Ch 15: Brain and Cranial Nerves Discuss the organization of the brain, including the major structures and their functions Describe the meninges of the.
Download ReportTranscript Ch 15: Brain and Cranial Nerves Discuss the organization of the brain, including the major structures and their functions Describe the meninges of the.
Ch 15: Brain and Cranial Nerves
Discuss the organization of the brain, including the major structures and their functions
Describe the meninges of the spinal cord and brain, and integrate the formation and flow of CSF with this information.
Describe the structures that constitute the BBB and their functions
Review the cranial nerves, again giving a brief function of each.
Major Brain Subdivisions
Telencephalon (= Cerebrum) Diencephalon (Thalamus and hypothalamus)
Mesencephalon Metencephalon (Pons and cerebellum) Myelencephalon (= Medulla oblongata) Brainstem
Gray & White Matter Organization In brain stem similar to spinal cord ( nuclei around ventricles, tracts on outside) In cerebrum and cerebellum : white matter covered with layer of neural cortex (grey)
Cranial Meninges
1. Dura mater - strong, "tough mother" a. falx cerebri b. falx cerebelli c. tentorum cerebelli 2. Arachnoid - spidery, holds blood vessels 3. Pia mater - "delicate mother"
Longitudinal fissure Arachnoid granulations:
This is where the CSF produced in the choroid plexuses of the ventricles and which has circulated into the subarachnoid space is reabsorbed.
Four Ventricles
CSF filled chambers Communicating with central canal of spinal cord Lined by ependymal cells
CSF: Cerebro-Spinal Fluid
Formation in ventricles by specialized ependymal cells of choroid plexuses
(~500 mL/day; total volume ~ 150 mL)
Functions
– – –
transport medium, in shock absorption buoyancy (floats the brain)
CSF circulation: Ventricles → central canal → subarachnoid space
Reabsorption into circulation via arachnoid granulations into superior sagittal sinus.
Blood Brain Barrier (BBB)
what is it?
3 areas in brain don’t have BBB
1.
portion of hypothalamus 2.
3.
pineal gland (in diencephalon) choroid plexus
Cerebrum
Two hemispheres separated by longitudinal fissure Gyrus (gyri) separated by sulcus (sulci)
Major lobes named after overlaying bones
Cerebral Hemispheres . . .
. . have
(motor, sensory and association areas)
. . . have some functional differences
(in spite of anatomical resemblance)
→ Lateralization of cortical functioning
. . . receive information and generate commands for opposite side of body
Cerebral Cortex and Central White Matter
Gray surface (cortex) with white tracts internally
Commissures
– connect corresponding gyri of the two hemispheres 1) corpus callosum 2) anterior commissure
Projection tracts (fibers)
vertically – connect more or less
Association tracts (fibers)
– connect one gyrus to another in the same hemisphere
Basal (or cerebral) Nuclei
Misnomer: basal ganglia Gray matter internal to the cerebral cortex, below floor of lateral ventricles.
Function:
modulate motor output from the cerebral cortex. Subconscious control of skeletal muscle tone and coordination of learned movement patterns.
Parkinson's disease is caused by the loss of at least 80% of the dopaminergic neurons in basal nuclei and substantia nigra (resting tremor)
Diencephalon
Epithalamus Pineal gland - produces melatonin, sets diurnal cycles Thalamus (~12 nuclei) Hypothalamus Just superior to optic chiasma Infundibulum - connects to pituitary gland
Some functions:
Control of autonomic nervous system Coordination of nervous and endocrine systems Secretion of hormones - ADH and oxytocin
Mesencephalon)
= Midbrain Corpora quadrigemina
= 2 pairs of sensory nuclei
1.
2.
Superior colliculi
(relay station for visual information)
Inferior colliculi
(relay station for auditory information
Substantia nigra - regulates motor output Cerebral peduncles - ascending and descending tracts to thalamus Nuclei of ori for CN III and IV
Metencephalon: Cerebellum
Hemispheres and lobes Cortex -gray surface with folia - fine ridges and sulci - grooves between the ridges Purkinje cells , axons of which become arbor vitae (white matter) in center Regulation of posture and balance
Metencephalon: Pons Myelencephalon: Medulla oblongata
Mostly ascending and descending tracts
Nuclei of ori for many cranial nerves
Location of autonomic nuclei involved in respiratory and cardiovascular control
Relay stations for sensory and motor neurons
Cranial Nerves
Twelve pairs:
–
2 attach to forebrain (Telen- & Diencephalon)
–
10 attach to brainstem (Mes-, Met- and Myelencephalon)
Names relate to appearance or function
Classification ?
Olfactory Nerve (= CN or N I)
1º function?
Origin?
Destination? _____________(By way of cribiform plate of ethmoid
)
Only CN directly attached to Cerebrum
Optic Nerve (N II)
1º fu?
ori?
dest? -
by way of optic foramen of sphenoid to Diencephalon (optic chiasma) and to occipital lobe
Oculomotor (N III)
C: Motor O: Mesencephalon D: Somatic motor to superior, inferior, medial recti and inferior oblique; visceral motor to intrinsic eye muscles by way of superior orbital fissure
Trochlear (N IV)
C: Motor O: Mesencephalon D: superior oblique by way of superior orbital fissure
Trigeminal (N V)
C: Mixed three major branches 1. ophthalmic (sensory) 2. Maxillary (sensory) 3. Mandibular (mixed) O: face / nuclei of pons D: sensory nuclei in pons / muscles of mastication
Abducens (CN VI)
C: Motor O: Pons D: Runs lateral rectus eye muscle
Facial (N VII)
C: Mixed O: sensory from taste receptors of anterior 2/3 of tongue / motor from pons D: Sensory to sensory nuclei of pons / motor muscles of facial expression, visceral motor to tear gland.
Vestibulocochlear (N VIII)
C O ?
D
Glossopharyngeal (CN IX)
C: mixed O: sensory from posterior 1/3 of tongue / motor from medulla oblongata D: medulla / muscles for swallowing, parotid gland
Vagus (N X)
C: Mixed O:
Sensation from pharyngeal area and outer ear
/ motor from medulla D:
Sensory to medulla
/ visceral motor to thoracic and abdominal cavities and their organs. Major motor pathway for ANS
Accessory (N XI)
and C: Motor O: Motor nuclei of medulla and spinal cord D: Swallowing, trapezius & scm muscles
Hypoglossal (N XII)
C: Motor O: Motor nuclei of medulla D: Tongue musculature