Biology Unit 4

Neuron Communication: Action Potentials
1. Neurons generate action potentials: rapid changes
  1. What happens to the resting potential when Na+ channels open?
    1. Depolarization!
    2. The internal charge becomes more positive
  2. What happens to the resting potential when K+ channels open?
    1. Hyperpolarization
    2. The internal charge becomes more negative.
  3. Pharmacology of Neurotoxins
    1. Dendrotoxin (Black mamba): - K+ channel blocker.
      1. Homobatrachotoxin in Central American poison arrow/dart frogs. Known to act on voltage-gated sodium channels
    2. Aposematic Warning
      1. Brightly colored (toxins)
2. At rest it is negative on inside compared to outside
  1. For an action potential to occur, the cell membrane must reach a threshold potential
    1. At threshold, more voltage-gated Na+ channels open, allowing Na+ to diffuse rapidly into the cell: DEPOLARIZATION
      1. At the peak of the action potential, Na+ voltage- gated channels begin to close, and K+ voltage-gated channels open in response to the positive membrane potential. This returns the membrane toward resting potential: REPOLARIZATION
        The K+ voltage-gated channels remain open slightly longer than required, and the membrane potential goes below resting. This results in: HYPERPOLARIZATION
Muscles
1. Properties of Muscle Tissue
  1. Contractility
  2. Excitability
  3. Extensibility
  4. Elasticity
  5. 3 Muscle Types
    1. Skeletal, Cardiac, Smooth
      1. Striated v Non striated (smooth)
      2. Voluntary v Involunatry
      3. Uni- v Multinucleate
2. Muscles contract/work against resistance
  1. Origin - not moving
  2. Insertion- moving
3. Motor Units
  1. neuron and muscle cell it excites
  2. we want smaller motor units!
  3. Polio attacks motor unit of spine
  4. Myograph
    1. fused tetanus- smooth steady contraction of a muscle
    2. Warming up and muscle strength
      1. Treppe
        Stair step effect - need to warm up muscles- generate more tension
        release of calcium - buildup!
4. Exercise and Muscle Contration
  1. Isometric
    1. Tension but no load movement
  2. Isotonic
    1. Concentric: muscle shortens
      1. Eccentric: muscle lengthens
5. Energy Sources (all working at once)
  1. direct phosphorylation
    1. Anaerobic Pathway
      1. Glycolosis- 60 seconds
    2. Aerobic pathway
      1. Hours
      2. oxygen required
    3. creatine used to make atp- not a really source 15 seconds
6. Skeletal Muscle Fiber Tissue
  1. genetically determined
    1. Fast twitch (sprinting muscles) tire quickly
    2. Fast twitch Type II A (combo)
  2. slow twitch- how fast myosin heads contract- dark, myoglobin (oxygen carrying)
7. Muscle Homeostasis
  1. Atrophy- muscles shrink
    1. cast, stomach wraps
  2. Hypertophy
    1. HUGE MUSCLES
8. Muscle Malfunctions
  1. Fatigue
    1. Depletion of ATP
      1. Insufficent O2 or glycogen
        Lactic Acid and ADP buildup
        Insufficent ACh from motor neurons
        Decline of Calcium
        Central Fatigue
  2. Spasms
    1. Involuntary twitching
      1. Chemical or pschological
        cramps and tics
        Charley Horse - leg cramps
  3. Rigor Mortis
    1. 3-4 hrs post death
      1. 12 hr - max stifness
        dissipates at 48-60 hours
Chemicals
1. ATP, Calcium, Na, K, ADP
Role of Calcium
1. acetylcholine
Sensory Mechanisms

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Biology Unit 4

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	Created by Marisa Orlow about 9 years ago