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PSY 322 Exam 1; Question 3 (Arousal (Neurotransmitters (Histamine…
PSY 322 Exam 1; Question 3
Arousal
Brain Regions
RAS-reticular activating system
Bremer's experiment with cutting cats
when RAS activated by sensory info it arouses the cerebral cortex along 2 pathways
reticular formation to thalamus to cortex
reticular formation to lateral HT, basal ganglia, basal forebrain
connections from basal forebrain activate cortex and hippocampus
Structures in area of pons responsible for changes in arousal move us from sleep-waking and back
The Process
EEG
electrical activity of relaxed state = synchronous alpha waves, large amplitude
alert = cells of cortex desynchronized, beta waves, low amplitude
RAS
receives sensory input from external sensory systems, muscles, internal organs
cut all brain structures surrounding animals normal sleep-wake but when cut RAS always sleeping
sends fibers diffusely to whole cortex
arouse organism from asleep to wakefulness
Hebb's theory
sensory info = 2 purposes
cue function = provide info about stimuli
if cortex not aroused, cue function has no effect
arouse individual = arousal function
sensory stimuli sent to RAS and cortex via thalamus
RAS "activates" cortex so info from thalamus can be processed
motivation = activation of cortex by RAS
cortex sends fibers down to RAS
can activate RAS to keep arousal high when external or internal stimulation is low
thoughts and external stimuli can lead to arousal
Neurotransmitters
Acetylcholine
Cells that produce it in pons and basal forebrain
Activate cerebral cortex = desynchronized EEG when stimulated
Block acetylcholine = reduce arousal levels
Increase acetylcholine production = increase arousal
Increases general arousal of cerebral cortex
Histamine
tuberomammilary nucleus of HT
connect to cortex, thalamus, HT, basal ganglia, and basal forebrain
activity high during waking and low during sleep
Connections to cortex increase arousal directly
connect to basal forebrain indirectly increase arousal via acetylcholine
related to attention to environmental stimuli
Orexin
lateral hypothalamus
orexin-producing cells respond primarily when rats were alert and actively engaged with the environment
Norepinephrine
Locus coerulus of pons
Activates many areas: cortex, hippocampus, thalamus, cerebellum, pons, medulla
production high during waking drops during sleep; almost zero during REM sleep
important for vigilance
Serotonin
raphe nuclei of pons and medulla
connect to cortex, hippocampus, thalamus, HT, basal ganglia
most active during waking and decrease during sleep
facilitates automatic behaviors e.g. chewing, pacing, grooming
involved in maintaining ongoing activities and suppressing sensory info that might interrupt those activities
Physiological measures
monitor autonomic arousal: heart rate, blood pressure, etc
cortical activity by EEG
beta waves = aroused, alpha = relaxed
Sleep
Brain Regions
Non-REM
Ventrolateral preoptic area
promotes sleep through GABA connections
crucial for delta wave sleep
location:
destruction of this in rats led to absence of sleep and death after 3 days
stimulate these neurons produces drowsiness and sleep in cats
animals deprived of sleep then allowed to sleep freely we see increase in firing rate of these neurons
Locus coerulus
inhibits REM sleep-as activity drops off during NREM, REM sleep is possible (same with raphe)
Raphe nuclei
inhibits REM sleep
REM sleep
areas located in upper pons
sublateralodorsal nucleus
precoeruleus region
medial peribrachial nucleus
if cells in this area destroyed, REM sleep greatly reduced
secrete diff NTs some excitatory some inhibitory
highly active during REM sleep
Neurotransmitters
Adenosine
Function/role
found that when injected dogs with CSF from sleep deprived dogs (10+days) the dogs sleep for several hours
also did it with sleep deprived goats and inject into cats and rats. Both became drowsy and less active.
increase in slow wave patterns during normal sleep
has inhibitory effect on neurons that maintain arousal in the pons
caffeine blocks the receptor sites for adenosine
Location
produced by brain metabolism during waking
produced as a byproduct of brain metabolism which is higher during waking than during sleep
Actually a sleep chemical
promotes sleep as a result of being awake
GABA
Function/role
inhibitory action
inhibits site of arousal specifically locus coerulus, raphe nuclei, tuberomammilary nucleus, and orexiogenic neurons in lat HT
location
VLPO neurons produce it
The Process
ANS changes activity during sleep
During NREM sleep, blood pressure, heart rate and respiration decline. Veins and arteries dilate.
During REM, blood pressure, heart rate, respiration increase and become more variable
increased flow of blood to brain and penile erection/vaginal secretion
REM: the electrical activity of cortex changes from slow, high amplitude delta waves to fast, low amplitude waves
circadian rhythms
Endocrine System
Anatomic Description
Components
Major gland = pituitary
Mastor b/c role in controlling other glands
located at base of brain (temporal lobe)
hypothalamus (may not actually be part of system)
controlls pituitary
active in many motivated activities
manufactures hormones that have effect of causing pituitary to release its substances
adrenal gland
one located at top of each kidney
two parts serve 2 different functions
adrenal cortex
outer covering
secretes hormones-17-hydroxycorticoids
cortisol = major one
secretes aldosterone
main effect on water and electrolyte balance
adrenal medulla
center portion of gland
secretes epinephrine and norepinephrine
Process
General
set of glands secrete hormones direct into blood
hormones = chemical signals regulate/coordinate activity at distant organs
stress process
info about state of body constantly being gathered
external sensory systems
eyes, nose, ears
internal sensory systems
internal organs, blood changes, etc.
info monitored by the brain
when stressor detected
activate systems in hypothalamus
posterior HT activates sympathetic NS
stimulates adrenal medulla to secrete norepin and epin
anterior hypothalamus
secretes corticotropin releasing hormone (CRH)
causes pituitary to secrete adrenocorticotropic hormone ACTH into bloodstream
ACTH travels thru blood to adrenal glands, cause cortex to secrete cortisol and aldosterone into bloodstream
release of epinephrine, norepinephrine, and cortisol
mobilizes body for action
increases blood sugar, heart rate, blood pressure
better deal with stressors
feedback mechanisms
as blood levels of cortisol increase, brain shuts off production of ACTH and therefore cortisol
when stressor reduced/overcame
activity of pituitary/adrenal system reduced and return to relaxed state