University:
Texas A&M University
Course:
BIOL 319 | Integrated Human Anatomy and Physiology I
Academic year:

2024
Views:

488

Pages:

74
Author:

Hundebuchesn

Peripheral Nervous System Four Basic Types of Tissues in the Body ----------------------------------------------Epithelium (90% of tumors) Muscular Tissue Connective Tissue Nervous Tissue Objectives Overview of the central and characteristics of the peripheral nervous system Characteristics of neurons and support cells Organization of peripheral nerves Nerve is like Epithelium Origin of nerve is ectoderm like epidermis (epithelium) of skin Nervous Tissue Functions: specialized for the transmission, reception, and integration of electrical impulses Distinguishing features: Neurons – very large excitable cells with long processes called axons and dendrites. The axons make contact with other neurons or muscle cells at a specialization called a synapse where the impulses are either electrically or chemically transmitted to other neurons or various target cells (e.g., muscle). Others secrete hormones. Nervous tissue Glial cells – the supporting cells of nervous tissue. Nerves – collections of neuronal processes bound together by connective tissue. Axons may be coated by a myelin sheath (“myelinated”) or simply protected by being cradled in an indentation of a glial cell (“unmyelinated”). Nervous tissue Distribution: comprise the central nervous system. Individual peripheral nerves are found throughout the body. Individual neurons and clusters of neurons (called ganglia) are found in most organs. Function of the Nervous System is Communication Dependent upon special signaling properties of neurons Long processes of neurons (e.g., 1 meter motor neuraxon) Function of the Nervous System is Communication Characteristics of neurons Irritability - protoplasm capable to react to various physical and chemical agents Conductivity - ability to transmit the resulting excitation from one locality to another Types of Nerves The Nervous System Central nervous system (CNS) – Brain and spinal cord – Neurons and support neuroglia The Nervous System Peripheral nervous system (PNS) All nervous tissue (neurons, support cells, and axons) outside the brain and spinal cord Activity of the Nervous System Information • Receive: receptors afferent pathway • Process: CNS (centralization is paramount) • Transmit: efferent pathways  effect Voluntary (conscious ) = somatic Involuntary = autonomic • Sympathetic - fight or flight • Parasympathetic - vegetative Cells and Functions of the Nervous System CNS PNS Function astrocytes (BBB) satellite cells ion exchange oligodendrocytes Schwann cells myelin production microglia --- phagocytosis Astrocytes Microglia Oligodendrocytes Schwann cells - Myelin Cells of the Nervous System Neuronal Structure / Function Structure • • • • Perikaryon (soma, cell body) Axon hillock - site of beginning of axon Dendrites - reception Axon (nerve) - transmission Neuronal Structure / Function Neuronal Structure / Function Neuronal Structure / Function NEURONAL STRUCTURE / FUNCTION Axonal transport Anterograde - toward terminal - kinesin Retrograde - toward cell body - dynein • Tetanus toxin • Neurotropic viruses (herpes and rabies) use path to get to cell body in CNS Neuronal Structure / Function Neuronal Structure/Function Function of Myelin Increase speed of condition – 1 meter/sec TO 120 meters/sec High-resistance low capacitance – Insulator Protection of axon Possible nutritional role Direct regenerating axons Schwann Cell Structure / Function Most peripheral nerves are myelinated 1 Schwann cell/1 axon for location Formation of myelin sheath • Nodes of Ranvier • Schmidt-Lantermann clefts • Neurokeratin network Schwann Cell Structure / Function Node of Ranvier Node of Ranvier Myelination and Schwann Cells Organization of Peripheral Nerves Ganglia - collections of nerve cell bodies Smooth muscle Smooth muscle Remember Connective Tissue Layers of Skeletal Muscle Epimysium, Perimysium, and Endomysium Organization of Peripheral Nerves Nerve fibers - axons invested by connective tissue Epineurum - surrounding entire nerve Perineurum - surrounding fascicles – constitutes the PNS blood barrier via tight junctions between fibroblasts Endoneurum - between individual nerve axons Organization of Peripheral Nerves PERINEURUM Organization of Peripheral Nerves PERINEURUM Autonomic Nervous System Sympathetic - Fight or Flight Parasympathetic - Vegetative Nerve Endings – Synapses (Efferent Pathways) Types – Electrical: gap junctions, slow ion exchange between cells, not common in mammals – Chemical: rapid plus or negative response Characteristics – Synaptic vesicles (neurotransmitters) – Synaptic cleft Motor End Plate Nerve Endings - Synapses Motor End Plate Nerve Endings – Synapses Pathways) (Efferent Nerve Endings – Synapses Nerve Endings - Synapses Nerve Endings - Synapses Nerve Endings - Synapses Neuroactive Substance Neurotransmitters - Acetylcholine Neuromodulators - Receptor Coupled and Second Messenger Neurohormone - Serotonin, GABA slow but widespread effect Innervation of Muscle Neurotransmitter Vesicles Physiological Events at the Synapse Arrival of Action Potential Opening of Voltage-Gated ion channels for Ca++ to enter terminal Influx of Ca++ Physiological Events at the Synapse Influx of Ca++ triggers exocytosis of neurotransmitters from docked vesicles Transmitter diffuses across synaptic cleft Physiological Events at the Synapse Transmitter binds to receptors on postsynaptic membrane Receptor binding causes ion channels to open to Na+ and causes depolarization Physiological Events at the Synapse Depolarization (equal Na+ inside and outside) Depolarization – Stimulation Hyperpolarization – Inhibition Removal of transmitter Summary of the Physiological Events at the Synapse • Arrival of action potential at axon terminal • Opening Ca++ channels • Influx of Ca++ into axon terminal • Exocytosis of neurotransmitter • Diffusion of neurotransmitter across synaptic cleft • Binding of neurotransmitter to receptors on target cell • Opening of Na+ channels causing depolarization of target cell • Removal of neurotransmitter Vesicle Membrane is Recycled Cycling of the Membrane Cycling of the Membrane Cycling of the Membrane Nerve Endings - Synapses Types of Synapses Anodendritic Synapses  http://www.youtube.com/watch?v=70DyJ wwFnkU&NR=1 Nerve Endings - Receptors Receptors (Afferent Pathways) • Neuromuscular Spindles • Pacinian Corpuscles • Meissner’s Corpuscles Nerve Endings - Receptors Receptors (Afferent Pathways) Neuromuscular Spindles Nerve Endings - Receptors Pacinian Corpuscles Nerve Endings - Receptors Meissner’s Corpuscles Nerve Endings - Receptors Meissner’s Corpuscles and other important corpuscles Inner Ear OLFACTORY Summary Nerve Endings - Receptors Nerve Endings - Synapses (Efferent Pathways) Summary Regeneration of Axons

Peripheral Nervous System

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