Download Higher-Order Functions

Chapter
16
Neural Integration
II: The Autonomic
Nervous System
and Higher-Order
Functions
PowerPoint® Lecture Slides
prepared by Jason LaPres
Lone Star College - North Harris
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Copyright © 2009 Pearson Education, Inc.,
publishing as Pearson Benjamin Cummings
An Introduction to the ANS
Autonomic Nervous System (ANS)
 coordinates cardiovascular, respiratory,
digestive, urinary, and reproductive functions
 Two subdivisions
 Sympathetic division
 Parasympathetic division
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Sympathetic Division

Sympathetic Division
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Prepares the body for heightened levels of
somatic activity
Produces the “fight or flight” response
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heightened mental alertness
increased metabolic rate
reduced digestive and urinary functions
activation of energy reserves
increased respiratory rate
increased heart rate
activation of sweat glands
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Sympathetic Division
 Preganglionic fibers are short and the
postganglionic fibers are long
 preganglionic fibers from the thoracic and superior
lumbar segments (T1 to L2) of the spinal cord
synapse in ganglia near the spinal cord
 The cell bodies of the preganglionic
neurons are situated in the lateral gray
horns, and their axons enter the ventral
roots of these segments.
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Sympathetic Division
 The ganglionic neurons occur in three locations:
Sympathetic Chain Ganglia
– Lie on both sides of the vertebral column
– These neurons control effectors in the body wall, inside the thoracic cavity,
and in the head and limbs
Collateral Ganglia
– Anterior to the vertebral bodies
– These neurons innervate tissues and organs in the abdominopelvic cavity
– Preganglionic fibers that innervate the collateral ganglia form the splanchnic
nerves. They originate as a paired ganglia but typically fuse together as one
in adults
– The splanchnic nerves innervate three collateral ganglia:
» celiac ganglion
» superior mesenteric ganglion
» inferior mesenteric ganglion
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Sympathetic Division
Adrenal Medullae
– Center of each adrenal gland (adrenal medulla) is a
modified sympathetic ganglion
– These neurons release the neurotransmitters
epinephrine (E) and norepinephrine (NE) into the
bloodstream when stimulated
– Function as hormones that affect target cells throughout
the body
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Sympathetic Division
 Sympathetic Activation
 Occurs in a crisis so the person can cope with a
stressful situation
 Controlled by sympathetic centers in the hypothalamus
 The following changes occur when activated:
 increased alertness causing the person to feel “on edge”
 a feeling of energy and euphoria which is associated with a
disregard for danger and a temporary insensitivity to painful
stimuli
 elevations in blood pressure, heart rate, and breathing
 general elevation in muscle tone
 mobilization of energy reserves
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Sympathetic Division
 The sympathetic division releases:
 Acetylcholine
 Syapses that release ACh are called cholinergic
 has an excitatory effect on the ganglionic neurons which leads to
the release of neurotransmitters at specific target organs
 Instead of fording synaptic knobs, telodendria form a branch
network. Each branch contains swollen segments called
varicosities that are packed with neurotransmitter vesicles.
 Norepinephrine
 Neurons that use NE as a neurotransmitter are called adrenergic
 NE released by varicosities affect its targets united it is reabsorbed
or inactivated by the enzymes MAO and COMT when it diffuses out
of the area
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Sympathetic Division
 There are two classes of sympathetic receptors:
 Alpha receptors
 Activates enzymes on the inside of the cell membrane
 Two types of alpha receptors
– a1
» more common type of alpha receptor
» function is the release of intracellular calcium ions from
reserves in the endoplasmic reticulum
» has an excitatory effect on the target cell
– a2
» results in a lowering of cAMP in the cytoplasm
» inhibitory effect on the cell
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Sympathetic Division
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Beta receptors
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located on the membranes of cells in many organs (skeletal muscles,
lungs, heart, liver)
stimulation triggers changes in the metabolic activity of the target cell
three types of beta receptors:

B1
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B2
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Stimulation leads to an increase in metabolic activity
Stimulation causes inhibition, triggering a relaxation of smooth muscles along the
respiratory tract
This response accounts for the effectiveness of inhalers used to treat asthma
B3
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Found in adipose tissue
Stimulation leads to lipolysis – breakdown of triglycerides stored within adipocytes
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Parasympathetic Division
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Parasympathetic Division
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Preganglionic fibers are long and the postganglionic
fibers are short because they synapse in ganglia
very close to the target organ
Stimulates visceral activity
Produces the “rest and repose” response that
follows a big meal
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decreased metabolic rate
decreased heart rate and blood pressure
increased secretion by salivary and digestive glands
increased motility and blood flow in the digestive tract
stimulation of urination and defecation
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Parasympathetic Division
 All parasympathetic neurons release ACh as a
neurotransmitter, but there are two types:
 Nicotinic Receptors
 Bind nicotine
 Causes excitation of the ganglionic neuron or muscle fiber by
the opening of chemically gated channels in the postsynaptic
membrane
 Muscarinic Receptors
 Stimulated by muscarine
 G proteins whose stimulation produces longer-lasting effects
than does the stimulation of nicotinic receptors
 Response can be inhibitory or excitatory
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Dual Innervation
 Although some organs are innervated by
just one division, most vital organs receive
instructions from both the sympathetic
and parasympathetic divisions (dual
innervation).
 Where dual innervation exists, the two
divisions commonly have opposing effects.
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Autonomic Tone
 Autonomic Tone
 Even in the absence of stimuli, autonomic motor
neurons show a resting level of spontaneous activity.
The background level of activation determines an
individual’s autonomic tone.
 If a nerve is absolutely inactive under normal
conditions, then all it can do is increase its activity on
demand. But if the nerve maintains a background level
of activity, it can increase or decrease its activity,
producing a greater range of control options.
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Integration and Control of Autonomic
Functions
 Integration and Control of Autonomic
Functions
 The ANS is organized into a series of interacting
levels. At the bottom are visceral motor neurons
in the lower brain stem and spinal cord that are
involved in cranial and spinal visceral reflexes.
 Visceral reflexes provide automatic motor
responses that can be modified, facilitated, or
inhibited by higher center, especially those of the
hypothalamus.
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Visceral reflexes
 Visceral reflexes
 Each visceral reflex arc consists of a receptor, a sensory neuron, a
processing center (one or more interneurons), and two visceral motor
neurons.
 All are polysynaptic
 They are either:
 1. long reflexes
– the autonomic equivalents of the polysynaptic reflexes
– visceral sensory neurons deliver information to the CNS along the dorsal roots of
spinal nerves, within the autonomic nerves that innervate visceral effectors.
– Control activities of an entire organ
 2. short reflexes
– bypass the CNS entirely
– they involve sensory neurons and interneurons whose cell bodies are located within
autonomic ganglia
– control very simple motorized responses with localized effects
– control patterns of activity in one small part of a target organ
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Higher-Order Functions
Higher-Order Functions
 Share three functions:
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The cerebral cortex is required for their performance,
and they involve complex interactions among areas of
the cortex and between the cerebral cortex and other
areas of the brain.
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They involve both conscious and unconscious
information processing.
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They are not part of the programmed “wiring” of the
brain; therefore, the functions are subject to
modification and adjustment over time.
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Higher-Order Functions
A. Memory
 Stored bits of information gathered through
experience
 There are two types of memories:
 Fact memories – specific bits of information, such as
the color of a stop sign or the smell of perfume
 Skill memories – learned motor behaviors, such as
lighting a match
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Higher-Order Functions
 There are two classes of memories:
 short-term memories
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primary memories
they do not last long, but can be recalled immediately
contain small bits of information
repetition promotes retention
 long-term memories
 last much longer than short-term memories
 short-term memories are converted to long-term memories through
memory consolidation
 two types of long-term memories:
– secondary memories – fade with time and may require considerable
effort to recall
– tertiary memories – memories with you for a lifetime
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Higher-Order Functions
 The amygdaloid body and the hippocampus are
essential to memory consolidation. Damage to the
hippocampus leads to an inability to convert short-term
memories to long-term memories.
 The nucleus basalis, a cerebral nucleus near the
diencephalon, plays an uncertain role in memory storage
and retrieval. Damage to this nucleus is associated with
changes in emotional states, memory, and intellectual
function.
 Most long-term memories are stored in the cerebral
cortex
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Higher-Order Functions
 Memory consolidation at the cellular level involves anatomical and
physiological changes in neurons and synapses. Research on animals
has indicated that the following mechanisms may be involved:
 Increased neurotransmitter release
 Facilitation at synapses
 The formation of additional synaptic connections
 These processes create anatomical changes that facilitate
communication along a specific neural circuit. This facilitated
communication is thought to be the basis of memory storage. A single
circuit that corresponds to a single memory is called a memory
engram.
 Amnesia is the loss of memory as a result of disease or trauma. The
type of memory loss depends on the specific regions of the brain
affected.
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Higher-Order Functions
B. States of Consciousness
 1. conscious
 implies an awareness of and attention to external
events and stimuli
 Examples include: nearly asleep, wide awake, or
high-strung and jumpy
 2. unconscious
 refer to conditions ranging from the deep,
unresponsive stated induced by anesthesia before
major surgery, to deep sleep, to light sleep.
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Higher-Order Functions
 Sleep
 There are two general levels of sleep:
 a. deep sleep
– also called slow wave or non-REM sleep
– your entire body relaxes, and activity at the cerebral cortex is at
a minimum
– heart rate, blood pressure, respiratory rate, and energy
utilization decline by up to 30%
 b. rapid eye movement (REM) sleep
– active dreaming occurs accompanied by changed in blood
pressure and respiratory rate
– become less receptive to outside stimuli
– muscle tone decreases markedly
– eyes move rapidly as dream unfolds
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Higher-Order Functions
 Periods of REM and deep sleep alternate throughout the night. People
spend less than two hours dreaming each night. REM sleep periods
average from 5 to 20 minutes in length over a typical 8 hour sleeping
cycle.
 Awakening from sleep (arousal) is one of the functions of the reticular
formation. It has extensive interconnections with the sensory, motor,
and integrative nuclei and pathways along the brain stem. All of these
interconnections make it the “watchdog”. The reticular activating system
(RAS) is a network in the reticular formation that is most important to
arousal and the maintenance of consciousness.
 The regulation of awake-sleep cycles involves an interplay between
brain stem nuclei that use different neurotransmitters. One group of
nuclei stimulates the RAS (reticular activating system) with
norepinephrine and maintains the awake, alert state. The other group,
which depresses RAS activity with serotonin, promotes deep sleep.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings