Download 12 - Brazosport College

Human Anatomy & Physiology
Ninth Edition
CHAPTER
7/2/2012
© Annie Leibovitz/Contact
Press Images
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12
The Central
Nervous
System 2:
Sleep and
Memory
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© 2013 Pearson Education,
Inc.
Sleep and Sleep-Wake Cycles
• State of partial unconsciousness from
which person can be aroused by
stimulation
• Two major types of sleep (defined by EEG
patterns)
– Non-rapid eye movement (NREM) sleep
– Rapid eye movement (REM) sleep
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Figure 12.19a Types and stages of sleep.
Awake
REM: Skeletal muscles (except
ocular muscles and diaphragm)
are actively inhibited; most
dreaming occurs.
NREM stage 1: Relaxation
begins; EEG shows alpha waves;
arousal is easy.
NREM stage 2: Irregular EEG
with sleep spindles (short highamplitude bursts); arousal is more
difficult.
NREM stage 3: Sleep deepens;
theta and delta waves appear; vital
signs decline.
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Typical EEG patterns
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NREM stage 4: EEG is
dominated by delta waves;
arousal is difficult; bed-wetting,
night terrors, and sleepwalking
may occur.
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Sleep Patterns
• Alternating cycles of sleep and
wakefulness reflect natural circadian (24hour) rhythm
• RAS activity inhibited during, but RAS also
mediates sleep stages
• Suprachiasmatic and preoptic nuclei of
hypothalamus time sleep cycle
• Typical sleep pattern alternates between
REM and NREM sleep
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Figure 12.19b Types and stages of sleep.
Awake
REM
Stage 1
NREM
Stage 2
Stage 3
Stage 4
4
5
7
3
6
Time (hrs)
Typical progression of an adult through one night’s sleep stages
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Sleep Disorders
• Narcolepsy - Abrupt lapse into sleep from
awake state
– Treatment
• Insomnia - Chronic inability to obtain
amount or quality of sleep needed
– Treatment
• Sleep apnea - Temporary cessation of
breathing during sleep
– Causes hypoxia
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Memory
• Storage and retrieval of information
• Two stages of storage
– Short-term memory (STM, or working
memory)—temporary holding of information;
limited to seven or eight pieces of information
– Long-term memory (LTM) has limitless
capacity
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Figure 12.20 Memory processing.
Outside stimuli
General and special sensory receptors
Afferent inputs
Temporary storage
(buffer) in cerebral
cortex
Data permanently
lost
Data selected
for transfer
Automatic
memory
Short-term
memory (STM)
Forget
Forget
Data transfer
influenced by:
Retrieval
Excitement
Rehearsal
Associating new
data with stored data
Long-term
memory
(LTM)
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Data unretrievable
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Transfer from STM to LTM
• Factors affecting transfer from STM to
LTM
– Emotional state—best if alert, motivated,
surprised, and aroused
– Rehearsal—repetition and practice
– Association—tying new information with old
memories
– Automatic memory—subconscious
information stored in LTM
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Brain Video
• Shows role of hippocampus in short-term
and long-term memory
• Shows physiology of chemical synapse
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Categories of Memory
1. Declarative (fact) memory
– Explicit information
– Related to conscious thoughts and language
ability
– Stored in LTM with context in which learned
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Categories of Memory
2. Nondeclarative memory
–
–
–
–
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Less conscious or unconscious
Acquired through experience and repetition
Best remembered by doing; hard to unlearn
Includes procedural (skills) memory, motor
memory, and emotional memory
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Figure 12.21a Proposed memory circuits.
Sensory
input
Thalamus
Thalamus
Basal
forebrain
Touch
Prefrontal
cortex
Hearing
Taste
Vision
Smell
Association
cortex
Medial temporal lobe
(hippocampus, etc.)
Prefrontal
cortex
ACh released
by basal
forebrain
Hippocampus
Declarative memory circuits
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Figure 12.21b Proposed memory circuits.
Premotor
cortex
Sensory and
motor inputs
Association
cortex
Basal
nuclei
Thalamus
Premotor
cortex
Dopamine released
by substantia nigra
Basal
nuclei
Thalamus
Substantia
nigra
Procedural (skills) memory circuits
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Molecular Basis of Memory
• During learning:
– Neuronal RNA altered; newly synthesized
mRNA moved to axons and dendrites
– Dendritic spines change shape
– Extracellular proteins deposited at synapses
involved in LTM
– Number and size of presynaptic terminals
may increase
– Presynaptic neurons release more
neurotransmitter
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Molecular Basis of Memory
• Long-term potentiation (LTP)
– Increase in synaptic strength crucial
• Neurotransmitter (glutamate) binds to
NMDA receptors, opening calcium
channels in postsynaptic terminal
– Calcium influx activates enzymes to
• Modifies proteins in pre and postsynaptic
terminals– this strengthens response to the next
stimuli
• Activate genes in postsynaptic neuron to produce
new synaptic proteins
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