chapter 12 CNS Flashcards
exam 2
Functions of the CNS
integration/ interpretation of incoming sensory info
sending out a motor response to effector organs
4 regions of brain
cerebral hemispheres
diencephalon
brain stem
cerebellum
gray matter
contains dendrites, cell bodies, and axon terminals
function: all synapses are found in gray matter - allows neurons to communicate
unmyelinated
white matter
contains myelinated axons , mostly in fiber tracts
passes msgs between diff areas of gray matter
allows generatiin of APs and msg relay
in the brain (gray/white)
gray matter is peripheral, white matter is central
outer layer of gray matter - cerebral cortex
in the brain stem (gray/white)
scattered gray matter found within white matter
in spinal cord (gray/white)
gray matter in a butterfly pattern surrounded by white matter
central canal - found at center of gray matter
Ventricles of the CNS
hollow chambers found in the brain that are filled with CSF and lined with ependymal cells
2 lateral ventricles
third ventricle
fourth ventricle
2 lateral ventricles
one in each cerebral hemispheres
look like ram horns
intraventricular foramen : connects lateral to 3rd
third ventricle
found in dienchephalon
cerebral aqueduct connects 3rd to 4th
travels inferiorly
4th ventricle
found in hindbrain
continuous w central canal of spinal cord
cerebral hemishpheres
form the most superior portion of the brain, make up most of the brain by mass
3 regions: cerebral cortex, white matter and basal nuclei
gyri - ridges of cerebral hemispheres
sulci - shallow grooves
fissure separate larger regions of the brain
Longitudinal fissure
separates the left and right hemispheres
transverse cerebral fissure
seperates the cerebral hemiosh[ers from the cerebellum
Lobes of the brain
Central sulcus: seperates frontal lobe and parietal lobe
Parieto-occipital sulcus: separates the occipital lobe from the parietal lobe
lateral sulcus - separates temporal lobe from the frontal and parietal lobes
cerebral cortex
portion of the brain where the conscious mind is found
functions: self-awareness, sensation, communication, memory, understanding/learning, initiation of voluntary movement
3 functional areas of cortex
motor areas: control voluntary movement
sensory areas: conscious awareness of sensations
association areas: integrate diverse information
associate something that has happened w something that is happening
Hemispheres are contralateral
right hemi is concerned info from left side of the body and vice versa
Motor areas of the cerebral cortex
Primary motor cortex
pre motor cortex
Broca’s area
frontal eye field
Primary motor cortex
allows for conscious control of skilled/precise voluntary movements
if u cant move issue w the primary motor cortex
Pyramidal cells
large neurons found in the primary motor cortex
axons of these neurons travel to the spinal cord in corticospinal tracts
synapse with and stimulate motor neurons
Pre motor cortex
- Helps plan movements by selecting and sequencing basic motor movements into more complex tasks
- communicates plan to primary motor cortex - controls voluntary actions that depend on sensory feedback
- if a movement is sloppy issue w pre motor cortex
Brocas area
specialized motor speech area that directs muscles involved in speech production
becomes active as we prepare to speak
usually found on left side of brain
Brocas Aphasia
neurons in Brocas area destroyed/damaged so a person knows what they want to say but are physically incapable of speech
Frontal eye field
controls voluntary movement of the eyes
Sensory areas of the cerebral cortex
primary somatosensory cortex
somatosensory association cortex
visual areas
auditory areas
vestibular cortex
olfactory cortex
gustatory cirtex
visceral sensory area
Primary somatosensory cortex
receive information from the general sensory receptors in the skin
general meaning not localized (scattered throughout the body)
the larger the body part, the more neurons are dedicated to that area of the body - increase sensitivity to sensation in larger body parts
somatosensory association cortex
integrates sensory input relayed to it via the primary somatosensory cortex
produce understanding of what is being felt (size , texture)
reaching into bag and knowing keys vs phone
visual areas
- primary visual cortex: largest cortical area
- receive visual information that originates from the retina in the eye
damage : loss of vision - Visual association area
- uses past visual experiences to interpret visual stimuli: allows us to recognize things
damage: can see clearly but don’t recognize objects
Auditory areas
- Primary auditory cortex
- interpretation of sound from the inner ear as pitch, loudness, and location - Auditory association area
permits perception of sound stimulus and stores memories of sounds for reference : recognze sounds weve heard
Vestibular cortex
allows for conscious awareness of balance/ orientation
maintain balance
olfactory cortex
primary olfactory cortex: conscious awareness of different odors
gustatory cortex
perception of taste stimuli
visceral sensory area
allow conscious perception of visceral organs : the sensation of deeper organs
feel of stomach or bladder is full
Lateralizaton of cortical functioning
A division of labor exists between the two hemispheres
division of labor: lateralization - left and right sides do things the other side might not
Cerebral dominance
one hemisphere dominates a particular task
usually in reference to language: Broca’s area - left side dominant
Cerebral white matter
-lies deep in cortical gray matter
-communication in the CNS: APs sent to different parts of the CNS
classification of cerebral white matter
1. Association fibers: connect different areas of the same hemisphere
2. Commissural fibers: connect corresponding areas of different hemispheres
3. Projection fibers: allow sensory information to reach cortex, motor output to leave the cortex
- contralateral
Basal Nuclei
sometimes referred to as basal ganglia
deep to white matter in each hemisphere
filters out incorrect or inapporpoate responses relating to
- muscle movement
- emotions and cognition
Diencephalon
thalamus
hypothalamus
epithalamus
Thalamus
relays sensory info coming into the cerebral cortex: makes sure sensory info is going to the correct part of the brain for interpretation
controls: motor activities, cortical arousal, learning and memory
Hypothalamus
function: main visceral control center in the body
1. controls autonomic NS
2. initiates a physical response to emotion
3. regulates body temperature
4. regulates food intake
5. regulates water balance and thirst
6. regulates sleep-wake cycles
7. controls endocrine system function: controls secretion of hormones by glands
Epithalamus
visual info about light surrounding us
pineal gland: more active as the sun sets
- secrete melatonin: become more tired
function : help regulate the sleep-wale cycle
Brain stem
3 regions
1. midbrain
2. pons
3. medulla oblongata
Functions of the brain stem
1. produces rigidly programmed, automatic behaviors necessary for survival: no conscious influence on these actions
2. provides pathway for fiber tracts running from higher brain centers to lower brain centers
3. innervation of the head
Midbrain
- regulate motor movement
- regulates hearing and vision
- alertness: aware of surroundings
- temperature control: stimulate the correct effector organ depending on body temp
Pons
- respiratory control
- bladder control
- swallowing
- most functions associated with the attached cranial nerves
medulla oblongata
- cardiovascular center: regulates heart rate and blood pressure
- respiratory center: controls respiratory rhythm and depth of breath
regulation of vomiting, swallowing, coughing, sneezing
Cerebellum
- receptors in the body relay info to the cerebellum ab body position, where the body is in space
- Cerebellar cortex decides the best way to execute movement - force, direction, and extent of muscle contraction
allows smooth coordinated movements required for everyday life
Functional brain systems
networks of neurons that span multiple regions of the brain that work together to accomplish one or more related tasks
1. Limbic system
2. the reticular formation
Limbic system
the emotional brain
regions
1. Amygdalioud body: response to perceived threats w fear or aggression
2. Cingulate gyrus: expressing emotions through gestures (jumping up and down when happy) and resolving mental conflicts during times of frustration (helps prevent reacting inappropriately to being frustrated)
Psychosomatic illness
limbic system output is relayed through the hypothalamus (main visceral control center)
emotional stress can cause visceral illnesses
illness w physical symptoms that results specifically from emotional causes
Limbic system and prefrontal cortex
interaction between the two
intimate relationship between our feelings and our thoughts
1. react emotionally to things we consciously understand to be happening
2. consciously aware of emotions
- communication between the two explains why
emotions sometimes override logic or why reason can stop us from expressing emotion inappropriately
Reticular activating system (RAS)
- sends a continuous stream of impulses to the cerebral cortex
- cerebral cortex is kept alert - filters out repetitve, familiar or weak signals
- prevention of sensory overload
- 99% of info is filtered out
Higher mental functions of the brain
- Language
- Memory
Language - higher mental function
left side of the brain : speaking and understanding language
1. Brocas area - production if spoken and written speech
2. Wernickes area - language comprehension , speaking clearly
right side of the brain : understanding non verbal language
ex . facial expression , body language
2 . emotional component of lamguage
- know how someone is feeling based off their tone
Memory - Higher brain function
storage/retrieval of info/past experiences
1. short term
2. long term
transfer of info from STM to LTM depends on
1. emotional state
2. rehearsal
3. Association
4. automatic memory
Categories of memory
Declarative memory - based on learning explicit info (facts)
manipulate symbols/language
Ex. names, dates, phone #s
Nondelcaraticve memory - memory acquired through repetition - hard to unlearn
based on actions more than language
Ex. riding a bike, playing instrument , driving a car
Protection of the brain
CNS tissue is very delicate (neurons damage easily)
1. bone
2. meninges
3. CSF
4. blood brain barrier
Meninges
membranes that surround and protect the brain
cover and protect CNS , protects blood vessels around CNS and contain CSF
1. dura mater
2. Arachnoid mater
3. Pia mater
Dura mater
most external layer
A. periosteal layer - attaches to the inner surface of skull bones
meningeal layer - form true external covering of the brain
Arachnoid mater
deep to dura mater
subarachnoid space - spiderweb projection that connect arachnoid mater to pia mater
CSF flows through here
pia mater
innermost layer
clings to brain surface
highly vascuralized
CSF
liquid surrounding the brain and spinal cord: produced by choroid plexus
1. forms liquid cushion : protection against physical trauma
2. gives buoyancy to CNS structures : w out CSF brain would crush itself
3. nutrient and chemical msg carrier - allows proper functioning of CNS
blood brain barrier
created by: 1. tight junctions 2. astrocytes and pericytes
movement across the barrier
1. simple diffusion - lipid soluble molecules pass freely
2. facilitated diffusion
3. transcytosis
substances not allowed to cross blood-brain barrier include
bloodborne metabolic waste
proteins
certain toxins
most drugs
nonessential amino acids
potassium ions
Brain traumas
concussions: alteration in brain functions following a physical blow to the head (temporary) - multiple concussions can result in permanent damage to brain functioning
contusions : permanent neurological damage resulting from bruising of the brain
MAY ENTER COMA
Degenerative brain disroders
Alzheimer’s disease: senile plaque found throughout the brain - sits between neurons and causes neuron death
effect: SHORT TERM memory loss, short attention span, disorientation,
LONG TERM: language loss, dementia, changes in personality
Parkinson’s disease: degenerating of dopamine-releasing cells in substania nigra of midbrain
basal nuclei becomes overactive w out dopamine: involuntary movement
CONSTANT TREMORS, STIFF FACIAL EXPRESSIONS,FORWARD BENT WALKING POSITION
Spinal cord
functions
1. conduction pathway
2. Major reflex center
the spinal cord extends from the foramen magnum until L1-L2
conus medullaris : cone shaped structure where spinal cord ends
ilium terminal : fibrous extensions that extend from conus medullaris to coccyx HELPS SECURE SPINAL CORD IN PLACE
Cauda Equina
collection of nerve roots at the end of the vertebral canal
Gray matter of spinal cord
central canal located at the center of gray matter: serves spinal cord w CSF
is arranged in horns
dorsal horns: receive somatic and visceral sensory input
ventral horns: somatic motor neurons - motor output to skeletal muscle tissue
lateral horns: only in thoracic and superior lumbar segments - motor output to visceral organs
Roots
Ventral roots: axons of ventral horn motor neurons (efferent) exit the spinal cord
Dorsal roots: axons of dorsal horn sensory neurons (afferent) enter the spinal cord
dorsal root ganglia: swelling or dorsal root where cell bodies of sensory neurons are found
Spinal Cord Trauma
damage to dorsal roots/sensory tracts: loss/abnormal sensation (paresthesia)
damage to ventral roots/motor tracts paralysis
1. flaccid paralysis: injury to the spinal cord of ventral roots prevents impulses from reaching skeletal muscle tissue CANT MOVE INVOLUNTARILY/VOLUNTARILY
2. spastic paralysis: upper motor neurons of primary motor cortex damages but spinal motor neurons still intact - can move involunatirly
Transection of spinal cord
complete cross-sectioning of the spinal cord
total sensory/motor loss below the point of separation
paraplegia: transection of T1-L1 - loss of functioning of lower limbs
quadriplegia: transection anywhere in cervical region
