Peripheral Nervous System & Autonomic Nervous System PDF

Vet Prep Structural and Functional Biology Peripheral Nervous System and Autonomic Nervous System Dr. Melissa Kehl Courtesy of Dr. Terri Clark Student Objectives • Describe the components of the PNS including nerves, cell types, their morphology, ganglia, function and their location. • Describe...

Vet Prep Structural and Functional Biology Peripheral Nervous System and Autonomic Nervous System Dr. Melissa Kehl Courtesy of Dr. Terri Clark Student Objectives • Describe the components of the PNS including nerves, cell types, their morphology, ganglia, function and their location. • Describe the parts of a spinal nerve. • Describe a nerve plexus and its purpose, using phrenic nerve example. • Distinguish between sensory and motor, voluntary and involuntary. • Describe myelin and cells that make it. • Differentiate between white and grey matter. • Distinguish between autonomic and somatic motor circuit, locations of cell bodies. • Describe the outflows of both PsNS and SNS and how targets are innervated by them. • Describe how autonomics control the heart and the nerves involved. PNS (Peripheral Nervous System) All nerves outside brain and spinal cord Starting branches are cranial nerves and spinal nerves CNS (Central Nervous System) brain and spinal cord Motor (Efferent) from the CNS Visceral Efferent - Autonomic Nervous System ANS Involuntary Smooth and Cardiac muscles, Glands 1 cell body in the gray matter of CNS 1 cell body in a ganglion 2 neurons Parasympathetic Rest and digest /homeostasis Sympathetic Fight or flight Somatic Efferent Voluntary Striated/skeletal muscles Cell body in the gray matter of CNS 1 neuron Sensory (Afferent) to the CNS Visceral Afferent Somatic Afferent PNS - Peripheral Nervous System Includes ALL nerves, ganglia, plexi outside of the CNS Nerves in body are called spinal nerves 8 cervical nerves 13 thoracic 7 lumbar 3 sacral 5 caudal (coccygeal) Nerves in head called cranial nerves (I-XII) Cells of Peripheral Nervous System • • • • Neurons = nerve cells Sensory (afferent) division transmit impulses toward the CNS. Motor (efferent) division transmits impulses toward organs, muscles and glands. Support cells pack around neurons, • Schwann cells make myelin (lipid) Spinal Cord Anatomy • Shortly after a spinal nerve exits the intervertebral foramen, it branches into the dorsal ramus, the ventral ramus, and the ramus communicans. Rami • Each of these three structures carries both sensory and motor information. Dorsal Root Gangion • The dorsal ramus is the dorsal branch of a spinal nerve and carries information to and from epaxial structures. • The ventral ramus is the ventral branch of a spinal nerve and carries information to and from the rest of the body. Communicating Ramus Blue = sensory Red = motor Axial Muscles Axial muscles are the muscles of the trunk and neck • Epaxial muscles • Lie dorsal to the transverse processes of the vertebrae • Extensors of the vertebral column • Hypaxial muscles • All other neck and trunk muscles – located ventral to the transverse processes of the vertebrae • Flexors of the vertebral column The blue line is the • Includes thoracic and abdominal wall muscles approximate location of the vertebral column Epaxial muscles Hypaxial muscles Textbook of Veterinary Anatomy, 4th ed.; Dyce, Sack, Wensing; Fig. 2.23 B Note that the limb muscles are not included – they are not axial muscles Nerve Plexi and Phrenic Nerve • A nerve plexus is a network of intersecting nerves. • It ensures that all part of the body are innervated. • They combine sets of ventral rami of spinal nerves that serve the same area of the body. • Root values of the phrenic nerve are C5, C6, and C7. Myelin • • • • • Fatty layer laid down around some axons Never found around cell body Looks white (makes ‘white matter’) Insulates axon electrically and increases conduction speed Not all nerve fibers are myelinated = unmyelinated fibers Schwann Cell Grey and White Matter • Grey matter is nervous tissue without myelin • Includes nerve cell bodies and unmyelinated nerve fibres • White matter is nervous tissue covered by myelin Spinal Cord Brain PNS (Peripheral Nervous System) All nerves outside brain and spinal cord Starting branches are cranial nerves and spinal nerves CNS (Central Nervous System) brain and spinal cord Motor (Efferent) from the CNS Visceral Efferent - Autonomic Nervous System Involuntary Smooth and Cardiac muscles, Glands 1 cell body in the gray matter of CNS 1 cell body in a ganglion 2 neurons Parasympathetic Rest and digest /homeostasis Sympathetic Fight or flight Somatic Efferent Voluntary Striated/skeletal muscles Cell body in the gray matter of CNS 1 neuron Sensory (Afferent) to the CNS Visceral Afferent Somatic Afferent Sensory Subdivision of PNS Dorsal Root Ganglion is always 100% sensory – may contain visceral and somatic afferent cell bodies Sensory from skin/body wall (somatic afferent) Sensory from organs (visceral afferent) PNS (Peripheral Nervous System) All nerves outside brain and spinal cord Starting branches are cranial nerves and spinal nerves CNS (Central Nervous System) brain and spinal cord Motor (Efferent) from the CNS Visceral Efferent - Autonomic Nervous System Involuntary Smooth and Cardiac muscles, Glands 1 cell body in the gray matter of CNS 1 cell body in a ganglion 2 neurons Parasympathetic Rest and digest /homeostasis Sympathetic Fight or flight Somatic Efferent Voluntary Striated/skeletal muscles Cell body in the gray matter of CNS 1 neuron Sensory (Afferent) to the CNS Visceral Afferent Somatic Afferent Motor Subdivision of PNS Autonomic/Visceral Innervates involuntary tissues = smooth muscle, cardiac muscle, glands Visceral efferent output takes 2 neurons Somatic Innervates voluntary tissues = skeletal muscle Somatic efferent output takes 1 neuron PNS (Peripheral Nervous System) All nerves outside brain and spinal cord Starting branches are cranial nerves and spinal nerves CNS (Central Nervous System) brain and spinal cord Motor (Efferent) from the CNS Visceral Efferent - Autonomic Nervous System Involuntary Smooth and Cardiac muscles, Glands 1 cell body in the gray matter of CNS 1 cell body in a ganglion 2 neurons Parasympathetic Rest and digest /homeostasis Sympathetic Fight or flight Somatic Efferent Voluntary Striated/skeletal muscles Cell body in the gray matter of CNS 1 neuron Sensory (Afferent) to the CNS Visceral Afferent Somatic Afferent Autonomic Nervous System (ANS) Visceral Efferent • Is part of the nervous system dealing with ‘automatic’ control of body functions (eg. gut movement, breathing etc) • Not generally under conscious control • Innervates smooth muscles, cardiac muscles and glands • Has at least 2 neurons • Has two divisions (sympathetic and parasympathetic) Autonomic Nervous System - ANS Two Neuron System 1. Preganglionic/Presynaptic neuron • Cell body is inside the CNS • Axon exits the CNS; synapses onto a second autonomic neuron in a ganglion 2. Postganglionic/Post-synaptic neuron • Cell body is inside an autonomic ganglion • Axon targets smooth muscle, cardiac muscle, or glands Autonomic Nervous System - ANS PNS (Peripheral Nervous System) All nerves outside brain and spinal cord Starting branches are cranial nerves and spinal nerves CNS (Central Nervous System) brain and spinal cord Motor (Efferent) from the CNS Visceral Efferent - Autonomic Nervous System Involuntary Smooth and Cardiac muscles, Glands 1 cell body in the gray matter of CNS 1 cell body in a ganglion 2 neurons Parasympathetic Rest and digest /homeostasis Sympathetic Fight or flight Somatic Efferent Voluntary Striated/skeletal muscles Cell body in the gray matter of CNS 1 neuron Sensory (Afferent) to the CNS Visceral Afferent Somatic Afferent Sympathetic Nervous System (SNS) • Fight or flight • Pre-ganglionic neurons Nerve cell bodies are in the thoracolumbar region of the spinal cord • Post-ganglionic neurons Nerve cell bodies are in identifiable cervical, thoracic or abdominal ganglia separate from the target organ • Often referred to as the thoracolumbar system Sympathetic Nervous System A preganglionic sympathetic axon may synapse on a postganglionic cell body in a remote ganglion, not necessarily in the closest one. Sympathetic Trunk/Chain Ganglia Sympathetic trunk Located on either side of the vertebral column Cervicothoracic ganglion Vagosympathetic trunk Middle cervical ganglion Left thoracic cavity Sympathetic Chain Ganglia Thoracic cavity Sympathetic trunk/chain– blue arrows PNS (Peripheral Nervous System) All nerves outside brain and spinal cord Starting branches are cranial nerves and spinal nerves CNS (Central Nervous System) brain and spinal cord Motor (Efferent) from the CNS Visceral Efferent - Autonomic Nervous System Involuntary Smooth and Cardiac muscles, Glands 1 cell body in the gray matter of CNS 1 cell body in a ganglion 2 neurons Parasympathetic Rest and digest /homeostasis Sympathetic Fight or flight Somatic Efferent Voluntary Striated/skeletal muscles Cell body in the gray matter of CNS 1 neuron Sensory (Afferent) to the CNS Visceral Afferent Somatic Afferent Parasympathetic Nervous System (PsNS) • Rest and digest – homeostasis • Pre-ganglionic neurons Nerve cell bodies are in the brainstem and sacral region of the spinal cord Nerve fibers are in Cranial Nerves III, VII, IX, X and sacral spinal nerves • Post-ganglionic neurons Nerve cell bodies are in the terminal ganglia on the structures innervated (not visible) • Often referred to as the craniosacral system S1 S2 S3 Parasympathetic Nervous System preganglionic fibers postganglionic fibers Notice the post-ganglionic nerve cell body at the organ of innervation. Parasympathetic Nervous System – Vagus Nerve diaphragm Left vagus nerve Vagosympathetic trunk Left thoracic cavity Autonomic Control of Heart Sympathetic innervation via cardiac nerves speeds up heart and constricts blood vessels Parasympathetic innervation via vagus nerves slows heart See you ALL in GA1!