Phys lab #2
Terms in this set (34)
Pithing destroys the frog's ________, but leaves the _______ intact.
brain and spinal cord
Is the frog used in the lab single or double pithed?
How long are the frog's tissues viable after pithing?
minutes to hours
What are the characteristics of Ringer's solution?
Same isotonic ion concentration as amphibian ECF
What 2 functions does Ringer's solution perform?
1) Keeps tissues moist
2) ensures correct ions present
What 2 factors allow oxygen to be supplied to a pithed frog's tissues?
1) moist skin
2) pumping heart
How are the frog's enzymes different from mammalian enzymes?
The frog's muscles will work at room temperature because is enzymes are not as temperature dependent as mammalian enzymes.
In the lab, we isolated the _______ nerve and the _______ muscle.
Skeletal muscles are connected to bones by
Skeletal muscles are composed of hundreds to thousands of individual cells called
The term motor unit refers to
one motor neuron and all of the skeletal muscle fibers it innervates
The motor neuron and muscle fiber intersect at what is called
A twitch is
one contractile response to a single action potential
An action potential in a motor neuron triggers the release of which neurotransmitter?
The term skeletal muscle fiber refers to
an individual skeletal muscle cell
The graded depolarization in the skeletal muscle fiber that is elicited in response to one action potential from the motor neuron is called
EEP - end plate potential
Which phase is not a phase of a skeletal muscle twitch?
A sufficiently strong electrical stimulus applied to an isolated, mounted skeletal muscle induces the development of muscle force, or muscle tension. Which is the true statement?
The electrical stimulus mimics acetylcholine release at a neuromuscular junction
Define the terms skeletal muscle fiber, motor unit, skeletal muscle twitch, electrical stimulus, and latent period
Skeletal muscle fibers are the individual cells that are bound together in fascicles. Many fascicles are bound together to make a muscle.
A motor unit consists of a motor neuron and all of the muscle fibers in innervates.
A skeletal muscle twitch is a mechanical response to a single action potential.
During this experiment, we used an electrical stimulus to mimic the contractions of skeletal muscles. It is done in vitro to produce in vivo results.
Latent period is the period of time between the generation of an action potential in a muscle cell and the start of muscle contraction.
Describe the process of excitation-contaction coupling in skeletal muscles fibers.
EC coupling is the entire process starting from the release of ACH that creates a graded potential, leading to the end-plate potential. The end-plate potential triggers a series of events that result in the contraction of a muscle cell
3 phases of a skeletal muscle twitch
1) Latent period - the period of time between the generation of an action potential in a muscle cell and the start of a muscle contraction
2) Contraction phase - starts at the end of the latent period and ends when the muscle tension peaks
3) Relaxation phase - period of time from peak tension until the end of muscle contraction.
Does the duration of the latent period change with different stimulus voltages?
The latent period never changes no matter the force
At the threshold stimulus, do sodium ions start to move into or out of the cell to bring about the membrane depolarization?
Na ions flow into the cell to bring about depolarization
Skeletal muscle fibers are innervated (stimulated) by
A single action potential propagating down a motor axon results in
a single action potential and a single contractile event in the muscle fibers it innervated
In resting skeletal muscle, calcium is stored in
the sarcoplasmic reticulum
During the latent period for an isometric contraction
the cellular events involved in excitation-contraction coupling occur
Motor unit recruitment refers to
an increase in the number of active muscle fibers to increase the force developed in a muscle
Active tension (or force) in a skeletal muscle fiber results from
activation of cross bridge cycling via increase intracellular calcium levels.
The ____ is the minimal stimulus needed to cause a depolarization of the muscle plasma membrane (sarcolemma).
Be definition, the ______ is the amount of stimulus required to successfully recruit all the muscle fibers into developing active force
Why was a maximal voltage observed in this experiment?
at the maximum voltage, all the muscle fibers contained in this muscle are depolarized and they all develop active force (that is, they were all successfully recruited)
Describe the effect of increasing stimulus voltage on isolated skeletal muscles
From threshold voltage as the stimulus increases, so does the force of the contraction until it reaches maximum voltage. At this level, the more stimulus, the muscle will still contract with the same force
What happens in the isolated skeletal muscle when the maximal voltage was applied?
It contracted with maximum tension and even with the voltage was increased, the tension stayed at the maximum level