Transcript 12_lecture_ppt Motor and Sensory Cortex Only

Chapter 12
Integration of
Nervous System
Functions
Presynaptic terminals associated
with a postsynaptic neuron
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Sensation (Perception)
• The conscious awareness of stimuli
received by sensory receptors
• Sensation requires
– A stimulus
– A receptor
– Conduction of an action potential to the CNS
– Translation of the action potential
– Processing of the action potential in the CNS
so that the person is aware of the sensation
Sensory Areas of the Cerebral Cortex
• Sensory pathways project to primary
sensory areas in the cerebral cortex
– Somatic sensory
– Visual
– Auditory
– Taste
– Olfactory
Fig. 12.6
Sensory Areas of the Cerebral Cortex
• organized topographically
in somatic sensory cortex
• post-central gyrus
• Nerve distibutions
– Size of body part = relative
amt of sensory receptors
there
• More in face
Fig. 12.7
Control of Skeletal Muscles
• Lower motor neurons
– Axons leave CNS thru nerves, innervate
skeletal muscles (motor units)
– Cell bodies found in cranial nuclei or anterior
horn of spinal cord gray matter
• Upper motor neurons
– form tracts that directly or indirectly control the
activities of lower motor neurons
– Cell bodies in cerebral cortex, brainstem, and
cerebellum
Motor Area of the Cerebral Cortex
• primary motor cortex is
pre-central gyrus
• organized topographically
• premotor and prefrontal
areas are staging areas
for motor function
Fig. 12.8
PAIN
• sensation characterized by group of
unpleasant and complex perceptual and
emotional experiences
• Triggers autonomic, psychological,
somatic motor responses
Two types of pain sensation
1. sharp, localized
• rapidly conducted APs carried by large (diameter)
myelinated axons
2. diffuse, burning/aching pain
• APs from slower, smaller, less myelinated axons
Analgesics
• Pain relievers (reversible)
• Block transmission of pain in spinal cord or
• Cerebral cortex—modify pain reception
Anesthetics
• Depress nerve cell function; loss of
sensation/concsciousness (reversible)
• “Local”: injection; blocks APs
• “general”: drugs act on reticular formation,
lose consciousness
Referred Pain
• Pain sensation in a different part of body
(not stimulus source)
• Ex: in skin when internal organ is inflamed
– Skin and organ neurons converge onto same
ascending neurons in spinal cord
– Brain can’t differentiate
– Sensation referred to most superficial
• Heart attacks...feel pain in left shoulder...
Phantom Pain
• Amputees
• AP along pathway, integration sends pain
sensation to sensory receptors
• EVEN IF NO LONGER PRESENT IN THE
BODY...
• Another weird thing...hit your funny bone
(ulnar nerve) & 4th/5th digits hurt
Chronic Pain
• Tissue damage (arthritis) or unknown
cause
• Varied levels of pain perception
• Brain can regulate and suppress it
• If that is non-functional, pain’s a problem &
can be more intense
• Chronic Pain Syndrome
 Just FYI…Memory 
• At least three kinds of memory exist
– Sensory
• Very brief (less than a second) retention of sensory input
received by the brain while something is scanned, evaluated,
and acted on
– Short-term memory
• Lasts for a few seconds to a few minutes and is limited to 7
or 8 pieces of information
– Long-term memory
• Lasts for hours or longer (a lifetime)
• Two types
– Explicit memory: retention of facts, such as names, dates, and
places
– Implicit memory: development of skills such as riding a bicycle
or playing a piano
Fig.
12.16
Effects of Aging on the Nervous System
• There is general decline in sensory and
motor functions as a person ages
• Short-term memory is decreased in
most older people
• Thinking ability does not decrease in
most older people
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