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Home , Dorsal root ganglion, Ependyma, Ganglion, Gray ramus communicans, Ramus communicans

CHAPTER 3 BASIC AND

Nervous Tissue 66

Central 68

Peripheral Nervous System 72

Cranial Nerves 74

Clinical Correlates 103 3 GENERAL INFORMATION Nervous tissue is divided into 2 major types: ● ● Neuroglial cells (the neuroglia)

NEURONS The structural and functional cells in the nervous system Respond to a nervous stimulus and conduct the stimulus along the length of the cell A ’s cell body is called the perikaryon, or Cell bodies are classified by their location: ● —a collection of nerve cell bodies located in the peripheral nervous system (e.g., , , ) ● —a collection of nerve cell bodies located in the (e.g., Edinger-Westphal nucleus, chief sensory nucleus of cranial nerve V, motor nucleus of cranial nerve VII) Neuron’s cell bodies contain typical cellular organelles within their cytoplasm: ● Mitochondria ● Nucleus ● Nucleolus ● Ribosomes ● Rough endoplasmic reticulum (Nissl substance) ● Neurotubules ● Golgi apparatus ● Lysosomes Neurons have 2 types of processes that extend from the nerve cell body: ● —process that carries nerve impulses toward the nerve cell body; neurons may have multiple ● —process that carries nerve impulses away from the nerve cell body; neurons can have only 1 axon 3 major types of neurons: ● Unipolar—has only 1 process from the cell body (sensory neurons) ● Bipolar—has 2 processes from the cell body: 1 dendrite and 1 axon (sensory neurons; located only in the retina, olfactory epithelium, and the vestibular and cochlear ganglia) ● Multipolar—has 3 or more processes from the cell body: 2 or more dendrites and 1 axon (motor neurons and )

Dendrites Bipolar cell of cranial n. VIII Rough endoplasmic Dendritic spines Unipolar cell of reticulum (gemmules) Interneurons (Nissl substance) sensory ganglia Ribosomes Satellite cells Blood vessel Nucleus Myelinated fibers Nucleolus Axon Free nerve endings Encapsulated ending Specialized ending Neurotubules Golgi apparatus Cell body (soma) Multipolar somatic motor cell Lysosome Mitochondrion Collateral Myelinated somatic motor fiber sheath Red: Blue: Purple: Gray: Glial and Motor end Striated (voluntary) muscle neurilemmal plate with cells and myelin Schwann cell cap

66 NETTER’S HEAD AND FOR DENTISTRY Nervous Tissue 3 NEUROGLIA Neuroglia is the supporting nervous tissue for neurons, although neuroglial cells also have assistive roles in neuron function Neuroglial cells have only 1 type of process Classification: ● —located in the central nervous system; help keep neurons in place, provide nutritional support, regulate the extracellular matrix, form part of the blood- barrier ● —located in the central nervous system; responsible for axon myelination in the central nervous system; 1 oligodendrocyte can myelinate 1 segment of multiple ● —located in the central nervous system; responsible for phagocytosis to remove waste ● Schwann cells—located in the peripheral nervous system; responsible for axon myelination in the peripheral nervous system; 1 schwann cell can myelinate 1 segment of 1 axon ● Satellite cells—located in the peripheral nervous system; surround the nerve cell bodies of ganglia

Ventricle

Microglial cell

Neuron Oligodendrocyte

Axon Astrocyte Astrocyte foot process

Perivascular pericyte Capillary

BASIC NEUROANATOMY AND CRANIAL NERVES 67 3 Central Nervous System GENERAL INFORMATION The central nervous system is composed of the: ● Brain ●

Precentral gyrus Precentral sulcus Central sulcus Superior frontal gyrus Superior parietal lobule Intraparietal sulcus Inferior parietal Middle frontal gyrus lobule Angular gyrus

Inferior frontal gyrus

Frontal pole Occipital pole Anterior ramus Lateral (sylvian) fissure Ascending ramus Inferior temporal gyrus Posterior ramus Temporal pole Superior temporal gyrus

Parietal lobe

Frontal lobe Occipital lobe

Temporal lobe

Central sulcus of insula Circular sulcus of insula

Short gyri Insula Limen Long gyrus

68 NETTER’S HEAD AND NECK ANATOMY FOR DENTISTRY Central Nervous System 3 BRAIN CEREBRUM The surface of the of the brain is divided by: ● Gyri (singular gyrus)—the elevations of brain tissue on the surface ● Sulci (singular sulcus)—the grooves or fissures located between the gyri There are 3 large sulci that help divide the cerebral hemispheres into 4 of its lobes: ● Central sulcus (of Rolando)—divides frontal lobe from parietal lobe ● Lateral sulcus (of Sylvius)—divides the frontal and parietal lobes from the temporal lobe ● Parieto-occipital sulcus—divides the parietal lobe from the occipital lobe The brain is divided into 5 lobes: ● Frontal—motor movement, motor aspect of speech (Broca’s area), reasoning, emotions, personality, and problem solving ● Parietal—sensory perceptions related to , temperature, touch and pressure, spatial orientation and perception, sensory aspect of language (Wernicke’s area) ● Temporal—auditory perceptions, learning, and memory ● Occipital—vision ● Insula—associated with visceral functions including taste DIENCEPHALON Composed of 4 parts: ● —major relay center of the and parts of the motor system ● Hypothalamus—controls the and endocrine system ● Epithalamus—major structures include the pineal gland (which controls circadian rhythms) and the habenula ● Subthalamus—an extrapyramidal nucleus of the motor system; if lesioned, will result in a contralateral hemiballismus Composed of 3 parts: ● Midbrain ● Pons ● Medulla CEREBELLUM Part of the motor system Receives sensory input of all forms that use the deep cerebellar nuclei Associated with: ● Equilibrium ● Posture ● Tone of axial muscles ● Gait Corpus callosum

Interthalamic adhesion Cuneus Thalamus

Hypothalamic sulcus Lingual gyrus Optic AP

Pineal gland

Cerebellum

Pituitary gland (anterior and posterior) Midbrain Pons Medulla oblongata BASIC NEUROANATOMY AND CRANIAL NERVES 69 3 Central Nervous System SPINAL CORD The caudal continuation of the central nervous system Begins at the caudal end of the medulla and ends at vertebral level L1–2, tapering into the conus medullaris Has 2 enlargements associated with the limbs: ● Cervical—associated with the upper limb and found between the spinal cord at levels C4 to T1 ● Lumbosacral—associated with the lower limb and found between the spinal cord at levels L1 to S2 Composed of: ● Gray matter—location of nerve cell bodies and neuroglial cells ● —location of the axons and neuroglial cells Has 5 levels: ● Cervical—8 spinal nerves ● Thoracic—12 spinal nerves ● Lumbar—5 spinal nerves ● Sacral—5 spinal nerves ● Coccygeal—1

C1 1st cervical n. Cervical enlargement C7 8th cervical n. T1 1st thoracic n. Spinal dura mater Filaments of nerve root

T12 Lumbosacral enlargement 12th thoracic n. L1 1st lumbar n. Conus medullaris Cauda equina L5 5th lumbar n. S1 1st sacral n. Filum terminale 5th sacral n. Coccygeal n. Coccyx

70 NETTER’S HEAD AND NECK ANATOMY FOR DENTISTRY Central Nervous System 3 SPINAL CORD CONTINUED

Posterior view

Rami communicantes

Dura mater Dorsal root Dorsal root (spinal) ganglion

Arachnoid

Subarachnoid space

Pia mater (overlying spinal cord)

Filaments of dorsal root

Denticulate ligament

Anterior view Gray matter

Filaments of dorsal root White matter Dorsal root Dorsal root (spinal) ganglion Ventral root Spinal nerve Filaments of ventral root Anterior median fissure

Sections through spinal cord at various levels

C5 T2 T8

L1 L3 S1

S3

BASIC NEUROANATOMY AND CRANIAL NERVES 71 3 Peripheral Nervous System GENERAL INFORMATION Peripheral nervous system is that portion of the nervous system located external to the central nervous system Consists of: ● Cranial nerves—12 pairs ● Spinal nerves—31 pairs Can be subdivided into: ● —voluntary system associated with afferent (sensory) and efferent (motor) fibers ● Autonomic nervous system—involuntary system associated with homeostasis of the body

Sensory Motor Preganglionic sympathetic Postganglionic Dorsal Dorsal sympathetic column root Dorsal root ganglion Vascular smooth muscle, sweat glands, and Dorsal arrector pili ramus muscles in skin Skeletal muscle Ventral ramus Gray Ventral root Sympathetic chain ganglion Free White ramus endings Splanchnic nerve communicans Sympathetic chain Collateral sympathetic ganglion Preganglionic sympathetic neurons Skeletal passing to in another muscle sympathetic chain ganglion Neuroeffector junctions on smooth Sensory neuron of muscle, cardiac muscle, secretory abdominal viscera glands, metabolic cells, immune cells

72 NETTER’S HEAD AND NECK ANATOMY FOR DENTISTRY Peripheral Nervous System 3 SPINAL NERVES AND CRANIAL NERVES

Oculomotor (III) n. Facial (VII) n. Intracranial vessels Glossopharyngeal (IX) n. Eye Ciliary ganglion Medulla oblongata Lacrimal gland Vagus (X) n. Pterygopalatine Parotid gland C1 ganglion C2 Sublingual and C3 submandibular glands C4 Submandibular Peripheral cranial

C5 ganglion Gray blood vessels C6 Larynx C7 C8 Trachea Bronchi and lungs Sweat T1 gland T2 T3 Heart T4 Greater Celiac thoracic ganglion Shown Peripheral T5 splanchnic n. vessel Stomach for only T6 1 segment Liver T7 c n. Gallbladder T8 Bile ducts Lesser thoracic splanchni T9 Rami communicantes gray and white Pancreas Sup. mesenteric Hair T10 ganglion Adrenal glands follicle Brown fat T11 Lowest thoracic splanchnic n. Kidneys T12

L1 Lumbar Intestines L2 splanchnic nn. L3 Lymphoid organs Sup. Inf. L4 hypogastric mesenteric Gray plexus ganglion Distal colon L5 Hypogastric S1 nn. Bladder S2 S3 Pelvic splanchnic nn. S4 S5 Sympathetic External genitalia Coccyx Inf. hypogastric trunk (pelvic) plexus

Sympathetic fibers Parasympathetic fibers preganglionic preganglionic postganglionic postganglionic

BASIC NEUROANATOMY AND CRANIAL NERVES 73