Chapter 12 Central Nervous System – Brain
CNS as integration of arcs
• integration center interneurons parallel circuits
• brain
• spinal cord
• connect “appropriate” motor responses to stimuli
• also: learning memory
Central Nervous System
• brain control center
• spinal cord superhighway
• gray matter cell bodies and interneurons
• white matter axons and dendrites
brain functional areas
• integration areas
• connect sensory to motor sensory to sensory other areas (parallel)
Brain
• cerebrum
• cerebellum
• diencephalon
• thalamus
• hypothalamus
• epithalamus
• brain stem
• midbrain
• pons
• medulla oblongata
cerebrum functional areas
• motor
– conscious motor frontal
– eye movement frontal
– speech movement frontal (Broca’s area)
• sensory
– general sensation parietal
– auditory temporal
– visual occipital
– taste parietal
– olfactory temporal , limbic system
other functional structures
• cerebellum coordination of voluntary motor synergist - antagonist
• basal ganglia motor control
• thalamus sensory relay sensory filtering
• hypothalamus visceral control
Hypothalamus
• visceral control center regulates bodily functions
– temperature
– hunger glucose, amino acids
– thirst salts, water
– pH levels CO2
– Autonomic NS
– emotions visceral responses
– endocrine controls Pituitary gland
brain stem
• 3 parts :
– midbrain
– pons
– medulla oblongata
• vital functions
• passageway betw cortex and spinal cord
• cranial nerves
midbrain
• cranial nerves nuclei III , IV
• corpora quadrigemina
– superior colliculi visual reflexes
– inferior colliculi auditory reflexes
• substantia nigra influences basal ganglia produces Dopamine
pons
• cranial nerves nuclei V , VI , VII
• respiratory centers
medulla oblongata
• cranial nerve nuclei VIII, IX, X, XI, XII
• visceral motor nuclei cardiac center HR vasomotor center BP respiratory center resp rate
• reflexes swallow cough sneeze BP , HR , Resp
limbic system
• medial surface of each hemisphere
• emotional brain
– amygdala fear, anger
– cingulate gyrus emotions, gestures
• memory / learning
– hippocampal formation short term memory sends to cortex (LTM)
– amygdala memories of emotions
– hypothalamus visceral responses
• frontal lobe social behaviors
Brain Waves
• measure of electrical activity
• EEG = electroencephalogram
– locates lesions
• inactivity – increase amplitude
• active – complex, low amplitude waves
• Alpha waves 8-13Hz relaxed wakefulness
• Beta waves 14-25Hz alert, concentrating
• Theta waves 4-7Hz abnormal (adults)
• Delta waves < 4 Hz deep sleep, abnormal if awake
consciousness
• sensation change in ion permeability due to a stimulus
• perception conscious awareness of a sensation
• Brain is the organ of perception
• light stimulates receptors = sensation
• vision = our perception of that sensation
• motor responses w/o consciousness:
• plants ; stretch reflex ; BP ; light reflex
problems of consciousness
• syncope brief unconsciousness
• coma unresponsive to sensory stimuli
– not deep sleep decreased O2 use
– may include part of brain stem
sleep
• partial unconsciousness cerebral, not brain stem
• can respond to stimuli
• decreased RAS activity
• Û adenosine increase after ATP use
• Why sleep? restore NT’s organize memories , emotions “we dream to forget”
• insomnia
types of sleep
• NREM non-rapid eye movement
– 4 stages
– slow-wave sleep delta waves
– low vitals increase digestive activity
• REM rapid eye movement
– alpha waves irregular
– increase vitals decrease digestive functions
– skeletal muscles inhibited
– limbic system active
– dreams
memory
• learning changes in synaptic communication
• memory those changes lasting a long time
memory
• declarative facts , events
– short term memory
– long term memory
• non-declarative motor skills, procedures
how do we store memory ?
• synapses work better = LTP long term potentiation
• potentiates neural connections
• sensory - sensory
• sensory – motor
• connect “appropriate” motor responses to stimuli
• build networks - associations
• reverberating circuits
result
• synapses work better = LTP
• more NT receptors
• glutamate - NMDA - Ca
• Û NT production
• NO
• dendritic spines change shape
• Û strength of graded potentials
• greater chance of action potential
where is the memory ?
• middle temporal lobe
– hippocampus STM consolidation
– amygdala fear, danger ; and responses
• cerebral association areas sensory info
• prefrontal cortex behaviors
affects on memory
• repetition increase LTP
• association
– networks
• stress
– norepinephrine
– glucocorticoids
• glutamate
• sleep
• alcohol
memory problems
• amnesia
– anterograde amnesia new info
– retrograde amnesia old info
• post-traumatic stress disorder
• Alzheimer’s Hippocampus cerebral cortex
– change NMDA receptors and Ca++ influx
– decreased Ach production
– plaques : beta amyloid peptide
• stem cells neurogenesis