Chapter 7: Nervous System

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Nervous System

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Brain, spinal chord, nerves, neurons (cells), neuroglia (helper cells), master control and communication system, in charge of involuntary control (homeostasis), voluntary control (movement of skeletal muscles), higher processing (thoughts, learning, memory), reflexes, its signalling device is rapid, specific electrical impulses, that cause immediate responses, 3 overlapping functions: 1. Sensory input- sensory receptors monitor changes/stimuli occurring inside and outside body 2. Integration- processes and interprets sensory input and decides what should be done 3. Motor output- effects or causes a response by activating muscles/glands

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Central Nervous System

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CNS, structural classification, brain, spinal chord, act as integrating and command centers of nervous system, interpret incoming sensory info and issue instructions based on past experiences and current conditions

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Interneuron

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Found in brain/spinal chord, in between neurons, when a sensory neuron comes in an interneuron will be in between the sensory neuron and the motor neuron

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Peripheral Nervous System

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PNS, structural classification, consists of nerves that extend from the brain and spinal chord, spinal nerves carry impulses to and from spinal chord, cranial nerves carry impulses to and from the brain, nerves are communication lines, they link all parts of the body by carrying impulses from the sensory receptors to the CNS and from CNS to the muscles and glands

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Sensory/Afferent Division

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Functional classification, afferent means to affect, consists of nerves that convey impulses to the central nervous system from sensory receptors in the body, keeps the CNS informed of events inside and outside the body, emotions/feelings

1. Somatic sensory fibres- sensory nerve fibres transmitting impulses from the skin, muscles & joints

2. Visceral sensory fibres- sensory nerve fibres transmitting impulses from the visceral organs

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Motor/efferent division

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Functional classification, efferent means effect, carries impulse from CNS to effector organs- muscles/glands, activates muscles/glands effecting a motor response, outgoing message causing something to happen

1. Somatic/voluntary nervous system- allows us to consciously or voluntarily control our skeletal muscles

2. Autonomic/involuntary Nervous System- regulates events that are automatic or involuntary, activity of smooth (organs) and cardiac (heart) muscles and glands, two parts: parasympathetic & sympathetic

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Neuroglia

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Supporting cells in the CNS, nerve glue, many types of cells that support, insulate and protect the delicate neurons

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Neurons

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Nerve cells, highly specialized to transmit messages/nerve impulses from one part of the body to another, all have cell body and processes

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Cell body

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Metabolic Center of neuron, contains nucleus, cytoplasm with Golgi apparatus and mitochondria, nissl bodies and neurofibrils

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Processes

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Armlike, vary in length microscopic to 7feet, longest go from lumbar spine to big toe

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Dendrites

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Processes that convey incoming messages from neurons (electrical signals) toward the cell body, many dendrites

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Axon

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Processes that generate nerve impulses away from/leaving the cell body, only one axon, axons branch at their terminal end forming axon terminals, terminals contain tiny vesicles or membrane sacs containing neurotransmitters, separated from the next neuron by the synaptic cleft making neurons close but never touching

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Myelin Sheath

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Whitish fatty material called myelin that covers nerve fibres, protects and insulates fibres, increases speed of nerve impulses, axons outside the CNS are myelinated by Schwann cells, spaces between Schwann cells are called Nodes of Ranvier

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Nodes of Ranvier

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Spaces between Schwann cells, influence our ability to send messages quickly

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Sensory Neuron

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Functional classification, carry impulses from sensory receptors in the internal organs or skin to the CNS, keep us informed about what's happening inside and outside the body

-receptors in skin are called cutaneous sense organs

-receptors in muscles and tendons are called proprioceptors

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Proprioceptors

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Detect the amount of Stretch or tension in skeletal muscles their tendons and joints, send this information to the brain so that proper adjustments can be made to maintain balance and normal posture

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Motor neuron

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Functional classification, carrying impulses from CNS to viscera or muscles or glands

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Associated neurons

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Functional classification, connect motor and sensory neurons in neural pathways

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Multipolar neuron

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Structural classification, several processes extending from cell body (most common)

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Bipolar neuron

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Structural classification, two processes extending from cell body an axon & dendrite, rare in adults, found in eye and nose act in sensory processing as receptor cells

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Unipolar Neuron

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Structural classification, single process emerging from cell body, short and divides almost immediately in proximal and distal processes, small branches at the end of the peripheral process are dendrites, remainder of peripheral processes and the central process function as axons, axons conducts impulse toward and away from cell body