11a_nervous_system.pdf - Name(s Mr Frazer Human Anatomy and...

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Mr. Frazer; Human Anatomy and Physiology Lab Activity by HASPI The Nervous System The nervous system is an incredibly complex network of tissues that are capable of carrying information throughout the human body. The two primary cells of the nervous system are neurons, that actually carry and store information, and glial cells that support the neurons. The nervous system is broken up into a few systems depending on the function and location. Central Nervous System The central nervous system, or CNS, is made up of the brain and spinal cord. The retina of the eye is also considered part of the central nervous system. The brain is the control center of the body and is housed within the protective hard skull. Layers of tissues called meninges and cerebrospinal fluid also protect the CNS. The spinal cord extends from the brainstem through the vertebral column. There are 31 segments to the spinal cord, and a pair of spinal nerves extends from each segment into the body. Peripheral Nervous System There are 43 pairs of nerves that connect the central nervous system to the rest of the body, and they make up the peripheral nervous system or PNS. The PNS is made up of sensory neurons that are capable of receiving stimuli, and motor neurons that are capable of responding to stimuli. For example, sensory neurons in the eye are capable of receiving light stimuli and motor neurons are attached to muscles that can create movement. The PNS is broken down into the somatic and autonomic nervous systems, and the autonomic is further broken down into the sympathetic and parasympathetic nervous systems. Diagram A summarizes the relationship between these systems. The somatic NS is the voluntary system that can be controlled consciously, such as movement of muscles. The autonomic NS is the involuntary system and controls unconscious impulses such as the heartbeat. The sympathetic and parasympathetic systems work opposite of one another. For example, the sympathetic system speeds up the heart rate while the parasympathetic system slows down the heart rate. The Neuron The neuron is the functional cell of the nervous system. It can send and receive nerve impulses. There are billions of neurons in the body, with more than 100 billion on the surface of the brain alone. Even so, approximately 90% of cells in the brain are supportive glial cells and only 10% are actual neurons. Neurons are made up of a cell body, dendrites, an axon, and axon terminals. When Name(s): ________________________ Period: _________ Date: ___________ 20/jpg/nervous_system_organization1328056081853.jpg Diagram A
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something stimulates a dendrite, the nerve impulse travels through the dendrite, to the cell body down the axon and axon terminals, where the impulse will be passed to the dendrites of the next neuron to perpetuate the impulse. Sensory neurons have a single specialized dendrite to receive stimuli while motor neurons have many dendrites.
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