Locomotive And Movement (17.1 - 17.2.2)

What are the three main types of movements exhibited by the cells of the human body?

The three main types of movements are:

1. Amoeboid movement.

2. Ciliary movement.

3. Muscular movement.

What is amoeboid movement, and where is it seen in the human body?

Amoeboid movement is seen in specialized cells like macrophages and leucocytes in blood. It is effected by pseudopodia formed by the streaming of protoplasm (as in Amoeba).

Which cytoskeletal elements are involved in amoeboid movement?

Cytoskeletal elements like microfilaments are involved in amoeboid movement.

Where does ciliary movement occur in the human body?

Ciliary movement occurs in internal tubular organs lined by ciliated epithelium, such as the trachea and the female reproductive tract.

What is the role of ciliary movement in the trachea and the female reproductive tract?

In the trachea, ciliary movement helps remove dust and foreign substances. In the female reproductive tract, it facilitates the passage of ova.

What is the role of muscular movement in the human body?

Muscular movement enables movement of limbs, jaws, tongue, etc., and is essential for locomotion and other activities.

What are the special properties of muscle tissue?

Muscle tissue has four special properties:

1. Excitability.

2. Contractility.

3. Extensibility.

4. Elasticity.

How are muscles classified based on their location?

Muscles are classified into:

1. Skeletal muscles.

2. Visceral muscles.

3. Cardiac muscles.

What are skeletal muscles, and how do they function?

Skeletal muscles are associated with skeletal components. They appear striped (striated) under a microscope and are under voluntary control. They are involved in locomotion and changes in body posture.

What are visceral muscles, and where are they located?

Visceral muscles are located in the walls of hollow organs like the alimentary canal and reproductive tract. They are smooth (non-striated) in appearance and involuntary in function.

How do visceral muscles assist in the human body?

Visceral muscles assist in the transportation of food through the digestive tract and the movement of gametes through the genital tract.

What are cardiac muscles, and how are they structured?

Cardiac muscles are the muscles of the heart. They are striated and involuntary in function, forming a branching pattern when cardiac muscle cells assemble.

What is the function of the sarcoplasmic reticulum in skeletal muscles?

The sarcoplasmic reticulum in skeletal muscles serves as the storehouse for calcium ions, which are essential for muscle contraction.

What are the two proteins responsible for the striated appearance of skeletal muscles?

The two proteins responsible are Actin (in I-bands) and Myosin (in A-bands).

What is the structure of an actin filament?

Each actin filament consists of two helically wound F-actins, which are polymers of G-actins. Tropomyosin runs close to the F-actins, and Troponin is distributed at regular intervals along the tropomyosin.

What is the function of troponin in actin filaments?

Troponin masks the active binding sites for myosin on actin filaments in the resting state.

What are the two main parts of a myosin filament?

A myosin filament consists of:

1. A globular head with a short arm (heavy meromyosin, HMM).

2. A tail (light meromyosin, LMM).

What is the function of the myosin globular head?

The myosin globular head acts as an active ATPase enzyme and has binding sites for ATP and actin.

What is the sliding filament theory of muscle contraction?

The sliding filament theory states that contraction occurs when thin filaments (actin) slide over thick filaments (myosin), shortening the sarcomere.

What initiates muscle contraction?

Muscle contraction is initiated by a signal from the CNS via a motor neuron. The motor neuron and muscle fibers it controls form a motor unit.

What happens at the neuromuscular junction during muscle contraction?

At the neuromuscular junction, a motor neuron releases acetylcholine, which generates an action potential in the sarcolemma. This causes the release of calcium ions into the sarcoplasm.

How do calcium ions trigger muscle contraction?

Calcium ions bind to troponin, unmasking active sites on actin for myosin binding. This allows cross bridges to form, pulling actin filaments toward the center of the A-band.

What happens during muscle relaxation?

During relaxation, calcium ions are pumped back into the sarcoplasmic reticulum, active sites on actin are masked again, and cross bridges break, returning the muscle to its relaxed state.