BIOLOGY II: Human Anatomy &Physiology Chapter 11
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BIOLOGY II: Human Anatomy &Physiology Chapter 11 Nervous System II: Divisions of the Nervous System 1 11.1: Introduction The central nervous system (CNS) consists of the brain and spinal cord. The brainstem connects the brain to the spinal cord. Communication to the peripheral nervous system (PNS) is by way of the spinal cord. 2 11.2: The Meninges The meninges Membranes of CNS Protect the CNS Three (3) layers: Dura mater “Tough mother” Venous sinuses Arachnoid mater “Spider mother” Space contains cerebrospinal fluid (CSF) Pia mater “Little mother” Encapsulates blood vessels 3 Meninges of the Spinal Cord Spinal cord Ventral root Dorsal root Spinal nerve Dorsal root ganglion Subarachnoid space Pia mater Arachnoid mater Epidural space Dura mater Dorsal root Dorsal branch (dorsal ramus) Spinal nerve Ventral branch (ventral ramus) Dorsal root ganglion Spinal cord Ventral root Epidural space Thoracic vertebra (a) (b) Body of vertebra 4 11.3: Ventricles and Cerebrospinal Fluid There are four (4) ventricles The ventricles are interconnected cavities within cerebral hemispheres and brain stem Lateral ventricle Interventricular foramen Third ventricle The ventricles are continuous with the central canal of the spinal cord Cerebral aqueduct Fourth ventricle They are filled with cerebrospinal fluid (CSF) The four (4) ventricles are: Lateral ventricles (2) Known as the first and second ventricles Third ventricle Fourth ventricle Interventricular foramen Cerebral aqueduct To central canal of spinal cord (a) Interventricular foramen Lateral ventricle Third ventricle Cerebral aqueduct Fourth ventricle 5 (b) To central canal of spinal cord Cerebrospinal Fluid Secreted by the choroid plexus (Can you recall the specific cells?) Circulates in ventricles, central canal of spinal cord, and the subarachnoid space Completely surrounds the brain and spinal cord Excess or wasted CSF is absorbed by the arachnoid villi (And where are these located?) Clear fluid similar to blood plasma Volume is only about 120 ml. Nutritive and protective Helps maintain stable ion concentrations in the CNS Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arachnoid granulations Blood-filled dural sinus Choroid plexuses of third ventricle Pia mater Third ventricle Cerebral aqueduct Fourth ventricle Subarachnoid space Arachnoid mater Dura mater Choroid plexus of fourth ventricle Central canal of spinal cord Pia mater Subarachnoid space Filum terminale Arachnoid mater Dura mater 6 11.4 Spinal Chord Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Slender column of nervous tissue continuous with brain and brainstem Extends downward through vertebral canal Begins at foramen magnum and ends at L1/L2 interspace Conduit for nerve impulses to and from brain and brainstem Center for spinal reflexes Brainstem Foramen magnum Cervical enlargement Cervical enlargement Spinal cord Vertebral canal Lumbar enlargement Lumbar enlargement Conus medullaris Cauda equina Conus medullaris Filum terminale 7 (a) (b) Structure of the Spinal Cord Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior horn Posterior funiculus Posterior median sulcus White matter Gray matter Gray commissure Lateral funiculus Dorsal root of spinal nerve Central canal Anterior funiculus Dorsal root ganglion Ventral root Anterior of spinal nerve horn (a) Anterior median fissure Portion of spinal nerve 8 Reflex Arcs Reflexes are automatic, subconscious responses to stimuli within or outside the body Simple reflex arc (sensory – motor) Most common reflex arc (sensory – association – motor) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sensory or afferent neuron Receptor Central Nervous System Motor or efferent neuron Effector (muscle or gland) 12 9 (a) Reflex Arcs 10 General Components of a Spinal Reflex Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spinal cord Interneuron Dorsal 1 Receptor 3 2 Sensory neuron Cell body of sensory neuron White matter Gray matter 4 Ventral Motor neuron Central canal 5 Effector (muscle or gland) (b) 11 Reflex Behavior Example is the knee-jerk reflex Simple monosynaptic reflex Helps maintain an upright posture Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Axon of sensory neuron Cell body of sensory neuron Spinal cord Cell body of motor neuron Axon of motor neuron Direction of impulse Effector (quadriceps femoris muscle group) Receptor associated with dendrites of sensory neuron Patella Patellar ligament 12 Reflex Behavior Example is a withdrawal reflex Prevents or limits tissue damage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell body of sensory neuron Axon of sensory neuron Direction of impulse Dendrite of sensory neuron Pain receptor in skin Tack Effector (flexor muscle contracts and withdraws part being stimulated) Interneuron Axon of motor neuron Spinal cord Cell body of motor neuron 13 Reflex Arc Example crossed extensor reflex Crossing of sensory impulses within the reflex center to produce an opposite effect Interneuron + = Stimulation – = Inhibition – + – Sensory neuron Extensor relaxes + Extensor contracts Flexor relaxes Motor neurons Motor neurons Flexor contracts 14 17 Tracts of the Spinal Cord Ascending tracts (dorsal) conduct sensory impulses to the brain Descending tracts (ventral) conduct motor impulses from the brain to motor neurons reaching muscles and glands Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dorsal column Fasciculus gracilis Fasciculus cuneatus Posterior spinocerebellar tract Lateral corticospinal tract Lateral reticulospinal tract Rubrospinal tract Anterior spinocerebellar tract Anterolateral system Lateral spinothalamic tract Anterior spinothalamic tract Anterior reticulospinal tract Medial reticulospinal tract Anterior corticospinal tract 15 Nerve Tracts of the Spinal Cord 16 11.5: Brain Functions of the brain: • Interprets sensations Determines perception Stores memory Reasoning Makes decisions Coordinates muscular movements Regulates visceral activities Determines personality Major parts of the brain: Cerebrum Frontal lobes Parietal lobes Occipital lobes Temporal lobes Insula Diencephalon Cerebellum Brainstem Midbrain Pons Medulla oblongata 17 The Brain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gyrus Skull Sulcus Meninges Cerebrum Corpus callosum Diencephalon Fornix Midbrain Brainstem Pons Cerebellum Medulla oblongata Spinal cord (a) Fornix Cerebrum Midbrain Pons Corpus callosum Transverse fissure Diencephalon Cerebellum Medulla oblongata Spinal cord 18 (b) b: © Martin M. Rotker/Photo Researchers, Inc. Structure of the Cerebrum Corpus callosum Connects cerebral hemispheres (a commissure) Gyri Bumps or convolutions Sulci Grooves in gray matter Central sulcus of Rolando Fissures Longitudinal: separates the cerebral hemispheres Transverse: separates cerebrum from cerebellum Lateral fissure of Sylvius Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Parietal lobe Gyrus Sulcus Frontal lobe Lateral sulcus Occipital lobe Transverse fissure Cerebellar hemisphere Temporal lobe (a) Central sulcus Parietal lobe Central sulcus Longitudinal fissure Parietal lobe Occipital lobe (b) Occipital lobe Frontal lobe Insula Retracted temporal lobe (c) 19 Split Brain Research The following videos give some idea as to what occurs on each side of the brain and what happens when the corpus callosum is severed (video 1) or missing altogether (video 2). http://www.youtube.com/watch?v=lfGwsAdS9Dc&feature =related http://www.youtube.com/watch?v=VHgClWAPbBY&feat ure=related 20 Lobes of the Cerebrum Five (5) lobes bilaterally: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Frontal lobe Parietal lobe Temporal lobe Occipital lobe Insula aka ‘Island of Reil’ (functions in Frontal lobe interoceptive awarenessInsula Retracted & judging intensity of temporal lobe pain, among other (c) things) Central sulcus Parietal lobe Occipital lobe 21 Functions of the Cerebrum Interpreting impulses Initiating voluntary movements Storing information as memory Retrieving stored information Reasoning Seat of intelligence and personality 22 Functional Regions of the Cerebral Cortex Cerebral cortex Thin layer of gray matter that constitutes the outermost portion of cerebrum Contains 75% of all neurons in the nervous system Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Motor areas involved with the control of voluntary muscles Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Visual area Interpretation of auditory patterns Cerebellum 23 Temporal lobe Brainstem Functions of the Cerebral Lobes 24 Sensory Areas (post-central sulcus) Interprets hearing Cutaneous sensory area Parietal lobe Interprets sensations on skin Sensory area for taste Visual area Occipital lobe Interprets vision Auditory area Temporal lobe Near base of the central sulcus Sensory area for smell Central sulcus Motor areas involved with the control of voluntary muscles Concentration, planning, problem solving Sensory areas involved with cutaneous and other senses Arises from centers deep within the cerebrum Frontal eye field Parietal lobe Auditory area Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Visual area Interpretation of auditory patterns Cerebellum Temporal lobe Brainstem 25 Motor & Sensory Areas Arm Forearm Trunk Trunk Pelvis Neck Forearm Arm Thigh Pelvis Thigh Thumb, fingers, and hand Leg Foot and toes Facial expression Hand, fingers, and thumb Upper face Leg Foot and toes Genitals Lips Salivation Vocalization Mastication Teeth and gums Swallowing Tongue and pharynx Longitudinal fissure (a) Motor area Longitudinal fissure (b) Sensory area Frontal lobe Motor area Sensory area Central sulcus Parietal lobe 26 Association Areas Regions that are not primary motor or primary sensory areas Widespread throughout the cerebral cortex Analyze and interpret sensory experiences Provide memory, reasoning, verbalization, judgment, emotions Copyright © The McGraw-Hill Companies, Inc. 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Central sulcus Motor areas involved with the control of voluntary muscles Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Visual area Interpretation of auditory patterns Cerebellum Temporal lobe Brainstem 27 Association Areas Frontal lobe association areas Concentrating Planning Complex problem solving Parietal lobe association areas Understanding speech Choosing words to express thought Interpret complex sensory experiences Store memories of visual scenes, music, and complex patterns Occipital lobe association areas Analyze and combine visual images with other sensory experiences Temporal lobe association areas 28 Motor Areas (pre-central sulcus) Primary motor areas Frontal lobes Control voluntary muscles Broca’s area Copyright © The McGraw-Hill Companies, Inc. 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Central sulcus Motor areas involved with the control of voluntary muscles Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Anterior to primary motor cortex Usually in left hemisphere Controls muscles needed for speech Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Visual area Interpretation of auditory patterns Frontal eye field Cerebellum Temporal lobe Brainstem Above Broca’s area Controls voluntary movements of eyes and eyelids 29 Hemisphere Dominance The left hemisphere is dominant in most individuals Dominant hemisphere controls: Speech Writing Reading Verbal skills Analytical skills Computational skills Nondominant hemisphere controls: Nonverbal tasks Motor tasks Understanding and interpreting musical and visual patterns Provides emotional and intuitive thought processes 30 Memory Short term memory Working memory Closed neuronal circuit Circuit is stimulated over and over When impulse flow ceases, memory does also unless it enters long-term memory via memory consolidation Limited to 7 bits of information Long term memory Changes structure or function of neurons Enhances synaptic transmission 31 Basal Nuclei Masses of gray matter Deep within cerebral hemispheres Produce dopamine Control certain muscular activities Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Longitudinal fissure Right cerebral hemisphere Caudate nucleus Basal nuclei Primarily by inhibiting motor functions Putamen Globus pallidus Thalamus Cerebellum Hypothalamus Brainstem Spinal cord 32 Diencephalon Between cerebral hemispheres and above the brainstem Surrounds the third ventricle Thalamus Epithalamus Hypothalamus Optic tracts Optic chiasm Infundibulum Posterior pituitary Mammillary bodies Pineal gland Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior colliculus Corpora quadrigemina Optic nerve Inferior colliculus Optic chiasma Pituitary gland Mammillary body Optic tract Pons Cerebral peduncles Pyramidal tract Thalamus Third ventricle Pineal gland Fourth ventricle Olive Cerebellar peduncles Medulla oblongata Spinal cord (a) (b) 33 Diencephalon Thalamus Gateway for sensory impulses heading to cerebral cortex Receives all sensory impulses (except smell) Channels impulses to appropriate part of cerebral cortex for interpretation Epithalamus Functions to connect the limbic system to other parts of the brain. Hypothalamus Maintains homeostasis by regulating visceral activities Links nervous and endocrine systems (hence some say the neuroendocrine system) 34 Diencephalon The Limbic System Consists of: Portions of frontal lobe Portions of temporal lobe Hypothalamus Thalamus Basal nuclei Other deep nuclei Functions: Controls emotions Produces feelings Interprets sensory impulses 35 Brainstem Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hypothalamus Three parts: Midbrain Pons Medulla Oblongata Diencephalon Thalamus Corpus callosum Corpora quadrigemina Midbrain Cerebral aqueduct Pons Reticular formation Medulla oblongata Spinal cord 36 Midbrain Between diencephalon and pons Contains bundles of fibers that join lower parts of brainstem and spinal cord with higher parts of the brain Cerebral aqueduct Cerebral peduncles (bundles of nerve fibers) Corpora quadrigemina (centers for visual and auditory reflexes) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior colliculus Corpora quadrigemina Optic nerve Inferior colliculus Optic chiasma Pituitary gland Thalamus Mammillary body Third ventricle Optic tract Pons Cerebral peduncles Pineal gland Fourth ventricle Pyramidal tract Olive Cerebellar peduncles Medulla oblongata Spinal cord (a) (b) 37 Pons Rounded bulge on underside of brainstem Between medulla oblongata and midbrain Helps regulate rate and depth of breathing Relays nerve impulses to and from medulla oblongata and cerebellum (bridge) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior colliculus Corpora quadrigemina Optic nerve Inferior colliculus Optic chiasma Pituitary gland Thalamus Mammillary body Third ventricle Optic tract Pons Cerebral peduncles Pineal gland Fourth ventricle Pyramidal tract Olive Cerebellar peduncles Medulla oblongata Spinal cord (a) (b) 38 Medulla Oblongata Enlarged continuation of spinal cord Conducts ascending and descending impulses between brain and spinal cord Contains cardiac, vasomotor, and respiratory control centers Contains various nonvital reflex control centers (coughing, sneezing, swallowing, and vomiting) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior colliculus Corpora quadrigemina Optic nerve Inferior colliculus Optic chiasma Pituitary gland Thalamus Mammillary body Third ventricle Optic tract Pons Cerebral peduncles Pineal gland Fourth ventricle Pyramidal tract Olive Cerebellar peduncles Medulla oblongata Spinal cord (a) (b) 39 Reticular Formation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Complex network of nerve fibers scattered throughout the brain stem Extends into the diencephalon Connects to centers of hypothalamus, basal nuclei, cerebellum, and cerebrum Filters incoming sensory information Arouses cerebral cortex into state of wakefulness Hypothalamus Diencephalon Thalamus Corpus callosum Corpora quadrigemina Midbrain Cerebral aqueduct Pons Reticular formation Medulla oblongata Spinal cord 40 Types of Sleep Slow wave Non-REM sleep Person is tired Decreasing activity of reticular system Restful Dreamless Reduced blood pressure and respiratory rate Ranges from light to heavy Alternates with REM sleep Rapid Eye Movement (REM) Paradoxical sleep Some areas of brain active Heart and respiratory rates irregular Dreaming occurs 41 Cerebellum Inferior to occipital lobes Posterior to pons and medulla oblongata Two hemispheres like cerebrum Vermis connects hemispheres Cerebellar cortex (gray matter) Arbor vitae (white matter) Cerebellar peduncles (nerve fiber tracts) Dentate nucleus (largest nucleus in cerebellum) Integrates sensory information concerning position of body parts Coordinates skeletal muscle activity Maintains posture Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Longitudinal fissure Corpus callosum Thalamus Superior peduncle Pons Middle peduncle Inferior peduncle Cerebellum Medulla oblongata 42 Major Parts of the Brain 43 11.6: Peripheral Nervous System Cranial nerves arising from the brain Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera Spinal nerves arising from the spinal cord Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera 44 Nervous System Subdivisions 45 Structure of a Peripheral Nerve Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fascicle Peripheral nerve Epineurium Motor neuron ending Axon Perineurium Endoneurium Node of Ranvier Schwann cell Sensory receptor Myelin sheath Neurilemma 46 Nerve and Nerve Fiber Classification Sensory nerves Conduct impulses into brain or spinal cord Motor nerves Conduct impulses to muscles or glands Mixed (both sensory and motor) nerves Contain both sensory nerve fibers and motor nerve fibers Most nerves are mixed nerves ALL spinal nerves are mixed nerves (except the first pair) 47 Nerve Fiber Classification General somatic efferent (GSE) fibers Carry motor impulses from CNS to skeletal muscles General visceral efferent (GVE) fibers Carry motor impulses away from CNS to smooth muscles and glands General somatic afferent (GSA) fibers Carry sensory impulses to CNS from skin and skeletal muscles General visceral afferent (GVA) fibers Carry sensory impulses to CNS from blood vessels and internal organs 48 Nerve Fiber Classification Special somatic efferent (SSE) fibers Carry motor impulses from brain to muscles used in chewing, swallowing, speaking and forming facial expressions Special visceral afferent (SVA) fibers Carry sensory impulses to brain from olfactory and taste receptors Special somatic afferent (SSA) fibers Carry sensory impulses to brain from receptors of sight, hearing and equilibrium 49 Cranial Nerves Copyright © The McGraw-Hill Companies, Inc. 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Olfactory bulb Olfactory (I) Olfactory tract Optic (II) Optic tract Oculomotor (III) Trochlear (IV) Trigeminal (V) Vestibulocochlear (VIII) Abducens (VI) Hypoglossal (XII) Facial (VII) Vagus (X) Glossopharyngeal (IX) Accessory (XI) 50 Cranial Nerves I and II Olfactory nerve (CN I) Sensory nerve Fibers transmit impulses associated with smell Optic nerve (CN II) Sensory nerve Fibers transmit impulses associated with vision 51 Cranial Nerves III and IV Oculomotor nerve (CN III) Primarily motor nerve Motor impulses to muscles that: Raise eyelids Move the eyes Focus lens Adjust light entering eye Some sensory Proprioceptors Trochlear nerve (CN IV) Primarily motor nerve Motor impulses to muscles that move the eyes Some sensory Proprioceptors 52 Cranial Nerve V Trigeminal nerve (CN V) Mixed nerve “Three (3) sisters” (1) Ophthalmic division Sensory from surface of eyes, tear glands, scalp, forehead, and upper eyelids (2) Maxillary division Sensory from upper teeth, upper gum, upper lip, palate, and skin of face (3) Mandibular division Sensory from scalp, skin of jaw, lower teeth, lower gum, and lower lip Motor to muscles of mastication and muscles in floor of mouth Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lacrimal nerve Ophthalmic division Lacrimal gland Eye Maxillary division Infraorbital nerve Mandibular division Maxilla Lingual nerve Inferior alveolar nerve Tongue Mental nerve 53 Mandible Cranial Nerves VI and VII Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Abducens nerve (CN VI) Primarily motor nerve Motor impulses to muscles that move the eyes Some sensory Proprioceptors Facial nerve (CN VII) Mixed nerve Sensory from taste receptors Motor to muscles of facial expression, tear glands, and salivary glands Temporal nerve Zygomatic nerve Buccal nerve Facial nerve Posterior auricular nerve Parotid salivary gland Mandibular nerve Cervical nerve 54 68 Cranial Nerves VIII and IX Vestibulocochlear nerve (CN VIII) Aka acoustic or auditory nerve Sensory nerve Two (2) branches: Vestibular branch Sensory from equilibrium receptors of ear Cochlear branch Sensory from hearing receptors Glossopharyngeal nerve (CN IX) Mixed nerve Sensory from pharynx, tonsils, tongue and carotid arteries Motor to salivary glands and muscles of pharynx 55 Cranial Nerve X Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Meningeal branch Vagus nerve (CN X) Mixed nerve Somatic motor to muscles of speech and swallowing Autonomic motor to viscera of thorax and abdomen Sensory from pharynx, larynx, esophagus, and viscera of thorax and abdomen Auricular branch Pharyngeal branch Superior ganglion of vagus nerve Inferior ganglion of vagus nerve Palate Nerve XI Superior laryngeal nerve Nerve XII Carotid body Recurrent laryngeal nerve Left vagus nerve Cardiac nerves Lung Heart Stomach Liver Spleen Pancreas Kidney Small intestine 56 Large intestine Cranial Nerves XI and XII Accessory nerve (CN XI) Primarily motor nerve We called this “Spinal” Accessory because: Cranial branch Motor to muscles of soft palate, pharynx and larynx Spinal branch Motor to muscles of neck and back Some sensory Proprioceptor Hypoglossal nerve (CN XII) Primarily motor Motor to muscles of the tongue Some sensory Proprioceptor 57 Functions of Cranial Nerves 58 Spinal Nerves Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ALL are mixed nerves (except the first pair) 31 pairs of spinal nerves: 8 cervical nerves (C1 to C8) 12 thoracic nerves T6 T7 Thoracic nerves T8 (L1 to L5) T9 T10 T11 5 sacral nerves (Co or Cc) Cervical nerves T5 5 lumbar nerves 1 coccygeal nerve Posterior view T3 T4 (T1 to T12) (S1 to S5) C1 C2 C3 C4 C5 C6 C7 C8 T1 T2 T12 L1 Cauda equina L2 L3 L4 Lumbar nerves L5 S1 S2 S3 S4 S5 Co Sacral nerves Coccygeal nerve 59 Spinal Nerves Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dorsal root Dorsal root (aka posterior root) Sensory root Axons of sensory neurons are in the dorsal root ganglion Dorsal root ganglion Aka DRG Cell bodies of sensory neurons whose axons conduct impulses inward from peripheral body parts Dorsal root ganglion Dorsal root Dorsal branch of spinal nerve Ventral branch of spinal nerve Ventral root Paravertebral ganglion Posterior median sulcus Posterior horn Visceral branch of spinal nerve (b) Lateral horn Ventral branch of spinal nerve (ventral ramus) Anterior horn Central canal Dorsal branch of spinal nerve (dorsal ramus) Anterior median fissure Paravertebral ganglion (a) Ventral root Spinal nerve Visceral branch of spinal nerve 60 Dermatome An area of skin that the sensory nerve fibers of a particular spinal nerve innervate Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. C2 C3 C4 C5 C6 C7 C2 C3 C4 C5 T1 T1 C8 C6 T1 T12 L1 T12 S1 S2 S3 S4 S5 C0 L1 S2 C6 C7 L2 S3 L3 L5 L1 L2 L4 C8 L3 L5 S1 L4 L5 (a) (b) 61 Spinal Nerves Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dorsal root Ventral root (aka anterior root) Motor root Axons of motor neurons whose cell bodies are in the spinal cord Spinal nerve Union of ventral root and dorsal roots Hence we now have a “mixed” nerve Dorsal root ganglion Dorsal root Dorsal branch of spinal nerve Ventral branch of spinal nerve Ventral root Paravertebral ganglion Posterior median sulcus Posterior horn Visceral branch of spinal nerve (b) Lateral horn Ventral branch of spinal nerve (ventral ramus) Anterior horn Central canal Dorsal branch of spinal nerve (dorsal ramus) Anterior median fissure Paravertebral ganglion (a) Ventral root Spinal nerve Visceral branch of spinal nerve 62 Nerve Plexuses Nerve plexus Complex networks formed by anterior branches of spinal nerves The fibers of various spinal nerves are sorted and recombined There are three (3) nerve plexuses: (1) Cervical plexus – Lies deep within the neck (2) Brachial plexus – Lies deep within shoulders (3) Lumbosacral plexus – Extends from lumbar region into pelvic cavity 63 Plexuses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior view Musculocutaneous nerve Axillary nerve Radial nerve Median nerve Ulnar nerve Phrenic nerve C1 C2 C3 C4 C5 C6 C7 C8 T1 Cervical plexus (C1–C4) Brachial plexus (C5–T1) T2 T3 T4 T5 T6 T7 Intercostal nerves T8 T9 T10 T11 T12 Cauda equina L1 L2 L3 L4 Femoral nerve L5 S1 S2 S3 S4 S5 Obturator nerve Lumbosacral plexus (T12–S5) Co Sciatic nerve 64 11.7: Autonomic Nervous System Functions without conscious effort Controls visceral activities Regulates smooth muscle, cardiac muscle, and glands Efferent fibers typically lead to ganglia outside of the CNS Two autonomic divisions regulate: Sympathetic division (speeds up) Prepares body for ‘fight or flight’ situations Parasympathetic division (pauses or slows down) Prepares body for ‘resting and digesting’ activities 65 Sympathetic Division Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lacrimal gland Eye Parotid gland, submandibular and sublingual glands Blood vessels Heart Celiac and pulmonary plexuses Trachea Lungs Skin Celiac ganglion Fibers to skin, blood vessels, and adipose tissue Liver Gallbladder Superior mesenteric ganglion Stomach Pancreas Small intestine Large intestine Spinal cord Inferior mesenteric ganglion Adrenal gland Kidney Sympathetic chain ganglia Urinary bladder Preganglionic Postganglionic neuron neuron Ovary Penis Uterus Scrotum 66 Parasympathetic Division Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sphenopalatine ganglion Lacrimal gland Ciliary ganglion Cranial nerve III Submandibular and sublingual glands Submandibular ganglion Cranial nerve VII Eye Parotid gland Otic ganglion Cranial nerve IX Heart Cranial nerve X (Vagus) Trachea Lung Cardiac and pulmonary plexuses Liver Gallbladder Stomach Celiac plexus Spleen Pancreas Superior hypogastric plexus Spinal cord Small intestine Large intestine Inferior hypogastric plexus Kidney Pelvic nerves Urinary bladder Preganglionic Postganglionic neuron neuron Scrotum Uterus Penis Ovary 67 Control of Autonomic Activity Controlled largely by CNS Medulla oblongata regulates cardiac, vasomotor and respiratory activities Hypothalamus regulates visceral functions, such as body temperature, hunger, thirst, and water and electrolyte balance Limbic system and cerebral cortex control emotional responses 68 11.8: Lifespan Changes Brain cells begin to die before birth Over average lifetime, brain shrinks 10% Most cell death occurs in temporal lobes By age 90, frontal cortex has lost half its neurons Number of dendritic branches decreases Decreased levels of neurotransmitters Fading memory Slowed responses and reflexes Increased risk of falling Changes in sleep patterns that result in fewer sleeping hours 69 Important Points in Chapter 11: Outcomes to be Assessed 11.1: Introduction Describe the general structure of the brain. Describe the relationship among the brain, brainstem, and spinal cord. 11.2: Meninges Describe the coverings of the brain and spinal cord. 11.3: Ventricles and Cerebrospinal Fluid Describe the formation and function of cerebrospinal fluid. 11.4: Spinal Cord Describe the structure of the spinal cord and its major functions. Describe a reflex arc. Describe reflex behavior. 11.5: Brain Name the major parts of the brain and describe the functions of each. Distinguish among motor, sensory, association areas of the cerebral cortex. 70 Important Points in Chapter 11: Outcomes to be Assessed Explain hemisphere dominance. Explain stages in memory storage. Explain the functions of the limbic system and reticular formation. 11.6: Peripheral Nervous System List the major parts of the peripheral nervous system. Describe the structure of a peripheral nerve and how its fibers are classified. Name the cranial nerves and list their major functions. Explain how spinal nerves are named and their functions 11.7: Autonomic Nervous System Describe the general characteristics of the autonomic nervous system. Distinguish between the sympathetic and the parasympathetic divisions of the autonomic nervous system. Describe a sympathetic and a parasympathetic nerve pathway. Explain how the autonomic neurotransmitters differently affect visceral effectors 71
