Homework 6
Cardiac muscle fibers are joined by special gap junctions call into collated desk; the disc allow heart actively to be costly coordinated
True
The effect of the neurotransmitter on the muscle cell membrane is to temporarily modify its permeability of ions such as Nat and K'
True
The formation of cross bridges requires both calcium ions and ATP
True
The neurotransmitter used by the nervous system to activate skeletal muscle cells is acetylcholine.
True
The sacralplasmic reticulum wraps like a sleeve around the myofibril and stores and releases calcium
True
The striations seen in skeletal muscle are actually alternating dark A and light I bands
True
When a muscle fiber contracts, the I bands nearly disappear, the H zones disappear, and the A bands move closer together but do not change in length.
True
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine ( ACh )
What initiates action potential on a muscle cell?
acetylcholine binding to receptors on the sarcolemma within the neuromuscular junction
What enzyme breaks down acetylcholine into acetic acid and choline to prevent continued contraction of the muscle fiber?
acetylcholinesterase
A myosin head binds which molecule to form a cross bridge?
actin
Which of these increases as muscles age?
amount of connective tissue in a muscle
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cel?
arrival of an action potential
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
arrival of an action potential
What causes the myosin head to disconnect from actin?
binding of ATP
What mineral is released within muscle cells to trigger contraction?
calcium
Striated involuntary muscle tissue is classified as ________ muscle.
cardiac
What type of muscle tissue is both striated And involuntary?
cardiac muscle
Muscle tissue has the abity to shorten when adequately stimulated, a characteristic known as
contractility
The heads of the myosin myofilaments are calledwhen they link the thick and thin filaments together during skeletal muscle contraction.
cross bridges
What is the function of creatine phosphate?
directly regenerates ATP from ADP within a muscle cell
Which layer of connective tissue surrounds each skeletal muscle fiber?
endomysium
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
A smooth, sustained contraction, with no evidence of relaxation, is called
fused, or complete, tetanus
What term describes the ability of a muscle to vary its degree of shortening to generate the strength needed to lift a 5 lb weight, a 7 lb weight, and finaly a 10 lb weight?
graded responses
A motor neuron and all of the skeletal muscle fibers it stimulates are termed a
motor unit
Which of the following is an example of an isometric contraction?
pushing against an immovable wall
What is key to offsetting the effects of aging on the muscular system?
regular exercise
What can older individuals do to increase muscle strength?
regularly use hand weights and practice leg lifts
What causes the power stroke?
release of ADP and Pi
What type of exercise causes increase in muscle size?
resistance exercise
How is acetylcholine (ACh) removed from the synaptic cleft?
simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)
The gap between the axon terminal of a motor neuron and the sarcolemma of a skeletal muscle cell is called the
synaptic cleft
What term refers to a muscle that aids another muscle by producing the same the movement or reducing undesirable movements?
synergist
Which one of the following is composed mostly of the protein myosin?
thick filaments
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
troponin
When an action potential arrives at the axon terminal of motor neuron, which ion channels open?
voltage-gated calcium channels
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate junctional folds of the sarcolemma) and sodium enters the cell.
Striated involuntary muscle tissues found in the heart is
Cardiac Muscle
The perimysium wraps a fascicle of muscle cells and is represented by
Label C
What happens to a muscle when the nerve supplying that muscle is cut?
Muscle paralysis and atrophy occur
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
O O terminal cisterns (cisternae) sarcoplasmic reticulum
Which connected tissue bundles muscle fibers into fascicles
Perimysium
What type of muscle tissue contracts must quickly upon stimulation
Skeletal
The type of muscle tissue pictured in the figure is
Smooth Muscle