Upgrade to remove ads
Only $35.99/year

A & P Test 3

Terms in this set (49)

What are the three types of muscle tissue found in the human body?
Skeletal, cardiac, and smooth muscle
Describe the functions of skeletal muscle.
Produce skeletal movement, maintain posture and body position, support soft tissues, ventilation (breathing), and thermoregulation
Define the following terms as they relate to tissue: extensibility, tensile strength, elasticity, and plasticity.
Extensibility: lengthen
Tensile strength: resist lengthening
Elasticity: return from tensile strength
Plasticity: ability of tissue to change (get bigger)
Which tissues have the property of contractility?
Skeletal and cardiac muscles can contract; smooth muscles do not contract
Describe what is meant when a cell is said to be excitable. Explain the two components of this property.
Excitability: capable of being activated by and reacting to stimuli

1. Irritability- the cell is able to respond to a stimuli in its change of polarity

2. Conductivity- ability of cell to take that change in polarity to conduct it a long its membrane
Which tissue have the property of excitability?
Nerve cells, muscle (cardiac/skeletal)
Every cell has a resting membrane potential. What does this mean and how is it maintained?
- This means that the potential inside the cell relative to the extracellular fluid
-Primarily due to ion and protein concentration inside the cell relative to the outside
-Primarily extracellular ion is NA+ while the primary intracellular ion is K+ (Cl- is also important)
What is the difference between a leak channel and a gated channel?
Leak channel: sets the negative resting membrane potential and is always open
-Electrochemical gradient: concentration gradient, polarity (Nernst potential)
-Permeability: membrane is about 100x more permeable to K+

Gated channel: opens and closes to a change in stimulus
-voltage gated: membrane potential
-chemical (ligand) gated: chemical messenger binding to the channel
-mechanical gated: mechanical force
What does the K+-Na+ pump do?
Active transport
-three Na+ ions are pumped out of the cell while two K+ are pumped in
-contributes to the negative resting membrane potential
Due to the electrochemical gradient across a muscle membrane, a rapid influx of Na+ should occur. Why doesn't it when the muscle is in a resting state?
Because in resting membrane potential the membrane threshold has not been reached, therefore the voltage gated Na+ channels do not open
Is it possible for a local change in polarity to occur in a membrane without a resultant action potential? Why or why not?
Yes, because it the change in polarity does not reach the threshold there will be no action potential.
What mechanisms are responsible for sarcolemma depolarization (as part of an AP)?
More Na+ in than K+ out (interior slightly less negative than outside)
-a stimulus causes the inside of the cell to become less negative
What mechanisms are responsible for sarcolemma repolarization (as part of an AP)?
-Voltage gated K+ channels open causing increase diffusion of K+ out of the cell reestablishing the normal resting membrane potential
-The pumps is strongly stimulated by excess Na+ in the cell
What is meant by the absolute and relative refractory periods? When and why do they occur?
Absolute refractory periods: the period from the initiation of the action potential to immediately after the peak. This is the time during which another stimulus given to the neuron will not lead to a second action potential.

Relative refractory periods: this period during which a stronger than normal stimulus is needed in order to elicit an action potential

Absolute refractory period- this period, from the opening of the Na+ channels until the Na+ channels begin to rest to their original resting state

Relative refractory period- follows the absolute refractory period, most Na+ channels have returned to their resting state, some K+ channels are still open, and repolarization is occurring
Describe the structure of skeletal muscles (fascicles, fibers, myofibrils, myofilaments)
Muscle fascicle-surrounded by perimysium (fibrous), composed of muscle cells

Muscle fibers (cell)- surrounded by endomysium (areolar) and sarcolemma, generally runs the entire length of the muscle, multinucleate (peripheral), each fiber is innervated by a terminal end branch, contains several hundred to several thousands myofibrils (functional unit)

Myofibrils: surrounded by sarcoplasm, contractile unit of muscle cells, sarcomeres in series, made up of myofilaments (myosin- thick filaments, actin- thin filaments, elastic filament)
Sets with similar terms