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Chapter 7: The Nervous System Functions of the Nervous System 1. __________________________________________ Monitor changes occurring _________________________ and ______________________ the body 2. __________________________________________ Processes and interprets sensory input and decide what to be done Mainly occurs in brain and spinal cord 3. __________________________________________ A response to integrated stimuli by activating effector organs – muscles and glands Organization of the Nervous System Classified based on structure and function Structure ______________________ ____________________ __________________________ Function Sensory: __________________________________________ Motor: __________________________________________ ___________________________ Classification of the Nervous System Central nervous system (_______________) Brain and spinal cord Integrating and command center Peripheral nervous system (________________) Cranial nerves and spinal nerves Communication lines between the CNS and the rest of the body ____________________________ Classification of the Nervous System Peripheral nervous system Two subdivisions Sensory (____________________________) division Carry information _____________________ the CNS Motor (____________________________) division Carry information _____________________ from the CNS Somatic nervous system ____________________________ and conscious control ____________________________ muscles Autonomic nervous system ____________________________ and subconscious __________________ muscles, ______________ muscles and ______________ Sympathetic ____________________________ Parasympathetic ____________________________ Nervous Tissue Two principal types of cells Support cells (__________________________) Support, insulate and protect the neurons Cannot transmit nerve impulses Continue to divide 4 in the CNS and 2 in the PNS ________________________ Structural units of the nervous system Transmit electrical impulses from one area of the body to another area using neurotransmitters Nervous Tissue: Support Cells (neuroglia) in ___________________________ Astrocytes Abundant, star-shaped cells ______________________ and ______________________ neurons Form barrier and make exchanges between capillaries and neurons Control the chemical environment of the brain by cleaning up potassium ions and neurotransmitters Microglia Small ovoid cells with thorny processes Spider-like ___________________________________ Dispose of debris Ependymal cells Line central cavities of the brain and spinal cord Cells are squamous and columnar shaped and ciliated _____________________________ cerebrospinal fluid Oligodendrocytes Produce ______________________ __________________ (fatty insulation) around nerve fibers Nervous Tissue: Support Cells in ____________________________ Satellite cells Surround neuron cell bodies located in the PNS ____________________________ and ________________________ neurons Similar to astrocytes Schwann cells Surround and form ______________________ _____________________ in the PNS Help with regeneration of damaged peripheral nerve fibers Nervous Tissue: Neurons Structural unit of the nervous system Highly specialized cells that conduct messages in the form of impulses from one part of the body to another Special characteristics ____________________________ (about 100 years) ____________________________ (cannot divide) ____________________________ Vary in structure but all have a cell body and one or more slender processes Plasma membrane is the site of electrical signaling Major regions of neurons Cell body (___________________________) Nucleus and metabolic center Most are located in the CNS Clusters of cell bodies in the CNS are called _________________________ Lie along the nerves in the PNS are called ___________________________ Processes (__________________________ and ____________________________) Arm like processes that extend from the body of all neurons CNS contain both cell bodies and their processes PNS consists mainly of neuron processes Bundles of neuron processes are called __________________ (CNS) or ___________________ (PNS) Neuron Processes Dendrites Main receptive or input region ________________________ signals from other neurons Conduct impulses ________________________ the cell body Axons Each neuron has only ____________________ axon Conducting region of the neuron _____________________________ nerve impulses Transmits impulses _________________ from the cell body Initial region of the axon arises from the ________________ ____________________ Narrows to form a slender process the rest of the length In some neurons the axon is very short and in others it is very long Ex: axons of toes extend from your spine to your foot (about 3-4 feet) – the longest cells in your body Axons and Axonal Terminals Axons can branch many times but all end in _________________ ______________________ Axon terminals Knoblike distal endings When impulses reaches the terminal it causes ___________________________________ to be released Neurotransmitters either ________________________ or __________________________ neurons Neurons never touch other neurons Separated from the next neuron by a gap ________________________________ Gap between adjacent neurons Axon Coverings Many axons are covered with a whitish, fatty, segmented ________________ ______________ _________________________ Covering that protects and insulates the axons and increases the speed of transmission of nerve impulses ________________________ ____________________________ A tight coil of wrapped myelin encloses the axon Peripheral nervous system Formed by ___________________________ which wrap themselves around the axon in jelly-roll fashion Central nervous system Formed by ______________________________ _______________________ of ____________________________ Adjacent Schwann cells and oligodendrocytes do not touch each other so there are gaps in the myelin _______________________________ fibers conduct nerve impulses rapidly _______________________________ fibers conduct impulses slowly Multiple Sclerosis (______________________________) Myelin sheath in the CNS are damaged and demyelination occurs Affects the ability of nerve cells to communicate with each other Caused by an __________________ disease where the body’s own immune system attacks and damages the myelin Electrical signals are slowed or stopped from reaching different parts of the body. Person loses ability to control his/her muscles Cause is unknown and there is no cure Neuron Cell Body Locations Most are found in the ______________________________________________ White matter Dense collections of __________________________ fibers Gray matter ___________________________ fibers and cell bodies Nuclei Clusters of cell bodies within the ________________________ matter of the central nervous system Outside the CNS ________________________: Collections of cell bodies Neuron Classification Neurons classified based on their structure and function Structural Classification of Neurons Multipolar neurons Three or more processes One axon and the rest dendrites Most common neuron type (_____________________ and _____________________________) Major neuron type in CNS Bipolar neurons Two processes An axon and a dendrite from opposite sides of the cell body _______________________________, found in special sensory organs Unipolar neurons Have a short single process leaving the cell body Mainly found in ______________________________ of PNS (sensory neurons) Functional Classification of Neurons Neurons classified based on the _________________________ the nerve impulse travels in relation to the CNS _________________________________________ _________________________________________ _________________________________________ Sensory (__________________________________) neurons Transmit impulses _______________________________ the CNS Sensory receptors in the skin or internal organs Cutaneous sense organs (________________________ and ____________________ corpuscles) ___________________________ (detect stretch or tension in organs) Motor (____________________________________) neurons Transmit impulses ____________________________ from the CNS Muscles or glands Association (____________________________________) Found between motor and sensory neurons In neural pathways in the CNS Make up 99% of the neurons of the body Amyotrophic lateral sclerosis (ALS) “Lou Gehrig’s Disease” Disease of the _________________________ neurons in the CNS that control voluntary movements Motor neurons degenerate or die and can no longer send messages to voluntary muscles Condition gets worse and usually ends in paralysis and death in about 3-5 years Cause is unknown (about 10% are genetic) Amyotrophic Muscle without ___________________________________ Sclerosis ___________________________________ of tissue