brain stem overview: midbrain, pons & medulla - · pdf filebrain stem overview: midbrain,...
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Brain Stem Overview: Midbrain,Pons & Medulla
Figure 9-9d: ANATOMY SUMMARY: The Brain
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• Many cranial nerves enter• Pyramids – nerve tracts crossover• Midbrain – eye movement control• Pons – breathing, signal relay• Medulla – involuntary functions
– Examples: Blood pressure, breathing, vomiting• Reticular formation:
– Network in brain stem– Arousal, sleep, pain, & muscle tone
Brain Stem Overview: Midbrain,Pons & Medulla
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Cranial Nerves
Table 9-1: The Cranial Nerves
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• Cervical• Thoracic• Lumbar• Sacral
Spinal Cord Regions
Figure 9-4a: ANATOMY SUMMARY: The Central Nervous System
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Cross-Sectional Anatomy of theSpinal Cord
• Anterior median fissure – separates anterior funiculi• Posterior median sulcus – divides posterior funiculi
Figure 12.30a
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Dermatomes
Figure 13.12
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Gray Matter: Organization
Figure 12.31
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Spinal Cord Organization
Figure 9-7: Specialization in the spinal cord
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White Matter: PathwayGeneralizations
Figure 12.32
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Nonspecific Ascending Pathway
• Nonspecificpathway forpain,temperature,and crudetouch withinthe lateralspinothalamictract
Figure 12.33b
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The Direct (Pyramidal) System
Figure 12.34a
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Spinal Cord Trauma:Transection
• Cross sectioning of the spinal cord at anylevel results in total motor and sensoryloss in regions inferior to the cut
• Paraplegia – transection between T1 andL1
• Quadriplegia – transection in the cervicalregion
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Reflexes
• A reflex is a rapid, predictable motorresponse to a stimulus
• Reflexes may:– Be inborn (intrinsic) or learned (acquired)– Involve only peripheral nerves and the spinal
cord– Involve higher brain centers as well
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Reflex Arc
• There are five components of a reflex arc– Receptor – site of stimulus– Sensory neuron – transmits the afferent
impulse to the CNS– Integration center – either monosynaptic or
polysynaptic region within the CNS– Motor neuron – conducts efferent impulses
from the integration center to an effector– Effector – muscle fiber or gland that responds
to the efferent impulse
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Reflex Arc
Figure 13.14
Receptor12 3
4
Sensory neuron Integrationcenter
5 EffectorMotor neuron
Stimulus
Skin
Spinal cord(in cross-section)
Interneuron
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• Vision• Hearing• Taste• Smell• Equilibrium
Special Senses – ExternalStimuli
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• Chemoreceptors• Mechanoreceptors• Photoreceptors• Thermoreceptors• Nociceptors
Sensory Receptor Types
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Sensory Receptor Types
Figure 10-1: Sensory receptors
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General Properties of SensorySystems
Figure 10-4: Sensory pathways
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• Mechanoreceptors• Free nerve endings• Pacinian corpuscles• Ruffini corpuscles• Merkel receptors• Meisaner's corpuscles• Barroreceptors
Touch (pressure)
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Touch (pressure)
Figure 10-11: Touch-pressure receptors
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• Touch• Temperature• Pain• Itch• Proprioception• Pathway
Somatic Senses – Internal Stimuli
Figure 10-10: The somatosensory cortex
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Somatic Pathways
Figure 10-9: Sensory pathways cross the body’s midline
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Sensory Modality
Figure 10-3: Two-point discrimination
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Sensory Modality
Figure 10-6: Lateral inhibition
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• Modality of the stimulus• location• Intensity• Duration• Tonic receptors• Phasic receptors• Adaptation
Stimulus Coding andProcessing
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Temperature
Figure 10-7: Sensory coding for stimulus intensity and duration
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Adaptation of SensoryReceptors
• Receptors responding to pressure, touch,and smell adapt quickly
• Receptors responding slowly includeMerkel’s discs, Ruffini’s corpuscles, andinteroceptors that respond to chemicallevels in the blood
• Pain receptors and proprioceptors do notexhibit adaptation