central nervous system Flashcards
CNS is composed of
brain and spinal cord
how many regions does the brain have
4
1. cerebral hemispheres (cerebrum)
2. diencephalon
3. brain stem
4. cerebellum
gray matter
nonmyelinated
white matter
myelinated
basic pattern found in CNS
central cavity surrounded by gray matter, with white matter external to gray matter
cerebrum and cerebellum have
gray on the outside (cortex) surrounding white matter
ventricles
- fluid filled chambers
- filled with CSF
- lined by ependymal cells
- there are 4
cerebral hemispheres
make up 83% of the mass
markings
gyri - ridge
sulci - shallow groove
fissure - deep groove
longitudinal - separates two hemispheres
transverse - separates cerebrum and cerebellum
lobes
frontal
parietal
temporal
occipital
insula
sulci divide
the lobes
central sulcus
divides frontal and parietal
parieto occipital sulcus
divides parietal and occipital
lateral sulcus
divides frontal and temporal
3 regions of cerebral hemisphere
- cerebral cortex of gray matter superficially (outer edge)
- white matter internally
- basal nuclei deep within white matter
cerebral cortex is the
executive suite of the brain
site of the conscious mind
- awareness
- sensory reception
- voluntary motor initiation
- communication
- memory storage
thin superficial layer of cerebral cortex
2-4mm
gray matter
considerations of the cerebral cortex
- 3 types of functional areas
- each hemisphere is concerned with the contralateral/opposite side of the body
- lateralization (specialization) of function can only occur in one hemisphere
- conscious behavior involves entire cortex
3 functional areas
- motor - controlling voluntary movement
- sensory - conscious awareness of sensation
- association - integrate diverse information
motor areas
- located in frontal lobe
- act to control voluntary movement
- primary (somatic) motor cortex
- premotor cortex
- broca’s area
- frontal eye field
- damage to areas of primary motor cortex result in no movement/paralysis
primary (somatic) motor cortex
- located in precentral gyrus of frontal lobe
- pyramidal cells allow conscious control of precise, skilled skeletal muscle movements
- tracts project down spinal cord
premotor cortex
- helps plan movement
- controls learned, repetitious, or patterned motor skills
- coordinated simultaneous or sequential actions
broca’s area
- usually in left hemisphere
- motor speech area; directs the muscles of speech production
frontal eye field
controls voluntary eye movement
sensory areas
concerned with conscious awareness of sensation
- there are 8 main areas
8 main areas
- primary somatosensory cortex
- somatosensory association cortex
- visual areas
- auditory areas
- vestibular cortex
- olfactory cortex
- gustatory cortex
- visceral sensory cortex
primary somatosensory cortex
- located in postcenteal gyrus of parietal lobe
- sensory information from skin and proprioceptors
- spatial discrimination: identification of body region being stimulated
somatosensory association cortex
- posterior to primary somatosensory cortex
- integrates sensory inputs from primary somatosensory cortex for understanding of object
- determines size, texture, and relationship of parts of objects being felt
visual areas
- primary visual area
- located: posterior tip of occipital lobe
- receives visual info from retinas - visual association area
- interprets visual stimuli (color, form, movement)
- complex processing involves entire posterior half of cerebral hemispheres
auditory areas
- primary auditory areas
- located: superior margin of temporal lobes
- interprets info from, inner ear as pitch, loudness, and location - auditory association areas
- posterior to primary auditory cortex
- stores memories of sounds and permits of sound
olfactory cortex
awareness of odors
vestibular cortex
awareness of balance
gustatory cortex
perception of taste
visceral sensory cortex
perception of bladder/stomach/internal organs
multimodal association areas
- receive input from multiple sensory areas
- sends output to multiple areas
- allows us to give meaning and store memories
- sensations, thoughts, and emotions become conscious
- 3 parts
3 parts
- anterior association area
- posterior association area
- limbic association
anterior association area
- also called prefrontal cortex
- involved with intellect, cognition, recall, personality
- contains working memory; judgement, reasoning, and planning
limbic association
- provides emotional impact
- helps establish memories
posterior association area
- recognition of patterns and faces
- wernicke’s area - understanding written and spoken language
lateralization
- hemispheres not identical
- cerebral dominance: most are left sided, right handed
- left hemisphere controls language, math, and logic
- right hemisphere controls visual-spatial skills, intuition, emotion, artistic and musical skills
membrane must depolarize to
15 to 20 mV
Na+
permeability increases
Na+ moves ___, K+ moves ___
in, out
AP are
self propagating
AP can travel ONLY in what direction
forward
influx of Na+ cause
local currents that open Na+ voltage gates
–> domino effect
CNS tells difference of weak or strong by
the frequency of impulses
what is a refractory period
- when a neuron cannot trigger another AP
- voltage gated channels are open
absolute refractory period
- from opening of Na+ channels to resetting of channels
- ensures its all or none and enforces one way transmission of nerve impulses
relative refractory period
- follows ARP
- most Na+ channels have returned to resting state
- repolarzing is occurring
- threshold is elevated
- stimulus must be strong to get a new AP
rate of propagation depends on
- axon diameter
- degree of myelination
continuous conduction
speed is slower
saltatory conduction
- AP only generated in gaps
- electrical signal jumps rapidly from gap to gap
