EXAM 3 Flashcards by Deja Nell

Define Rigor Mortis

postmortem contraction of the skeletal muscles due to lack of new ATP synthesis

ATP is no longer being produced

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Name the proteins in the thin filaments of smooth muscle and their functions

Actin - contains binding sites for myosin heads
Tropomyosin - supports the structure of actin. Does not block the myosin binding sites on actin in a relaxed smooth muscle

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what is the function of tropomyosin in a relaxed skeletal muscle

wraps around the actin filament and covers myosin binding sites, so contraction cannot occur

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Name the structures PRESENT in SKELETAL muscle fibers that are ABSENT from SMOOTH muscle cells (4)

sarcomeres - cellular units of skeletal (and cardiac) muscle
troponin -“regulates actin-myosin interactions in skeletal and cardiac muscle contraction”
z-lines - protein that encloses the thin filament
t-tubules - involutions of sarcomere that action potentials flow through

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Compare and Contrast… single-unit smooth muscle and multiunit smooth muscle

Similarities

innervated with autonomic nerve fibers
stimulated to contract by chemicals

Differences

single unit:
- circular and longitudinal muscle sheets
- electrically coupled by gap junctions
- functional syncytium
- pacemaker activity
multiunit:
- individual smooth muscle fibers
- no gap junctions
- no pacemaker activity

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Define the neuromuscular junction

junction between the axon terminal of a motor neuron and a skeletal muscle fiber that is separated by a small space called the neuromuscular (synaptic) cleft

each muscle fiber has only ONE neuromuscular junction

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How will an increase in extracellular calcium affect the strength of a cardiac muscle

strength will increase; relies on extracellular calcium to release calcium from the SR

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in smooth muscle cells, the thin filaments are anchored by…

dense bodies

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Compare and Contrast… skeletal muscle and cardiac muscle

Similarities

Striations present
sarcomeres present
T-tubules present
Ca²⁺ binds to TnC
Grows through hypertrophy

Differences

Skeletal muscle: voluntary movement, no syncytium, no gap junctions
cardiac muscle: involuntary movement

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Define a Triad

the structure formed by a transverse (T) tubule in between two terminal cisternae

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define indirect attachment of the skeletal muscle

tendon extends from the muscle to attach to the bone

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Autonomic Nervous System divisions

Sympathetic Nervous System

Parasympathetic Nervous System

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Give the role of ATP in muscle contraction (3)

ATP is hydrolyzed by ATPase to produce ADP and Pi to activate the myosin heads
ATP is required for crossbridge detachment
ATP is required for the sequestration of calcium ions back into the SR for storage (active transport)

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Place the three skeletal muscle fibers in order of GLYCOCEN CONTENT (high to low)

FG > FO >SO

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What is the power stroke in excitation-contraction coupling in skeletal muscle?

ADP + Pi dissociate from myosin

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List the sources of ATP to support skeletal muscle contraction (4)

stored ATP - used first
Direct phosphorylation of ADP by creatine phosphate
- CP + ADP –> ATP + creatine
Aerobic catabolism of glucose - produces the most ATP, slowest
Anaerobic catabolism of glucose - fastest

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Which type of skeletal muscle fiber is fatigable and why?

Fast Glycolitic Fibers because they produce ATP from anaerobic respiration, which produces powerful, high-tension contractions, but fatigues quickly

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Define the motor end plate and its function

definition: Highly folded region of the sarcolemma
function: expresses acetylcholine receptors on surface

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How will the contraction of smooth muscle be affected if the autonomic innervation is severed?

Contraction of smooth muscle will occur due to pacemaker activity

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Place the three skeletal muscle fibers in order of MYOGLOBIN CONTENT (high to low)

SO > FO > FG

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Define the sliding filament mechanism

when contraction (shortening) occurs when thin filaments “slide” into the H zone (towards the M line) pulling the Z discs inward

length of sarcomere shortens, shortening the entire muscle

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How will an increase in extracellular calcium affect the strength of a smooth muscle?

strength will increase; relies on extracellular calcium to release calcium from the SR

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Define isometric contraction

force (tension) generated by the muscle is increasing at a constant muscle length; muscle does not shorten

FORCE < WEIGHT

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In SMOOTH muscle cells, myosin heads are activated when…

MLCK hydrolyzes Pi from ATP to activate myosin

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Discuss the role of calcium in **skeletal muscle** contraction

Ca2+ binds to TnC Troponin undergoes a conformational change that moves TnT and Tropomyosin from blocking the myosin binding sites on actin

what is the function of triads?

Triad releases Ca2+ ions into the sarcoplasm when the sarcolemma depolarizes

Characteristics of **Fast Glycolitic (FG) Fibers**

Fast ATPase; produces ATP **quickly** through **anaerobic** respiration

Which **skeletal muscle fiber** is also known as "red fibers" and why?

**Slow Oxidation Fibers** because they have the highest myoglobin content, which gives them a red pigment

In **SKELETAL muscle fibers** myosin heads are activated when...

ATP hydrolyzes to ADP + Pi

Describe the structural organization of a **sarcomere** (6)

* **A band:** thick filament * **M line****:** bisects and anchors A bands * **Thin filaments:** give the striated appearance of skeletal/cardiac muscle * **Z lines (Z discs)****:** anchor thin filaments * **H zone****:** middle region of A band * **I bands:** regions of thin filaments not overlapping with A band

What can inhibit the contraction of **cardiac muscle**?

Calcium Channel Blockers

Characteristics of **Fast Oxidative (FO) Fibers**

Fast ATPase; produces ATP **quickly** through **aerobic** respiration

What can inhibit a the contraction of a **skeletal muscle**?

chemicals that **block** **acetylcholine receptors**

Describe the **divisions** of the motor (efferent) nerves of the PNS

Somatic Nervous System Autonomic Nervous Sustem

Activation of the **sympathetic nervous system** causes...

bronchodilation and vasoconstriction

**Function** of dense bodies

anchor thin filaments

Place the three skeletal muscle fibers in order of recruitment (first to last)

SO \> FO \> FG

Discuss the role of calcium in **smooth muscle** contraction

Calcium binds to calmodulin --\> forms calcium-calmodulin complex --\> activated Myosin Light-Chain Kinase (MLCK)

What can inhibit the contraction of **skeletal muscles**?

Chemicals that block acetylcholine receptors

what is the consequence (result) of the **power stroke**?

Sliding of the thin filaments toward the H Zone and M line

Name the proteins in the thin filament of a **cardiac muscle** and their functions

* **Actin** - contains binding sites for myosin heads * **Tropomyosin** - regulatory protein that "wraps around the actin filament and covers myosin binding sites to prevent contraction in a relaxed skeletal muscle" * **Troponin** - three polypeptide complex (TnC, TnT, TnI) that regulates actin-myosin interactions in skeletal and cardiac muscle contraction

How will an increase in extracellular calcium affect the strength of the **skeletal muscle**?

**strength is unaffected** because skeletal muscle doesn't use extracellular calcium

Characteristics of **Slow Oxidative (SO) Fibers**

Slow ATPase; produces ATP **slowly** through **aerobic** respiration

Autonomic Nervous System **function**

takes information to the smooth muscles and cardiac muscles (soft organs)

Types of **skeletal muscle fibers** (3)

Slow Oxidative (SO) Fibers Fast Oxidative (FO) Fibers Fast Glycolytic (FG) Fibers

Define Muscle Fatigue

physiological inability of a stimulated skeletal muscle to contract due to an **ATP deficit** ATP is **still being produce****d** but not at the rate of demand

**function** of calmodulin

regulatory protein that calcium binds to

List the subunits of troponin (3) and their functions

TnC - binds calcium ions TnT - binds to tropomyosin TnI - inhibitory subunit that binds to actin

Describe the **function** of the motor (efferent) nerves of the PNS

To take information from CNS to the effector structures

Define **direct attachment** of the skeletal muscles

when the epimysium fuses **directly** to the periosteum of the bone

Name the structures **PRESENT in SMOOTH musle cells** that are **ABSENT from SKELETAL muscle fibers** (4)

* **dense bodies** * **intermediate filaments** * **caveolae** * **calmodulin**

Define a **motor unit**

motor neuron and all of the skeletal muscle fibers it innervates

**function** of intermediate filaments

resist tension

Somatic Nervous System **function**

Takes information to the skeletal muscles (hard organs)

**cross bridge detachment** occurs when...

phosphate is removed from the myosin heads by **phosphorylase enzymes** and **intracellular Ca2+ levels fall**

Define functional syncytium

The contraction of the muscle as a single unit

Place the three skeletal muscle fibers in order of FIBER DIAMETER (large to small)

FG \> FO \> SO

what are activated globular heads?

When ATPase hydrolyzes ATP into [ADP and Pi] and attach to the myosin globular heads... they become ACTIVATED (Activated Myosin globular heads attach to actin which is called CROSS BRIDGES)

Compare and Contrast... **smooth muscle** and **cardiac muscle**

Similarities: * gap junctions present * functional syncytium * involuntary muscle control Differences: * **Smooth muscle** grows through hyperplasia AND hypertrophy * **Cardiac muscle** grows through hypertrophy

caveolae

shallow cavities in the sarcolemma that contain extracellular fluid that is saturated with calcium

What can inhibit the contraction of **smooth muscle?**

Calcium Channel Blockers

Describe the structural organization of a skeletal muscle

* **epimysium:** outer protective layer * **perimysium:** surrounds fasicles * **fasicle:** group of muscle fibers * **endomysium:** surrounds single muscle fiber (cell)

How will the **contraction of cardiac muscle** be affected if the parasympathetic innervation is severed?

Contraction of cardiac muscle **will occur** because there is no parasympathetic inhibition of the cardiac muscle

**Structures of the sarcomere** that **shorten** when a skeletal muscle contracts

H zone and I bands

Factors that affect the strength of skeletal contraction

1. **Size of the motor unit** activated 2. **Number of motor units** activated 3. **Frequency of activation** of the skeletal muscle fibers by the motor neuron 4. **Length of the sarcomere** prior to contraction

**structures of the sarcomere** that **remain the same** when a skeletal muscle contracts

A bands and Thin filaments

the diffuse junctions form directly between...

varicosity of an autonomic fiber and a smooth muscle cell

Explain **recruitment** as it pertains to the strength generated by skeletal muscle contraction

smallest motor units are used first and larger units recruited after

Define **isotonic** contraction

[sliding filament mechanism] generates force by changing the length of the muscle FORCE \> WEIGHT (me lifting a 5 lb weight)

EXAM 3 Flashcards

(73 cards)