Chapter 12 Central Nervous System

CHAPTER 12

CENTRAL NERVOUS SYSTEM

Surface Head ectoderm

Neural plate

Tail 1 The neural plate forms from surface ectoderm.

Neural folds

Neural groove

2 The neural plate invaginates, forming the neural groove, flanked by neural folds.

Neural crest

3 Neural fold cells migrate to form the neural crest, which will form much of the PNS and many other structures.

Head Surface ectoderm

Neural tube Tail

4 The neural groove becomes the neural tube, which will form CNS structures.

(a) (b) Primary brain (c) Secondary brain (d) Adult brain (e) Adult Neural vesicles vesicles structures neural tube canal regions

Cerebrum: cerebral Lateral hemispheres (cortex, Telencephalon ventricles white matter, basal nuclei)

Anterior Prosencephalon Diencephalon (rostral) (forebrain) Diencephalon (thalamus, hypothalamus, Third ventricle epithalamus), retina

Mesencephalon Cerebral Mesencephalon Brain stem: midbrain (midbrain) aqueduct

Rhombencephalon Metencephalon Brain stem: pons (hindbrain) Cerebellum Fourth ventricle Myelencephalon Brain stem: medulla Posterior oblongata (caudal) Spinal cord Central canal

Cerebral hemisphere

Diencephalon Cerebellum Brain stem • Midbrain • Pons • Medulla (d) Birth oblongata

Central cavity Cortex of gray matter Migratory Inner gray pattern of matter neurons Cerebrum Outer white Cerebellum matter Gray matter Region of cerebellum Central cavity Inner gray matter Outer white matter

Gray matter Brain stem

Central cavity Outer white matter Inner gray matter Spinal cord

Lateral ventricle Septum pellucidum Anterior horn Posterior horn Inferior horn

Interventricular Lateral foramen aperture Third ventricle Median aperture Inferior horn Lateral Cerebral aqueduct aperture Fourth ventricle Central canal (a) Anterior view (b) Left lateral view

1) High density areas of neuron cell bodies 2) Muscle 3) Blood vessels 4) High density areas of unmyelinated axons 5) High density areas of myelinated axons

1) True 2) False

Copyright © 2010 Pearson Education, Inc. Figure 12.6a Lobes and fissures of the cerebral hemispheres. Precentral Central gyrus sulcus Postcentral Frontal gyrus lobe Parietal lobe Parieto-occipital sulcus (on medial surface of hemisphere) Lateral sulcus Occipital lobe Temporal lobe Transverse cerebral fissure Cerebellum Pons Fissure Medulla oblongata (a deep Spinal cord sulcus) Gyrus Cortex (gray matter) Sulcus White matter

(a)

Gyri of insula Temporal lobe (pulled down)

(b)

Longitudinal Frontal lobe fissure

Cerebral veins and arteries Parietal covered by lobe arachnoid mater Left cerebral Right cerebral hemisphere hemisphere Occipital lobe (c) Posterior

Longitudinal Left frontal Left temporal Areas active fissure lobe lobe in speech and hearing (fMRI)

Motor areas Central sulcus Sensory areas and related

Primary motor cortex association areas Premotor cortex Primary somatosensory cortex Frontal eye field Somatic Somatosensory sensation association cortex Broca’s area Gustatory cortex (outlined by dashes) Taste (in insula) Prefrontal cortex Working memory Wernicke’s area for spatial tasks (outlined by dashes) Executive area for task management Working memory for Primary visual object-recall tasks cortex Vision Solving complex, Visual multitask problems association area Auditory association area Hearing Primary auditory cortex (a) Lateral view, left cerebral hemisphere

Primary motor cortex Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex

Cingulate Primary Premotor cortex gyrus motor cortex Central sulcus Corpus Primary somatosensory callosum cortex Frontal eye field Parietal lobe Prefrontal Somatosensory cortex association cortex Parieto-occipital sulcus

Processes emotions Occipital related to personal lobe and social interactions Visual Orbitofrontal association area cortex Olfactory bulb Olfactory tract Primary Fornix visual cortex Temporal lobe Uncus Calcarine sulcus Primary Parahippocampal olfactory cortex gyrus (b) Parasagittal view, right hemisphere

Primary motor cortex Motor association cortex Primary sensory cortex Sensory association cortex Multimodal association cortex

Posterior

Motor Sensory Motor map in Anterior Sensory map in precentral gyrus postcentral gyrus

Toes Genitals

Jaw

Tongue Primary motor Primary somato- cortex sensory cortex Intra- Swallowing (precentral gyrus) (postcentral gyrus) abdominal

Copyright © 2010 Pearson Education, Inc. Quiz Q1: All of these are true of the primary motor cortex except it… 1) Is located anterior to the central sulcus 2) Is located on the precentral gyrus 3) Controls voluntary muscle movement 4) Coordinates repeated/learned complex muscle movements

Copyright © 2010 Pearson Education, Inc. Quiz Q2: The sensory homunculus has the fingers mapped to a large area of the brain because… 1) The fingers have a very large surface area 2) The fingers have lots of muscles required to move them 3) The fingers contain many sensory receptors 4) All of the above

1) True 2) False

1) muscles directly. 2) the primary somatosensory cortex 3) the somatosensory association cortex 4) the primary motor cortex

1) myelinated axons 2) neuron cell bodies 3) Schwann cells 4) ganglia

Longitudinal fissure Association fibers Superior Lateral Commissural fibers (corpus callosum) ventricle Corona Basal nuclei radiata • Caudate • Putamen • Globus Fornix pallidus Internal Thalamus capsule Gray matter Third White matter ventricle Projection Pons fibers Decussation Medulla oblongata of pyramids (a) (b)

Fibers of corona radiata Caudate nucleus Thalamus Lentiform Tail of Corpus nucleus caudate striatum • Putamen • Globus pallidus nucleus (deep to putamen)

Projection fibers run deep to (a) lentiform nucleus

Anterior Cerebral cortex Cerebral white matter Corpus callosum Anterior horn of lateral ventricle Caudate nucleus Putamen Globus Lentiform pallidus nucleus Thalamus Tail of caudate nucleus Third ventricle Inferior horn of lateral ventricle (b) Posterior

Cerebral cortex Cerebral white matter Corpus callosum Anterior horn of lateral ventricle Caudate nucleus

Lentiform nucleus

Thalamus

Third ventricle Inferior horn of lateral ventricle (b)

1) Part of the cerebral cortex 2) Part of the cerebral hemispheres 3) Gray matter 4) 2 and 3 only 5) All of the above

Cerebral hemisphere

Septum pellucidum Corpus callosum Interthalamic Fornix adhesion Choroid plexus (intermediate Thalamus mass of (encloses third thalamus) ventricle) Interven- Posterior commissure tricular Pineal gland foramen (part of epithalamus) Anterior Corpora commissure quadrigemina Mid- Hypothalamus Cerebral brain aqueduct Optic chiasma Arbor vitae (of Pituitary gland cerebellum) Mammillary body Fourth ventricle Choroid plexus Pons Cerebellum Medulla oblongata Spinal cord

Paraventricular Dorsal nuclei nucleus Medial Lateral Lateral dorsal posterior Anterior commissure Fornix Dorsomedial nucleus Preoptic nucleus Posterior Pulvinar Anterior hypothalamic hypothalamic nucleus Anterior nucleus Lateral Medial Supraoptic hypothalamic nuclear geniculate group nucleus area body Supra- Ventromedial Reticular Lateral chiasmatic nucleus nucleus geniculate nucleus Arcuate Mammillary

Ventral body Optic nucleus body chiasma Ventral Ventral postero- Pituitary anterior lateral lateral Infundibulum gland (stalk of the Ventral nuclei pituitary gland) (a) The main thalamic nuclei. (The reticular (b) The main hypothalamic nuclei. nuclei that “cap” the thalamus laterally are depicted as curving translucent structures.)

View (a) Optic chiasma Optic nerve (II)

Diencephalon Crus cerebri of • Thalamus cerebral peduncles • Hypothalamus (midbrain) Thalamus Diencephalon Mammillary body Hypothalamus Oculomotor nerve (III) Midbrain Pons Brainstem Trochlear nerve (IV) Medulla oblongata Trigeminal nerve (V) Middle cerebellar Pons peduncle Facial nerve (VII) Abducens nerve (VI) Vestibulocochlear Glossopharyngeal nerve (IX) nerve (VIII) Hypoglossal nerve (XII) Pyramid Vagus nerve (X) Ventral root of first cervical nerve Accessory nerve (XI) Decussation of pyramids

Spinal cord

(a) Ventral view

Crus cerebri of cerebral peduncles Thalamus (midbrain) View (b) Infundibulum Superior colliculus Pituitary gland Inferior colliculus Trochlear nerve (IV) Trigeminal nerve (V) Superior cerebellar peduncle Pons Middle cerebellar peduncle Facial nerve (VII) Inferior cerebellar peduncle Abducens nerve (VI) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Olive Hypoglossal nerve (XII) Thalamus Diencephalon Vagus nerve (X) Hypothalamus Accessory nerve (XI) Midbrain Pons Brainstem Medulla oblongata

(b) Left lateral view

Thalamus

View (c)

Diencephalon Midbrain • Superior Corpora colliculus quadrigemina • Inferior of tectum colliculus Pineal gland • Trochlear nerve (IV) • Superior cerebellar peduncle Pons • Middle cerebellar peduncle Medulla oblongata Anterior wall of • Inferior cerebellar peduncle fourth ventricle • Facial nerve (VII) • Vestibulocochlear nerve (VIII) Choroid plexus • Glossopharyngeal nerve (IX) (fourth ventricle) • Vagus nerve (X) Dorsal median sulcus • Accessory nerve (XI) Thalamus Diencephalon Dorsal root of Hypothalamus first cervical nerve Midbrain Pons Brainstem (c) Dorsal view Medulla oblongata

Superior Tectum Dorsal Periaqueductal gray colliculus matter Cerebral aqueduct Oculomotor nucleus (III) Reticular formation Medial lemniscus Red nucleus Substantia nigra Fibers of pyramidal tract Ventral Crus cerebri of (a) Midbrain cerebral peduncle

Fourth ventricle Reticular Superior cerebellar formation peduncle Trigeminal main sensory nucleus Trigeminal motor nucleus Middle cerebellar peduncle Trigeminal Pontine nerve (V) nuclei Fibers of Medial lemniscus pyramidal (b) Pons tract

Fourth ventricle Solitary Hypoglossal nucleus (XII) Choroid nucleus plexus Dorsal motor nucleus Vestibular nuclear of vagus (X) complex (VIII) Inferior cerebellar Cochlear

peduncle nuclei (VIII)

Lateral nuclear group Nucleus Medial ambiguus nuclear group Inferior olivary Raphe nucleus nucleus Reticular formation Reticular Pyramid Medial lemniscus (c) Medulla oblongata

Anterior lobe Cerebellar cortex Arbor vitae

Cerebellar peduncles Posterior • Superior lobe • Middle Choroid • Inferior plexus of Medulla Flocculonodular fourth oblongata lobe ventricle (b)

Anterior lobe Arbor vitae

Cerebellar cortex

Pons

Fourth Posterior ventricle lobe Medulla Flocculonodular lobe oblongata (a) Choroid plexus

Anterior lobe

Posterior lobe

(d) Vermis

Septum pellucidum Fiber tracts connecting limbic Diencephalic structures Corpus callosum system structures

of the limbic system •Fornix •Anterior thalamic •Anterior commissure nuclei (flanking 3rd ventricle) Cerebral structures of the •Hypothalamus limbic system •Mammillary body •Cingulate gyrus •Septal nuclei •Amygdala •Hippocampus •Dentate gyrus •Parahippocampal gyrus Olfactory bulb

Visual impulses Auditory impulses Reticular formation Ascending general Descending sensory tracts motor projections (touch, pain, temperature) to spinal cord

Skin of scalp Periosteum Bone of skull Periosteal Dura Meningeal mater Superior Arachnoid mater sagittal sinus Pia mater Subdural Arachnoid villus space Blood vessel Subarachnoid Falx cerebri space (in longitudinal fissure only)

Superior sagittal sinus Skull Falx cerebri Straight Scalp sinus Occipital lobe Crista galli of the Tentorium cerebelli ethmoid Dura mater bone Falx Transverse Pituitary cerebelli sinus gland Cerebellum Temporal Arachnoid bone mater over medulla oblongata (a) Dural septa (b) Dural venous sinuses

Superior sagittal sinus 4 Choroid plexus Arachnoid villus Interventricular foramen Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Right lateral ventricle (deep to cut) Choroid plexus of fourth ventricle 3 Third ventricle 1 CSF is produced by the Cerebral aqueduct choroid plexus of each Lateral aperture ventricle. Fourth ventricle 2 CSF flows through the ventricles and into the Median aperture 2 subarachnoid space via the Central canal median and lateral apertures. of spinal cord Some CSF flows through the central canal of the spinal cord.

3 CSF flows through the (a) CSF circulation subarachnoid space. 4 CSF is absorbed into the dural venous sinuses via the arachnoid villi.

Ependymal cells Capillary Section of choroid Connective plexus tissue of pia mater

Wastes and Cavity of CSF forms as a filtrate unnecessary containing glucose, oxygen, solutes absorbed ventricle vitamins, and ions (Na+, Cl–, Mg2+, etc.) (b) CSF formation by choroid plexuses

Cervical Cervical spinal nerves enlargement

Dura and arachnoid Thoracic mater spinal nerves Lumbar enlargement Conus medullaris Lumbar Cauda spinal nerves equina Filum (a) The spinal cord and its nerve terminale Sacral roots, with the bony vertebral spinal nerves arches removed. The dura mater and arachnoid mater are cut open and reflected laterally.

Spinal cord Vertebral arch

Denticulate Denticulate ligament ligament

Dorsal Arachnoid median mater sulcus Dorsal root

Spinal dura mater (c) Thoracic spinal cord, showing denticulate ligaments.

T12

Ligamentum flavum L5 Lumbar puncture needle entering subarachnoid space L4

Supra- spinous ligament

L5 Filum terminale

S1 Inter- Cauda equina vertebral Arachnoid Dura in subarachnoid disc matter mater space

Epidural space Pia mater (contains fat) Arachnoid mater Spinal Subdural space meninges Dura mater Subarachnoid space Bone of (contains CSF) vertebra

Dorsal root ganglion Body of vertebra

(a) Cross section of spinal cord and vertebra

Copyright © 2010 Pearson Education, Inc. Figure 12.31b Anatomy of the spinal cord. Dorsal median sulcus Gray commissure Dorsal funiculus Dorsal horn White Ventral funiculus Gray Ventral horn columns Lateral funiculus matter Lateral horn Dorsal root ganglion

Spinal nerve Central canal

Dorsal root (fans out into Ventral median dorsal rootlets) fissure

Ventral root (derived from several Pia mater ventral rootlets) Arachnoid mater Spinal dura mater

(b) The spinal cord and its meningeal coverings

1) Dorsal 2) Ventral 3) Anterior 4) Posterior

Dorsal root (sensory) Dorsal root ganglion Dorsal horn (interneurons) Somatic sensory neuron Visceral sensory neuron Visceral motor Spinal nerve neuron Ventral horn Ventral root (motor neurons) Somatic (motor) motor neuron Interneurons receiving input from somatic sensory neurons

Interneurons receiving input from visceral sensory neurons

Visceral motor (autonomic) neurons

Somatic motor neurons

Ascending tracts Descending tracts

Fasciculus gracilis Ventral white Dorsal commissure white Fasciculus cuneatus column Lateral reticulospinal tract Dorsal Lateral spinocerebellar corticospinal tract tract Rubrospinal tract Ventral spinocerebellar Medial tract reticulospinal Lateral tract spinothalamic tract Ventral corticospinal Ventral spinothalamic tract tract Vestibulospinal tract Tectospinal tract

Dorsal Medial lemniscus (tract) spinocerebellar (axons of second-order neurons) (axons of tract Nucleus gracilis second-order Nucleus cuneatus neurons) Medulla oblongata Fasciculus cuneatus (axon of first-order sensory neuron)

Joint stretch receptor Axon of (proprioceptor) first-order Cervical spinal cord neuron Fasciculus gracilis Muscle spindle (axon of first-order sensory neuron) (proprioceptor) Lumbar spinal cord

Touch receptor (a) Spinocerebellar Dorsal column–medial pathway lemniscal pathway

Primary somatosensory cortex Axons of third-order neurons Thalamus

Cerebrum

Midbrain

Cerebellum

Pons

(a) Spinocerebellar Dorsal column–medial pathway lemniscal pathway

Internal capsule

Cerebrum

Midbrain Cerebral peduncle

Cerebellum

Pons

(a) Pyramidal (lateral and ventral corticospinal) pathways

Ventral corticospinal tract Medulla oblongata Pyramids Decussation of pyramid Lateral corticospinal Cervical spinal cord tract

Skeletal muscle

Lumbar spinal cord

Somatic motor neurons (lower motor neurons) (a) Pyramidal (lateral and ventral corticospinal) pathways