Chapter 12 - THE CENTRAL NERVOUS SYSTEM Flashcards
(237 cards)
1
Q
The central nervous system consists of what two things?
A
brain, spinal cord
2
Q
What is cephalization?
A
an elaboration of the rostral, or anterior, portion of the CNS, along with an increase in neurons in the head
3
Q
What does gray matter consist of?
A
short, nonmyelinated neurons and neuron cell bodies
4
Q
What does white matter consist of?
A
1 - mostly myelinated axons
2 - some nonmyelinated axons (primarily in fiber tracts)
5
Q
What is the basic pattern of the CNS?
A
central cavity surrounded by gray matter, external to which is white matter
6
Q
Does the spinal cord exhibit normal pattern?
A
yes
7
Q
Does the brain stem exhibit the normal pattern of the CNS?
A
sort of, it has additional gray matter scattered within the white matter
8
Q
What is a cortex? Where is it located?
A
1 - an outer layer of gray matter
2 - cerebral hemispheres / cerebellum
9
Q
What are the brain’s ventricles? What are the chambers filled/lined with?
A
1 - central hollow cavities within the brain
2 - filled with CSF; lined with ependymal cells
10
Q
What are the lateral ventricles? What do they reflect?
A
1 - pair of large C-shaped chambers, one in each hemisphere
2 - the pattern of cerebral growth
11
Q
What is the septum pellucidum?
A
a thin median membrane that separates the lateral ventricles
12
Q
Each lateral ventricles communicates with what? Via what?
A
1 - third ventricle (in diencephalon)
2 - a channel called the interventricular foramen
13
Q
The third ventricle is continuous with what? Via what?
A
1 - fourth ventricle
2 - a canal-like cerebral aqueduct that runs through the midbrain
14
Q
The fourth ventricle lies where?
A
in the hindbrain dorsal to the pons and superior medulla
15
Q
What 3 openings mark the walls of the fourth ventricle?
A
lateral apertures (side walls) and the median aperture (in the roof)
16
Q
What is the subarachnoid space?
A
a fluid-filled space surrounding the brain
17
Q
What are the elevated ridges called?
A
gyri
18
Q
What are the shallow grooves in the brain called?
A
sulci
19
Q
What are deep grooves in the brain called?
A
fissures
20
Q
What does the longitudinal fissure do?
A
separates cerebral hemispheres
21
Q
What does the transverse cerebral fissure do?
A
separates the cerebral hemispheres from the cerebellum
22
Q
What does the central sulcus do?
A
it separates the frontal lobe from the parietal lobe
23
Q
What borders the central sulcus?
A
the precentral gyrus and the postcentral gyrus
24
Q
What separates the occipital lobe from the parietal lobe?
A
the parieto-occipital sulcus
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What is buried deep within the lateral sulcus and forms part of its floor?
the insula
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What houses the brainstem and the cerebellum?
The posterior cranial fossa
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What structure enables us to be aware of ourselves and our sensations, to communicate, remember, understand, and initiate voluntary movements?
The cerebral cortex
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Where is our conscious mind found?
The cerebral cortex
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What is the cerebral cortex composed of?
Gray matter: neuron cell bodies, dendrites, associated glia and blood vessels, but no fiber tracts
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The cerebral cortex account for how much of total brain mass?
40%
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What are the three types of functional areas in the cerebral cortex?
1 - motor areas
2 - sensory areas
3 - associated areas
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Where is the primary (somatic) motor cortex found?
In the precentral gyrus
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What is the primary (somatic) motor cortex responsible for?
Conscious control of precise, skilled, skeletal muscle movements
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Where is the premotor cortex found?
Anterior to the precentral gyrus
35
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
36
What is Broca’s area?
The motor-speech area that directs muscles of speech production
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How many hemispheres is Broca’s area found in?
One, usually the left
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What is the frontal eye field?
Controls voluntary eye movements
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Where are the sensory areas of the cerebral cortex?
Parietal, insular, temporal, and occipital lobes
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What receives general sensory information from skin, and proprioceptors of skeletal muscle, joints, and tendons?
Primary somatosensory cortex
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The primary somatosensory cortex is capable of spatial discrimination. What is that?
Identification of body region being stimulated
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What integrate sensory input from the primary somatosensory cortex for understanding?
The somatosensory association cortex
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What visual area receives visual information from the retinas?
The primary visual (striate) cortex
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What visual area uses past visual experiences to interpret a visual stimuli such as color, form, and movement?
The visual association area
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What visual area has the ability to recognize faces?
The visual association area
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What auditory area interprets information from the inner ear such as pitch, loudness, and location?
The primary auditory cortex
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What auditorium area stores memories of sounds and permits perception of sound stimulus?
The auditory association area
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What is the vestibular cortex responsible for?
Conscious awareness of balance (position of head in space)
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What sensory area is responsible for the conscious awareness of odors?
The olfactory cortex
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What sensory area is involved in the perception of taste?
The gustatory cortex
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What is the visceral sensory area responsible for?
Conscious perception of visceral sensations; such as an upset stomach or full bladder
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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
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What cortical region is involved with intellect, cognition, recall, and personality?
Anterior association area (pre-frontal cortex)
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What cortical region contains the working memory needed for abstract ideas, judgment, reasoning, persistence, and planning?
Anterior association area (pre-frontal cortex)
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What does the development of the anterior association area depend on?
Feedback from social environment
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What large cortical region is located in the temporal, parietal, and occipital lobes?
Posterior association area
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The role of recognizing patterns, faces, and localizing yourself in space is associated with what cortical region?
Posterior association area
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What cortical region is involved in understanding written and spoken language?
Posterior association area
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What specific area in the posterior association area is involved in understanding written and spoken language?
Wernicke’s area
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What cortical region is part of the limbic system?
Limbic association area
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What cortical region involves the cingulate gyrus, parahippocampal gyrus, and the hippocampus?
Limbic association area
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What cortical regions and provide emotional impact that makes a scene important and helps establish memories?
Limbic association area
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What does the lateralization of cortical function mean?
The division of labor
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Are the hemispheres identical?
Almost
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What does the term cerebral dominance designate?
The hemisphere that is dominant for language
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Which hemisphere controls language, math, and logic?
Left hemisphere
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Which hemisphere involves visual-spatial skills, intuition, emotion, and artistic/musical skills?
Right hemisphere
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What are tracts?
Bundles of myelinated fires
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What substance allows communication between the cerebral areas in between the cortex and lower CNS?
Cerebral white matter
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Cerebral white matter consists of what?
Myelinated fibers and tracts
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What three things do the cerebral hemispheres consist of?
Cortex, white matter, and the basal nuclei
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What are the three classifications of the fibers and tracts that make up white matter?
Association, commissural, or projection
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What kind of fibers connect different parts of the same hemisphere?
Association fiber
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What kind of fibers connect corresponding gray areas of the two hemispheres?
Commissural fibers
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What allows the two hemispheres to function as a coordinated whole?
Commissures
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What is the corpus callosum classified as?
Commissure
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What kind of fibers tie the cortex to the rest of the nervous system into the body’s receptors and effectors?
Projection fibers
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Projection fibers run in which direction?
Vertically
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Commissural fibers run in which direction?
Horizontally
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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)
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What does each hemisphere’s basal nuclei include?
Caudate nucleus, putamen, and globus pallidus
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What does the caudate nucleus and putamen form?
The striatum
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What three paired structures does the diencephalon include?
Thalamus, hypothalamus, epithalamus
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How much of the diencephalon does the thalamus consist of?
80%
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What structure of the diencephalon is the gateway to the cerebral cortex?
The thalamus
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What structure of the diencephalon mediates sensation, motor activities, cortical arousal, learning, and memory?
The thalamus
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Which structure of the diencephalon forms the walls of the third ventricle?
The hypothalamus
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What is the name of the stalk that connects to the pituitary gland from the hypothalamus?
Infundibulum
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Which structure of the diencephalon controls the autonomic nervous system?
The hypothalamus
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Which structure of the diencephalon Allows physical responses to emotions from the limbic system?
The hypothalamus
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Which structure of the diencephalon regulates body temp, hunger, water balance/thirst, and your sleep-wake cycle?
The hypothalamus
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Which structure of the diencephalon controls the endocrine system? This structure controls anterior pituitary gland secretions and produces posterior pituitary hormones.
The hypothalamus
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What are the paired pealike nuclei that bulge ventrally from the hypothalamus and are relay stations in the olfactory pathways?
The mamillary bodies
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What structure is the most dorsal portion of the diencephalon?
The epithalamus
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What structure of the diencephalon does the pineal gland extend from?
The epithalamus
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What does the pineal gland secrete?
The hormone melatonin
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What does the pineal gland help regulate along with hypothalamic nuclei?
The sleep-wake cycle
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What does the brainstem consist of?
Midbrain, pons, and medulla oblongata
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What feature is different in the brainstem that makes it different from the spinal cord?
The nuclei is embedded
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What does the brainstem control?
Automatic behavior is necessary for survival
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Brainstem nuclei are associated with how many of the 12 pairs of cranial nerves?
10
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Where is the midbrain located?
Between the diencephalon and the pons
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What hollow structure runs through the midbrain and connects the third and fourth ventricles?
The cerebral aqueduct
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What substance surrounds the cerebral aqueduct?
The periaqueductal gray matter
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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
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What is the largest midbrain nuclei that raises four domelike protrusions on the dorsal midbrain surface?
Corpora quadrigemina
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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
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What are the functions of the inferior colliculi?
Part of the auditory relay; also act in reflexive responses to sound
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What are the two pigmented nuclei that are embedded in each side of the midbrain white matter?
Substantia nigra and red nucleus
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What part of the midbrain is functionally linked to basal nuclei?
Substantia nigra
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What part of the midbrain relays nuclei for some descending motor pathways and is part of reticular formation?
Red nucleus
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What does the fourth ventricle separate?
The pons and the cerebellum
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What three cranial nerves is the pons the origin of?
Trigeminal (V), abducens (VI), and facial (VII)
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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
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Where does the medulla oblongata join the spinal cord?
Foramen magnum
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What structure of the medulla oblongata relays sensory information on the degree of stretch in muscles and joints to the cerebellum?
Inferior olivary nuclei
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What structure of the of the medulla oblongata mediates responses that maintain equilibrium?
Vestibular nuclei
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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
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What structure of the brain stem is the cardiovascular center when involved in maintaining homeostasis?
The medulla oblongata
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What structure of the brain stem is the respiratory center when maintaining homeostasis?
The medulla oblongata
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How much of total brain mass does the cerebellum account for?
about 11%
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What part of the brain adjusts motor output, ensuring coordination and balance?
The cerebellum
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What connects the cerebellar hemispheres?
The vermis
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What is the tree like pattern of cerebellar white matter called?
Arbor vitae
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What structures does the cerebellum take input from?
Cortex, brainstem, sensory receptors
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What are the two main cerebellar functions?
Processes motor activity, cognitive activity
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What does the cerebellum use the signals from proprioceptors for?
Continuously inform the cerebellum of the body’s position and momentum
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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
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How does the cerebellum dispatch to the cerebral motor cortex its “blueprint“ for coordinating movement?
Via the superior peduncles
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What roles does the cerebellum play in cognition?
Thinking, language, emotion
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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
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What structure of the limbic system recognizes angry/fearful facial expressions, assesses danger, elicits fear; with the hippocampus, related to memory?
Amygdaloid body
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What does the limbic system do to odors?
Puts emotional responses to odors
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Most of the output from the limbic system is relayed with what other structure?
The hypothalamus
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What links the limbic system regions together?
The fornix
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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
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Why is there an intimate relationship between our feelings and our thoughts?
Because the limbic system interacts with the prefrontal cortex
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Which two structures of the limbic system play a role in memory?
The hippocampus and the amygdaloid body
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What does the reticular formation extend through?
The medulla oblongata, pons, and midbrain
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What is the reticular formation composed of?
Loosely clustered neurons and what is otherwise white matter
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What system send impulses to the cerebral cortex to keep it conscious and alert?
The reticular activating system (RAS)
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What system filters out repetitive, familiar, and weak stimuli?
The reticular activating system (RAS)
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What system is inhibited by sleep centers, alcohol, sleep-inducing drugs, and tranquilizers?
The reticular activating system (RAS)
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What can happen if there is a severe injury to the reticular activating system?
Permanent unconsciousness (coma)
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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
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What does EEG stand for?
Electroencephalogram
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What is an electroencephalogram?
Electrical activity accompanying brain function; generated from cortical synaptic activity
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What does a flat EEG mean?
Clinical evidence of brain death
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What are the two types of seizures regarding epilepsy?
Absence and tonic-clonic
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What is an absence seizure?
A mild seizure, usually in young children, where their expression goes blank for a few seconds
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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
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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
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What is consciousness?
Conscious perception of sensation, voluntary initiation and control of movement, capabilities associated with memory/logic/judgment
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What is a syncope?
A brief loss of consciousness
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What is a coma?
An extended period of loss of consciousness
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What are the two major types of sleep?
Non-rapid eye movement (NREM) and rapid eye movement (REM)
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What happens to people that are deprived of REM sleep?
They become moody and depressed
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What happens to daily sleep requirements as we age?
They decline
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What sleep disorder is defined by an abrupt lapse into sleep?
Narcolepsy
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What causes narcolepsy?
Orexins (“wake up” chemicals from hypothalamus) are destroyed by the immune system
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What is the chronic inability to obtain quality amount of sleep needed?
Insomnia
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What is one way that we can possibly treat insomnia?
Blocking orexin action
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What sleep disorder is a temporary cessation of breathing?
Sleep apnea
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What does sleep apnea cause?
Hypoxia
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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)
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What are the areas corresponding to Broca’s area and Wernicke’s area on the right side of the brain involved in?
Nonverbal language
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Regarding memory, what are the two stages of storage?
Short term memory (STM) and long term memory (LTM)
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What is another name for short term memory?
Working memory
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What is the capacity of long-term memory?
Seemingly limitless, but we can forget over time
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How is the hippocampus involved in memory?
It surrounds the temporal lobes, which are important to consolidation/access to memory
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Motor memory involves what structure of the brain?
The cerebellum
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Emotional memory involves what part of the brain?
The amygdaloid body
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What is necessary for memory formation and retrieval?
ACh from the basal forebrain
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What is the brain protected by?
Meninges, cerebrospinal fluid, bone, and the blood brain barrier
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What are the three layers of the meninges?
From outer to inner: dura mater, arachnoid mater, pia mater
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What is meningitis?
Inflammation of the meninges
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What are the two layers of the dura mater?
The periosteal layer and the meningeal layer
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What is the strongest meninx?
dura mater
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The arachnoid mater contains arachnoid villi. What is the function of the arachnoid villi?
Reabsorption of cerebrospinal fluid
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What is the name of the delicate vascularized connective tissue the clings tightly to the brain?
Pia mater
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What is cerebrospinal fluid formed from?
Blood plasma
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What does cerebrospinal fluid provide for CNS structures?
Buoyancy
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What fluid nourishes the brain and carries chemical signals?
Cerebrospinal fluid
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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
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What is a normal volume of cerebrospinal fluid and how often is it replaced?
150 mL; placed every eight hours
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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
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What causes hydrocephalus?
And obstruction blocks cerebrospinal fluid circulation or drainage
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How is hydrocephalus treated?
Ventricular shunt to drain
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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
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What does the blood brain barrier do for the brain?
It helps maintain a stable environment for the brain
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What does the blood brain barrier do with blood?
It separates neurons from some substances in blood
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In what way does the blood brain barrier allow nutrients to move?
Facilitated diffusion
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What substances does the blood brain barrier allow through?
Any fat soluble substances including alcohol, nicotine, and anesthetics
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Why is the blood brain barrier absent in some areas?
These areas monitor chemical composition of blood
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What is a concussion?
Temporary alteration in function
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What is a contusion?
Permanent damage to the CNS
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What is a sub dural or subarachnoid hemorrhage?
It may force the brainstem through the foramen magnum, resulting in death
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What is a cerebral edema?
It is the swelling of the brain associated with a traumatic head injury
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What does the term ischemia mean?
It is when there is tissue deprived of blood supply and when brain tissue dies
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What is hemiplegia?
paralysis on one side of the body, or sensory and speech deficits
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What is a transient ischemic attack?
Temporary episodes of reversible cerebral ischemia
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What is the only approved treatment for a stroke?
Tissue plasminogen activator (TPA)
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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.
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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.
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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.
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Does the brain shrink with Alzheimer’s disease?
Yes
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Where does the spinal cord begin and end?
It begins at the foramen magnum and ends at L1 or L2 vertebrae
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Like the brain, what is the spinal cord protected by?
Bone, meninges, and cerebrospinal fluid
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What do dorsal and ventral roots fuse laterally to form question
Spinal nerves
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What do neurons whose cell bodies are in the spinal cord gray matter having common?
They are all multipolar
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What do dorsal horns consist entirely of?
Interneurons
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What do the ventral horns consist of?
Some interneurons, mostly somatic motor neurons whose axons exit the spinal cord via the ventral roots
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How many pairs of spinal nerves are there in humans?
31
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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
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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
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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
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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.
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What are the three main ascending pathways?
The dorsal column-medial lemniscal pathways, the spinalthalamic pathways, and the spinocerebellar tracts
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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
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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.
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The spinothalamic pathways primarily transmit what?
Impulses for pain and temperature, but also for coarse touch and pressure
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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.
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What do descending pathways and tracts do?
They deliver efferent impulses from the brain to the spinal cord
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What are the two groups of descending pathways?
Direct pathways (pyramidal tracts) and indirect pathways (all the others)
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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)
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What is the direct pathway regulate?
Primarily regulates fast and fine (or skilled) movements such as texting or playing an instrument
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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
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Damage to the dorsal roots or sensory tracts result in what?
Paresthesias (abnormal sensations) or a loss of sensation
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What does damage to the ventral roots or ventral horn cells result in?
Paralysis, or the loss of motor function
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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
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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
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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
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The transection between T1 and L1 results in what?
Paraplegia
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The transection anywhere in the cervical region results in what?
Quadriplegia
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What is the transient period of functional loss caudal to a lesion called?
Spinal shock
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What is poliomyelitis?
It is the destruction of ventral horn motor neurons by the poliovirus
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What is Amyotrophic Lateral Sclerosis (ALS)?
It is the destruction of ventral horn motor neurons and fibers of the pyramidal tract
