Locomotion and Movement PDF

Locomotion is the voluntary movements resulting in a change in location. It includes muscles which are mesodermal in origin. Muscles constitute 40-50% of the body weight. Muscles have excitability, contractility, extensibility & elasticity. Striations present Voluntary Attached t...

Locomotion is the voluntary movements resulting in a change in location. It includes muscles which are mesodermal in origin. Muscles constitute 40-50% of the body weight. Muscles have excitability, contractility, extensibility & elasticity. Striations present Voluntary Attached to skeleton Rich blood supply Fatigue muscle Muscle fibre is multinucleate (syncitium) Numerous mitochondria Striations absent Involuntary Found in visceral organs (alimentary canal, reproductive tract, urinary bladder etc). Poor blood supply Non-fatigue Uninucleate Less mitochondria Striations present Involuntary Found only in heart wall Rich blood supply Non-fatigue Uninucleate Numerous mitochondria Skeletal (striated) muscles Visceral (smooth) muscles Cardiac muscles Striations present Striations absent Striations present Voluntary Involuntary Involuntary In visceral organs (alimentary Attached to skeleton canal, reproductive tract, In heart wall urinary bladder etc). Rich blood supply Poor blood supply Rich blood supply Fatigue muscle Non-fatigue Non-fatigue Muscle fibre is multinucleate Uninucleate Uninucleate (syncitium) Numerous mitochondria Less mitochondria Numerous mitochondria Skeletal muscle is made of number of muscle bundles (fascicles) held together by fascia (collagenous connective tissue layer). Each fascicle contains number of muscle fibres. Muscle fibres are lined by plasma membrane (sarcolemma) enclosing the sarcoplasm. Each muscle fibre contains parallelly arranged myofilaments (myofibrils). Each myofibril has alternate dark (Anisotropic or A-band) and light striations (Isotropic or I- band) on it. The striation is due to the presence of 2 fibrous contractile proteins- thin Actin filament and thick Myosin filament. I-bands contain actin. A-bands contain actin & myosin. They are arranged parallel to each other. A-band bears a lighter region at the middle called H –band. It is formed of only myosin. A thin dark line (M-line) runs through the centre of H-zone. When muscle contracts, actin filaments on either sides partially overlap so that H-zone disappears. I-band is bisected by a dense dark band called Z-line. Region between two Z-lines is called sarcomere. Sarcomeres are the structural and functional units of a muscle. Each actin filament is made of 2 filamentous (F) actins. They form double helix. Each ‘F’ actin is a polymer of monomeric Globular (G) actins. Actin filaments contain 2 other proteins namely tropomyosin & troponin. Two filaments of tropomyosin run along the grooves of the ‘F’ actins double helix. Troponin has 3 subunits. It is located at regular intervals on the tropomyosin. In the resting state, a subunit of troponin masks the binding sites for myosin on the actin filaments. Each myosin filament is a polymer of many monomeric proteins called Meromyosins. Each meromyosin has 2 parts: A globular head (heavy meromyosin or HMM) with a short arm. A tail (light meromyosin or LMM). HMM component (head + short arm) projects outwards at regular distance and is called cross arm. Globular head is an active ATPase enzyme. It has binding sites for ATP and active sites for actin. According to sliding filament theory, contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments. A neural signal (impulse) is sent by the CNS via motor neuron. (A motor neuron + muscle fibres = a motor unit). Impulses reach the neuromuscular junction (Motor-end plate). It is the junction between a motor neuron and sarcolemma of the muscle fibre. A neurotransmitter (Acetylcholine) is released by neuromuscular junction. It generates an action potential in the sarcolemma. The action potential spreads through the muscle fibre and causes the release of Ca2+ ions into the sarcoplasm. Ca binds with a subunit of troponin on actin filaments and removes the masking of active sites for myosin. Using the energy from ATP hydrolysis, myosin head binds to the exposed active sites on the actin to form a cross bridge. This pulls the actin filaments towards the centre of ‘A’ band. The ‘Z’ line attached to these actins is also pulled inwards. So the sarcomere shortens (contraction). ‘I’ bands get shortened, and ‘A’ bands retain the length.  The myosin releases the ADP and Pi and goes back to its relaxed state. A new ATP binds and the cross-bridge is broken. The ATP is again hydrolyzed by the myosin head and the cycle of cross-bridge formation and breakage is repeated causing further sliding. When Ca2+ ions are pumped back to the sarcoplasmic cisternae, the actin filaments are again masked. This causes the return of ‘Z’ lines back to their original position, i.e., relaxation. The reaction time of the fibres vary in different muscles. Repeated activation of the muscles leads to the accumulation of lactic acid. It causes muscle fatigue. This is due to anaerobic breakdown of glycogen in muscles. Red (Aerobic) muscle fibres White muscle fibres Red coloured due to the presence of White coloured due to the lesser myoglobin. amount of myoglobin Plenty of mitochondria Small amount of mitochondria Aerobic metabolism (utilize large Anaerobic metabolism amount of O2) Slow and sustained contraction Fast contraction for short period Consists of a framework of bones (206) and few cartilages. Bone has a very hard matrix due to Ca salts. Cartilage has slightly pliable matrix due to chondroitin salts. Cranial bones (8): Frontal (1), Parietals (2), Temporal (2), Occipitals (1), Sphenoid (1), Ethmoid (1) Facial bones (14): Nasals (2), Maxillae (2), Zygomatics (2), Lachrymals (2), Palatines (2), Inferior nasals (2), Mandible (1), Vomer (1) Hyoid bone (1): U-shaped bone found at the floor of buccal cavity. Ear ossicles (3 x 2 = 6): Maleus, Incus and stapes.  The skull articulates with first vertebra (atlas) of vertebral column with the help of 2 occipital condyles (dicondylic skull). Formed of 26 vertebrae. They are 5 types: Cervical vertebrae (7) Thoracic vertebrae (12) Lumbar vertebrae (5) Sacral vertebrae (1-fused) Coccygeal vertebrae (1-fused) Vertebra has a central hollow portion (neural canal) through which the spinal cord passes. Number of cervical vertebrae are 7 in almost all mammals. Vertebral column protects spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back.  It includes 1 Flat bone on the ventral midline of thorax. 3 types: True ribs (first 7 pairs) Vertebrochondral (false) ribs (8th, 9th & 10th pairs) Floating ribs (11th & 12th pairs) Each rib has 2 articulation surfaces on its dorsal end. So it is called bicephalic. True ribs are attached to thoracic vertebrae and ventrally connected to sternum with the help of Hyaline cartilage. False ribs do not articulate directly with the sternum but join the 7th rib with the help of Hyaline cartilage. Floating ribs are not connected ventrally.  30 x 2 = 60 bones. They include Humerus (1) Radius(1) & ulna (1) Carpals (wrist bones- 8) Metacarpals (palm bones-5) Phalanges (digits-14) 30 x 2 = 60 bones They include Femur (thigh bone- 1) Patella (knee cap- 1) Tibia (1) & fibula (1) Tarsals (ankle bones-7) Metatarsals (5) Phalanges (digits-14)  2 x 2 = 4 bones They are formed of Clavicle (collar bone-2) Scapula (shoulder blade-2) Scapula is a large triangular flat bone situated in dorsal part of the thorax between second and 7th ribs. Scapula has a slightly elevated ridge (spine) which projects as a flat, expanded process called the acromion. The clavicle articulates with this. Below the acromion is a depression (glenoid cavity) which articulates with the head of humerus to form the shoulder joint. 2 x 1 = 2 bones Formed of 2 coxal bones. Each coxal bone is formed by the fusion of 3 bones- Ilium, Ischium & pubis. At the point of fusion of Ilium, Ischium & Pubis is a cavity (Acetabulum) to which the thigh bone articulates. The 2 halves of the pelvic girdle meet ventrally to form pubic symphisis containing fibrous cartilage. Joints are points of contact between bones, or between bones and cartilages. They are 3 types: Fibrous (Immovable) joints Cartilaginous (Slightly movable) joints Synovial (movable) joints Immovable joints E.g. sutures between flat skull bones. Slightly movable joints. Bones are joined together with the help of cartilages. E.g. Joints between the adjacent vertebrae. Movable joints. They are characterized by the presence of a fluid filled synovial cavity between articulating surfaces of the 2 bones.  Types of Synovial joints Examples Ball & socket joint Shoulder joint & hip joint. Hinge joint Knee joint, elbow joint etc. Pivot joint Joints b/w atlas & axis. Gliding joint Joints b/w carpals. Saddle joint Joints b/w carpal & metacarpal of thumb. It is the rapid spasm in muscle due to low Ca2+ in body fluid. Auto immune disorder. It affects neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscles. Progressive degeneration of skeletal muscles mostly due to genetic disorder. It is the inflammation of joints It is the inflammation of joints due to accumulation of uric acid crystals. Age-related disorder characterized by decreased bone mass and increased chances of fractures. Decreased level of estrogen is a common cause.