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Explore the ANS structures, neurotransmitter mechanisms, aging effects & higher order functions in the CNS. Learn the organization of the sympathetic & parasympathetic divisions.
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Chapter 16, part 1 Neural Integration II: The Autonomic Nervous System and Higher Order Functions
Learning Objectives • Compare the organization of the autonomic nervous system with the somatic nervous system. • Describe the structures and functions of the sympathetic and parasympathetic divisions of the ANS. • Describe the mechanisms of neurotransmitter release in the sympathetic and parasympathetic divisions. • Describe the effects of sympathetic and parasympathetic neurotransmitters on target organs and tissues.
Learning Objectives • Describe the hierarchy of interacting levels of control in the ANS • Explain how memories are created, stored and recalled. • Summarize the effects of aging on the nervous system.
ANS • Coordinates cardiovascular, respiratory, digestive, urinary and reproductive functions • Preganglionic neurons in the CNS send axons to synapse on ganglionic neurons in autonomic ganglia outside the CNS
Divisions of the ANS • Sympathetic division (thoracolumbar, “fight or flight”) • Thoracic and lumbar segments • Parasympathetic division (craniosacral, “rest and repose”) • Preganglionic fibers leaving the brain and sacral segments
Sympathetic division anatomy • Preganglionic neurons between segments T1 and L2 • Ganglionic neurons in ganglia near vertebral column • Specialized neurons in adrenal glands
Figure 16.3 The Organization of the Sympathetic Division of the ANS Figure 16.3
Sympathetic ganglia • Sympathetic chain ganglia (paravertebral ganglia) • Collateral ganglia (prevertebral ganglia)
Figure 16.5 The Distribution of Sympathetic Innervation PLAY Animation: The sympathetic division Figure 16.5
Sympathetic activation • In crises, the entire sympathetic division responds • Sympathetic activation • Affects include increased alertness, energy and euphoria, increased cardiovascular and respiratory activities, elevation in muscle tone, mobilization of energy resources
Neurotransmitters and sympathetic function • Stimulation of sympathetic division has two distinct results • Release of ACh or NE at specific locations • Secretion of E and NE into general circulation • Most postganglionic fibers are adrenergic, a few are cholinergic or nitroxidergic • Two types of receptors are alpha receptors and beta receptors • Sympathetic ganglionic neurons end in telodendria studded with varicosities filled with neurotransmitter
Figure 16.6 Sympathetic Variosities Figure 16.6
Parasympathetic division • Preganglionic neurons in the brainstem and sacral segments of spinal cord • Ganglionic neurons in peripheral ganglia located within or near target organs
Figure 16.7 The Organization of the Parasympathetic Division of the ANS Figure 16.7
Figure 16.8 The Distribution of Parasympathetic Innervation Figure 16.8
Parasympathetic activation • Effects produced by the parasympathetic division • relaxation • food processing • energy absorption
Neurotransmitters and parasympathetic functions • All parasympathetic fibers release ACh • Short-lived response as ACH is broken down by AChE and tissue cholinesterase • Postsynaptic membranes have two kinds of receptors • Muscarinic • Nicotinic
SECTION 16-4Interactions Between the Sympathetic and Parasympathetic Divisions
Sympathetic and parasympathetic divisions • Sympathetic • Widespread influence on visceral and somatic structures • Parasympathetic • Innervates only visceral structures serviced by cranial nerves or lying within the abdominopelvic cavity • Dual innervation = organs that receive input from both systems
Comparison of the two divisions • Important physiological and functional differences exist
Figure 16.10 Summary: The Anatomical Differences between the Sympathetic and Parasympathetic Divisions Figure 16.10
Higher levels of autonomic control • Activity in the ANS is controlled by centers in the brainstem that deal with visceral functioning
Figure 16.12 Levels of Autonomic Control Figure 16.12
SNS and ANS organized in parallel • Integration occurs at the brainstem and higher centers
Figure 16.13 A Comparison of Somatic and Autonomic Function Figure 16.13
Higher order functions • Are performed by the cerebral cortex and involve complex interactions • Involve conscious and unconscious information processing • Are subject to modification and adjustment over time
Memory • Short term or long term • Memory consolidation is moving from short term to long term • Amnesia is the loss of memory due to disease or trauma
Figure 16.14 Memory Storage Figure 16.14
Consciousness • Deep sleep, the body relaxes and cerebral cortex activity is low • REM sleep active dreaming occurs • The reticular activating system (RAS) is important to arousal and maintenance of consciousness
Figure 16.16 The Reticular Activating System Figure 16.16
Neurotransmitters and the brain • Neurotransmitters and brain function • Changes in balance between neurotransmitters can profoundly alter brain function • Personality and self-awareness • Characteristics of the brain as an integrated system rather than one specific component
Age-related changes • Reduction in brain size and weight • Reduction in the number of neurons • Decrease in blood flow to the brain • Changes in synaptic organization of the brain • Intracellular and extracellular changes in CNS neurons
You should now be familiar with: • The organization of the autonomic nervous system. • The structures and functions of the sympathetic and parasympathetic divisions of the ANS. • The mechanisms of neurotransmitter release in the sympathetic and parasympathetic divisions. • The effects of sympathetic and parasympathetic neurotransmitters on target organs and tissues. • The hierarchy of interacting levels of control in the ANS. • How memories are created, stored and recalled. • The effects of aging on the nervous system.
