Transcript Lecture 11 - Websupport1

Anatomy & Physiology
Lecture 12: Chapter 16
Neural Integration II: The Autonomic
Nervous System and Higher Order
Functions.
Pages: 517 - 548
Lecturer: Dr. Barjis
Room P313 /P307
Phone: (718) 260-5285
E-Mail: [email protected]
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
• 2nd 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
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
Sympathetic division anatomy
• Preganglionic neurons are located in the latheral
gray horns between segments T1 and L2 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
AChE 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.