the central nervous system 1

Question 1

cephalization

Answer 1

evolutionary development of the rostral (anterior) portion CNS - results in an increased number of neurons

Question 2

4 regions of the adult brain

Answer 2

• cerebrum (2 hemispheres)
• diencephalon
• brain stem (midbrain, pons, medulla oblongata)
• berebellum

Question 3

gray matter

Answer 3

short, non mylinated neurons + cell bodies

Question 4

white matter

Answer 4

mostly myelinated axons, some nonmyelinated axons, primarily organized in fiber tracts

Question 5

basic pattern of the CNS

Answer 5

central cavity surrounded by gray matter with white matter external to the gray matter - this pattern is seen in the spinal cord
- the brain stem has additional gray matter nuclei scattered within the white matter
- the cerebral hemispheres and cerebellum contain an outer layer of gray matter (the cortex)

Question 6

ventricles

Answer 6

fluid filled chambers
- filled with cerebrospinal fluid (CSF) and lined with ependymal cells
- the ventricles are continuous with one another and with the central canal of the spinal cord

Question 7

lateral ventricles

Answer 7

large, paired, c-shaped chambers, deep within each hemisphere
- each lateral ventricle is connected to the narrow 3rd ventricle via interventricular foramen
- the 3rd ventricle connects to the 4th ventricle cerebral aqueduct - the 4th ventricle is continuous with the central canal of the spinal cord

Question 8

3 openings that connect the 4th ventricle to the subarachnoid space

Answer 8

• paired lateral apertures
• 1 median aperture

Question 9

septum pellucidum

Answer 9

thin membrane that separates the lateral ventricles

Question 10

cerebral hemispheres surface markings

Answer 10

• gyri: ridges
• sulci: shallow grooves
• fissures: deep grooves

Question 11

longitudinal fissure

Answer 11

separates the 2 hemispheres

Question 12

transverse cerebral fissure

Answer 12

separates cerebrum and cerebellum

Question 13

5 cerebral hemispheres

Answer 13

• frontal
• parietal
• temporal
• occipital
• insula

Question 14

3 major sulci

Answer 14

• central sulcus: separates the precentral gyrus of the frontal lobe and the postcentral gyrus of the parietal lobe
• parieto-occipital sulcus: separates the occipital and parietal lobes
• lateral sulcus: outlines the temporal lobes

Question 15

3 basic regions of each cerebral hemisphere

Answer 15

• cerebral cortex: superficial gray matter
• internal white matter
• basal nuclei: islands of gray matter deep within white matter

Question 16

cerebral cortex

Answer 16

• The “executive suite” of the brain
• Thin (2-4mm), superficial layer of gray matter
• Site of the conscious mind: awareness, sensory perception, initiation of voluntary motor tasks, communication, memory storage, understanding
• Composed of neuron cell bodies, dendrites, glial cells, and blood vessels – no axons!
• Contains billions of neurons; accounts for 40% of the mass of the brain

Question 17

functional imaging

Answer 17

pet scans and/or functional MRI can show where specific motor and sensory functions
- show metabolic activity
- functional mris show blood flow

Question 18

domain

Answer 18

the place a particular motor or sensory function is localized
- the higher functions (memory, language, etc) are spread over multiple areas and in overlapping domains

Question 19

4 general considerations of the cerebral cortex

Answer 19

1.The cortex contains 3 types of functional areas:
- Motor Areas: control voluntary movement
- Sensory Areas: conscious awareness of sensation
- Association Areas: integrate diverse information
2. Each hemisphere is chiefly concerned with the sensory and motor functions of the contralateral (opposite) side of the body
3. Although largely symmetrical in structure, the two hemispheres are not identical in function
- Lateralization: specialization of cortical function in only one hemisphere
4. Conscious behaviors involve the entire cortex

Question 20

cerebral cortex: motor areas

Answer 20

The motor areas are located in the posterior part of the frontal lobe. They control most voluntary movement.
- Primary Motor Cortex: located in the precentral gyrus
- Premotor Cortex: anterior to the precentral gyrus
- Broca’s Area: anterior and inferior to the premotor cortex
- Frontal Eye Field: within and anterior to the premotor cortex; superior to Broca’s area

Question 21

cerebral cortex: the primary motor cortex

Answer 21

The primary motor cortex is in the precentral gyrus of the frontal lobe
- Pyramidal Cells: large neurons that allow conscious control of precise, skilled skeletal muscle movements
- Pyramidal (Corticospinal) Tracts: formed from the long axons of the pyramidal cells that project down to the spinal cord
- Somatotopy: all specific areas of the body can be mapped to specific areas on the primary motor cortex
- Motor Homunculi: upside-down, caricature-like representation of the motor innervation of the contralateral body regions

Question 22

Cerebral Cortex: Other Motor Areas

Answer 22

Premotor Cortex
- Helps to plan movements – a “staging area”
- Selects + sequences basic motor movements into more complex tasks
- Uses highly processed sensory information to control voluntary actions
- Sends activating impulses to the primary motor cortex
Broca’s Area
- Present in only 1 hemisphere – usually the left
- Motor speech area – directs the muscles of speech production
- Active in planning speech and other voluntary motor activities
Frontal Eye Field
- Located partially in and anterior to the premotor cortex
- Controls voluntary eye movements

Question 23

damage to the primary motor cortex

Answer 23

– as seen in strokes – paralyzes the muscles controlled by those areas
- Paralysis will occur on the opposite side of the body from the cortical damage
- Only voluntary control is lost – the muscles can still contract reflexively

Question 24

Damage to the premotor cortex

Answer 24

results in loss of the motor skills programmed by that region, but it does not impair muscle strength or the ability to perform discrete, individual movements
- Other premotor neurons can be reprogrammed to take over the skill of the damaged neurons, but this requires significant patience and practice

Question 25

Cerebral Cortex: Sensory Areas

Answer 25

• Sensory areas are areas of the cortex concerned with the conscious awareness of sensation
• Sensory areas occur in the parietal, insular, temporal, and occipital lobes
• 8 Main Sensory Areas: primary somatosensory cortex, somatosensory association cortex, visual areas, auditory areas, vestibular cortex, olfactory cortex, gustatory cortex, and visceral sensory areas

Question 26

cerebral cortex sensory areas: primary somatosensory cortex

Answer 26

• Located in postcentral gyrus of the parietal lobe
• Receives general sensory information from skin and the proprioceptors of skeletal muscle, joints, and tendons
• Capable of spatial discrimination: identification of body region being stimulated

Question 27

cerebral cortex sensory areas: somatosensory homunculus

Answer 27

the body is represented by upside-down caricatures that represent contralateral sensory input

Question 28

cerebral cortex sensory areas: Somatosensory Association Cortex

Answer 28

• Posterior to the primary somatosensory cortex
• Integrates the sensory inputs relayed to it from the primary somatosensory cortex to provide an understanding of an object being felt - determines size, texture, and relationship of the parts

Question 29

cerebral cortex sensory areas: Primary Visual (Striate) Cortex

Answer 29

located on the extreme posterior tip of the occipital lobe, but most of it is buried in the calcarine sulcus
- Largest cortical sensory area
- Receives visual information that originates on the retinas
- The visual space on the opposite side of the body is mapped to the primary visual cortex

Question 30

cerebral cortex sensory areas: Visual Association Area

Answer 30

• Covers much of the occipital lobe and communicates with the primary visual cortex
• Uses past visual experiences to interpret visual stimuli (color, form, or movement) Ex: ability to recognize faces
• Complex processing involves entire posterior half of cerebral hemisphere

Question 31

Cerebral Cortex: Sensory Areas: Primary Auditory Cortex

Answer 31

located in the superior margin of the temporal lobes
- Interprets information from the sound receptors in the inner ear – determines pitch, loudness, and location

Question 32

Cerebral Cortex: Sensory Areas: Auditory association area

Answer 32

located posterior to primary auditory cortex
- Stores memory of sounds, and permits perception of the sound stimulus

Answer 33

Vestibular Cortex: posterior portion of insula and adjacent parietal cortex
- Responsible for conscious awareness of balance (position of the head in space)
Primary Olfactory Cortex: medial aspect of the temporal lobes (the piriform lobes)
- Part of primitive rhinencephalon – along with the olfactory bulbs and tracts. In humans, the remainder of the rhinencephalon becomes part of the limbic system.
- Involved in conscious awareness of odors
- Receives impulses from the superior nasal cavity
Gustatory Cortex: in the insula – deep to the temporal lobe
- Involved in perceiving taste stimuli
Visceral Sensory Area: posterior to the gustatory cortex
- Provides conscious perception of visceral sensations - ex: upset stomach or full bladder