Tag: muscle tissue

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'.

• Cardiac muscles have the property of both the striated muscles (or skeletal muscle) and unstriated muscle or smooth muscle.
• Cardiac muscle is involuntary, which is the property of smooth muscle.
• Cardiac muscles also have features of skeletal muscles. Like skeletal muscle, cardiac muscle cross striations formed by rotating segments of thick and thin protein filaments and the primary structural proteins of cardiac muscle are myosin and actin. 
• However, skeletal muscles are voluntary as they are supplied with the somatic nerve.

The muscles in the upper arm and shoulder are striated muscles. So, option B is incorrect.
Heart possesses unique muscles, called cardiac muscles, which are involuntary striated muscles. So, option C is incorrect.
The intestinal muscles are involuntary and are smooth muscle. So, option D is incorrect.

A syncytium is a multinucleated mass of cytoplasm, that is not separated into individual cells.
Example: Formation of skeletal muscle. Large skeletal muscle fibers formed by the fusion of thousands of individual muscle cells.
Cardiac muscle's syncytium is important because it allows rapid coordinated contraction of muscles along their entire length.
Smooth muscles, however, are not syncytial
So, the correct answer is 'Smooth muscle'

There are three types of muscle tissue such as cardiac, smooth or unstriated and skeletal or striated.
Cardiac muscle cells are located in the walls of the heart, appear striated and are under involuntary control.
Smooth or unstriated muscle fibers are located in the walls of hollow visceral organs, except the heart, appear spindle-shaped and are under involuntary control.
Skeletal or striated muscles fibers occur in muscles, which are attached to the skeleton. They are striated in appearance and are under voluntary control.
Thus, the correct answer is option D.