Lecture Outline
Adapted from Martini Human Anatomy7th ed. / Session:
Section:
Days / Time: Instructor: / FALL
52999
MW 5:00 PM – 9:20 PM
RIDDELL
Chapter 16
The Nervous System
The Brain and Cranial Nerves
Introduction
The brain is a complex three-dimensional structure that performs a bewildering array of functions
Think of the brain as an organic computer
However, the brain is far more versatile than a computer
The brain is far more complex than the spinal cord
The brain consists of roughly 20 billion neurons
An Introduction to the Organization of the Brain
Embryology of the brain
The CNS begins as a neural tube
The lumen of the tube (neurocoel) is filled with fluid
In the fourth week of development, the cephalic area of the neural tube enlarges to form:
Prosencephalon
Mesencephalon
Rhombencephalon
An Introduction to the Organization of the Brain
Embryology of the brain (continued)
Prosencephalon eventually develops to form:
Telencephalon: forms the cerebrum
Diencephalon: forms the epithalamus, thalamus, and hypothalamus
An Introduction to the Organization of the Brain
Mesencephalon
Does not subdivide
Becomes the midbrain
Rhombencephalon
Eventually develops to form:
Metencephalon: forms the pons and cerebellum
Myelencephalon: forms the medulla oblongata
An Introduction to the Organization of the Brain
Major Regions and Landmarks of the Brain
Medulla oblongata
Pons
Cerebellum
Mesencephalon (midbrain)
Diencephalon
Cerebrum (telencephalon)
An Introduction to the Organization of the Brain
Medulla oblongata
Relays information to the thalamus and brain stem
Regulates visceral function
Pons
Relays information to the thalamus and cerebellum
Regulates subconscious somatic and visceral motor centers
An Introduction to the Organization of the Brain
Cerebellum
Coordinates somatic motor function
Adjusts output of somatic motor centers resulting in smooth operation
Mesencephalon (midbrain)
Processes visual and auditory data
Maintains consciousness and alertness
An Introduction to the Organization of the Brain
Diencephalon
Epithalamus
Contains the pineal gland
Thalamus
Relays information to the cerebrum
Processes sensory information
Hypothalamus
Involved in emotions, thirst, some habitual activity
An Introduction to the Organization of the Brain
Telencephalon (cerebrum)
Conscious thought processes
Memory storage
Conscious regulation of skeletal muscle contractions
An Introduction to the Organization of the Brain
Gray Matter and White Matter Organization
The cerebrum consists of:
Inner region of gray matter
Surrounded by tracts of white matter
Gray matter consists of cell bodies
An Introduction to the Organization of the Brain
The Ventricles of the Brain
Ventricles are fluid-filled cavities
Filled with cerebrospinal fluid (CSF)
Fluid transports nutrients to the CNS and transports waste away from the CNS
CSF also provides protection
There are four ventricles
Ventricles 1 and 2 (called lateral ventricles) are in the cerebral hemispheres (separated by a partition called the septum pellucidum)
Ventricle 3 is in the diencephalon
Ventricle 4 lies between the pons and the cerebellum
An Introduction to the Organization of the Brain
Lateral ventricles (ventricles 1 and 2)
Main portion of the ventricle lies in the parietal lobes
Each has an anterior horn extending into the frontal lobe
Each has a posterior horn extending into the occipital lobe
Each has an inferior horn extending into the temporal lobe
Each communicates with the third ventricle
Through the interventricular foramen
An Introduction to the Organization of the Brain
Third ventricle
Communicates with the fourth ventricle
Through the aqueduct of the midbrain
Fourth ventricle
Communicates with the central canal of the spinal cord
Protection and Support of the Brain
Protection involves:
Bones of the skull
Parietal, frontal, occipital, and temporal bones
Cranial meninges
Dura mater, arachnoid mater, and pia mater
Cerebrospinal fluid
Blood–brain barrier
Protection and Support of the Brain
Cranial Meninges: The Dura Mater
Consists of two layers
Endosteal layer
This is the layer felt within the anterior fontanel of a baby
Meningeal layer
Space between the two layers is called the dural sinus
The meningeal layer forms folds called:
falx cerebri
tentorium cerebelli
falx cerebelli
diaphragma sellae
Protection and Support of the Brain
Folds of the Dura Mater
Falx cerebri
Meningeal layer that extends into the longitudinal fissure
Inferior/anterior portion attaches to the crista galli
Inferior/posterior portion attaches to the internal occipital crest and the tentorium cerebelli
Tentorium cerebelli
Separates the cerebellar hemispheres from the cerebral hemispheres
Extends across the cranium at right angles to the falx cerebri
Protection and Support of the Brain
Folds of the Dura Mater (continued)
Falx cerebelli
Extends from the tentorium cerebelli to separate the cerebellar hemispheres
Diaphragma sellae
Lines the sella turcica of the sphenoid bone
It anchors the dura mater to the sphenoid bone
It encases the pituitary gland
Protection and Support of the Brain
Cranial Meninges: The Arachnoid Mater
Consists of projections called arachnoid granulations
CSF flows through these to enter into blood circulation
Consists of weblike material underlining the arachnoid layer
These collagenous fibers help anchor cerebral blood vessels
Protection and Support of the Brain
Cranial Meninges: The Pia Mater
Attached to the surface of the brain
Follows the sulci and gyri of the brain
Helps to anchor the larger blood vessels of the cerebrum
Protection and Support of the Brain
Cerebrospinal Fluid (CSF)
Provides protection of the brain and spinal cord
Provides support
Transports nutrients to the CNS tissue
Transports waste away from the CNS
Protection and Support of the Brain
Formation of CSF
Produced by the ependymal cells of the choroid plexus
They actively transport nutrients, vitamins, and ions into the CSF
They actively remove waste from the CSF
Protection and Support of the Brain
Circulation of CSF
CSF from the choroid plexus of the lateral ventricles
Flows through the interventricular foramen
Flows into the third ventricle
Flows into the aqueduct of the midbrain
Flows into the fourth ventricle
Through the lateral aperture and median aperture andcentral canal of the spinal cord
Flows into the subarachnoid space
Flows around the brain and spinal cord eventually enters circulation via the arachnoid granulations
Protection and Support of the Brain
Blood–Brain Barrier
The lining of the blood vessels consists of endothelial cells that are highly interconnected by tight junctions
Due to this tight connection, only lipid-soluble material can pass from the blood to the cells of the brain and spinal cord
Water-soluble material can only pass via the action of transport mechanisms
The transport mechanisms are very specific
The Medulla Oblongata
Medulla oblongata
Continuous with the spinal cord to the brain stem
All communication between the brain and spinal cord passes through the medulla oblongata
Nuclei in the medulla oblongata are:
Relay stations for sensory or motor pathways
Associated with cranial nerves connected to the medulla oblongata
Associated with the autonomic control of visceral organs
The Medulla Oblongata
Relay stations
Nucleus gracilis and nucleus cuneatus
Pass sensory information to the thalamus
Olivary nuclei
Pass information to the cerebrum, diencephalon, and brain stem
The Medulla Oblongata
Nuclei of cranial nerves
Contains sensory and motor nuclei of cranial nerves:
VIII, IX, X, XI, and XII
Autonomic nuclei
Major centers include:
Cardiovascular centers (cardiac and vasomotor)
Respiratory centers (rhythmic breathing)
The Pons
The pons is a prominent bulge superior to the medulla oblongata and consists of:
Sensory and motor nuclei for cranial nerves:
V, VI, VII, and VIII
Nuclei involved with involuntary control of breathing:
Consist of apneustic center and pneumotaxic center
Nuclei that relay cerebellar commands:
Consist of cerebellar peduncles
Ascending, descending, and transverse tracts
The Mesencephalon
Mesencephalon (also called the midbrain)
Consists of two pairs of nuclei collectively called corpora quadrigemina
Responsible for processing auditory and visual stimuli
Auditory processing occurs in the inferior colliculus
Visual processing occurs in the superior colliculus
Consists of nuclei of the reticular formation
Involved in maintaining alertness
The Mesencephalon
Mesencephalon (continued)
Consists of:
Red nucleus: integrates information between the cerebrum and cerebellum
Substantia nigra: regulates motor output of the basal nuclei
Cerebral peduncles: have ascending fibers that synapse in the thalamus and descending fibers of the corticospinal pathway
The Diencephalon
The diencephalon consists of:
Epithalamus
Thalamus
Hypothalamus
The Diencephalon
The epithalamus
Forms the roof of the third ventricle
Contains the pineal gland
Produces the hormone melatonin
Regulates our day/night cycles
The Diencephalon
The thalamus
Forms the walls of the third ventricle
There is a right and a left thalamus
Thalamic nuclei are egg-shaped
Each thalamic nucleus is divided into:
Anterior group: part of the limbic system
Medial group: relays information to the frontal lobe
Ventral group: relays information to the parietal lobes
Posterior group: relays information to the occipital lobe
Lateral group: adjusts activity in the cingulate gyrus
The Diencephalon
The hypothalamus
Forms the floor of the third ventricle
Consists of numerous nuclei
Consists of an infundibulum, which connects to the pituitary gland
Consists of the mamillary body on the posterior wall of the hypothalamus
The Diencephalon
The hypothalamus (continued)
Consists of nuclei to control:
Subconscious control of skeletal muscles
Heart rate, blood pressure, respiration, and digestive functions
Secretion of antidiuretic hormone and oxytocin
Emotional and behavioral drives and thirst drives
Coordination between voluntary and autonomic functions
Body temperature
Circadian rhythm
The Cerebellum
The cerebellum consists of:
Two hemispheres
Folia (folds similar to gyri of the cerebrum)
Anterior and posterior lobes
Vermis (separates the hemispheres)
Flocculonodular lobes
Arbor vitae
Cerebellar peduncles
The Cerebellum
The cerebellum
Cerebellar cortex: subconscious coordination of movements
Arbor vitae: connects cerebellar cortex with cerebellar peduncles
Cerebellar peduncles
Superior: connect cerebellum with mesencephalon, diencephalon, and cerebrum
Middle: communicate between cerebellum and pons
Inferior: connect cerebellum with the medulla oblongata
The Cerebrum
The cerebrum consists of:
Two hemispheres
Several lobes
Frontal, parietal, occipital, and temporal
Gyri and sulci
Longitudinal fissure
Corpus callosum
Basal nuclei
Limbic system
The Cerebrum
The Cerebral Hemispheres
The hemispheres consist of:
Gyri and sulci
Central sulcus
Longitudinal fissure
Cerebral lobes
The Cerebrum
The Cerebral Hemispheres
The Cerebral Lobes
Frontal lobe: conscious control of skeletal muscles
Occipital lobe: perception of visual stimuli
Parietal lobe: conscious perception of touch, pressure, vibration, pain, temperature, and taste
Temporal lobe: conscious perception of auditory and olfactory stimuli
The Cerebrum
Motor and Sensory Areas of the Cerebral Cortex
Precentral gyrus
Anterior to the central gyrus
Neurons direct voluntary movements by controlling somatic motor neurons in the brain stem and spinal cord
Postcentral gyrus
Posterior to the central gyrus
Neurons receive somatic sensory information for touch, pressure, pain, taste, and temperature from the dorsal columns and spinothalamic tracts
The Cerebrum
Hemispheric Specialization
Left hemisphere
Speech center, writing, language, mathematics
Right hemisphere
Analysis by touch, spatial visualization
The Cerebrum
The Central White Matter
Consists of bundles called:
Association fibers: tracts that interconnect areas of neural cortex within a hemisphere (arcuate fibers and longitudinal fasciculi)
Commissural fibers: tracts that connect the two hemispheres (anterior commissure and corpus callosum)
Projection fibers: tracts that link the cerebrum with other regions of the brain and spinal cord
The Cerebrum
The Basal Nuclei
These are masses of gray matter embedded in the white matter inferior to the lateral ventricles
Consist of:
Caudate nucleus
Amygdaloid body
Claustrum
Putamen
Globus pallidus
The Cerebrum
The Basal Nuclei
Caudate nucleus, putamen, and globus pallidus
Control the cycles of arm and leg movements when walking
Claustrum
Plays a role in subconscious processing of visual information
Amygdaloid body
Component of the limbic system
The Cerebrum
The Limbic System
Located between the cerebrum and the diencephalon just superior to the corpus callosum
Functions:
Establishes emotional states
Links the conscious functions with the unconscious autonomic functions
Facilitates memory storage and retrieval
The Cerebrum
The limbic system consists of:
Cingulate gyrus
Dentate gyrus
Parahippocampal gyrus
Hippocampus
The Cerebrum
The Limbic System
The fornix
Tract of white matter connecting the hippocampus with the hypothalamus
Many fornix fibers extend to the mamillary bodies
Mamillary bodies control reflex movements associated with eating
The Cranial Nerves
There are 12 pairs of cranial nerves
These nerves innervate the periphery emerging from the brain (not the spinal cord)
These nerves are on the ventrolateral surface of the brain
They are numbered beginning at the anterior aspect of the brain
They are numbered CN I to CN XII
The Cranial Nerves
CN I: The Olfactory Nerve
Function: sensory (smell)
Origin: olfactory epithelium
Foramen: olfactory foramina
Destination: olfactory bulbs
The Cranial Nerves
CN II: The Optic Nerve
Function: sensory (vision)
Origin: retina
Foramen: optic canal
Destination: diencephalon, then to occipital lobe
The Cranial Nerves
CN III: The Oculomotor Nerve
Function: controls extra-ocular eye muscles
Motor function
Superior, inferior, and medial rectus
Inferior oblique
Levator palpebrae superioris
Origin: mesencephalon
Foramen: superior orbital fissure
Destination: extra-ocular eye muscles
The Cranial Nerves
CN IV: The Trochlear Nerve
Function: controls extra-ocular eye muscles
Motor function
Superior oblique
Origin: mesencephalon
Foramen: superior orbital fissure
Destination: extra-ocular eye muscles
The Cranial Nerves
CN V: The Trigeminal Nerve
Function:
Mixed (sensory and motor) function
Ophthalmic: sensations from the forehead, eyelids, and nose
Maxillary: sensations from lower eyelid, upper lip, and cheek
Mandibular: controls mastication
Origin: ophthalmic, maxillary, and mandibular nerves
The Cranial Nerves
CN V: The Trigeminal Nerve (continued)
Foramen:
Ophthalmic: superior orbital fissure
Maxillary: foramen rotundum
Mandibular: foramen ovale
Destination:
Ophthalmic and maxillary: Pons
Mandibular: mandibular muscles
The Cranial Nerves
CN VI: The Abducens Nerve
Function: controls eye movements
Motor function
Origin: pons
Foramen: superior orbital fissure
Destination: innervates the lateral rectus eye muscle
The Cranial Nerves
CN VII: The Facial Nerve
Function: Mixed (sensory and motor)
Sensory: sensations from the face / taste
Motor: controls muscles of the face
Origin:
Sensory: taste buds
Motor: pons
Foramen: internal acoustic meatus
Destination:
Sensory: pons
Motor: muscles of the face
The Cranial Nerves
CN VIII: The Vestibulocochlear Nerve
Function:
Sensory: balance and hearing
Origin: receptors of the vestibule and cochlea
Foramen: internal acoustic meatus
Destination: pons
The Cranial Nerves
CN IX: The Glossopharyngeal Nerve
Function: Mixed (sensory and motor)
Sensory function: tongue pain
Motor function: swallowing
Origin:
Sensory: posterior 1/3 of the tongue
Motor: salivary gland
The Cranial Nerves
CN IX: The Glossopharyngeal Nerve (continued)
Foramen: jugular foramen
Destination:
Sensory: pons
Visceral motor: parotid salivary gland
Somatic motor: pharyngeal muscles for swallowing
The Cranial Nerves
CN X: The Vagus Nerve
Function:
Sensory: information from organs
Motor: sends information to the organs
Origin:
Sensory: from the organs
Motor: medulla oblongata
The Cranial Nerves
CN X: The Vagus Nerve (continued)
Foramen: jugular foramen
Destination:
Sensory: autonomic centers of the medulla oblongata
Somatic motor: muscles of the palate and pharynx
Visceral motor: respiratory, cardiovascular, and digestive organs
The Cranial Nerves
CN XI: The Accessory Nerve
Function:
Motor: controls the sternocleidomastoid, trapezius, palate, pharynx, and larynx muscles
Origin: spinal cord and medulla oblongata
Foramen: jugular foramen
Destination:
Internal branch: muscles of the palate, pharynx, and larynx
External branch: sternocleidomastoid and trapezius muscles
The Cranial Nerves
CN XII: The Hypoglossal Nerve
Function:
Motor: controls tongue movement
Origin: medulla oblongata
Foramen: hypoglossal canal
Destination: tongue muscles
The Cranial Nerves
Summary of Cranial Nerve Branches and Functions
Mnemonic aid
Oh, Once One Takes The Anatomy Final, Very Good Vacations Are Heavenly
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