Lab Exam 1 Notes Contd Flashcards
the contraction of skeletal and cardiac muscle fibers can be considered in terms of 3 events – … of the muscle cell, …., and shortening of the muscle cell due to … within it
electrical excitation; excitation contraction coupling; sliding of the myofilaments
because the plasma membrane is more permeable to … than to …, the cell’s resting membrane potential is more negative inside than outside
K+; Na+
the resting membrane potential is of particular interest in excitable cells, like muscle cells and neurons, because changes in that voltage underlie their ability to … (to … and/or …)
do work; contract; issue electrical signals
when a muscle cell is stimulated, the sarcolemma becomes temporarily more permeable to sodium ions, which enters the cell. this sudden influx of sodium ions alters the membrane potential, such that the cell interior becomes less negatively charged – ….
depolarization
when depolarization reaches a certain level and the sarcolemma momentarily changes its polarity, a depolarization wave travels along the sarcolemma. even as the influx of sodium occurs, the sarcolemma becomes becomes less permeable to sodium and more permeable to potassium, which moves out of the cell –
repolarization
the … is the period of time when sodium permeability of the sarcolemma is rapidly changing and maximal, and the following period when sodium permeability becomes restricted. during this period there is no possibility of generating another action potential
absolute refractory period
as sodium permeability is gradually restored to resting levels during repolarization, an especially strong stimulus to the muscle cell may provoke another action potential –> …
repolarization restores the muscle cell’s normal excitability
relative refractory period
if the muscle cell is stimulated to contract rapidly repeatedly, the changes in sodium and potassium concs near the membrane begin to reduce its ability to respond. the … must become more active to reestablish the ionic concs of the resting state
sodium-potassium pump
Propagation of the action potential along the sarcolemma causes the release of …. from storage in the … within the muscle cell.
calcium ions (Ca2+); sarcoplasmic reticulum;
When the calcium ions bind to the regulatory protein… on the actin myofilaments, they act as an ionic trigger that initiates …, and the actin and myosin filaments slide past each other. Once the action potential ends, the calcium ions are almost immediately transported back into the sarcoplasmic reticulum. Instantly the muscle cell relaxes.
troponin; contraction;
Muscle cell contraction is initiated by generation and transmission of an …along the sarcolemma. This electrical event is coupled to the sliding of the …—contraction—by the release of calcium ions (Ca2+).
action potential ; myofilaments;
generally there is … with ATP alone. There is … with the salt solutions alone. … occurs in the presence of ATP and the proper concs of potassium and magnesium ions
little or no contraction; no contraction; maximum contraction
a single contraction of skeletal muscle is called a …
a tracing of this shows three distinct phases: latent, contraction, and relaxation
muscle twitch
the … is the interval from stimulus application until the muscle begins to shorten. although no activity is indicated on the tracing during this phase, … is occurring within the muscle
latent period; excitation-contraction coupling;
during the …, the muscle fibers shorten; the tracing shows an increasingly higher needle deflection and the tracing peaks
period of contraction
during the .., represented by a downward curve of the tracing, the muscle fibers relax and lengthen
period of relaxation
If a muscle is stimulated with a rapid series of stimuli of the same intensity before it has had a chance to relax completely, the response to the second and subsequent stimuli will be greater than to the first stimulus. This phenomenon, called …, or …, occurs because the muscle is already in a … state when subsequent stimuli are delivered.
wave summation; temporal summation; partially contracted;
voltage that produces the maximal strength of contraction, and is the weakest stimulus at which all muscle cells are being stimulated: …
maximal stimulus
Stimulation of a muscle at an even higher frequency will produce a “fusion” (complete tetanization) of the summated twitches. In effect, a single sustained contraction is achieved in which no evidence of relaxation can be seen. …, or …, demonstrates the … generated by a skeletal muscle
Fused tetanus; complete tetanus; maximum force
… is a reversible physiological condition in which a muscle is unable to contract even thought it is being stimulated. it can occur with short-duration maximal contraction or long-duration submaximal contraction
muscle fatigue
several factors contribute to muscle fatigue, most of which affect …
one theory involves the buildup of … from ATP and creatine phosphate breakdown, which may block …
another theory suggests that … in the T tubules may block ca release from the SR and alter the membrane potential of the muscle fiber
excitation-contraction coupling; Pi; calcium release from the SR; potassium accumulation
When the fibers of a skeletal muscle are slightly stretched by a weight or tension, the muscle responds by …and thus is capable of doing more work. When the actin and myosin barely overlap, sliding can occur along nearly the entire length of the actin filaments. If the load is increased beyond the optimum, the latent period becomes longer, contractile force decreases, and… (fatigue) occurs more quickly. With excessive stretching, the muscle is unable to develop any active tension and no contraction occurs. Since the filaments no longer overlap at all with this degree of stretching, the sliding force cannot be generated.
contracting more forcibly; relaxation;
A single skeletal muscle consists of numerous elongated skeletal muscle cells, also called skeletal muscle …. These muscle cells are excited by motor neurons of the central nervous system whose axons terminate at the muscle. an axon of a motor neuron branches profusely at the muscle. each branch produces multiple …, each of which innervates a single fiber
fibers; axon terminals
the most important organizational concept in the physiology of muscle contraction is the …, a single motor neuron and all of the cells within a muscle that it activates
motor unit
a muscle consists of multiple motor units and the gradual and coordinated activation of these motor units results in … of the whole muscle
graded contraction
the nervous system controls muscle contraction by two mechanisms:
…: the gradual activation of more and more motor units
…: an increase in the frequency of nerve impulses for each active motor unit
recruitment (multiple motor unit summation);
temporal (wave) summation
…: constant state of slight excitation of a muscle while it is in the relaxed state. even while “at rest,” a small number of motor units to a skeletal muscle remain slightly active to prepare the muscle for possible contraction
tonus
graded muscle contractions, which represent increasing levels of force generated by a muscle, depend upon:
- the gradual …
- increasing the … for each active motor unit. this permits a range of forces to be generated by any given muscle or group of muscles, all the way up to the …
activation of more motor units;
frequency of motor neuron action potentials; maximum force
the … is the second major control system of the body, and acting with the nervous system, it helps coordinate and integrate the activity of the body
endocrine system
the endocrine system uses chemical messengers, or …, which enter the blood to be transported throughout the body
hormones
organs that respond to a particular hormone are referred to as the … of that hormone. the ability of the target tissue to respond depends on the ability of the hormone to bind with … occurring on the cells’ plasma membrane or within the cells
target organs; specific receptors
endocrine glands release their hormones directly into the …, from which the hormones enter the blood or lymph
the exocrine glands release their products at the … or upon an … via ducts
extracellular fluid; body’s surface; epithelial membrane
the pituitary gland, or …, is located in the sella turcica of the sphenoid bone. it consists largely of two functional lobes, the …, or …, and the …, consisting of the … and the …. – the stalk that attaches the pituitary gland to the hypothalamus
hypophysis;
adenohypophysis; anterior pituitary;
neurohypophysis; posterior pituitary; infundibulum
the anterior pituitary produces and secretes a number of hormones, four of which are …,
tropic hormones
the target organ of a tropic hormone is another …, which secretes its hormone in response to stimulation
endocrine gland
because the anterior pituitary controls the activity of many other endocrine glands, it has been called the …
however, because … or … hormones from neurons of the ventral hypothalamus control anterior pituitary cells, the hypothalamus has superseded the anterior pituitary as the major controller of endocrine glands
master endocrine gland; releasing; inhibiting
(anterior pituitary tropic hormones) … and … - regulate gamete production and hormonal activity of the gonads (ovaries and testes0
gonadotropins-follicle-stimulating hormone (FSH); luteinizing hormone (LH)
(anterior pituitary tropic hormones) … regulates the endocrine activity of the adrenal cortex
adrenocorticotropic hormone
(anterior pituitary tropic hormones) … or … influences the growth and activity of the thyroid gland
thyroid-stimulating hormone; thyrotropin
other important hormones produced by the anterior pituitary are not directly involved in the regulation of other endocrine glands of the body:
… – general metabolic hormone that plays an important role in determining body size – hyposecretion results in dwarfism in children and hypersecretion causes gigantism in children and … (overgrowth of bones in hands, feet, and face) in adults
growth hormone; acromegaly;
other important hormones produced by the anterior pituitary are not directly involved in the regulation of other endocrine glands of the body:
… stimulates milk production by the breasts. the role of the hormone in males is not well understood
prolactin (PRL)
the … hormones control production and secretion of the tropic hormones, GH, and PRL
ventral hypothalamic
the hypothalamic hormones reach the cells of the anterior pituitary through the …, a complex vascular arrangement of two capillary beds that are connected by the hypophyseal portal veins
hypophyseal portal system
the posterior pituitary is not an endocrine gland because it does not …
synthesize the hormones it releases
the posterior pituitary acts as a storage area for two neurohormones that are released in response to nerve impulses from neurons in the hypothalamus:
…: stimulates powerful uterine contractions during birth and also causes milk ejection in the lactating mother
…: causes the tubules of the kidneys to reabsorb more water from the urinary filtrate, reducing urine output and conserving body water
oxytocin; antidiuretic hormone
hyposecretion of ADH results in dehydration from excessive urine output, a condition called … Individuals with this condition experience an insatiable thirst. hypersecretion results in edema, headache, and disorientation
diabetes insipidus
the pineal gland is a small cone-shaped gland located in the roof of the third ventricle of the brain. its major endocrine product is …, which exhibits a diurnal cycle. it peaks at night, making us drowsy, and is lowest around noon
melatonin
The endocrine role of the pineal gland in humans is still controversial, but it is known to play a role in mating and migratory behavior of other animals. In humans, melatonin appears to exert some inhibitory effect on the reproductive system that prevents … Changing levels of melatonin may also affect biological rhythms associated with body temperature, sleep, and appetite.
precocious sexual maturation.
The thyroid gland is composed of two lobes joined by a central mass, or…. It is located in the throat, just inferior to the larynx. It produces two major hormones, …and ….
isthmus; thyroid hormone; calcitonin;
