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Chapter 4 Central Nervous System and Sensory Organs © David G. Ward © David Dendrites of Neuron Showing Dendritic Spines (Brighteld, Silver, x1880) 79 Sensory and Motor Neurons Cell Body Synaptic Bulb Dendrite / Receptor Axon (Central Process) Axon (Peripheral Process) Figure 4.1: Unipolar neuron (sensory). © David G. Ward. Dendrites Dendrites Cell Body Axon Hillock Synaptic Bulb Dendrites Axon Figure 4.2: Multipolar neuron (motor). © David G. Ward. 80 Chapter 4: Central Nervous System and Sensory Organs Communication Between Neurons Cell Body Dendrites Axon Cell Body Enlargement Synaptic Axon Synaptic Bulb Hillock Vesicles Synaptic Bulb Presynaptic Axon Membrane Postsynaptic Membrane Dendrite Synaptic Cleft Figure 4.3: Synaptic communication. © David G. Ward. Synaptic Bulb* Axon Dendrite Dendrite Synaptic Bulb* Synaptic Bulb Nucleus Axon Synaptic Vessicles *The synaptic bulbs are from other neurons communicating with this neuron. Presynaptic Membrane Figure 4.4: Mutlipolar neuron. Figure 4.5: Synaptic bulb. © David G. Ward. © David G. Ward. Chapter 4: Central Nervous System and Sensory Organs 81 Motor Neurons, Glial and Schwann Cells Multipolar Neurons Glial Cells Figure 4.6: Spinal multipolar neurons. © David G. Ward. Node Node Schwann Cell Axon Endoneurium Axon Myelin Sheath Figure 4.7: Myelinated neuron. © David G. Ward. Axon Node Axon Schwann Cell Schwann Cell 400x+ Axon Schwann Cell / Myelin Sheath Figure 4.8: Schwann cell. © David G. Ward. 82 Chapter 4: Central Nervous System and Sensory Organs Nerve and Schwann Cells Fascicle Perineurium Epineurium Perineurium Epineurium Fascicle Figure 4.9: Nerve cell, histology. © David G. Ward. Epineurium Perineurium Endoneurium Axons Perineurium Perineurium Fascicle Figure 4.10: Nerve. Figure 4.11: Nerve fascicle. © David G. Ward. © David G. Ward. NodeNode Endoneurium Endoneurium Axons Node Schwann Cells Myelin Sheaths Figure 4.12: Schwann cells and axons. Figure 4.13: Schwann cells. © David G. Ward. © David G. Ward. Chapter 4: Central Nervous System and Sensory Organs 83 Neuromuscular Junctions and Motor Units Axon of Motor Neuron Skeletal Muscle Cells Axon of Motor Neuron Synaptic Bulbs Motor End Plate Motor End Plate Figure 4.14: Neuromuscular junctions. © David G. Ward. Alpha Motor Neurons Anterior Large Motor Unit Horn (1 alpha motor neuron, many skeletal muscle cells) Small Motor Unit (1 alpha motor neuron, 1 skeletal muscle cell) Figure 4.15: Motor units. © David G. Ward. 84 Chapter 4: Central Nervous System and Sensory Organs Spinal Cord Central Canal Dorsal Horn Dorsal Root White Matter Gray Matter Ventral Horn Ventra Median Ventral Root Sulcus Figure 4.16: Cross section with meninges. © David G. Ward. Dorsal Horn Dorsal Root Pia Mater Dura Mater Arachnoid Dorsal Root Ganglion Figure 4.17: Meninges. © David G. Ward. Ventral Root Ventral Horn Figure 4.18: Horns and roots. © David G. Ward. Chapter 4: Central Nervous System and Sensory Organs 85 Brain Optic a. b. Cerebrum Chiasma Pyramids Optic Nerve Cerebellum c. d. Cerebrum Gyrus (Raised) Corpus Callosum Transverse Longitudinal Fissure Fissure Cerebellum Olfactory Sulcus Hypothalamus Blub Pons (Recessed) Medulla Thalamus e. Parietal f. Cerebrum Lobe Medulla Cerebellum Pons Frontal Lobe Temporal Lobe Spinal Cord Figure 4.19: Brain. © NCSU. 86 Chapter 4: Central Nervous System and Sensory Organs Figure 4.20: Spinal cord divisions. © NCSU. Chapter 4: Central Nervous System and Sensory Organs 87 Parasympathetic Ganglia and Neurotransmitters Parasympathetic Ciliary, Sphenopalatine, Preganglionic Submandibular and Otic Neurons Ganglia Organs of the Head Parasympathetic Postganglionic Neuron Middle Medulla Thoracic and Abdominal Thoracic and Abdominal Organs Intramural Ganglia Parasympathetic Parasympathetic Preganglionic Postganglionic Neurons Neuron Pelvic Pelvic Organs Intramural Ganglia Sacral Spinal Cord Parasympathetic Postganglionic Neuron Figure 4.21: Parasympathetic ganglia. © David G. Ward. Acetylcholine Parasympathetic Preganglionic Neuron Cholinergic Muscarinic Middle Medulla Receptors Enlargement Acetylcholine Target Organ Cholinergic Enlargement Nicotinic-N Intramural Parasympathetic Receptors Ganglion Postganglionic Neuron Figure 4.22: Parasympathetic neurotransmitters. © David G. Ward. 88 Chapter 4: Central Nervous System and Sensory Organs Sympathetic Nervous System Impulse Conduction Synaptic Knob Axon Mitochondrion Endoplasmic Reticulum Synaptic Vesicles Presynaptic Membrane Synaptic Postsynaptic Cleft Membrane Figure 4.23: Synapse. © bluedoor, LLC. Direction of Neural Impulse Axon Vesicles Containing Neurotransmitter Chemicals Mitochondrion Axonal Terminal Presynaptic Membrane Membrane of Postsynaptic Synaptic Cleft Neuron Figure 4.24: Synapse structure. © bluedoor, LLC. Chapter 4: Central Nervous System and Sensory Organs 89 Sympathetic Ganglia and Neurotransmitters Lateral Horn Sympathetic Preganglionic Neurons Sympathetic Postganglionic Neuron Thoracic Spinal Cord Head, Thoracic, Skeletal and Cutaneous Chain Organs Ganglia Adrenal Celiac and Endocrine Mesenteric Medulla Ganglia Abdominal and Pelvic Sympathetic Organs Postganglionic Neuron Figure 4.25: Sympathetic ganglia. © David G. Ward. Norepinephrine Sympathetic Preganglionic Neuron Lateral Horn Adrenergic Alpha / Beta Receptors Acetylcholine Enlargement Enlargement Sympathetic Ganglion Target Organ Cholinergic Nicotinic-N Sympathetic Receptors Postganglionic Neuron Figure 4.26: Sympathetic neurotransmitters. © David G. Ward. 90 Chapter 4: Central Nervous System and Sensory Organs Nerves Cervical Thoracic Lumbar Sacral L5 L4 T1,2 C8 C7 C6 S1 L7 L6 Figure 4.27: Spinal nerves. © NCSU. Cranial Cervical a. Thoracic Sacral Lumbar b. Thoracic Cervical Figure 4.28: Spinal nerves. © NCSU. Chapter 4: Central Nervous System and Sensory Organs 91 Nerves a. Olfactory Bulb Optic Nerve Oculomotor Nerve Trochlear Nerve Trigeminal Nerve Abducens Nerve Facial Nerve Vestibulocochlear Nerve Glossopharyngeal Vagus Nerve Nerve Spinal Accessory b. Nerve Hypoglossal Nerve Infraorbital c. Maxillary Facial Caudal Mental Middle Mental d. Buccal Mandibular Gland Facial Branches of External Lingual Nerve Facial Nerve Carotid Nerve Maxillary Nerve Vein Figure 4.29: Cranial nerves. © NCSU. Lingual Nerve Deep Facial Jugular Lingual Nerve Vein Nerve Parotid Gland Common Carotid External Carotid Artery Artery 92 Chapter 4: Central Nervous System and Sensory Organs Nerves of the Thoracic Limb Brachial Plexus Median Nerve Axillary Nerve Ulnar Nerve Radial Nerve Musculocutaneous Nerve Figure 4.30: Nerves of the thoracic limb, lateral view. © NCSU. Chapter 4: Central Nervous System and Sensory Organs 93 Nerves of Thoracic Limb Figure 4.31: Ulnar nerve. Figure 4.32: Musculocutaneous nerve. Figure 4.33: Radial nerve. © NCSU. © NCSU. © NCSU. Figure 4.34: Axillary nerve. Figure 4.35: Median nerve. © NCSU. © NCSU. 94 Chapter 4: Central Nervous System and Sensory Organs Nerves of the Lumbosacral Plexus Lumbosacral plexus Femoral Nerve Sciatic Nerve Saphenous Nerve Peroneal Nerve Tibial Nerve Figure 4.36: Nerves of lumbosacral plexes, lateral view. © NCSU. Chapter 4: Central Nervous System and Sensory Organs 95 Nerves of the Lumbosacral Plexus Figure 4.37: Tibial nerve. Figure 4.39: Peroneal (fibular) nerve. © NCSU. © NCSU. Figure 4.38: Femoral nerve. © NCSU. Figure 4.40: Saphenous nerve. Figure 4.41: Sciatic nerve. © NCSU. © NCSU. 96 Chapter 4: Central Nervous System and Sensory Organs Dermatomes and Stretch Reflex C2 T2 T8 T5 T11 C3 L1 C4 T9 T3 C6 T12 T6 L2 C5 L3/L4 T10 T4 T13 T7 S1 L5 S2 L7 L5 L4 T1 L7 L6 C7 L8 C8 C7 Figure 4.42: Dermatomes. © NCSU. Sensory Neuron (detects muscle stretch) Anterior Horn Alpha Muscle Motor Spindle Neuron (contracts muscle) Motor Unit Figure 4.43: Spinal stretch reflex. © David G. Ward. Chapter 4: Central Nervous System and Sensory Organs 97 Sensory Organs: Ear Pinna Semicircular Canals Pinna and Temporlis Muscle 3 6 3 Figure 4.44: Inner ear model. © NCSU. 4 Vertical Ear 5 Canal 6 Pinna and Temporlis Muscle Horizontal Ear Canal Figure 4.45: Heathly ear model. © NCSU. Pinna Tympanic Membrane Ossicles Cochlea Eustachian Tube Figure 4.46: Diseased ear model. © NCSU. 98 Chapter 4: Central Nervous System and Sensory Organs Cochlea Vestibular Duct Vestibular Membrane Tectorial Cochlear Duct Membrane Organ of Corti Basilar Membrane Tympanic Duct Figure 4.47: Cochlea. © David G. Ward. Vestibular Duct Tectorial Membrane Vestibular Membrane Cochlear Duct Basilar Organ of Corti Membrane Tympanic Duct Cochlear Nerve Figure 4.48: Cochlea. © David G. Ward. Chapter 4: Central Nervous System and Sensory Organs 99 Cochlea and Vestibular Apparatus Vestibular Cochlear Duct Membrane (Filled with Endolymph) Tectorial Membrane Stereocilia Basilar Membrane Inner Hair Cell Organ of Rods of Corti Corti Outer Hair Cells Figure 4.49: Organ of corti. © David G. Ward. Lateral Semicircular Canal Superior Semicircular Canal Utricle and Saccule Vestibular Ganglion Vestibular Nerve © David G. Ward © David Cochlear nerve Posterior Semicircular Canal Ampulla of Posterior Semicircular Canal Figure 4.50: Vestibular apparatus and cochlea, posterior view. © David G. Ward. 100 Chapter 4: Central Nervous System and Sensory Organs Sensory Organs: Eye Sclera Ciliary Body Choroid Suspensory Ligaments Retina Iris Fovea Cornea Optic Nerve Pupil Aqueous Humor Optic Disk Lens Vitreous Humor Figure 4.51: Eye, midsagittal. © David G. Ward. Upper eyelid Cornea Pupil Third Eyelid Lower Eyelid Third Eyelid Iris Iris Lens Superior Rectus Muscle Medial Rectus Muscle Lens Vitreous Humor Cornea Lateral Rectus Left
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  • Nerve Cell Impulses

    Nerve Cell Impulses

    • Localization of Certain Neurons Neurotransmitters Nerve Conduction by: Mary V. Andrianopoulos, Ph.D Clarification: Types of Neuron • There may be none, one, or many dendrites composing part of a neuron. • No dendrite = a unipolar neuron • One dendrite = bipolar neuron • More than one dendrite = multipolar neuron. Multipolar neuron Bipolar neuron Unipolar neuron Localization of Neuron types • Unipolar: – found in most of body's sensory neurons – dendrites are the exposed branches connected to receptors – axon carries the action potential in to the CNS – Examples: posterior root ganglia + cranial nerves – Usually: have peripheral + central connections Localization of Neuron types • Bipolar: – retina, sensory cochlear, vestibular ganglion • Multipolar: (fibers) brain + spinal cord – found as motor neurons and interneurons – neuronal tractsÆ CNS – peripheral nervesÆ PNS Size of Neurons + their localization • Golgi I: – Fiber tracts: brain + spinal cord (PNS + motor) – (i.e., Pyramidal tract + Purkinje cells) • Golgi II: – Cerebral + cerebellar cortex – Often inhibitory – Out number Golgi I – Star-shaped appearance 2° short dendrites Histology of the Nervous System A review of Cell types 1) Neurons - the functional cells of the nervous system 2) Neuroglia (glial cells) - Long described as supporting cells of the nervous system, there is also a functional interdependence of neuroglial cells and neurons a) astrocytes - anchor neurons to blood vessels, regulate the micro-environment of neurons, and regulate transport of nutrients and wastes to and from neurons b) microglia- are phagocytic to defend against pathogens and monitor the condition of neurons c) ependymal - line the fluid-filled cavities of the brain and spinal column and play a role in production, transport, and circulation of the CSF.