17. Locomotion and Movement

Class 11 Biology Chapter 17 Locomotion and Movement

Chapter 17 : Locomotion and Movement

Class 11 Biology Chapter 17 Locomotion and Movement Exercise Questions and Answers :

1. Draw the diagram of a sarcomere of skeletal muscle showing different regions.

Answer :

The diagram of a sarcomere of skeletal muscle

2. Define sliding filament theory of muscle contraction.

Answer : The sliding filament theory of muscle contraction is a process initiated by a neural signal transmitted from the central nervous system to a muscle fiber via a motor neuron. This signal releases acetylcholine, generating an action potential and leading to the release of calcium ions in the sarcoplasm. Elevated levels unmask active sites on actin filaments, enabling myosin heads to bind to them, forming cross-bridges that use ATP energy to induce muscle contraction.

3. Describe the important steps in muscle contraction.

Answer : Muscle contraction is a complex physiological process involving several steps are :

Stages in cross bridge formation, rotation of head and breaking of cross bridge .

Sliding-filament theory of muscle contraction :

(i) The process begins with a motor neuron sending an electrical signal, known as an action potential, to the muscle fibers it innervates.

(ii) The action potential triggers the release of acetylcholine, a neurotransmitter, at the neuromuscular junction, where the nerve and muscle fiber meet.

(iii) Acetylcholine binds to receptors on the muscle cell membrane, causing it to depolarize. This depolarization spreads throughout the muscle fiber via the transverse tubules, which triggers the release of calcium ions from the sarcoplasmic reticulum.

(iv) Calcium ions bind to the protein troponin, which shifts tropomyosin, revealing binding sites on actin filaments.

(v) Myosin heads bind to actin, forming cross-bridges.

(vi) Myosin heads pivot, pulling actin filaments toward the center of the sarcomere.

(vii) ATP binds to myosin, causing the myosin head to detach from actin. ATP is hydrolyzed to ADP and inorganic phosphate, resetting the myosin head for another cycle.

(viii) Repeated cycles of cross-bridge formation and power strokes result in muscle contraction.

(ix) When neural stimulation ceases, calcium is actively transported back into the sarcoplasmic reticulum, leading to muscle relaxation.

These steps ensure efficient muscle contraction and are vital for various physiological functions, including movement and force generation.

4. Write true or false. If false change the statement so that it is true.

(a) Actin is present in thin filament

(b) H-zone of striated muscle fibre represents both thick and thin filaments.

(d) There are 11 pairs of ribs in man.

(e) Sternum is present on the ventral side of the body.

Answer : (a) True - Actin is a component of the thin filament in muscle fibers.

(b) False - The H-zone of a striated muscle fiber represents only the thick filaments; thin filaments do not extend into this region.

(d) False - There are 12 pairs of ribs in humans, including 7 pairs of true ribs, 3 pairs of false ribs, and 2 pairs of floating ribs.

(e) True - The sternum is indeed located on the ventral (front) side of the body and serves as a central attachment point for the ribs.

5. Write the difference between :

(a) Actin and Myosin

(b) Red and White muscles

Answer : (a) The main differences between Actin and Myosin:

Actin	Myosin
Thin filament protein	Thick filament protein
Found in the I band and extends into the A band of a sarcomere in muscle fibers	Primarily located in the A band of a sarcomere
Made up of globular G-actin (monomers) that polymerize to form F-actin (filaments)	Composed of long polypeptide chains with globular heads
Forms the thin filaments in sarcomeres and interacts with myosin during muscle contraction	Binds with actin and, through a cyclic process, moves actin filaments to cause muscle contraction
Tropomyosin and troponin help regulate the interaction of actin and myosin	No regulatory proteins
Actin provides binding sites for myosin heads during muscle contraction	Myosin heads (cross-bridges) bind to actin to facilitate muscle contraction
Actin remains relatively stationary while myosin heads pivot and slide actin filaments	Myosin heads pivot and "walk" along actin filaments, causing them to slide and the muscle to contract
Smaller in size compared to myosin	Larger in size compared to actin
Helical structure with active sites for myosin binding	Long, fibrous structure with heads and tails
Forms the thin filaments that, along with myosin, make up the sarcomeres	Forms the thick filaments in sarcomeres

(b) The main differences between red and white muscles:

Red Muscles	White Muscles
High - contain abundant myoglobin, which gives them a red or dark color	Low - contain little myoglobin, resulting in a pale or white appearance
Slow-twitch muscle fibers (Type I)	Fast-twitch muscle fibers (Type II)
Slow and sustained contractions	Rapid and brief contractions
High - resistant to fatigue due to a rich blood supply and myoglobin	Low - fatigue quickly due to limited blood supply and reliance on anaerobic metabolism
High - have a high density of mitochondria for sustained energy production	Low - have fewer mitochondria
Well-vascularized with a rich blood supply	Poor blood supply, resulting in a lower capillary density
Primarily oxidative metabolism - relies on aerobic energy production	Primarily glycolytic metabolism - relies on anaerobic energy production
Suited for endurance activities, such as long-distance running or sustained activities	Suited for brief, intense activities, such as sprinting or weightlifting
Smaller fiber diameter compared to white muscles	Larger fiber diameter compared to red muscles
Found in postural muscles, such as those in the back and legs	Found in muscles used for short bursts of activity, such as the biceps and pectorals
Activated first during low-intensity activities	Activated during high-intensity, quick movements
High capillary density for efficient oxygen delivery	Lower capillary density for less oxygen delivery
Slow myosin ATPase activity	Fast myosin ATPase activity

Pectoral Girdle	Pelvic Girdle
Located in the upper body, associated with the shoulder and upper limb	Located in the lower body, associated with the hip and lower limb
Composed of two paired bones: the scapula (shoulder blade) and clavicle (collarbone)	Composed of two paired bones: the ilium, ischium, and pubis, which fuse to form the hip bone (os coxae)
Articulates with the humerus, forming the shoulder joint	Articulates with the sacrum, forming the sacroiliac joint and with the femur to create the hip joint
Offers a wide range of motion, allowing the upper limbs to move freely	Provides stability and support for the lower limbs, restricting mobility
Serves as the attachment point for the upper limbs (arms)	Serves as the attachment point for the lower limbs (legs)
Primarily responsible for mobility and manipulation of objects	Primarily responsible for weight-bearing and locomotion
Consists of flat and scapula bones that allow for flexibility	Composed of robust and weight-bearing structures
Not designed for weight-bearing; focuses on motion	Designed to support the body's weight and absorb forces from walking and other movements
Generally, similar in shape between males and females	Often exhibit sexual dimorphism, with differences between the male and female pelvis to accommodate childbirth
Provides no direct protection to vital organs	Offers some protection to the reproductive and digestive organs located in the pelvic cavity

6. Match Column I with Column II :

Column I	Column II
(a) Smooth muscle	(i) Myoglobin
(b) Tropomyosin	(ii) Thin filament
(c) Red muscle	(iii) Sutures
(d) Skull	(iv) Involuntary

Answer : The matching of Column I with Column II :

(a) Smooth muscle -------- (iv) Involuntary

(b) Tropomyosin --------- (ii) Thin filament

(d) Skull --------- (iii) Sutures

7. What are the different types of movements exhibited by the cells of human body?

Answer : Cells in the human body display a range of movements crucial for various functions. Amoeboid movement, seen in immune cells, involves the extension and retraction of pseudopodia for crawling. Ciliary movement, as in respiratory tract cells, utilizes cilia to move mucus and debris. Flagellar movement propels sperm cells forward. Muscle cells contract and relax for voluntary and involuntary movements. Cytoplasmic streaming aids in nutrient uptake in plant cells. Neuronal axon transport carries materials along neuron axons. Phagocytosis allows immune cells to engulf foreign particles. Chemotaxis guides cells along chemical gradients. Cell division involves movements for genetic separation, while cell migration is essential in processes like wound healing and embryonic development.

8. How do you distinguish between a skeletal muscle and a cardiac muscle?

Answer : Skeletal muscles and cardiac muscles can be distinguished based on several characteristics :

Location :

Skeletal Muscle : Skeletal muscles are attached to the skeletal components of the body, such as bones.

Cardiac Muscle: Cardiac muscles are found exclusively in the heart.

Appearance :

Skeletal Muscle : Skeletal muscles have a striped or striated appearance when viewed under a microscope.

Cardiac Muscle : Cardiac muscles also appear striated or striped.

Control:

Skeletal Muscle : Skeletal muscles are under voluntary control, meaning their activities can be consciously regulated by the nervous system.

Cardiac Muscle : Cardiac muscles are involuntary in nature. They do not rely on direct nervous system control for their contractions. Instead, the heart's contractions are regulated by the cardiac conduction system and hormones.

Function :

Skeletal Muscle: Skeletal muscles are primarily responsible for locomotory actions, allowing for body movement, posture changes, and various voluntary movements.

Cardiac Muscle: Cardiac muscles have the unique function of contracting rhythmically to pump blood throughout the circulatory system, maintaining blood circulation.

These differences highlight the contrasting characteristics and functions of skeletal and cardiac muscles

9. Name the type of joint between the following:-

(a) atlas/axis

(b) carpal/metacarpal of thumb

(d) femur/acetabulum

(e) between cranial bones

(f) between pubic bones in the pelvic girdle

Answer : (a) Atlas/Axis: Pivot joint .

(b) Carpal/Metacarpal of thumb: Saddle joint .

(d) Femur/Acetabulum: Ball-and-socket joint .

(e) Between Cranial Bones: Fibrous (Suture) joint .

(f) Between Pubic Bones in the Pelvic Girdle: Cartilaginous (Symphysis) joint .

10. Fill in the blank spaces:

(a) All mammals (except a few) have __________ cervical vertebra.

(b) The number of phalanges in each limb of human is __________

(d) In a muscle fibre is stored in __________

(e) __________ and __________ pairs of ribs are called floating ribs.

(f) The human cranium is made of __________ bones.

Answer : (a) All mammals (except a few) have ' 7 ' cervical vertebrae.

(b) The number of phalanges in each limb of a human is ' 14 ' .

(d) In a muscle fiber, is stored in the ' sarcoplasmic reticulum ' .

(e) ' 11th ' and ' 12th ' pairs of ribs are called floating ribs.

(f) The human cranium is made of ' 8 ' bones.