The Neuron Nerves Bundles of Axons Same function
The Neuron
Nerves • Bundles of Axons • Same function • Phrenic nerve • Alcohol Overdose
Axonal Membrane of a Neuron
Ion Channels • Cell membrane proteins that pass ions in and out of the cell • Voltage-Gated Ion Channels • gates are regulated by membrane voltage • Chemical-Gated Ion Channels (also called Receptors) • gates are regulated by neurotransmitters • Iontotropic • fast • Metabotropic (G-protein coupled) • requires second messenger cascade • slow
Chemical-Gated Ion Channels Iontotropic Metabotropic
Electrochemical Gradient Inside the Cell Outside the Cell More K+ More Na+ Less K+ Ion Flow Mantra: Na+ In, K+ out
Depolarization/Hyperpolarization
2 Action Potential Phases Rapid 3 1 Threshold Phase 4 Ion responsible 1. Threshold 2. Rapid Depolarization 3. Repolarization 4. After Hyperpolarizatoin Na+ K+ K+ Ion Channel Responsible Chemical-gated Na+ channel Voltage -gated K+ channel Na+/K+ pumps
Na+/K+ Pumps After the Action Potential, Na+/K+ pumps move Na+ ions back out of the cell and move K+ ions back into the cell The movement is against the concentration gradient of each ion so it requires energy (ATP) The pumps move 3 Na+ ions for every 2 K+ ions
Unmyelinated Propagation
Myelinated Propagation
Synaptic Action Voltage-gated Ca 2+ channels Synaptic Potentials: • EPSP • IPSP
Synaptic Potentials • Excitatory Postsynaptic Potential (EPSP) • triggered by excitatory neurotransmitters • open ligand-gated Na+ channels • allows Na+ to flow inside the cell • causing a slight depolarization of the postsynaptic cell • moves the postsynaptic cell closer to firing an action potential • Inhibitory Postsynaptic Potential (IPSP) • triggered by inhibitory neurotransmitters • open ligand-gated K+ channels or Cl- channels • allows K+ to flow out of the cell or Cl- to flow inside the cell • causing a slight hyperpolarization of the postsynaptic cell • moves the postsynaptic cell further from firing an action potential
Brain Organization
Spinal Cord Anatomy Dorsal Ventral Dorsal Horn: Sensory information in Ventral Horn: Motor information out
Brainstem: arousal center (ARAS) sensory in pathway motor out pathway Midbrain Superior Colliculus Inferior Colliculus Pons REM sleep Medulla breathing center cardiac center
Ascending Reticular Activating System (ARAS) Arousal Center
Cerebellum Motor Coordination Fine tuning of: sensory systems emotions learning and memory Autism • decreased cerebellum size
Thalamus and Hypothalamus Thalamus relay station Hypothalamus regulation center
Nucleus Reticularis Thalami NRT: GABA cells Gatekeeper
Hypothalamic Nuclei • hunger/thirst • blood pressure/heart rate • blood pressure/shivering • stress • sex • satiety • memory • reproduction • thermoregulation • circadian rhythms • reproduction
Limbic System Emotion Rewards Memory • smell • aggression • fear learning • memory • recognition memory • smell recognition?
Basal Ganglia Movement Parkinson’s Disease • cell death in • substantia nigra
Frontal: Strategy and Planning Motor area Parietal: Somatosensory area Temporal: Audition, Language Occipital: Vision Cortical Lobes
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