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Download Information Processing The Central Nervous System Peripheral
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Divisions of the Nervous System Information Processing The Nervous System The Central Nervous System The central nervous system is divided into two major parts: the brain and the spinal cord. In the average adult human, the brain weighs 1.3 to 1.4 kg (about 3 pounds). The brain contains about 100 billion nerve cells (neurons) and trillons of "support cells" called glia. The spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35-40 gm. The vertebral column, the collection of bones (back bone) that houses the spinal cord, is about 70 cm long. So the spinal cord is much shorter than the vertebral column. Peripheral Nervous System • • • This system is made up of two major divisions – the sensory and motor divisions. The sensory division carries information toward the CNS from the sense organs. The motor division is comprised of the voluntary somatic nervous system and the involuntary autonomic nervous system. Both carry info from the CNS to effector organs. 1 The Sensory System Activates the Nervous System • The senses allow the organism to monitor changes in the external environment. • The senses receive the stimulus, transduce the stimulus to an electrical signal, sometimes amplify the signal and then transmit the signal to the CNS. Autonomic Nervous System Something that is autonomic can run on its own, like automatic. The ANS is made up of nervous tissue that controls involuntary organ and bodily function. For example, it is your autonomic nervous system that commands smooth muscle to contract in blood vessels so that the vessels constrict. It also controls all major organs and their actions. The two divisions are the sympathetic and parasympathetic divisions. TYPES OF SENSORS • Mechanoreceptors – Pacinian corpuscles – Merkel cells – Meissner's corpuscles – muscle spindles – hair cells » auditory » lateral line in fish » equilibrium • Chemoreceptors – osmoreceptors – multiple classes of taste receptors – multiple classes of olfactory receptors • Thermoreceptors – Ruffini's organ – end-bulbs of Krause • Pain • Electromagnetic receptors – electroreceptors – magnetoreceptors – infrared receptors – vision Autonomic Nervous System The following website has an excellent learning module on the autonomic nervous system. Using the website answer the appropriate questions that are listed on your question sheet. http://webx.washcoll.edu/wc.html/siemen/ans.html 2
