PPT Notes Chapter 12

Question 1

Central Nervous System (CNS)

Answer 1

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

Question 2

Background: Embryonic Development

Answer 2

Neural groove fuses dorsally to form the neural tube
Neural tube gives rise to the brain and spinal cord

Anterior end of the neural tube gives rise to three primary brain vesicles
Prosencephalon—forebrain
Mesencephalon—midbrain
Rhombencephalon—hindbrain

Question 3

Background: Effect of Space Restriction on Brain Development
Midbrain flexure and cervical flexure cause forebrain to move toward the brain stem
Cerebral hemispheres grow posteriorly and laterally
Cerebral hemisphere surfaces crease and fold into convolutions

Answer 3

Midbrain flexure and cervical flexure cause forebrain to move toward the brain stem
Cerebral hemispheres grow posteriorly and laterally
Cerebral hemisphere surfaces crease and fold into convolutions

Question 4

Regions and Organization of the CNS

Answer 4

Adult brain regions
Cerebral hemispheres
Diencephalon
Brain stem (midbrain, pons, and medulla)
Cerebellum
Spinal cord 
Central cavity surrounded by a gray matter core 
External white matter composed of myelinated fiber tracts

REMEMBER! Gray matter interprets, white matter transmits!!
Brain
Similar pattern with additional areas of gray matter
Nuclei in cerebellum and cerebrum
Cortex of cerebellum and cerebrum

Question 5

Ventricles of the Brain

Answer 5

Connected to one another and to the central canal of the spinal cord
Lined by ependymal cells
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

Question 6

Cerebral Hemispheres: Important!!

Answer 6

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

Question 7

Cerebral Cortex

Answer 7

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 [right brain/left brain]

Question 8

Functional Areas of the Cerebral Cortex

Answer 8

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

Question 9

Motor Areas

Answer 9

Primary (somatic) motor cortex
Premotor cortex
Broca’s area
Frontal eye field

Question 10

Primary Motor Cortex

Answer 10

Large pyramidal cells of the precentral gyri
Long axons  pyramidal (corticospinal) tracts
Allows conscious control of precise, skilled, voluntary movements
Motor homunculi: upside-down caricatures representing the motor innervation of body regions

Question 11

Premotor Cortex

Answer 11

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

Question 12

Broca’s Area

Answer 12

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

Question 13

Frontal Eye Field

Answer 13

Anterior to the premotor cortex and superior to Broca’s area

Controls voluntary eye movements

Question 14

Sensory Areas

Answer 14

Primary somatosensory cortex
Somatosensory association cortex
Visual areas
Auditory areas

Question 15

Primary Somatosensory Cortex

Answer 15

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

Question 16

Somatosensory Association Cortex

Answer 16

Posterior to the primary somatosensory cortex
Integrates sensory input from primary somatosensory cortex
Determines size, texture, and relationship of parts of objects being felt

Question 17

Visual Areas

Answer 17

Primary visual (striate) cortex
Extreme posterior tip of the occipital lobe
Receives visual information from the retinas
Visual association area
Surrounds the primary visual cortex
Uses past visual experiences to interpret visual stimuli (e.g., color, form, and movement)
Complex processing involves entire posterior half of the hemispheres

Question 18

Auditory Areas

Answer 18

Primary auditory cortex
Superior margin of the temporal lobes
Interprets information from inner ear as pitch, loudness, and location
Auditory association area
Located posterior to the primary auditory cortex
Stores memories of sounds and permits perception of sounds

Question 19

OIfactory Cortex

Answer 19

Medial aspect of temporal lobes (in piriform lobes)
Part of the primitive rhinencephalon, along with the olfactory bulbs and tracts
(Remainder of the rhinencephalon in humans is part of the limbic system)
Region of conscious awareness of odors

Question 20

Gustatory Cortex

Answer 20

In the insula

Involved in the perception of taste

Question 21

Visceral Sensory Area

Answer 21

Posterior to gustatory cortex

Conscious perception of visceral sensations, e.g., upset stomach or full bladder

Question 22

Vestibular Cortex

Answer 22

Posterior part of the insula and adjacent parietal cortex

Responsible for conscious awareness of balance (position of the head in space)

Question 23

Multimodal Association Areas

Answer 23

Receive inputs from multiple sensory areas
Send outputs to multiple areas, including the premotor cortex
Allow us to give meaning to information received, store it as memory, compare it to previous experience, and decide on action to take
There are several multimodal association areas.

Question 24

Limbic Association Area

Answer 24

Part of the limbic system

Provides emotional impact that helps establish memories

Question 25

Lateralization of Cortical Function

Answer 25

Lateralization Division of labor between hemispheres Cerebral dominance Designates the hemisphere dominant for language (left hemisphere in 90% of people) Left hemisphere Controls language, math, and logic Right hemisphere Insight, visual-spatial skills, intuition, and artistic skills Left and right hemispheres communicate via fiber tracts in the cerebral white matter

Question 26

Cerebral White Matter

Answer 26

Myelinated fibers and their tracts Responsible for communication Commissures (in corpus callosum)—connect gray matter of the two hemispheres Association fibers—connect different parts of the same hemisphere Projection fibers—(corona radiata) connect the hemispheres with lower brain or spinal cord

Question 27

Basal Nuclei (Ganglia)

Answer 27

Subcortical nuclei [islands within white matter] Consists of the corpus striatum Caudate nucleus Lentiform nucleus (putamen + globus pallidus) Functionally associated with the subthalamic nuclei (diencephalon) and the substantia nigra (midbrain)

Question 28

Functions of Basal Nuclei

Answer 28

Though somewhat elusive, the following are thought to be functions of basal nuclei Influence muscular control Help regulate attention and cognition Regulate intensity of slow or stereotyped movements Inhibit antagonistic and unnecessary movements

Question 29

Diencephalon

Answer 29

``` Three paired structures Thalamus Hypothalamus Epithalamus Encloses the third ventricle ```

Question 30

Thalamus

Answer 30

80% of diencephalon Superolateral walls of the third ventricle Connected by the interthalamic adhesion (intermediate mass) Contains several nuclei, named for their location Nuclei project and receive fibers from the cerebral cortex

Question 31

Thalamic Function

Answer 31

Gateway to the cerebral cortex Sorts, edits, and relays information Afferent impulses from all senses and all parts of the body Impulses from the hypothalamus for regulation of emotion and visceral function Impulses from the cerebellum and basal nuclei to help direct the motor cortices Mediates sensation, motor activities, cortical arousal, learning, and memory

Question 32

Hypothalamus

Answer 32

Forms the inferolateral walls of the third ventricle Contains many nuclei Example: mammillary bodies Paired anterior nuclei Olfactory relay stations Infundibulum—stalk that connects to the pituitary gland

Question 33

Hypothalamic Function

Answer 33

Autonomic control center for many visceral functions (e.g., blood pressure, rate and force of heartbeat, digestive tract motility) Center for emotional response: Involved in perception of pleasure, fear, and rage and in biological rhythms and drives Regulates body temperature, food intake, water balance, and thirst Regulates sleep and the sleep cycle Controls release of hormones by the anterior pituitary Produces posterior pituitary hormones

Question 34

Epithalamus

Answer 34

Most dorsal portion of the diencephalon; forms roof of the third ventricle Pineal gland—extends from the posterior border and secretes melatonin Melatonin—helps regulate sleep-wake cycles

Question 35

Brain Stem

Answer 35

Three regions Midbrain Pons Medulla oblongata Similar structure to spinal cord but contains embedded nuclei Controls automatic behaviors necessary for survival Contains fiber tracts connecting higher and lower neural centers Associated with 10 of the 12 pairs of cranial nerves

Question 36

Midbrain

Answer 36

Located between the diencephalon and the pons Cerebral peduncles Contain pyramidal motor tracts Cerebral aqueduct Channel between third and fourth ventricles

Question 37

Pons

Answer 37

Forms part of the anterior wall of the fourth ventricle Fibers of the pons Connect higher brain centers and the spinal cord Relay impulses between the motor cortex and the cerebellum Origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial) Some nuclei of the reticular formation Nuclei that help maintain normal rhythm of breathing

Question 38

Medulla Oblongata

Answer 38

Joins spinal cord at foramen magnum Forms part of the ventral wall of the fourth ventricle Contains a choroid plexus of the fourth ventricle Pyramids—two ventral longitudinal ridges formed by pyramidal fiber tracts Functions to relay sensory information from muscles and joints to cerebellum Cranial nerves VIII, X, and XII are associated with the medulla mediates responses that maintain equilibrium Autonomic reflex centers Cardiovascular center Cardiac center adjusts force and rate of heart contraction Vasomotor center adjusts blood vessel diameter for blood pressure regulation Respiratory centers Generate respiratory rhythm Control rate and depth of breathing, with pontine centers Additional centers regulate Vomiting Hiccuping Swallowing Coughing Sneezing

Question 39

The Cerebellum

Answer 39

11% of brain mass Dorsal to the pons and medulla Subconsciously provides precise timing and appropriate patterns of skeletal muscle contraction

Question 40

Anatomy of the Cerebellum

Answer 40

Two hemispheres connected by vermis Each hemisphere has three lobes Anterior, posterior, and flocculonodular Folia—transversely oriented gyri Arbor vitae—distinctive treelike pattern of the cerebellar white matter

Question 41

Cerebellar Peduncles

Answer 41

All fibers in the cerebellum are ipsilateral Three paired fiber tracts connect the cerebellum to the brain stem Superior peduncles connect the cerebellum to the midbrain Middle peduncles connect the pons to the cerebellum Inferior peduncles connect the medulla to the cerebellum

Question 42

Cerebellar Processing for Motor Activity

Answer 42

Cerebellum receives impulses from the cerebral cortex of the intent to initiate voluntary muscle contraction Signals from proprioceptors and visual and equilibrium pathways continuously “inform” the cerebellum of the body’s position and momentum Cerebellar cortex calculates the best way to smoothly coordinate a muscle contraction A “blueprint” of coordinated movement is sent to the cerebral motor cortex and to brain stem nuclei

Question 43

Cognitive Function of the Cerebellum

Answer 43

Recognizes and predicts sequences of events during complex movements Plays a role in nonmotor functions such as word association and puzzle solving

Question 44

Protection of the Brain

Answer 44

Bone (skull) Membranes (meninges) Watery cushion (cerebrospinal fluid) Blood-brain barrier

Question 45

Meninges

Answer 45

``` Cover and protect the CNS Protect blood vessels and enclose venous sinuses Contain cerebrospinal fluid (CSF) Form partitions in the skull Three layers Dura mater Arachnoid mater Pia mater ```

Question 46

Dura Mater

Answer 46

Strongest meninx | Two layers of fibrous connective tissue (around the brain) separate to form dural sinuses

Question 47

Arachnoid Mater

Answer 47

Middle layer with weblike extensions Separated from the dura mater by the subdural space Subarachnoid space contains CSF and blood vessels Arachnoid villi protrude into the superior sagittal sinus and permit CSF reabsorption

Question 48

Pia Mater

Answer 48

Layer of delicate vascularized connective tissue that clings tightly to the brain

Question 49

Cerebrospinal Fluid (CSF)

Answer 49

Composition Watery solution Less protein and different ion concentrations than plasma Constant volume Functions Gives buoyancy to the CNS organs Protects the CNS from blows and other trauma Nourishes the brain and carries chemical signals

Question 50

Choroid Plexuses

Answer 50

Produce CSF at a constant rate Hang from the roof of each ventricle Clusters of capillaries enclosed by pia mater and a layer of ependymal cells Ependymal cells use ion pumps to control the composition of the CSF and help cleanse CSF by removing wastes

Question 51

Blood-Brain Barrier

Answer 51

Helps maintain a stable environment for the brain Separates neurons from some bloodborne substances Composition Continuous endothelium of capillary walls Basal lamina Feet of astrocytes Provide signal to endothelium for the formation of tight junctions

Question 52

Blood-Brain Barrier: Functions

Answer 52

Selective barrier Allows nutrients to move by facilitated diffusion Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics Absent in some areas, e.g., vomiting center and the hypothalamus, where it is necessary to monitor the chemical composition of the blood

Question 53

Homeostatic Imbalances of the Brain

Answer 53

Traumatic brain injuries Concussion—temporary alteration in function Contusion—permanent damage Subdural or subarachnoid hemorrhage—may force brain stem through the foramen magnum, resulting in death Cerebral edema—swelling of the brain associated with traumatic head injury Cerebrovascular accidents (CVAs)(strokes) Blood circulation is blocked and brain tissue dies, e.g., blockage of a cerebral artery by a blood clot Typically leads to hemiplegia, or sensory and speed deficits Transient ischemic attacks (TIAs)—temporary episodes of reversible cerebral ischemia Tissue plasminogen activator (TPA) is the only approved treatment for stroke Degenerative brain disorders Alzheimer’s disease (AD): a progressive degenerative disease of the brain that results in dementia Parkinson’s disease: degeneration of the dopamine-releasing neurons of the substantia nigra Huntington’s disease: a fatal hereditary disorder caused by accumulation of the protein huntingtin that leads to degeneration of the basal nuclei and cerebral cortex

Question 54

Spinal Cord

Answer 54

``` Location Begins at the foramen magnum Ends as conus medullaris at L1 vertebra Functions Provides two-way communication to and from the brain Contains spinal reflex centers Spinal nerves 31 pairs Cervical and lumbar enlargements The nerves serving the upper and lower limbs emerge here Cauda equina The collection of nerve roots at the inferior end of the vertebral canal ```

Question 55

Spinal Cord: Protection

Answer 55

Bone, meninges, and CSF Cushion of fat and a network of veins in the epidural space between the vertebrae and spinal dura mater CSF in subarachnoid space

Question 56

Cross-Sectional Anatomy

Answer 56

Two lengthwise grooves divide cord into right and left halves Ventral (anterior) median fissure Dorsal (posterior) median sulcus Gray commissure—connects masses of gray matter; encloses central canal

Question 57

Gray Matter

Answer 57

``` Dorsal horns—interneurons that receive somatic and visceral sensory input Ventral horns—somatic motor neurons whose axons exit the cord via ventral roots Lateral horns (only in thoracic and lumbar regions) –sympathetic neurons Dorsal root (spinal) gangia—contain cell bodies of sensory neurons ```

Question 58

White Matter

Answer 58

``` Consists mostly of ascending (sensory) and descending (motor) tracts Transverse tracts (commissural fibers) cross from one side to the other Tracts are located in three white columns (funiculi on each side—dorsal (posterior), lateral, and ventral (anterior) Each spinal tract is composed of axons with similar functions ```

Question 59

Pathway Generalizations

Answer 59

Pathways decussate (cross over) Most consist of two or three neurons (a relay) Pathways are paired symmetrically (one on each side of the spinal cord or brain)

Question 60

Spinal Cord Trauma

Answer 60

Functional losses Parasthesias Sensory loss Paralysis Loss of motor function Flaccid paralysis—severe damage to the ventral root or ventral horn cells Impulses do not reach muscles; there is no voluntary or involuntary control of muscles Muscles atrophy Spastic paralysis—damage to upper motor neurons of the primary motor cortex Spinal neurons remain intact; muscles are stimulated by reflex activity No voluntary control of muscles Transection Cross sectioning of the spinal cord at any level Results in total motor and sensory loss in regions inferior to the cut Paraplegia—transection between T1 and L1 Quadriplegia—transection in the cervical region

Question 61

Amyotrophic Lateral Sclerosis (ALS)

Answer 61

Also called Lou Gehrig’s disease Involves progressive destruction of ventral horn motor neurons and fibers of the pyramidal tract Symptoms—loss of the ability to speak, swallow, and breathe Death typically occurs within five years Linked to glutamate excitotoxicity, attack by the immune system, or both