The Central Nervous System Chapter 9a The Central Nervous System

Anatomy of the central nervous system The spinal cord The brain About this Chapter Anatomy of the central nervous system The spinal cord The brain Brain function

The Embryonic Nervous System The neural tube specializes into the seven major regions of the central nervous system A 4-week human embryo showing the anterior end of the neural tube, which has specialized into three brain regions Hindbrain Forebrain Midbrain Spinal cord Lumen of neural tube (a) Figure 9-3a

The Embryonic Nervous System At 6 weeks, the neural tube has differentiated into the brain regions present at birth. The central cavity (lumen) shown in the cross section will become the ventricles of the brain. (see Fig. 9.5) Cerebrum Diencephalon Midbrain Eye Medulla oblongata Spinal cord (b) Cerebellum and Pons Forebrain Hindbrain Figure 9-3b

The Embryonic Nervous System Cerebrum Diencephalon Midbrain Medulla oblongata Cerebellum Spinal cord Pons (c) By 11 weeks of embryonic development, the growth of the cerebrum is noticeably more rapid than that of the other divisions of the brain. Figure 9-3c

Late Developmental Regions Structure Derived from Regions Early Developmental Regions Thalamus

Encephalons Development

CNS: Bone and Connective Tissue Brain is encased in bony skull or cranium Spinal cord runs through vertebral column Meninges lies between bone and tissues Dura mater Arachnoid membrane Pia mater Meningeal layers of the brain cushion and protect delicate neural tissue

Anatomy of the Central Nervous System ANATOMY SUMMARY CENTRAL NERVOUS SYSTEM SECTIONAL VIEWS OF THE CNS Cranium Cranium Dura mater Cerebral hemispheres Venous sinus Arachnoid membrane Pia mater Cerebellum Brain Subdural space Subarachnoid space Cervical spinal nerves (b) Meningeal layers of the brain cushion and protect delicate neural tissue. Central canal Gray matter White matter Thoracic spinal nerves Spinal nerve Pia mater Spinal cord Arachnoid membrane Meninges Dura mater Sectioned vertebrae Body of vertebra Autonomic ganglion Lumbar spinal nerves Sacral spinal nerves Spinal nerve Coccygeal nerve (c) Posterior view of spinal cord and vertebra (a) Posterior view Figure 9-4

CNS: Gray and White Matter Gray matter Unmyelinated nerve cell bodies Dendrites Axon terminals White matter Myelinated axons Contains very few cell bodies

CNS: Gray and White Matter ANATOMY SUMMARY CENTRAL NERVOUS SYSTEM Central canal Gray matter White matter Thoracic spinal nerves Spinal nerve Pia mater Spinal cord Arachnoid membrane Meninges Dura mater Sectioned vertebrae Body of vertebra Autonomic ganglion Lumbar spinal nerves Sacral spinal nerves Spinal nerve Coccygeal nerve (c) Posterior view of spinal cord and vertebra (a) Posterior view Figure 9-4 (2 of 2)

CNS: Gray and White Matter ANATOMY SUMMARY CENTRAL NERVOUS SYSTEM Central canal Gray matter White matter Spinal nerve Pia mater Spinal cord Arachnoid membrane Meninges Dura mater Body of vertebra Autonomic ganglion Spinal nerve (c) Posterior view of spinal cord and vertebra Figure 9-4c

CNS: Bone and Connective Tissue Dural Sinses drain CSF only between dura Cerebral hemispheres Cerebellum Cranium Cervical spinal nerves Dura mater Subdural space Subarachnoid space Pia mater Arachnoid membrane Brain (b) Meningeal layers of the brain cushion and protect delicate neural tissue. CENTRAL NERVOUS SYSTEM SECTIONAL VIEWS OF THE CNS ANATOMY SUMMARY Venous sinus Figure 9-4 (1 of 2)

CNS: Bone and Connective Tissue Cranium Dura mater Subdural space Subarachnoid space Pia mater Arachnoid membrane Brain (b) Meningeal layers of the brain cushion and protect delicate neural tissue. CENTRAL NERVOUS SYSTEM SECTIONAL VIEWS OF THE CNS ANATOMY SUMMARY Venous sinus Figure 9-4b

CNS: Ventricles of the Brain ANATOMY SUMMARY VENTRICLES OF THE BRAIN Cerebrum Lateral ventricles Third ventricle Fourth ventricle Cerebellum Central canal Spinal cord (a) Lateral view Frontal view Figure 9-5a

CNS: Cerebrospinal Fluid ANATOMY SUMMARY Cerebrospinal fluid CEREBROSPINAL FLUID CIRCULATION Arachnoid villi Bone of skull Dura mater Endothelial lining Choroid plexus of third ventricle Blood in venous sinus Fluid movement Pia mater Cerebral cortex Arachnoid villus Arachnoid membrane Dura mater (inner layer) Pia mater Subarachnoid space Arachnoid membrane Subdural space (d) (b) Sinus Choroid plexus of fourth ventricle Spinal cord Central canal Subarachnoid space Arachnoid membrane Dura mater Figure 9-5b-d

CNS: Cerebrospinal Fluid ANATOMY SUMMARY CEREBROSPINAL FLUID CIRCULATION Cerebrospinal fluid Bone of skull Dura mater Endothelial lining Blood in venous sinus Fluid movement Arachnoid villus Cerebral cortex Dura mater (inner layer) Pia mater Subarachnoid space Arachnoid membrane Subdural space (d) Figure 9-5d

CSF Flow

CNS: Blood-Brain Barrier ★★ Astrocyte foot processes secrete paracrines that promote tight junction formation. Astrocyte Tight junction prevents solute movement between endothelial cells. (a) Figure 9-6a

CNS: Blood-Brain Barrier Figure 9-6b

CNS: Neural Tissue – Metabolic Needs Oxygen Passes freely across blood-brain barrier Brain receives 15% of blood pumped by heart Glucose Brain responsible for about half of body’s glucose consumption Membrane transporters move glucose from plasma into the brain interstitial fluid Progressive hypoglycemia leads to confusion, unconsciousness, and death

Central nervous system, posterior view Spinal Cord: Overview Cerebral hemispheres Cerebellum Cranium Cervical spinal nerves Thoracic spinal Lumbar spinal Sacral spinal Coccygeal nerve (a) Posterior view Sectioned vertebrae CENTRAL NERVOUS SYSTEM ANATOMY SUMMARY Central nervous system, posterior view Figure 9-4a

Specialization in the spinal cord Spinal Cord: Anatomy Specialization in the spinal cord Gray matter White matter (a) One segment of spinal cord, ventral view, showing its pair of nerves. Dorsal root: carries sensory (afferent) information to CNS. Ventral root: carries motor (efferent) information to muscles and glands. Figure 9-7a

Spinal Cord: Anatomy Visceral sensory nuclei Somatic sensory nuclei (b) Gray matter consists of sensory and motor nuclei. Dorsal root ganglion Ventral root Ventral horn Lateral horn Dorsal horn Visceral sensory nuclei Somatic sensory nuclei Autonomic efferent nuclei Somatic motor nuclei Figure 9-7b

Propriospinal tracts remain within the cord Spinal Cord: Anatomy Propriospinal tracts remain within the cord Figure 9-7c (1 of 2)

Spinal Cord: Anatomy Figure 9-7c (2 of 2)

Spinal Cord: Integrating Center Sensory information goes to the brain Spinal cord Stimulus Sensory information Integrating center Interneuron Command to muscles or glands A spinal reflex initiates a response without input from the brain.★ Response Figure 9-8

Anatomy of the Brain Figure 9-9 ANATOMY SUMMARY ANATOMY OF THE BRAIN LATERAL VIEW OF THE CNS Frontal lobe Frontal lobe Cingulate gyrus Cerebrum Parietal lobe Parietal lobe Corpus callosum Thalamus Occipital lobe Occipital lobe Spinal cord Temporal lobe Cerebellum Temporal lobe Pons Cerebellum Pons Vertebrae Medulla oblongata Medulla oblongata (b) Lateral view of brain (c) Mid-sagittal view of brain Thalamus Cut edge of ascending tracts to cerebrum Optic tract Frontal bone Parietal bone Midbrain (a) Pons Temporal bone Cut edges of tracts leading to cerebellum Cranial nerves Occipital bone Medulla oblongata (d) Lateral view of brain stem (e) The skull Spinal cord Figure 9-9

The Brain: The Brain Stem Most cranial nerves originate along brain stem Cranial nerves can include sensory fibers, efferent fibers, or both (mixed nerves) Many nuclei are associated with reticular formation Medulla Somatosensory and corticospinal tracts in white matter - Pyramids

The Brain: The Brain Stem ANATOMY SUMMARY ANATOMY OF THE BRAIN Thalamus Cut edge of ascending tracts to cerebrum Optic tract Midbrain Pons Cut edges of tracts leading to cerebellum Cranial nerves Medulla oblongata (d) Lateral view of brain stem Spinal cord Figure 9-9d

The Brain: Cerebellum ANATOMY SUMMARY ANATOMY OF THE BRAIN Frontal lobe Parietal lobe Occipital lobe Temporal lobe Pons Cerebellum Medulla oblongata (b) Lateral view of brain Figure 9-9b

The Brain: Diencephalon Thalamus Epithalamus Hypothalamus Thalamus Hypothalamus Pineal gland Anterior pituitary Posterior pituitary Figure 9-10

The Brain: Hypothalamus Activates sympathetic nervous system Maintains body temperature Controls body osmolarity Controls reproductive functions Controls food intake Interacts with limbic system to influence behavior and emotions Influences cardiovascular control center in medulla oblongata Secretes trophic hormones that control release of hormones from anterior pituitary gland

The Brain: Mid-Sagittal View ANATOMY SUMMARY ANATOMY OF THE BRAIN Frontal lobe Cingulate gyrus Parietal lobe Corpus callosum Thalamus Occipital lobe Cerebellum Temporal lobe Pons Medulla oblongata (c) Mid-sagittal view of brain Figure 9-9c

The Brain: Gray Matter of the Cerebrum Basal ganglia Corpus callosum Lateral ventricle Tracts of white matter Tip of lateral ventricle Gray matter of cerebral cortex Figure 9-11

The Brain: Cell Bodies in the Cerebral Cortex Form Distinct Layers Figure 9-12

The Brain: The Limbic System Emotion, memory, and learning Cingulate gyrus plays a role in emotion. Thalamus Hippocampus is involved in learning and memory. Amygdala is involved in emotion and memory. Figure 9-13