BIOLOGY 2 Marks Questions

Actin and Myosin:

Actin	Myosin
Actin is a thin contractile protein.	Myosin is a thick contractile protein.
The light bands called I-band or Isotropic band contain actin.	The dark band called ‘A’ or Anisotropic band contains myosin.

The components of pelvic girdle are ilium, is chium and pubis. It articulates with, femur through acetabulum. The components of pectoral girdle are scapula and clavicle. It is the glenoid cavity of pectoral girdle in which head of humerus articulates.

1. The types of ribs in a human body:

• True ribs.
• Vertebro-chondral ribs.
• Floating ribs.

2. There are 12 pairs of ribs in a human being.

Myasthenia gravis: Auto-immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

2. Rahul has gained weight due to increased muscle and less of fat.

Explanation:
Rahul has gained weight because with regular exercise, myofibrils increase in thickness and protein synthesis also increases resulting in increase in volume of muscles. Thus, muscles become denser. With regular exercise the body fat burns.

Locomotion is performed:

1. In search of food.
2. To move to suitable breeding grounds.
3. To move to favourable climatic conditions.
4. in search of a mate.

The bones in the leg are as follows:

Thigh	-	Femur (1)
Knee cap	-	Patella (1)
Shank	-	Tibia (1)
	-	Fibula (1)
Ankle	-	Tarsals (7)
Foot	-	Metatarsals (5)
Toes	-	Phalanges (14)

S.No.	Fibrous Joints	Cartilaginous Joints
(i)	These joints do not allow any movement.	These joints allow limited movements.
(ii)	The bones are joined end-to-end with dense fibrous connective tissue.	The bones are joined together with the help of cartilages.
(iii)	e.g. skull bones.	e.g. between succesessive vertebrae.

1. Skeletal muscles show striations, i.e. alternate dark and light bands; hence, called striated musecls.
2. Since their movements are under the voluntary control of nervous system, they are called voluntary muscles.

In cartilaginous joints, white fibro cartilage present between the ends of bones and in synovial joints, synovial fluid present’ between articulating surface of two bones enclosed within synovial cavity make our joints to function without grinding noise and pain.

The three types of joints are:

1. Fibrous joints.
2. Cartilaginous joints.
3. Synovial joints.

Synovial joints play a major role in locomotion.

A forelimb contains the following bones:

Upper arm	-	Humerus (1)
Forearm	-	Radius (1)
	-	Ulna (1)
Wrist	-	Carpals (8)
Palm	-	Metacarpals (5)
Fingers	-	Phalanges (14)

Muscular movement is the type of movement found in majority of multicellular organisms. This occurs with the help of muscles. These are brought about by movement of myofilaments present within the muscle fibres.

Differences between non-muscular and muscular movements:

S. No.	Non-muscular Movement	Muscular Movement
1.	These movements include pseudopodial and ciliary movements.	These movements are brought about by movement of myofilaments within muscle firbres.
2.	They persist in the animals in some of their cells.	These are found in majority of animals.

1. Pivot joint.
2. Saddle joint.
3. Cartilaginous joint.
4. Ball and socket joint.

1. It protects the spinal cord.
2. It supports the head.
3. It serves as the point of attachment for the ribs.
4. It also provides place for attachment of muscles of the back.

There are five different types of synovial joints:

1. Ball and socket joint e.g., between humerus and pectoral girdle, between femur and pelvic girdle.
2. Hinge joint e.g., knee joint and elbow joint.
3. Pivot joint e.g., between atlas and axis.
4. Gliding joints e.g., between the carpals, between the tarsals.
5. Saddle joint e.g., between carpal and metacarpal of thumb.

The skull is composed of two sets of bones-cranial and facial, that totals to 22 bones. Cranial bones are 8 in number. They form the hard protective outer covering, cranium for the brain. The facial region is made up of 14 skeletal elements which form the front part of the skull. A single U-shaped bone called hyoid is present at the base of the buccal cavity and it is also included in the skull. Each middle ear contains three tiny bones-Malleus, Incus and Stapes, collectively called Ear Ossicles. The skull region articulates with the superior region of the vertebral column with the help of two occipital condyles (dicondylic skull).

S.No.	Skeletal Muscles	Cardiac Muscles
(i)	They are found attached to bones (skeletal elements).	They are found only in the heart.
(ii)	They are under the direct voluntary control of nervous system.	Nervous system does not directly control their activity.
(iii)	Striations are prominent.	Striations are faint.
(iv)	Intercalated discs are absent.	Intercalated discs are present.

1. Mandible and ear ossicles are the movable joints.
2. There are 33 vertebrae in vertebral column.
3. Atlas vertebra is also called 'yes' bone as it provides up and down movement to the skull.

1. The coordinated movements of cilia in our trachea help us in removing the dust or other particles inhaled with the air, towards the larynx.
2. The movements of cilia of the epithelial cells lining the fallopian tube facilitate the movement of ova towards the uterus.

1. A four wheeler has four articulation points for the four wheels.

Explanation:
The word 'spineless' is often used in the literal sense also. A person with no self respect and no self-confidence can be termed as spineless. It is said that such person can go to any low to fulfill his selfish goals. Such people are usually dishonest and lack the initiative. They are afraid of taking responsibilities. We should develop strong ‘spine' so that we can live with our head held high.

1. Vertebrochondral ribs; there are three pairs of them.
2. Since they are not attached ventrally to the sternum, they are called floating ribs.

1. Patella.
2. Clavicle ISTO.
3. Cranium.
4. Vertebral column.
5. Scapula.
6. Innominate.

A bone is a hard connective tissue, while cartilage is soft connective tissue. Bones form the skeletal structure of the body, whereas cartilage is present in nose, ear, ribs, larynx, and joints and also act as a shock absorber in these joints.

1. Locomotion refers to the voluntary movements which result in a change of place or location.
2. Walking, swimming, flying, climbing, running.

Eight bones form the facial part of skull. They are as follows:

1. Lacrimal bone (1),
2. Nasal bones (2),
3. Zygomatic bones (2),
4. Maxilla (2),
5. Mandible (1).

Bones and cartilages constitute our skeletal system. The skeletal system is divisible into axial and appendicular. Skull, vertebral column, ribs and sternum constitute the axial skeleton. Limb bones and girdles form the appendicular skeleton. Three types of joints are formed between bones or between bone and cartilage - fibrous, cartilaginous and synovial. Synovial joints allow considerable movements and therefore, play a significant role in locomotion.

Calcitonin and parathyroid hormones affect the level of calcium ion in blood. When plasma level of calcium rises beyond a certain point, it is controlled by calcitonin. When plasma level of calcium falls below a certain point, it is controlled by parathryroid hormone.

3. Helmets are very important because they help in saving the most important organ; the brain.

Explanation:
I can raise awareness about wearing helmet by following methods:
I will carry out poster campaigns, highlighting the dangers of not wearing a helmet. I will take help from doctors and police authorities to educate people; about benefits of wearing helmet. I will request my teachers to arrange for a guest lecture by eminent neurophysician to educate students about the issue.

S.No.	Fibrous Joints	Cartilaginous Joints
(i)	These joints do not allow any movement.	These joints allow limited movements.
(ii)	The bones are joined end-to-end with dense fibrous connective tissue. e.g. skull bones.	The bones are joined together with the help of cartilages. e.g. between successive vertebrae.

S.No.	Synovial Joints	Cartilaginous Joints
(i)	These are freely movable joints.	These joints permit only limited movement.
(ii)	There is a cavity filled with synovial fluid which reduces friction. e.g. Ball and socket joint, knee joint, etc.	They are joined by cartilages and there is no synovial fluid between articulating bones, e.g. joint between successive vertebrae.

S.No.	Cardiac Muscles	Visceral Muscles
(i)	They are found only in the the wall of the heart.	They are found in wall of visceral organs like alimentary canal, uterus, ureters, etc.
(ii)	Striations are faintly seen.	Striations are absent.
(iii)	Cells are cylindricall and branched.	Cells are spindle shaped.
(iv)	Intercalated discs are present.	Intercalated discs are absent.

1. Due to lack of oxygen, anaerobic respiration starts in the muscle. This leads to accumulation of lactic acid in the muscle which results in muscle cramp.
2. One can get rid off it by resting for some time, so that normal breathing rate resumes.
3. Myoglobin or muscle haemoglobin is the oxygen o carrying pigment of muscles.
4. Akhil is a lazy, irresponsible student. He is very casual about his studies and classes.

Differences between A-band and l-band:

S. No.	A-Band	I-Band
1.	It is formed of myosin filaments.	It is formed of only actin filaments.
2.	It gives dark appearance.	It gives light appearance.
3.	It has a light H-zone, in the centre.	It has dark Krause's membrane, in the centre.
4.	It is anisotropic band which possesses two type of proteins.	It is isotropic band which possesses only one type of proteins.

Gout occurs due to accumulation of uric acid crystals in the joints and causes in inflammation of joints which results in inflammation of joints and pain. Gout it self is a form of artheritis. The primary cause of pain is accumulation of uric acid which is not seen in other forms of artheritis.

Arhtritis is inflammation of joints. This happens mostly in synovial joints. Because of ageing and wear and tear the synovial fluid dries up. This leads to corrosion of cartilage. At the end the movement of joints is not as smooth as it should be. This results in general discomfort while doing normal tasks and causes swelling and pain of the affected joint.

1. The calcium ions after contraction are quickly pumped back to the sarcoplasmic cisternae. This leads to blocking of active sites on actin. The Z-line returns to the original position. Causing muscles to return to its original position, i.e., relaxation form.

2. Repeated activation of the muscles leads to accumulation of lactic acid due to anaerobic breakdown of glycogen in them which causes fatigue.