2. The Central Nervous System: Part A

3. Central Nervous System (CNS)
CNS consists of the brain and spinal cord
Cephalization
Evolutionary development of the rostral (anterior) portion of the CNS
Increased number of neurons in the head
Highest level is reached in the human brain

4. Functions of the Nervous System
Sensory input
Information gathered by sensory receptors about internal and external changes
Integration
Interpretation of sensory input
Motor output
Activation of effector organs (muscles and glands) produces a response

5. Sensory input
Integration
Motor output
Figure 11.1

6. Divisions of the Nervous System
Central nervous system (CNS)
Brain and spinal cord
Integration and command center
Peripheral nervous system (PNS)
Paired spinal and cranial nerves carry messages to and from the CNS

7. Peripheral Nervous System (PNS)
Two functional divisions
Sensory (afferent) division
Somatic afferent fibers—convey impulses from skin, skeletal muscles, and joints
Visceral afferent fibers—convey impulses from visceral organs

8. Motor (efferent) division
Transmits impulses from the CNS to effector organs

9. Motor Division of PNS Somatic (voluntary) nervous system
Conscious control of skeletal muscles

10. Figure 11.2 Central nervous system (CNS)
Peripheral nervous system (PNS)
Brain and spinal cord
Cranial nerves and spinal nerves
Integrative and control centers
Communication lines between the
CNS and the rest of the body
Sensory (afferent) division
Motor (efferent) division
Somatic and visceral sensory
nerve fibers
Motor nerve fibers
Conducts impulses from the CNS
to effectors (muscles and glands)
Conducts impulses from
receptors to the CNS
Somatic sensory
fiber
Somatic nervous
system
Autonomic nervous
system (ANS)
Skin
Somatic motor
(voluntary)
Visceral motor
(involuntary)
Conducts impulses
from the CNS to
skeletal muscles
Conducts impulses
from the CNS to
cardiac muscles,
smooth muscles,
and glands
Visceral sensory fiber
Stomach
Skeletal
muscle
Motor fiber of somatic nervous system
Sympathetic division
Parasympathetic
division
Mobilizes body
systems during activity
Conserves energy
Promotes house-
keeping functions
during rest
Sympathetic motor fiber of ANS
Heart
Structure
Function
Sensory (afferent)
division of PNS
Parasympathetic motor fiber of ANS
Bladder
Motor (efferent)
division of PNS
Figure 11.2

11. Embryonic Development Don’t copy
Neural plate forms from ectoderm
Neural plate invaginates to form a neural groove and neural folds

12. The neural plate forms from surface ectoderm.
Head
Neural plate
Tail 1
The neural plate forms from surface ectoderm.
Figure 12.1, step 1

13. Neural folds Neural groove
The neural plate invaginates, forming the neural groove, flanked by neural folds. 2
Figure 12.1, step 2

14. Embryonic Development don’t copy
Neural groove fuses dorsally to form the neural tube
Neural tube gives rise to the brain and spinal cord

15. Neural crest 3
Neural fold cells migrate to form the neural crest, which will form much of the PNS and many other structures.
Figure 12.1, step 3

16. Head Surface ectoderm Neural tube Tail
The neural groove becomes the neural tube, which will form CNS structures. 4
Figure 12.1, step 4

17. Anterior (rostral) Posterior (caudal) Metencephalon Mesencephalon
Midbrain
Diencephalon
Flexures
Cervical
Telencephalon
Spinal cord
Myelencephalon
(a) Week 5
Figure 12.3a

18. Outline of diencephalon
Cerebral hemisphere
Outline of diencephalon
Midbrain
Cerebellum
Pons
Medulla oblongata
Spinal cord
(b) Week 13
Figure 12.3b

19. Cerebral hemisphere Cerebellum Pons Medulla oblongata Spinal cord
(c) Week 26
Figure 12.3c

21. *Regions and Organization of the CNS
Adult brain regions
Cerebral hemispheres
Diencephalon
Brain stem (midbrain, pons, and medulla)
Cerebellum

22. Cerebral hemisphere Diencephalon Cerebellum Brain stem • Midbrain
• Pons
• Medulla oblongata
(d) Birth
Figure 12.3d

23. Regions and Organization of the CNS
Spinal cord
Central cavity surrounded by a gray matter core
External white matter composed of myelinated fiber tracts

24. Regions and Organization of the CNS
Brain
Similar pattern with additional areas of gray matter
Nuclei in cerebellum and cerebrum
Cortex of cerebellum and cerebrum

25. Central cavity Cortex of gray matter Migratory pattern of neurons
Inner gray
matter
Cerebrum
Outer white
matter
Cerebellum
Gray matter
Region of cerebellum
Central cavity
Inner gray matter
Outer white matter
Gray matter
Brain stem
Central cavity
Outer white matter
Inner gray matter
Spinal cord
Figure 12.4

26. Ventricles of the Brain
Connected to one another and to the central canal of the spinal cord
Lined by ependymal cells

27. Ventricles of the Brain
Contain cerebrospinal fluid
Two C-shaped lateral ventricles in the cerebral hemispheres
Third ventricle in the diencephalon
Fourth ventricle in the hindbrain, dorsal to the pons, develops from the lumen of the neural tube

28. Lateral ventricle Septum pellucidum Anterior horn Posterior horn
Inferior
horn
Interventricular
foramen
Lateral
aperture
Median
aperture
Third ventricle
Inferior horn
Lateral
aperture
Cerebral aqueduct
Fourth ventricle
Central canal
(a) Anterior view
(b) Left lateral view
Figure 12.5

29. *Cerebral Hemispheres
Surface markings
Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures)
Five lobes
Frontal
Parietal
Temporal
Occipital
Insula

30. *Cerebral Hemispheres
Surface markings
Central sulcus
Separates the precentral gyrus of the frontal lobe and the postcentral gyrus of the parietal lobe
Longitudinal fissure
Separates the two hemispheres
Transverse cerebral fissure
Separates the cerebrum and the cerebellum
PLAY
Animation: Rotatable brain

31. Parieto-occipital sulcus (on medial surface of hemisphere)
Precentral
gyrus
Central
sulcus
Postcentral
gyrus
Frontal
lobe
Parietal lobe
Parieto-occipital sulcus
(on medial surface
of hemisphere)
Lateral sulcus
Occipital lobe
Temporal lobe
Transverse cerebral fissure
Cerebellum
Pons
Medulla oblongata
Fissure
Spinal cord
(a deep
sulcus)
Gyrus
Cortex (gray matter)
Sulcus
White matter
(a)
Figure 12.6a

32. Central sulcus Frontal lobe Gyri of insula Temporal lobe (pulled down)
Figure 12.6b

33. Anterior Longitudinal Frontal lobe fissure Cerebral veins and arteries
covered by
arachnoid
mater
Parietal
lobe
Left cerebral
hemisphere
Right cerebral
hemisphere
Occipital
lobe
(c)
Posterior
Figure 12.6c

34. Left cerebral hemisphere Transverse cerebral fissure Brain stem
Cerebellum
(d)
Figure 12.6d

35. *Cerebral Cortex Thin (2–4 mm) superficial layer of gray matter
40% of the mass of the brain
Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding
Each hemisphere connects to contralateral side of the body
There is lateralization of cortical function in the hemispheres

36. *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
Conscious behavior involves the entire cortex

37. Cerebral hemisphere Septum pellucidum Corpus callosum Interthalamic
adhesion
(intermediate
mass of
thalamus)
Fornix
Choroid plexus
Thalamus
(encloses third
ventricle)
Interven-
tricular
foramen
Posterior commissure
Pineal gland
(part of epithalamus)
Anterior
commissure
Corpora
quadrigemina
Mid-
brain
Hypothalamus
Cerebral
aqueduct
Optic chiasma
Arbor vitae (of
cerebellum)
Pituitary gland
Fourth ventricle
Mammillary body
Choroid plexus
Pons
Cerebellum
Medulla oblongata
Spinal cord
Figure 12.12

38. *Motor Areas Primary (somatic) motor cortex Premotor cortex
Broca’s area
Frontal eye field

39. Sensory areas and related association areas Primary motor cortex
Motor areas
Central sulcus
Sensory areas and related
association areas
Primary motor cortex
Primary somatosensory
cortex
Premotor cortex
Somatic
sensation
Frontal eye field
Somatosensory
association cortex
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Taste
Prefrontal cortex
Working memory
for spatial tasks
Wernicke’s area
(outlined by dashes)
Executive area for
task management
Working memory for
object-recall tasks
Primary visual
cortex
Visual
association
area
Vision
Solving complex,
multitask problems
Auditory
association area
Hearing
Primary
auditory cortex
(a) Lateral view, left cerebral hemisphere
Primary motor cortex
Motor association cortex
Primary sensory cortex
Sensory association cortex
Multimodal association cortex
Figure 12.8a

40. *Primary Motor Cortex
Allows conscious control of precise, skilled, voluntary movements
Motor homunculi: upside-down caricatures representing the motor innervation of body regions

41. Posterior
Motor
Motor map in
precentral gyrus
Anterior
Toes
Jaw
Tongue
Primary motor
cortex
(precentral gyrus)
Swallowing
Figure 12.9

42. *Premotor Cortex Anterior to the precentral gyrus
Controls learned, repetitious, or patterned motor skills
Coordinates simultaneous or sequential actions
Involved in the planning of movements that depend on sensory feedback

43. *Broca’s Area Anterior to the inferior region of the premotor area
Present in one hemisphere (usually the left)
A motor speech area that directs muscles of the tongue
Is active as one prepares to speak

44. *Frontal Eye Field
Anterior to the premotor cortex and superior to Broca’s area
Controls voluntary eye movements

45. Sensory areas and related association areas Primary motor cortex
Motor areas
Central sulcus
Sensory areas and related
association areas
Primary motor cortex
Primary somatosensory
cortex
Premotor cortex
Somatic
sensation
Frontal eye field
Somatosensory
association cortex
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Taste
Prefrontal cortex
Working memory
for spatial tasks
Wernicke’s area
(outlined by dashes)
Executive area for
task management
Working memory for
object-recall tasks
Primary visual
cortex
Visual
association
area
Vision
Solving complex,
multitask problems
Auditory
association area
Hearing
Primary
auditory cortex
(a) Lateral view, left cerebral hemisphere
Primary motor cortex
Motor association cortex
Primary sensory cortex
Sensory association cortex
Multimodal association cortex
Figure 12.8a

46. *Primary Somatosensory Cortex
In the postcentral gyri
Receives sensory information from the skin, skeletal muscles, and joints
Capable of spatial discrimination: identification of body region being stimulated

47. Posterior
Sensory
Anterior
Sensory map in
postcentral gyrus
Genitals
Primary somato-
sensory cortex
(postcentral gyrus)
Intra-
abdominal
Figure 12.9

48. Sensory areas and related association areas Primary motor cortex
Motor areas
Central sulcus
Sensory areas and related
association areas
Primary motor cortex
Primary somatosensory
cortex
Premotor cortex
Somatic
sensation
Frontal eye field
Somatosensory
association cortex
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Taste
Prefrontal cortex
Working memory
for spatial tasks
Wernicke’s area
(outlined by dashes)
Executive area for
task management
Working memory for
object-recall tasks
Primary visual
cortex
Visual
association
area
Vision
Solving complex,
multitask problems
Auditory
association area
Hearing
Primary
auditory cortex
(a) Lateral view, left cerebral hemisphere
Primary motor cortex
Motor association cortex
Primary sensory cortex
Sensory association cortex
Multimodal association cortex
Figure 12.8a

49. Primary somatosensory cortex
Cingulate
gyrus
Primary
motor cortex
Premotor cortex
Central sulcus
Corpus
callosum
Primary somatosensory
cortex
Frontal eye field
Parietal lobe
Somatosensory
association cortex
Prefrontal
cortex
Parieto-occipital
sulcus
Occipital
lobe
Processes emotions
related to personal
and social interactions
Visual
association
area
Orbitofrontal
cortex
Olfactory bulb
Olfactory tract
Primary
visual cortex
Fornix
Temporal lobe
Uncus
Calcarine sulcus
Primary
olfactory cortex
Parahippocampal
gyrus
(b) Parasagittal view, right hemisphere
Primary motor cortex
Motor association cortex
Primary sensory cortex
Sensory association cortex
Multimodal association cortex
Figure 12.8b