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Chapter 12 - The Nervous System

Chapter 12 - The Nervous System - Chapter 12 An...

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Chapter 12 - An Introduction to the Nervous System The Nervous System includes all neural tissue in the body & contains two kinds of cells 0. Neurons : cells that send and receive signals 1. Neuroglia (glial cells): cells that support and protect neurons Organs of the Nervous System i. Brain and spinal cord ii. Sensory receptors of sense organs (eyes, ears, etc.) iii. Nerves connect nervous system with other systems Divisions of the Nervous System - Anatomical Divisions of the Nervous System Central nervous system ( CNS ) & Peripheral nervous system ( PNS ) Central Nervous System (CNS) consists of the spinal cord & brain; contains neural tissue, connective tissues & blood vessels Functions of the CNS are to process and coordinate: sensory data: from inside and outside body o Motor commands: control activities of peripheral organs (e.g., skeletal muscles) o Higher functions of brain: intelligence, memory, learning, emotion The Peripheral Nervous System ( PNS ) includes all neural tissue outside the CNS Functions of the PNS Deliver sensory information to the CNS Carry motor commands to peripheral tissues and systems Nerves (peripheral nerves): bundles of axons with connective tissues & blood vessels that carry sensory information & motor commands in PNS: 0. cranial nerves connect to brain 1. spinal nerves attach to spinal cord Divisions of the Nervous System - Functional Divisions of the PNS Afferent division carries sensory information from PNS sensory receptors to CNS Efferent division carries motor commands from CNS to PNS muscles and glands Receptors and effectors of afferent division Receptors : detect changes/respond to stimuli: neurons, specialized cells & complex sensory organs (e.g., eyes, ears) Effectors : respond to efferent signals - cells and organs The Efferent Division Somatic nervous system ( SNS ): controls skeletal muscle contractions: voluntary & involuntary (reflexes) muscle contractions Autonomic nervous system ( ANS ): controls subconscious actions like contractions of smooth muscle & cardiac muscle & glandular secretions o sympathetic division : has a stimulating effect o parasympathetic division : has a relaxing effect Neurons - the basic functional units of the nervous system Structure of Neurons: multipolar neuron is common in CNS, it has a cell body (soma), short, branched dendrites & a long, single axon Major Organelles of the Cell Body i. Large nucleus and nucleolus ii. Perikaryon ( cytoplasm) iii. Mitochondria (produce energy) iv. RER and ribosomes (produce neurotransmitters) v. Cytoskeleton - Neurofilaments and neurotubules : in place of microfilaments and microtubules Neurofibrils : bundles of neurofilaments that provide support for dendrites and axon iv. Nissl bodies - dense areas of RER & ribosomes; make it appear gray (gray matter) v.
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