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Putting it all together-Neural integration
Muse lecture #16
Ch 15-16
Sensory Information
 Afferent Division of the Nervous System
 Receptors
 Sensory neurons
 Sensory pathways
 Efferent Division of the Nervous System
 Nuclei
 Motor tracts
 Motor neurons
Sensory Information
Figure 15–1 An Overview of Neural Integration.
Sensory Information
 Somatic Nervous System (SNS)
 Motor neurons and pathways that control
skeletal muscles
Sensory Receptors
 Sensation
 The arriving information from these senses
 Perception
 Conscious awareness of a sensation
Sensory Receptors
 Special Senses
 Olfaction (smell)
 Vision (sight)
 Gustation (taste)
 Equilibrium (balance)
 Hearing
Sensory Receptors
 The Detection of Stimuli
 Receptor sensitivity
 Each receptor has a characteristic sensitivity
 Receptive field
 Area is monitored by a single receptor cell
 The larger the receptive field, the more difficult it is
to localize a stimulus
Sensory Receptors
Figure 15–2 Receptors and Receptive Fields
Sensory Receptors
 The Interpretation of Sensory Information
 Arriving stimulus
 Takes many forms:
– physical force (such as pressure)
– dissolved chemical
– sound
– light
Sensory Receptors
 The Interpretation of Sensory Information
 Sensations
 Taste, hearing, equilibrium, and vision provided by
specialized receptor cells
 Communicate with sensory neurons across
chemical synapses
Sensory Receptors
 Adaptation
 Reduction in sensitivity of a constant stimulus
 Your nervous system quickly adapts to stimuli
that are painless and constant example smell
Sensory Receptors
 Adaptation
 Tonic receptors
 Are always active
 Show little peripheral adaptation
 Are slow-adapting receptors
 Remind you of an injury long after the initial
damage has occurred
Sensory Receptors
 Adaptation
 Phasic receptors
 Are normally inactive
 Become active for a short time whenever a change
occurs
 Provide information about the intensity and rate of
change of a stimulus
 Are fast-adapting receptors
Sensory Receptors
 Stimulation of a receptor produces action potentials
along the axon of a sensory neuron
 The frequency and pattern of action potentials
contain information about the strength, duration, and
variation of the stimulus
 Your perception of the nature of that stimulus
depends on the path it takes inside the CNS
Classifying Sensory Receptors
 Exteroceptors provide information about
the external environment
 Proprioceptors report the positions of
skeletal muscles and joints
 Interoceptors monitor visceral organs and
functions
Classifying Sensory Receptors
 Proprioceptors
 Provide a purely somatic sensation
 No proprioceptors in the visceral organs of the
thoracic and abdominopelvic cavities
 You cannot tell where your spleen, appendix, or
pancreas is at the moment
Classifying Sensory Receptors
 General sensory receptors are divided into
four types by the nature of the stimulus that
excites them
 Nociceptors (pain)
 Thermoreceptors (temperature)
 Mechanoreceptors (physical distortion)
 Chemoreceptors (chemical concentration)
Classifying Sensory Receptors
 Nociceptors (also called pain receptors)
 Are common in the superficial portions of the
skin, joint capsules, within the periostea of
bones, and around the walls of blood vessels
 May be sensitive to temperature extremes,
mechanical damage, and dissolved chemicals,
such as chemicals released by injured cells
Figure 15–2
Classifying Sensory Receptors
 Nociceptors
 Are free nerve endings with large receptive
fields
 Branching tips of dendrites
 Not protected by accessory structures
 Can be stimulated by many different stimuli
 Two types of axons: Type A and Type C fibers
Classifying Sensory Receptors
 Nociceptors
 Myelinated Type A fibers
 Carry sensations of fast pain, or prickling pain,
such as that caused by an injection or a deep cut
 Sensations reach the CNS quickly and often
trigger somatic reflexes
 Relayed to the primary sensory cortex and receive
conscious attention
Classifying Sensory Receptors
 Nociceptors
 Type C fibers
 Carry sensations of slow pain, or burning and
aching pain
 Cause a generalized activation of the reticular
formation and thalamus
 You become aware of the pain but only have a
general idea of the area affected
Classifying Sensory Receptors
 Thermoreceptors
 Also called temperature receptors
 Are free nerve endings located in
 The dermis
 Skeletal muscles
 The liver
 The hypothalamus
Classifying Sensory Receptors
 Thermoreceptors
 Temperature sensations
 Conducted along the same pathways that carry
pain sensations
 Sent to:
– the reticular formation
– the thalamus
– the primary sensory cortex (to a lesser extent)
Classifying Sensory Receptors
 Mechanoreceptors
 Sensitive to stimuli that distort their plasma
membranes
 Contain mechanically gated ion channels whose
gates open or close in response to
 Stretching
 Compression
 Twisting
 Other distortions of the membrane
Classifying Sensory Receptors
 Three Classes of Mechanoreceptors
 Tactile receptors
 provide the sensations of touch, pressure,
and vibration:
– touch sensations provide information about
shape or texture
– pressure sensations indicate degree of
mechanical distortion
– vibration sensations indicate pulsing or
oscillating pressure
Classifying Sensory Receptors
 Three Classes of Mechanoreceptors
 Baroreceptors
 Detect pressure changes in the walls of
blood vessels and in portions of the
digestive, reproductive, and urinary tracts
Classifying Sensory Receptors
 Three Classes of Mechanoreceptors
 Proprioceptors
 Monitor the positions of joints and muscles
 The most structurally and functionally
complex of general sensory receptors
Classifying Sensory Receptors
 Mechanoreceptors: Tactile Receptors
 Fine touch and pressure receptors
 Are extremely sensitive
 Have a relatively narrow receptive field
 Provide detailed information about a source of
stimulation, including:
– its exact location, shape, size, texture, movement
Classifying Sensory Receptors
 Mechanoreceptors: Tactile Receptors
 Crude touch and pressure receptors
 Have relatively large receptive fields
 Provide poor localization
 Give little information about the stimulus
Classifying Sensory Receptors
 Six Types of Tactile Receptors in the Skin
 1.
Free nerve endings
 Sensitive to touch and pressure
 Situated between epidermal cells
 Free nerve endings providing touch sensations are tonic
receptors with small receptive fields
Classifying Sensory Receptors
5.
1.
2.
3.
4
Figure 15–3a Tactile Receptors in the Skin.
6
Classifying Sensory Receptors
 Six Types of Tactile Receptors in the Skin
 2. Root hair plexus nerve endings rapid
• 3. Tactile discs tonic
Also called Merkel discs
Fine touch and pressure receptors
Extremely sensitive to tonic receptors
Have very small receptive fields
Figure 15–3b
Classifying Sensory Receptors
Figure 15–3b Tactile Receptors in the Skin.
Classifying Sensory Receptors
 4. Tactile corpuscles: rapid
 Also called Meissner corpuscles
 Perceive sensations of fine touch, pressure, and lowfrequency vibration
 Adapt to stimulation within 1 second after contact
 Most abundant in the eyelids, lips, fingertips, nipples, and
external genitalia
5.
Lamellated corpuscles (Pacinian)
rapid
Sensitive to deep pressure
Fast-adapting receptors
Most sensitive to pulsing or high-frequency vibrating stimuli
Figure 15–3d
Classifying Sensory Receptors
Figure 15–3d Tactile Receptors in the Skin.
Classifying Sensory Receptors
 6 Ruffini corpuscles tonic
 Also sensitive to pressure and distortion of the
skin
 Located in the reticular (deep) dermis
 Tonic receptors that show little if any adaptation
Figure 15–3f
Classifying Sensory Receptors
Figure 15–3f Tactile Receptors in the Skin.
Classifying Sensory Receptors
 Baroreceptors
 Monitor change in pressure
 Consist of free nerve endings that branch
within elastic tissues in wall of distensible
organ (such as a blood vessel)
 Respond immediately to a change in
pressure, but adapt rapidly
Classifying Sensory Receptors
 Proprioceptors
 Monitor
 Position of joints
 Tension in tendons and ligaments
 State of muscular contraction
Classifying Sensory Receptors
 Three Major Groups of Proprioceptors
 Muscle spindles
 Monitor skeletal muscle length
 Trigger stretch reflexes
 Golgi tendon organs
 Located at the junction between skeletal muscle and its tendon
 Stimulated by tension in tendon
 Monitor external tension developed during muscle contraction
 Receptors in joint capsules
 Free nerve endings detect pressure, tension, movement at the joint
Classifying Sensory Receptors
 Chemoreceptors
 Respond only to water-soluble and lipidsoluble substances dissolved in surrounding
fluid
 Receptors exhibit peripheral adaptation over
period of seconds; central adaptation may
also occur
Sensory Pathways
 First-Order Neuron
 Sensory neuron delivers sensations to the CNS
 Cell body of a first-order general sensory neuron is located in dorsal
root ganglion or cranial nerve ganglion
 Second-Order Neuron
 Axon of the sensory neuron synapses on an interneuron in the CNS
 May be located in the spinal cord or brain stem
 Third-Order Neuron
 If the sensation is to reach our awareness, the second-order neuron
synapses on a third-order neuron in the thalamus
Sensory Pathways
 Somatic Sensory Pathways
 Carry sensory information from the skin and
musculature of the body wall, head, neck, and limbs
 Three major somatic sensory pathways
 1 The posterior column pathway
 2 The spinothalamic pathway
 3 The spinocerebellar pathway
Sensory Pathways
1
3
2
Figure 15–4 Sensory Pathways and Ascending Tracts in the Spinal
Cord.
Sensory Pathways
 Somatic Sensory Pathways
 Posterior column pathway
 Carries sensations of highly localized (“fine”)
touch, pressure, vibration, and proprioception
 Spinal tracts involved:
– left and right fasciculus gracilis
– left and right fasciculus cuneatus
Figure 15–5a
Sensory Pathways
 Posterior Column Pathway
 Axons synapse
 On third-order neurons in one of the ventral nuclei
of the thalamus
 Nuclei sort the arriving information according to:
– the nature of the stimulus
– the region of the body involved
Figure 15–5a
Sensory Pathways
 Posterior Column Pathway
 Processing in the thalamus
 Determines whether you perceive a given sensation as fine
touch, as pressure, or as vibration
 Ability to determine stimulus
 Precisely where on the body a specific stimulus originated
depends on the projection of information from the thalamus
to the primary sensory cortex
Figure 15–5a
Sensory Pathways
 Posterior Column Pathway
 Sensory information
 From toes arrives at one end of the primary
sensory cortex
 From the head arrives at the other:
– when neurons in one portion of your primary sensory
cortex are stimulated, you become aware of sensations
originating at a specific location
Figure 15–5a
Sensory Pathways
 Posterior Column Pathway
 Sensory homunculus
 Functional map of the primary sensory cortex
 Distortions occur because area of sensory cortex
devoted to particular body region is not
proportional to region’s size, but to number of
sensory receptors it contains
Sensory Pathways
Figure 15–5a The Posterior Column Pathway.
Sensory Pathways
 The Spinothalamic Pathway
 Provides conscious sensations of poorly localized
(“crude”) touch, pressure, pain, and temperature
 First-order neurons
 Axons of first-order sensory neurons enter spinal cord and
synapse on second-order neurons within posterior gray
horns
Sensory Pathways
 The Spinothalamic Pathway
 Second-order neurons
 Cross to the opposite side of the spinal cord before
ascending
 Ascend within the anterior or lateral spinothalamic
tracts:
– the anterior tracts carry crude touch and pressure
sensations
– the lateral tracts carry pain and temperature sensations
Sensory Pathways
 The Spinothalamic Pathway
 Third-order neurons
 Synapse in ventral nucleus group of the thalamus
 After the sensations have been sorted and
processed, they are relayed to primary sensory
cortex
Sensory Pathways
Figure 15–5b The Spinothalamic Tracts of the Spinothalamic Pathway.
Sensory Pathways
humunculus
Figure 15–5c The Spinothalamic Tracts of the Spinothalamic Pathway.
Sensory Pathways
 Feeling Pain (Lateral Spinothalamic Tract)
 An individual can feel pain in an uninjured part of the
body when pain actually originates at another location
 Strong visceral pain
 Sensations arriving at segment of spinal cord can stimulate
interneurons that are part of spinothalamic pathway
 Activity in interneurons leads to stimulation of primary
sensory cortex, so an individual feels pain in specific part of
body surface:
– also called referred pain
Sensory Pathways
Figure 15–6 Referred Pain.
Sensory Pathways
 The Spinocerebellar Pathway
 Cerebellum receives proprioceptive
information about position of skeletal
muscles, tendons, and joints
Figure 15–7
Sensory Pathways
 The Spinocerebellar Tracts
 The posterior spinocerebellar tracts
 Contain second-order axons that do NOT cross
over to the opposite side of the spinal cord:
– axons reach cerebellar cortex via inferior cerebellar
peduncle of that side
Sensory Pathways
Figure 15–7 The Spinocerebellar Pathway.
Sensory Pathways
Sensory Pathways
 Most somatic sensory information is
relayed to the thalamus for processing
 A small fraction of the arriving information
is projected to the cerebral cortex and
reaches our awareness
Sensory Pathways
 Visceral Sensory Pathways
 Collected by interoceptors monitoring visceral
tissues and organs, primarily within the thoracic and
abdominopelvic cavities
 These interoceptors are not as numerous as in
somatic tissues
 Nociceptors, thermoreceptors, tactile receptors,
baroreceptors, and chemoreceptors
Sensory Pathways
 Visceral Sensory Pathways
 Cranial Nerves V, VII, IX, and X
 Carry visceral sensory information from mouth,
palate, pharynx, larynx, trachea, esophagus, and
associated vessels and glands
Sensory Pathways
 Visceral Sensory Pathways
 Solitary nucleus
 Large nucleus in the medulla oblongata
 Major processing and sorting center for visceral
sensory information
 Extensive connections with the various
cardiovascular and respiratory centers, reticular
formation
Somatic Motor Pathways
 SNS, or the somatic motor system, controls
contractions of skeletal muscles (discussed
next)
 ANS, or the visceral motor system, controls
visceral effectors, such as smooth muscle,
cardiac muscle, and glands (Ch. 16)
Somatic Motor Pathways
 Always involve at least two motor neurons
 1 Upper motor neuron
 Cell body lies in a CNS processing center
 Synapses on the lower motor neuron
 Innervates a single motor unit in a skeletal muscle:
– activity in upper motor neuron may facilitate or inhibit
lower motor neuron
Somatic Motor Pathways
 2 Lower motor neuron
 Cell body lies in a nucleus of the brain stem or
spinal cord
 Triggers a contraction in innervated muscle:
– only axon of lower motor neuron extends outside CNS
– destruction of or damage to lower motor neuron
eliminates voluntary and reflex control over innervated
motor unit
Somatic Motor Pathways
 Conscious and Subconscious Motor
Commands
 Control skeletal muscles by traveling over
three integrated motor pathways
 Corticospinal pathway
 Medial pathway
 Lateral pathway
Somatic Motor Pathways
Figure 15–8 Descending (Motor) Tracts in the Spinal Cord.
Somatic Motor Pathways
 The Corticospinal Pathway
 Sometimes called the pyramidal system
 Provides voluntary control over skeletal muscles
 System begins at pyramidal cells of primary motor cortex
 Axons of these upper motor neurons descend into brain stem
and spinal cord to synapse on lower motor neurons that
control skeletal muscles
 Contains three pairs of descending tracts
 Corticobulbar tracts
 Lateral corticospinal tracts
 Anterior corticospinal tracts
Somatic Motor Pathways
 The Corticospinal Pathway
 Corticobulbar tracts
 Provide conscious control over skeletal muscles
that move the eye, jaw, face, and some muscles of
neck and pharynx
 Innervate motor centers of medial and lateral
pathways
Somatic Motor Pathways
 The Corticospinal Pathway
 Corticospinal tracts
 As they descend, lateral corticospinal tracts are visible
along the ventral surface of medulla oblongata as pair of
thick bands, the pyramids
 At spinal segment it targets, an axon in anterior
corticospinal tract crosses over to opposite side of spinal
cord in anterior white commissure before synapsing on
lower motor neurons in anterior gray horns
Somatic Motor Pathways
 The Corticospinal Pathway
 Motor homunculus
 Primary motor cortex corresponds point by point with specific
regions of the body
 Cortical areas have been mapped out in diagrammatic form
 Homunculus provides indication of degree of fine motor
control available:
– hands, face, and tongue, which are capable of varied and
complex movements, appear very large, while trunk is relatively
small
– these proportions are similar to the sensory homunculus
Somatic Motor Pathways
Figure 15–9 The Corticospinal Pathway.
Somatic Motor Pathways
 The Medial and Lateral Pathways
 Several centers in cerebrum, diencephalon, and brain
stem may issue somatic motor commands as result of
processing performed at subconscious level
 These nuclei and tracts are grouped by their primary
functions
 Components of medial pathway help control gross
movements of trunk and proximal limb muscles
 Components of lateral pathway help control distal limb
muscles that perform more precise movements
Somatic Motor Pathways
 The Medial Pathway
 Primarily concerned with control of muscle tone and
gross movements of neck, trunk, and proximal limb
muscles
 Upper motor neurons of medial pathway are located
in
 Vestibular nuclei
 Superior and inferior colliculi
 Reticular formation
Somatic Motor Pathways
 The Medial Pathway
 Vestibular nuclei
 Receive information over the vestibulocochlear
nerve (VIII) from receptors in inner ear that monitor
position and movement of the head:
– primary goal is to maintain posture and balance
– descending fibers of spinal cord constitute
vestibulospinal tracts
Somatic Motor Pathways
 The Medial Pathway
 Superior and inferior colliculi
 Are located in the roof of the mesencephalon, or the tectum
 Colliculi receive visual (superior) and auditory (inferior)
sensations
 Axons of upper motor neurons in colliculi descend in
tectospinal tracts
 These axons cross to opposite side, before descending to
synapse on lower motor neurons in brain stem or spinal cord
Somatic Motor Pathways
 The Medial Pathway
 Reticular formation
 Loosely organized network of neurons that extends
throughout brain stem
 Axons of upper motor neurons in reticular
formation descend into reticulospinal tracts
without crossing to opposite side
Somatic Motor Pathways
 The Lateral Pathway
 Primarily concerned with control of muscle
tone and more precise movements of distal
parts of limbs:
 axons of upper motor neurons in red nuclei
cross to opposite side of brain and descend
into spinal cord in rubrospinal tracts
Somatic Motor Pathways
Somatic Motor Pathways
Somatic Motor Pathways
 The Basal Nuclei and Cerebellum
 Responsible for coordination and feedback
control over muscle contractions, whether
contractions are consciously or
subconsciously directed
Somatic Motor Pathways
 The Basal Nuclei
 Provide background patterns of movement involved in
voluntary motor activities
 Some axons extend to the premotor cortex, the motor
association area that directs activities of the primary motor
cortex:
– alters the pattern of instructions carried by the corticospinal
tracts
 Other axons alter the excitatory or inhibitory output of the
reticulospinal tracts
Somatic Motor Pathways
 The Cerebellum
 Monitors
 Proprioceptive (position) sensations
 Visual information from the eyes
 Vestibular (balance) sensations from inner ear as
movements are under way
Somatic Motor Pathways
 Levels of Processing and Motor Control
 All sensory and motor pathways involve a series of synapses,
one after the other
 General pattern
 Spinal and cranial reflexes provide rapid, involuntary,
preprogrammed responses that preserve homeostasis over short
term
 Cranial and spinal reflexes
 Control the most basic motor activities
Somatic Motor Pathways
 Levels of Processing and Motor Control
 Integrative centers in the brain
 Perform more elaborate processing
 As we move from medulla oblongata to cerebral cortex,
motor patterns become increasingly complex and variable
 Primary motor cortex
 Most complex and variable motor activities are directed by
primary motor cortex of cerebral hemispheres
Somatic Motor Pathways
 Neurons of the primary motor cortex innervate
motor neurons in the brain and spinal cord
responsible for stimulating skeletal muscles
 Higher centers in the brain can suppress or
facilitate reflex responses
 Reflexes can complement or increase the
complexity of voluntary movements
An Introduction to the ANS
 Somatic Nervous System (SNS)
 Operates under conscious control
 Seldom affects long-term survival
 SNS controls skeletal muscles
 Autonomic Nervous System (ANS)
 Operates without conscious instruction
 ANS controls visceral effectors
 Coordinates system functions: cardiovascular, respiratory,
digestive, urinary, reproductive
Autonomic Nervous System
 Organization of the ANS
 Integrative centers
 For autonomic activity in hypothalamus
 Neurons comparable to upper motor neurons in
SNS
Autonomic Nervous System
 Organization of the ANS
 Visceral motor neurons
 In brain stem and spinal cord, are known as
preganglionic neurons
 Preganglionic fibers:
– axons of preganglionic neurons
– leave CNS and synapse on ganglionic neurons
Autonomic Nervous System
 Visceral Motor Neurons (cont’d)
 Autonomic ganglia
 Contain many ganglionic neurons
 Ganglionic neurons innervate visceral effectors:
– such as cardiac muscle, smooth muscle, glands, and
adipose tissue
 Postganglionic fibers:
– axons of ganglionic neurons
Autonomic Nervous System
Figure 16-2a The Organization of the Somatic and Nervous Systems.
Autonomic Nervous System
Figure 16-2b The Organization of the Autonomic Nervous Systems.
Divisions of the ANS
 The autonomic nervous system
 Operates largely outside our awareness
 Has two divisions
 Sympathetic division
gas pedal
– increases alertness, metabolic rate, and muscular
abilities
fight or flight
 Parasympathetic division
brake
– reduces metabolic rate and promotes digestion
Rest and digest
Divisions of the ANS
 Two divisions may work independently
 Some structures innervated by only one
division
 Two divisions may work together
 Each controlling one stage of a complex
process
Divisions of the ANS
 Sympathetic Division
 Preganglionic fibers (thoracic and superior lumbar;
thoracolumbar) synapse in ganglia near spinal cord
 Preganglionic fibers are short
 Postganglionic fibers are long
 Prepares body for crisis, producing a “fight or flight”
response
 Stimulates tissue metabolism
 Increases alertness
Divisions of the ANS
 Seven Responses to Increased Sympathetic Activity
 Heightened mental alertness
 Increased metabolic rate
 Reduced digestive and urinary functions
 Energy reserves activated
 Increased respiratory rate and respiratory passageways dilate
 Increased heart rate and blood pressure
 Sweat glands activated
Divisions of the ANS
 Parasympathetic Division
 Preganglionic fibers originate in brain stem and sacral
segments of spinal cord; craniosacral
 Synapse in ganglia close to (or within) target organs
 Preganglionic fibers are long
 Postganglionic fibers are short
Divisions of the ANS
 Parasympathetic Division
 Rest and repose
 Parasympathetic division stimulates visceral activity
 Conserves energy and promotes sedentary activities
 Decreased metabolic rate, heart rate, and blood pressure
 Increased salivary and digestive glands secretion
 Increased motility and blood flow in digestive tract
 Urination and defecation stimulation
Divisions of the ANS
 Enteric Nervous System (ENS)
 Third division of ANS
 Extensive network in digestive tract walls
 Complex visceral reflexes coordinated locally
 Roughly 100 million neurons
 All neurotransmitters are found in the brain
The Sympathetic Division
 Preganglionic neurons located between
segments T1 and L2 of spinal cord
 Ganglionic neurons in ganglia near vertebral
column
 Cell bodies of preganglionic neurons in lateral
gray horns
 Axons enter ventral roots of segments
The Sympathetic Division
Figure 16–3 The Organization of the Sympathetic Division of the ANS.
The Sympathetic Division
 Ganglionic Neurons
 Occur in three locations
 Sympathetic chain ganglia
 Collateral ganglia
 Suprarenal medullae
The Sympathetic Division
Figure 16–4a Sites of Ganglia in Sympathetic Pathways
The Sympathetic Division
Figure 16–4b Sites of Ganglia in Sympathetic Pathways.
The Sympathetic Division
Figure 16–4c Sites of Ganglia in Sympathetic Pathways.
The Sympathetic Division
 Fibers in Sympathetic Division
 Preganglionic fibers
 Are relatively short
 Ganglia located near spinal cord
 Postganglionic fibers
 Are relatively long, except at suprarenal medullae
Various Sympathetic Neurotransmitters
 Sympathetic Stimulation and the Release
of ACh and NO
 Cholinergic (ACh) sympathetic terminals
 Innervate sweat glands of skin and blood vessels
of skeletal muscles and brain
 Stimulate sweat gland secretion and dilate blood
vessels
Various Sympathetic Neurotransmitters
 Sympathetic Stimulation and the Release
of ACh and NO
 Nitroxidergic synapses
 Release nitric oxide (NO) as neurotransmitter
 Neurons innervate smooth muscles in walls of
blood vessels in skeletal muscles and the brain
 Produce vasodilation and increased blood flow
The Parasympathetic Division
 Autonomic Nuclei
 Are contained in the mesencephalon, pons,
and medulla oblongata
 associated with cranial nerves III, VII, IX, X
 In lateral gray horns of spinal segments S2–S4
Organization and Anatomy of the
Parasympathetic Division
Figure 16–7 The Organization of the Parasympathetic Division of the
ANS.
Organization and Anatomy of the
Parasympathetic Division
Figure 16–8 The Distribution of Parasympathetic Innervation.
Organization and Anatomy of the
Parasympathetic Division
Figure 16–8 The Distribution of Parasympathetic Innervation.
The Parasympathetic Division
 Parasympathetic Activation
 Centers on relaxation, food processing, and
energy absorption
 Localized effects, last a few seconds at most
The Parasympathetic Division
 Major effects of parasympathetic division include
 Constriction of pupils
 Restricts light entering eyes
 Secretion by digestive glands
 Exocrine and endocrine
 Secretion of hormones
 Nutrient absorption and utilization
 Changes in blood flow and glandular activity
 Associated with sexual arousal
Parasympathetic Neurons Release ACh
 Neuromuscular and Neuroglandular Junctions
 All release ACh as neurotransmitter
 Small, with narrow synaptic clefts
 Effects of stimulation are short lived
 Inactivated by AChE at synapse
 ACh is also inactivated by pseudocholinesterase (tissue
cholinesterase) in surrounding tissues
Parasympathetic Neurons Release ACh
 Membrane Receptors and Responses
 Nicotinic receptors
 On surfaces of ganglion cells (sympathetic and
parasympathetic):
– exposure to ACh causes excitation of ganglionic neuron
or muscle fiber
Parasympathetic Neurons Release ACh
Dual Innervation
 Sympathetic
 Widespread impact
 Reaches organs and tissues throughout body
 Parasympathetic
 Innervates only specific visceral structures
 Most vital organs receive instructions from both
sympathetic and parasympathetic divisions
 Two divisions commonly have opposing effects
Dual Innervation
 Anatomy of Dual Innervation
 Parasympathetic postganglionic fibers
accompany cranial nerves to peripheral
destinations
 Sympathetic innervation reaches same
structures by traveling directly from superior
cervical ganglia of sympathetic chain
Dual Innervation
Figure 16–9 Summary: The Anatomical Differences between the
Sympathetic and Parasympathetic Divisions.
Anatomy of Dual Innervation
Figure 16–10 The Autonomic Plexuses.
Dual Innervation
 The heart receives dual innervation
 Two divisions have opposing effects
 Parasympathetic division
 Acetylcholine released by postganglionic fibers slows heart
rate
 Sympathetic division
 NE released by varicosities accelerates heart rate
 Balance between two divisions
 Autonomic tone is present
 Releases small amounts of both neurotransmitters
continuously
Dual Innervation
 The heart receives dual innervation
 Parasympathetic innervation dominates under
resting conditions
 Crisis accelerates heart rate by
 Stimulation of sympathetic innervation
 Inhibition of parasympathetic innervation
Visceral Reflexes Regulate Autonomic Function
Figure 16–12 A Comparison of Somatic and Autonomic Function.
Higher-Order Functions
 Require the cerebral cortex
 Involve conscious and unconscious
information processing
 Not part of programmed “wiring” of brain
 Can adjust over time
Higher-Order Functions
 Memory
 Fact memories
 Are specific bits of information
 Skill memories
 Learned motor behaviors
 Incorporated at unconscious level with repetition
 Programmed behaviors stored in appropriate area of brain
stem
 Complex are stored and involve motor patterns in the basal
nuclei, cerebral cortex, and cerebellum
Higher-Order Functions
 Memory
 Short–term memories
 Information that can be recalled immediately
 Contain small bits of information
 Primary memories
 Long-term memories
 Memory consolidation: conversion from short-term to longterm memory:
– secondary memories fade and require effort to recall
– tertiary memories are with you for life
Higher-Order Functions
Figure 16–13 Memory Storage.
The limbic system
Higher-Order Functions
 Brain Regions Involved in Memory Consolidation
and Access
 Amygdaloid body and hippocampus
 Nucleus basalis
 Cerebral cortex
memory
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Higher-Order Functions
 Amygdaloid body and hippocampus
 Are essential to memory consolidation
 Damage may cause
 Inability to convert short-term memories to new
long-term memories
 Existing long-term memories remain intact and
accessible
memory
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Higher-Order Functions
 Nucleus Basalis
 Cerebral nucleus near diencephalon
 Plays uncertain role in memory storage and retrieval
 Tracts connect with hippocampus, amygdaloid body,
and cerebral cortex
 Damage changes emotional states, memory, and
intellectual functions
Higher-Order Functions
 Cerebral cortex
 Stores long-term memories
 Conscious motor and sensory memories referred to
association areas
 Occipital and temporal lobes
 Special portions crucial to memories of faces, voices, and
words
 A specific neuron may be activated by combination of
sensory stimuli associated with particular individual; called
“grandmother cells”
Higher-Order Functions
 Cerebral cortex
 Visual association area
 Auditory association area
 Speech center
 Frontal lobes
 Related information stored in other locations
 If storage area is damaged, memory will be incomplete
Higher-Order Functions
 Cellular Mechanisms of Memory Formation and
Storage
 Involves anatomical and physiological
changes in neurons and synapses
 Increased neurotransmitter release
 Facilitation at synapses
 Formation of additional synaptic connections
Higher-Order Functions
 Increased Neurotransmitter Release
 Frequently active synapse increases the
amount of neurotransmitter it stores
 Releases more on each stimulation
 The more neurotransmitter released, the
greater effect on postsynaptic neuron
Higher-Order Functions
 Facilitation at Synapses
 Neural circuit repeatedly activated
 Synaptic terminals begin continuously releasing
neurotransmitter
 Neurotransmitter binds to receptors on postsynaptic
membrane
 Produces graded depolarization
 Brings membrane closer to threshold
 Facilitation results affect all neurons in circuit
Higher-Order Functions
 Formation of Additional Synaptic Connections
 Neurons repeatedly communicating
 Axon tip branches and forms additional synapses on
postsynaptic neuron
 Presynaptic neuron has greater effect on
transmembrane potential of postsynaptic neuron
Higher-Order Functions
 Cellular Mechanisms of Memory Formation and
Storage
 Basis of memory storage
 Processes create anatomical changes
 Facilitate communication along specific neural circuit
 Memory Engram
 Single circuit corresponds to single memory
 Forms as result of experience and repetition
Higher-Order Functions
 Cellular Mechanisms of Memory Formation and
Storage
 Efficient conversion of short-term memory
 Takes at least 1 hour
 Repetition crucial
 Factors of conversion
 Nature, intensity, and frequency of original stimulus
 Strong, repeated, and exceedingly pleasant or unpleasant
events likely converted to long-term memories
Higher-Order Functions
 Cellular Mechanisms of Memory Formation and
Storage
 Drugs stimulate CNS
 Caffeine and nicotine are examples:
– enhance memory consolidation through facilitation
 NMDA (N-methyl D-aspartate) Receptors:
–
–
–
–
–
linked to consolidation
chemically gated calcium channels
activated by neurotransmitter glycine
gates open, calcium enters cell
blocking NMDA receptors in hippocampus prevents longterm memory formation
Higher-Order Functions
 States of Consciousness
 Many gradations of states
 Degree of wakefulness indicates level of
ongoing CNS activity
 When abnormal or depressed, state of
wakefulness is affected
Higher-Order Functions
 States of Consciousness
 Deep sleep
 Also called slow-wave sleep
 Entire body relaxes
 Cerebral cortex activity minimal
 Heart rate, blood pressure, respiratory rate, and
energy utilization decline up to 30%
Higher-Order Functions
 States of Consciousness
 Rapid eye movement (REM) sleep
 Active dreaming occurs
 Changes in blood pressure and respiratory rate
 Less receptive to outside stimuli than in deep sleep
 Muscle tone decreases markedly
 Intense inhibition of somatic motor neurons
 Eyes move rapidly as dream events unfold
Higher-Order Functions
 States of Consciousness
 Nighttime sleep pattern
 Alternates between levels
 Begins in deep sleep
 REM periods average 5 minutes in length;
increase to 20 minutes over 8 hours
Higher-Order Functions
 Sleep
 Has important impact on CNS
 Produces only minor changes in physiological
activities of organs and systems
 Protein synthesis in neurons increases during sleep
 Extended periods without sleep lead to disturbances
in mental function
 25% of U.S. population experiences sleep disorders
Higher-Order Functions
Figure 16–14 Levels of Sleep.
Higher-Order Functions
 States of Consciousness
 Arousal and the reticular activating system (RAS)
 Awakening from sleep
 Function of reticular formation:
– extensive interconnections with sensory, motor, integrative nuclei,
and pathways along brain stem
 Determined by complex interactions between reticular formation
and cerebral cortex
Higher-Order Functions
 Reticular Activating System (RAS)
 Important brain stem component
 Diffuse network in reticular formation
 Extends from medulla oblongata to mesencephalon
 Output of RAS projects to thalamic nuclei that
influence large areas of cerebral cortex
 When RAS inactive, so is cerebral cortex
 Stimulation of RAS produces widespread activation
of cerebral cortex
Higher-Order Functions
 Arousal and the Reticular Activating
System
 Ending sleep
 Any stimulus activates reticular formation and RAS
 Arousal occurs rapidly
 Effects of single stimulation of RAS last less than a
minute
Higher-Order Functions
 Arousal and the Reticular Activating System
 Maintaining consciousness
 Activity in cerebral cortex, basal nuclei, and sensory and
motor pathways continue to stimulate RAS:
– after many hours, reticular formation becomes less responsive
to stimulation
– individual becomes less alert and more lethargic
– neural fatigue reduces RAS activity
Higher-Order Functions
 Arousal and the Reticular Activating System
 Regulation of awake–asleep cycles
 Involves interplay between brain stem nuclei that use
different neurotransmitters
 Group of nuclei stimulates RAS with NE and maintains
awake, alert state
 Other group promotes deep sleep by depressing RAS activity
with serotonin
 “Dueling” nuclei located in brain stem
Higher-Order Functions
Figure 16–15 The Reticular Activating System.
Brain Chemistry
 Huntington Disease
 Destruction of ACh-secreting and GABA-secreting
neurons in basal nuclei
 Symptoms appear as basal nuclei and frontal lobes
slowly degenerate
 Difficulty controlling movements
 Intellectual abilities gradually decline
Brain Chemistry
 Lysergic Acid Diethylamide (LSD)
 Powerful hallucinogenic drug
 Activates serotonin receptors in brain stem,
hypothalamus, and limbic system
Brain Chemistry
 Serotonin
 Compounds that enhance effects also
produce hallucinations (LSD)
 Compounds that inhibit or block action cause
severe depression and anxiety
 Variations in levels affect sensory
interpretation and emotional states
Brain Chemistry
 Serotonin
 Fluoxetine (Prozac)
 Slows removal of serotonin at synapses
 Increases serotonin concentrations at postsynaptic
membrane
 Classified as selective serotonin reuptake
inhibitors (SSRIs)
 Other SSRIs:
– Celexa, Luvox, Paxil, and Zoloft
Brain Chemistry
 Parkinson Disease
 Inadequate dopamine production causes motor
problems
 Dopamine
 Secretion stimulated by amphetamines, or “speed”
 Large doses can produce symptoms resembling
schizophrenia
 Important in nuclei that control intentional movements
 Important in other centers of diencephalon and cerebrum
Nervous System Integration
 Neural Tissue
 Extremely delicate
 Extracellular environment must maintain
homeostatic limits
 If regulatory mechanisms break down,
neurological disorders appear
Nervous System Integration
Figure 16–16 Functional Relationships between the Nervous System and Other
Systems.
Nervous System Integration
Figure 16–16 Functional Relationships between the Nervous System and Other
Systems.
Nervous System Integration
Figure 16–16 Functional Relationships between the Nervous System and Other
Systems.