Q: Identify the correct statements.1. A-bands are dark and contain myosin.2. I-bands are light and contain actin.3. During the action, A band contracts.4. The part between two Z-lines is sarcomere.5. The central part of thin filament, not overlapped by thick filament is the H-zone.

The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils. The light bands contain actin(thin filament) and are called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin(thick filament). In the centre of each ‘I’ band is an elastic fibre called ‘Z’ line which bisects it. The thin filaments are firmly attached to the ‘Z’ line. The portion of the myofibril between two successive ‘Z’ lines is considered as the functional unit of contraction and is called a sarcomere Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge. This pulls the attached actin filaments towards the centre of ‘A’ band.The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction. Hence the ‘I’ bands get reduced, whereas the ‘A’ bands retain the length. The central part of thick filament, not overlapped by thick filament is the H-zone.So, the correct answer is '1,2 and 4

Question 1

Identify the correct statements.1. A-bands are dark and contain myosin.2. I-bands are light and contain actin.3. During the action, A band contracts.4. The part between two Z-lines is sarcomere.5. The central part of thin filament, not overlapped by thick filament is the H-zone.

Accepted Answer

The &#8216;A&#8217; and &#8216;I&#8217; bands are arranged alternately throughout the length of the myofibrils. The light bands contain actin(thin filament) and are called I-band or Isotropic band, whereas the dark band called &#8216;A&#8217; or Anisotropic band contains myosin(thick filament). In the centre of each &#8216;I&#8217; band is an elastic fibre called &#8216;Z&#8217; line which bisects it. The thin filaments are firmly attached to the &#8216;Z&#8217; line. The portion of the myofibril between two successive &#8216;Z&#8217; lines is considered as the functional unit of contraction and is called a sarcomere Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge. This pulls the attached actin filaments towards the centre of &#8216;A&#8217; band.The &#8216;Z&#8217; line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction. Hence the &#8216;I&#8217; bands get reduced, whereas the &#8216;A&#8217; bands retain the length. The central part of thick filament, not overlapped by thick filament is the H-zone.So, the correct answer is '1,2 and 4

Question 2

H-zone in skeletal muscle fibre is due to

Accepted Answer

Myofibril is made up of two types of filaments. They are thin filament(actin) and thick filament(myosin).The light bands contain actin and are called I-band or Isotropic band, whereas the dark band called &#8216;A&#8217; or Anisotropic band contains myosin. The &#8216;A&#8217; and &#8216;I&#8217; bands are arranged alternately throughout the length of the myofibrils. In a resting state, the edges of thin filaments on either side of the thick filaments partially overlap the free ends of the thick filaments leaving the central part of the thick filaments. This central part of thick filament, not overlapped by thin filaments is called the &#8216;H&#8217; zone.Hence H-zone in skeletal muscle fibre is due to Central gap between actin filaments extending through myosin filaments in A-band.So, the correct answer is 'Central gap between actin filaments extending through myosin filaments in A-band'.

Question 3

Boojho fell off a tree and hurt his ankle. On examination the doctor confirmed that the ankle was fractured. How was it detected?

Accepted Answer

Doctor used X-ray technique to detect the injuries of Boojho. X-ray machines are used to examine the desired internal structure of body.

Question 4

Name the type of joint between the following.(a) Atlas/axis(b) Carpal/metacarpal of thumb(c) Between phalanges(d) Femur/acetabulum(e) Between cranial bones(f) Between pubic bones in the pelvic girdle

Accepted Answer

Atlas/axis: Pivotal jointPivot joint, also called as rotary joint, or trochoid joint, in vertebrate anatomy, a joint that allows only rotary movement. It is exemplified by the joint between the atlas and the axis (first and second cervical vertebrae), directly under the skull, which allows for turning of the head from side to side.Carpal/metacarpal of thumb: Saddle jointA saddle joint is a synovial joint where one of the bones forming the joint is shaped like a saddle with the other bone resting on it like a rider on a horse. Saddle joints provide stability to the bones while providing more flexibility than a hinge or gliding joint.Between phalanges: Hinge jointA hinge joint is a common class of synovial joint that includes the ankle, elbow, and knee joints. Hinge joints are formed between two or more bones where the bones can only move along one axis to flex or extend.Femur/acetabulum: Ball and socket jointBall and socket joint is a natural or manufactured joint or coupling, such as the hip joint, in which a partially spherical end lies in a socket, allowing multidirectional movement and rotation.Between cranial bones: Fibrous jointFibrous joints are joints that have no joint cavity and are connected via fibrous connective tissue. The skull bones are connected by fibrous joints. Between pubic bones in the pelvic girdle: Ball and socket jointBall and socket joint is a natural or manufactured joint or coupling, such as the hip joint, in which a partially spherical end lies in a socket, allowing multidirectional movement and rotation.

Question 5

Differentiate between skeletal and smooth muscles.

Accepted Answer

Skeletal Muscles Smooth Muscles They are attached to the bones.They line up the visceral organs viz. Intestines, blood vessels, pupils, etc.They perform voluntary actions.They are responsible for involuntary reflexes and actions.They are well striated.They lack striation. Innervated by Peripheral Nervous System i.e. PNS.Innervated by Sympathetic and parasympathetic nervous systems.Help perform movements i.e walking, running, jumping, writing, etc. Responsible for vital body functions i.e. breathing, digestion, urine formation, etc.Calcium is the most vital substance in the process of skeletal muscle contraction. Neurotransmitters Acetylcholine or Norepinephrine play important role in smooth muscle contraction.Types of Skeletal Muscles are Red and White.Types of Smooth Muscles are Single-unit, Multi-unit, eg. Ciliary muscles.They contain actin and myosin filaments. The ratio of actin & myosin is 2:1. They also contain actin and myosin filaments, The ratio of actin and myosin is 10:1. Troponin is present in skeletal muscles that are Ca-binding proteins responsible for muscle contraction. Calmodulin is present in smooth muscles that are Ca-binding proteins responsible for muscle contraction.

Question 6

Differentiate between voluntary and involuntary muscles. Give one example of each type.

Accepted Answer

Voluntary muscles Involuntary muscles 1. They are controlled by CNS They function under ANS2.  The muscle cells are cylindrical and multinucleate The muscle cells are spindle shaped and uninucleate3  Cells are striated Cells are non-striated 4 Example: Skeletal muscles Example: muscles of the alimentary canal

Question 7

The type of joint between the human skull bones is called:

Accepted Answer

The type of joint between the human skull bones is called 'fibrous joint'. So, the correct answer is (c).

Question 8

The ability to move from one place to another is called

Accepted Answer

Locomotion is when the movement of a part of the body leads to a change in the position and location of the organism. The act of changing place or position by the entire body or by one or more of its parts is called movement.In multicellular animals, these movements include walking, running, jumping, crawling, climbing, swimming, flying, galloping, slithering, and so on. Hence, the ability to move from one place to another is called locomotion.So, the correct answer is 'Locomotion'.

Question 9

Write the difference between Pectoral and Pelvic girdle.

Accepted Answer

Pectoral girdle Pelvic girdle1. The pectoral girdle is situated in the pectoral region of the body and joins the upper limb to the body. The pelvic girdle is situated in the pelvic region of the body and joins the lower limb to the body. 2. It is composed of two bones namely clavicle or collar bone and scapula. It is composed of three bones, upper ileum, inner pubic and ischium. 3. It has no articulation with the vertebral column  It has an articulation with the vertebral column. 4. These perform functions like holding, lifting etc. These perform functions like running, standing, jumping etc.

Question 10

Draw a labelled diagram of various types of muscles found in the human body.

Accepted Answer

There are three types of muscles are-a. Striated muscleb. Smooth musclec. Cardiac muscle