Chapter 9

what events result in the development of rigor mortis?

- calcium is released from the SR - myosin head cannot release - cross bridges form

list in order the events leading to excitation of a muscle fiber

- nerve impulse arrives at distal end of axon - acetylcholine is released - ACh diffuses across synaptic cleft -ACh binds to its receptors on muscle fiber sarcolemma -Permeability of sarcolemma to sodium ions is increased

steps leading to the relaxation of muscles

- nerve signal ceases - acetylcholine release into the synaptic cleft stops; ACh already in the synaptic cleft is broken down - calcium is actively transported into the sarcoplasmic reticulum; ca+2 diffuses away from troponin - troponin returns to its relaxed configuration, causing tropomyosin to cover the myosin binding sites on actin

glycolysis results in the net production of _______________ ATP molecules per glucose molecule

2

the chemical called ______________ is the neurotransmitter for skeletal muscle contraction

Acetylcholine

the aerobic phase of cellular respiration occurs in the organelle called the ______________.

Mitochondria

A neuromuscular junction is the synapse between __________ and ___________.

a motor neuron; a muscle fiber

acetylcholinesterase functions to break down _________________ in the synaptic cleft

acetylcholine

receptors for the neurotransmitter _____________ are found in the sarcolemma at a neuromuscular junction.

acetylcholine

during excitation of a muscle fiber, which one of the following events comes immediately after the release of acetylcholine from the motor neuron?

acetylcholine diffuses accrocs the synaptic cleft

the enzyme ______________ is located on the sarcolemma of the motor end plate and in the synaptic cleft

acetylcholinesterase

In muscle contraction the force that shortens the sarcomeres comes from the myosin cross-bridges pulling on the _____________ filaments.

actin

glycolysis is used to produced ATP for muscle contraction, describe glycolysis.

anaerobic breakdown of glucose to produce ATP

skeletal muscle will be supplied with sufficient oxygen under which two conditions?

at rest; during moderate exercise

neurons have extension (processes) called ___________ that carry electrical impulses toward the cell they are innervating

axons

neurons have extensions (processes) called __________ that carry electrical impulses toward the cell they are innervating

axons

during a muscle contraction, what causes myosin heads to release from their actin binding sites?

binding of a new ATP to myosin head

what causes the myosin head to move into their "cocked" positions prior to them attaching to actin?

breakdown of ATP into ADP

the synaptic _______________ is the gap between a motor neuron and muscle fiber at a neuromuscular junction

cleft

what is the first source of energy used to convert ADP and phosphate to ATP at the start of a contraction?

creatine phosphate

the oxygen needed to recycle lactic acid in the liver and regenerate ATP in the skeletal muscle cells is called oxygen _______________.

debt

A drop in pH and the depletion of glycogen are factors thet lead to muscle _______________

fatigue

prolonged or intense exercise can lead to a condition called muscle ___________, defined as the loss of a muscle's ability to contract

fatigue

what is the immediate result of the opening of sodium channels along the sarcolemma (beyond the motor end plate)

generation of an action potential

muscle cells store glucose in the form of ______________.

glycogen

what is the outcome of the movement of the cocked myosin head?

increase in overlap between the thin and thick filaments

which of the following leads to shortening of sarcomeres?

increasing overlap between thin and thick filaments

what is the function of the enzyme creatine phosphokinase?

it transfers a phosphate group from creatine phosphate to ADP to form ATP

during high intensity exercise, anaerobic metabolism results in the production of pyretic acid, which is then converted to ___________ acid.

lactic

neuron that control sensory neurons are called ____________ neurons

motor

effectors such as skeletal muscles are controlled by what type of neuron?

motor neurons

what causes muscles to shorten during contraction

muscles shorten because individual sarcomeres shorten

a cross bridge is best described as a ___________

myosin head bound to actin

what type of chemical is released by neurons? These chemicals then bind to effector cells.

neurotransmitters

the role of tropomyosin and troponin is best described as ___________

regulatory proteins

what phases include these events (1) myosin releases thin filaments (2) muscle tension declines (3) cytoplasmic calcium levels fall

relaxation

during which phase are calcium ions actively transported into the sarcoplasmic reticulum?

relaxation phase

Since the shortening of ______________ results in shortening of entire skeletal muscles, these structures are called the functional units of skeletal muscles

sarcomeres

Name the three types of muscles

skeletal, smooth, cardiac

The binding of acetylcholine to its receptors on the motor end plate results in increased membrane permeability to _________________ ions and potassium ions.

sodium

action potentials spending along the sarcolemma of a muscle fiber result from the opening of ____________ channels in the sarcolemma

sodium

what is the term for the functional connection between a neuron and its effector?

synapse

the tiny vesicles in motor neurons that store neurotransmitters are called ______________ vesicles.

synaptic

what is the name of the space between a motor neuron and a muscle fiber at neuromuscular junction?

synaptic cleft

excitation-contraction coupling results in linkages being formed between the ________________ and ________________ filaments, resulting in contraction of the muscle fiber

thick and thin

name the proteins involved in blocking the binding sites on actin molecules, resulting in the inability of myosin to bind to the thin filaments

tropomyosin and troponin

true or false: ATP is needed for both muscle contraction and muscle relaxation

true

true or false: the sarcoplasmic reticulum releases calcium into the cytoplasm when a muscle impulse moves down into the muscle fiber along the T tubules

true

true or false: thick and thin filaments do not change length during a muscle contraction

true

when is acetylcholine released into the synaptic cleft of a neuromuscular junction?

when a nerve impulse reaches the end of the axon