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Divisions of the Nervous System • Central Nervous Nervous Tissue Lab BIO 137 Anatomy and Physiology I Mary Catherine Flath, Ph.D. System • brain • spinal cord • Peripheral Nervous System • peripheral nerves • cranial nerves • spinal nerves Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Functions of Nervous System Sensory Function (PNS) • sensory receptors gather information (are stimulated) • information is carried as sensory Motor Function (PNS) • decisions are acted impulse on sensory neurons to the upon CNS • motor impulses are Integrative Function (CNS) carried on motor • sensory information is neurons to effectors integrated. (i.e. used to create (responsive body parts) • sensations • memory • thoughts • decisions) Copyright 2016 Dr. Mary Cat Flath 10-6 Divisions of the Nervous System 10-1 Divisions of Peripheral Nervous System Sensory Division • picks up sensory information and delivers it to the CNS Motor Division • carries information from CNS to effectors: •muscles and glands Divisions of the Motor Division Somatic – carries information to skeletal muscle Autonomic – carries information to smooth muscle, cardiac muscle, and glands Copyright 2016 Dr. Mary Cat Flath 10-4 Divisions of the Nervous System CENTRAL NERVOUS SYSTEM (Brain and Spinal Cord; Interneurons) PERIPHERAL NERVOUS SYSTEM (Cranial and Spinal Nerves SENSORY/AFFERENT NEURONS (INPUT) MOTOR/EFFERENT NEURONS (OUTPUT) SOMATIC (Effectors: skeletal muscle) AUTONOMIC (Effectors: smooth muscle, cardiac muscle, glands) PARASYMPATHETIC (maintains homeostasis; acetylcholine) SYMPATHETIC (Fight or Flight; norepinephrine) Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 1 Nervous Tissue Nervous Tissue Neurons with multiple extensions surrounded by neuroglial cells. Locations: Brain and spinal cord (CNS) Nerves (PNS) Function: Sensory, Integration, and motor No reproduction of cells. Nervous Tissue is composed of • neurons • neuroglial cells Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 10-2 Neuron Structure Neuron Structure Copyright 2016 Dr. Mary Cat Flath 10-7 Copyright 2016 Dr. Mary Cat Flath Transmission of a Nerve Impulse within a Neuron (Electrical Impulse) Neuron Structure SEM Copyright 2016 Dr. Mary Cat Flath Starts on a Dendrite Continues through the Cell Body Continues down the Axon And finally into Axonal terminals/Synaptic Knobs Copyright 2016 Dr. Mary Cat Flath 2 NERVOUS TISSUE ~HP NEUROGLIAL CELLS LIGHT MICROGRAPHS OF NERVOUS TISSUE SLIDE IS LABELED “GIANT MULTIPOLAR NEURONS” CELL BODY OF NEURON Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath TEM OF AXONS (CROSS-SECTION) Myelination of Axons PNS: Schwann cells (neuroglial cells in PNS) myelinate axons TEM CNS: Oligodendrocytes (neuroglial cells in CNS) myelinate axons Copyright 2016 Dr. Mary Cat Flath 10-8 Copyright 2016 Dr. Mary Cat Flath Neuroglial Cells Types of Neuroglial Cells Schwann Cells • PNS • myelinating cell Oligodendrocytes • CNS • myelinating cell Microglia • CNS • phagocytic cell Astrocytes • CNS • support and nourish neurons Ependyma • CNS • ciliated • line central canal of spinal cord and ventricles of brain Copyright 2016 Dr. Mary Cat Flath 10-11 Copyright 2016 Dr. Mary Cat Flath 3 Functional Classification of Neurons Sensory Neurons • afferent neurons • carry impulses from sensory receptors to CNS Interneurons • link neurons • multipolar • in CNS Motor Neurons • multipolar • efferent • carry impulses away from CNS to effectors Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 10-10 Structural Classification of Neurons (we will consider all as multipolar) Bipolar • two processes • eyes, ears, nose Unipolar • one process • ganglia MULTIPOLAR • many processes • most neurons of CNS Copyright 2016 Dr. Mary Cat Flath 10-9 Copyright 2016 Dr. Mary Cat Flath Divisions of the Nervous System Nervous Tissue (continued) Copyright 2016 Dr. Mary Cat Flath CENTRAL NERVOUS SYSTEM (Brain and Spinal Cord; Interneurons) PERIPHERAL NERVOUS SYSTEM (Cranial and Spinal Nerves SENSORY/AFFERENT NEURONS (INPUT) MOTOR/EFFERENT NEURONS (OUTPUT) SOMATIC (Effectors: skeletal muscle) AUTONOMIC (Effectors: smooth muscle, cardiac muscle, glands) PARASYMPATHETIC (maintains homeostasis; acetylcholine) SYMPATHETIC (Fight or Flight; norepinephrine) Copyright 2016 Dr. Mary Cat Flath 4 Peripheral Nervous System • Definition of a nerve: A bundle of myelinated axons in the PNS A NERVE IS A BUNDLE OF MYELINATED AXONS IN THE PNS •Cranial nerves arise from the brain • 12 pairs • Spinal nerves arise from the spinal cord • 31 pairs • All mixed 11-42 Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Structure of a Peripheral Nerve 11-43 Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Peripheral Nerve (Medullated nerve) Your peripheral nerve slide shows both a longitudinal section (ls) & cross section (cs) The slide is labeled “medullated nerve”. Copyright 2016 Dr. Mary Cat Flath Longitudinal Section You can see myelinated axons and Nodes of Ranvier Cross-Section You can see connective tissue coverings Copyright 2016 Dr. Mary Cat Flath 5 Longitudinal Section of a Peripheral Nerve (LM) SEM Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Divisions of the Nervous System Your third slide in Nervous Tissue is a “motor unit.” The slide is labeled “Motor Nerve Endings.” (You saw this slide when you studied the muscular system). Copyright 2016 Dr. Mary Cat Flath STIMULATION OF SKELETAL MUSCLE FIBERS CENTRAL NERVOUS SYSTEM (Brain and Spinal Cord; Interneurons) PERIPHERAL NERVOUS SYSTEM (Cranial and Spinal Nerves SENSORY/AFFERENT NEURONS (INPUT) MOTOR/EFFERENT NEURONS (OUTPUT) SOMATIC (Effectors: skeletal muscle) AUTONOMIC (Effectors: smooth muscle, cardiac muscle, glands) PARASYMPATHETIC (maintains homeostasis; acetylcholine) SYMPATHETIC (Fight or Flight; norepinephrine) Copyright 2016 Dr. Mary Cat Flath Neuromuscular Junction EACH SKELETAL MUSCLE FIBER IS STIMULATED TO CONTRACT BY A BRANCH OF A MOTOR NEURON A MOTOR UNIT IS DEFINED AS ONE MOTOR NEURON MANY SKELETAL MUSCLE FIBERS A NEUROMUSCULAR JUNCTION IS WHERE THE MOTOR NERVE ENDING MEETS THE SARCOLEMMA OF THE SKELTAL MUSCLE FIBER Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 6 MOTOR NERVE ENDINGS (MOTOR UNIT) ~LOW MUSCLE FIBERS Light Micrographs (LMs) of Motor Units Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath MOTOR NERVE ENDINGS (MOTOR UNIT) ~LOW~ MOTOR NERVE ENDINGS (MOTOR UNIT) ~LOW~ BRANCHING MOTOR NEURON NEUROMUSCULAR JUNCTIONS Copyright 2016 Dr. Mary Cat Flath MOTOR NERVE ENDINGS (MOTOR UNIT) ~HIGH~ Copyright 2016 Dr. Mary Cat Flath Nerve Fiber Classification • Sensory Nerves – conduct sensory impulses into CNS • Motor Nerves – conduct motor impulses from CNS to muscles or glands • Mixed Nerves – contain both sensory nerve fibers and motor nerve fibers; most nerves and all spinal nerves 11-44 Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 7 Divisions of the Nervous System CENTRAL NERVOUS SYSTEM (Brain and Spinal Cord; Interneurons) PERIPHERAL NERVOUS SYSTEM (Cranial and Spinal Nerves SENSORY/AFFERENT NEURONS (INPUT) MOTOR/EFFERENT NEURONS (OUTPUT) SOMATIC (Effectors: skeletal muscle) AUTONOMIC (Effectors: smooth muscle, cardiac muscle, glands) PARASYMPATHETIC (maintains homeostasis; acetylcholine) SYMPATHETIC (Fight or Flight; norepinephrine) Cranial Nerves (studied later) 11-46 Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Spinal Nerves (studied later) • mixed nerves • 31 pairs • 8 cervical (C1 to C8) • 12 thoracic (T1 to T12) • 5 lumbar (L1 to L5) • 5 sacral (S1 to S5) • 1 coccygeal (Co) See how you do identifying the following structures. 11-54 Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Neuron Structure Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 10-7 8 Motor neuron Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Longitudinal Section of a Peripheral Nerve (LM) Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath MOTOR NERVE ENDINGS (MOTOR UNIT) ~LM; LOW~ BRANCHING MOTOR NEURON Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 9 Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Good luck studying!!! Copyright 2016 Dr. Mary Cat Flath 10