Page 567 - Fundamentals of anatomy physiology
P. 567
554 Unit 3 Control and Regulation diencephalon and brain stem primarily direct the behavior of
newborn infants.
Cranial and spinal reflexes control the most basic motor ac-
tivities. Integrative centers in the brain perform more elaborate Checkpoint
processing. As we move from the medulla oblongata to the ce-
rebral cortex, the motor patterns become increasingly complex 1 1. What is the anatomical basis for the fact that the left
and variable. The primary motor cortex of the cerebral hemi- side of the brain controls motor function on the right
spheres directs the most complex and variable motor activities. side of the body?
During development, the spinal reflexes and cranial re- 1 2. An injury involving the superior portion of the motor
flexes appear first. More complex reflexes and motor patterns cortex affects which region of the body?
develop as CNS neurons multiply, enlarge, and interconnect.
The process proceeds slowly, as billions of neurons establish 1 3. What effect would increased stimulation of the motor
trillions of synaptic connections. At birth, neither the cerebral neurons of the red nucleus have on muscle tone?
nor the cerebellar cortex is fully functional. Centers in the
See the blue Answers tab at the back of the book.
Related Clinical Terms
15 analgesia: The inability to feel pain while still conscious. spastic paralysis: The chronic pathological condition in which
flaccid paralysis: Weakness or loss of muscle tone as a result of muscles are affected by persistent spasms and exaggerated
tendon reflexes due to damage to motor nerves of the central
disease or injury to the nerves innervating the muscles. nervous system.
hyperalgesia: Increased sensitivity to pain that may be caused by
syphilis: A sexually transmitted disease (STD) caused by the bacte-
damage to nociceptors or peripheral nerves. rium Treponema pallidum. Many of the signs and symptoms are
pain threshold: The lowest intensity of stimulation at which pain indistinguishable from those of other diseases. Late-stage un-
treated syphilis can cause progressive degeneration of the poste-
is experienced. It can vary among individuals. rior column pathway, spinocerebellar pathway, and dorsal roots
pain tolerance: The maximum pain level an individual can of the spinal cord.
withstand. It can vary among individuals.
Chapter Review external environments. Information arrives by sensory recep-
tors and ascends within the afferent division, while motor
Study Outline commands descend and are distributed by the efferent
division.
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15-2 Sensory receptors connect our internal and external
• Chapter Quizzes, Chapter Practice Test, Art-labeling Activities,
Animations, MP3 Tutor Sessions, and Clinical Case Studies environments with the nervous system p. 536
3. A sensory receptor is a specialized cell or cell process that
• Practice Anatomy Lab ™ • A&P Flix ™
• Interactive Physiology • PhysioEx ™ monitors specific conditions within the body or in the exter-
nal environment. Arriving information is a sensation; aware-
® ness of a sensation is a perception.
4. The general senses are our sensitivity to pain, temperature,
An Introduction to Sensory Pathways and the Somatic touch, pressure, vibration, and proprioception. Receptors for
Nervous System p. 535 these senses are distributed throughout the body. Special senses,
1. The nervous system works as an integrated unit. This chapter located in specific sense organs, are structurally more complex.
5. Each receptor cell monitors a specific receptive field. Transduc-
considers sensory pathways (sensory receptors and sensory tion begins when a large enough stimulus depolarizes the
processing centers in the brain) and motor pathways (includ- receptor potential or generator potential to the point where action
ing both conscious and subconscious motor functions). potentials are produced. (Figure 15–2)
(Figure 15–1) 6. A labeled line is a link between a peripheral receptor and a
cortical neuron. Tonic receptors are always active. Phasic
15-1 Sensory information from all parts of the body is routed receptors provide information about the intensity and rate
of change of a stimulus. Adaptation is a reduction in sensitiv-
to the somatosensory cortex p. 535 ity in the presence of a constant stimulus. Tonic receptors are
2. The brain, spinal cord, and peripheral nerves continuously
communicate with each other and with the internal and
