BIO 360 - Exam 3 - Lecture 2_Smooth & Cardiac muscle.pdf Flashcards
Figure 11.5 Use it as a map. Don’t memorize it!
Aren’t all involuntary reflexes caused by autonomic NS?
No. There are several somatic (motor) reflexes in addition to many autonomic reflexes..Dr. S discussed this knee jerk reflex twice: “..in response to signals from motor neurons”, “the skeletal muscle contracts in response to motor neurons”. /In both cases, tho, Dr. S transitioned from this reflex to taking about the autonomic nervous system.
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What is a baroreflex?
In cardiovascular physiology, we discuss select autonomic reflexes. These include the baroreflex that enables you to maintain blood pressure by modulating factors like heart rate and -force.
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Sympathetic branch has 2 “gears”
Amygdala fear! >hypothalamus
Adrenal sympathetic pathway: Kidneys stimulate epinephrine and norepinephrine release.
Autonomic NS, adrenal sympathetic pathway in ALL vertebrate animals
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The Autonomic NS target ______.
Movement and posture depend upon use of ______ ______, which attach to bones by ______.
*contract in response to ______ ______ ______ signals.
______ ______ usually surround organs and tubes
*contract on their own, but regulated by autonomic nervous system,hormones, metabolic factors.
______ ______ has hybrid traits, some similar to skeletal muscle, other similar to smooth muscle
●contracts on its own, but regulated by autonomic nervous system.
DO NOT REQUIRE ______ FROM NEURONS TO CONTRACT
muscles / skeletal muscles / tendons / somatic motor system
Smooth muscle / Cardiac muscle / Signals
Since prehistoric times, one smooth muscle has received more attention than others.
Uterus
Smooth muscles…
(1) Flexible.
(2) Do not fatigue.
(3) Enhanced capacity for growth and healing.
Smooth muscle vs. skeletal muscle - Figure 12.1
Organization of contractile filaments and the nuclei?
Organization of the cells relative to each other?
How does smooth muscle DIFFER from skeletal muscle: 1
Smooth muscle
(1) has small, mono-nucleated cells that can divide all life
(2) is not striated:actin and myosin filaments dispersed ‘randomly’, and are not organized into sarcomeres
(3) Contracts and relaxes more slowly
(4) has poorly developed sarcoplasmic reticulum that is notthe source of Ca2+for contraction
(5) requires the influx of Ca2+from the extracellular fluid
(6) has no t-tubules, no troponin, and no troponin-Ca2+binding…
in other words, the excitation-contraction coupling is different
How does smooth muscle DIFFER from skeletal muscle: 2
Smooth muscle
(1) does not need somatic motor neurons to contract
(2) is typically myogenic (self-excitable)
(3) rate and/or strength of contractions is influenced by autonomic NS
(4) neurotransmitter receptors are spread along the muscle cell membrane and transmitters diffuse there from the autonomic neurons
(5) Some smooth muscles have fibers (cells) connected to each other by gap junctions so the muscle’s contraction is coordinated between the cells.
Autonomic nerves have ______ along axons: bulges where ______ is stored and released.
Single vs. multi-unit smooth muscle = different innervation by autonomic NS
Single unit smooth muscle cells are connected by ______ ______, and the cell contracts as a single unit.
varicosities / neurotransmitter / gap junctions
Single vs. multi-unit smooth muscle = different innervation by autonomic NS
Multi-unit smooth muscle cells are not ______ ______, each cell must be stimulated ______.
electrically linked / independently
One smooth muscle in the female body is usually a multi-unit smooth muscle, but will change to a single-unit smooth muscle under the influence of hormones produced during the late stages of pregnancy. Which muscle?
What is the adaptive significance of this change?
How can the muscle tissue change from multi-unit to single-unit?
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Figure 12.1 - Cardiac muscle has some ‘hybrid’ characters, but also unique features.
How is cardiac muscle similar and different to skeletal or smooth muscle?
*See the summaries in Fig. 12.1 and Table 12.4
Cardiac muscle
(1) contracts without any outside(NS) signal, like many smooth muscles
(2) contraction does not depend upon somatic motor neurons
(3) rate and graded force of contraction is regulated by the autonomic NS
(4) cells are striated: myofibrils have actin and myosin filaments organized in sarcomeres, like skeletal muscle
(5) excitation-contraction coupling is similar to skeletal muscle
(6) action potentials in t-tubules stimulates Ca2+influx and release of Ca2+from sarcoplasmic reticulum
(7) Ca2+binds to troponin, cross bridge formation etc.
Organization of the cardiac cells: 2 major types
99% are contractile cardiac muscle fibers(contractile myocardium):
* respond to depolarization by contracting (but depolarization signal is NOT from AP in neurons!)
* do mechanical pumping activity of heart
1% are autorhythmic cells organized into network
* conducting system of the heart (autorhythmic myocardium)
* initiate and propagate action potentials that trigger contraction of contractile cells: i.e. they make the contractile cardiac cells depolarize
* do not contract, just set the pace,so NO manual labor
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Heart’s 1% autorhythmic cells (conduction system)
Heart’s 99% contractile cardiac muscle cells (working muscle)
