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Anatomy & Physiology: A Unity of Form and Function

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Unformatted text preview: Nervous Tissue ● overview of the nervous system ● properties of neurons ● supportive cells (neuroglia) ● electrophysiology of neurons ● synapses ● neural integration ¡¢£¡ ¡¢£¢ Overview of Nervous System ● endocrine and nervous system maintain internal coordination ○ endocrine system- communicates by means of chemical messengers ( hormones ) secreted into to the blood ○ nervous system- employs electrical and chemical means to send messages from cell to cell ● nervous system carries out its task in three basic steps : ■ sense organs receive information about changes in the body and the external environment, and transmits coded messages to the spinal cord and the brain ■ brain and spinal cord processes this information , relates it to past experiences, and determine what response is appropriate to the circumstances ■ brain and spinal cord issue commands to muscles and gland cells to carry out such a response ¡¢£¤ ● sensory ¥afferent¦ division – carries sensory signals from various receptors to the CNS ● informs the CNS of stimuli within or around the body ● somatic sensory division – carries signals from receptors in the skin, muscles, bones, and joints ● visceral sensory division – carries signals from the viscera of the thoracic and abdominal cavities ○ heart, lungs, stomach, and urinary bladder Sensory 'ivisions of PNS ¡¢£¤ ● motor ¥efferent¦ division – carries signals from the CNS to gland and muscle cells that carry out the body’s response ■ effectors – cells and organs that respond to commands from the CNS ○ somatic motor division – carries signals to skeletal muscles ■ output produces muscular contraction as well as somatic reflexes – involuntary muscle contractions ○ visceral motor division ( autonomic nervous system ) - carries signals to glands, cardiac muscle, and smooth muscle ■ involuntary, and responses of this system and its receptors are visceral reflexes ■ sympathetic division ■ tends to arouse body for action ■ accelerating heart beat and respiration; inhibits digestive and urinary systems ■ parasympathetic division ■ tends to have calming effect ■ slows heart rate and breathing; stimulates digestive and urinary systems Motor 'ivisions of PNS ¡¢£¤ Universal Properties of Neurons ● excitability ( irritability ) ○ respond to environmental changes called stimuli ● conductivity ○ neurons respond to stimuli by producing electrical signals that are quickly conducted to other cells at distant locations ● secretion ○ when electrical signal reaches end of nerve fiber, a chemical neurotransmitter is secreted that crosses the gap and stimulates the next cell Structure of a Neuron ● soma – the control center of the neuron ○ also called neurosoma , cell body , or perikaryon ○ has a single, centrally located nucleus with large nucleolus ○ cytoskeleton consists of dense mesh of microtubules and neurofibrils (bundles of actin filaments)...
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Chapter_12 - Nervous Tissue ● overview of the nervous...

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