Membranes And Muscle Contraction Flashcards
What is voltage?
Electric potential difference
What is resistance?
Opposition to the passage of electrical current
Which way does sodium want to go?
In the cell
Which way does potassium want to go?
Out of the cell
What is the normal resting potential of a cell?
-70mV
What is the absolute refractory state?
Time when another action potential cannot be generated
What is the relative refractory period?
Time when a stronger than normal stimulus could trigger another action potential
What ion ratio does the na-k pump, pump?
3 na out
2 k in
What is hyperkalemia?
Increased extra cellular k+ resulting in cell being more excitable
What is hypokalemia?
Decrease in extra cellular k+ leading to less excitable cell
What affect does increasing the Ca++ have?
Makes cell less excitable
What affect does decreasing the Ca++ have?
Makes cell more excitable
What is the neuromuscular junction?
Site of innervation
What does the sarcoplasmic reticulum primarily do?
Store and release Ca++
What are terminal cisternae?
Enlarged portions of SR nearest t-tubules
What are transverse tubules?
Tube through which action potentials propagate into muscle near SR
What is the A-band?
Dark, myosin band
What is the I-band?
Light actin filaments and z line
What is the H-zone
Center of A band with just myosin
What is the M-line?
Center or H-zone to which myosin anchors
What are titins?
Proteins that anchor thick filaments to z-discs. Helps muscle spring back
Which sections shorten during contraction?
I-band
H-zone
Sarcomere
How do calcium, troponin and tropomyosin interact?
Calcium binds troponin which shifts and pulls tropomyosin over to expose binding sites on actin for myosin
What are the 9 main events of skeletal muscle contraction?
1-AP initiates 2-AP triggers release of Ach 3-Ach diffuses to muscle fiber 4-Local depolarization occurs 5-EPP triggers AP in muscle 6-AP triggers release of Ca++ from SR 7-Ca++ binds troponin, shifting tropomyosin 8-Energized myosin binds actin and shortens 9-Cytoplasmic ca++ is pumped back to SR
What are the 3 energy sources for muscle contraction?
Creatine phosphate- 1 ATP Anaerobic respiration (glycogen)- 2ATP Cellular respiration (aerobic)- 38ATP, heat water and CO2
What is isotonic contraction?
Tension force is greater than load and muscle shortens
What is isometric contraction?
Load exceeds tension and muscle does not shorten
What is type 1 motor units?
Slow twitch- always active
What is type 2 motor units?
Fast twitch
6 basic components of reflex?
1-sensory receptor 2-sensory/afferent neuron 3-integration to CNS 4-interneuron 5-motor/efferent 6-an effector
What is a stretch reflex?
Spindles sensitive to muscle length. Activated alpha motor neurons and Stimulates muscle to contract. Knee jerk
What are the subtypes of muscle fibers?
Extrafusal-innervated by alpha motor neurons
Intrafusal- innervated by gamma motor neurons
What is a Golgi (deep) tendon reflex?
Reflex sensitive to tendon tension causing muscle to relax by inhibiting alpha motor neurons
What is current?
Flow of electrical force
What do extrafusal muscle fibers do?
Provide force of contraction
What do intrafusal muscle fibers do?
Detect fast (group Ia) and static changes (group II)
