In the histology of skeletal muscle, a triad is the structure formed by a T tubule with a sarcoplasmic reticulum (SR) known as the terminal cisterna on either side. Each skeletal muscle fiber has many thousands of triads, visible in muscle fibers that have been sectioned longitudinally.

triad is an essential skeletal muscle substructure. It represents the close apposition of the transverse tubule (T- tubule) membrane with 2 flanking terminal cisternae of the sarcoplasmic reticulum (SR) (Fig. 1A). The primary role of the triad is to coordinate excitation-contraction coupling (EC coupling).

Complete answer: The triad system is the characteristic of muscle cells. It is a part of the skeletal muscle. The skeletal muscle consists of thousands of triads. It is visible when the longitudinal section of muscle fibre is taken. The muscle cells consist of many transverse tubules present on the sarcolemma.

In skeletal muscle, T-tubules tightly associate with the sarcoplasmic reticulum (SR), in a region called terminal cisternae/junctional SR. The close association of one T-tubule with two terminal cisternae on both sides of the tubule forms the triad (Figure 1). Triad organization in skeletal muscle.

The main function of the triads is to translate the action potential from the plasma membrane to the sarcoplasmic reticulum, effecting calcium flow into the cytoplasm and the initiation of muscle contraction.

So, Correct answer is ‘Stimuli Neurotransmitter secretion →→ Excitation of T-system →→ Release of Ca2+ →→ Cross-bridges formation →→ Sliding of actin filaments →→ H band diminishes’

The process of muscular contraction occurs over a number of key steps, including:

• Depolarisation and calcium ion release.
• Actin and myosin cross-bridge formation.
• Sliding mechanism of actin and myosin filaments.
• Sarcomere shortening (muscle contraction)

Terms in this set (5)

• exposure of active sites – Ca2+ binds to troponin receptors.
• Formation of cross-bridges – myosin interacts with actin.
• pivoting of myosin heads.
• detachment of cross-bridges.
• reactivation of myosin.

Terms in this set (9)

• Electrical current goes through neuron releasing ACH.
• ACH released into synapse.
• Electric current spreads to sarcolema.
• Current goes down to T tubules.
• Action potential travels to sarcoplasmic reticulum releasing calcium.
• Calcium binds to troponin, changing shape of tropomysium.
• Myosin binds with actin.

Terms in this set (14)

• Action potential arrives at axon terminal.
• Trigger voltage gated calcium channels.
• Calcium causes ACh to be released by exocytosis.
• ACh diffuses across junction.
• Influx of sodium to sarcolema.
• Action potential travels down sarcolema and into t-tubule.
• Calcium is released from sarcoplasmic reticulum.

The first step in the process of contraction is for Ca++ to bind to troponin so that tropomyosin can slide away from the binding sites on the actin strands. This allows the myosin heads to bind to these exposed binding sites and form cross-bridges.

Terms in this set (11)

1. brain sends signal.
2. acetylcholine is released from the synaptic vesicles.
3. acetylcholine travels across the synaptic cleft and binds to receptor molecules.
4. sodium ions diffuse into the muscle cell.
5. calcium ions are released from the SR.
6. calcium ions bind to actin and expose binding sites for myosin.

Sliding filament theory (muscle contraction) 6 steps D:

• Step 1: Calcium ions. Calcium ions are released by the sarcoplasmic reticulum in the actin filament.
• Step 2: cross bridge forms.
• Step 3: Myosin head slides.
• Step 4: skeletal muscle contraction has occurred.
• Step 5: Cross bridge breaks.
• Step 6: troponin.

Terms in this set (8)

• an action potential travels along a neuron to a synapse at a muscle fiber.
• acetylcholine (neurotransmitter) is released from a neuron.
• acetylcholine (neurotransmitter) binds to muscle cell membrane.
• sodium ions diffuse into the muscle fiber starting an action potential.

12 Steps

The movements and motions that joints and their muscles are capable of include:

• Abduction.
• Adduction.
• Flexion.
• Hyperflexion.
• Extension.
• Hyperextension.
• Rotation.
• Internal rotation.

Terms in this set (6)

• Rule #1. Muscles have two+ attachments and must cross at least one joint.
• Rule #2. Muscles “pull” and get shorter.
• Rule #3. attachment that moves is the insertion.
• Rule #4. Muscles that decrease angle between ventral surfaces are flexors.
• Rule #5. Muscles work in opposing pairs.
• Rule #6.

How do you do progressive muscle relaxation?

• Breathe in, and tense the first muscle group (hard but not to the point of pain or cramping) for 4 to 10 seconds.
• Breathe out, and suddenly and completely relax the muscle group (do not relax it gradually).
• Relax for 10 to 20 seconds before you work on the next muscle group.

The sequence of events in twitch skeletal muscle involves: (1) initiation and propagation of an action potential along the plasma membrane, (2) spread of the potential throughout the transverse tubule system (T-tubule system), (3) dihydropyridine receptors (DHPR)-mediated detection of changes in membrane potential, (4) …

In order for it to release that handhold and pull again, ATP must provide energy for the release motion. Thus, ATP is consumed at a high rate by contracting muscles.

ATP is required for muscle contraction. Four sources of this substance are available to muscle fibers: free ATP, phosphocreatine, glycolysis and cellular respiration. A small amount of free ATP is available in the muscle for immediate use.

Muscle contraction does not occur without sufficient amounts of ATP. The amount of ATP stored in muscle is very low, only sufficient to power a few seconds worth of contractions. As it is broken down, ATP must therefore be regenerated and replaced quickly to allow for sustained contraction.

What two things is the energy released during muscle contraction needed for? 1) The movement of the myosin heads. 2) The reabsorption of calcium ions into the sarcoplasmic reticulum by active transport.

Muscle contraction happens only when the energy molecule called adenosine triphosphate (ATP) is present. ATP provides the energy for muscle contraction and other reactions in the body.

Muscle contraction begins when the nervous system generates a signal. The signal, an impulse called an action potential, travels through a type of nerve cell called a motor neuron. The neuromuscular junction is the name of the place where the motor neuron reaches a muscle cell.

During exercise epinephrine (adrenaline) and norepinephrine (noradrenaline) are released from the adrenal medulla into the blood. They transport energy to muscles and enhance the activity of the heart and other organs promoting muscle contraction.

Each sarcomere is composed of two main protein filaments—actin and myosin—which are the active structures responsible for muscular contraction.

calcium ions

Calcium triggers contraction in striated muscle. (A) Actomyosin in striated muscle. (1) Striated muscle in the relaxed state has tropomyosin covering myosin-binding sites on actin. (2) Calcium binds to troponin C, which induces a conformational change in the troponin complex.