page 340-349 Flashcards
■ Contains a rich supply of blood vessels and nerves required for nerve
conduction.
Connective Tissue
xxx;Surrounds the entire muscle.
yyy; Surrounds muscle bundles (fascicles).
zzz; Surrounds each muscle fiber.
Epimysium: Surrounds the entire muscle.
■ Perimysium: Surrounds muscle bundles (fascicles).
■ Endomysium: Surrounds each muscle fiber.
One xxx neuron innervates several skeletal muscle fibers (axon is
highly yyy
■ When a motor neuron transmits an action potential, ALL of the fibers it
innervates contract zzz
One α-motor neuron innervates several skeletal muscle fibers (axon is
highly branched).
■ When a motor neuron transmits an action potential, ALL of the fibers it
innervates contract simultaneously.
All motor neurons are arranged in various positions within the xxxx
horn of the spinal cord
All motor neurons are arranged in various positions within the ventral
horn of the spinal cord
Fractionation:
Not necessary to activate all motor units in a muscle.
■
Size principle:
Motor units are recruited in order of size of motor unit.
With greater muscle force, larger motor units are recruited
When an action potential reaches the xxx, acetylcholine
is released from vesicles within the axon terminus and binds to zzz on the sarcolemma. This, in turn, increases the membrane
permeability of yyyy and depolarizes the muscle cell.
When an action potential reaches the neuromuscular junction, acetylcholine
is released from vesicles within the axon terminus and binds to postsynaptic
nicotinic receptors on the sarcolemma. This, in turn, increases the membrane
permeability of Na+ and K+ and depolarizes the muscle cell.
https://drive.google.com/open?id=0B8uJUY-tie8GdmxwOTFwSGFKSmc
https://drive.google.com/open?id=0B8uJUY-tie8GeG9uRjJpSzVmR2s
The action potential travels along thexxxx and through a system of
yyyy, which extend from the zzz surface of the muscle fiber to the
SR of two adjacent sarcomeres.
The action potential travels along the sarcolemma and through a system of
t-tubules, which extend from the outer surface of the muscle fiber to the
SR of two adjacent sarcomeres.
xxx released from the terminal cisternae of each SR bind to zzz,
which is attached to the yyy molecule of thin filaments. This
causes a conformational change in the shape of tropomyosin, allowing
the actin filament to interact with the myosin cross-bridge.
Ca2+ released from the terminal cisternae of each SR bind to troponin C,
which is attached to the tropomyosin molecule of thin filaments. This
causes a conformational change in the shape of tropomyosin, allowing
the actin filament to interact with the myosin cross-bridge.
An yyy molecule bound to myosin is hydrolyzed to ADP + Pi. When
the ADP + Pi is xxxx from myosin, the actin filament is pulled closer
toward the aaa of the sarcomere, shortening its length (power stroke)
An ATP molecule bound to myosin is hydrolyzed to ADP + Pi. When
the ADP + Pi is released from myosin, the actin filament is pulled closer
toward the center of the sarcomere, shortening its length (power stroke)
As long as x and y are available, this cycle continues, further contracting
the muscle. If more muscle force is needed, more motor units are
activated.
As long as Ca2+ and ATP are available, this cycle continues, further contracting
the muscle. If more muscle force is needed, more motor units are
activated.
During relaxation, Ca2+ is taken up by the xx, causing the release of yyy
from the myosin cross-bridges. zzzz returns to its normal configuration,
blocking this interaction.
During relaxation, Ca2+ is taken up by the SR, causing the release of actin
from the myosin cross-bridges. Tropomyosin returns to its normal configuration,
blocking this interaction.
Oxidative capacity of muscle fibers is related to
■ Number of capillaries
■ Myoglobin content
■ Number of mitochondria
https://drive.google.com/open?id=0B8uJUY-tie8GSzV1d0ZMeE9BNkU
https://drive.google.com/open?id=0B8uJUY-tie8GbTVHTlA3TnhjM2s
Extrafusal fibers
■ Make up the majority of skeletal muscle.
■ Innervated by α-motor neurons.
Intrafusal fibers
■ Located within the bulk of the muscle.
■ Encapsulated.
■ Innervated by γ-motor neurons.
■ Includes muscle spindle and Golgi tendon organs
Sensory Innervation
■ Encapsulated intrafusal nerve fibers.
■ Stretch receptors.
■ Fine-tunes muscle tone.
■ Run parallel with extrafusal muscle fibers.
https://drive.google.com/open?id=0B8uJUY-tie8GN2dRYUFVZjdJYTA
https://drive.google.com/open?id=0B8uJUY-tie8GTldwaEg0LVJ6OXM
Reflex arcs:
- Receptor
- Sensory (afferent) neuron
- Integration center (CNS)
- Interneuron
- Motor (efferent) neuron
- Effector
https://drive.google.com/open?id=0B8uJUY-tie8GZlBPMEw0UlR2TjQ
https://drive.google.com/open?id=0B8uJUY-tie8GOW9mdHFDeXliUG8
Histology
■ Cells have a similar contractile structure (myofilaments) and striated
(actin, myosin) appearance as skeletal muscle cells.
■ Fibers are firmly linked by desmosomes.
■ Nuclei are centrally located.
cardiac muscles
cardiac muscle
More mitochondria between myofibrils.
■ Richer in myoglobin.
■ Cells have many branches, which communicate to adjacent cardiac muscle
cells via gap junctions.
cardiacmuscl
Intercalated discs coordinate the action of cardiac muscle cells.
■ Cells do not undergo mitosis: Injury results in fibrosis with loss of function
at that site
cardiac muscle innerv
Mediated by its own intrinsic contractile activity.
■ There are no motor units.
The autonomic nervous system (both sympathetic and parasympathetic
fibers) controls the rate and strength of myocardial depolarization
cardiac muscle
Cardiac muscle
Ca2+ enters the myocytes via xxxx, which are regulated
by yyy protein kinases.
Ca2+ enters the myocytes via specific calcium channels, which are regulated
by cAMP protein kinases.
The influx of Ca2+ enables the release of more Ca2+ from the xxx, initiating
yy and eventual muscle contraction.
The influx of Ca2+ enables the release of more Ca2+ from the SR, initiating
troponin-C binding and eventual muscle contraction.
Relaxation occurs when Ca2+ exits the xxx through a regulated yyy + exchange system.
Relaxation occurs when Ca2+ exits the myocytes through a regulated
Ca2+-Na+ exchange system.
Commonly found in tubular organs such as blood vessels, the GI tract,
and the respiratory tract, but also in ciliary bodies of the eye and hair
follicles.
■ Cells are small in diameter but very long.
■ Nuclei are single and centrally located.
smooth muscle
smooth muscle
Myofibrils are not striated.
■ No t-tubules are present.
■ SR system is poorly developed
cardiac muscle
Innervation
■ Mediated by the autonomic nervous system (both sympathetic and
parasympathetic).
However, there is a considerable xxx from the nerve terminal
to the sarcolemma because the yyy terminate in the surrounding
connective tissue.
However, there is a considerable synaptic distance from the nerve terminal
to the sarcolemma because the autonomic axons terminate in the surrounding
connective tissue.
Because not all smooth muscle cells are directly innervated, they rely on
xxxx junctions to propagate the action potential.
smooth muscle
Because not all smooth muscle cells are directly innervated, they rely on
cell-cell gap junctions to propagate the action potential.
Single unit of cardiac muscle
Numerous gap junctions between adjacent cells. Fibers
contract spontaneously without nerve impulses. Examples: GI, uterus,
ureters, arterioles
Multi-unit of smooth muscle
Cells lack gap junctions. Fibers are directly innervated.
Ca2+ (from the SR or extracellular sources) enters the xxx
cytoplasm and binds to calmodulin.
■ Calmodulin activates yyyy, which transfers a Pi from
an ATP molecule to the myosin light-chain.
Ca2+ (from the SR or extracellular sources) enters the smooth muscle cell
cytoplasm and binds to calmodulin.
■ Calmodulin activates myosin light-chain kinase, which transfers a Pi from
an ATP molecule to the myosin light-chain.
The phosphorylation of xxx enables it to interact with yyy in the
same manner as skeletal and cardiac muscle
The phosphorylation of myosin enables it to interact with actin in the
same manner as skeletal and cardiac muscle
Relaxation occurs when xx is taken up by the SR or plasma membrane
and the myosin light-chain kinase becomes yyy.
■ Contraction is zzz. Each contraction cycle requires one
ATP.
Relaxation occurs when Ca2+ is taken up by the SR or plasma membrane
and the myosin light-chain kinase becomes inactivated.
■ Contraction is slow and prolonged. Each contraction cycle requires one
ATP.
https://drive.google.com/open?id=0B8uJUY-tie8GbDFOWU9hSjVKNjA
https://drive.google.com/open?id=0B8uJUY-tie8GMUlNcWdlMTEwLVk
Low Reynolds number
■ In straight vessels.
■ Layer closest to vessel surface does not move.
■ Layer in center moves at maximum velocity.
■ Laminar flow occurs up to a xxx
■ Turbulent flow occurs above yyy
■ Laminar flow occurs up to a certain critical velocity.
■ Turbulent flow occurs above critical velocity.
High Reynolds number
Occurs above critical velocity.
■ Reynolds number.
■ Represents probability for turbulent flow.
reynold number
Related to:
■ Velocity.
■ Diameter of vessel.
■ Blood viscosity.
Examples of turbulence:
■ Constricted, atherosclerotic vessel.
■ Ascending aorta.
■ Anemia.
Fastest to slowest:
■ Vena cavae.
■ Aorta.
■ Large veins.
■ Small arteries.
■ Arterioles.
■ Capillaries.
https://drive.google.com/open?id=0B8uJUY-tie8GSEQ3MGNWZUFRUGc
https://drive.google.com/open?id=0B8uJUY-tie8GN2dRYUFVZjdJYTA
https://drive.google.com/open?id=0B8uJUY-tie8GQUt4U0xBNUwxSGc
laplace law
Wall stress = Pr/t.
■ P = pressure.
■ r = radius.
■ t = wall thickness.
In vessels:
A thin-walled, distended vessel, under large amounts of pressure
has more wall tension/stress and is at greater risk for rupture.
In the heart:
A dilated, thin-walled myocardium, under increasing pressure
and volume has higher wall tension (and the myocardial oxygen
demand is elevated).
P within the ventricle depends on xxxx (eg, TPR, aortic stenosis).
■ r within the ventricle depends on yyy (amount of venous return).
■ t thickness of the ventricle: Increased zzz decreases wall stress to
P within the ventricle depends on afterload (eg, TPR, aortic stenosis).
■ r within the ventricle depends on preload (amount of venous return).
■ t thickness of the ventricle: Increased thickness decreases wall stress to a point
