Chapter 13 Nervous System (Part 1) PDF

Chapter 13 Nervous System (Part 1) Overview of the Nervous System 1 2 Nervous system function? Allows us to receive, integrate (process), and react to environmental stimuli to maintain homeostasis. Component parts?  Central nervous system (CNS) includ...

Chapter 13 Nervous System (Part 1) Overview of the Nervous System 1 2 Nervous system function? Allows us to receive, integrate (process), and react to environmental stimuli to maintain homeostasis. Component parts?  Central nervous system (CNS) includes the brain and spinal cord  Peripheral nervous system (PNS) Somatic sensory and motor neurons to skeletal muscles (voluntary) Autonomic sensory and motor neurons go to smooth muscles and glands (involuntary) 3 4 Nervous Tissue Nervous Tissue contains two types of cells. Neurons transmit nerve impulses between parts of the nervous system. Neuroglia support, protect, and nourish neurons. (neuroglial cells or glial cells) Have different specific names based on their shape, location, function. 5 6 Neuron Structure Neurons are classified according to function. Sensory neurons take impulses from a sensory receptor to the CNS. (afferent, ‘at’) Interneurons receive input from sensory neurons, and other neurons, and then communicate with motor neurons. (association, connector) Motor neurons take nerve impulse away from the CNS to an effector that carries out responses to environmental change. (efferent, ‘exit’) 7 Types of Neurons 8 Neuron Structure Neurons contain three basic parts. Cell body contains nucleus and other organelles. Dendrites receive signals from sensory receptors or other neurons. Axon conducts nerve impulses away for the cell body. 9 10 Myelin Sheath Some axons are covered by a protective myelin sheath. Formed by Schwann cells containing myelin in plasma membranes. (neurolemmocytes) Nodes of Ranvier are gaps on the axon with no myelin sheath. (neurofibril node) 11 12 Myelin Sheath 13 Neurotransmitter Molecules Among the more than 100 substances known or suspected to be neurotransmitters are acetylcholine (ACh), norepinephrine (NE), dopamine, serotonin, glutamate, and GABA (gamma aminobutyric acid). Neurotransmitters transmit signals between nerves. Nerve– muscle, nerve–organ, and nerve– gland synapses also communicate using neurotransmitters.  Acetylcholine and norepinephrine are active in both the CNS and PNS. In the PNS, these neurotransmitters act at synapses called neuromuscular junctions. 14 The Central Nervous System The central nervous system (CNS) is made up of the spinal cord and the brain. Both are wrapped in protective membranes, meninges, with spaces between meninges filled with cerebrospinal fluid which also fills 4 cavities in the brain (called ventricles) and act as reservoirs. CNS is composed of two types of nervous tissue. Gray matter – Short, nonmyelinated fibers. White matter - Myelinated axons. 15 16 17 18 The Spinal Cord The spinal cord extends from the base of the brain through the foramen magnum into the vertebral canal. Components: Central canal – filled with cerebrospinal fluid Grey matter – “butterfly shaped” White matter – contains interneurons grouped in tracts (ascending and descending) which cross over so that left side of brain controls right side of body. 19 20 Functions of the Spinal Cord The spinal cord 1. Provides a means of communication between the brain and the peripheral nerves that leave the cord 2. Is a center for reflex actions. 21 22