Human Biology Sylvia S. Mader Michael Windelspecht Chapter 13 Nervous System Lecture Outline Part 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Nervous System See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes 2

Points to ponder What are the 3 types of neurons? What are neuroglia? What is the structure of a neuron? What is the myelin sheath? Saltatory conduction? Schwann cell? Node of Ranvier? Explain the resting and action potential as they relate to a nerve impulse. How does the nerve impulse traverse the synapse? What are the 2 parts of the nervous system? What 3 things protect the CNS? What are the 4 parts of the brain and their functions? What is the reticular activating system and the limbic system? What are some higher mental functions of the brain? What are the 2 parts of the peripheral nervous system? How do abused drugs work?

The nervous divisions 2 divisions 13.1 Overview of the Nervous System The nervous divisions 2 divisions __________________ (CNS): Brain and spinal cord __________________ (PNS): Nerves and ganglia (collections of cell bodies)

The nervous divisions 13.1 Overview of the Nervous System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. brain Central Nervous System (CNS) cranial nerves brain spinal cord spinal cord spinal nerves Peripheral Nervous System (PNS) sensory (afferent) nerves — carry sensory information into brain and spinal cord motor (efferent) nerves — carry motor information from CNS to effectors somatic sensory nerves: signals from skin, muscles, joints, special senses somatic motor nerves: signals to skeletal muscles, voluntary autonomic motor nerves: signals to smooth muscle, cardiac muscle, glands, involuntary visceral sensory nerves: signals from body organs sympathetic division “fight or flight” parasympathetic division “rest and digest” a. b. Figure 13.1 The two divisions of the nervous system.

13.1 Overview of the Nervous System The nervous system allows for _____________ between cells through sensory input, integration of data, and motor output. 2 cell types: _______ and ________

Expanding on neurons 3 types of neurons 13.1 Overview of the Nervous System Expanding on neurons 3 types of neurons _________ – takes impulses from sensory receptor to CNS _________ – receives information in the CNS and sends it to a motor neuron ______ – takes impulses from the CNS to an effector (i.e., gland or muscle fiber)

Expanding on neurons Neuron structure (Ch. 4 review) 13.1 Overview of the Nervous System Expanding on neurons Neuron structure (Ch. 4 review) Cell body – main cell where nucleus and most organelles reside Dendrites – many short extensions that carry impulses to a cell body Axon (nerve fiber) – single, long extension that carries impulses away from the cell body

Types of neurons 13.1 Overview of the Nervous System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Sensory neuron sensory receptor cell body axon myelin sheath direction of conduction Schwann cell b. Interneuron 400 nm axon dendrite c. Motor neuron cell body axon node of Ranvier 2.7 μm Figure 13.2 The structure of sensory neurons, interneurons, and motor neurons. axon terminal direction of conduction a (myelin): © M.B. Bunge/Biological Photo Service; c (cell body): © Manfred Kage/Peter Arnold/Photolibrary

13.1 Overview of the Nervous System The myelin sheath A lipid covering on long axons that acts to increase the speed of nerve impulse conduction, insulation, and regeneration in the PNS _____________ – neuroglia that make up the myelin sheath in the PNS _____________ – gaps between myelination on the axons Saltatory conduction – conduction of the nerve impulse from node to node

Neuron structure 13.1 Overview of the Nervous System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Sensory neuron sensory receptor cell body axon myelin sheath direction of conduction Schwann cell b. Interneuron 400 nm axon dendrite c. Motor neuron cell body axon node of Ranvier 2.7 μm Figure 13.2 The structure of sensory neurons, interneurons, and motor neurons. axon terminal direction of conduction a (myelin): © M.B. Bunge/Biological Photo Service; c cell body): © Manfred Kage/Peter Arnold/Photolibrary

The nerve impulse: Resting potential (RP) 13.1 Overview of the Nervous System The nerve impulse: Resting potential (RP) ___________________ – when the axon is not conducting a nerve impulse More positive ions outside than inside the membrane Negative charge of -70 mV inside the axon More Na+ outside than inside More K+ inside than outside

The nerve impulse: Resting potential (RP) 13.1 Overview of the Nervous System The nerve impulse: Resting potential (RP) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. recording electrode inside axon reference electrode outside axon + + + + + + + + + +           axonal membrane           + + + + + + + + + + inside axon K+ Na+ gated K+ channel gated Na+ channel outside axon a. Resting potential: Na+ outside the axon, K+ and large anions inside the axon. Separation of charges polarizes the cell and causes the resting potential. Figure 13.3a Generation of an action potential.

The nerve impulse: Action potential 13.1 Overview of the Nervous System The nerve impulse: Action potential ________________ – rapid change in the axon membrane that allows a nerve impulse to occur Sodium gates open, letting Na+ in. Depolarization occurs. Interior of axon loses negative charge (-55 mV, then +35 mV).

The nerve impulse: Action potential 13.1 Overview of the Nervous System The nerve impulse: Action potential Potassium gates open, letting K+ out. _______________ occurs. Interior of axon regains ______________ charge (-70 mV). Wave of depolarization/repolarization travels down the axon. Resting potential is restored by moving potassium inside and sodium outside.