Brain Activity

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  • Created by: LBCW0502
  • Created on: 21-10-18 18:16
Describe the procedure used to monitor electroencephalographic activity (1)
Pairs of electrodes are placed in 19 standard positions distributed over the head. Recordings from each pair of electrodes will differ slightly because they monitor activities of different populations of neurons in separate brain regions
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Describe the procedure used to monitor electroencephalographic activity (2)
Simultaneous activity of many neurons makes the extracellular fluid near the cortex surface more negative which may be detected by electrodes on the scalp. (Electrodes too far away from processes in the brain)
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Changes in consciousness from alert to drowsiness are indicated by what?
Shifts towards lower frequencies and higher amplitudes of recorded signals. Descending stages from drowsiness to deep sleep (stage IV) takes 1hr
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Stages of 'non-rapid eye movement' sleep contrasts with what?
Periods of rapid eye movement (REM) sleep - a time when the brain becomes active and most dreaming occurs
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Describe features of the circadian cycle of sleep and wakefulness in humans
Human volunteer isolated from cues about time by living in an underground bunker. Daily activity rhythm changed from a 24h cycle to one of about 26 hours (internal clock free-running). Hypothalamus - suprachiasmatic nucleus (primary biological clock)
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What is melatonin?
Hormone of darkness (not hormone of sleep)
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How is the nuclei of reticular activating system involved in regulation of the sleep-wake cycle? (1)
Left - cholinergic nuclei of pons-midbrain junction and raphe nuclei (serotoninergic). Right - locus coeruleus (noradrenergic) and tuberomammillary nucleus (histamine). Neurons in each nuclei are active during wakefulness (less active during non-REM)
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How is the nuclei of reticular activating system involved in regulation of the sleep-wake cycle? (2)
During REM sleep, cholinergic and noradrenergic neurons are active but not the serotoninergic neurons
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Describe the experiment used to demonstrate why we sleep
Two animals on a platform with a divider and feeders. When animal falls asleep, they are woken up by rotation of platform (sleep deprivation). Results show sleep deprivation leads to increased food intake and decreased body weight
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Describe features of regulation of food intake (example of motivated behaviour)
Altered feeding behaviour and body weight resulting from bilateral lesions of rat hypothalamus. Lateral hypothalamic syndrome (anorexia). Ventromedial hypothalamic syndrome (obesity)
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Describe features of food intake and regulation by satiety signals (1)
Duration of intervals between meals correlated with size of previous meal. Food intake regulated by short term signalling factors, GIT (PYY/ghrelin), longer term from adipose tissue (leptin)
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Describe features of food intake and regulation by satiety signals (2)
After food consumption, PYY is secreted from ileum/colon to reduce appetite. When stomach is empty, it secrets ghrelin to promote appetite
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Describe features of regulation of body weight (1)
Maintenance of body weight around set value. Force-fed (gain weight). Weight lost (regulation of food intake). Weight lost during period of starvation is gained when food is freely available
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Describe features of regulation of body weight (2)
Obese mouse surgically fused with normal mouse showed that obesity was lost. Administration of leptin leads to decrease in body weight
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Which part of the brain is important for control of feeding?
Hypothalamic nuclei
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Describe the response to elevated leptin levels due to excess adiposity
Raised levels of leptin activate neurons in arcuate nucleus containing peptides (aMSH, CARC). Neurons project to paraventricular nucleus, lateral hypothalamic area, brainstem, spinal cord, influence feeding/metabolism
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Describe the response to decreased leptin levels due to loss adiposity
Activate neurons in arcuate nucleus containing peptides NPY and AgRP. Inhibit neurons in paraventricular nuclei which control release of TSH and ACTH but activate neurons in lateral hypothalamus that stimulate feeding behaviour
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Describe features of the mesocorticolimbic dopaminergic neurons
Important for motivated behaviour. Destruction of neurons disrupt feeding behaviour. Animals like food it placed in mouth/lack of motivation to find it. Animals motivated to behave in ways that stimulated release of dopamine in basal forebrain
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Describe the effects of administering addictive drugs on the neurotransmitter systems (e.g. opiate, cholinergic, dopaminergic) (1)
Addictive drugs involved in motivated behaviour and dopaminergic pathway from ventral tegmental area to nucleus accumbens. Results - heroin/nicotine act on dopaminergic neurons in ventral tegmental area (project - lateral hypothalamus - forebrain)
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Describe the effects of administering addictive drugs on the neurotransmitter systems (e.g. opiate, cholinergic, dopaminergic) (2)
Cocaine enhances the action of dopamine within the nucleus accumbens by blocking its reuptake
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Describe the experiment used to determine pleasure centres
Electrical self-stimulation by a rate (when rat presses lever, it received a brief electrical current to an electrode in its brain. Self stimulation when electrodes are placed in: septal area, lateral hypothalamus, dorsal pons/ventral tegmental area
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Describe features of emotion? (1)
Variety of states in which distinctive subjective feelings e.g. happiness, anger are associated with specific physiological responses (e.g. facial expressions, autonomic activity, increased HR) and expressive behaviour (social interaction)
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Describe features of emotion? (1)
Emotion - mind's perception of physiological conditions that result from stimulus e.g. It's not that we see a bear/fear it/run. We see a bear/run, then fear bear. Our mind’s perception, higher A level/HR is the emotion
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Describe features of the limbic system
(Border, encircling). Integrates emotional/intellectual lives. Concerned with generating appropriate emotional/autonomic responses to stimuli. Affects output. Involved in adaptive/maladaptive states
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Describe features of emotion and the limbic system
Areas important for experience/expression - amygdala, orbital and medical prefrontal cortex, thalamus, hypothalamus and ventral striatum
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Describe features of amygdala
Active when identifying expressions (e.g. fear/rage). Active during panic attacks/PTSD. Site for emotional memories rather than memories of emotion. Damage to amygdala leads to inability to show fear. (Direct route from visual thalamus to amygdala)
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Describe features of the hippocampus
Role in memory - HM, place cells, combinations of stimuli, psychosis. Vulnerability - stress/brain damage. Resilience - adult neurogensis
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Where is the hippocampus located?
In the temporal lobes of the brain (sea-horse shaped)
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What are the two sub-divisions of memory?
Declarative (available to consciousness) and non-declarative (not available to consciousness)
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Describe features of the case involving amnesia
18 yr old underwent surgery to treat intractable epilepsy (1953). Hippocampus removed. Only remembers events prior to surgery, cannot remember new memories after surgery
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Describe the experiment used to investigate spatial learning and memory
Control rat compared to rate with hippocampus lesioned. Rats placed in circular tank with opaque water and a small platform. Control rat remembered location of platform better compared to subject rat
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Describe features of losing the hippocampus (1)
Large lesions cause spatial memory deficits. Ventral damage leaves spatial memory unaffected but changes anxiety levels. Dorsal damage produces spatial memory impairments but leaves anxiety behaviour unchanged (AD-medial temporal lobe shrinks)
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Describe features of losing the hippocampus (2)
Connection between hippocampus and possible declarative memory storage sites. Projections from cortical areas (medial and lateral views)
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Summarise features of the limbic system
Forms interface between sensation, cognition and emotion. Incorporates cortical/subcortical sites, circuits learning, mediates adaptive/maladaptive responses. Vulnerable to damage (disorders). Resilience of brain (ways to offset degenerative process)
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Card 2

Front

Describe the procedure used to monitor electroencephalographic activity (2)

Back

Simultaneous activity of many neurons makes the extracellular fluid near the cortex surface more negative which may be detected by electrodes on the scalp. (Electrodes too far away from processes in the brain)

Card 3

Front

Changes in consciousness from alert to drowsiness are indicated by what?

Back

Preview of the front of card 3

Card 4

Front

Stages of 'non-rapid eye movement' sleep contrasts with what?

Back

Preview of the front of card 4

Card 5

Front

Describe features of the circadian cycle of sleep and wakefulness in humans

Back

Preview of the front of card 5
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