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Anatomy 32 Lecture Chapter 12 - The Nervous System & Nervous Tissue I. Overview A. Divisions & Functions of the Nervous System B. Nervous Tissue C. Nerves D. Nerve Impulses II. Divisions & Functions of the Nervous System A. The __________ system works closely with the ___________ system to maintain bodily homeostasis. 1. The nervous system reacts rapidly via ____________________, and has 3 major functions: a. ___________ input - sensory receptors within and near the body’s surface respond to stimuli and send nerve impulses to the CNS b. ___________ - the CNS receives, processes, and interprets the sensory input, then decides what to do about it c. ___________ output – the CNS sends nerve impulses to effector organs (muscles or glands) in response to the sensory input 1. 2. The endocrine system reacts more slowly via ____________. ______________ is the study of nervous system function and disorders. B. ________________ of the Nervous System 1. _____________ Nervous System (CNS) - consists of _______ & ________________. Most impulses that stimulate muscles to contract and glands to secrete originate in the CNS. 2. _______________ Nervous System (PNS) – outside the CNS; consists of cranial nerves & spinal nerves a. b. c. ____________ nerves – carry signals to & from the ______ __________ nerves – carry signals to & from the _____ cord Cranial & spinal nerves are composed of ___________ and ___________ neurons 1) Sensory (_________) neurons, whose cell bodies end in the CNS, conduct nerve impulses from the _______ to the CNS. 2) Motor (_________) neurons, whose cell bodies originate in the CNS, conduct impulses from the _____ to muscles & glands. 3._______ Subdivisions include the somatic and autonomic nervous systems a. __________ (voluntary) Nervous System (SNS) - consists of 1) ________ neurons that conduct impulses from the ______ and sense receptors to the CNS 2 2) ________ neurons that conduct impulses from the CNS to ____________ ___________ tissue. b. __________ (involuntary) Nervous System (ANS) - contains sensory neurons from visceral ______ and motor neurons that convey impulses from the CNS to ________ muscle, ______ muscle, and __________. ANS is further subdivided into: 1) ____________ ANS – controls “flight or fight” functions 2) _____sympathetic ANS – controls “vegetative” functions III. Nervous ____________: neuroglia & neurons A. ___________ (glia) - Small cells that make up about 50% of the CNS; neuroglia support, nourish, and protect neurons. ________ brain tumors are formed by rapidly dividing glial cells. 1. ______ Neuroglia a. _____________ - star-shaped cells with many processes; functions: 1) Form structural support between _____________ and _______ of the CNS 2) Take up & release ______ to control the neuronal environment 3) Establish the _______________ barrier c. _________ - small, phagocytic cells derived from monocytes; phagocytize pathogens within the CNS d. __________ cells – ciliated columnar epithelial cells that line brain ventricles and spinal cord central canal; they produce and help circulate cerebral spinal fluid (CSF). e. 2. __________________ - most common glial cell, similar to astrocytes but with shorter & fewer processes. Functions: 1) Guide development of _________ in the CNS 2) Produce ______________ (lipid & protein) around CNS neuron axons, which insulates axon, increasing speed of nerve impulse conduction. 3) __________________ involves an autoimmune destruction of the myelin sheath. ______ Neuroglia a. ________ cells (neurolemmocytes) - flattened cells arranged in series around axons or dendrites; produce the __________ sheath around PNS neuron axons 1) ______________ is the outer nucleated cytoplasmic layer of a Schwann cell; helps regenerate damaged myelinated PNS neuron axon or dendrite. 2) _______ of ___________ (neurofibral nodes) are gaps between myelin sheaths on the neuron axon. b. __________ cells (ganglionic gliocytes) - support neurons in ___________ (collection of neuron cell bodies in PNS). 3 B. _________ - nerve cells that conduct nerve impulses at up to 280 mph; lengths range from 1 mm to longest cells in body (from brain to toes). Neurons are long lived, have a high metabolic rate, and do not divide. Neuron ________: 1. 2. Nerve __________ - neuron dendrite or axon 3. 4. 5. ____________ - Group of nerve cell bodies in the PNS. 6. _____ matter - contains nerve cell bodies, dendrites, and axon terminals or bundles of ______________ axons and neuroglia; forms H-shaped inner core of spinal cord and covers cerebrum. _________ - bundle of nerve fibers; most nerves include both sensory and motor fibers. Nucleus (________) - mass of nerve cell bodies and dendrites inside the CNS. __________ - Bundle of myelinated nerve fibers in the CNS. Tracts interconnect brain regions as well as regions in the brain to the spinal cord. 7. _______ matter - aggregation of ____________ neuron processes; surrounds Hshaped inner core of spinal cord. C. Neuron Structure 1. Cell ______ (soma or perikaryon) - contains nucleus, cytoplasm, lysosomes, mitochondria, golgi bodies as well as: a. b. c. ______________ - yellowish-brown lysosome remnants. _________ bodies - neuronal rough ER _______________ - cytoskeletal intermediate filaments that move materials through the neuron. 2. __________ - treelike processes extending from cell body that ___________ impulses from receptors or other neurons and conduct the impulses to the cell body. 3. ________ - process extending from cell body that _________ the nerve impulse from the neuron to the dendrites or cell body of another neuron, or to an ____________ (muscle or gland). a. b. Axon _________ - cone-shaped structure where axon joins cell body. Axon __________ - specialized processes at end of axon collaterals and axons; may end with swollen bumps called synaptic _____________, which contain synaptic vesicles containing ________________, which influence other neuron, muscle, or gland activities. D. Neuron & Nerve Classification - related to _________ (number of cell body processes) and ____________ (sensory/afferent or motor/efferent). 1. _______polar – usually have _______ dendrites and one axon; includes most neurons found in brain & spinal cord; have both ________ & ___________ functions. 2. ____polar - have one main __________ and one _______; rare - found in retina, inner ear, and olfactory area of brain; have mostly ___________ functions. 4 3. _____polar (pseudounipolar) - has ___ process extending from cell body; ________ only. Dendrites located at distal tip of axon; monitors sensory stimuli (touch or pain). 4. ____________ (association neurons) - found only in the CNS; not purely sensory or motor; conduct impulses to other neurons; 90% of all neurons in body. 5. Neuron & nerve classifications according to ____________: 6. a. ________ ____________ afferent receptors in the _____, bones, muscles, joints, eyes, & ears, deliver impulses (pain, temp., touch, vibration, pressure, position, vision, hearing) to the CNS via spinal & some cranial nerves. b. __________ ________ - afferent neurons that send impulses relaying distention and chemical conditions from ________, blood vessels, tongue, & nasal epithelia to CNS via cranial & spinal nerves. c. ________________ - efferent neurons relay impulses from the CNS via motor cranial & spinal nerves and cause the contraction of _________ __________. d. ______________ - efferent neurons (autonomic motor fibers) relay impulses from the CNS via cranial & spinal nerves to smooth & cardiac _________ and ________. A _________ is a collection of neuron fibers held together by loose CT outside the CNS; it consists of the following layers: a. b. c. _______neurium CT sheath surrounds each individual nerve fiber d. Most nerves are composed of both motor & sensory fibers, thus are called _________ nerves Some _____ nerves consist of only sensory or motor neurons 1) Sensory nerves serve the special _________ (taste, smell, sight, hearing) 2) Motor nerves conduct impulses to _________, causing contraction, or glands, causing secretion. e. _______neurium CT surrounds a group of nerve fibers (____________) _____neurium CT surrounds the entire nerve and contains blood vessels & adipose cells IV. Transmission of Nerve Impulses A. Nerve __________ - the exchange of sodium (___) and potassium (___) ions along the length of a nerve fiber, resulting in a stimulus that activates another neuron or tissue (e.g.: muscle or gland) 1. A ___________ nerve fiber has more ____ ions outside than inside, and more ____ ions inside than outside, creating a difference in charge called the __________ _________ across the plasma membrane 2. A strong stimulus received by the neuron opens Na+ ion channels in the membrane, allowing an influx of ___ ions, resulting in _____________ that generates an action potential, which continues the length of the axon 5 3. After depolarization, ________________ occurs as ____ ions are transported out of the neuron via K+ ion channels. 4. The neuron’s resting potential is restored by the __________-_________ pump, which pumps Na+ out and K+ into the neuron B. ___________ - the junction between an _____ terminal and an ____________, such as another neuron, muscle, or gland. 1. The axon terminal contains many synaptic ___________ that contain neuro______________, such as acetylcholine (ACh) 2. When the action potential reaches the axon terminal, it stimulates the release of neurotransmitter into the synaptic ________ between the axon and effector 3. The neurotransmitter stimulates the _________, propagating the impulse and causing a _________, such as muscle contraction or glandular secretion.