nervous system part 3 – section 3: higher functions – sleep, emotion, and learning (from week 5 – nervous system part iii, slides 61–69)

functions of sleep

restoration of brain and body, energy conservation, learning and memory consolidation, immune function

sleep definition

an active process involving coordinated neural activity and changing brain states

theories of sleep

functions include restoration, neural repair, synaptic reorganization, and memory reinforcement

sleep control

regulated by neural circuits in the brainstem, hypothalamus, and forebrain

measurement of brain activity

electroencephalography (eeg) records electrical activity from cortical neurons

types of sleep

slow-wave sleep (sws, non-rem) and rapid eye movement (rem) sleep

slow-wave sleep

non-rem sleep; deep sleep with reduced brain activity and delta waves

rem sleep

characterized by rapid eye movement, vivid dreaming, muscle paralysis, and brain activity similar to wakefulness

characteristics of slow-wave sleep

low-frequency delta waves, reduced heart rate, respiration, and metabolism

characteristics of rem sleep

increased brain activity, irregular heart rate and breathing, muscle atonia, and dreaming

sleep cycle

progresses through stages of non-rem to rem approximately every 90 minutes

ascending reticular activating system (aras)

part of reticular formation that maintains cortical arousal and wakefulness

forebrain role in sleep

initiates and maintains slow-wave sleep

aras role in wakefulness

projects to thalamus and hypothalamus to stimulate cortical activation

body temperature during sleep

follows circadian rhythm; lowest during early morning

neurotransmitters promoting wakefulness

acetylcholine (ach), norepinephrine (ne), dopamine (da)

neurotransmitters promoting sleep

adenosine and acetylcholine (during rem sleep)

adenosine role

accumulates during wakefulness to promote sleep; caffeine blocks adenosine receptors

serotonin and sleep

regulates sleep onset and transitions between sleep stages

acetylcholine role in sleep

increases during rem to activate cortical neurons and dream processing

noradrenaline and dopamine

role in wakefulness and alertness; decrease during rem sleep

eeg patterns in wakefulness

beta waves (alert), alpha waves (relaxed but awake)

eeg patterns in sleep

k-complex and sleep spindles (stage 2), delta waves (stages 3–4), rem resembles awake pattern

importance of sleep deprivation

causes cognitive decline, mood changes, memory impairment, and weakened immunity

emotions

integrated responses involving subjective feelings, physiological reactions, and behavioral expressions

brain areas regulating emotion

limbic system, hypothalamus, midbrain, and prefrontal cortex

amygdala

functions in fear, anxiety, and aggression

hypothalamus

integrates emotional responses with autonomic and endocrine changes

prefrontal cortex

regulates emotional expression and decision making

motivation

internal drive that directs behavior and goal pursuit

relationship between emotion and motivation

emotions often drive motivation and behavioral priorities

reward centers in brain

include areas rich in dopamine such as nucleus accumbens and ventral tegmental area (vta)

dopamine role in motivation

produces feelings of pleasure and reinforcement; central to reward system

addictive behaviors

result from overstimulation of dopaminergic reward pathways

learning

process of acquiring new information or skills through experience

memory

retention and storage of learned information

neural plasticity

ability of nervous system to change structure and function in response to experience

hippocampus

role in learning and converting short-term memory to long-term memory

amygdala

role in emotional learning and memory modulation

types of learning

associative and non-associative

associative learning

forming connections between stimuli; includes classical and operant conditioning

non-associative learning

involves habituation (reduced response) and sensitization (enhanced response)

procedural memory (implicit)

stores learned motor skills and habits; involves cerebellum and basal nuclei

declarative memory (explicit)

stores facts and events; involves hippocampus and cerebral cortex

short-term memory

temporary storage lasting seconds to hours; limited capacity

long-term memory

stable storage lasting years to lifetime; large capacity

memory consolidation

process of converting short-term memories into long-term storage

neural basis of memory

involves changes in synaptic strength and connectivity

plasticity

mechanism underlying learning; includes formation of new synapses and modification of existing ones

long-term potentiation (ltp)

long-lasting increase in synaptic strength following repeated stimulation

key neurotransmitter in ltp

glutamate

receptors involved in ltp

nmda and ampa receptors

nmda receptor

allows calcium entry when depolarized and glutamate-bound; mediates long-term changes

ampa receptor

allows sodium entry for fast excitatory transmission

magnesium block in nmda receptor

blocked at rest; removed by depolarization to allow calcium influx

calcium role in ltp

triggers protein kinases that strengthen synaptic response

protein kinases

function in phosphorylating ampa receptors and promoting new receptor insertion

second messengers in ltp

trigger gene expression leading to structural synapse changes

paracrine signaling in ltp

postsynaptic cell releases signals enhancing presynaptic neurotransmitter release

result of long-term potentiation

strengthened synaptic transmission and improved communication between neurons

neurogenesis

formation of new neurons; occurs in hippocampus and contributes to learning

memory loss causes

aging, injury, disease, or disruption of hippocampal function

importance of learning and memory

essential for adaptation, survival, and cognitive development