B3.3 muscles and motility

Question 1

2 ways in which organisms move

Answer 1

In every organism there is internal movement.

1. motile organisms move their body from one place to another= locomotion
2. sessile organisms= remain in fixed positions (most plants)

Question 2

tropism

Answer 2

movement of an organism towards and external stimulus

Question 3

structure of muscle

Answer 3

-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

Question 4

structure of a sarcomere

Answer 4

-The endings are Z discs which are attached to thin protein filament (actin)
-Actin filaments overlap with thick myosin filaments

Question 5

sliding filament theory

Answer 5

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.

Question 6

contracted form of sarcomere

Answer 6

-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

Question 7

Sarcoplasm and sarcoplastic reticulum

Answer 7

Sarcoplasm= cytoplasm of muscle fibers
Sarcoplasmic reticulum = modified ER that stores calcium ions involved in muscle contraction

Question 8

Role of titin

Answer 8

-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

Question 9

Antagonistic muscles

Answer 9

muscles contract to move bones
Skeletal muscles exist in antagonistic pairs. Whilst 1 contracts and shortens the other relaxes and extends

Question 10

How skeletal muscles contract

Answer 10

-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

Question 11

motor units

Answer 11

-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

Question 12

Endoskeleton and exoskeleton

Answer 12

Endoskeleton= internal skeleton
Exoskeleton= external skeleton made of chitin (arthropods)

Question 13

joints

Answer 13

The junctions between bones

Question 14

tendons and ligaments

Answer 14

tendons= connective tissue which anchors bone to muscle
ligaments= connective tissue which anchors bones together

Question 15

bones as levers

Answer 15

Bones act as levers as muscles contract
Bone rotates around a fixed position (fulcrum)

Question 16

Anchoring points

Answer 16

Origin; fixed point where muscle attaches to bone but doesnt move
Insertation; point where muscle attaches to bone that moves, muscle contracts

Question 17

Synovial joints

Answer 17

Joints which connect 2 or more bones with capsule which contains synovial fluid (elbow, knee, hips)

Question 18

Structure of hip bone

Answer 18

=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

Question 19

Goniometer

Answer 19

Measures the range of motion of a joint

Question 20

Internal intercostal muscles and external intercostal muscles as antagonistic muscles

Answer 20

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

Question 21

Need for locomotion

Answer 21

-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)
-

Question 22

Locomotion

Answer 22

Ability to move from place to place

Question 23

Swimming adaptations in marine mammals

Answer 23

• 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