CHAPTER 24: Neurologic System
Nervous system divided into two parts:
o CNS: brain & spinal cord
o PNS: nerve fibers outside the brain & spinal cord.
12 pairs of cranial nerves, 31 pairs of spinal nerves, & all their branches
Carries sensory (afferent) messages to CNS from sensory receptors.
Motor (efferent) messages from CNS to muscles & glands, as well as
autonomic messages that govern internal organs & blood vessels.
Cerebral Cortex:
o Cerebrum’s outer layer of nerve cells.
o Cerebral cortex is center of functions governing thought, memory, reasoning,
sensation, & voluntary movement.
Each half of cerebrum is hemisphere.
Each hemisphere divided into four lobes: frontal, parietal, occipital,
temporal.
Frontal: personality, behavior, emotions, & intellectual function
o Broca’s area: Mediated motor speech. When injured in the
dominant hemisphere, expressive aphasia results; the
person cannot talk. The person can understand language &
knows what he or she wants to say but can produce only a
garbled sound.
Parietal: postcentral gyrus is primary center for sensation
Occipital: primary visual receptor center
Temporal: behind ear has primary auditory reception center, with
functions of hearing, taste, & smell.
o Wernicke’s area: associated with language comprehension.
When damaged in person’s dominant hemisphere,
receptive aphasia results. Person hears sound, but it has
no meaning, like hearing foreign language.
, Pathways of the CNS:
o Crossed representation: notable features of the nerve tracts; the left cerebral
cortex receives sensory information from & controls likewise interactions with the
left side of the body.
Sensory Pathways:
o Monitor conscious sensation, internal organ functions, body position, & reflexes.
Motor Pathways:
o Corticospinal or Pyramidal Tract: “Higher” Motor system that permits humans
to have a very skilled & purposeful movement.
o Extrapyramidal Tracts: “Lower” more primitive motor system. Maintain
muscle tone & control body movements, especially gross automatic movements
such as walking.
o Cerebellar System: Coordinates movement, maintain equilibrium, & helps
maintain muscles & joints, the equilibrium of the body, & what kind of motor
messages are being sent from the cortex of the muscles.
Upper & Lower Motor Neurons:
o UMNs: CNS, diseases of this are stroke, cerebral palsy, & MS.
o LMNs: PNS, examples of LMNs are cranial nerves & spinal nerves of PNS.
Diseases are Bell palsy in the face (cranial nerve VII), spinal cord lesions, &
poliomyelitis.
Cranial Nerves: 12
Nervous system divided into two parts:
o CNS: brain & spinal cord
o PNS: nerve fibers outside the brain & spinal cord.
12 pairs of cranial nerves, 31 pairs of spinal nerves, & all their branches
Carries sensory (afferent) messages to CNS from sensory receptors.
Motor (efferent) messages from CNS to muscles & glands, as well as
autonomic messages that govern internal organs & blood vessels.
Cerebral Cortex:
o Cerebrum’s outer layer of nerve cells.
o Cerebral cortex is center of functions governing thought, memory, reasoning,
sensation, & voluntary movement.
Each half of cerebrum is hemisphere.
Each hemisphere divided into four lobes: frontal, parietal, occipital,
temporal.
Frontal: personality, behavior, emotions, & intellectual function
o Broca’s area: Mediated motor speech. When injured in the
dominant hemisphere, expressive aphasia results; the
person cannot talk. The person can understand language &
knows what he or she wants to say but can produce only a
garbled sound.
Parietal: postcentral gyrus is primary center for sensation
Occipital: primary visual receptor center
Temporal: behind ear has primary auditory reception center, with
functions of hearing, taste, & smell.
o Wernicke’s area: associated with language comprehension.
When damaged in person’s dominant hemisphere,
receptive aphasia results. Person hears sound, but it has
no meaning, like hearing foreign language.
, Pathways of the CNS:
o Crossed representation: notable features of the nerve tracts; the left cerebral
cortex receives sensory information from & controls likewise interactions with the
left side of the body.
Sensory Pathways:
o Monitor conscious sensation, internal organ functions, body position, & reflexes.
Motor Pathways:
o Corticospinal or Pyramidal Tract: “Higher” Motor system that permits humans
to have a very skilled & purposeful movement.
o Extrapyramidal Tracts: “Lower” more primitive motor system. Maintain
muscle tone & control body movements, especially gross automatic movements
such as walking.
o Cerebellar System: Coordinates movement, maintain equilibrium, & helps
maintain muscles & joints, the equilibrium of the body, & what kind of motor
messages are being sent from the cortex of the muscles.
Upper & Lower Motor Neurons:
o UMNs: CNS, diseases of this are stroke, cerebral palsy, & MS.
o LMNs: PNS, examples of LMNs are cranial nerves & spinal nerves of PNS.
Diseases are Bell palsy in the face (cranial nerve VII), spinal cord lesions, &
poliomyelitis.
Cranial Nerves: 12
