The Central Nervous System

1
Chapter 12

• The Central Nervous System

2
The Brain

• Composed of wrinkled, pinkish gray tissue
• Surface anatomy includes cerebral hemispheres,
  cerebellum, and brain stem

3
Ventricles

• System of fluid filled cavities
• The ventricles are
• The paired C-shaped lateral ventricles
• The third ventricle found in the diencephalon
• The fourth ventricle found in the hindbrain
  dorsal to the pons

4
Cerebral Hemispheres

• Form the superior part of the brain and make up
  83 of its mass
• Contain ridges (gyri) and shallow grooves (sulci)
• Contain deep grooves called fissures
• Are separated by the longitudinal fissure
• Have three basic regions cortex, white matter,
  and basal nuclei

5
Major Lobes, Gyri, and Sulci of
the Cerebral Hemisphere

• Deep sulci divide the hemispheres into five
  lobes
• Frontal, parietal, temporal, occipital, and
  insula
• Central sulcus separates the frontal and
  parietal lobes

6
Major Lobes, Gyri, and Sulci of the Cerebral
Hemisphere

• Parieto-occipital sulcus separates the parietal
  and occipital lobes
• Lateral sulcus separates the parietal and
  temporal lobes
• The precentral and postcentral gyri border the
  central sulcus

7
Cerebral Cortex

• The cortex superficial gray matter accounts
  for 40 of the mass of the brain
• Consists of neuron cell bodies, dendrites,
  unmyelinated axons, no fiber tracts
• Conscious mind
• It enables sensation, communication, memory,
  understanding, and voluntary movements
• Each hemisphere acts contralaterally (controls
  the opposite side of the body)
• Hemispheres are not equal in function

8
Functional Areas of the Cerebral Cortex

• The three types of functional areas are
• Motor areas control voluntary movement
• Sensory areas conscious awareness of sensation
• Association areas integrate diverse information

9
Cerebral Cortex Motor Areas

• Lie in posterior part of frontal lobes
• Primary (somatic) motor cortex
• Allows conscious control of precise, skilled,
  voluntary movements
• The entire body is represented this cortex

10
Cerebral Cortex Motor Areas

• 2. Premotor Cortex
• Memory bank for skilled motor activities already
  learned
• 3. Brocas Area
• A motor speech area that directs muscles of the
  tongue
• 4. Frontal Eye Field
• Controls voluntary eye movement

11
Cerebral Cortex Motor Areas

• 2. Premotor Cortex
• Memory bank for skilled motor activities already
  learned
• 3. Brocas Area
• A motor speech area that directs muscles of the
  tongue
• 4. Frontal Eye Field
• Controls voluntary eye movement

12
Cerebral Cortex Sensory Areas

• 1. Primary somatosensory cortex
• Parietal lobe
• Receives information from somatic sensory fibers
  (muscles, skin, joints)
• Identifies the region being stimulated spatial
  discrimination

13
Cerebral Cortex Sensory Areas

• 2. Somatosensory association cortex
• Parietal lobe
• Integrates sensory info
• Forms comprehensive understanding of the stimulus
• Determines size, texture, and relationship of
  parts

14
Cerebral Cortex Sensory Areas

• Visual areas
• Occipital lobe
• Primary visual cortex
• Receives visual information from retinas
• Visual association area
• Interprets visual stimuli (e.g., color, form, and
  movement)

15
Cerebral Cortex Sensory Areas

• Auditory areas
• Temporal lobe
• Primary auditory cortex
• Receives information related to pitch, rhythm,
  and loudness
• Auditory association area
• Stores memories of sounds and permits perception
  of sounds

16
Cerebral Cortex Sensory Areas

• Olfactory (smell) cortex
• Frontal lobe above orbit
• Medial aspect - temporal
• Conscious awarness of different odors
• 6. Gustatory (taste) cortex
• Parietal lobe
• Perception of taste
• Vestibular (equilibrium) cortex
• Insula
• Conscious awareness of balance

17
Cerebral Cortex Association Areas

• Prefrontal cortex frontal lobe
• Involved with intellect, cognition, recall, and
  personality
• Necessary for judgment, reasoning, persistence,
  and conscience
• Closely linked to the limbic system (emotional
  part of the brain)

18
Cerebral Cortex Association Areas

• Language areas
• Surrounds lateral sulcus in left hemisphere
• Wernickes area involved in sounding out
  unfamiliar words
• Brocas area speech preparation and production

19
Lateralization of Cortical Function

• Lateralization each hemisphere has abilities
  not shared with its partner
• Cerebral dominance designates the hemisphere
  dominant for language
• Left hemisphere controls language, math, and
  logic
• Right hemisphere controls visual-spatial
  skills, emotion, and artistic skills

20
Cerebral White Matter

• Consists of deep myelinated fibers and their
  tracts
• It is responsible for communication between
• The cerebral cortex and lower CNS center, and
  areas of the cerebrum

21
Classification of White Matter Fibers

• Commissures connect corresponding gray areas of
  the two hemispheres

22
Classification of White Matter Fibers

• Association fibers connect different parts of
  the same hemisphere
• Projection fibers enter the hemispheres from
  lower brain or cord centers

23
Basal Nuclei

• Masses of gray matter found deep within the
  cortical white matter
• Regulate intensity of slow or stereotyped
  movements
• Inhibit antagonistic and unnecessary movement

24
Diencephalon

• 3 paired structures
• 1. Thalamus
• Sorts and relays sensory information
• 2. Epithalamus
• Pineal body/gland
• melatonin

25
Diencephalon

• 3. Hypothalamus
• Autonomic control center
• Regulates feelings of hunger and satiety
• Regulates water balance
• Regulates sleep and the sleep cycle
• Involved with perception of pleasure, fear, rage