Title: Chapter 15: Neural Integration I: Sensory Pathways and the Somatic Nervous System
1Chapter 15 Neural Integration I Sensory
Pathways and the Somatic Nervous System
2Neural Integration
3Afferent Division of the Nervous System
- Receptors
- Sensory neurons
- Sensory pathways
4Afferent Division
- Sensory receptors ? sensory pathway ?
- Somatic Sensory info
- Sensory cortex of cerebrum
- Cerebellum
- Visceral Sensory info
- Reflex centers in brainstem
- Reflex centers in diencephalon
5Sensory Receptors
- Specialized cells that monitor specific
conditions in the body or external environment - General Senses
- Temp, pain, touch, pressure, vibration,
proprioception - Simple receptors located anywhere on body
- Special Senses
- Are located in sense organs such as the eye or
ear - Olfaction, vision, gustation, hearing,
equilibrium - Complex receptors located in specialized sense
organs
6Sensory Receptors
- Sensation the sense info action potentials
- Taste, hearing, equilibrium, and vision provided
by specialized receptor cells - Communicate with sensory neurons across chemical
synapses - Perception conscious awareness of sensation
7Sensory Receptors
- Transduction conversion of environmental
stimulus into action potential by sensory
receptor - Action potential
- When stimulated, a receptor passes information to
the CNS in the form of action potentials along
the axon of a sensory neuron - Receptors specific for particular type of
stimulus - Specificity is due to structure of receptor
- Simplest receptors are dendrites (free nerve
endings), least specific
8Free Nerve Endings
- Branching tips of dendrites
- Not protected by accessory structures
- Can be stimulated by many different stimuli
9Sensory Receptors
- Receptive field
- area monitored by single receptor (e.g. touch
arm vs. fingertip) - Area is monitored by a single receptor cell
- The larger the receptive field, the more
difficult it is to localize a stimulus
10Sensory Receptors
- Labeled line
- Link between receptor and processing site in CNS
- Stimulation anywhere on labeled line will produce
the same perception (e.g. phantom limb) - Stimulus -gt receptor -gt transduction -gt action
potential -gt sensation -gt-gt CNS perception
11Sensory Pathways
- Deliver somatic and visceral sensory information
to their final destinations inside the CNS using - nerves
- nuclei
- tracts
12Sensory Receptors
- Tonic Receptors
- Always active
- Signal at different rate when stimulated
- Monitor background levels
- Phasic Receptors
- Activated by stimulus
- Become active for a short time whenever a change
occurs - Monitor intensity and rate of change of stimulus
13Sensory Receptors
- Adaptation
- Reduced sensitivity to a constant stimulus
- Peripheral Adaptation
- Reduction in receptor activity
- Phasic ? fast adapting
- Tonic ? slow or non adapting
- Remind you of an injury long after the initial
damage has occurred - Central Adaptation
- Inhibition of nuclei along labeled line
- Not all pathways will adapt
14Four types of General Sensory Receptors
- Pain nociceptor
- Temperature thermoreceptor
- Physical mechanoreceptor
- Chemicals chemoreceptors
- All can be found in both somatic (exteroceptors)
and visceral (interoceptors) locations except - Proprioceptors (a mechanoreceptor) are somatic
only - report the positions of skeletal muscles and
joints
151. Pain Receptors Nociceptors
- Detect Pain
- Are common in the
- superficial portions of the skin
- joint capsules
- within the periosteum of bones
- around the walls of blood vessels
- Rare in deep tissue and visceral organs
- Consist of free nerve endings with large receptor
fields
Figure 152
161. Pain Receptors Nociceptors
- Mode of Action
- Injured cells release arachidonic acid
- Arachidonic acid is converted into prostaglandins
by the interstitial enzyme cyclo-oxygenase - Prostaglandins activate nociceptors
- Many pain medications like aspirin function to
inhibit cyclo-oxygenase
171. Pain Receptors Nociceptors
- Once transduced pain sensations are carried on
either type A and type C fibers/axons - Type A
- Fast pain stab or cut triggers defensive
reflexes - Type C
- Slow pain aching pain
- Tonic receptors with no peripheral adaptation
- Pain levels are modulated by endorphins which
inhibit CNS function
182. Thermoreceptors
- Detect temperature
- Found in skin, skeletal muscle, liver, and
hypothalamus - Consist of free nerve endings
- Phasic receptors that adapt easily
193. Mechanoreceptors
- Detect membrane distortion
- Three receptor types
- Tactile Receptors
- Proprioceptors
- Baroreceptors
203. Mechanoreceptors
- Tactile Receptors
- Detect touch, pressure and vibration on skin
- Free nerve endings
- Detect touch on skin
- Tonic receptors with small receptor fields
- Root hair plexus nerve endings
- Detect hair movement
- Phasic receptors, adapt rapidly
- Tactile discs/Merkels discs
- Detect fine touch
- Extremely sensitive
- Whole cell tonic receptors
213. Mechanoreceptors
- Tactile Receptors
- Tactile corpuscles/Meissners corpuscles
- Detect fine touch and vibration
- Larger receptor structure
- Phasic receptors, adapt rapidly
- Lamellated corpuscles/Pacinian corpuscles
- Detect deep pressure
- Larger multi-layer receptors
- Phasic receptor, adapt rapidly
- Ruffini corpuscles
- Detect pressure and distortion
- Large tonic receptors, no adaptation
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233. Mechanoreceptors
- Proprioceptors
- Detect positions of joints and muscles
- Tonic receptors, do not adapt, complex
- Muscle spindles
- Modified skeletal muscle cell
- Monitor skeletal muscle length
- Golgi tendon organs
- Dendrites around collagen fibers at the
muscle-tendon junction - Monitor skeletal muscle tension
- Joint capsule receptors
- - Monitor pressure, tension and movement in the
joint
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253. Mechanoreceptors
- Baroreceptors
- Detect pressure changes
- Found in elastic tissue of blood vessels and
organs of digestive, reproductive and urinary
tracts - Consists of free nerve endings
- Phasic receptors, adapt rapidly
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274. Chemoreceptors
- Detect change in concentration of specific
chemicals or compounds - E.g. pH, CO2
- Found in respiratory centers of the brain and in
large arteries - Phasic receptors, adapt rapidly
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29KEY CONCEPT
- Stimulation of a receptor produces action
potentials along the axon of a sensory neuron - The frequency and pattern of action potentials
contains 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
30Somatic Sensory Pathways
- Carry sensory information from the skin and
musculature of the body wall, head, neck, and
limbs
31Somatic Sensory Pathways
- Consist of two or three neurons
- First Order Neuron
- Sensory neuron
- Connects from receptor to CNS
- Cell body is in dorsal root ganglion/cranial
nerve ganglion - Second Order Neuron
- Interneuron (stimulated by first order)
- Located in spinal cord or brain stem
- Subconscious processing of info
- Third Order Neuron
- Located in thalamus
- Relays info to primary somatosensory cortex of
cerebrum for conscious awareness (perception)
32- Only 1 of somatic sensory info reaches cerebrum
(major changes only, background in filtered) - LSD interferes with sensory damping/filtering
sensory overload - All sensory info undergoes decussation in spine
before reaching target in CNS
333 Major Somatic Sensory Pathways
Figure 154
34Posterior Column Pathway
- Carries sensations of highly localized (fine)
touch, pressure, vibration, and proprioception
Figure 155a
35Visceral Sensory Pathways
- Interoceptors transmit info to solitary nucleus
of medulla oblongata for relay to visceral
centers in brainstem and diencephalon - No perception
- Two neurons 1st and 2nd order
36Efferent Division
- Conscious and subconscious motor centers in brain
-gt motor pathways -gt - Somatic Nervous System ? skeletal muscle
- Autonomic Nervous System ? visceral effectors
- - Smooth and cardiac muscle, glands, and adipose
37Somatic Nervous System
- Motor control of skeletal muscle
- Consists of two neurons
- Upper motor neuron
- Has soma in CNS processing center
- Primary motor cortex of cerebrum
- - voluntary control
- Cerebrum, diencephalon, and brain stem
- - subconscious controlreflex
- Basal nuclei of cerebrum and cerebellum
- - coordination, balance, fine tuning
- Lower motor neuron
- Soma in brain stem or spinal cord
- Links to skeletal muscle motor unit
38Motor Homunculus
39Sensory HomunculusFunctional map of the primary
sensory cortex
Figure 155a, b
40Processing in the Thalamus
- Determines whether you perceive a given sensation
as fine touch, as pressure, or as vibration
41Motor Related Disorder
- Parkinsons Disease
- Jittery movements lack of fine tuning of motor
- Results from degeneration of dopamine neurons of
substantia nigra - Inhibits basal nuclei
- Overactive basal nuclei ticks
- Amylotrophic Lateral Sclerosis
- Degeneration of motor neurons in CNS
- Causes muscle atrophy and death
42Motor Related Disorder
- 3. Epilepsy
- 1/25 people
- Wide range in condition
- Absence seizures (blank) to grand mal seizures
(convulsions, unconscious) - Uncontrolled/chaotic neuron activity in brain
blocks normal messages
43When the nociceptors in your hand are stimulated,
what sensation do you perceive?
- pain
- heat
- vibration
- pressure
44What would happen to you if the information from
proprioceptors in your legs were blocked from
reaching the CNS?
- no pain sensations from the legs
- uncontrolled blood pressure in the legs
- uncoordinated movements and inability to walk
- no tactile sensations in the legs
45Chapter 16 Neural Integration II The
Autonomic Nervous System and Higher-Order
Functions
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47Autonomic Nervous System (ANS)
- Operates without conscious instruction
- Coordinates systems functions
- cardiovascular
- respiratory
- digestive
- urinary
- reproductive
48Autonomic Nervous System
- Motor control of visceral effectors
- Involves three neurons
- Visceral motor nuclei in hypothalamus to
autonomic nuclei in CNS - Autonomic nuclei to autonomic ganglia in PNS
- Autonomic ganglia to visceral effector
- Nuclei in CNS, a center with a visible
boundary - Ganglia in PNS, collection of somas together
in one place
49Autonomic Nervous System
50- Two subdivisions
- Sympathetic fight or flight
- Parasympathetic rest and digest
- Typically oppose each other on same effector
- Some effectors innervated by only one
- Blood vessels/sweat glands gt sympathetic only
- Smooth muscle of eye gt parasympathetic only
51Sympathetic Division
- Prepares body for heightened somatic activity
- Ganglia
- Located near spinal cord
- Adrenal Medulla
- Center of adrenal gland (above kidney)
- Releases epinephrine and norepinephrine as
hormones into blood to control effectors body
wide at one (endocrine function)
52Sympathetic Division
- Sympathetic Activation Results
- Increased alertness
- Insensitivity to pain
- Elevation in blood pressure, respiratory rate
- Elevation in muscle tone
- Mobilization of energy reserves
53Sympathetic Division Neurotransmitter
- Preganglionic Neurons release acetycholine
- (cholinergic synapse) ? EPSP on ganglionic
neuron - - directly open ion channel
- - fast acting, short lived
54Sympathetic Division Neurotransmitter
- Ganglionic neurons/postganglionic fibers release
norepinephine at effectors (adrenergic synapse) - NE and E from adrenal medulla hormones
- Result depends on type of receptor
- Alpha1 and beta1 receptors
- - excititory/stimulatory to effector
- Alpha2 and beta2 receptors
- Inhibitory
- beta-blockers block beta1 receptors
- G protein ? second messengers
- Slow acting but long lasting
55Parasympathetic Division
- Stimulates visceral activity
- Maintains homeostasis
- Ganglia located in or near effector
- Vagus nerve carries 75 of parasympathetic
innervations
56Parasympathetic Division
- Parasympathetic activations results
- Constriction of pupils
- Secretion by digestive glands
- Secretion of hormones for nutrient uptake
- Sexual arousal
- Activation of digestive tract
- Defecation and urination
- Constriction of respiratory pathways
- Reduction in heart rate
57Parasympathetic DivisionNeurotransmitters
- All release Ach all cholinergic synapses
- Effects quick, localized, short-lived
- Type of effect depends on receptor
- Nicotonic receptor
- - Excititory effect on target
- Muscarinic receptor
- - Inhibitory or excititory, depends on target cell
58How many motor neurons are required to conduct an
action potential from the spinal cord to smooth
muscles in the wall of the intestine?
59While out for a brisk walk, Julie is suddenly
confronted by an angry dog. Which division of
the autonomic nervous system is responsible for
the physiological changes that occur in Julie as
she turns and runs?
- parasympathetic division
- somatic nervous system
- enteric nervous system
- sympathetic division
60On the basis of anatomy, how could you
distinguish the sympathetic division from the
parasympathetic division of the autonomic nervous
system?
- origin of preganglionic fibers
- number of preganglionic fibers
- placement of ganglia
- both 1 and 3 are correct
61How would a drug that stimulates acetylcholine
receptors affect the sympathetic nervous system?
- complete shut-down of sympathetic activity
- decreased sympathetic activity
- uncontrolled sympathetic activity
- increased sympathetic activity
62An individual with high blood pressure is given a
medication that blocks beta receptors. How could
this medication help correct that persons
condition?
- aids sympathetic stimulation
- decreases blood volume
- prevents sympathetic stimulation
- none of the above
63Which nerve is responsible for the
parasympathetic innervation of the lungs, heart,
stomach, liver, pancreas, and parts of the small
and large intestines?
- cranial nerve IX
- splanchic nerve
- vagus nerve
- pelvic nerve
64What effect would the loss of sympathetic tone
have on blood flow to a tissue?
- Blood flow would decrease.
- Blood flow would be redirected to heart, lungs
and brain. - Blood flow would increase.
- Blood flow would become erratic.
65What physiological changes would you expect in a
patient who is about to undergo a root canal and
is quite anxious about the procedure?
- change in motility of digestive tract
- increased heart rate
- increased breathing rate
- all of the above
66Harry has a brain tumor that is interfering with
the function of his hypothalamus. Would you
expect this tumor to interfere with autonomic
function? Why or why not?
- Yes hypothalamus regulates ANS.
- Yes all brain tumors affect ANS functioning.
- No ANS has no connection to the hypothalamus.
- No ANS function is regulated by thalamus.
67Higher Order Functions
- Involve cerebral cortex
- Involve both conscious and subconscious
processing - Are not part of genetic wiring (reflex) can be
modified - e.g. memory and consciousness
68Memory
- Memory storage and retrieval of info
- Fact memories specific bits of info
- Skill memories learned motor behaviors
- Short term memory (STM)
- primary/working memory
- Rapid recall but short retention
- Store 7-8 bits of info at one time
- STM can be converted to long term memory for more
permanent storage
69Memory
- Memory consolidation STM?LTM
- Performed by hippocampus
- Depends on
- Emotional State
- Rehearsal
- Association
- Automatic memory
70Memory
- Long term memory (LTM)
- Infinite info
- Can be stored for lifetime
- Secondary memories
- fade with time, can be difficult to recall much
later - Tertiary memories
- part of ones consciousness (e.g. name)
- LTMs are broken into component parts to store in
appropriate cerebral cortex - E.g. visual, olfactory, etc.
71Memory
- Mechanism of memory storage not clearly
understood but involves - New mRNA and protein synthesis in neurons
involved - Change of shape of dendritic spines
- Change in size and number of synaptic terminals
- Release of more neurotransmitter
72Memory
- Amnesia loss of memory, due to disease or trama
of hippocampus and amygdala - Retrograde Amnesia
- Lose memories of past events,
- Remember now ? forward
- Anterograde Amnesia
- Unable to store new memories
- Only remember past
73Consciousness
- Conscious aware of external stimuli
- Unconscious range of unawareness
- Drowsy ? coma ? brain dead
74Sleep
- Sleep partial unconsciousness from which a
person can be aroused with stimuli - Deep Sleep
- Relaxed state
- Heart and respiratory rate decreased
- Minimal activity in cerebral cortex
- REM (rapid eye movement) sleep
- active, dreaming state
- Cerebral cortex as active/more active than in
conscious state - But little reaction to outside stimuli
- Skeletal muscles inhibited
75Activity in Cerebral Cortex
76- Alternate between deep and REM sleep throughout
sleep period - Sleep required for life, but not clear why
- Lack of sleep leads to serious disturbance in
mental function - During sleep protein synthesis in neurons
increases sleep may be used to repair and
recharge neural tissue
77Sleep Disorders
- Narcolepsy
- Condition where person lapses abruptly into sleep
for 15 min - Usually follows pleasant event
- Cause unknown
- Sufferers show reduced levels of REM sleep at
night - Sleep apnea
- Person stops breathing until hypoxia (lack of O2)
wakes them - Hypoxic wake response ability declines with age
or respiratory illness
78Arousal
- Requires Reticular Activating System (RAS)
- RAS located in brainstem, provides consciousness
- Mechanism
- Stimulation of RAS ? activation of cerebral
cortex - Positive feedback (reverberation) on RAS
maintains consciousness after initial stimulus - Over time RAS becomes less responsive sleep
feeling - Internal clock in suprashiasmatic nucleus of
hypothalamus - sets normal sleep-wake cycle
79Which of the following is not a characteristic of
higher order functions?
- require cerebral cortex
- involve conscious and unconscious processing
- part of the programmed wiring of the brain
- subject to modification over time
80After suffering a head injury in an automobile
accident, David has difficulty comprehending what
he hears or reads. This symptom might indicate
damage to which portion of his brain?
- right temporal lobe of the cerebrum
- left temporal lobe of the cerebrum
- frontal lobe of the cerebrum
- left parietal lobe of the cerebrum
81As you recall facts while you take your AP test,
which type of memory are you using?
- long term memory
- skill memory
- memory consolidation
- short term memory
82You are asleep. What would happen to you if your
reticular activating system were suddenly
stimulated?
- You would wake up.
- You would experience a pleasant dream.
- You would experience a nightmare.
- You would experience muscular contraction and
cramping.
83Age Related Changes
- Decrease
- Brain size and weight (cerebrum)
- Number of neurons
- Blood flow to brain (incr. chance of stroke)
- Number of synapses
- Neurotransmitter production
84Age Related Changes
- Accumulation of deposits
- Inside Cells
- lipofuscin granular pigment
- Neurofibrillary tangles packed neurofibrils
- Extracellular
- plaques collections of fibrillar proteins
entangling abnormal cell processes - Amyloid proteins normal proteins misfolding
become sticky - All forms of deposits affect processing and
memory ability, motor speed, and sensory
sensitivity
85Age Related Changes
- Increased disease
- Alzheimers Disease
- Loss of higher order functions
- Occurs in 15 over 65 years
- Progressive, untreatable
- Due to reduction of Ach levels and accumulation
of beta amyloid peptide - Plaques and tangles
- Current treatments block Ach breakdown
86Age Related Changes
- 2. Huntingtons Disease
- genetic, middle age onset
- Accumulation of huntingtons protein kills
neurons of basal ganglia and cerebral cortex ?
ticks, cognitive dysfunction - Progressive and fatal
- On set ? death in 15 years
87One of the problems associated with aging is
difficulty in recalling things or even a total
loss of memory. What are some possible reasons
for these changes?
- decreased blood flow to brain
- formation of neurofibrillary tangles
- reduction in brain weight
- all of the above
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89SUMMARY
- Brain, spinal cord, and peripheral nerves
continuously communicate with each other and with
internal and external environments - Information arrives via sensory receptors and
ascends within afferent division, while motor
commands descend and are distributed by efferent
division - Sensory receptor is a specialized cell or cell
process that monitors specific conditions within
body or in external environment - arriving information is called a sensation
- awareness of a sensation is a perception
90SUMMARY
- General senses are pain, temperature, physical
distortion, and chemical detection - receptors for these senses are distributed
throughout the body - Special senses, located in specific sense organs,
are structurally more complex - Each receptor cell monitors a specific receptive
field - Transduction begins when a large enough stimulus
changes the receptor potential reaching generator
potential
91SUMMARY
- Tonic receptors are always active
- Phasic receptors provide information about
intensity and rate of change of a stimulus - Adaptation is a reduction in sensitivity in
presence of a constant stimulus - Tonic receptors are slow-adapting receptors,
while phasic receptors are fast-adapting
receptors - 3 types of nociceptor found in the body provide
information on extremes of pain - temperature
- mechanical damage
- dissolved chemicals
- myelinated Type A fibers carry fast pain
- Type C fibers carry slow pain
92SUMMARY
- Thermoreceptors are found in the dermis
- Mechanoreceptors are sensitive to distortion of
their membranes and include - tactile receptors, baroreceptors, proprioceptors
- 6 types of tactile receptors in the skin
- 3 types of proprioceptors
- Chemoreceptors include carotid bodies and aortic
bodies - Sensory neurons that deliver sensations to CNS
are referred to as first-order neurons - synapse on second-order neurons in brain stem or
spinal cord - next neuron in this chain is a third-order
neuron, found in the thalamus
93SUMMARY
- Functions of the autonomic nervous system (ANS)
- Functions of CNS preganglionic neurons
- The sympathetic division
- Sympathetic activation
- Function of neurotransmitters
- acetylcholine (ACh)
- norepinephrine (NE)
- epinephrine (E)
94SUMMARY
- Sympathetic ganglionic neurons
- Two types of sympathetic receptors
- alpha receptors
- beta receptors
- The parasympathetic division (food processing and
energy absorption) - Muscarinic and nicotinic receptors
95SUMMARY
- Memory
- shortterm or longterm
- Memory consolidation
- Consciousness, unconsciousness, and sleep
- Age-related changes in the nervous system