Structure Block 4 flag concepts

Which area of the sarcomere remains constant in length during an isotonic muscle contraction?

A band

In the 'Walk Along Theory' of muscle contraction, what event is directly responsible for the detachment of the myosin cross-bridge from the actin filament?

Binding of a new ATP molecule to the myosin head.

What characterizes the 'rigor state' in the cross-bridge cycle?

Myosin is tightly bound to actin without any bound nucleotide.

In terms of cellular organization, how is the 'pull' generated by the myofibrils transmitted to the bone?

Via the T-tubules which act as physical struts connecting the sarcoplasm to the epimysium.

In the context of sarcomere zones, what is found in the I-band?

only thing filaments

What is the term for a localized and transient increase in Ca2+concentration in cardiac muscle that occurs just before a full calcium signal is created?

Calcium spark

True or False: Smooth muscle fibers contain a sarcoplasmic reticulum that is just as extensive and well-developed as that of skeletal muscle.

False, only slightly developed

The process of 'calcium-induced calcium release' in cardiac muscle involves Ca2+ entry through which specific structure?

T tubules

Smooth muscle structure

Smooth muscle cells are small and spindle-shaped, and they lack the epimysium and perimysium found in skeletal muscle.

What happens to the myosin-actin relationship in smooth muscle after the phosphate is split from the regulatory light chain?

The removal of the phosphate group by myosin phosphatase inactivates the myosin, causing the contraction to end.

True or False: In smooth muscle, the concentration of extracellular calcium has a direct effect on the strength of contraction.

True: Because the SR is poorly developed in smooth muscle, the influx of calcium from the ECF is the primary determinant of contraction.

In cardiac muscle, what is the ultimate fate of the 'calcium signal' formed by summed calcium sparks?

Just like in skeletal muscle, the final calcium signal in cardiac muscle binds to troponin to initiate contraction.

Which muscle type is characterized by being branching, striated, and usually having a single nucleus?

Cardiac

Which band of the sarcomere contains only thick filaments and disappears or narrows significantly during maximal contraction?

H zone: This area is the central part of the A band where no thin filaments overlap the thick filaments in a relaxed state.

What happens to the myosin head in the 'low energy state'?

It has just completed the power stroke and released ADP

In skeletal muscle, which protein molecule is composed of two intertwined helices forming a tail and two globular heads?

Myosin

Which statement accurately describes the differences in mitochondria between muscle fiber types?

Slow-contracting fibers contain more mitochondria to support sustained energy needs

Which specific layer of the epidermis is characterized by the presence of desmosomes providing significant mechanical strength to the tissue?

Stratum spinosum

What skin layer is thick and vascularized?

Dermis; The dermis contains the blood vessels and capillary networks necessary to nourish the skin and regulate temperature.

What glands regulate the ionic composition of plasma?

This is a function associated with eccrine sweat glands, which can reabsorb sodium and chloride.

What is the primary function of sebaceous glands in the integumentary system?

Lubrication and waterproofing of the skin and hair

Which structure in the claw is directly fused with the periosteum of the distal phalanx?

The dermis covering the unguicular process of the bone is fused with the periosteum, providing a strong anchor for the claw.

Birds lack sebaceous glands, but what gland do they have?

they often have a specialized uropygial (preen) gland, though it is not associated with individual feathers.

Layers of epidermis

Corneum, granulosum, spinosum, basale

What allows for the 'functional syncytium' of cardiac muscle?

Intercalated disks with gap junctions and desmosomes