BIOL164Ch8NotesWin12

BIOL164Ch8NotesWin12 - Ch 8 The Nervous System The...

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1 Ch. 8 – The Nervous System The organization of the nervous system • I. CNS (central nervous system) = the brain and spinal cord; this is the central command center that integrates and coordinates all voluntary and involuntary nervous functions; the “decider” • II. PNS (peripheral nervous system) = nerves (both spinal nerves and cranial nerves); these carry messages to and from the CNS –A . Sensory (afferent) division : brings sensory information from receptors to the CNS –B . Motor (efferent) division : carries motor commands from the CNS to effectors (i.e., muscles and glands) •1 . Somatic NS : voluntary (conscious) control of skeletal muscle •2 . Autonomic NS : involuntary (subconscious) control of smooth muscle, cardiac muscle, and glands –a . Sympathetic NS (division) : prepares the body to deal with stressful or emergency conditions – a.k.a. the “fight-or-flight” division –b
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2 A somewhat useful organizational chart of the nervous system Figure 8.1 Protection of the CNS •T h e meninges : Dura mater (the outermost layer) Arachnoid (arachnoid mater) (the middle layer) • CSF is found in the subarachnoid space between the arachnoid and pia mater – CSF is also found in the CNS’s hollow internal spaces (i.e., the brain ventricles and the central canal of the spinal cord) – Besides providing cushioning and support, CSF also nourishes nervous tissue Pia mater (the innermost layer) • The CNS is also protected from harmful substances in the blood by the blood- brain barrier (which is formed mainly by non-leaky capillaries and astrocytes)
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3 White matter (a lot of myelin is present) consists of: – Myelinated axons (with some unmyelinated axons mixed in), which are myelinated by… • Schwann cells in the PNS • Oligodendrocytes in the CNS Gray matter (little myelin is present) consists of: – Neuron cell bodies and dendrites – Unmyelinated axons – Interneurons and synapses – Neuroglia (astrocytes, etc.) A quick note about white matter vs. gray matter Figure 8.9a The brain • Weighs about 3 pounds, and contains about 100 billion neurons and 1 trillion glial cells
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4 The brain has 4 main regions 4. 3. Diencephalon
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BIOL164Ch8NotesWin12 - Ch 8 The Nervous System The...

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