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Nerve System and Muscle Contractions
Terms in this set (76)
A simple nervous system
_______ includes sensory information, an integrating center, and effectors.
Most of the neurons in the human brain are
The nucleus and most of the organelles in a neuron are located in the
The point of connection between two communicating neurons is called the
A neuron's nucleus is located in its _____.
A nerve impulse moves away from a neuron's cell body along _____.
An impulse relayed along a myelinated axon "jumps" from _____ to _____.
node of Ranvier ... node of Ranvier
Axons insulated by a(n) _____ are able to conduct impulses faster that those not so insulated.
What type of cell makes up the myelin sheath of a motor neuron?
What part of a neuron relays signals from one neuron to another neuron or to an effector?
Functionally, which cellular location is the neuron's "decision-making site" as to whether or not an action potential will be initiated?
Although the membrane of a "resting" neuron is highly permeable to potassium ions, its membrane potential does not exactly match the equilibrium potential for potassium because the neuronal membrane is also
slightly permeable to sodium ions.
The operation of the sodium-potassium "pump" moves
sodium ions out of the cell and potassium ions into the cell.
A cation that is more abundant as a solute in the cytosol of a neuron than it is in the interstitial fluid outside the neuron is
After the depolarization phase of an action potential, the resting potential is restored by
the opening of voltage-gated potassium channels and the closing of sodium channels
In the sequence of permeability changes for a complete action potential, the first of these events that occurs is the
opening of voltage-gated sodium channels.
Saltatory conduction is a term applied to
jumping from one node of Ranvier to the next in a myelinated neuron.
Which of these causes the release of neurotransmitter molecules?
an action potential reaching the end of the axon
The space between an axon of one neuron and the dendrite of another neuron is called a(n) _____.
Neurons store neurotransmitter molecules in vesicles located within _____.
In a simple synapse, neurotransmitter chemicals are released by
the presynaptic membrane.
Transmission of information across the synaptic cleft
Where are neurotransmitter receptors located?
the postsynaptic membrane
For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the
hyperpolarization of the neuron.
A graded hyperpolarization of a membrane can be induced by
increasing its membrane's permeability to K+.
An inhibitory postsynaptic potential (IPSP) occurs in a membrane made more permeable to
When several EPSPs arrive at the axon hillock from different dendritic locations, depolarizing the postsynaptic cell to threshold for an action potential, this is an example of
Neurotransmitters categorized as inhibitory are expected to
hyperpolarize the membrane
The major inhibitory neurotransmitter of the human brain is
An amino acid that operates at inhibitory synapses in the brain is
During the course of muscle contraction the potential energy stored in ATP is transferred to potential energy stored in _____.
the myosin head
The release of _____ ions from the sarcoplasmic reticulum is required for skeletal muscle contraction.
Myosin heads bind to _____, which they then pull and cause to slide toward the center of the sarcomere.
Of these events, the first to occur when a motor neuron stops sending an impulse to a muscle is _____
the pumping of calcium ions out of the cytoplasm and back into the sarcoplasmic reticulum
The thick filaments of sarcomeres are composed of _____.
The thin filaments of sarcomeres are composed of _____.
A single muscle cell is referred to as a _____.
Which muscle type is involved in the function of the digestive tract and blood vessels?
How does cardiac muscle differ from the other types of muscle?
It contains branched cells.
True or false? Myofibrils are the alternating light-dark units that produce the banded appearance of muscle fibers.
Which molecules form the thick filaments of sarcomeres?
Which of the following interactions is the molecular basis of muscle contraction?
Myosin and thin filaments
Which step constitutes the power stroke of muscle contraction?
The phosphate ion is released, and the myosin head moves back to its original position.
Which of the following statements about the stimulation of muscle cells is true?
An action potential in a muscle cell ultimately results in the release of calcium ions into the cell.
The contraction of skeletal muscles is based on
myosin cross-bridges binding to actin and transitioning from a high-energy to a low-energy state.
The calcium ions released into the cytosol during excitation of skeletal muscle bind to
The muscles of a recently deceased human can remain in a contracted state, termed rigor mortis, for several hours, due to the lack of
ATP needed to break actin-myosin bonds.
Calcium ions initiate sliding of filaments in skeletal muscles by
binding to the troponin complex, which then relocates tropomyosin.
In a relaxed skeletal muscle, actin is not chemically bound to
Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber?
1. Tropomyosin shifts and unblocks the cross-bridge binding sites.
2. Calcium is released and binds to the troponin complex.
3. Transverse tubules depolarize the sarcoplasmic reticulum.
4. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP.
5. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane.
5 → 3 → 2 → 1 → 4
The "motor unit" in vertebrate skeletal muscle refers to
one motor neuron and all of the muscle fibers on which it has synapses.
Sustained muscle contraction without relaxation between successive stimuli is called
What do the orange bars on the graph represent?
the percentage of slow muscle fibers in individuals with different athletic abilities
According to the graph, which type of muscle fiber predominates in endurance athletes (marathon runners and extreme endurance athletes)?
The percentage of intermediate muscle fibers plus fast muscle fibers in world-class sprinters is approximately the same as the percentage of slow muscle fibers in ____________.
a world-class marathon runner
The muscle cell and its motor neuron
the following statements correctly describe(s) T tubules and their role in conducting action potentials in muscle cells?
-T tubules carry action potentials into the interior of the muscle cell via voltage-gated Na+ and K+ channels.
-Without T tubules, the muscle cell would not be able to contract.
-T tubules are infoldings of the plasma membrane that encircle the myofibrils and are in contact with the sarcoplasmic reticulum.
Structure of the sarcomere
Drag the labels to their appropriate locations on the diagram below, indicating the function of each structure during muscle contraction.
Contraction of the sarcomere: the sliding-filament model
Which of the following statements correctly describe(s) the relationship between Ca2+ concentration in the cytosol and the response in the sarcomere?
-Increasing Ca2+ concentration causes movement of tropomyosin, exposing myosin-binding sites on actin.
-Decreasing Ca2+ concentration causes dissociation of Ca2+ from troponin.
Which of the following statements correctly describes why a series of closely spaced action potentials causes a sustained contraction rather than a series of closely spaced twitches?
When a series of action potentials is closely spaced, there is not sufficient time for Ca2+ uptake into the sarcoplasmic reticulum between action potentials, and Ca2+ remains bound to troponin throughout the series.
The large surface area in the gut directly facilitates
In the digestive system, peristalsis is
smooth muscle contractions that move food along the esophagus.
After ingestion by humans, the first category of macromolecules to be chemically digested by enzymes in the mouth is
Salivary amylase digests
Digestive secretions with a pH of 2 are characteristic of the
Pepsin is a digestive enzyme that
begins the hydrolysis of proteins in the stomach.
Upon activation by stomach acidity, the secretions of the parietal cells
initiate the digestion of protein in the stomach.
The bile salts
emulsify fats in the duodenum.
The absorption of fats differs from that of carbohydrates in that the
most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood
The cells that secrete the acidic components of stomach juices are
in the lumen of the stomach
Stomach cells are moderately well adapted to the acidity and protein-digesting activities in the stomach by having
a thick, mucous secretion and active mitosis of epithelial cells.
Which of the following organs is incorrectly paired with its function?
large intestine--bile production
Which of the following is not a major activity of the stomach?
After surgical removal of an infected gallbladder, a person must be especially careful to restrict dietary intake of
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