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Terms in this set (58)
The T tubules:
provide a means of rapidly transmitting the action potential from the surface into the central portions of the muscle fiber.
The larger the motor units within a muscle, the more precisely controlled the gradations of contraction. t/f
The first means by which ATP is produced at the onset of contractile activity is:
transfer of energy and phosphate from creatine phosphate to ADP
What is the fate of ACh following binding to receptors?
It is removed by the enzyme acetylcholinesterase.
The sympathetic branch of the autonomic nervous system has its cells of origin in the brain stem as well as the spinal cord. t/f
Thick filaments in skeletal muscle are composed of:
What are the intracellular signal for contraction?
A motor unit refers to:
a single motor neuron plus all of the muscle fibers it innervates.
The terminals of both autonomic nerve fibres and motor neurons end in a single, enlarged knoblike structure that releases neurotransmitter. t/f
What system would suppress the digestive organs during times of greater physical activity?
Skeletal muscle fibers are formed during embryonic development by the fusion of many smaller cells. t/f
Which of the following is the final signalling step following impulse conduction along the axon terminal of a motor neuron?
ACh binds with receptors on the muscle cell membrane, opening sodium channels.
Calcium turns on cross bridges by physically repositioning the troponin-tropomyosin complex to uncover the actin cross-bridge binding sites in:
both skeletal and cardiac muscle.
binds with calcium to initiate sarcomere shortening
Rigor mortis occurs when Ca2+ links actin and the myosin globular head together in a rigor complex. t/f
The sarcoplasmic reticulum stores ____ when a muscle is relaxed and releases it for binding to ____ during contraction.
Select the correct statement about the summation of simple twitches.
The twitches from action potentials add together
Gap junctions are only found in cardiac muscle. t/f
The parasympathetic nervous system inhibits the rate of heartbeat. t/f
Sympathetic stimulation of the gallbladder relaxes the activity of this organ. t/f
An action potential rapidly spreads to the central portions of a muscle cell by means of the:
During an isotonic contraction of a muscle in the arm:
The tension in the muscle remains constant.
A skeletal muscle undergoes hypertrophy mainly by producing many more muscle fibers. t/f
The strength and rate of contraction of the heart can be influenced by the autonomic nervous system. t/f
The preganglionic fibres of the autonomic nervous system are cholinergic fibres. t/f
Which statement characterises sympathetic activity?
The pupils of the eye dilate
Parasympathetic postganglionic fibres secrete the neurotransmitter ____________________.
The output zone includes the
Which of the following is not a graded potential?
A postsynaptic neuron can either excite or inhibit a presynaptic neuron. t/f
Neurotransmitters do not always bind to receptors attached to ion channels. t/f
If a concentration or electrical gradient is present for a given substance, the substance will always passively permeate the membrane. t/f
At resting potential, the outside of the cell is negative compared to the intracellular fluid. t/f
Which statement regarding graded potentials is false?
They are self-propagating
The conduction velocity of a nerve impulse is slower in myelinated fibers than in unmyelinated fibers because myelin acts as an insulator that slows down the flow of current. t/f
Communication between neurons occurs by the release of chemical messengers termed?
At an excitatory synapse
There is increased permeability of the postsynaptic membrane to both Na and K
In addition to the concentration gradient, what else affects the movement of ions across plasma membranes?
The Na+/K+ pump plays the primary role in establishing the membrane potential in neurons. t/f
Chemically gated ion channels are predominantly located in dendrite membranes compared to axonal membranes. t/f
A spike is another name for the axon of a neuron. t/f
What cells form myelin around neurons in the peripheral nervous system?
When EPSPs originating from a single presynaptic input occur in close succession such that they add together or sum, thereby bringing the postsynaptic cell to threshold, it is called
The Na+/K+ pump
pumps K+ into the cell.
What is the positive ion that tends to passively leak out of cells.
When a neuron starts to depolarise, what ions move into the cell?
The period of time following an action potential during which a membrane cannot be restimulated, no matter how strong the stimulus, is known as the subminimal response period. t/f
What ion is more concentrated in the extracellular fluid (ECF)?
The nerve fiber is another name for the nucleus of a neuron. t/f
At what potential, typically around -55 mV, does rapid depolarization occurs?
The space between the presynaptic and postsynaptic neurons is known as a
What type of voltage-gated ion channels are found in axon terminals that when operational induce neurotransmitter release?
A given synapse is always excitatory or inhibitory. t/f
What happens to the diffusion rate as the distance increases?
Membrane potential is related to the uneven distribution of what two positively charged ions?
sodium and potassium
At the end of repolarisation, the newly opened channels for which ions close?
The junction between two neurons is known as a
A given synapse may produce EPSPs at one time and IPSPs at another time. t/f
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