Chapter 14 Flashcards
Four major parts of brain?
Brain stem
Cerebellum
Diencephalon
Cerebrum
Brainstem
Continuous with spinal cord and consists of medulla oblongata, pons, midbrain
Cerebellum
Posterior to brainstem
Diencephalon
Superior to the brainstem
Consists of thalamus, hypothalamus, epithalamus
Cerebrum
Supported on Diencephalon and brainstem
Largest part of brain
Cranial meninges
Continuous with spinal meninges
Same basic structure
Same names: dura mater, arachnoid mater, pia mater
Two dural layers: periosteal layer and meningeal layer
Extensions of dura mater that separate brain parts?
Flax cerebrum
Flax cerebelli
Tentorium cerebelli
Falx cerebri
Separates two hemispheres of cerebrum
Falx cerebelli
Separates two hemispheres of the cerebellum
Tentorium cerebelli
Separates the cerebrum from the cerebellum
How does blood flow (mainly) to the brain?
Internal carotid and vertebral arteries
Where do the dural venous sinuses drain in order to return blood from the head to the heart?
Internal jugular vein
How much does the brain weight in terms of body percentage?
2% of total body weight
How much oxygen and glucose is used by the brain in terms of body percentage?
20% of oxygen and glucose used by the body is used by the brain
How long does it take for an interruption. Of blood flow to impact neuronal function and cause permanent damage?
Impairment takes 1-2 minutes
Permanent injury takes 4 minutes
Why must the supply of glucose to the brain be continuous?
Because none is “stored” in the brain
What does low glucose levels in the blood entering the brain cause?
Mental confusion, dizziness, convulsions, loss of consciousness may occur
Blood brain barrier (BBB)
Consists mainly of tight junctions that seal together the endothelial cells of brain blood capillaries and a thick basement membrane that surrounds the capillaries
Cerebrospinal fluid (CSF)
Clear liquid, made up of mostly water that protects the brain
Carries small amounts of oxygen, glucose, and other chemicals from the blood to the neurons and neuroglia
Continuously circulated through cavities
80-150 mls
Ventricles
CSF filled cavities within brain
Lateral ventricle
One in each hemisphere of cerebrum, separated anteriorly by thin membrane
Septum pellucidum
Thin membrane that separates the lateral ventricles
Third ventricle
Narrow, slit like cavity along the midline superior to hypothalamus and between the right and left halves of the thalamus
Fourth ventricle
Between brainstem and cerebellum
CSF basic functions for maintaining homeostasis?
- Mechanical protection
- Chemical protection
- Circulation
Choroid plexuses
Main site of CSF production
Blood cerebrospinal fluid barrier
Protects brain and spinal cord from potentially blood borne substances formed by tight junctions of ependymal cells
Interventional foramina
Two narrow, oval openings
The CSF formed in the choroid plexuses of each lateral ventricle flows where?
Into the third ventricle through two narrow, oval openings (interventricular foramina)
Where does the fluid flow after adding more CSF from the third ventricle?
Aqueduct of the midbrain
Three structures of brainstem?
- Medulla oblongata
- Pons
- Midbrain
Reticular formation
Extends through brainstem
Network of interspersed gray and white matter
Medulla oblongata
Begins at the foramen magnum and extends to the inferior border of the pons
Contains motor and sensory tracts
Decussationn of pyramids
Axons on left side go to right side and via versa is why the brain controls opposit side of body
Nuclei
Medulla nuclei control vital body functions
Vomiting, swallowing, sneezing, coughing, and hiccuping
Cardiovascular (CV) center
Regulates the rate and force of the heartbeat and diameter of blood vessels
Medullary respiratory centre
Adjust basic rhythm of breathing
Deglutition center
Promotes deglutition (swallowing)
Inferior olivary nucleus
Receives input from the cerebral cortex, red nucleus of midbrain, and spinal cord. Used to make adjustments to muscle activity as you learn new motor skills
Gracile and cuneate nucleus
Associated with touch, pressure, vibration, and conscious proprioception
Two tracts in the posterior columns of spinal cord form synapses in these nuclei
Medial lemniscus
Band of white matter extends through medulla, pons, and midbrain
Posterior column medial lenniscus pathway
Tracts of the posterior columns and axons of the medial lemniscues
Gustatory nucleus in medulla
Taste
Cochlear nuclei in medulla
Auditory pathway
Vestibular nuclei medulla
Equalibrium
Pons
Lies directly superior to the medulla and anterior to the cerebellum, 2.5 cm long, a “bridge” connects parts of the brain
Ventral and dorsal region
Pontine nuclei
Scattered grey centers in the synaptic relay station of pons
Pontine respiratory group
Helps control breathing with medulla respiratory group
Cranial nerves associated with pons nuclei?
- Trigeminal (v) nerve
- Abducens (VI) nerves
- Facial (VII) nerves
- Vestibulocochlear (VIII) nerves
Midbrain or mesencephalon
- Extends from pons to the diencephalon
- Contains nuclei and tracts
3.
Cerebral peduncles
paired bundles of axons located in the anterior part of midbrain
Axons of the corticospinal, corticobulbar, and corticopontine tracts, which conduct nerve impulses from motor areas in cerebral cortex to spinal cord, medulla, and pons
Tectum
Posterior part of midbrain contains four rounded elevations
Superior: superior colliculi, inferior colliculi
Reticular formation
Where white and gray matter exhibit netlike arrangement
Contains sensory and motor neurons
Reticular activating system (RAS)
Ascending: wakefulness, arousal,maintain attention, prevent sensory over load
Descending: muscle tone
Inactivation: produces sleep
Damage: coma
Transverse fissure and Tentorium cerebelli in cerebellum
Support posterior part of cerebrum and separates cerebellum from cerebrum
