1. Chapter 15 Sensory, Motor & Integrative Systems
Levels and components of sensation
Pathways for sensations from body to brain
Pathways for motor signals from brain to body
Integration Process
wakefulness and sleep
learning and memory
Tortora & Grabowski 9/e 2000 JWS

2. Is Sensation Different from Perception?
Sensation is any stimuli the body is aware of
What are we not aware of?
X-rays, ultra high frequency sound waves, UV light
We have no sensory receptors for those stimuli
Perception is the conscious awareness & interpretation of a sensation.
precisely localization & identification
memories of our perceptions are stored in cortex
Tortora & Grabowski 9/e 2000 JWS

3. Sensory Modalities Different types of sensations
touch, pain, temperature, vibration, hearing, vision
Each type of sensory neuron can respond to only one type of stimuli
Two classes of sensory modalities
general senses
somatic are sensations from body walls
visceral are sensations from internal organs
special senses
smell, taste, hearing, vision, and balance
Tortora & Grabowski 9/e 2000 JWS

4. Process of Sensation Sensory receptors demonstrate selectivity
respond to only one type of stimuli
Events occurring within a sensation
stimulation of the receptor
transduction (conversion) of stimulus into a graded potential
vary in amplitude and are not propagated
generation of impulses when graded potential reaches threshold
integration of sensory input by the CNS
Tortora & Grabowski 9/e 2000 JWS

5. Sensory Receptors Selectively respond to only one kind of stimuli
Have simple or complex structures
General Sensory Receptors (Somatic Receptors)
no structural specializations in free nerve endings that provide us with pain, tickle, itch, temperatures
some structural specializations in receptors for touch, pressure & vibration
Special Sensory Receptors (Special Sense Receptors)
very complex structures---vision, hearing, taste, & smell
Tortora & Grabowski 9/e 2000 JWS

6. Classification of Sensory Receptors
Structural classification
Type of response to a stimulus
Location of receptors & origin of stimuli
Type of stimuli they detect
Tortora & Grabowski 9/e 2000 JWS

7. Structural Classification of Receptors
Free nerve endings
bare dendrites
pain, temperature, tickle, itch & light touch
Encapsulated nerve endings
dendrites enclosed in connective tissue capsule
pressure, vibration & deep touch
Separate sensory cells
specialized cells that respond to stimuli
vision, taste, hearing, balance
Tortora & Grabowski 9/e 2000 JWS

8. Structural Classification
Compare free nerve ending, encapsulated nerve ending and sensory receptor cell
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9. Classification by Response to Stimuli
Generator potential
free nerve endings, encapsulated nerve endings & olfactory receptors produce generator potentials
when large enough, it generates a nerve impulse in a first-order neuron
Receptor potential
vision, hearing, equilibrium and taste receptors produce receptor potentials
receptor cells release neurotransmitter molecules on first-order neurons producing postsynaptic potentials
PSP may trigger a nerve impulse
Amplitude of potentials vary with stimulus intensity
Tortora & Grabowski 9/e 2000 JWS

10. Classification by Location
Exteroceptors
near surface of body
receive external stimuli
hearing, vision, smell, taste, touch, pressure, pain, vibration & temperature
Interoceptors
monitors internal environment (BV or viscera)
not conscious except for pain or pressure
Proprioceptors
muscle, tendon, joint & internal ear
senses body position & movement
Tortora & Grabowski 9/e 2000 JWS

11. Classification by Stimuli Detected
Mechanoreceptors
detect pressure or stretch
touch, pressure, vibration, hearing, proprioception, equilibrium & blood pressure
Thermoreceptors detect temperature
Nociceptors detect damage to tissues
Photoreceptors detect light
Chemoreceptors detect molecules
taste, smell & changes in body fluid chemistry
Tortora & Grabowski 9/e 2000 JWS

12. Adaptation of Sensory Receptors
Change in sensitivity to long-lasting stimuli
decrease in responsiveness of a receptor
bad smells disappear
very hot water starts to feel only warm
potential amplitudes decrease during a maintained, constant stimulus
Receptors vary in their ability to adapt
Rapidly adapting receptors (smell, pressure, touch)
adapt quickly; specialized for signaling stimulus changes
Slowly adapting receptors (pain, body position)
continuation of nerve impulses as long as stimulus persists
Tortora & Grabowski 9/e 2000 JWS

13. Somatic Tactile Sensations
Touch
crude touch is ability to perceive something has touched the skin
discriminative touch provides location and texture of source
Pressure is sustained sensation over a large area
Vibration is rapidly repetitive sensory signals
Itching is chemical stimulation of free nerve endings
Tickle is stimulation of free nerve endings only by someone else
Tortora & Grabowski 9/e 2000 JWS

14. Meissner’s Corpuscle
Dendrites enclosed in CT in dermal papillae of hairless skin
Discriminative touch & vibration-- rapidly adapting
Generate impulses mainly at onset of a touch
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15. Hair Root Plexus
Free nerve endings found around follicles, detects movement of hair
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16. Merkel’s Disc Flattened dendrites touching cells of stratum basale
Used in discriminative touch (25% of receptors in hands)
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17. Ruffini Corpuscle Found deep in dermis of skin
Detect heavy touch, continuous touch, & pressure
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18. Pacinian Corpuscle
Onion-like connective tissue capsule enclosing a dendrite
Found in subcutaneous tissues & certain viscera
Sensations of pressure or high-frequency vibration
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19. Thermal Sensations
Free nerve endings with 1mm diameter receptive fields on the skin surface
Cold receptors in the stratum basale respond to temperatures between degrees F
Warm receptors in the dermis respond to temperatures between degrees F
Both adapt rapidly at first, but continue to generate impulses at a low frequency
Pain is produced below 50 and over 118 degrees F.
Tortora & Grabowski 9/e 2000 JWS

20. Pain Sensations Nociceptors = pain receptors
Free nerve endings found in every tissue of body except the brain
Stimulated by excessive distension, muscle spasm, & inadequate blood flow
Tissue injury releases chemicals such as K+, kinins or prostaglandins that stimulate nociceptors
Little adaptation occurs
Tortora & Grabowski 9/e 2000 JWS

21. Types of Pain Fast pain (acute) Slow pain (chronic)
occurs rapidly after stimuli (.1 second)
sharp pain like needle puncture or cut
not felt in deeper tissues
larger A nerve fibers
Slow pain (chronic)
begins more slowly & increases in intensity
aching or throbbing pain of toothache
in both superficial and deeper tissues
smaller C nerve fibers
Tortora & Grabowski 9/e 2000 JWS

22. Localization of Pain Superficial Somatic Pain arises from skin areas
Deep Somatic Pain arises from muscle, joints, tendons & fascia
Visceral Pain arises from receptors in visceral organs
localized damage (cutting) intestines causes no pain
diffuse visceral stimulation can be severe
distension of a bile duct from a gallstone
distension of the ureter from a kidney stone
Phantom limb sensations -- cells in cortex still
Tortora & Grabowski 9/e 2000 JWS

23. Referred Pain
Visceral pain that is felt just deep to the skin overlying the stimulated organ or in a surface area far from the organ.
Skin area & organ are served by the same segment of the spinal cord.
Heart attack is felt in skin along left arm since both are supplied by spinal cord segment T1-T5
Tortora & Grabowski 9/e 2000 JWS

24. Pain Relief
Aspirin and ibuprofen block formation of prostaglandins that stimulate nociceptors
Novocaine blocks conduction of nerve impulses along pain fibers
Morphine lessen the perception of pain in the brain.
Tortora & Grabowski 9/e 2000 JWS

25. Proprioceptive or Kinesthetic Sense
Awareness of body position & movement
walk or type without looking
estimate weight of objects
Proprioceptors adapt only slightly
Sensory information is sent to cerebellum & cerebral cortex
from muscle, tendon, joint capsules & hair cells in the vestibular apparatus
Tortora & Grabowski 9/e 2000 JWS

26. Muscle Spindles
Specialized intrafusal muscle fibers enclosed in a CT capsule and innervated by gamma motor neurons
Stretching of the muscle stretches the muscle spindles sending sensory information back to the CNS
Spindle sensory fiber monitor changes in muscle length
Brain regulates muscle tone by controlling gamma fibers
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27. Golgi Tendon Organs Found at junction of tendon & muscle
Consists of an encapsulated bundle of collagen fibers laced with sensory fibers
When the tendon is overly stretched, sensory signals head for the CNS & resulting in the muscle’s relaxation
Tortora & Grabowski 9/e 2000 JWS

28. Joint Receptors Ruffini corpuscles Pacinian corpuscles
found in joint capsule
respond to pressure
Pacinian corpuscles
found in connective tissue around the joint
respond to acceleration & deceleration of joints
Tortora & Grabowski 9/e 2000 JWS

29. Somatic Sensory Pathways
First-order neuron conduct impulses to brainstem or spinal cord
either spinal or cranial nerves
Second-order neurons conducts impulses from spinal cord or brainstem to thalamus--cross over to opposite side before reaching thalamus
Third-order neuron conducts impulses from thalamus to primary somatosensory cortex (postcentral gyrus of parietal lobe)
Tortora & Grabowski 9/e 2000 JWS

30. Posterior Column-Medial Lemniscus Pathway of CNS
Proprioception, vibration, discriminative touch, weight discrimination & stereognosis
Signals travel up spinal cord in posterior column
Fibers cross-over in medulla to become the medial lemniscus pathway ending in thalamus
Thalamic fibers reach cortex
Tortora & Grabowski 9/e 2000 JWS

31. Spinothalamic Pathways
Lateral spinothalamic tract carries pain & temperature
Anterior tract carries tickle, itch, crude touch & pressure
First cell body in DRG with synapses in cord
2nd cell body in gray matter of cord, sends fibers to other side of cord & up through white matter to synapse in thalamus
3rd cell body in thalamus projects to cerebral cortex
Tortora & Grabowski 9/e 2000 JWS

32. Somatosensory Map of Postcentral Gyrus
Relative sizes of cortical areas
proportional to number of sensory receptors
proportional to the sensitivity of each part of the body
Can be modified with learning
learn to read Braille & will have larger area representing fingertips
Tortora & Grabowski 9/e 2000 JWS

33. Sensory Pathways to the Cerebellum
Major routes for proprioceptive signals to reach the cerebellum
anterior spinocerebellar tract
posterior spinocerebellar tract
Subconscious information used by cerebellum for adjusting posture, balance & skilled movements
Signal travels up to same side inferior cerebellar peduncle
Tortora & Grabowski 9/e 2000 JWS

34. Tertiary Syphilis
Sexually transmitted disease caused by bacterium Treponema pallidum.
Third clinical stage known as tertiary syphilis
Progressive degeneration of posterior portions of spinal cord & neurological loss
loss of somatic sensations
proprioceptive impulses fail to reach cerebellum
People watch their feet while walking, but still uncoordinated and jerky
Tortora & Grabowski 9/e 2000 JWS

35. Somatic Motor Pathways
Control of body movement
motor portions of cerebral cortex
initiate & control precise movements
basal ganglia help establish muscle tone & integrate semivoluntary automatic movements
cerebellum helps make movements smooth & helps maintain posture & balance
Somatic motor pathways
direct pathway from cerebral cortex to spinal cord & out to muscles
indirect pathway includes synapses in basal ganglia, thalamus, reticular formation & cerebellum
Tortora & Grabowski 9/e 2000 JWS

36. Primary Motor Cortex Precentral gyrus initiates voluntary movement
Cells are called upper motor neurons
Muscles represented unequally (according to the number of motor units)
More cortical area is needed if number of motor units in a muscle is high
vocal cords, tongue, lips, fingers & thumb
Tortora & Grabowski 9/e 2000 JWS

37. Direct Pathway (Pyramidal Pathway)
1 million upper motor neurons in cerebral cortex
60% in precentral gyrus & 40% in postcentral gyrus
Axons form internal capsule in cerebrum and pyramids in the medulla oblongata
90% of fibers decussate(cross over) in the medulla
right side of brain controls left side muscles
Terminate on interneurons which synapse on lower motor neurons in either:
nuclei of cranial nerves or anterior horns of spinal cord
Integrate excitatory & inhibitory input to become final common pathway
Tortora & Grabowski 9/e 2000 JWS

38. Details of Motor Pathways
Lateral corticospinal tracts
cortex, cerebral peduncles, 90% decussation of axons in medulla, tract formed in lateral column.
skilled movements hands & feet
Anterior corticospinal tracts
the 10% of axons that do not cross
controls neck & trunk muscles
Corticobulbar tracts
cortex to nuclei of CNs ---III, IV, V, VI, VII, IX, X, XI & XII
movements of eyes, tongue, chewing, expressions & speech
Tortora & Grabowski 9/e 2000 JWS

39. Location of Direct Pathways
Lateral corticospinal tract
Anterior corticospinal tract
Corticobulbar tract
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40. Paralysis Flaccid paralysis = damage lower motor neurons
no voluntary movement on same side as damage
no reflex actions
muscle limp & flaccid
decreased muscle tone
Spastic paralysis = damage upper motor neurons
paralysis on opposite side from injury
increased muscle tone
exaggerated reflexes
Tortora & Grabowski 9/e 2000 JWS

41. Indirect Pathways All other descending motor pathways
Complex polysynaptic circuits
include basal ganglia, thalamus, cerebellum, reticular formation
Descend in spinal cord as 5 major tracts
All 5 tracts end upon interneurons or lower motor neurons
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42. Final Common Pathway
Lower motor neurons receive signals from both direct & indirect upper motor neurons
Sum total of all inhibitory & excitatory signals determines the final response of the lower motor neuron & the skeletal muscles
Tortora & Grabowski 9/e 2000 JWS

43. Basal Ganglia Helps to program automatic movement sequences
walking and arm swinging or laughing at a joke
Set muscle tone by inhibiting other motor circuits
Damage is characterized by tremors or twitches
Tortora & Grabowski 9/e 2000 JWS

44. Basal Ganglia Connections
Circuit of connections
cortex to basal ganglia to thalamus to cortex
planning movements
Output from basal ganglia to reticular formation
reduces muscle tone
damage produces rigidity of Parkinson’s disease
Tortora & Grabowski 9/e 2000 JWS

45. Cerebellar Function Aspects of Function learning
coordinated & skilled movements
posture & equilibrium
1. Monitors intentions for movements -- input from cerebral cortex
2. Monitors actual movements with feedback from proprioceptors
3. Compares intentions with actual movements
4. Sends out corrective signals to motor cortex
Tortora & Grabowski 9/e 2000 JWS

46. Wakefulness and Sleep Circadian rhythm
24 hour cycle of sleep and awakening
established by hypothalamus
Awake means to be able to react consciously to stimuli
EEG recordings show large amount of activity in cerebral cortex when awake
Tortora & Grabowski 9/e 2000 JWS

47. Reticular Activating System
RAS has connections to cortex & spinal cord.
Many types of inputs activate the RAS---pain, light, noise, muscle activity, touch
Produces state of wakefulness called consciousness
Coma is sleeplike state
deep coma has no reflexes
death if cardiovascular reflexes are lost
Tortora & Grabowski 9/e 2000 JWS

48. Sleep
State of altered or partial consciousness from which a person can be aroused
Triggers for sleep are unclear
adenosine levels increase with brain activity
adenosine levels inhibit activity in RAS
caffeine prevents adenosine from inhibiting RAS
Two types of normal sleep
NREM = non-rapid eye movement sleep
REM = rapid eye movement sleep
Tortora & Grabowski 9/e 2000 JWS

49. Non-Rapid Eye Movement Sleep
Stage 1
person is drifting off with eyes closed (first few minutes)
Stage 2
fragments of dreams
eyes may roll from side to side
Stage 3
very relaxed, moderately deep
20 minutes, body temperature & BP have dropped
Stage 4 = deep sleep
bed-wetting & sleep walking occur in this phase
Tortora & Grabowski 9/e 2000 JWS

50. REM Sleep Most dreams occur during REM sleep
In first 90 minutes of sleep:
go from stage 1 to 4 of NREM,
go up to stage 2 of NREM
to REM sleep
Cycles repeat until total REM sleep totals 90 to 120 minutes
Neuronal activity & oxygen use highest in REM sleep
Total sleeping & dreaming time decreases with age
Tortora & Grabowski 9/e 2000 JWS

51. Learning & Memory Learning is acquiring new knowledge
Memory is retaining that knowledge
short-term memory
recall phone number while dialing
depends upon electrical events (reverberating circuits)
long-term memory
frequent retrieval of specific information helps with memory consolidation (learning)
structural or biochemical changes occurs
increase in dendrites, enlarge endbulbs, increase in presynaptic terminals or formation of additional membrane receptors
Recently acquired memory lost first with coma or shock treatments
Tortora & Grabowski 9/e 2000 JWS

52. Spinal Cord Injury Damaged by tumor, herniated disc, clot or trauma
Complete transection is cord severed resulting loss of both sensation & movement below the injury
Paralysis
monoplegia is paralysis of one limb only
diplegia is paralysis of both upper or both lower
hemiplegia is paralysis of one side
quadriplegia is paralysis of all four limbs
Spinal shock is loss of reflex function (areflexia)
slow heart rate, low blood pressure, bladder problem
reflexes gradually return
Tortora & Grabowski 9/e 2000 JWS

53. Cerebral Palsy Loss of motor control and coordination
Damage to motor areas of the brain
infection of pregnant woman with rubella virus
radiation during fetal life
temporary lack of O2 during birth
Not a progressive disease, but irreversible
Tortora & Grabowski 9/e 2000 JWS

54. Parkinson Disease Progressive disorder striking victims at age 60
Environmental toxins may be the cause
Neurons from the substantia nigra do not release enough dopamine onto basal ganglia
tremor, rigidity, bradykinesia (slow movement) or hypokinesia (decreasing range of movement)
may affect walking, speech, even facial expression
Treatments
drugs to increase dopamine levels, or to prevent its breakdown, surgery to transplant fetal tissue or removal of part of globus pallidus to slow tremors
Tortora & Grabowski 9/e 2000 JWS