B3.3 Flashcards
Muscle and Motility
Sliding Filament Theory
Muslce Fibres?
- Each individual long cylindrical msucle cell, that clusters into rings to make up muscles.
- Multinucleate, covered in an extra layer of tissue.
- On top of them – many mitochondira & speical endoplasmic reticulum for calcium transport.
Sliding Filament Theory
Myofibrils?
- Protein filaments running parrallel throughout the cell, located in each muscile fibre in numerous amounts.
- On their outlayer is nuclei & mitochonria
Sliding Filament Theory
Sacromere?
- A functional contracting unit that makes up myofirbil.
- All sacromeres in a muscle contract at the same time –> contracts muscle tissue.
- Classified as Z-line to Z-line with the actin and myosin proteins between.
Sliding Filament Theory
Myosin?
- The thick protein that sits in between actin filaments.
- Surrounded by 6 actin filaments.
- Filaments have ‘heads’/ extentions that stick up and form attatchments or cross bridges with actin.
- Breaking & reforming of these cross bridges in the basis of muscle contraction.
Sliding Filament Theory
Actin?
- The thinner protein (or filament).
- Attatches to a side protein called a Z-line, also able to form cross bridges with the myosin –> used to pull Z-linse close together to cause a muscle contracion.
Sliding Filament Theory
Z-disc?
- A vertical protein that actin attatches to.
- There’s two Z-discs for each sacromere & when contracion occurs the Z-lines are pulled together –> lines provide boundary for each sacromere.
Sliding Filament Theory
Titin?
- The largest polypeptide out of the 34000 amino acids.
- Highly elastic & functions as the sacromere spring.
- Connects the myosin filaments to the Z-disc (don’t directly bind)
- When muscles relax they lengthen –> stretches titin, storing potential energy at the same time.
- When muscles contract, energy is stored & titin condenses pulling Z-lines in.
Sliding Filament Theory
Light & Dark Bands of Sacromere?
- Myosin is thicker protein - the centre region of sacromere thus appears darker on an electron micrograph.
- Therefore, you can determine whether a muscle is relaxed or contracted based on how wide the dark band it.
Sliding Filament Theory
Role of ATP in Sliding Filaments?
Contraction of muscles works by myosin pullin the actin filaments in –> Requiring ATP.
- ATP is hydrolysed into ADP & P causing a change in the position of the myosin head, allowing it to bind to actin.
- Myosin then releases ADP & P, pulling actin ahead (powerstroke).
- A new ATP binds to the head, releasing the head, which it can then hydrolyse and repeat the process.
Sliding Filament Theory
Titin and Muscle Relaxation
- When muscles contract the protein titin shortens & relaxes, allowing Z-disc to be pulled inwards.
- To relax, titin needs to be pulled back out to allow the lengthening of the sacromere & to store potential energy to aid in next contraction.
- The muscle itself can’t provide energy for that relaxation.
- Thus it relies on another muscle to contract –> that contraction allows Titin to lengthen.
- All muscles need a paired muscle to faciliate the relaxation of the mucle (ANTGONISTIC PAIRS)
- EXAMPLE: INNER Intercostel and EXTERNAL Intercostel muscles
Antagonistic Pairs in Muscles
Tendons?
- Connective tissue that attach a muscle to two bones, one at each end of the tendon.
- One of the bones acts as an anchor, the other is moved by the muscle contraction.
- They’re strong but flexible tissue (mainly comprised of collagen)
Antagonistic Pairs in Muscles
Nueromuscular Junctions?
- The space between the last moton nueron and the muscle fibres.
- Movement of muscles relies on messages sent from brain telling them to contract.
- Nuerotransmitter acetycholine is released into a version of synapse.
- The muscle fibres then recieve the message from acetycholine and initiate contraction.
Antagonistic Pairs in Muscles
Motor Nuerons?
- A specialized nerve cell that function to transfer messages from the brain to the muscle.
- Some are located in the brain to collect messages, most in continuous lines in nerves, connecting the brain & muscle & the terminal motor nueron in a nerve end at the muscle.
Antagonistic Pairs in Muscles
Motor Units?
- A number/cluster of muscle fibres attatched to and controlled by a single motor nueron.
- Vary is size, smaller movements require smaller motor units.
Antagonistic Pairs in Muscles
Levers?
- A rod able to rotate on a fixed point called the fulcrum.
- Bones act as the levers, muscles pull on them which moves bones on their fulcrum to easily craete movement of the body part.
Antagonistic Pairs in Muscles
Fulcrum?
- The fixed point that a lever can pivot on, acting as a hinge – allows movement on either side of it.
- Our joints (where 2 bones meet) act as the fulcrum, which bones pivot on.
- Type of movement depends on location of fulcrum, so joints determine range of motion.
Antagonistic Pairs in Muscles
Synovial Joint
Joins: Any place where two bones connect.
* Some joints aren’t adapted for movement.
* Joints that function as fulcrums to create movement however have special adapatiation to faciliate this –> freely moveable joints –> Synovial joints
* Synovial fluid lubricates the joint to educe friction.
Antagonistic Pairs in Muscles
Cartilage
- Smooth protective connective tissue that lines both bones in a joint.
- Ensure if bones collide, there’s no bone-to-bone contect.
- Acts as a cushion that reduces friction and absorbs shock.
Antagonistic Pairs in Muscles
Ligaments?
- Connective tissue that attach two bones at a joint.
- Tough connective tissue, but connect bone to bone instead of muscle to bone.
- They have greater elasticity than tendons due to need to retain connection as bones move.
Antagonistic Pairs in Muscles
Structure of a Motor Unit?
- Consists of a motor nueron, bringing the chemical messages, & many muscle fibres that recieve the message from that motor nueron.
- A single muscle fibre often has multiple motor nuerons attached to it – allows more/less movement of same muscle by adjusting no. firing nuerons.
Antagonistic Pairs in Muscles
Endo vs Exo Skeletons.
Exo: On the outside of the body, made of tough plates of chitin, use muscle to move skeleton but the muscles are attatched on the inside of skeleton. Muscles used to move chitin plates in insects.
Endo: Internal, under other body tissues, made of bones.
Antagonistic Pairs in Muscles
Movement of Skeletons by Muscle
- A muscle is attached to 2 parts of the skeleton, with one steady acting as the anchor.
- Muscle uses force, pulls the other one, cuasing bone to move.
- The fixed bone acts as the fulcrum – the other bone (lever) pivots on its point.
Antagonistic Pairs in Muscles
Range of Motion in a Joint
- Structure of joint determines range of motion for those bones.
- Hip & shoulder – ball and socket, faciliating wider range of movement.
- Elbow and knee – flexation & extensioin.
Adapatations for Movement
What does Sessile Mean?
Organisms not able to move from place to place but able to alter their body form in some way in response to an envrionmental stimuli (a form of movement).
EG: Venus Fly Trap
Adapatations for Movement
Motile?
Organisms with adaptationis allowing them to move within their habitats.
EG: Sloth, Cheetah.
Adapatations for Movement
Streamlining?
(Streamlined bodies) A body shape designed to minimize resistance when moving through a fluid by having a smooth, curved, teardrop shaped form.
Common adapation (ducks) for aquatic animals to overcome waters viscovity.
Adapatations for Movement
Fluke?
An adapated tail allowing for and up and down motion to help propel them through water. (whale’s tail)
Adapatations for Movement
Reasons for Movement? (4)
- Foraging for food
- Escaping danger
- Searching for a mate
- Migration
Adapatations for Movement
Adapatations for Swimming?
- Streamlined Body
- Loss of body hair
- Fluke for a tail
- Sealable blowhole for gas exchange
