Exam 2

• Membrane potential


  Difference in electrical charge across a plasma membrane
• Membrane potential

  • Unequal concentration of ions across membrane
  • Measured in mV
• Na/K ATPase aka pump

  1. ATP driven

  2. Transports 3 Na+ out

  3. Brings 2 K+ in

  4. Phosphorylation by ATP causes Na+ - K+ pump to undergo conformation change for active transport
• K+ leak channels


  • Maintain resting membrane potential
  • Channels are usually open
  • K+ leaving cell makes cell more negative
• Resting membrane potential


  • Higher [Na+] outside
  • Higher [K+] inside
  • Potential to do work signals
• Equilibrium potentials

  • Ernst equation: Eion = (61/z) log [ion] out/ [ion] in
  • Resting membrane potential = -70 mV standard
• Voltage gated Na+ channel

  1. Closed

  2. GHK equation: 61log Pk[K+] out + PNa[Na+] out / Pk[K+] in + PNa[Na+] in
• Changes in membrane potential

  1. Depolarization: Inside becomes less negative, graph moves upward, closer to action potential

  2. Repolarization: Inside becomes more negative, graph moves downward, pumping Na+ out, returns to resting membrane potential

  3. Hyperpolarization: More negative than resting
• Threshold


  • Above = action potential
  • Below = graded potential
• Action potential


  1. Happens on axon and axon hillock

  2. Long distance

  3. Voltage gated

  4. Voltage gated Ca2+ channels on axon terminal
• Refractory period


  • Ion channels remain close
  • No AP could be generated during absolute refractory period
  • Larger than normal stimulus can initiate new AP during relative refractory period
• Graded potential


  • On soma and dendrites
  • Happens before action potential
  • Not good for long distance bc they decay so it triggers another signal
  • Ligand gated Na channel
• EPSP


  Excitatory postsynaptic potential, depolarization, closer to threshold
• IPSP


  Inhibitory postsynaptic potential, hyperpolarization, moving away from threshold
• Temporal summation


  Two or more stimulus that come from the same presynaptic neuron at different times

  
• Spatial summation


  Two or more stimulus coming from different presynaptic neurons

  
• Saltatory conduction


  Happens because of myelin, the signal jumps the areas with myelin
• Continuous conduction


  Short distance
• Parts of CNS and their functions

  • Basal Nuclei: Influences muscle activity, inhibits unnecessary motor movements, coordinates slow sustained contractions
  • Medulla Oblongata and pons: Vital reflex centers, cardiac, vasomotor, respiratory
  • Hypothalamus, medulla oblongata, and pons: Regulates ANS activities
  • Thalamus: Edits sensory information which is passed on to cerebral cortex, relays motor signals coming out of cerebral cortex
  • Hypothalamus: Contains our biological clock, regulates daily patterns including wake-sleep cycles
  • Cerebral cortex: Memory, integration, interpretation, discrimination, localization, language
  • Spinal cord: Contains many major reflex centers, withdrawal (flexor) reflex, stretch reflex
  • Limbic system: Functional system responsible for emotional behavior
  • Hypothalamus: Regulates body temp
  • Thalamus: Receives and processes sensory info from receptor pathways, perception
  • Midbrain: Involved in eye reflexes, such as pupillary reflex, consensual response, blinking
  • Hypothalamus: Food intake, regulates water balance
  • Spinal cord: Found throughout brain stem, reticular activating system, also involved in motor activities and visceral activities
  • Hypothalamus: Controls several major endocrine functions

  
• Neural synapses


  • Small gap between neuron and neuron: synaptic cleft
  • Electrical signal needs to be transferred to chemical signal

  
• Synaptic communication


  1. Simple diffusion (short distance)

  2. Axon terminal to dendrites

  3. Voltage gated Ca2+ channel open to trigger Neurotransmitter release
• Neurotransmitters


  • Similar to peptide hormones
  • Lipophobic ligand action, can trigger chemically gated ion channels or second messenger cascade
  • Can be excitatory or inhibitory
  • Influenced by drugs and diseases
• Acetylcholine (ACh)


  • Excitatory or inhibitory
  • Locations: Neuromuscular junctions, ANS, CNS
  • Degraded by AChE
• Glutamate


  • Major excitatory neurotransmitter in CNS
  • Linked to memory and learning
• Norepinephrine (NE)


  • Excitatory or inhibitory
  • Locations: ANS (sympathetic), CNS (mood, motivation, alertness)
  • NE transporter for reuptake
• GABA


  • Primary inhibitory neurotransmitter in brain
  • Reuptake into axon terminal and glial cells by GABA transporter
  • Maintains balance
• Divisions of the nervous system

  • Central nervous system (CNS): Brain, Spinal cord
  • Peripheral nervous system (PNS): Cranial nerves, Spinal nerves
• CNS

  • Protected
  • Neural tissue organization: Gray matter (soma), White matter (tracks)
• Spinal cord


  Functions: Reflex and signal transduction
• Lobes of the cerebral cortex

  • Occipital lobe: Vision
  • Parietal lobe: Sensory, body sensation, Homunculus
  • Frontal lobe: Motor, Prefrontal cortex: Reasoning and decision making

  
• Basal ganglia


  • Inside cluster of neurons
  • Affects motor, Dopamine related to Parkinson's disease
• Limbic system


  • Amygdala, Hippocampus, Cingulate gyrus
  • Emotion and memory
  • Cingulate gyrus plays role in emotion
  • Hippocampus involved in learning and memory
  • Amygdala involved in emotion and memory
  • Memory processing requires hippocampus
• Types of long term memory

  • Reflexive (implicit) memory: Learning
  • Declarative (explicit) memory: Requires hippocampus
• Sensory receptors


  • Simple receptors: One cell with free nerve endings can detect pain
  • Complex neuron receptor: One single neuron with free nerve endings enclosed with connective tissues, can detect pressure and touch
  • Nonneural: Requires at least two neurons, special senses receptor, release neurotransmitter, initiates action potential

  
• Properties of a stimulus that CNS must distinguish

  • Nature/modality: Type or form of stimulus
  • Location: Where the stimulus originates or affects the body
  • Intensity: Strength or magnitude of the stimulus
  • Duration: How long the stimulus lasts
• Adrenal medulla


  Secretes adrenaline and noradrenaline, hormones involved in the fight-or-flight response
• Sympathetic nervous system


  • Activates the fight-or-flight response
• Parasympathetic nervous system

  • Promotes rest and digestion
• Neurotransmitters released by preganglionic and postganglionic neurons

  1. Preganglionic neurons release acetylcholine in both sympathetic and parasympathetic systems

  2. Postganglionic neurons release neurotransmitters such as norepinephrine in the sympathetic system and acetylcholine in the parasympathetic system
• Adrenergic receptors


  Receptors used by the sympathetic nervous system