Chapter 14 - The Brain and Cranial Nerves Flashcards
What is The Development of the Nervous System?
The development of the nervous system begins with a thickening of the Ectoderm called the Neural Tube
Prosencephalon (forebrain):
1- Make Telencephalon, make Cerebrum, make Lateral Ventricles
2- Make Diencephalon, make Thalamus, Hypothalamus, and Epithalamus, make Third Ventricle
Mesencephalon (midbrain):
Make Mesencephalon, make Midbrain, make Aqueduct of the Midbrain between Third and Fourth Ventricles
Rhombencephalon (Hindbrain):
1- Make Metencephalon, make Pons and Cerebellum, make Upper Part of Fourth Ventricle
2- Myelencephalon, make Medulla Oblongata, make Lower Part of Fourth Ventricle
All ventricles form CSF from up to down
(Lateral Ventricles to Third Ventricle to Fourth Ventricle)
(If path blocked, CSF accumulates, Brain gets bigger but skull doesn’t, need surgery to fix)
What are the Principle Parts of the Brain?
1- Cerebrum
2- Diencephalon:
Thalamus
Hypothalamus
Pineal Gland (part of Epithalamus)
3- Brainstem:
Midbrain
Pons
Medulla Oblongata
4- Cerebellum
5- Spinal Cord
6- Pituitary Gland
What is Brain Protection?
Brain is protected by:
1- Cranial bones
2- Cranial Meninges:
Pia Mater
Arachnoid Mater
Dura Mater (Cranial Dura is composed of 2 layers: Periosteal and Meningeal layers)
Epidural Space between Bone and Dura
Subdural Space between Dura and Arachnoid
Subarachnoid Space between Arachnoid and Pia
3- CSF
What are the Structures around the Superior Sagittal Sinus?
Skin
Parietal Bones
Epidural Space
Dura Matter (Periosteal layer then Meningeal layer)
Subdural Space
Arachnoid Matter
Subarachnoid Space
Pia Mater
Arachnoid Villus (extends from Arachnoid Matter into sinus)
Cerebral Cortex
Falx Cerebri (inferior to Superior Sagittal Sinus, where Dura Matter of both hemispheres meet)
What is Blood Flow to the Brain?
Blood flows to the Brain via the Vertebral and Carotid Arteries
And flows back to the Heart via the Jugular Veins
What is Homoculus?
Picture of self in Brain
What is Importance of Blood Flow to the Brain?
The Brain utilizes about 20% of the body’s oxygen supply
Any interruption of the oxygen supply can result in weakening, permanent damage, or death of Brain cells
Glucose deficiency may produce mental confusion, dizziness, convulsions, and unconsciousness
What is Blood-Brain Barrier (BBB)?
The BBB protects Brain cells from harmful substances and pathogens by serving as a selective barrier to prevent passage of substances from blood to Brain
BBB can prevent entry of therapeutic drugs
Injury to Brain may cause a breakdown of the BBB, permitting passage of normally restricted substances into Brain tissue
What is CSF?
CSF is a liquid that protects Brain and Spinal Cord against chemical and physical injuries
CSF carries oxygen, glucose, and other important substances from blood to nervous tissue cells
What are Ventricles and the Choroid Plexus?
Ventricles of the Brain contain CSF
Choroid Plexuses make CSF
How are Ventricles Organized?
1- Two Lateral Ventricles:
Separated by Septum Pellucidum
2- Third Ventricle:
Inferior to Lateral Ventricles
Interventricular Foramen connects Lateral Ventricles to Third Ventricle
3- Fourth Ventricle:
Inferior to Third Ventricle
Aqueduct of the Midbrain connects Third Ventricle to Fourth Ventricle
4- Below the Fourth Ventricle:
Lateral Aperture (between Pons and Medulla Oblongata)
Median Aperture (Posterior of Medulla Oblongata)
Central Canal (in Spinal Cord)
What is Choroid Plexus made of?
Choroid Plexus inside Ventricles
Blood capillary of Choroid Plexus
Capillary Endothelium around it
Pia Matter around it
Ependymal Cells with Tight Junctions around it
What is CSF Flow?
1- Lateral Ventricles’ Choroid Plexus make CSF into Lateral Ventricles
2- CSF goes to Third Ventricle through Interventricular Foramen
Third Ventricle’s Choroid Plexus makes CSF into Third Ventricle
3- CSF goes to Fourth Ventricle through Aqueduct of the Midbrain (Cerebral Aqueduct)
Fourth Ventricle’s Choroid Plexus make CSF into Fourth Ventricle
4- CSF goes to Subarachnoid Space through Lateral and Median Apertures
5- CSF goes to Arachnoid Villi of Dural Venous Sinuses
6- CSF goes into Venous Blood
7- Venous Blood goes to Heart and Lungs
8- Arterial Blood goes from Heart to each Choroid Plexus in each Ventricle
What is Tentorium Cerebelli?
Separate Cerebrum from Cerebellum on each hemisphere
What is Septum Pellucidum?
Separates both Lateral Ventricles
What is Corpus Callosum?
Superior to Lateral Ventricles
What is Brainstem?
Brainstem is composed of the:
1- Medulla Oblongata
2- Pons
3- Midbrain
What is Medulla Oblongata?
Medulla Oblongata: CN8-12
Continuous with the superior aspect of the Spinal Cord
Contains portions of both Motor and Sensory Tracts
1- Cranial Nerves:
Vestibulocochlear Nerve VIII (8) - (balance, ears)
Glossopharyngeal Nerve XI (9)
Vagus Nerve X (10)
Accessory Nerve XI (11)
Hypoglossal Nerve XII (12)
2- Structural regions:
Pyramids
Inferior Olivary Nuclei
3- Functional Regions:
Heart Rate
Respiratory Rate
Vasoconstriction
Swallowing
Coughing
Vomiting
Sneezing
Hiccupping
What is Pons?
Pons: 5-8
Located superior to Medulla Oblongata
Links parts of Brain with one another by way of Tracts
1- Cranial Nerves:
Trigeminal Nerve V (5)
Abducens Nerve VI (6)
Facial Nerve VII (7)
Vestibular Branch of Vestibulocochlear Nerve VIII (8) - (balance)
2- Functional Regions:
Relays nerve impulses related to voluntary skeletal muscle movements from Cerebrum to Cerebellum
Pneumotaxic and Apneustic Areas (control of respiration)
What is Midbrain?
Midbrain: 3-4
Located superior to Medulla Oblongata
Extends from Pons to Diencephalon
1- Cranial Nerves:
Oculomotor Nerve III (3)
Trochlear Nerve IV (4)
2- Structural Regions:
Cerebral Peduncles
Corpora Quadrigemina
Substantia Nigra (if damaged, Parkinson’s Disease, resting tremors)
Red Nuclei
Medial Lemniscus
3- Functional Regions:
Conveys motor impulses from Cerebrum to Cerebellum and Spinal Cord
Sends sensory impulses from Spinal Cord to Thalamus
Regulates auditory and visual reflexes
What is Reticular Formation?
Reticular Formation:
Helps regulate muscles tone
Alerts Cortex to incoming sensory signals
Responsible for maintaining consciousness and awakening from sleep
What is Cerebellum?
Cerebellum:
Occupies inferior and posterior aspects of Cranial Cavity
Consists of 2 Hemispheres and a Central Vermis
Functions:
Coordination of skeletal muscle contractions
Maintenance of normal muscle tone, posture, and balance