CNS Flashcards
basal ganglia
several nuclei located deep within cerebral white matter
fucntions of basal ganglia
- motor control, cognition, emotions, learning
-inhibiting muscle tone, balance of excitatory and inhibitory inputs to neurons that innervate skeletal muscles
-selecting, maintaining purposeful motor activity while supressing unwanted patterns of movement
-coordinates slow, sustained contractions esp those related to posture and support
what is parkinsons caused by
degeneration of dopaminergic neurons in substantia nigra in midbrain which synapse onto neurons in basal ganglia- important for smooth movement
features of parkinsons
-inc muscle tone and rigidity
- involuntary useless movements at rest. tremors
-difficulty in initiating and carrying out movement
what causes huntingtons disease
degeneration of cuadate nucleus
symptoms of huntingtons
some motor circuits become overactive
-chorea- rapid uncontrolled jerky movements
- memory movements
where is the thalamus
deep in the brain near basal ganglia
function of thalamus
relay station and synaptic integrating centre for sensory input
helps direct attention to stimuli of interest
capable of crude awareness of sensations but cant distinguish location or intensity
function of hypothalamus
integrating centre for homeostatic functions
regulates internal enviroment
body temp and food intake
thirst and urine output
anterior pituitary hormone secretion
posterior pituitary hormone
five functions of brain stem
- majority of cranial nerves
- contains centres that control cardiovascular, respiratory, and digestive functions
- regulates postural muscle reflexes
- RAS- overall degree of cortical alertness
- sleep/ wake cycle
cerebellum function
integration of motor output and sensory perception
balance and planning of movement
what are the three functionally distinct parts of the cerebellum
- verstbilocerebellum: balance and eye movement
- spinocerebellum: enhances muscle tone and coordinates skilled movements
- cerebrocerebellum: plans and initiates voluntary activity and stores procedural memories
RAS
Reticular activating system- behavioural state system- diffuse modulatory system
where do neurons originate
in the RAS and project to various areas in brain
what does RAS influence
attention, motivation, wakefulness, memory, motor control, mood and metabolic homeostatis, overall degree of cortical awareness
what effect do general anaesthetics do to reticular formation
depress transmission in RAS
what does blocking the ascending pathways between the reticular formation and the cerebral cortex create
state of unconsciousness
limbic sysem
surrounds brain not seperate structure. interconnected ring of forebrain structures
what does the limbic system include
poritons of the cerebral lobes, basal nuclei, thalamus, and hypothalamus
what neurotransmitters does the limbic system use
serotonin, dopamine, norepinephrine
defects in the limbic system cause
depression
what parts of our behaviour is related to limbic system
emotions, basic survival, sociosexual behaviour, motivation and learning
limbic system functions
- emotion: subjective feelings and moods and physical responses associated with these feelings (amugdala)
- basic behavioural patterns: aimed at survival and perpetuation of species
- motivation
- learning
- memory
cortical structures of limbic system
medial prefrontal cortex: decision making, control of emotion and impulses
cingulate cortex: motivation, drive, mood, decreased avitivity correlates with depression
medial temporal lobes: episodic memory formation of recent event sequences
subcortical structures of the limbic system
hippocampus: within medial temporal lobe: episodic memory formation, context, and location
hypothalamus: homeostasis and basic drives: food, water, sex, aggresion
amygdala: fear and affective learning. activation causes anxiety, ablation eliminates fear recognition and learning
learning
acquisition of knowledge or skills as a consequence of experience, instruction or both. rewards and punishments are integral parts
memory
storage of acquired knowledge for later recall
short term memory
seconds to hours
long term memory
days to years
working memory
temporarily holds and interrelates various peices of info relevant to a current mental task
memory trace
neural change reponsible for retention or storage of knowledge. present in multipole regions of the brain (sites of original auditory, visual, experince)
declarative memory
what memories of people, places and important in remembering facts and events. involves hippocampus
procedural memory
how to memories. the learning of new motor skills involves the cerebellum
function of the medial temporal lobe (hippocampus and adjacent areas of temporal lobe)
consolidation of short term declarative memory into long term memory mostly during sleep. requires gene activation leading to protein synthesis and synaptic changes
what is the difference between short and long term memory
different molecular mechanisms involved
short term memory
involves transient changes in synaptic activity
habituation: decreased respnosiveness to a repetitive and indifferent stimulus
sensitization: increased respnsiveness to mild stimuli following a nocious stimuli
short term memory
involves transient changes in synaptic activity
habituation: decreased respnosiveness to a repetitive and indifferent stimulus
sensitization: increased respnsiveness to mild stimuli following a nocious stimuli
both involve changes in ion channels and currents
long term memory
involves formation of new permanent synaptic connections
activation of specific genes that control synthesis of proteins needed for lasting structural or functional changes in pre or postsynaptic membranes
long term potentiation LTP is important for initial storage into long term memory
working memory
concept that working memory memory temporarily holds and interrelates various pieces of info that are relevant to a current mental task 7+/-2 objects
hold and process data for immediate use and can include newly acquired and prev stored info that is transiently accessed
why is working memory critical
to reason, plan, and make judgements
where does working memory take place
in the prefrontal cortex
what is azheimers characterized by
short term memory loss in early stages followed by eventual loss of long term memory, confusion, disorientation, personality changes, ability to read and write and calculate, language and speech ability
what brain alterations in alzheimers
neurofibrillar tangles, amyloid plaques.
characteristic loss of cholinergic neuros in basal forebrain- cells that project to hippocampus
what neurotransmitter do cholinergic neurons use
acetylcholine
what hemisphere is language locallized in
left
95 for right handed
60-70 for left handed
brocas area
speaking ability
damage leads to inability to send proper commands to motor cortex to form the words
wernickes area
language comprehension
damage leads to inability to attach meaning to words or choose the approperiate words
aphasia
defect in language processing caused by disfunction of the dominant cerebral hemesphere (stroke, brocas, wernickes aphasia)
speech impediments
defects in mechancal aspects of speech
dyslexia
difficulty in learning to read bc of inappropriate interpretation of words due to developmental abnormatlities in connections bw visual and language areas of cortex (independant of intelegance)
coordination of neurons in wake state
not always coordinated as a result of ascending signals coming from reticular activating system
what is EEG used for
clinical tool used for diagnosis of cerebral dysfunction
EEG of epilepsy
shows distinctively abnormal traces
how to seizures occur
when collections of neurons undergo synchronous action potentials that produce stereotypical involuntary spasms and alterations in behaviour
neuronal excitability coupled with compromised inhibitory activity or prolonged activation of excitatory transmitters
legal determination of death
flat EEG- electrocerebral silence. needs to be coupled with other stringent criteria
alpha rythym range
8-13 Hz
alpha waves
index of cortical inactivity
present in adult who is awake but relaxed with eyes closed
amplitude is neg correlated to cortical activity
beta rhythym range
13-30 hz
beta waves
decreased synchronization with cortical activity
in individuals who are alert and attentive to external stimuli or exert specific mental effort
states of consciousness
maximum alertness
wakefulness
sleep (stages 1-4 and paradoxical)
coma
maximum altertness dependancy
on sensory input that stimulates the RAS and subsequenctly the activity levels of the CNS as a whole
normal cyclic variation in awareness
sleep- wake cycle
is sleep an active process
yes the brains overall activity is not reduced
two types of sleep characterized by EEG patterns
slow wave sleep- delta wave non rapid eye movement NREM
paradoxial sleep- rapid eye movement
functions of sleep
conservation of energy for defrence of predation
restorative function for brain and body for healing and growth and immune function
cerebral changes that underlie consolidation of long term memory in cortex
what happens during stage 1 of sleep
drowsiness and drifting in and out of consciousness
stages 2-4 of sleep
sleepers move through these stages then move back through the stages and enter REM without going back to stage 1
time in stages 3 and 4 decreases over the cycles and time in REM increases
how many min is a cycle of sleep
90 min
stages of sleep
occurs in 4 stages each with a lower frequency but higher amplitude EEG wave
light sleep
stage 1
deep sleep
stage 4
