Chapter 12 - THE CENTRAL NERVOUS SYSTEM Flashcards
The central nervous system consists of what two things?
brain, spinal cord
What is cephalization?
an elaboration of the rostral, or anterior, portion of the CNS, along with an increase in neurons in the head
What does gray matter consist of?
short, nonmyelinated neurons and neuron cell bodies
What does white matter consist of?
1 - mostly myelinated axons
2 - some nonmyelinated axons (primarily in fiber tracts)
What is the basic pattern of the CNS?
central cavity surrounded by gray matter, external to which is white matter
Does the spinal cord exhibit normal pattern?
yes
Does the brain stem exhibit the normal pattern of the CNS?
sort of, it has additional gray matter scattered within the white matter
What is a cortex? Where is it located?
1 - an outer layer of gray matter
2 - cerebral hemispheres / cerebellum
What are the brain’s ventricles? What are the chambers filled/lined with?
1 - central hollow cavities within the brain
2 - filled with CSF; lined with ependymal cells
What are the lateral ventricles? What do they reflect?
1 - pair of large C-shaped chambers, one in each hemisphere
2 - the pattern of cerebral growth
What is the septum pellucidum?
a thin median membrane that separates the lateral ventricles
Each lateral ventricles communicates with what? Via what?
1 - third ventricle (in diencephalon)
2 - a channel called the interventricular foramen
The third ventricle is continuous with what? Via what?
1 - fourth ventricle
2 - a canal-like cerebral aqueduct that runs through the midbrain
The fourth ventricle lies where?
in the hindbrain dorsal to the pons and superior medulla
What 3 openings mark the walls of the fourth ventricle?
lateral apertures (side walls) and the median aperture (in the roof)
What is the subarachnoid space?
a fluid-filled space surrounding the brain
What are the elevated ridges called?
gyri
What are the shallow grooves in the brain called?
sulci
What are deep grooves in the brain called?
fissures
What does the longitudinal fissure do?
separates cerebral hemispheres
What does the transverse cerebral fissure do?
separates the cerebral hemispheres from the cerebellum
What does the central sulcus do?
it separates the frontal lobe from the parietal lobe
What borders the central sulcus?
the precentral gyrus and the postcentral gyrus
What separates the occipital lobe from the parietal lobe?
the parieto-occipital sulcus
What is buried deep within the lateral sulcus and forms part of its floor?
the insula
What houses the brainstem and the cerebellum?
The posterior cranial fossa
What structure enables us to be aware of ourselves and our sensations, to communicate, remember, understand, and initiate voluntary movements?
The cerebral cortex
Where is our conscious mind found?
The cerebral cortex
What is the cerebral cortex composed of?
Gray matter: neuron cell bodies, dendrites, associated glia and blood vessels, but no fiber tracts
The cerebral cortex account for how much of total brain mass?
40%
What are the three types of functional areas in the cerebral cortex?
1 - motor areas
2 - sensory areas
3 - associated areas
Where is the primary (somatic) motor cortex found?
In the precentral gyrus
What is the primary (somatic) motor cortex responsible for?
Conscious control of precise, skilled, skeletal muscle movements
Where is the premotor cortex found?
Anterior to the precentral gyrus
What is the premotor cortex responsible for?
1 - Planning movements; staging area for skilled motor activities
2 - controls voluntary actions that depend on sensory feedback
What is Broca’s area?
The motor-speech area that directs muscles of speech production
How many hemispheres is Broca’s area found in?
One, usually the left
What is the frontal eye field?
Controls voluntary eye movements
Where are the sensory areas of the cerebral cortex?
Parietal, insular, temporal, and occipital lobes
What receives general sensory information from skin, and proprioceptors of skeletal muscle, joints, and tendons?
Primary somatosensory cortex
The primary somatosensory cortex is capable of spatial discrimination. What is that?
Identification of body region being stimulated
What integrate sensory input from the primary somatosensory cortex for understanding?
The somatosensory association cortex
What visual area receives visual information from the retinas?
The primary visual (striate) cortex
What visual area uses past visual experiences to interpret a visual stimuli such as color, form, and movement?
The visual association area
What visual area has the ability to recognize faces?
The visual association area
What auditory area interprets information from the inner ear such as pitch, loudness, and location?
The primary auditory cortex
What auditorium area stores memories of sounds and permits perception of sound stimulus?
The auditory association area
What is the vestibular cortex responsible for?
Conscious awareness of balance (position of head in space)
What sensory area is responsible for the conscious awareness of odors?
The olfactory cortex
What sensory area is involved in the perception of taste?
The gustatory cortex
What is the visceral sensory area responsible for?
Conscious perception of visceral sensations; such as an upset stomach or full bladder
What are the three broad parts of the multimodal association areas?
1 - Anterior association area (pre-frontal cortex)
2 - posterior association area
3 - limbic association area
What cortical region is involved with intellect, cognition, recall, and personality?
Anterior association area (pre-frontal cortex)
What cortical region contains the working memory needed for abstract ideas, judgment, reasoning, persistence, and planning?
Anterior association area (pre-frontal cortex)
What does the development of the anterior association area depend on?
Feedback from social environment
What large cortical region is located in the temporal, parietal, and occipital lobes?
Posterior association area
The role of recognizing patterns, faces, and localizing yourself in space is associated with what cortical region?
Posterior association area
What cortical region is involved in understanding written and spoken language?
Posterior association area
What specific area in the posterior association area is involved in understanding written and spoken language?
Wernicke’s area
What cortical region is part of the limbic system?
Limbic association area
What cortical region involves the cingulate gyrus, parahippocampal gyrus, and the hippocampus?
Limbic association area
What cortical regions and provide emotional impact that makes a scene important and helps establish memories?
Limbic association area
What does the lateralization of cortical function mean?
The division of labor
Are the hemispheres identical?
Almost
What does the term cerebral dominance designate?
The hemisphere that is dominant for language
Which hemisphere controls language, math, and logic?
Left hemisphere
Which hemisphere involves visual-spatial skills, intuition, emotion, and artistic/musical skills?
Right hemisphere
What are tracts?
Bundles of myelinated fires
What substance allows communication between the cerebral areas in between the cortex and lower CNS?
Cerebral white matter
Cerebral white matter consists of what?
Myelinated fibers and tracts
What three things do the cerebral hemispheres consist of?
Cortex, white matter, and the basal nuclei
What are the three classifications of the fibers and tracts that make up white matter?
Association, commissural, or projection
What kind of fibers connect different parts of the same hemisphere?
Association fiber
What kind of fibers connect corresponding gray areas of the two hemispheres?
Commissural fibers
What allows the two hemispheres to function as a coordinated whole?
Commissures
What is the corpus callosum classified as?
Commissure
What kind of fibers tie the cortex to the rest of the nervous system into the body’s receptors and effectors?
Projection fibers
Projection fibers run in which direction?
Vertically
Commissural fibers run in which direction?
Horizontally
There is a group of subcortical nuclei deep within the cerebral white matter that are primarily involved in the control of movement. What are they called?
Basal nuclei (basal ganglia)
What does each hemisphere’s basal nuclei include?
Caudate nucleus, putamen, and globus pallidus
What does the caudate nucleus and putamen form?
The striatum
What three paired structures does the diencephalon include?
Thalamus, hypothalamus, epithalamus
How much of the diencephalon does the thalamus consist of?
80%
What structure of the diencephalon is the gateway to the cerebral cortex?
The thalamus
What structure of the diencephalon mediates sensation, motor activities, cortical arousal, learning, and memory?
The thalamus
Which structure of the diencephalon forms the walls of the third ventricle?
The hypothalamus
What is the name of the stalk that connects to the pituitary gland from the hypothalamus?
Infundibulum
Which structure of the diencephalon controls the autonomic nervous system?
The hypothalamus
Which structure of the diencephalon Allows physical responses to emotions from the limbic system?
The hypothalamus
Which structure of the diencephalon regulates body temp, hunger, water balance/thirst, and your sleep-wake cycle?
The hypothalamus
Which structure of the diencephalon controls the endocrine system? This structure controls anterior pituitary gland secretions and produces posterior pituitary hormones.
The hypothalamus
What are the paired pealike nuclei that bulge ventrally from the hypothalamus and are relay stations in the olfactory pathways?
The mamillary bodies
What structure is the most dorsal portion of the diencephalon?
The epithalamus
What structure of the diencephalon does the pineal gland extend from?
The epithalamus
What does the pineal gland secrete?
The hormone melatonin
What does the pineal gland help regulate along with hypothalamic nuclei?
The sleep-wake cycle
What does the brainstem consist of?
Midbrain, pons, and medulla oblongata
What feature is different in the brainstem that makes it different from the spinal cord?
The nuclei is embedded
What does the brainstem control?
Automatic behavior is necessary for survival
Brainstem nuclei are associated with how many of the 12 pairs of cranial nerves?
10
Where is the midbrain located?
Between the diencephalon and the pons
What hollow structure runs through the midbrain and connects the third and fourth ventricles?
The cerebral aqueduct
What substance surrounds the cerebral aqueduct?
The periaqueductal gray matter
What is the periaqueductal gray matter involved in?
Pain suppression and it links the fear-perceiving amygdaloid body and the ANS pathways that control the “fight or flight” response
What is the largest midbrain nuclei that raises four domelike protrusions on the dorsal midbrain surface?
Corpora quadrigemina
What are the functions of the superior colliculi?
Visual reflex center that coordinates head and eye movements when we visually follow a moving object, even if we are not consciously looking at it
What are the functions of the inferior colliculi?
Part of the auditory relay; also act in reflexive responses to sound
What are the two pigmented nuclei that are embedded in each side of the midbrain white matter?
Substantia nigra and red nucleus
What part of the midbrain is functionally linked to basal nuclei?
Substantia nigra
What part of the midbrain relays nuclei for some descending motor pathways and is part of reticular formation?
Red nucleus
What does the fourth ventricle separate?
The pons and the cerebellum
What three cranial nerves is the pons the origin of?
Trigeminal (V), abducens (VI), and facial (VII)
What are the two functions of the fibers in the pons?
1 - Connect higher brain centers and spinal cord
2 - Relate impulses between the motor cortex and the cerebellum
Where does the medulla oblongata join the spinal cord?
Foramen magnum
What structure of the medulla oblongata relays sensory information on the degree of stretch in muscles and joints to the cerebellum?
Inferior olivary nuclei
What structure of the of the medulla oblongata mediates responses that maintain equilibrium?
Vestibular nuclei
What two nuclei housed in the medulla oblongata serve as relay nuclei in a pathway by which general somatic and proprioceptive sensory information ascends from the spinal cord to the somatosensory cortex?
Nucleus gracilis, nucleus cuneatus
What structure of the brain stem is the cardiovascular center when involved in maintaining homeostasis?
The medulla oblongata
What structure of the brain stem is the respiratory center when maintaining homeostasis?
The medulla oblongata
How much of total brain mass does the cerebellum account for?
about 11%
What part of the brain adjusts motor output, ensuring coordination and balance?
The cerebellum
What connects the cerebellar hemispheres?
The vermis
What is the tree like pattern of cerebellar white matter called?
Arbor vitae
What structures does the cerebellum take input from?
Cortex, brainstem, sensory receptors
What are the two main cerebellar functions?
Processes motor activity, cognitive activity
What does the cerebellum use the signals from proprioceptors for?
Continuously inform the cerebellum of the body’s position and momentum
What structure of the cerebellum calculates the best way to coordinate the force, direction, and extent of muscle contraction to prevent overshoot, maintain posture, and ensure smooth, coordinated movements?
The cerebellar cortex
How does the cerebellum dispatch to the cerebral motor cortex its “blueprint“ for coordinating movement?
Via the superior peduncles
What roles does the cerebellum play in cognition?
Thinking, language, emotion
What are two examples of networks of neurons that work together but span wide areas of the brain?
The limbic system and the reticular formation
What structure of the limbic system recognizes angry/fearful facial expressions, assesses danger, elicits fear; with the hippocampus, related to memory?
Amygdaloid body
What does the limbic system do to odors?
Puts emotional responses to odors
Most of the output from the limbic system is relayed with what other structure?
The hypothalamus
What links the limbic system regions together?
The fornix
What structure of the limbic system plays a role in expressing our emotions through gestures and in resolving mental conflicts when we are frustrated?
The cingulate gyrus
Why is there an intimate relationship between our feelings and our thoughts?
Because the limbic system interacts with the prefrontal cortex
Which two structures of the limbic system play a role in memory?
The hippocampus and the amygdaloid body
What does the reticular formation extend through?
The medulla oblongata, pons, and midbrain
What is the reticular formation composed of?
Loosely clustered neurons and what is otherwise white matter
What system send impulses to the cerebral cortex to keep it conscious and alert?
The reticular activating system (RAS)
What system filters out repetitive, familiar, and weak stimuli?
The reticular activating system (RAS)
What system is inhibited by sleep centers, alcohol, sleep-inducing drugs, and tranquilizers?
The reticular activating system (RAS)
What can happen if there is a severe injury to the reticular activating system?
Permanent unconsciousness (coma)
What motor functions does the reticular activating system have?
1 - helps control coarse limb movements via reticulospinal tracts
2 - regulates visceral motor functions: vasomotor, cardiac, and respiratory centers
What does EEG stand for?
Electroencephalogram
What is an electroencephalogram?
Electrical activity accompanying brain function; generated from cortical synaptic activity
What does a flat EEG mean?
Clinical evidence of brain death
What are the two types of seizures regarding epilepsy?
Absence and tonic-clonic
What is an absence seizure?
A mild seizure, usually in young children, where their expression goes blank for a few seconds
What is a tonic-clonic seizure?
The most severe type of seizure, it might last a few minutes, where a victim loses consciousness, bones might break during intense convulsions, loss of bowel and bladder control, and a possibility of severe tongue biting
How can we control epilepsy?
Anticonvulsive drugs, implant a vagus nerve stimulator or deep brain stimulator, brain electrode implants to detect and prevent oncoming seizures
What is consciousness?
Conscious perception of sensation, voluntary initiation and control of movement, capabilities associated with memory/logic/judgment
What is a syncope?
A brief loss of consciousness
What is a coma?
An extended period of loss of consciousness
What are the two major types of sleep?
Non-rapid eye movement (NREM) and rapid eye movement (REM)
What happens to people that are deprived of REM sleep?
They become moody and depressed
What happens to daily sleep requirements as we age?
They decline
What sleep disorder is defined by an abrupt lapse into sleep?
Narcolepsy
What causes narcolepsy?
Orexins (“wake up” chemicals from hypothalamus) are destroyed by the immune system
What is the chronic inability to obtain quality amount of sleep needed?
Insomnia
What is one way that we can possibly treat insomnia?
Blocking orexin action
What sleep disorder is a temporary cessation of breathing?
Sleep apnea
What does sleep apnea cause?
Hypoxia
The language implementation system is associated with what three bits?
Basal nuclei, Broca’s area and Wernicke’s area (associated with the cortex on the left side of the brain)
What are the areas corresponding to Broca’s area and Wernicke’s area on the right side of the brain involved in?
Nonverbal language
Regarding memory, what are the two stages of storage?
Short term memory (STM) and long term memory (LTM)
What is another name for short term memory?
Working memory
What is the capacity of long-term memory?
Seemingly limitless, but we can forget over time
How is the hippocampus involved in memory?
It surrounds the temporal lobes, which are important to consolidation/access to memory
Motor memory involves what structure of the brain?
The cerebellum
Emotional memory involves what part of the brain?
The amygdaloid body
What is necessary for memory formation and retrieval?
ACh from the basal forebrain
What is the brain protected by?
Meninges, cerebrospinal fluid, bone, and the blood brain barrier
What are the three layers of the meninges?
From outer to inner: dura mater, arachnoid mater, pia mater
What is meningitis?
Inflammation of the meninges
What are the two layers of the dura mater?
The periosteal layer and the meningeal layer
What is the strongest meninx?
dura mater
The arachnoid mater contains arachnoid villi. What is the function of the arachnoid villi?
Reabsorption of cerebrospinal fluid
What is the name of the delicate vascularized connective tissue the clings tightly to the brain?
Pia mater
What is cerebrospinal fluid formed from?
Blood plasma
What does cerebrospinal fluid provide for CNS structures?
Buoyancy
What fluid nourishes the brain and carries chemical signals?
Cerebrospinal fluid
What structures hanging from the roof of each ventricle and produces cerebrospinal fluid at a constant rate while keeping it in motion?
The choroid plexuses
What is a normal volume of cerebrospinal fluid and how often is it replaced?
150 mL; placed every eight hours
Why are ependymal cells important to cerebrospinal fluid?
They use ion pumps to control the composition of cerebrospinal fluid and they help clean cerebrospinal fluid by removing waste
What causes hydrocephalus?
And obstruction blocks cerebrospinal fluid circulation or drainage
How is hydrocephalus treated?
Ventricular shunt to drain
What’s the difference in hydrocephalus in newborns and hydrocephalus in adults?
Newborns have unfused skull bones which allows had enlargement while adults do not; pressure would kill neurons
What does the blood brain barrier do for the brain?
It helps maintain a stable environment for the brain
What does the blood brain barrier do with blood?
It separates neurons from some substances in blood
In what way does the blood brain barrier allow nutrients to move?
Facilitated diffusion
What substances does the blood brain barrier allow through?
Any fat soluble substances including alcohol, nicotine, and anesthetics
Why is the blood brain barrier absent in some areas?
These areas monitor chemical composition of blood
What is a concussion?
Temporary alteration in function
What is a contusion?
Permanent damage to the CNS
What is a sub dural or subarachnoid hemorrhage?
It may force the brainstem through the foramen magnum, resulting in death
What is a cerebral edema?
It is the swelling of the brain associated with a traumatic head injury
What does the term ischemia mean?
It is when there is tissue deprived of blood supply and when brain tissue dies
What is hemiplegia?
paralysis on one side of the body, or sensory and speech deficits
What is a transient ischemic attack?
Temporary episodes of reversible cerebral ischemia
What is the only approved treatment for a stroke?
Tissue plasminogen activator (TPA)
What is Huntington’s disease?
It is a fatal hereditary disorder caused by the accumulation of the protein huntingtin. It leads to the generation of the basal nuclei and the cerebral cortex.
What is Parkinson’s disease?
It is a degeneration of dopamine-releasing neurons of substantia nigra. The basal nuclei deprived of dopamine becomes overactive causing tremors at rest. The cause of this is unknown.
What is Alzheimer’s disease?
What is a progressive degenerative disease of the brain. Plaques of beta-amyloid peptides form in the brain, causing toxicity. Also, neurofibrillary tangles inside neurons kill the neurons by disrupting the transport mechanisms.
Does the brain shrink with Alzheimer’s disease?
Yes
Where does the spinal cord begin and end?
It begins at the foramen magnum and ends at L1 or L2 vertebrae
Like the brain, what is the spinal cord protected by?
Bone, meninges, and cerebrospinal fluid
What do dorsal and ventral roots fuse laterally to form question
Spinal nerves
What do neurons whose cell bodies are in the spinal cord gray matter having common?
They are all multipolar
What do dorsal horns consist entirely of?
Interneurons
What do the ventral horns consist of?
Some interneurons, mostly somatic motor neurons whose axons exit the spinal cord via the ventral roots
How many pairs of spinal nerves are there in humans?
31
What is the white matter of the spinal cord composed of?
Myelinated and non-myelinated nerve fibers that allow communication between different parts of the spinal cord in between the cord and the brain
What is a first-order neuron?
It conducts impulses from the cutaneous receptors and proprioceptors, branches diffusely as it enters the spinal cord or the medulla oblongata, it has synapses with the second-order neuron
What is a second-order neuron?
It is an interneuron whose cell body is in the dorsal horn of the spinal cord or medullary nuclei with axons that extend to the thalamus or the cerebellum
What is a third-order neuron?
It is also an interneuron whose cell body is in the thalamus whose axons extend to the somatosensory cortex. There are no third-order neurons in the cerebellum.
What are the three main ascending pathways?
The dorsal column-medial lemniscal pathways, the spinalthalamic pathways, and the spinocerebellar tracts
Which of the three main ascending pathways transmit somatosensory information to the sensory cortex via the thalamus?
The dorsal column-medial lemniscal pathways and the spinothalamic pathways
The dorsal column-medial lemniscal pathways mediate what?
Precise, straight-through transmission of inputs from a single type of sensory receptor that can be localized precisely on the body surface, such as discriminative touch and vibrations.
The spinothalamic pathways primarily transmit what?
Impulses for pain and temperature, but also for coarse touch and pressure
What do the spinocerebellar pathways do?
They convey information about muscle or tendon stretch to the cerebellum, which uses this information to coordinate skeletal muscle activity.
What do descending pathways and tracts do?
They deliver efferent impulses from the brain to the spinal cord
What are the two groups of descending pathways?
Direct pathways (pyramidal tracts) and indirect pathways (all the others)
In the descending pathways, what two neurons do the motor pathways involved?
The upper motor neurons (pyramidal cells in primary motor cortex) and the lower motor neurons (ventral horn motor neurons that innervate skeletal muscles)
What is the direct pathway regulate?
Primarily regulates fast and fine (or skilled) movements such as texting or playing an instrument
What do the indirect pathways regulate?
They regulate the axial muscles maintaining balance and posture, the muscles controlling course limb movement, and head, neck, and eye movements that follow objects in your visual field
Damage to the dorsal roots or sensory tracts result in what?
Paresthesias (abnormal sensations) or a loss of sensation
What does damage to the ventral roots or ventral horn cells result in?
Paralysis, or the loss of motor function
Severe damage to the ventral root or the ventral horn cells results in what?
Flaccid paralysis: impulses do not reach muscles and there is no voluntary or involuntary control of the muscles
Damage to the upper motor neurons of the primary motor cortex results in what?
Spastic paralysis: spinal neurons remain intact and the muscles are stimulated by reflex activity but there is no voluntary control of muscles and muscles often shorten permanently
What is transection?
It is the cross sectioning of the spinal cord at any level and results in a total motor and sensory loss and regions that are inferior to the cut
The transection between T1 and L1 results in what?
Paraplegia
The transection anywhere in the cervical region results in what?
Quadriplegia
What is the transient period of functional loss caudal to a lesion called?
Spinal shock
What is poliomyelitis?
It is the destruction of ventral horn motor neurons by the poliovirus
What is Amyotrophic Lateral Sclerosis (ALS)?
It is the destruction of ventral horn motor neurons and fibers of the pyramidal tract
