A&P 2.15 Action Potential or Nerve Impulse Flashcards
Iliopsoas
A, I, O
A - hip flexion, major postural muscle
I - iliacus muscle and lesser trochanter
O - vertebral bodies, anterior discs of T12-L5 and TP of L1-L5, iliac fossa
Iliopsoas
Two muscles
Iliacus And psoas major
Strongest hip flexor
Iliacus
A, I, O
A - origin fixed: flex the hip
Insertion fixed: flex the trunk toward the thigh
I - lesser trochanter
O - iliac fossa
Named for location: ilium, loin
Psoas major
A, I, O
A - origin fixed: flex the hip
Insertion fixed: flex trunk toward the thigh
Unilaterally- assist to laterally flex the lumbar spine
O - bodies of the transverse process of lumbar vertebrae
I - lesser trochanter
Ribs are what to the transverse processes they attach to
Anterior
Lesser trochanter
Posterior medial
Inferior to the greater trochanter
Ions
Electrically charged atoms or molecules
Positive or negatively charged
Ions
Three states
Neutral atoms - equal number of protons and electrons
Negative ions - have more electrons
Positive ions - have fewer electrons
Number of protons do not change
Most plentiful outside cell ions
NA+ sodium
CL- chlorine
Most plentiful ion intercellular
K+ potassium
Membrane potential
A difference in electrical charge across the plasma membrane caused by differing concentration of ions across a membrane
Called a potential because it is a type of stored energy called potential energy
Every cell in the body maintains a membrane potential
A membrane that exhibits a membrane potential is said to be polarized
Resting membrane potential
When a neuron is not conducting electrical signals is said to be “resting”
-70 mV
What can generate action potentials?
Only muscle cells and neurons can generate an action potential
Action potential
An impulse results when ions are allowed to move toward each other
Sodium-potassium pump
The mechanism in the plasma membrane actively pumps sodium ions (Na+) out of the neuron (cell) and potassium ions (K+) into the neuron at an unequal rate (3:2)
Local potentials
In neurons, membrane potentials can fluctuate above or below the resting membrane potential in response to certain stimuli
A slight shift away from resting membrane potential in a specific region of the plasma membrane is often called a local potential
Excitation
When any stimulus causes gates or channels to open and causes the RMP to reach -59 MV
Called depolarization
Inhibition
Movement of the membrane potential away from zero below usual RMP called hyperpolarization
Action potential
The membrane potential of an active neuron while conducting an impulse
Action potential
Same as spreading wave
Refractory period
A brief period during which a local area of an axon’s membrane resists re-stimulation for about 1/2 millisecond after then membrane surpasses the threshold potential, IT WILL NOT RESPOND TO ANY STIMULUS NO MATTER HOW STRONG (absolute) or VERY STRONG (relative)
How do anesthetics affect pain?
Block ability of nerve potential to continue by binding to the postsynaptic nerve receptors
Action potential process
6 Steps
Stimulus Threshold potential reached Action potential peaks Repolarization Hyperpolarization Resting potential restored
Stimulus
Anything that changes the resting membranes potential (-70 Mv)
Triggers stimulus gated Na+ channels to open
Allows Na+ inward diffusion
MEMBRANE DEPOLARIZES (Decreases from -70 Mv toward -59 Mv)
Threshold potential reached
Membrane reaches -59 Mv
Voltage gated Na+ channels open
Action potential peaks
More Na+ enters cell
Depolarization continues until +30 Mv
ACTION POTENTIAL PEAKS AT +30 Mv
Voltage gated Na+ channels close
Repolarization
Moving back toward resting membrane potential (-70 Mv)
Begins when voltage gated K+ channels open
Allows outward diffusion of K+
Hyperpolarization
K+ exits cell and moves toward resting membrane potential (-70 Mv)
Membrane potential increases beyond resting membrane potential to -100 Mv
HYPERPOLARIZATION ABOVE -70 Mv
Resting potential restored
Sodium-potassium pump activates to restore resting membrane potential (-70 Mv)
Decreases membrane potential from -100 Mv (hyperpolarization) to normal (-70 Mv)
Ion channels return to resting state
All or none phenomenon
Each action potential is all or nothing
If the threshold (-59 Mv) is surpassed, the full peak action potential is always reached
If threshold potential is not surpassed, no action potential will occur at all
How does myelin affect conduction of the action potential
Myelinated greatly increases the speed due to nodes of Ranviea
