Chapter 12: The Central Nervous System

Question 1

4 regions of the brain

Answer 1

1. Cerebrum: 2 cerebral hemispheres (right & left)
2. Diencephalon
3. Brain Stem
4. Cerebellum: small brain, 2 hemispheres

Question 2

Brain stem consists of:

Answer 2

• midbrain
• pons
• medulla

Question 3

Cerebrum surface structures

Answer 3

• gyri; gyrus
• sulci; sulcus
• fissure

Question 4

Cerebrum surface structures: Gyri

Answer 4

elevated ridges

Question 5

Cerebrum surface structures: sulci

Answer 5

• shallow grooves
• some sulci are landmarks for dividing each hemisphere into 5 lobes

Question 6

Cerebrum surface structures: fissure

Answer 6

• deep grooves
• longitudinal fissure: separates right from left hemisphere
• transverse cerebral fissure: separates cerebrum from underlying cerebellum

Question 7

Hypothalamus

Answer 7

• main visceral control center; vital in maintaining homeostasis
• has many important nuclei: ex. mammillary bodies: acts as olfactory relay station
• primary homeostatic functions: controls ANS, physical response to emotions, body temp, hunger, water balance and thirst, sleep-wake cycle, control endocrine system: produces ADH and oxytocin

Question 8

Infindulum

Answer 8

stalk at base of hypothalamus that connects to pituitary gland

Question 9

Thalamus

Answer 9

• 80% of diencephalon
• relay station that sorts info traveling to cerebral cortex, info stored and edited before relayed
• mediates sensation, motor activities, cortical arousal, learning, memory
• involved in memory processing

Question 10

Medulla Oblongata

Answer 10

• decussation of pyramids
• origin of VII, IX, X, XII cranial nerves
• brain stem: has autonomic reflex center, involved in maintaining homeostasis
• relays ascending sensory pathway impulses from skin and proprioceptors through nuclei cuneatus and gracile
• contains visceral nuclei controlling heart rate, blood vessel diameter, respiratory rate, vomiting, coughing, etc.

Question 11

Medulla oblongata: Decussation of Pyramids

Answer 11

• spot where pyramidal tracts cross over another to opposite side of body: why each cerebral hemisphere control movement on opposite side of body

Question 12

Medulla Oblongata: vital centers

Answer 12

• cardiovascular: adjusts rate and force of contractions, vasomotor center changes blood vessel diameter to control bp
• respiratory center: generates rhythm of respiration, controls rate and depth of breathing
• other centers control vomiting, hiccuping,swallowing, coughing, sneezing

Question 13

Cerebellum

Answer 13

• “small brain”
• processes input from cerebral cortex, brain stem, and sensory receptors to provide precise, smooth, coordinated movements of skeletal muscles
• responsible for balance and posture

Question 14

Limbic System

Answer 14

• group of medial cerebral hemispheres and diencephalon that collectively work together
• emotional-visceral brain (aka affective brain: responds to perceived threats, express emotion through gestures, resolve mental conflict, attach emotional response to odors
• mediates emotional response
• involved in memory processing

Question 15

Reticular formation

Answer 15

• groups of nuclei running through central core of brain stem
• governs brain arousal via reticular activating system
• maintains cerebral cortical alertness (RAS)
• filters out receptive stimuli
• helps regulate skeletal and visceral muscle activity

Question 16

Primary somatosensory cortex

Answer 16

• receives sensory info from the skin and proprioceptors found in skeletal muscle, joints, and tendons: proprioceptors tell the brain the body’s positioning in space
• uses sensory info to identify what part of body stimulated (spatial discrimination)

Question 16

Primary motor cortex

Answer 16

allows conscious control or precise, skilled, skeletal muscle movement (voluntary muscle control)

Question 16

Broca’s area: function and location

Answer 16

• typically present only in one hemisphere (usually left)
• motor speech area- controls muscles used in producing speech
• also used when planning/preparing to speak
• control voluntary movements of the eye

Question 16

Anterior association area

Answer 16

• involved in intellect, cognition (complex learning activities), recall, and personality
• working memory found here: needed for abstract ideas, judgment, reasoning, persistence, and planning

Question 17

Wernicke’s area: function & location

Answer 17

• posterior association area
• involved in understanding written and spoken language
• if damaged: fail to recognize body on opposite side of damage as part of their body

Question 17

Commissural fibers: main one and location

Answer 17

main one: corpus callosum commissural fibers that connect 2 hemispheres (center of the brain between right and left hemispheres)
* horizontal
* connect gray matter of 2 hemispheres

Question 18

Structures protecting the brain

Answer 18

• 3 meninges (connective tissue membranes covering CNS): dura mater, arachnoid mater, pia mater
• cerebrospinal fluid (CSF)
• blood brain barrier

Question 19

Meninge 1: Dura mater

Answer 19

• “tough mother”
• stronger, most external
• periosteal layer: outer layer, attached to periosteum of skull
• meningeal layer: inner layer, true external covering of brain
• layers fused except at dural venous sinuses between layers
• extends forward, forming partitions (dural septa) that divide cranial cavity

Question 19

Meninge 3: Pia mater

Answer 19

• “gentle mother”
• delicate layer of connective tissue, most internal
• clings tightly to the brain along every gyrus and down each sulcus
• has numerous tiny blood vessels supplying the brain

Question 19

Meninge 2: arachnoid mater

Answer 19

* middle meninges layer; subdural space separates arachnoid mater from dura mater; arachnoid granulation (villi) protrude into superior sagittal sinus so CSF can be reabsorbed * underneath arachnoid mater is subarachnoid space which contains CSF and the largest blood vessels supplying the brain

Question 20

Formation of CSF

Answer 20

* choroid plexus of each ventricle produces CSF * CSF flows thru ventricles into subarachnoid space via median lateral apertures * CSF flows through subarachnoid space * CSF is absorbed into dural venous sinuses via arachnoid granulations

Question 20

Blood Brain Barrier: components

Answer 20

* tight junctions: between capillary endothelial cells: most important because they prevent substances from squeezing between endothelial cells, anything crossing the BBB must go thru an endothelial cell * astrocytes: help maintain tight junctions * basement membrane: surrounds endothelial cells

Question 21

Spinal cord: gross anatomy

Answer 21

* spinal dura mater is not fused to vertebrae * epidural space: between vertebrae and spinal dura. fat padding with network of veins * CSF in subarachnoid space between arachnoid and pia mater * dural and arachnoid membranes extend beyond the end of spinal cord at L1/L2 own to S2 of sacrum: lumbar puncture or spinal tap procedure tiste below L1/L2 because no spinal cord here to damage

Question 22

Spinal cord: where does it begin/end

Answer 22

* end tapers to conus medullaris; cone-shaped structure marking end of spinal cord * spinal nerves (31 pairs) branch off spinal cord * spinal cord begins at base of skull at foramen magnum

Question 23

Spinal cord: cross-section anatomy

Answer 23

* central canal: filled with CSF, runs length of spinal cord * Gray matter: forms butterfly shape in center

Question 24

Spinal cord cross-section anatomy Gray matter

Answer 24

* dorsal horn (posterior) * ventral horn (anterior) * lateral horns (only in thoracic and lumbar regions)

Question 25

Cross-section anatomy roots and nerves

Answer 25

* ventral roots: motor neuron axon bundles exiting spinal cord * dorsal roots: sensory input to spinal cord * dorsal roots (spinal) ganglia: sensory neuron cell bodies * spinal nerves: formed by fusion of ventral and dorsal roots

Question 26

Ascending pathways vs descending pathways: what do they od

Answer 26

conduct sensory pathways superiorly through a chain of 3 neurons to the brain: first-order neurons second-order neurons third-order neurons

Question 27

First-order neurons

Answer 27

impulses conducted from cutaneous receptors and proprioceptors to spinal cord or brain stem where they synapse with second-order neurons

Question 28

Second-order neurons

Answer 28

* interneurons * in dorsal horn of spinal cord or medullary nuclei; axons extend and transmit impulses to cerebellum or synapse with 3rd order neuron in thalamus

Question 29

Third-order neurons

Answer 29

* interneurons * cell bodies in thalamus * axons extend and transmit impulses to somatosensory cortex * none in the cerebellum

Question 30

3 pathways that transmit somatosensory info to the brain

Answer 30

1. dorsal column-medial lemniscal pathways 2. spinothalamic pathways 3. spinocerebellar tracts

Question 31

Dorsal column-medial lemniscal pathways

Answer 31

* impulses relayed through thalamus to somatosensory cortex * relays discriminative touch, vibration, and info from proprioceptors

Question 32

Spinothalamic Pathways

Answer 32

* impulses relayed through thalamus to somatosensory cortex * transmit pain, temp, coarse touch, and pressure

Question 33

Spinocerebellar tracts

Answer 33

transmit info about muscle or tendon stretch to cerebellum, which then coordinates skeletal muscle activity