Hotshot topics series for NEET Locomotion & Movement (Study Notes+Video Class)

By Gagan Makkar|Updated : February 28th, 2020

In this article, we are providing you with all Short Notes on the Locomotion and Movement for NEET 2020! This is an important chapter from Unit Human Physiology to pay attention as 2-3 questions have been asked every year in various medical examinations like NEET, AIIMS, JIPMER. The article includes detailed points on Locomotion and Movement. So Let's begin with a brief introduction about what is the Locomotion. You can also download the Locomotion and Movement  Notes PDF at the end of the post.

Locomotion and Movement NEET Notes

Locomotion and Movement

Movement is the characteristic feature of the living organisms. It is defined as the change is body orientation, change in position, either of some part of the body or of the whole organism. When the movement results in displacement of the organism, it is called the locomotion. An organism shows the locomotion for the following reasons:

  • Search for food
  • Search for shelter
  • Mating
  • Escape from predator

Walking, running, swimming, climbing, flying etc. are the forms of locomotion. The organs specified for the locomotion need not be different from those involved in the movement. For example, the tentacles in jelly-fishes are used in capture of prey and locomotion, the cilia in Paramecium gather the food and also perform locomotion and the forelimbs and hindlimbs in humans perform the locomotion as well as the movements.

Types of Movements

There are following three types of movements:

MOVEMENT

DESCRIPTION

EXAMPLES

Amoeboid or Pseudopodal Movement

A crawling type of movement that occurs due to the emergence of finger-like projections called the pseudopodia.

It occurs in Amoeba for phagocytosis. It is shown by the leucocytes in blood and the microfilaments.

Ciliary Movement

Cilia are the tiny hair-like projections, present all over the body surface of an organism. They exhibit coordinated beatings that result in movement, called ciliary movement.

Shown by the internal organs that are lined with the ciliated epithelium. Movement of the ovum across the fallopian tube, elimination of the dust particles in trachea etc.

Muscular Movement

This type of movement occurs due to contraction of the contractile proteins within the muscles. It occurs in response to the nerve impulse.

Majority of the movements, including, swallowing, peristalsis, contraction of blood vessels etc.

Muscles

The muscular tissue is mesodermal in origin. It is made up of the cells called muscle fibers. These constitute around 40% to 50% of the human body weight. These show the following types of features:

  1. Excitability: The muscles are capable of responding to the nerve impulse, that is, they are capable of depolarising and polarising their membranes and transfer the potential difference across the membrane to the sarcoplasmic reticulum.
  2. Contractility: While showing excitability, the muscles respond by contraction along the long axis. This property is called contractility.
  3. Elasticity: The property of the muscles to regain the original shape after an event of the excitation and the contraction is called elasticity.
  4. Extensibility: The property to extension and stretching is called the extensibility.

Types of Muscles

There are the following three types of muscles:

1. Skeletal Muscles or the Striated Muscles:

These can be located below the skin, specifically, the skin covering the limbs. The skeletal muscles contract and bring about stimulation or inhibition of the movement.

Structure of the Skeletal Muscles

Each skeletal muscle can be seen covered with three layers of connective tissues that provide integrity to the structure and function of the muscles.

  1. The outer most layer of dense irregular connective tissue is called the epimysium. It provides structural separation to the muscles from other tissues.
  2. Within the epimysium, many bundles of muscles called fascicles are arranged. These fascicles are covered with another layer of connective tissue called perimysium.
  3. Within the fascicles, the muscle fibers are arranged and are covered with the third layer of connective tissue called the endomysium.
  4. The muscle fiber represents the individual cell of the muscular tissue, surrounded by the plasma membrane called the sarcolemma. The cytoplasm of the muscle fiber is called sarcoplasm and it contains sarcoplasmic reticulum and special contractile proteins arranged as myofibrils.
  5. These are multi-nucleated and appear striated.
  6. These are innervated by the motor neurons of the voluntary nervous system.

2. Cardiac Muscles:

These are exclusively located in the heart. These are also striated but are not under voluntary control. These are uninucleate. These are branched and their branches are connected via the intercalated discs. These intercalated discs have gap-junctions due to which a coordinated contraction can be achieved.

3. Smooth Muscles or Visceral Muscles:

These are unstriated in appearance. These are associated with the visceral organs like stomach, urinary bladder etc., so they are also not under the voluntary control. These are spindle-shaped, uninucleate, and are innervated by the autonomic nervous system.

Structure of the Contractile Proteins

The functional unit of the skeletal muscles is called the sarcomere, due to which they appear striated. Each sarcomere shows the proper arrangement of the myofilaments made up of contractile proteins called the actin and the myosin. Within each sarcomere, the following types of protein filaments are seen:

(a) The Thin Filament:

It is made up of the actin and the associated proteins called troponin and tropomyosin. Actin is a globular protein. Two filaments helically wound around each other form the thin filament. Two filaments of the tropomyosin are also placed along the actin filaments throughout their length. The troponin is a complex protein which appears distributed across the length of the thin filament. When at rest, the troponin proteins mask the active myosin binding site on the actin filament. Troponin has the binding sites for the Ca++ ions.

(b) The Thick Filament:

It is made up of the myosin protein that shows the following structural details:

  1. Head: The short arm called the heavy meromyosin represents the head. It shows ATPase activity and binding site for the actin.
  2. Tail: It is the light meromyosin and controls the contraction.

Mechanism of the Muscle Contraction

The muscle contraction is the functionality of the sarcomere. Following is the structure of the sarcomere:

  1. Each sarcomere shows light bands and heavy bands. The light bands are called I-bands and are made up of thin filaments. The heavy bands are called the A-bands and are made up of thick filaments.
  2. Each sarcomere lies within two Z-lines to which the thin filaments are anchored.
  3. Within A-band, there is H-zone which represents only the thick filaments at rest. The M-line holds the thick filaments together.

Sliding Filament Theory for Muscle Contraction

This theory states that the contraction of the muscles occurs when the thick and the thin filaments slide past each other due to the formation of the cross-bridges and this sliding movement reduces the length of the sarcomere, thereby contracting the muscles. This theory was put forward by Andrew Huxley and Niedergerke. The muscle contraction occurs in the following steps as per the sliding filament theory:

  1. The axons of the motor neuron from the voluntary nervous system synapse with the muscles at the neuromuscular junction or the end-plate. Upon receiving the stimulus from the sensory neurons, these release the acetylcholine that binds to the receptors on the muscles and depolarises the sarcolemma.
  2. The sarcolemma shows special T-shaped proteins. These proteins allow the spread of the depolarization to the membrane of the sarcoplasmic reticulum.
  3. The Ca++ are released from the sarcoplasmic reticulum and bind to the troponin complex of the thin filaments.
  4. This binding changes the conformation of the troponin, which in turn rotates the tropomyosin filaments and the myosin binding site of the actin filament is exposed.
  5. When at rest, the myosin is bound with ATP. As soon as the myosin binding site of the actin is exposed, the ATPase of the head of the myosin hydrolyzes the ATP into ADP and iP, the energy so released is used in forming the cross-bridges between the actin and the myosin.
  6. The cross-bridge formation results in pulling of the thin filaments towards the thick filament and the distance between the two successive Z-lines is reduced.
  7. The shortening of the distance between the Z-lines shorten the sarcomere and the muscle contraction is said to have taken place. This is called the power-stroke and involves the movement of the thin filament.
  8. The myosin head continues binding with the actin filament until the ATP binds with another site on the myosin head. This binding of ATP detaches the myosin head from the actin. But soon, this ATP is hydrolyzed and the power-stroke is generated once again.
  9. Thus, as long as the ATP continues to bind and hydrolyze, and the myosin binding sites on the actin are exposed, the muscle contraction will continue.

Relaxation of Muscles

It occurs when the action potential terminates at the motor neurons and so, the Ca++ ions are taken back in the sarcoplasmic reticulum. The myosin binding sites are masked with tropomyosin and cross-bridges are broken.

 Locomotion and Movement Notes for NEET Part 1 Download PDF 

Locomotion and Movement Notes for NEET (Part 2)

Introduction

The movement of the body parts or the change in position of the whole organism is supported and executed with the help of the skeleton. In the majority of the non-chordates, either the hemocoel or the exoskeleton provides the necessary supports. In human, the bony endoskeleton is responsible for the movement and locomotion. Apart from this, the skeleton serves the following functions:

  • Supports the body
  • Protects the internal organs
  • Produces the blood cells
  • Stores the mineral ions

Bone also called the osseous tissue, is the hard and specialized connective tissue in the body. It is mesodermal in origin. The movements of the bones are facilitated as they are connected with the skeletal muscles and are supported by the cartilage. Cartilage is the flexible connective tissue that serves to provide smooth surfaces for the movements.

Skeletal System in Humans

The human skeletal system is made up of bones, cartilage, and ligaments that join the bones. In an adult, there are 206 bones. A younger individual would have more bones as compared to an older individual. The basic functionality of the skeletal system is to provide the ability to move and locomote. The lower part of the system is specialized for the locomotion. The upper part of the skeleton can bring about a range of movements, for example, lifting, carrying etc.

The skeletal system can be divided into two sub-types:

  1. The Axial System:

It shapes the vertical and the central axis of the body and consists of the bones of the head, neck, chest and back. Altogether there are 80 bones in this system.

 

  1. The Appendicular System:

It consists of the bones of the upper limbs, lower limbs and the bones connecting limbs to the axial skeleton. There are 126 bones in this system.

Axial Skeletal System

  1. Skull

It consists of 22 bones joined via synarthrodial (immovable) joints. Only the 22nd bone called the mandibles are movable. The skull is studied under the following heads:

  1. Neurocranium

It is present around the brain. The following bones can be located in this part:

Occipital Bone

It is the base of the skull. It has an opening called foramen magnum through which spinal cord passes

Two Temporal Bones

These form the part of the base and the sides of the skull. These are lateral to the temporal brain.

Two Parietal Bones

These form the upper part and the upper sides of the skull.

Sphenoid Bone

It is located in the mid of the skull

Ethmoid Bone

It acts as a barrier between the nasal cavity and brain.

Frontal Bone

It forms the front part of the skull. The squamous part forms the forehead, Orbital part forms the orbit of eyes, the nasal part forms the roof of the nose.

 

  1. Viscerocranium:

It has the following Facial bones:

1The vomer
2Two Nasal Conchae
3Two Nasal Bones
4Two Maxilla: Upper Jaw
5The Mandible: Lower Jaw
6Two Palatine Bones
7Two Zygomatic Bones: Cheek Bones
8Two Lacrimal Bones

Hyoid Bone: It is located at the base of the buccal cavity. It is not connected with any bone. 

  1. Vertebral Column:

The backbone is located dorsally. It is made up of 26 vertebrae. The atlas is the first vertebrae. It serves to protect the spinal cord and providing bending ability. It can be divided into the following regions:

  1. Seven Cervical vertebrae
  2. Twelve Lumbar vertebrae
  3. Five Sacral vertebrae
  4. One Coccygeal vertebra
  5. Ribs:

These are 24 in number forming 12 pairs and protect the organs in the thoracic cavity. The first seven pairs are called true ribs as they are attached with the sternum ventrally. The 8th, 9th and 10th pairs do not attach to the sternum, they attach to the 7th pair. So, these are called the false ribs. The 11th and 12th pairs remain free and are called floating ribs. These provide a protective bony cover to the heart.

Appendicular Skeletal System

It consists of the forelimb and the hindlimb, each containing 30 bones. The pectoral and the pelvic girdle form the connection between the limbs and the axial skeleton. These are discussed below:

  1. Pectoral Girdle:

It attaches forelimbs to the upper skeleton. It has the following bones:

Scapula or the Shoulder Blade

It forms the posterior of the shoulders. It is a flat bone with a triangular shape

Clavicle or Collar Bone

These are horizontal long bones.

 

  1. Pelvic Girdle:

It is made up of hip bone or the coxal bone that attaches with the hindlimbs and the sacral vertebrae of the backbone. The coxal bones are immobile and serve to bear the weight. Each coxal bone is formed by the fusion of upper ilium bone, lower ischium bone and the inner pubis bone.

Limb Bones

  1. Forelimbs:

There are the following regions with their corresponding bones:

REGION

BONES

Arm (between shoulder and elbow joint)

Humerus

Forearm (between elbow joint and wrist joint)

Ulna (located medially) and Radius (Located laterally)

Hand

Carpal Bones (base of hand)

Metacarpal Bones (palm)

Phalanx Bones (fingers and thumbs)

 

  1. Hindlimbs:

There are the following regions with their corresponding bones:

REGION

BONES

Thigh (between hip joint and the knee joint)

Femur

Patella or knee-cap

Leg (between knee joint and the ankle joint)

Tibia (located medially)

Fibula (located laterally)

Foot

Tarsals (distal ankle)

Metatarsals (midfoot)

Phalanx (Toes)

Joints

Joints are the points or the regions where the connection between the two bones or bone and cartilage occurs. The joints can be classified as follows:

Fibrous or Immovable Joints

The bones are bound with dense fibrous connective tissues, so the movement is not possible. For example, sutures between the bones of skull.

Cartilaginous or Slightly Movable Joints

The ends of the bones have hyaline cartilage, so a slight degree of movement is possible. For example, joints between the vertebrae in vertebral column.

Synovial or Freely Movable Joints

These joints have a synovial cavity (fluid-filled) surrounded by the articular capsule.

Types of Synovial Joints:

  1. Ball and Socket joint: One bone forms a ball-like structure into which the socket-like structure of the other bone is fixed. For example, shoulder joint and hip joint.
  2. Hinge joint: One bone form convex end that articulates with the concave end of the other bone. Movement is possible in one plane only. For example, elbow joint, knee joint etc.
  3. Pivot Joint: It allows the rotatory movements. For example, radioulnar
  4. Gliding Joint: Bones are firmly attached via ligaments so limited movement occurs in all directions. For example, joints of carpals and tarsals.
  5. Saddle Joint: It is a biaxial joint. It resembles a ball and socket joint. For example, the joint between thumb and carpals.

Functions of Joints:

  1. Provide the ability to perform the movements.
  2. Provide flexibility.
  3. Provide a lever system to the body along with the muscles and the bones.

Lever System:

The bones, muscles, and ligaments form the lever system because they allow the varying degrees of the movements in the human body.

  1. The first-class lever is formed between the skull (weight) and the atlas. The fulcrum is located between the weight and the force.
  2. The second-class lever is formed between the lower leg (tibia and fibula) and tarsals. The weight is located between the axis and the force.
  3. The third-class lever is formed by the elbow joint. The force is located between the axis and the weight.

Disorders of the Muscular and the Skeletal System:

  1. Muscular Dystrophy: It is a congenital disorder that results in muscular wasting and deterioration. The patients do not have a long life-span.
  2. Tetany: Low level of the calcium ions resulting in the frequent and painful muscle contractions, also called tremors. It is associated with the hyposecretion of the parathyroid hormone.
  3. Arthritis: It is an autoimmune disorder, sometimes can be due to the pathogenic infection that causes the inflammation of the joints.
    • Rheumatoid Arthritis: It is the inflammation of the synovial joint membrane.
    • Osteoarthritis: It is the degenerative disease of the articular capsule of the synovial joints.
    • Gout Arthritis: Accumulation of the uric acid crystals in the joints.
    • Infectious Arthritis: This is caused due to pathogenic infections.
  4. Osteoporosis: The excessive resorption of the calcium by the bones makes them brittle and degenerate the bony tissue. It enhances fracture incidences.
  5. Osteomalacia or Rickets: It is a degenerative disease of bones in children, specifically caused due to lack of vitamin D.

Locomotion and Movement Notes for NEET (Part 2) Download PDF

Axial and Appendicular Skeleton 

Appendicular Skeleton

Muscle Contraction Mechanism

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