Tag: structure of protein

Epimysium is the outermost white fibrous connective tissue that completely surrounds and encases skeletal muscle. It is composed of dense irregular connective tissue. The most important biological purposes of this layer are protection from strain and friction. The smoothness of the tissues promotes seamless gliding, and also protect joints and other high-impact areas from rips or tears and promotes smooth movement of the limbs and joints.

The gluteus maximus (also known as glutus maximus or, collectively with the gluteus medius and minimus, the glutes) is the largest and most superficial of the three gluteal muscles. It makes up a large portion of the shape and appearance of the hips. It permits a variety of motion and allows us to sit upright.

myosin filament is a polymerised protein. Many monomeric proteins, called meromyosin constitute one thick filament. Each meromyosin has two important parts, a globular head with a short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM). The HMM component, i.e., the head and short arm projects outwards at regular distance and angle from each other from the surface of a polymerised myosin filament and are known as the cross arm. The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.

Muscles cannot expand. They can only contract. Hence, muscles responsible for body movements frequently occur in pairs called agonist-antagonist pairs, for example, biceps and triceps. The biceps cause movement towards the body or central axis and triceps cause movement away from the body or away from the central axis.

There are two types of muscles, voluntary and involuntary. Voluntary muscles are under our own control while involuntary muscles are not. The arrector pili muscles are small muscles attached to hair follicles in mammals. Contraction of these muscles causes the hairs to stand on end. Each arrector pili is composed of a bundle of smooth muscle fibres, which attach to several follicles (a follicular unit) and is innervated by the sympathetic branch of the autonomic nervous system. The contraction of the muscle is, therefore, involuntary stresses such as cold, fear etc., may stimulate the sympathetic nervous system and thus, cause contraction, but the muscle is not under conscious control.

Like all other mammals, camel also have 7 cervical vertebre. The only exceptions in mammals are the manatee and the 2-toed sloth, which have 6 cervical vertebrae and the 3-toed sloth having 9 cervical vertebrae.

Shivering is an involuntary action of striated muscles ( skeletal muscles). Shivering is also called as rigors or shuddering. It is a bodily function in response to early hypothermia or just feeling cold in warm-blooded animals. When the core body temperature drops, the shivering reflex is triggered to maintain homeostasis. Skeletal muscles around begin to shake in small movements, creating warmth by expending energy. 

Myosin is found in muscle filaments. The head portion of myosin forms cross linkage with actin filaments during muscular contraction. The cross bridges between actin and myosin are very important for muscular contraction activity. Thus, myosin fulfills both structural and functional roles.

Autorhythmicity is a property of electrically active cells, that show rhythmic activity without being driven by the rhythmic external stimulation, e.g., heart muscle cells or neurons.
Thus, the correct answer is option (C), 'Heart'.

The shape of the skeletal muscle is cylindrical, while that of visceral muscle is pear-shaped or spindle-shaped. Actin filaments which are thin filaments and myosin which are thick filaments are contractile proteins in the skeletal muscle as well as in the visceral muscle.
Thus, the correct answer is the option (D), 'Presence of actin and myosin filaments'.