Muscles and mobility Flashcards
Types of movement
- Internal (peristalsis, breathing movements, cytoplasmic movements) – sessile organisms
- Whole body movement (locomotion)
Importance of movement for animals
foraging for food, escaping danger, finding a mate, migration
How are marine mammals adapted for swimming (water viscous)?
How are adapted for aqueous life generally?
Adaptations for locomotion include flippers (steering), tail flukes (increase thrust), dorsal fin (stability) and blubber (buoyancy)
1. Streamlining – animals shaped to minimize drag and resistance to motion by being widest near the front, having flippers, flukes and dorsal fin, having a smooth body surface due to even blubber distribution and absence of hind limbs (no hair to reduce friction)
2. Adaptations for periodic breathing between dives – airways can be closed during dives using nostrils or blowhole and they are reinforced with rings of cartilage pr smooth muscle to ensure ventilation can restart quickly after a dive
Functions of a skeleton
- Providing support
- Protection (exo.)
- Metabolic function (blood cell creation, storing vitamins and minerals)
- Anchorage for muscles and levers
Muscle attachment points – biceps and masseter muscle example
leg bones and arm bones
Origin/tip is where the muscle starts
Insertion is where it ends – it is located on the bone which the muscle moves by contracting or relaxing
Fulcrum or pivot point is the fixed point of a lever (joint)
biceps: origin on the humerus bone and insertion on the radius. Pivot point is the elbow
masseter muscle: origin on cheek bone and insertion on jawbone
Femur: tibia and fibula, humerus: radius and ulna
Anatomy of the muscle-skeletal system and the structures’ functions:
1) Skeletal/striated muscle – elongated, spindle-shaped; surrounded by a membrane which forms tendons at its ends
2) Tendons – attach bones to muscles, (relatively) non-elastic structure which transmits the contractile force of muscles to the bone
3) Synovial fluid – fluid inside the synovial joint (self-lubricating joints) that prevents friction by being incompressible – the fluid contains nutrients and supplies them to the cartilage as well as receives waste products from it because the cartilage doesn’t have its own blood supply (the fluid has to be regularly exchanged)
4) Synovial membrane – constantly produces new and removes old synovial fluid
5) Capsula – seals the joint
6) Cartilage – prevents friction and damaging of bone tissue
7) Ligament – connects and stabilizes bones
Types of joints:
- Ball and socket (3 planes of movement: protraction/retraction, abduction/adduction, rotation)
- Hinge joint (one plane of movement: flexion/extension)
What is used to measure ethe rage of movement at the joint?
Goniometer
Muscle structure (decreasing order)
Muscles > muscle bundles > muscle cells (myocytes) > myofibrils (parallel, cylindrical)
Myocyte components
sarcolemma (membrane), sarcoplasm (multinucleated cytoplasm due to fusion of several embryonic muscle cells), mitochondria, and sarcoplasmic reticulum (modified ER that wraps around myofibrils)
what is a sarcomere – arrangement of protein filaments in the sarcomere
basic contractile units of a myocyte divided by Z-discs (optical illusion) composed of two types of protein filaments called actin and myosin that are arranged in a regular pattern – these filaments are responsible for muscular contraction – each myosin (thicker) is surrounded by six actins (thinner)
each sarcomere has a dark band in the middle and a light band at each end, where the dark band contains many parallel overlapping myosin filaments and the light bands contain only actin filaments, each attached to a Z-disc at one and overlapping with myosin filaments at the other end
Each sarcomere (light band) gets shorter when contracted and thus the whole muscle gets shorter
difference in actin and myosin arrangement and myocyte appearance in different muscles
arranged regularly in striated muscles and irregularly in smooth (don’t have that specific bending pattern and appearance) – unlike in skeletal muscles, myocardium myocytes branch out to ensure powerful and uniform heart contractions
Motor unit
one motor neuron plus all muscle fibers it stimulates – the number of motor units recruited is proportional to the relative force of muscle contraction
Explain the entire mechanism of muscle contraction
1) Nerve impulse arrives at the end of a motor neuron at the neuromuscular junction (synaptic cleft)
2) It is carried over to the myocyte by neurotransmitter acetylcholine
3) The nerve impulse causes sarcoplasmic reticulum to release Ca2+ ions into myofibrils
4) During relaxation, myosin head binding sites on actin were covered with tropomyosin and troponin complex but Ca2+ ions bind with the troponin and cause tropomyosin to shift and expose the binding sites to myosin heads
5) Myosin has lateral extensions called heads that can attach to binding sites on actin and they undergo a cycle of binding
6) With the binding sites exposed, myosin heads can attach and form a cross-bridge, beginning a contraction
7) Myosin head has different conformations based on how much energy it has -> low E = bent (muscle relaxed)
8) When it gains E by ATP hydrolysis, it straightens out to reach the myosin head bonding site
9) Once a cross-bridge is formed the P group and ADP detach from the head which causes another conformational change of the head so it pushes actin towards the center of the sarcomere
10) Once ATP joins again (another hydrolysis), head will detach and change back to its original conformation (E needed for relaxation too) – or if the impulse continues it will swivel to the next binding site, furthering the muscle contraction
11) As long as there is a nerve impulse, ATP and Ca2+ ions, the process of sliding filaments continues and results in muscle contraction
12) The small force exerted by each myosin head is multiplied up and muscles can exert very powerful forces
Rigor mortis
muscles are stiff the first few minutes after death due to lack of ATP needed for muscle relaxation
Titin – function?
An elastic (not contractile) protein in between six actin filaments and myosin which acts as a molecular spring. It is the largest protein in nature and the 3rd most abundant protein in muscle cells
1) Attaches myosin to the z-line
2) Prevents overstretching of muscle
3) Increases the F exerted by muscle contraction by storing potential E when stretched (relaxation) and releasing it when it recoils in contraction
