cerebelli, separates the two hemispheres of the cerebellum.
Tentorium cerebelli, separates the cerebrum from the cerebellum.
[14.1] Describe the blood-brain barrier.
Endothelial cells of capillaries sealed together by tight junctions coupled with a thick basement membrane surrounding the capillaries. Selectively allows certain substances in blood to enter brain tissue.
[14.2] Describe cerebrospinal fluid (CSF).
Clear, colourless liquid composed mainly of water. Carries oxygen, glucose, and other micronutrients from blood to nervous tissue. Circulates through cavities in the brain, spinal cord, and the subarachnoid space.
[14.2] What are the cavities of the brain and where are they located?
Lateral Ventricles, two lateral ventricles each located in either hemisphere of the brain.
Third Ventricle, a narrow cavity along the midline above the hypothalamus and between the halves of the thalamus.
Fourth Ventricle, lies between the brainstem and cerebellum.
[14.2] What is the septum pellucidum?
A thin membrane separating the anterior portions of the lateral ventricles.
[14.2] List and describe the functions of CSF.
Mechanical protection, serves as shock-absorbing fluid and buoys the brain in the cranial cavity.
Chemical protection, provides optimal chemical environment for neuronal signaling.
Circulation, medium of exchange for nutrients and waste of nervous tissue.
[14.2] Describe choroid plexuses.
Networks of blood capillaries in the walls of ventricles that produce CSF. Covered by ependymal cells featuring tight junctions that allow for bidirectional secretion. Tight junctions of the ependymal cells forces all material to pass through them instead of between cells.
[14.2] What is the blood-cerebrospinal fluid barrier?
The barrier formed by ependymal cells and their tight junctions that protect the brain and spinal cord from harmful substances that would use CSF as a vector.
[14.2] What are the interventricular foramina?
Two narrow oval openings of the lateral ventricles (one in each) that allow CSF to flow into the third ventricle.
[14.2] What is the aqueduct of the midbrain?
A passage formed between the third ventricle and the fourth ventricle that passes through the midbrain.
[14.2] What are the median and lateral apertures?
Median aperture, an opening in the roof of the fourth ventricle on the midline allowing CSF to circulate into the subarachnoid space.
Lateral apertures, openings on the lateral aspects of the fourth ventricle allowing CSF to circulate into the subarachnoid space.
[14.2] Where is CSF formed?
In the choroid plexuses of each lateral ventricle, the choroid plexus in the roof of the third ventricle, and the choroid plexus of the fourth ventricle.
[14.2] How is CSF reabsorbed?
Through arachnoid villi, extensions of the arachnoid mater the project into the dural venous sinuses.
[14.2] What is the superior sagittal sinus?
A sinus located at the superior, posterior region of the brain.
[14.2] What is an arachnoid granulation?
A cluster of arachnoid villi.
[14.3] Describe the medulla oblongata.
A structure continuous with the spinal cord forming the inferior part of the brainstem. Begins at the foramen magnum and extends to inferior border of the pons. Contains all sensory and motor tracts extending between the brain and spinal cord.
[14.3] What are the pyramids of the medulla?
Bulges of white matter formed by the corticospinal tracts passing from the cerebrum to the spinal cord.
[14.3] What is the decussation of pyramids?
A crossing of axons to opposite sides of the body just above the junction of the medulla and spinal cord.
[14.3] List and describe the nuclei of the medulla.
Cardiovascular center, regulates rate and force of heartbeat as well as diameter of blood vessels.
Medullary respiratory center, adjusts basic rhythm of breathing.
Vomiting center, causes vomit reflex.
Deglutition center, promotes deglutition when stimulated.
Gustatory nucleus, part of the gustatory sensory pathway.
Cochlear nuclei, part of the auditory sensory pathway.
Vestibular nuclei, components of the equilibrium sensory pathway.
[14.3] What are medullary olives?
Oval-shaped swellings lateral of pyramids that contain the inferior olivary nucleus.
[14.3] What is the inferior olivary nucleus?
A nucleus of the medulla oblongata that receives input from the cerebral cortex, red nucleus of the midbrain, and spinal cord. Neurons in the nucleus extend their axons into the cerebellum to regulate cerebellar neurons.
[14.3] What are the gracile nuclei and cuneate nucleus?
Nuclei located on both posterior sides of the medulla that are associated with sensations of touch, pressure, vibration, and conscious proprioception. Form synapses with axons from the spinal cord and relay information to the thalamus.
[14.3] What is the medial lemniscus?
Myelinated axons of the gracile and cuneate nucleus that ascend to the thalamus, decussating shortly after extending from the neural soma in the nucleus.
[14.3] What is the posterior column-medial lemniscus pathway?
A pathway formed by the tracts of the posterior columns and the axons of the medial lemniscus.
[14.3] Describe the pons.
A structure of the brainstem laying directly superior to the medulla and anterior to the cerebellum. Consists of both nuclei and tracts, and mainly functions to connect parts of the brain with one another.
[14.3] What are the main regions of the pons?
A ventral region and a dorsal region.
[14.3] What is the pontine nuclei?
A large synaptic relay station of scattered grey centers in the ventral region synapsing with numerous white matter tracts. Essential role in coordinating and maximizing efficiency of voluntary motor output.
[14.3] What is the pontine respiratory group?
A nucleus that works in tandem with the medullary respiratory center to control breathing.
[14.3] Describe the midbrain.
A structure of the brainstem that extends from the pons to the diencephalon. Contains nuclei and tracts.
[14.3] What are the cerebral peduncles?
Paired bundles of axons of the corticospinal, corticobulbar, and corticopontine tracts. They conduct nerve impulses from the cerebral cortex to the spinal cord, medulla, and pons respectively.
[14.3] What is the tectum?
The posterior part of the midbrain and contains four rounded elevations.
[14.3] What are the superior colliculi?
The two superior elevations of the tectum that serve as reflex centers for visual activities. Innervate extrinsic eye muscles and skeletal muscles of head, neck, and trunk in responses to visual activity.
[14.3] What are the inferior colliculi?
The two inferior elevations of the tectum that relay impulses from auditory sensory receptors to the brain and include auditory reflexes.
[14.3] What are the substantia nigra?
Two nuclei, one on each side of the midbrain, that release dopamine and help control subconscious muscle activity.
[14.3] What are the red nuclei?
Nuclei, one in each side of the midbrain, aiding to control muscular movement by synapsing with axons from the cerebellum and cerebral cortex.
[14.3] What is the reticular formation?
A broad region where white and grey matter form a net-like arrangement extending from the superior portion of the spinal cord to the inferior part of the diencephalon. Responsible for consciousness, attention, and awakening. Prevents sensory overload.
[14.3] What is the reticular activating system?
The ascending portion of the reticular formation consisting of sensory axons projecting to the cerebral cortex.
[14.4] Describe the cerebellum.
A mass of nervous tissue forming the posterior/inferior portion of the brain. Contains folds increasing surface area. Rests posterior to the medulla/pons.
[14.4] What is the transverse fissure?
A deep groove separating the cerebellum from the cerebrum and containing the tentorium cerebelli.
[14.4] What is the tentorium cerebelli?
A membrane supporting the posterior cerebrum and separating the cerebellum from the cerebrum.
[14.4] What is the vermis of the cerebellum.
The central constricted area of the cerebellum.
[14.4] What are the cerebellar hemispheres?
Lateral portions of the cerebellum that resemble wings.
[14.4] What is the purpose of the anterior and posterior lobe of the cerebellum?
To govern subconscious aspects of skeletal muscle movement.
[14.4] What is the cerebellar cortex?
The superficial layer of the cerebellum consisting of grey matter in slender, parallel folds called folia.
[14.4] What is the arbor vitae?
Tracts of white matter deep to the cerebellar cortex.
[14.4] What are the cerebellar nuclei?
Regions of grey matter deep to the arbor vitae that extend axons to other brain centers.
[14.4] What are the cerebral peduncles?
Bundles of white matter attaching the cerebellum to the brainstem, with extending axons that link the cerebellum to other regions of the brain.
[14.4] What are the superior cerebellar peduncles?
Peduncles of the cerebellum resting superior to the others that extend axons to the red nuclei of the midbrain and several nuclei in the thalamus.
[14.4] What are the middle cerebellar peduncles?
Bundle of axons extending from the pontine nuclei to the cerebellum carrying impulses for voluntary movements.
[14.4] What are the inferior cerebral peduncles?
Paired bundles of white matter made of five axon groups:
- Axons from spinocerebellar tract carrying proprioceptive information of the body
- Axons from the vestibular apparatus and vestibular nuclei of medulla and pons
- Axons from the inferior olivary nucleus of medulla regulating cerebellar neurons
- Axons from the cerebellum to vestibular nuclei of medulla and pons
- Axons from the cerebellum extending to the reticular formation
[14.5] Describe the diencephalon.
The central core of brain tissue superior of the midbrain and surrounded by the cerebral hemispheres and contributes to a wide variety of sensory and motor processing between higher and lower brain centers. Consists of the thalamus, hypothalamus, and epithalamus.
[14.5] Describe the thalamus.
A pair of oval masses of grey matter organized into nuclei with interspersed tracts of white matter.
[14.5] What is the interthalamic adhesion?
A bridge of grey matter joining the right and left halves of the thalamus.