GEN PHYSIO MIDTERMS

• Membrane potential is a fundamental aspect of cellular biology, resembling a microscopic power source.
• Analogous to a battery it maintains a nuanced electrical balance between the interior and exterior of the cell membrane
• • MEMBRANE POTENTIAL : These are electrical potentials that can be seen in the cell membrane that rapidly generates impulses to transmit signals along the nerves, muscles
• MEMBRANE POTENTIAL: It is the difference between the intracellular and extracellular charge of a membrane
• INTRACELLULAR: NEGATIVE
• EXTRACELLULAR: POSITIVE
• Action Potentials: A rapid change in the membrane potential from its resting value due to an influx of sodium ions into the neuron
• sodium is positively charged
• VOLTMETER

  • a highly sophisticated electronic apparatus that is capable of measuring small voltages despite extremely high resistance to electrical flow through the tip of the micropipette which has a lumen diameter usually less than 1 micrometer and resistance more than a million ohms
• RESTING MEMBRANE POTENTIAL happens when there is no transmission of signals or if there is a recession.

  it is always NEGATIVELY CHARGED
• NORMAL RESTING MEMBRANE POTENTIAL VALUE: -90 MILLIVOLTS, -70 MILLIVOLTS
• • Every time that there is a muscle contraction, there is an electrical gradient or potential
• Once there is a spike of signal the resting membrane potential turns into action potential which causes MUSCLE CONTRACTION
• 3 STAGES OF ACTION POTENTIAL: RESTING STAGE, REPOLARIZATION, DEPOLARIZATION
• DEPOLARIZATION STAGE-

  • there is an elicitation of contraction, it is activethere is an INFLUX OF SODIUM gumagalaw; there is an excitation, stimulation and movementrapid increase of positively charged ions (Na+)
• REPOLARIZATION: diffusion of K+ ions to return to normal resting membrane potentialsgoing back to resting stage

  leads to RELAXATION AND

  INFLUX OF CALCIUM IONS

  INHIBITION
• • HYPERPOLARIZATION BEYOND RESTING POTENTIAL, there is too much increased activity or increased spike of action potential (THIS HAPPENS ON THE CELL MEMBRANE)
• SODIUM POTASSIUM PUMP: Cellular mechanism that regulates the balance of sodium (Na+) and potassium (K+) ions across the cell membrane.
• SODIUM POTASSIUM PUMP actively transports three sodium ions out of the cell and two potassium ions into the cell against their respective concentration gradients.
• SODIUM POTASSIUM PUMP

  • This pump utilizes energy from adenosine triphosphate (ATP). It also plays a central role in maintaining the resting membrane potential, supporting nerve signal transmission, muscle contraction, and overall cellular stability.
• VOLTAGE GATING

  • Responds to the changes of the electric across the cell membrane where the ion channels are situated.
  • Allow the selective passage of a particular ion
• VOLTAGE-GATED SODIUM CHANNEL

  • 2 GATES: Activation GATE & InactivationGate
  • HIGHER CONCETRATION TO LOWER CONCENTRATION
• 1. Activation gate opens to enter the sodium ions inside the membrane. Where the content is higher or more abundant, there is the activation gate.
• 1. Inactivation gate closes when sodium ions are enough inside the membrane.
• • SODIUM INFLUX is faster than POTASSIUM
• VOLTAGE-GATED POTASSIUM CHANNEL

  
  

  • This channel opens when the action potential goes from -70m to 0
• HYPERPOLARIZATION - increase in calcium efflux, because potassium gated channels are slow
• ANIONS MAINTAINS THE NEGATIVE CHARGE ENVIRONMENT INSIDE THE CELL
• CALCIUM IONS

  also has voltage gated channel, functions like sodium channel but it is SLOWER

  Contribute to depolarization

  NUMEROUS IN CARDIAC AND SMOOTH MUSCLES
• (SODIUM AND POTASSIUM IS ACTIVE DURING

  SKELETAL MUSCLE CONTRACTION)
• 1. MYELINATED: which has a myelin sheath. During nerve transmissions, the nerve impulse does not go through there; what it does is jump. That is when there is a myelinated Axon.
• 1. UNMYELINATED: its action potential is only direct. They don't have breaks.
• Saltatory Conduction:

  Definition: Action potential jumps between nodes of Ranvier along myelinated axons.Speed: Faster due to "jumping" nature.Energy Efficiency: More efficient, as action potentials occur only at nodes.
• SALTATORY CONDUCTION: SKELETAL MUSCLES (FAST)
• Non-Saltatory Conduction:

  Action potentials propagate continuously along unmyelinated axons.Slower, as action potentials travel the entire length.
• NON SALTATORY CONDUCTION: CARDIAC MUSCLES
• Any event that causes initial rise of membrane potential from -70m to zero, leads to opening of the sodium gated channels - influx of sodium ions into the cell (Positive feedback cycle)
• INITIATION OF ACTION POTENTIAL

  Any event that causes initial rise of membrane potential from -70m to zero, leads to opening of the sodium gated channels - influx of sodium ions into the cell (Positive feedback cycle)
• EXCITATION

  Process of ELICITING APCan be mechanical, chemical or electrical disturbance to the membrane
• Mechanical pressure to stimulate sensory nerve ending in the skin