Chapter 12: The Central Nervous System Flashcards
CNS Development
neural tube formed by week 4; brain develops from anterior portion of neural tube; spinal cord develops from posterior porition of neural tube
3 Primary Brain Regions Form
forebrain, midbrain and hindbrain; from these 3 primary regions 4 adult brain structures develop (cerebrum, dienchephalon, brain stem and cerebellum
Gender Specific Differences Appear…
during embryonic development; determined by presence of testosterone; sex differenetiation of genitals take place during first 2 months of pregnancy; sexual diffeentiation of the brain starts in the second half of pregnancy
Cavities (ventricles) develop within the brain
they are filled with cerebrospinal fluid (CF) and lined by ependymal cells
Cerebral Hemispheres
each consist of 5 lobes; frontal, parietal, temporal, occipital and insula
Gyri
gyrus; raised areas
Suri
sulcus; shallow depressions
Central Sulcus
separates frontal and parietal lobes
Lateral Sulcus
separates temporal lobe from frontal and parietal lobes
Parieto-occipital Sulcus
separates parietal and occipital lobe
Fissures
deep depressions
Longitudinal Fissure
separates parietal lobes
Transverse Cerebral Fissure
separates cerebrum from cerebellum
Cerebral Cortex
outermost layer of cerebrum; consists of grey matter containing interneuron cell bodies and dendrites; each hemisphere sends and receives info from OPPOSITE sides of the body; contains 3 functional areas- motor areas, sensory areas, and association areas
Motor Areas
control voluntary movement; located in posterior part of frontal lobe
Primary Motor Cortex
located in presentral gyrus of frontal lobe; controls voluntary movements of skeletal muscles on opposite side of body
Premotor Cortex
anterior to primary motor cortex; helps plan movements of complex tasks (typing, playing muscial instruments)
Brocas Area
present in 1 hemisphere only (usually left); controls muscles of speech
Frontal Eye Field
control voluntary movement of eyes
Sensory Areas
deal with conscious awareness of sensation; located in parietal, insular, temporal, and occipital lobes
Primary Somatosensory Cortex
located in post central gyrus of parietal lobe; receives sensory info from sensory receptors in skin and proprioceptors on opposite side of body; exhibits somatotpy (a specific part of the body is associated with a distinct location in the CNS)
Somatosensory Association Cortex
posterior to primary somatosensory cortex; integrates sensory input based on past experiences; like placing hand on hot stove
Primary Visual Cortex
located in occipital lobs; receives visual input from retina of eyes
Primary Auditory Cortex
location in superior portion of temporal lobe; receives auditory input from inner ear (cochlea)
Vestibular (Equlibrium) Cortex
located in insular lobe; responsible for conscious awareness of balance
Primary Olfactory Cortex
located in uncus (underneath) of temporal lobe; receives smell input from nasal cavity
Gustatory Cortex
located in insular lobe; receives taste input from taste buds
What type of matter is the cerebral cortex?
grey matter
Cerebral Hemispheres Exhibit a Division of Labor
aka lateralization; left hemisphere is more focused on language, math and logic; right hemisphere more involved with intuition, emotion, artistic and muscial skills; 90% of people are left hemisphere dominant and right handed; 10% of people are reversed or they share equal function and most are left handed
Grey and White Matter
grey matter is unmyelinated (and mostly cell bodies and dendrites) and white matter is myelinated
Cerebral White Matter
deep to the cortex; houses lateral ventricles (separated from each other by septum pellucidum); consists of myelinated axons bundled into tracts; allows communication within brain and between brain and spinal cord
Association Fibers/Tracts
connect different parts of the SAME hemispheres
Commissural Fibers/Tracts
connect right and left hemispheres (corpus callosum)
Projection Fibers/Tracts
connect cerebral hemispheres to spinal cord
Cerebral Nasal Nuclei (ganglia)
islands of gray matter within white matter of the cerebrum; influence muscle movements directed by the primary motor cortex
Diencephalon
forms central core of brain; consists of thalamus, hypothalamus, and epithalamus
Thalamus
encloses third ventricle; relay sensory info to and motor info from cerebrum; routes incoming information to appropriate areas of cerebral cortex; contains nuclei that play a key role in mediating sensation, motor activities, cortical arousal, learning and memory
Hypothalamus
visceral control center; associated with optic chiasm and infundibulum of pituitary gland; chief integration center of autonomic (involuntary) nervous sys; contains nuceli that regulate body temp, hunger, water balance/thirst and sleep/wake cycles; contains anterior pituitary; produces 2 hormones (oxytocin and ADH)
Epithalamus
consists of pineal gland (secretes melatonin; helps regulate sleep/wake cycles) and the posterior commissure
Brain Stem
consists of midbrain, pons, and medulla oblongata
Midbrain
contains nuclei that house- visual reflex center, auditory reflex center, dopamine releasing neurons; contains projection fibers; encloses cerebral aqueduct
Pons
relays information from cerebrum to cerebellum; contains pontine respiratory center (helps regulate rate and depth or breath); contains projection fibers
Medulla Oblongata
relays sensory info to the somatosensory cortex and cerebellum; contains nuclei controlling heart rate, blood vessel diameter, respiratory rate, vomiting, coughing, swallowing, hiccuping, and sneezing; contains projection fibers; amin site of decussation (crossing over of neurons)
Cerebellum
processes infor from cerebral motor cortex, propriocepter, visual pathways and equillibrium pathway; responsible for balance posture, and smooth coordinated skeletal muscle movements; white matter known as “arbor vitae”
Functional Brain Systems
network of neurons found in different regions of the brain that work together; include limbic system and reticular formation
Limbic System
includes cerebral (hippocampus, amygdala) and diencephalon (thalamus, hyppothalamus structures); combines higher mental function and primitive emotions into a single sys, the emotional nervous sys; mediates emotional response; involved in memory processing and motivation; involved in the bodys response to stress (connected to endocrine and autonomic NS)
Reticular Formation
extends through brainstem (midbrain, pons, medulla oblongata); reticular activating sys (RAS) keeps cerebral cortex alert and conscious (inhibited by sleep center in hypothalamus; depressed by alcohol, sleep inducing drugs and tranquilizers); filters out repetitive, familiar or weak signals (like you dont feel your clothes after a while) (LSD blocks this filter)
What controls higher mental functions?
cerebrum
Language
left cerebral hemisphere is language dominant hemisphere in most individuals (contains brocas and wenikes areas)
Broca’s Area
controls muscles of speech; if damaged you have difficulty speaking, not in understanding language
Wernike’s Area
enables you to understand spoken and written words; if damaged you can not understand language; the muscles still work but anything you say is nonsense
Memory
involves storage and retrieval of information
Short Term Memory
working memory; temporary memory storage; may be transfered to LTM (can take minutes or hours)
What is the transfer of short term to long term memory influenced by?
emotional state, rehearsal. association
Long Term Memory
LTM; limitless capacity
Brain Wave Patterns
reflect electrical activity of the cerebrum; recorded in an EEG (electroencephalogram)
What are the four types of brain wave patterns?
alpha, beta, theta, delta
Alpha Waves
regular, rhythmic, low amplitude waves; indicate a relaxed state of wakefulness
Beta Waves
less regular than alpha and higher frequency; indicate mental alertness
Theta Waves
much more irregular; common in children but rare in adults
Delta Waves
high amplitude waves; occur during deep sleep; indicate brain damage in awake adults
What does is mean to be clinically dead?
flat EEG; no brain waves in cerebrum
Sleep
a state of partial unconsciousness ; can be aroused by stimulation
NREM Sleep
non rapid eye movement sleep; 4 stages
Stage 1 of NREM
relaxation begins; alpha waves; easily aroused
Stage 2 of NREM
irregular EEG with sleep spindles; arousal more difficult
Stage 3 of NREM
theta and delta waves; vital signs decline
Stage 4 of NREM
delta waves; arousal difficult; bed wetting, night terrors, and sleepwalking may occur
REM
rapid eye movement sleep; most dreaming occurs; vital signs increase; skeletal muscles (except ocular and diaphragm) are inhibited (prevents us from acting out our dreams)
Hypothalmus and Sleep
hypothalamus dictates timing of sleep cycle and relfect a circadian (24 hour) rythm; inhibits RAS; releases orexins (wake up chemicals)
Protection of the Brain includes
bones, meninges, cerebrospinal fluid, and blood-brain barrier
Meninges
connective tissue membranes; order: dura mater, arachnoid mater, and the inner layer is the pia mater
Dura Mater
outermost meninge; leathery; 2 layered sheet of fibrous connective tissue fused together EXCEPT at doral venous sinuses
Dural Venous Sinuses
collect venous blood from brain and empty it into internal jugular veins
Meningeal dura mater invaginates to form…
3 septae that limit movement of the brain; falx cerebri, falx cerebelli, tentorium cerebrelli
Arachnoid Mater
middle meninx; spider web like extensions dip into subarachnoid space (contains CSF and large blood vessels); arachnoid granulation (knob like extension) absorb CSF into dural venous sinuses
Pia Mater
inner meninx; delicate layer “glued” to brain and spinal cord; arachnoid granulations (knob like extension) absorb CSF into dural venous sinuses
What is meningitis?
inflammtion of the meninges
What is encephalitis?
inflammation of brain
Cerebrospinal Fluid
protects and nourishes brain and spinal cord; produced by ependmal cells of choroid plexuses in the ventricles; CSF produced at same rate as being absorbed
Hydrocephalus
occurs when CSF production outpaces resorption; image of young child with swollen head
Blood Brain Barrier
protective; helps maintain a stable environment; formed by brain capillaries surrounded by astrocytes (induce capillary endothelial cells to form tight junctions); the tight junctions allows nutrients and lipid-solubel sibstances to enter (o2, co2, alcohol, nicotine, and anesthetics); barrier absent neat vomiting center nad hypothalamus
Why is the blood-brain barrier absent near the vomiting center and hypothalamus?
so it can detect toxins in blood and hypothalamus regualtes a lot and needs access to the blood to monitor it
Traumatic Brain Injuries
concussion, contusion (bruise on brain), subdural, or subarachnoid, hemorrhage (bleeding on brain), cerebral edema
Cerebrovascular Accidents
CVAs; strokes; brain area dies due to lack of blood uspply; most common disorder
Degenerative Disorders
alsheimers (degeneration of neurons –> dementia); parkinsons (degeneration of dopamine releasing neurons); huntingtons (hereditary, degeneration of basal nuclei and the cerebral cortex)
Congenital Disorders
cerebral palsy (voluntary muscles poorly controlled or paralyzed; results from temporary lack of o2 during birth); anencephaly (cerebrum and part of the brain stem never develop; die shortly after birth)
Spinal Cord Gross Anatomy
extends from medulla oblongata to the conus medullaris (L1/L2 vertebra); cervical and lumbar enlargements indicate where nerves serving arms and legs arise
Cauda Equina
nerve roots extending from the conus medullaris
Filum Terminale
fibrous extension of conus medullaris; anchors cord to coccyx
How many pairs of spinal nerves are there in humans?
31; the extra one is between occipital condyles and atlas
How many cervical, thoracic, lumbar, and sacral nerves are there?
c-8, t-12,l-5, s,5
Denticulate Ligaments
attach cord to dera mater
The spinal cord is the….
major reflex center
Spinal Nerves come out of…
intervertebral foramen
Lateral horns of gray matter are only found…
in thoracic, S1, S2, regions
Spinal Cord Injuries and Disorders
damage to primary motor cortex (spastic paralysis); damage to spinal cord or ventral roots (flaccid paralysis); transcetion of cord below t1 and l1 (paraplegia); transection of cord in cervical region (quadriplegia)
Poliomyelitis
polio, destroys motor cell bodies; poliovirus destroys motor neuron cell bodies in ventral horns (flaccid paralysis); death occurs when diaphragm paralyzed; prevented via vaccine
Amytrophic Lateral Sclerosis (ALS)
progressive destruction of motor neuron in ventral horns and descending tracts (flaccid paralysis); caused by environemental and genetic factor; death after 5 years
Spina Bifida
conginetal disorder involving inadequate prenatal closure of vertebra; 70% caused by lack of folic acid in materal diet in early pregnancy
