11.2 Movement Flashcards
What systems control movement?
skeletal system
muscular system
nervous system
How does the skeletal system help coordinate movement?
consists of bones that act as levers and provide a structure for the muscles to pull
How does the muscular system help coordinate movement?
muscles deliver the force required to move one bone in relation to another
How does the nervous system help coordinate movement?
delivers signals to the muscles which cause them to contract and create movement
What are skeletons?
Skeletons are a rigid framework that function to provide support and protection for body organs
What two types of skeleton are there? (dependent on location)
Skeletons can be internal (endoskeletons) or external (exoskeletons) depending on the organism
What is the difference between endo and exo skeletons?
Endoskeletons typically consist of numerous bones, while exoskeletons are comprised of connected segments
What connects to skeletons?
Skeletons provide a surface for muscle attachment and thus facilitate the movement of an organism
What do bones and exoskeletons act as?
Bones and exoskeletons act as levers, moving in response to muscular contraction
What are bones connected to other bones by?
Bones are connected to other bones by ligaments
What are muscles connected to bones by?
bones are connected to muscles by tendons
What are synovial joints?
Synovial joints are capsules that surround the articulating surfaces of two bones (i.e. where the bones connect)
What is the role of joints?
Joints function to maintain structural stability by allowing certain movements but not others
What are the 3 components of synovial joints?
joint capsule
cartilage
synovial fluid
What is the role of joint capsules in synovial joints?
Seals the joint space and provides stability by restricting the range of possible movements
What is the role of cartilage in synovial joints?
Lines the bone surface to facilitate smoother movement, as well as absorbing shock and distributing load
What is the role of synovial fluid in synovial joints?
Provides oxygen and nutrition to the cartilage, as well as lubrication (reduces friction)
What are the 6 types of joint?
List in order of ranges or movement/mobility
Plane joints (least mobility), hinge joints, pivot joints, condyloid joints, saddle joints, ball and socket joints (most mobility)
What type of joint is the human elbow?
The human elbow joint is an example of a hinge joint that is located between the humerus and radius / ulna
What type of movement is the elbow joint capable of?
It is capable of angular movement in one direction (i.e. flexion and extension only)
A small amount of rotation may be possible, but excessive multiaxial movement will cause injury
What are the 3 bones in the elbow joint?
humerus
radius
ulna
What is the function of the humerus?
anchors muscle (muscle origin)
What is the role of the radius?
acts as a forearm lever for biceps
What is the role of the ulna?
acts as a forearm lever for triceps
What are the 2 muscles involved in the elbow joint?
biceps
triceps
What is the role of the biceps?
bends the forearm (flexion)
What is the role of triceps?
straightens the forearm (extension)
How do muscles provide movement? (breif)
muscles connect to bones (via tendons) and contract to provide the force required to produce movement
Where do muscles connect to? 2 points?
The muscle connects a static bone (point of origin) to a moving bone (point of insertion)
What do skeletal muscles exist in?
Skeletal muscles exist in antagonistic pairs (when one contracts, the other relaxes) to enable opposing movements
What are examples of movements by antagonistic pairs?
Opposing movements may include: flexion vs extension, abduction vs adduction, protraction vs retraction, etc.
What types of specialised muscles do insects have? Give an example.
Many types of insects (including grasshoppers and praying mantises) have hind legs that are specialised for jumping
How is the hind leg of an insect divided?
The jointed exoskeleton of the hind leg is divided into three parts: femur (upper leg), tibia (middle leg) and tarsus (lower leg)
How are the femur and tibia connected in an insect?
The femur and tibia are connected by two antagonistic muscles: flexor tibiae muscle and extensor tibiae muscle
How do the tibia and femur interact in an insect hind leg?
When the flexor muscle contracts, the extensor muscle relaxes and the tibia and femur are brought closer together
What does the relaxation of the extensor muscles and the contraction of the flexor muscle cause in insects?
This retracts the hind quarters in preparation for pushing off the ground
How does an insect prepare to jump
When the extensor muscle contracts, the flexor muscle relaxes and the tibia is pushed away from the femur
This extends the hindquarters and causes the insect to jump
What do skeletal muscles consist of?
Skeletal muscles consist of tightly packaged muscular bundles (fascicles) surrounded by connective tissue (perimysium)
What does each muscular bundle contain?
Each bundle contains multiple muscle fibres, which are formed when individual muscle cells fuse together
What do muscle fibres contain?
Muscle fibres contain tubular myofibrils that run the length of the fibre and are responsible for muscular contraction
What can myofibrils be divided into?
The myofibrils can be divided into repeating sections called sarcomeres, each of which represent a single contractile unit
List the organisation of skeletal muscles?
skeletal muscle muscular bundle (fascicles) muscle fibres myofibrils sacromeres
What 5 specialised features does each individual muscle fibre have to facilitate muscle contraction?
They are Multinucleate They have a large number of Mitochondria They have a specialised Endoplasmic reticulum They contain tubular Myofibrils Sarcolemma
MMEMS
How are muscle cells multinucleate?
fibres form from the fusion of individual muscle cells and hence have many nuclei
How does having a large number of mitochondria aid in muscle contraction?
They have a large number of mitochondria (muscle contraction requires ATP hydrolysis)q
What is the specialised ER of muscles called and what is its role?
They have a specialised endoplasmic reticulum (it is called the sarcoplasmic reticulum and stores calcium ions)
What are tubular myofibrils composed of?
They contain tubular myofibrils made up of two different myofilaments – thin filament (actin) and thick filament (myosin)
What is the sarcolemma? (structure)
The continuous membrane surrounding the muscle fibre is called the sarcolemma and contains invaginations called T tubules
What do myofibrils consist of?
Myofibrils consist of repeating contractile units called sarcomeres, which are made of two protein myofilaments
What is the “thick” filament and its structure?
The thick filament (myosin) contains small protruding heads which bind to regions of the thin filament (actin)
What causes the lengthening and shortening of the sarcomere?
Movement of these two filaments relative to one another causes the lengthening and shortening of the sarcomere
What is each individual sarcomere flanked by?
Each individual sarcomere is flanked by dense protein discs called Z lines, which hold the myofilaments in place
What is the role of the z discs?
The actin filaments radiate out from the Z discs and help to anchor the central myosin filaments in place
What causes skeletal muscle fibres to look striated?
The recurring sarcomeres produce a striated (striped) pattern along the length of the skeletal muscle fibres
What does the A band look like?
The centre of the sarcomere appears darker due to the overlap of both actin and myosin filaments (A band)
What does the I band look like?
The peripheries of the sarcomere appear lighter as only actin is present in this region (I band)
What does the H zone look like?
The dark A band may also contain a slightly lighter central region where only the myosin is present (H zone)
What 3 things are key to remember when drawing a diagram of the sarcomere?
The myosin filaments are the thick filaments and should be represented as being thicker than the actin filaments
The myosin filaments should include protruding heads (myosin heads form cross-bridge attachments with actin)
The striated banding pattern should be identified (A band = dark region ; I band = light region)
What are the 4 main steps of muscle contraction?
Depolarisation and calcium ion release
Actin and myosin cross-bridge formation
Sliding mechanism of actin and myosin filaments
Sarcomere shortening (muscle contraction)
- What is the first step of depolarization and calcium ion release?
An action potential from a motor neuron triggers the release of acetylcholine into the motor end plate
- What is the role of acetylcholine?
Acetylcholine initiates depolarization within the sarcolemma, which is spread through the muscle fibre via T tubules
- What is the role of depolarisation?
Depolarisation causes the sarcoplasmic reticulum to release stores of calcium ions (Ca2+)
- What is the role of calcium ions?
Calcium ions play a pivotal role in initiating muscular contractions
2.5. Why can binding not occur straight away?
On actin, the binding sites for the myosin heads are covered by a blocking complex (troponin and tropomyosin)
2.6. How are the myosin heads allowed to bind?
Calcium ions bind to troponin and reconfigure the complex, exposing the binding sites for the myosin heads
2.7 What happens when the actin is exposed?
The myosin heads then form a cross-bridge with the actin filaments
3.8 What causes myosin to detach?
ATP binds to the myosin head, breaking the cross-bridge between actin and myosin
3.9 What does ATP hydrolysis cause?
ATP hydrolysis (releasing ADP and inorganic phosphate) causes the myosin heads to change position and swivel, moving them towards the next actin binding site
3.10 What happens once myosin has swivelled/changed shape?
The myosin heads bind to the new actin sites and return to their original conformation
3.11 What causes the movement?
This reorientation drags the actin along the myosin in a sliding mechanism (a power stroke)
4.12 What does the cycle cause?
The repeated reorientation of the myosin heads drags the actin filaments along the length of the myosin
4.13 what change in appearance occurs to the sarcomeres?
As actin filaments are anchored to Z lines, the dragging of actin pulls the Z lines closer together, shortening the sarcomere
4.14 what, overall, causes the muscle to contract?
As the individual sarcomeres become shorter in length, the muscle fibres as a whole contracts
What change in appearance occurs to I bands after contraction?
When muscle fibres contract, actin filaments slide along the myosin, reducing the length of the lighter I bands
What change in appearance occurs to H zone after contraction?
The movement of the actin filaments also reduces the width of the H zone
What change in appearance occurs to the A bands?
the length of A bands do not change
What type of protein is actin?
These are globular protein molecules
What form does actin take in sarcomeres? (structure)
Many actin molecules link together to form a chain
Two actin chains twist together to form one thin filament
What surrounds the actin filaments?
A fibrous protein known as tropomyosin is twisted around the two actin chains
Another protein known as troponin is attached to the actin chains at regular intervals
What type of protein is myosin?
These are fibrous protein molecules with a globular head
What is the role of the fibrous part of myosin?
The fibrous part of the myosin molecule anchors the molecule into the thick filament
What is the structure of myosin?
In the thick filament, many myosin molecules lie next to each other with their globular heads all pointing away from the M line
What enzyme is involved in muscle contraction?
The enzyme ATP hydrolase hydrolyses ATP into ADP and inorganic phosphate which causes the myosin heads to move back to their original positions
This is known as cocking of the myosin head or the recovery stroke
What happens once the muscle relaxes?
When the motor neurone stops sending impulses to the muscle fibre, calcium ions are actively pumped back into the sarcoplasmic reticulum and the tropomyosin moves back to cover the binding sites on the actin
The muscle is now relaxed
What is the M-line?
attachment for myosin filaments
