Anatomy Physiology Lecture 12 Chapter 16 Neural Integration

Anatomy & Physiology Lecture 12: Chapter 16 Neural Integration II: The Autonomic Nervous System and Higher Order Functions. Pages: 517 - 548 Lecturer: Dr. Barjis Room P 313 /P 307 Phone: (718) 260 -5285 E-Mail: ibarjis@citytech. cuny. edu Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Frederic H. Martini Fundamentals of

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.

An Overview of the ANS Autonomic Nervous System (ANS) • Routin homeostatic adjustments in physiological systems are made by ANS • Coordinates cardiovascular, respiratory, digestive, urinary and reproductive functions • In ANS there is always a synapse between CNS and the effector organs • 2 nd order neurons of the autonomic nervous system are located in autonomic ganglia

An Overview of the ANS • Preganglionic neurons in the CNS send axons to synapse on ganglionic neurons in autonomic ganglia outside the CNS (brain and Spinal Cord) Postganglionic Ganglion Preganglionic • Preganglionic neuron’s body lies in the CNS • Postganglionic axons of ANS are usually unmyelinated

Divisions of the ANS • ANS contain two primary subdivisions: • Sympathetic division (thoracolumbar, “fight or flight”) – prepare body for stress and activity • Thoracic and lumbar segments • Parasympathetic division (craniosacral, “rest and repose”) – Maintains homeostasis at rest • Preganglionic fibers leaving the brain and sacral segments • Often the two divisions have opposing effects e. g. one would excite and the other will inhibit. • Sometime they may also work together or independently.

Sympathetic division anatomy • Preganglionic neurons are located in the latheral gray horns between segments T 1 and L 2 of spinal cord • Ganglionic neurons in ganglia near vertebral column • Specialized second order neurons of the sympathetic NS that release neurotransmitter into blood are located in adrenal glands

The Organization of the Sympathetic Division of the ANS

Sympathetic ganglia • Sympathetic chain ganglia (paravertebral ganglia) – preganglionic fibers of the sympathetic NS that carry motor impulses to the body wall or thoracic cavity synapses in chain ganglia • Collateral ganglia (prevertebral ganglia) – group of second order neurons that innervate organs in the abdominopelvic region

Sympathetic Pathways

Sympathetic Pathways

Sympathetic Pathways

The Distribution of Sympathetic Innervation Animation: The sympathetic division (see tutorial)

Postganglionic fibers • Rejoin spinal nerves and reach their destination by way of the dorsal and ventral rami • Those targeting structures in the thoracic cavity form sympathetic nerves • Go directly to their destination

Abdominopelvic viscera • Sympathetic innervation via preganglionic fibers that synapse within collateral ganglia • Splanchic nerves – carry fibers that synapse in collatheral ganglia

Abdominopelvic viscera • Celiac ganglion • Innervates stomach, liver, gall bladder, pancreas, spleen • Superior mesenteric ganglion • Innervates small intestine and initial portion of large intestine • Inferior mesenteric ganglion • Innervates kidney, urinary bladder, sex organs, and final portion of large intestine

Sympathetic activation • Sympathetic activation is controlled by sypathetic centers in the hypothalamus. • 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

Sympathetic Variosities

Parasympathetic division • Preganglionic neurons in the brainstem and sacral segments of spinal cord • Ganglionic neurons in peripheral ganglia located within or near target organs

The Organization of the Parasympathetic Division of the ANS

Organization and anatomy of the parasympathetic division • Preganglionic fibers of parasympathetic neurons can be found in cranial nerves III, VI, IX, X • Sacral neurons form the pelvic nerves • Almost 75% of all parasympathetic outflow travels along the vagus nerve (cranial nerve X)

The Distribution of Parasympathetic Innervation

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 ACh. E and tissue cholinesterase

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 • Effects produced by the parasympathetic branch include increased secretion by digestive glands • Dual innervation = organs that receive input from both systems

Anatomy of dual innervation • Sympathetic and parasympathetic systems intermingle to form autonomic plexuses • Cardiac plexus – sympathetic and parasympathetic fibers bound for the heart and kungs pass through the cardiac plexus • Pulmonary plexus • Esophageal plexus • Celiac plexus • Inferior mesenteric plexus • Hypogastric plexus

The Autonomic Plexuses

Comparison of the two divisions • Important physiological and functional differences exist

Summary: The Anatomical Differences between the Sympathetic and Parasympathetic Divisions

A Comparison of Somatic and Autonomic Function

Higher levels of autonomic control • Activity in the ANS is controlled by centers in the brainstem that deal with visceral functioning

Levels of Autonomic Control Example of higher-level of autonomic function would be increased heart rate when you see a person that you dislike.

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 • Hippocampus is essential for memory consolidation • Mechanisms involved in memory formation and storage are: • Increased release of neurotransmitter • Formation of additional synaptic connection • Formation of memory engrams (single circuit that correspond to single memory) • Amnesia is the loss of memory due to disease or trauma

Memory • Memory that can be voluntarily retrieved and verbally expressed are called declarative memories • Conversion of a short term memory to a long term memory is called memory consolidation

Memory Storage

Consciousness • Deep sleep, the body relaxes and cerebral cortex activity is low • The reticular activating system (RAS) is important to arousal and maintenance of consciousness • RAS is located in the mesencephalon

The Reticular Activating System

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.