Chapter 12 CNS Flashcards
Describe the structure of the spinal cord
central cavity containing fluid
surrounded by grey (unmyelinated) core
external layer of white matter
What type of cells line the ventricles?
ependymal cells
What structure separates the 2 lateral ventricals?
septum pelucidum
What are the 4 regions of the brain?
CEREBRUM - grey matter and basal nuclei
DIENCEPHALON - thalamus, hypothalamus, and limbic
BRAIN STEM - midbrain, pons, and medulla
CEREBELLUM - hindbrain
what percentage of brain mass does the cerebrum make up?
83%
What is a gyri?
the ridges in the cerebrum
What is a sulcus (pleural; sulci)
shallow groves that separate gyri
What structure separates the frontal and parietal lobes?
central sulcus
What structure separates the parietal and temporal lobes?
lateral sulcus
What structure separates the parietal and occipital lobes?
parietal - temporal sulcus
What structure separates the left and right hemisphere?
longitudinal fissure
What structure separates the cerebrum and cerebellum?
transverse fissure
describe the structure of the cerebral cortex (cerebrum)
- thin outer layer of grey matter (2-4 mm thick)
- billions of interneurons with no fiber tracts
- convolutions (folds) increase surface area
What is the role of the cerebrum?
consciousness and intelligence
- awareness, sens prec, voluntary motor, communication, memory, understanding
What are the 3 types of functional areas in the cerebrum?
MOTOR
SENSORY
ASSOCIATION
which side of the brain controls the right side of the body?
control is contralateral
- left controls right
What lobe are the motor areas located?
all in the frontal lobe
What type of cells make up the primary somatic motor cortex?
pyramidal cells (large motor neurons whose axons extend from cortex and down the spinal cord to muscles
What is the role of the primary somatic motor cortex?
conscious control of precise or skilled voluntary movement of skeletal muscles
How much space is represented by the hands on the primary motor cortex compared to the arm?
Much more space because it requires a lot more processing for fine movements
What is the role of the premotor cortex?
involved in the planning of voluntary movements that depend on sensory input
CONTROLS: learned, repetitive, or patterned behavior
ex piano playing
What is the role of the broca’s area?
controls muscles involved in speech
active in planning and thinking about speech
Where is the central eye field area?
anterior to premotor and superior to broca’s
What is the role of the central eye field?
control voluntary movements of the eye
NOT INVOLVED IN SEEING
Where is the primary somatosensory cortex located and what is its role?
post central gyrus
- receives sensory information from skin, skeletal muscles, and joints
- capable of spatial discrimination; can identify where
- size of area for a part correlates with sensitivity
- it is contralateral
What is the role of the somatosensory association cortex?
ROLE: uses stored sensory memories to recognize objects being touched
what are the two areas involved in vision? what is their role?
primary visual cortex: receives stimuli
visual association area: interprets what we see by comparing with past visual memories
What is the largest sensory area in the body?
the primary visual cortex
What would happen if damage is caused to the primary visual cortex?
blindness
What would happen if damage is caused to the visual association area?
could see, but could not interpret what we are seeing
what are the two auditory areas?
primary auditory cortex
auditory association area
Where are the olfactory areas located?
temporal lobes
Where is the gustatory cortex located? what does it do
in the insula
ROLE: perception of taste
Where is the visceral sensory area located? what is its role?
located in the cortex of the insula
ROLE: conscious perception of visceral sensations
ex full bladder
What is a multi modal association area?
association areas that receive input from mult. sensory areas and then sends info out to mult areas
gives us our consciousness and allow integration of higher brain functions
What are the three multimodal association areas?
Anterior association area (prefrontal cortex)
Posterior association area
Limbic association area
Describe what the anterior association area (prefrontal cortex) is.
located in anterior frontal lobes
Most complicated region
- source of humanness and personality
- involved with intellect, cognition, recall, learning
- contains working mem
- matures slowly
What does development of the anterior association area (prefrontal cortex) depend on?
feedback from social environment (both positive and negative)
What is the posterior association area?
large region in temporal, parietal, and occipital lobes
- plays a role in recognizing patterns and faces and localizing us in space
- sense of self
- integrates sensory input to give a picture of the whole
- contains a large area involved in understanding language
What are the 4 areas of the posterior association area that are involved in language?
WERNICKE’s area: sounding out unfamiliar words
BROCA’s area: speech
LATERAL PREFRONTAL CORTEX: comprehension, word analysis
MOST OF LATERAL AND VENTAL PARTS OF TEMPORAL LOBE: reading and naming objects
What is the role of the limbic association area?
to provide emotional response to sensory inputs
- no specific location, network that is spread throughout the brain
What is the white matter of the cerebrum?
it is myelinated fiber tracts that are responsible for communication within cortex and between cortex and other parts of NS
What are the three types of fiber tracts in the white matter of the cerebrum?
COMMISURAL FIBERS
ASSOCIATION FIBERS
PROJECTION FIBERS
What do commissural fibers do?
connect R and L hemispheres
corpus callosum is the largest horizontal tract
What are association fibers?
connect different parts of same hemisphere together
two types:
short: connect adjacent gyri
long: bundled into tracts and connect different lobes
What are projection fibers?
connect the cortex to the rest of the NS (vertical tracts)
What are the basal nuclei?
clusters of grey matter inside white matter of cerebrum that play a complex role in motor control
- starting, stopping, monitoring movements
- inhibit antagonistic and unnecessary movements
- play a role in REGULATING ATTENTION
what can malfunctions of basal nuclei cause?
difficulty in coordinating movements (ex PD)
What is the diencephalon?
the grey matter enclosing the third ventrical
What structures are found within the diencephalon?
hypothalamus, thalamus, and epithalimus
What percent of the diencephalon does the thalamus make up?
80%
What is the role of the thalamus?
contains 12 nuclei that act as RELAY centers that project and receive fibers from cerebrum
- acts as a GATEWAY to cerebrum
role: sorts, edits, and relays info
What is the role of the hypothalamus?
many nuclei make up the visceral control center of body
- homeostasis, emotional response, sleep and sleep cycle, controls endocrine system
What is the epithalamus?
forms roof of third ventricle
contains:
Pineal gland - melatonin
Choroid plexus - secretes CSF
What are the three regions of the brainstem?
midbrain
pons
medulla
What does the brain stem control?
autonomic behaviours necessary for survival
How many of the 12 pairs of cranial nerves arise from the brain stem?
10 of 12 pairs
What is the role of the midbrain?
to serve as a conduction path between higher and lower brain centers
What are the two types of structures in the midbrain?
cerebral peduncles - contain pyramidal motor tracts
cerebellar peduncles - connect to cerebellum
What is the role of the pons?
acts as the bridge between higher brain centers and spinal cord
- relays impulses btwn motor cortex and cerebellum
- PNEUMOTAXIC center; controls breathing with the medulla
for what 3 cranial nerves does the pons contain nuclei for?
Trigeminal (V)
Abducens (VI)
Facial (VII)
What is the role of the medulla oblongata?
- relays sensory info from muscles and joints to cerebellum
- nucleus cuneatus and anucleus gracilis relay sensory information to the cortex
- vestibular nuclear complexes mediate responses that maintain equilibrium
has. …
- cardiovascular center
- respiratory centers
- reflex centers; vomiting, sneezing, coughing, swallowing
hypothalamus relays instructions to medulla which carries them out via reticular fibers
Where do the pyramidal tracts decussate (cross-over)?
in the medulla
What cranial nerves emerge from the medulla?
VIII, X, and XII
What are the fine gyri of the cerebellum called?
the folia
What is the tree-like structure of white matter in the cerebellum called?
arbor vitea
Are the cerebellar fibers contra or ipsi lateral?
ispilateral (stay on same side of the body)
What are the three peduncles of the cerebellum?
SUPERIOR peduncle - to midbrain
MIDDLE peduncle - to pons
INFERIOR peduncle - to medulla
What is the role of the cerebellum?
subconsciously coordinates body movements and maintains balance
may play a role in non motor functions such as word association and puzzle solving
Describe how the cerebellum influences movement.
1) cerebellum receives impulses from the cerebrum indicating intent to move
2) cerebellum coordinates with sensory input
3) cerebellum creates blueprint (plan) and sends it to cerebrum
4) cerebellum monitors and modifies blueprint as needed
What can result from damage to the cerebellum?
loss of
- balance
- muscle tone
- coordination
What is the role of the limbic system?
to mediate emotional responses
- interacts with autonomic nervous system, cerebral cortex, prefrontal lobes
hippocampus and amygdala play a role in long term memory
What are two parts of the limbic system?
AMYGDALA - fear response
CINGULATE GYRUS - expressing emotions via gestures
What is the role of the reticular formation?
extend from brain stem to thalamus, hypothalamus, cerebral cortex, cerebellum, and spinal cord
RETICULAR ACTIVATING SYSTEM (RAS) - keeps cerebrum alert and conscious and filters out unneeded stimuli
- helps regulate coarse skeletal movements and visceral muscle functions (vasomotor, cardiac, respiratory centers)
What are alpha brain waves?
regular and rhythmic, low amp, slow waves indicating an idling brain
AWAKE, but RELAXED
What are beta brain waves?
rhythmic, less regular, fast waves that occur when mentally alert
What are theta brain waves?
more irregular, slow waves.
- common in children and abnormal in awake adults
What are delta brain waves?
high amp, slow waves seen in deep sleep when RAS is muted or during anesthesia
What does the presence of delta waves in an awake individual indicate?
brain damage
What are the 4 levels of consciousness?
1) alert
2) lethargic (drowsy)
3) stupor (semi consciousness)
4) coma
What happens if the broca’s area is damaged?
can understand language but can’t speak
What happens if the Wernicke’s area is damaged?
can’t understand language but are capable of speech (although it won’t make sense)
What works with the broca’s and Wernicke’s areas to produce grammer and syntax of language?
the basal nuclei
What structures are involved in declarative memory?
hippocampus, thalamus, prefrontal cortex and basal forebrain
ACH from basal forebrain is necessary for formation and retrieval
What structures are involved in procedural memory?
basal nuclei relay sensory and motor inputs to the thalamus and premotor cortex
dopamine from the substantia nigra is necessary
What forms the blood brain barrier?
- continuous endothelium of capillaries (tight junctions)
- thick basal lamina around capillaries
- astrocytes that surround capillaries
how many pairs of spinal nerves emerge through the intervertebral foramen?
31
what is the cauda equine?
the cluster of nerve fibers at the base of the spinal cord
What are the two groves that divide the spinal cord into right and left halves?
dorsal median fissure
ventral median fissure
how do sensory (afferent) fibers enter the spine?
through the dorsal roots
Where are the cell bodies of the sensory neurons clustered in the spine?
the dorsal root ganglia
Where do motor (efferent) fibers leave the spine?
through the ventral roots
What do the dorsal horns of the spinal cord grey matter contain?
interneurons that synapse with sensory neurons
What do the ventral horns of the spinal cord grey matter contain?
cell bodies of somatic motor neurons
What do the lateral horns of the spinal cord grey matter contain?
cell bodies of the autonomic (sympathetic) motor neurons
What are the three types of tracts that are in the white matter of the spinal cord?
Ascending tracts - sensory to brain centers
Descending tracts - motor output from brain down to lower levels
Transverse fibers - transmit across cord
How many neurons do ascending pathways normally have?
3
1st order sensory neuron, cell body in dorsal root ganglion
2nd order interneuron, cell body in dorsal horn
3rd order interneuron, cell body in hypothalamus/cerebellum
What are the 3 types of ascending pathways in the spine?
Dorsal column (medial lemniscal) - decussate in medulla
Anterolateral
- decussate in spinal cord
Spinocerebellar tracts
- carry info about muscle/tendon stretch to cerebellum
- do not decussate or else do it twice
How many neurons are in descending pathways?
2
upper motor neuron and lower motor neuron
