B3.3 muscles and motility Flashcards
2 ways in which organisms move
In every organism there is internal movement.
- motile organisms move their body from one place to another= locomotion
- sessile organisms= remain in fixed positions (most plants)
tropism
movement of an organism towards and external stimulus
structure of muscle
-skeletal muscles are composed of muscle fibres which are formed by the fusion of many cells (multinucleated atypical cells)
-each muscle fiber is composed of many protein filaments called myofibrils that run parallel to each other. It contains repeating units called sarcomeres
structure of a sarcomere
-The endings are Z discs which are attached to thin protein filament (actin)
-Actin filaments overlap with thick myosin filaments
sliding filament theory
When receptor sites on actin are exposed, myocin heads bind. Myosin head moves actin by rowing actions pulling actin towards center of sarcomere (M line)
ATP binds to myocin head causing separation from action filament.
ATP hydrolises once removed to move myocin head back. This can be done again.
contracted form of sarcomere
-myosin remains stationary while 2 sides of actin move towards the center of the sarcomere (M line)
-myosin has heads that interact with the actin causing Z lines to move closer to each other
Sarcoplasm and sarcoplastic reticulum
Sarcoplasm= cytoplasm of muscle fibers
Sarcoplasmic reticulum = modified ER that stores calcium ions involved in muscle contraction
Role of titin
-Titin is a long fibrous elastic protein that joins end of myosin filament to Z line and acts as a molecular spring
-helps sarcomeres recoil after stretching and prevents over stretching, aids contraction
Antagonistic muscles
muscles contract to move bones
Skeletal muscles exist in antagonistic pairs. Whilst 1 contracts and shortens the other relaxes and extends
How skeletal muscles contract
-contract under control of the nervous system
-requires electrical impulses which terminate at neuromuscular junctions
-in synapse, ACH is released which binds to protein receptors on sarcolema to stimulate contraction in tissue
-each muscle contraction varies with intensity depending on how many muscle fibers receive impulses
motor units
-each motor neuron has a set number of muscle fibers it controls called a motor unit
-This can vary from 1:10 to 1:200
Endoskeleton and exoskeleton
Endoskeleton= internal skeleton
Exoskeleton= external skeleton made of chitin (arthropods)
joints
The junctions between bones
tendons and ligaments
tendons= connective tissue which anchors bone to muscle
ligaments= connective tissue which anchors bones together
bones as levers
Bones act as levers as muscles contract
Bone rotates around a fixed position (fulcrum)
Anchoring points
Origin; fixed point where muscle attaches to bone but doesnt move
Insertation; point where muscle attaches to bone that moves, muscle contracts
Synovial joints
Joints which connect 2 or more bones with capsule which contains synovial fluid (elbow, knee, hips)
Structure of hip bone
=synovial ball and socket joint
-Head of femur forms a ball which fits into rounded pelvis bone
-Cartlidge covers both bones
-Incased in membrane that contains synovial fluid
-Hip joined by ligaments
Goniometer
Measures the range of motion of a joint
Internal intercostal muscles and external intercostal muscles as antagonistic muscles
Muscles change the shape of the rib cage
Ribs are the origin and insertion point and the spine the the fulcrum point.
During inhalation external intercostal muscles contract and the internal relax causing the rising of the rib cage
Need for locomotion
-foraging for food (honeybees)
-escaping danger (flying fish)
-searching for a mate (sea turtle)
-migration (some birds eg geese)
-dispersal (seeds with helicopter like features)
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Locomotion
Ability to move from place to place
Swimming adaptations in marine mammals
- streamlined body shape, no body hair
-modified pentadactyle limbs
-fluke or tail, maximising SA for efficient swimming
-modified airways, which allow for periodic breathing between dives
-blow holes which can prevent water entering whilst diving