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
What are the Structures of the Cerebellum?
Anterior Lobe
Posterior Lobe
Vermis (separates hemispheres)
Cerebellar Superior Peduncle
Cerebellar Middle Peduncle
Cerebellar Inferior Peduncle
Flocculonodular Lobe
Folia (foliage looking)
Arbor Vitae (White Matter)
Cerebellar Cortex (Gray Matter)
What is Diencephalon?
Diencephalon composed of the:
1- Thalamus
2- Hypothalamus
3- Epithalamus
What is Thalamus?
Pain Center
Thalamus:
Located superior to Midbrain
Contains Nuclei that serve as relay stations for all sensory impulses (except smell) to the Cerebral Cortex
Structures:
Interthalamic Adhesion
Inferior to Central Sulcus (motor area anterior, sensory area posterior)
What are the Thalamus’s Nuclei?
Reticular
Medial
Interthalamic Adhesion
Midline
Anterior
Internal Medullary Lamina
Intralaminar
Ventral Anterior
Lateral Dorsal
Ventral Lateral
Ventral Posterior
Lateral Posterior
Pulvinar
Lateral Geniculate
Medial Geniculate
What is Hypothalamus?
Hypothalamus:
Inferior to Thalamus
Has 4 major regions
Controls many body activities
One of major regulators of homeostasis
What are the Structures of the Hypothalamus?
Posterior Hypothalamic Nucleus
Mammillary Body
Dorsomedial Nucleus
Ventromedial Nucleus
Arcuate Nucleus
Paraventricular Nucleus
Anterior Hypothalamic Nucleus
Supraoptic Nucleus
Medial Preoptic Nucleus
Lateral Preoptic Nucleus
Suprachiasmatic Nucleus
What is Epithalamus?
Epithalamus:
Superior and posterior to Thalamus
Contains Pineal Gland
Pineal gland secrets Melatonin
Habenular Nuclei involved in olfaction
What is Circumventricular Organs (CVOs) of the Diencephalon?
CVO:
Parts of the Diencephalon
Monitor chemical changes in blood because they lack BBB
- CVOs include a portion of the:
Hypothalamus
Pineal Gland
Pituitary Gland
CVOs coordinate homeostatic activities of the Endocrine and Nervous Systems
What is Cerebrum?
Cerebral Cortex composed of Gray Matter which contains billions of neurons
Gyri, Fissures, and Sulci can be identified on the Cortex
Deep to Cortex is White Matter composed of Tracts of neurons that connect parts of the Brain to each other and the Spinal Cord
Corpus Callosum:
Bundle of White Matter Tracts that connect right and left hemispheres of Cerebrum
What are some of the Cerebral Cortex Markings?
Frontal Lobe
Parietal Lobe
Occipital Lobe
Longitudinal Fissure (separate right and left hemispheres)
Precentral Gyrus
Central Sulcus
Postcentral Gyrus
What are the Lobes of the Cerebrum?
Cerebrum divided into the:
1- Frontal Lobe
2- Parietal Lobe
3- Temporal Lobe
4- Occipital Lobe
5- Insula (deep at intersection of Frontal, Parietal, and Temporal Lobes)
Parieto-Occipital Sulcus
Transverse Fissure (between Occipital and Temporal Lobes and Cerebellum)
Lateral Cerebral Sulcus (between Frontal and Temporal Lobes)
What are the Basal Nuclei of the Cerebrum?
Basal Nuclei are paired masses of Gray Matter in each Cerebral Hemisphere
Basal Nuclei:
1- Caudate Nucleus
2- Putamen
3- Globus Pallidus
Help initiate and terminate movements
Suppress unwanted movements
Regulate muscle tone
What is Limbic System?
Limbic System found in Cerebral Hemispheres and Diencephalon
Promotes range of emotions:
Pleasure
Pain
Docility
Affection
Fear
Anger
What is Functional Organization of the Cerebral Cortex?
Specific types of sensory, motor, and integrative signals are processed in certain regions of the Cerebral Cortex
There are:
1- Sensory Areas
2- Motor Areas
3- Association Areas
What are some Functional Areas of the Cerebrum?
Primary Auditory Area
Prefrontal Cortex
Broca’s Speech Area (motor speech area)
Frontal Eye Field Area
Premotor Area
Primary Motor Area (precentral Gyrus)
Central Sulcus
Primary Somatosensory Area (Postcentral Gyrus)
Somatosensory Association Area
Common Integrative Area
Wernicke’s Area (speech interpretation, then sent to Broca’s Speech Area)
Visual Association Area
Primary Visual Area
What is Hemisphere Lateralization?
Functional differences in right and left hemispheres
What is Right Hemisphere Functions?
Receive somatic sensory signals from and controls muscles on left side of body
Music/Art
Space/Pattern perception
Recognition of faces and emotional content of facial expression
Generate emotional content of language
Generate mental images to compare spatial relationships
Identify and discriminate among odors
Patient with damage to right hemisphere that correspond to Broca’s and Wernicke’s areas in left hemisphere speak in monotonous voice, having lost ability to impart emotional inflections to what they say
What is Left Hemisphere Functions?
Receive somatic sensory signals from and control muscles on right side of body
Reasoning
Numerical and scientific skills
Ability to use and understand sign language
Spoken and written language
Persons with damage in left hemisphere often exhibit Aphasia (hard to understand speak read write)
What are Brain Waves?
Brain waves indicate electrical activity of the Cerebral Cortex
Presented on an EEG
For awake:
1- Alpha
2- Beta
For sleep:
3- Theta
4- Delta
What are Cranial Nerves?
Olfactory Nerve I (1)
Optic Nerve II (2)
Oculomotor Nerve III (3)
Trochlear Nerve IV (4)
Trigeminal Nerve V (5)
Abducens Nerve VI (6)
Facial Nerve VII (7)
Vestibulocochlear Nerve VIII (8)
Glossopharyngeal Nerve IX (9)
Vagus Nerve X (10)
Accessory Nerve XI (11)
Hypoglossal Nerve XII (12)
What is Olfactory Nerve (CN I)?
Special Sensory:
Olfaction (smell)
What is Optic Nerve (CN II)?
Special Sensory:
Vision
What is Oculomotor Nerve (CN III)?
Motor Somatic:
Movement of eyeballs and upper eyelids
Motor Autonomic:
Adjusts Lens for near vision
Constricts Pupil
What is Trochlear Nerve (CN IV)?
Motor Somatic:
Movement of eyeballs
What is Trigeminal Nerve (CN V)?
Mixed
Sensory:
Touch, Pain, Thermal sensation from scalp, face, and oral cavity (including teeth and anterior 2/3 of tongue)
Motor (branchial):
Chewing
Controls middle ear muscles
What is Abducens Nerve (CN VI)?
Motor Somatic:
Movement of eyeballs
What is Facial Nerve (CN VII)?
Mixed
Sensory:
Taste from anterior 2/3 of tongue
Touch, Pain, Thermal sensation from skin in external ear canal
Motor (branchial):
Control of muscles of facial expression and middle ear muscle
Motor Autonomic:
Secretion of tears and saliva
What is Vestibulocochlear Nerve (CN VIII)?
Special Sensory:
Hearing and equilibrium
What is Glossopharyngeal Nerve (CN IX)?
Mixed
Sensory:
Taste from posterior 1/3 of tongue
Proprioception in some swallowing muscles
Monitor BP and oxygen and CO2 levels in blood
Touch, Pain, Thermal sensation from skin of external ear and upper pharynx
Motor (branchial):
Assists in swallowing
Motor Autonomic:
Secretion of saliva
What is Vagus Nerve (CN X)?
Mixed
Sensory:
Taste from epiglottis
Proprioception from throat and voice box muscles
Monitor BP and oxygen and CO2 levels in blood
Touch, Pain, Thermal sensation from skin of external ear
Sensation from thoracic and abdominal organs
Motor (branchial):
Swallowing
Vocalization
Coughing
Motor Autonomic:
Motility and secretion of GI organs
Constriction of respiratory passageways
Decreases HR
What is Accessory Nerve (CN XI)?
Motor (branchial):
Movement of head and pectoral girdle
Sternocleidomastoid muscle
What is Hypoglossal Nerve (CN XII)?
Motor Somatic:
Speech
Manipulation of food
Swallowing
What is Development of Brain and Cranial Nerves?
During the 3rd week of gestation, Ectoderm thickens, forming Neural Plate
Neural Plate folds inward and forms the Longitudinal Groove
On either side of the Longitudinal Groove, the raised edges are the Neural Folds
Eventually the Neural Folds meet to form the Neural Tube
How does Aging affect Nervous System?
Aging can result in:
Loos of neurons
Diminished capacity for sending nerve impulses to and from Brain
Diminished ability to process information
Decreased conduction velocity
Slowing of voluntary motor movements
Increased reflex time
Degenerative changes in vision, hearing, sight, taste, smell, touch, and balance
What are some Brain Disorders?
Cerebrovascular Accident (Stroke)
Transient Ischemic Attack (TIA)
Alzheimer’s Disease (type of Dementia, CNS disease)
