Locomotion and Movement PDF

Locomotion and Movement © 2022, Aakash BYJU'S. All rights reserved. Key Takeaway Locomotion 1 2 Muscle 3 4 Structure of contractile proteins © 2022, Aakash BYJU'S. All rights reserved. Movements 5 Structure of muscle 6 Cross bridge cycle 7 8 Human skeletal system © 2022, Aakash BYJU'S. All rights re...

Locomotion and Movement © 2022, Aakash BYJU'S. All rights reserved. Key Takeaway Locomotion 1 2 Muscle 3 4 Structure of contractile proteins © 2022, Aakash BYJU'S. All rights reserved. Movements 5 Structure of muscle 6 Cross bridge cycle 7 8 Human skeletal system © 2022, Aakash BYJU'S. All rights reserved. Light and dark bands 9 Sliding filament theory Axial skeleton Skull 10 11 Vertebral column Appendicular skeleton Pectoral girdle Sternum Bones of arms Ribs Pelvic girdle Joints 12 Synovial joints 13 Summary © 2022, Aakash BYJU'S. All rights reserved. Bones of legs Disorder of muscular and skeletal system​ Locomotion Movement  Locomotion: It is the ability of an entity or organism to move from one place to another.  Locomotion is a type of movement, but not all movements are locomotory.  Locomotion is a special type of movement where the organism changes its position.  Examples: o Limbs in humans for walking o Cilia in Paramecium Locomotion © 2022, Aakash BYJU'S. All rights reserved. Movements  It is the change of position in an organism. It is essential for all living organisms including humans.  Examples: o Pumping of blood o Breathing through lungs o Mobility of vesicles inside a vessel © 2022, Aakash BYJU'S. All rights reserved. Types of movement Amoeboid E.g. Amoeba Ciliary E.g. Cilia of trachea Muscular E.g. Jaws Movements Amoeboid movements    It occurs with the help of pseudopodia. Pseudopodia is formed by cytoplasmic streaming. o Cytoskeletal elements such as microfilaments aid in cytoplasmic streaming. Examples: Amoeba, macrophage, etc. © 2022, Aakash BYJU'S. All rights reserved. Ciliary movements   This type of movement occurs in some internal organs. o The organs that are lined with ciliated epithelium show this movement. Examples: Trachea, female reproductive system Muscular movements    It is the movement shown by limbs, jaws, tongue, etc. The contractile property of muscles is utilised for this movement. Examples: Humans and majority of multicellular organisms. Movements Types of movements based on control Involuntary movements Voluntary movements   These movements can be controlled consciously. They are associated with skeletal components and controlled voluntarily. © 2022, Aakash BYJU'S. All rights reserved.   They are under the control of the autonomic nervous system. These movements are involuntary, i.e., they cannot be controlled by our will. Muscle Myocyte  It is a type of specialised tissue originating from mesoderm.  It is made up of cells known as myocytes.  Myocytes provide contractility and allow muscles to gain the ability to contract.  The stimulus provided by a myocyte spreads to the neighbouring myocyte. Length = l Myocyte Length = l/2 Myocyte Length = l  Contractility: It is a property that allows it to shorten and return to its original state. © 2022, Aakash BYJU'S. All rights reserved. Muscle Unique properties of muscles Contractibility  It is the property that allows a muscle to shorten and return to its original state. Excitability  © 2022, Aakash BYJU'S. All rights reserved. It is the ability of a muscle to respond to a stimulus. Elasticity  It is the ability of a muscle to recoil or bounce back to its original length. Extensibility  It is the ability of a muscle to stretch itself. Muscle Types of muscles Smooth muscles   Tapering ends: The cells taper at both the ends. Striations are absent: The altering light and dark bands are absent, giving a smooth appearance to the muscles. © 2022, Aakash BYJU'S. All rights reserved. Skeletal muscles Cardiac muscles    It is present only in the heart. It is a contractile tissue that aids in the beating of the heart. Cardiac muscle helps in maintaining the cardiac cycle. o It has continuous rhythmic heart movements: contraction and relaxation.     It is closely associated with skeletal components of the body. Voluntary muscle: The movements of this muscle are under the control of the nervous system. Muscle fibres have a striated appearance under microscope. It enables the movements of body parts. Muscle Types of muscles Smooth muscles   It is also known as the following: o Visceral muscle: As it forms the lining of hollow organs o Non-striated muscle: As it lacks striation o Non-stripped muscle: As it appears smooth o Involuntary muscle: As it is involuntary in nature It assists in: o Transport of food through digestive tract o Transport of gametes through female genital tract © 2022, Aakash BYJU'S. All rights reserved. Skeletal muscles Cardiac muscles  It is also known as the following: o Striated muscle o Involuntary muscle  It is also known as the following: o Striped muscle o Striated muscle o Voluntary muscle  Examples: o Muscles of tongue o Muscles of limbs Structure of Muscle Fascia Skeletal muscle Muscle fibre Epimysium © 2022, Aakash BYJU'S. All rights reserved. Muscle fibre bundle (fascicle) Structure of Muscle Fascia Muscle bundle fibre   The collagenous sheath surrounding the muscle which holds together muscle bundle fibres. The muscle fibres are arranged parallelly in the form of a bundle known as a muscle bundle fibre or fascicle. Epimysium Muscle fibre   It is a dense connective tissue sheath surrounding a muscle. © 2022, Aakash BYJU'S. All rights reserved.  Each fascicle has many muscle fibres. Muscle fibres are arranged parallel to each other. Structure of Muscle Myofibril  A muscle fibre contains many filamentous myofibrils/myofilaments. Sarcoplasm   It is the cytoplasm of the striated muscle. Sarcoplasm contains lots of nuclei. Hence, it is termed as syncytium (multinucleated). Sarcolemma  Muscle fibres are covered by a layer of plasma membrane known as sarcolemma. Sarcoplasmic reticulum   © 2022, Aakash BYJU'S. All rights reserved. Sarcoplasm has the endoplasmic reticulum known as a sarcoplasmic reticulum that stores calcium. This calcium aids in muscle contraction. Structure of Muscle Myofibril  Each muscle fibre has many myofibrils. Each myofibril contains many proteins. Thick filament: Constitutes myosin   Thin filament: Constitutes actin Myofilaments are made up of actin and myosin that are also known as contractile proteins. Myosin and actin both are rod-like structures arranged parallel to each other. o They are longitudinal to myofibrils. The actin filaments are thinner than myosin filaments. © 2022, Aakash BYJU'S. All rights reserved. Structure of Contractile Proteins Structure of actin G actin Tropomyosin   Each F actin is a polymer of monomeric units known as G (globular protein) actin. F actin  Each actin filament has two filamentous actin known as F actin helically wound to each other. © 2022, Aakash BYJU'S. All rights reserved. It is the protein that runs close to F actin. Troponin   It is the filament that holds the tropomyosin and is present in regular intervals. It blocks the active binding sites of actin. Structure of Contractile Proteins Structure of myosin Myosin    Myosin is also known as the thick filament. It is the polymer of meromyosin. Monomeric proteins are known as meromyosins. Each meromyosin has two parts: HMM and LMM. HMM: Heavy meromyosin   Globular head: It is an active ATPase enzyme. It has binding sites for ATP and active sites for actin. It has a short arm. Cross arm: The head and the short arm project outwards at a regular distance and angle from each other and from the surface of myosin. LMM: Light memomyosin  © 2022, Aakash BYJU'S. All rights reserved. It is the tall. Light and Dark Bands  Light band Constitutes actin Dark band Constitutes myosin © 2022, Aakash BYJU'S. All rights reserved. Actin and myosin are arranged in the myofibril in such a way that they appear as light and dark bands. This gives the skeletal muscles a striated appearance. Light and Dark Bands Sarcomere is the portion between the successive Z lines. A sarcomere is a functional unit for contraction. I band o The light band contains actin. o It is also known as the I band or isotropic band.  M line o It is a thin, fibrous membrane. o It holds the dark bands together.  H zone o It is the central part of the thick filament that has only myosin or the thick filament. o The overlapping thin filaments are not present in this region.  © 2022, Aakash BYJU'S. All rights reserved. Z line o The I band is bisected by an elastic fibre known as the Z line. o The zigzag line cuts through the I band.  Dark band o The dark band has myosin. It is overlapped by actin filaments at the periphery. o It is also known as the A band or anisotropic band. o A band and I band are arranged alternately throughout the myofibril.  Light and Dark Bands I Band A Band I Band Z Line M Line H Zone Sarcomere © 2022, Aakash BYJU'S. All rights reserved. Muscle Contraction © 2022, Aakash BYJU'S. All rights reserved.  When an electrical signal reaches the neuromuscular junction, the neurotransmitter molecules are released.  The neurotransmitter molecules bind to the receptors on the sarcolemma. This generates an action potential in the muscle fiber.  Action potential - It is an electrical impulse that propagates on the muscle fiber.  The action potential spreads to both sides from the neuromuscular junction.  An action potential causes the sarcoplasmic reticulum to release calcium ions.  These calcium ions ultimately bring about the contraction of the muscle, by means of the cross-bridge cycle. Cross-Bridge Cycle Myosin-binding site masked at resting state Myosin-binding site Actin Troponin Troponin Actin filament Tropomyosin Myosin filament Myosin-binding sites exposed © 2022, Aakash BYJU'S. All rights reserved. Myson-binding site Tropomyosin Actin During action potential Ca2+binds to troponin causing conformational change Cross-Bridge Cycle Myosin head binds ATP ATP Myosin head pulls actin filament Myosin head hydrolyses ATP and is full of energy ADP P Myosin head binds actin ADP P ADP P © 2022, Aakash BYJU'S. All rights reserved. Cross-Bridge Cycle Myosin head releases ADP and P Myosin head binds fresh ATP ATP ADP P Myosin hydrolyses ATP ADP P © 2022, Aakash BYJU'S. All rights reserved. Myosin detaches from actin filament ATP Sliding Filament Theory Thin filament (actin) Z-line Thick filament (myosin) M-line Z-line H-zone I-band A-band Sarcomere © 2022, Aakash BYJU'S. All rights reserved. I-band Sliding Filament Theory Relaxed state of muscle Actin Z-line M-line M-line Sarcomere A I © 2022, Aakash BYJU'S. All rights reserved. H I Myosin Sliding Filament Theory Contracting state of muscle Z-line Actin M-line M-line Sarcomere A I © 2022, Aakash BYJU'S. All rights reserved. H I Myosin When the myosin head binds and pulls at the actin filament, the actin filaments come closer to the M-line. a. The Z-lines come closer b. The length of the sarcomere shortens. c. The lengths of the I bands shortens. d. The length of the A band remains the same. Sliding Filament Theory Maximally contracted state of muscle In this state of the muscle, the length of the sarcomere is the shortest. Actin Z-line M-line Sarcomere A I © 2022, Aakash BYJU'S. All rights reserved. H I Myosin Sliding Filament Theory Relaxation of muscle  After a muscle contracts, it has to come back to its original relaxed state.  The steps of contraction are reversed as follows:  o Calcium ions are pumped back into the sarcoplasmic reticulum. o Tropomyosin masks myosin-binding sites on actin once again. o So, myosin is no longer able to bind the actin filament. o Z lines go back to their original position. o Hence, the sarcomere goes back to its original length. The lengthening of the sarcomere means the relaxation of the muscle. © 2022, Aakash BYJU'S. All rights reserved. Tetanus or Tetanic Contraction  In a normal condition, an electric impulse comes from a motor neuron, the muscle contracts and then relaxes.  When the electric impulses come too fast, the muscle does not get the time to relax.  It is then in a state of continuous contraction. This is called tetanic contraction or tetanus. Muscle Fatigue  While exercising, the glycogen stored in the muscles is readily converted to its monomer glucose, which then undergoes cellular respiration in order to produce energy.  Glycogen levels become depleted in the exercising muscles after prolonged or strenuous exercise. © 2022, Aakash BYJU'S. All rights reserved. Red and White Muscle Fibres Every muscle of the body is composed of two types of muscle fibers: red and white, named so because of their colors. Red muscle fibre White muscle fibre  More blood vessels - more oxygen  Less blood vessels - less oxygen  More mitochondria - more aerobic respiration  Less mitochondria - more anaerobic respiration  Large amounts of myoglobin - stores oxygen - red in color  Less amount of myoglobin  Less sarcoplasmic reticulum - slow release of Ca2+ - slow muscle contraction  Extensive sarcoplasmic reticulum rapid release of Ca2+ - fast muscle contraction  Marathoners born with more red fibres  Sprinters born with more white fibres © 2022, Aakash BYJU'S. All rights reserved. Human Skeletal System  The hard, supportive, or protective elements of the animal body constitute the skeletal system or skeleton.  It consists of a framework of bones (206) and a few cartilages.  Functions o It supports the internal softer organs. o It protects the delicate parts. o It helps in movement. o It provides attachment for muscles. o It gives the body its shape and form. o It helps in the formation of blood cells in bone marrow. o It helps in breathing (tracheal rings, sternum, and ribs). o It helps in hearing as ear bones (middle ear) transmit sound vibrations. © 2022, Aakash BYJU'S. All rights reserved. Human Skeletal System On the basis of the position of the skeletal structures in the body, the skeleton is divided as follows: Axial (80 bones) Appendicular (126 bones) Skull Pectoral girdle Vertebral column Arm bones Sternum Pelvic girdle Ribs Leg bones © 2022, Aakash BYJU'S. All rights reserved. Axial Skeleton Skull  It is the bony framework of the head.  The skull is composed of the following set of bones: Cranial bones  Cranium is the skeleton of the head.  It is the outer protective covering of the brain.  It is made of 8 cranial bones. Cranial bones Parietal (2) Frontal (1) Ethmoid (1) Sphenoid (1) Temporal (2) Occipital (1) © 2022, Aakash BYJU'S. All rights reserved. Axial Skeleton Facial bones   It forms the front part of the skull. There are 14 facial bones. Facial bones Nasal (2) Palatine (2) Lacrimal(2) Zygomatic (2) Maxilla (2) Mandible (1) Vomer (1) Inferior nasal conchae (2) © 2022, Aakash BYJU'S. All rights reserved. Axial Skeleton Ear ossicles  Ear ossicles are also known as auditory ossicles.  They are the 3 bones present in the middle part of human ears. Incus  So, there are a total of six ear ossicles in the body. Malleus  The ear ossicles are the three of the smallest bones in the human body. © 2022, Aakash BYJU'S. All rights reserved. Ear ossicles Stapes Axial Skeleton Hyoid  It is a U-shaped bone.  It is present at the base of the buccal cavity above the larynx.  It is the only bone that is not in contact with any other bone.  It is also known as the tongue bone.  It acts as a point of attachment for certain tongue muscles and the floor of the mouth. © 2022, Aakash BYJU'S. All rights reserved. Hyoid Bone Hyoid bone Hyoid bone Larynx Axial Skeleton Mnemonics Bones of face Bones of cranium Fluffy Puppies On Every Third Street Victor Can Not Make My Pet Zebra Laugh Frontal Ethmoid Vomer Mandible Parietal Temporal Conchae (inferior) Palatine Occipital Sphenoid Nasal bone Zygomatic Maxilla Lacrimal © 2022, Aakash BYJU'S. All rights reserved. Axial Skeleton Skull Based on the number of articulations, skulls are of two types: Monocondylic Dicondylic  1 occipital condyle  2 occipital condyle  E.g. - birds, reptiles  E.g. - humans 1 Occipital condyle  Occipital condyles are bony articulations that are projections on the occipital bone. © 2022, Aakash BYJU'S. All rights reserved. 2 Occipital condyles  Humans have dicondylic skulls.  In the posterior end, there are these two rounded occipital condyles.  They attach with the first vertebrae. Axial Skeleton Vertebral column  The vertebral column or the backbone is curved and lies dorsally in our body.  It comprises 26 serially arranged units called vertebrae.  It extends from the base of the skull and forms the framework of the trunk.  Functions o It bears the bodyweight in the standing position and while the body is in motion. o It protects the spinal cord. o It supports the head. o It serves as the point of attachment for the ribs. © 2022, Aakash BYJU'S. All rights reserved. Vertebral Column Cervical Thoracic Lumbar Sacrum Coccyx Axial Skeleton Vertebral column  The components of the vertebral column are known as vertebrae.  The anterior with a large disc-like flattened part is known as the body or centrum.  The posterior portion is known as neural arch.  The neural arch forms a hole known as vertebral foramen.  The 24 vertebral foramen together form vertebral canal/neural canal. The spinal cord passes through this neural canal. © 2022, Aakash BYJU'S. All rights reserved. Posterior Centrum/ body Vertebral foramen Neural arch Anterior Axial Skeleton Vertebral column The vertebrae are grouped into five types, depending on the level of the vertebral column where they are found: Cervical (7)  It is present in the neck.  They are 7 in number in almost all mammals.   The first cervical vertebra is the atlas. It articulates with the occipital condyles and supports the head. The second vertebra is known as the axis. © 2022, Aakash BYJU'S. All rights reserved. C1 (Atlas) C2 (Axis) C3 C4 C5 C6 C7 Axial Skeleton Thoracic (12)  They are present in the chest level.  They are 12 in number.  They are larger and stronger than cervical vertebrae.  They are joined with the ribs. T1 T2 T3 T4 T5 T6 T7 T8 T9 T 10 T 11 T 12 © 2022, Aakash BYJU'S. All rights reserved. Axial Skeleton Lumbar (5)  Lumbar vertebrae are present in the lower back.  They are five in number.  They are the largest and strongest of all vertebrae.  They have to bear the weight of the whole body when the body is in a standing position. © 2022, Aakash BYJU'S. All rights reserved. L1 L2 L3 L4 L5 Axial Skeleton Sacrum (1) (Fused)  Five sacral vertebrae are fused, forming the sacrum.  The vertebrae are separate in the beginning, but start to fuse during adolescence.  The sacrum lies between the innominate or hip bones. Coccyx (1) (Fused)  The four coccygeal vertebrae fuse to form the coccyx. 1  The vertebrae separate in the beginning, but start to fuse during adolescence. 2  The coccyx is considered to be the vestigial tail in humans. 3 4 © 2022, Aakash BYJU'S. All rights reserved. Axial Skeleton Sternum Sternum © 2022, Aakash BYJU'S. All rights reserved.  The sternum is also known as the breastbone.  It is a flat dagger-shaped bone.  It is present just under the skin in the front and middle of the chest.  It provides the point of attachment for ribs.  It also protects the organs in the thoracic region and helps in respiration. Axial Skeleton Ribs Thoracic vertibrae  They are the thin, flat, and curved bones that form a protective cage around the organs of the upper body.  The ribs are composed of 24 bones arranged in 12 pairs.  They are dorsally connected to the vertebral column (thoracic vertebrae) and ventrally to the sternum.  They have two articulations/attachment surfaces on their dorsal ends. Hence, they are known as bicephalic.  Functions: o They protect the organs present in the thoracic cavity and the kidneys. o They also help in the respiration process. Rib Coastal cartilage Rib Sternum © 2022, Aakash BYJU'S. All rights reserved. Axial Skeleton Ribs Sternum True ribs False ribs Floating ribs L1 Vertebra © 2022, Aakash BYJU'S. All rights reserved. Axial Skeleton Ribs True ribs    The first seven pairs of ribs are known as true ribs. They are dorsally attached to the thoracic vertebrae. They are ventrally connected to the sternum with the help of hyaline cartilage, known as costal cartilage. © 2022, Aakash BYJU'S. All rights reserved. False ribs   The eighth, ninth, and tenth pairs are known as vertebrochondral (false) ribs. They do not articulate directly instead anteriorly connect indirectly with the sternum by costal cartilage of the seventh rib. Floating ribs   The last two pairs (11th and 12th) of ribs are not connected ventrally to the sternum or the cartilage. Therefore, they are known as floating ribs. Thoracic vertebrae, ribs, and sternum together form the rib cage. Appendicular Skeleton Pectoral girdle  It lies along the transverse (side) axis.  The bones of the limbs along with their girdles constitute the appendicular skeleton.  It is called so because it gives support to the appendages.  It comprises 126 bones. Arm Pelvic girdle Leg © 2022, Aakash BYJU'S. All rights reserved. Appendicular Skeleton Pectoral girdle Pectoral girdle Scapula © 2022, Aakash BYJU'S. All rights reserved. Clavicle  Also known as the shoulder girdle  Acts as a point of attachment for the upper limbs and the arm muscles  Made up of two halves o Scapula o Clavicle  The scapula is a large triangular flat bone.  It consists of a spine and a body.  The slightly elevated ridge is known as the spine. Appendicular Skeleton Pectoral girdle Scapula Acromion Flat, expanded process Spine Sharpe ridge Body Large triangular bone © 2022, Aakash BYJU'S. All rights reserved.  The spine projects as a flat expanded process known as the acromion.  The scapula is situated in the dorsal part of the thorax.  It lies between the second and the seventh rib.  Below the acromion is a depression known as the glenoid cavity. o It articulates with the head of the humerus to form the shoulder joint. Appendicular Skeleton Pectoral girdle Clavicle Superior view Acromial end Inferior view Collar bone Clavicle © 2022, Aakash BYJU'S. All rights reserved.  Pectoral girdle has two clavicles.  Each clavicle is a long slender bone with two curvatures.  This bone is commonly known as the collar bone.  The clavicle articulates with the acromion of the scapula.  The clavicle and the scapula together make the pectoral girdle. Appendicular Skeleton Bones of arms  Each arm is made of 30 bones Humerus Phalanges (14) Digits (5) Radius Metacarpals (5) Palm bones Carpals (8) Wrist bones Ulna Bones of wrist © 2022, Aakash BYJU'S. All rights reserved. Bones of arm Appendicular Skeleton Pelvic girdle Ilium Acetabulum  The pelvic girdle bones help in the articulation of the lower limbs.  It is formed by two innominate bones. They are also known as the coxal or hip bones.  Each hip bone is made by the fusion of three bones: o ilium o ischium o pubis  At the point of fusion of the above bones is a cavity known as acetabulum, to which the thigh bone articulates. Pubis Ischium Femur (Thigh bone) © 2022, Aakash BYJU'S. All rights reserved. Appendicular Skeleton Pelvic girdle The pubic symphysis is made of fibrous cartilage that joins the two coxal (hip) bones ventrally. Pubis Pubis symphysis © 2022, Aakash BYJU'S. All rights reserved. Appendicular Skeleton Bones of legs  Each leg is made of 30 bones. Phalanges (14) Digits (5) Metatarsals (5) Femur (2) (Thigh bone) Longest and strongest in the body Patella (2) Knee cap Cup-shaped bone Fibula (2) Shorter, thinner, deeper Tarsals (7) Ankle bones © 2022, Aakash BYJU'S. All rights reserved. Tibia (2) Longer, thicker, front Total Number of Bones Bones Number Bones Number Cranial bones 8 Ribs 24 Facial bones 14 Scapula 2 Ear ossicles 6 Clavicle 2 Hyoid 1 Arm bones 60 Vertebral column 26 Hip bones 2 Sternum 1 Leg bones 60 Total © 2022, Aakash BYJU'S. All rights reserved. 206 Joints  Joints are the points of contact between: o Bones o Bones and cartilages  Functions of joints: o Hold bones together o Bear weight of the whole body o Allow movements in coordination with muscles © 2022, Aakash BYJU'S. All rights reserved. Joints (On the basis of structure and movement) Fibrous Cartilaginous Synovial No movement Slight movement Considerable movement Joints Fibrous    Cartilaginous Fibrous joints do not allow any movement. Sutures are a type of fibrous joints in the skull. Skull bones are fused end to end with the help of dense fibrous connective tissues to form sutures.    These joints permit limited movements. The bones are joined together with the help of a cartilage. Example: The joint between the adjacent vertebrae in the vertebral column.    These joints allow considerable movement. They have a fluid-filled synovial cavity between the articulating surfaces of the two bones. Examples: Movement of head, wrist movement etc. Synovial cavity Sutures Cartilage © 2022, Aakash BYJU'S. All rights reserved. Synovial Articular cartilage Synovial Joints Types of synovial joints Pivot joint  Also known as rotary joint  A ring-like movement is seen  E.g. - Joint between atlas and axis Gliding joint  Also known as the plane joint  Characterised by smooth surfaces that can glide over one another  E.g. - Joint between the carpals © 2022, Aakash BYJU'S. All rights reserved. Pivot joint Gliding joint Synovial Joints Condyloid joint  The condyloid joint allows movement but not rotation.  E.g. - Wrist joint Saddle joint  The saddle joint does not allow rotation.  It enables back-and-forth and side-to-side movements.  E.g. - Joint between the carpals and the metacarpals of thumb © 2022, Aakash BYJU'S. All rights reserved. Condyloid joint Saddle joint Synovial Joints Ball and socket joint  Permits movement in all directions  E.g. - Shoulder joint, hip joint Hinge joint  Allows the opening and closing in one direction, along one plane  E.g. - Elbow joint, knee joint Ball and socket joint © 2022, Aakash BYJU'S. All rights reserved. Hinge joint Disorders of Muscular and Skeletal System Myasthenia gravis    Myasthenia gravis is a rare autoimmune neuromuscular disorder that causes weakness in skeletal muscles. It can also lead to paralysis. o An autoimmune disease is a condition where the body's immune system mistakenly attacks its own organs. The most commonly affected muscles are those of the eyes, face, and the ones involved in swallowing. © 2022, Aakash BYJU'S. All rights reserved. Muscular dystrophy  It is a genetic-inherited disorder.  It causes progressive degeneration of skeletal muscles.  Muscles are damaged in this disorder.  It causes difficulty in: o o o Walking Swallowing Breathing Disorders of Muscular and Skeletal System Arthritis Tetany  Rapid spasms (wild contractions) occur in muscles due to low Ca++ in body fluid.  The articulating cartilage wears away in this condition, leading to more friction between the bones.  Spasms are rapid contractions  Symptoms: o Joint pain o Stiffness Gout Osteoporosis  It is an age-related disorder, characterised by decreased bone mass and increased chances of fractures. © 2022, Aakash BYJU'S. All rights reserved.  It is the inflammation of joints due to the accumulation of uric acid crystals. Summary Types of movement Amoeboid E.g. - Amoeba Ciliary E.g. - Cilia of trachea Muscular E.g. - Jaws Types of muscles Smooth muscles E.g. - Muscles of digestive tract © 2022, Aakash BYJU'S. All rights reserved. Cardiac muscles E.g. - Muscles of heart Skeletal muscles E.g. - Muscles of limbs Summary Structure of muscle fibre Myofibril Sarcoplasm Sarcolemma Sarcoplasmic reticulum © 2022, Aakash BYJU'S. All rights reserved. Summary Structure of skeletal muscle Fascia Skeletal muscle Muscle fibre Muscle fibre bundle (fascicle) Epimysium © 2022, Aakash BYJU'S. All rights reserved. Summary Structure of actin actin Structure of  Also known as the thin filament G actin F actin © 2022, Aakash BYJU'S. All rights reserved. Tropomyosin Troponin Summary Structure of myosin    Myosin is also known as the thick filament. It is the polymer of monomeric proteins called meromyosin. Each meromyosin has two parts: HMM and LMM HMM: Heavy meromyosin Cross arm LMM: Light meromyosin © 2022, Aakash BYJU'S. All rights reserved. Summary Thin filament(actin) Z-line Thick filament(myosin) M-line Z-line H-zone I-band A-band Sarcomere © 2022, Aakash BYJU'S. All rights reserved. I-band Summary Muscle contraction  Neuromuscular junction- The place where the end-point of a motor neuron meets the sarcolemma of the muscle is called a neuromuscular junction or motor end plate.  Action potential- Action potential is an electrical impulse that propagates on the muscle fibre. Tetanus/ Tetanic contraction  When the electric impulses come too fast, the muscle does not get the time to relax.  It is then in a state of continuous contraction. This is called tetanic contraction or tetanus. © 2022, Aakash BYJU'S. All rights reserved. Summary Cross-bridge cycle A. Myosin-binding site masked at resting state. B. During action potential Ca2+ binds to troponin causing conformational change. C. Myosin-binding sites exposed. D. Myosin head binds ATP. E. Myosin head hydrolyses ATP and is full of energy. F. Myosin head binds actin. G. Myosin head pulls actin filament. H. Myosin head releases ADP and P. I. Myosin head binds fresh ATP. J. Myosin detaches from actin filament. K. Myosin hydrolyses ATP. L. Myosin binding and releasing cycle continues as long as there is Ca2+. © 2022, Aakash BYJU'S. All rights reserved. Summary On the basis of the position of the skeletal structures in the body, the skeleton is divided as follows: Axial Appendicular Skull Pectoral girdle Sternum Vertebral column © 2022, Aakash BYJU'S. All rights reserved. Ribs Arm Pelvic girdle Leg Summary Skull Facial bones(14): Cranial bones(8): Frontal Parietal Sphenoid Ethmoid Nasal Lacrimal Palatine Zygomatic Inferior nazal concha Temporal Occipital Vomer Maxilla Mandible © 2022, Aakash BYJU'S. All rights reserved. Summary Vertebral column Rib cage True ribs (1-7) Hyaline cartilage Thoracic vertebrae(12) Lumbar vertebrae(5) Sacrum(1) Coccyx(1) © 2022, Aakash BYJU'S. All rights reserved. True ribs (1-7) Sternum Thoracic vertebrae False ribs (8-10) Floating ribs (11-12) Summary Clavicle Scapula Femur Radius Hip bone Femur Patella Ulna Fibula Metacarpals Metatarsals Phalanges Phalanges Bones of upper limb and pectoral girdle © 2022, Aakash BYJU'S. All rights reserved. Bones of lower limb and pelvic girdle Summary Joints (On the basis of structure and movement) Fibrous No movement © 2022, Aakash BYJU'S. All rights reserved. Cartilaginous Slight movement Synovial Slight movement Summary Types of synovial joints Pivot joint Ball and socket joint Hinge joint Saddle joint Condyloid joint Gliding joint © 2022, Aakash BYJU'S. All rights reserved. Summary Disorders of muscular and skeletal system Myasthenia gravis Autoimmune neuromuscular disease causing muscle weakness Muscular dystrophy Progressive degeneration of skeletal muscle Tetany Rapid spasms in muscles due to low calcium ions Arthritis Osteoporosis Gout © 2022, Aakash BYJU'S. All rights reserved. Inflammation in joints Decrease in the bone mass increases the risk of fractures Inflammation of joints due to the accumulation of uric acid crystals