1. Receptor 2. Sensory (afferent) neuron 3. Integration center (CNS) 4. Interneuron 5. Motor (efferent) neuron 6. Effector

page 340-349 Flashcards by Sumit Puri

■ Contains a rich supply of blood vessels and nerves required for nerve

conduction.

Connective Tissue

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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.

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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.

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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

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Fractionation:

Not necessary to activate all motor units in a muscle.

■

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Size principle:

Motor units are recruited in order of size of motor unit.

With greater muscle force, larger motor units are recruited

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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.

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https://drive.google.com/open?id=0B8uJUY-tie8GdmxwOTFwSGFKSmc

https://drive.google.com/open?id=0B8uJUY-tie8GeG9uRjJpSzVmR2s

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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.

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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.

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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)

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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.

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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.

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Oxidative capacity of muscle fibers is related to

■ Number of capillaries

■ Myoglobin content

■ Number of mitochondria

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https://drive.google.com/open?id=0B8uJUY-tie8GSzV1d0ZMeE9BNkU

https://drive.google.com/open?id=0B8uJUY-tie8GbTVHTlA3TnhjM2s

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Extrafusal fibers

■ Make up the majority of skeletal muscle.

■ Innervated by α-motor neurons.

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Intrafusal fibers

■ Located within the bulk of the muscle.

■ Encapsulated.

■ Innervated by γ-motor neurons.

■ Includes muscle spindle and Golgi tendon organs

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Sensory Innervation

■ Encapsulated intrafusal nerve fibers.

■ Stretch receptors.

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■ Fine-tunes muscle tone.

■ Run parallel with extrafusal muscle fibers.

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https://drive.google.com/open?id=0B8uJUY-tie8GTldwaEg0LVJ6OXM

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Reflex arcs:

Receptor
Sensory (afferent) neuron
Integration center (CNS)
Interneuron
Motor (efferent) neuron
Effector

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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.

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cardiac muscles

cardiac muscle

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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

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.

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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.

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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

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