B3.3 Muscle and motility Flashcards
What are sessile organisms?
These are organisms that cannot move from place to place, but are still able to alter their body form in response to environmental stimuli.
What are motile organisms?
These are organisms that have adaptations allowing movement within their habitat
Sessile organism example
Venus flytrap: this is a carnivorous plant native to the subtropical wetlands found in north + south carolina. This plant species lives in soils that are deficient in minerals, especially nitrogen. The plant’s traps ia a pair of leaves with short but sturdy trigger hairs. It waits for and insect to fly insides it’s paired leaves and trigger the hairs, once triggered both sides close, to prevent prey from escaping. The internal portion of these leaves then secretes enzymes to digest the trapped insect
Example of a motile organism
Brown-throated three-toed sloth: is motile but a very slow moving mammal. Sloths are arboreal (tree dwelling) and herbivorous. Their digestive process is slow, it takes them about a month for them to process an ingested leaf. Once a week the sloth will descend to the ground to use bathroom, leaving behind the equivalent of 1/3 of their body mass. They have 3 long toes, in combination with their bone structure and musculature are adapted to hanging from branches and moving using a pulling motions. These adaptations make movement on the ground almost impossible for a sloth
What is the sliding filament model of muscle contraction?
explains how muscles contract by actin (thin filaments) sliding over a myosin (thick filament), shortening the sarcomere and the entire muscle fiber without changing the filament length
What are muscle cells + why are they multinucleate?
Muscle fibers are elongated, multinucleated cells formed by the fusion of multiple embryonic cells. They contain myofibrils and many nuclei to efficiently control protein synthesis and muscle contraction
What are Myofibrils, and how are they structured?
Myofibrils are long, cylindrical structures inside muscle fibers made up of repeating contractile units called sarcomeres. These are aligned in a striated pattern due to alternating actin and myosin filaments
What are sarcomeres + what happens when they contract?
Sarcomeres are the basic contractile units of myofibril, located between the z-lines. During contraction;
- Z-lines move closer together
-I-band shortens
- A-band remains the same
- H-zone disappears
What happens to actin and myosin filaments during muscle contraction?
During contraction, actin filaments slide over myosin filaments, pulling the z-lines closer together and shortening the sarcomere. Neither actin nor myosin changes in length; only their relative positions shift. This process is known as the sliding filament theory
Why do sarcomeres appear as dark and light bands in muscle fibers?
The dark bands (A-bands) are regions where actin and myosin filaments overlap, while the light bands (I-bands) contain only actin filaments. When the muscle contracts, the I-band shortens, and the H-zone (only myosin) disappears, causing the entire sarcomere to shrink
What are the 4 steps of the cross-bridge cycle in muscle contraction?
- ATP hydrolysis; ATP is broken down into ADP +Pi, energizing the myosin head, which moves into a ready position
- Cross-bridge formation; myosin heads bind to actin at exposed binding sites, forming cross-bridges.
- Power stroke; myosin heads bend inward, pulling actin filaments toward the center of the sarcomere. ADP and Pi are released
- Detachment; A new ATP molecule binds to myosin, breaking the cross-bridge, allowing myosin to detach from actin and reset for another cycle
What is the role of ATP in muscle contraction?
ATP is essential for;
- detaching myosin heads from actin (breaking cross-bridges)
- Resetting myosin heads to their high energy state (ATP hydrolysis)
- Powering calcium ion pumps in the sarcoplasmic reticulum to restore calcium levels after contraction
How does calcium regulate muscle contraction?
When a ner signal reaches the muscle;
- Calcium ions are released from the sarcoplasmic reticulum
- Calcium binds to troponin, causing tropomyosin to move, exposing actin’s binding sites
- myosin heads can not attach -> allowing contraction
- when calcium is pumped back into the sarcoplasmic reticulum, muscle relaxation occurs
What are tendons + what is their function?
tendons are connective tissues that attach muscles to bones, allowing force transfer from muscle contraction to skeletal movement
What is the difference between the origin and insertion of a muscle?
Origin; the fixed attachment point of a muscle that does not move during contraction
Insertion: the moveable attachment point that shifts when the muscle contracts
Why do muscles work in antagonistic pairs?
Muscles can only pull (contract), so movement in the opposite direction requires a second muscle with the opposite function. This opposing pair is called an antagonistic pair
Example of an antagonistic pair in human body;
Biceps (flexor); contracts to bend the arm
Triceps (extensor); contracts to straighten the arm
what are antagonistic pairs?
are muscles that work opposite to each other to create movement. When one muscle contracts, the other relaxes, allowing a controlled motion
What is titin?
Titin is an immense protein that has multiple folds that allow it to act as a spring. Muscles also use a force to help with relaxation, as a result of the spring-like action of the protein, titin
How is titin involved in contraction?
When sarcomeres shorten during contraction, the two sides of each sarcomere move towards the centre. This creates a spring-like tension in titin that is released when the muscle relaxes. This allows each sarcomere of the muscle to undergo a contraction once again. Titin also holds myosin fibres in place in the sarcomere and prevents muscle fibres overstretching
Which contraction is under control of your nervous system?
Skeletal muscle contractions. Every movement made requires many electrical impulses originating in your brain and terminating at synapses called neuromuscular junctions. These junctions are a types of synapse where a chemical message is sent into the muscle tissue to stimulate a contractions. Neurons that carry these ‘messages’ are motor neurons
Which neurotransmitter is always released at the neuromuscular junctions?
It is always acetylcholine. Neurotransmitter = chemical that is released
What is a motor unit?
A motor unit consists of a single motor neuron and all the muscle fibres it controls. The number of fibres in a motor unit varies depending on the function of the muscle
How does the number of motor units activated affect muscle contraction intensity?
Low-intensity contraction -> few motor units activated
High-intensity contraction -> more motor units activated.
This allows the body to control force production based on the task
What is the typical ratio of motor neurons to muscle fibres?
The ratio varies from 1:10 to 1:200
What is an endoskeleton, and which animals have it?
an endoskeleton is an internal skeleton make of bone or cartilage found in vertebrates (eg humans, birds, kangaroos). Muscles attach to bones to enable movement
How do differences in bone length and muscle attachment affect movement?
Different bone structures and muscle connections allow specialized movements, such as hopping in kangaroos vs walking in humans
What is and exoskeleton, and what is it made of?
An exoskeleton is a hard external skeleton made of chitin, found in arthropods like insects
How do muscles attach in animals with exoskeletons?
Unlike endoskeletons, where muscles attach outside bones, in exoskeletons, muscles attach to the inside of the hollow skeleton
What is a lever in the skeletal system, and what is its purpose?
A lever is a bone that rotates around a fixed point (fulcrum), reducing the force needed for movement. Levers help maximise efficiency in actions like lifting or walking
What is a fulcrum and how does it function in movement?
A fulcrum is a joint were a lever (bone) rotates. For example, in a nodding movement, that cranium-vertebrae joint acts as a fulcrum while muscles move the head
How do arthropods use their exoskeletons for movement?
Arthropods use their jointed exoskeletons for leverage. Muscles attach inside the chitin armor, working in antagonistic pairs, allowing powerful movements like a fleas 200x body-length jump
What is a synovial joint, and what is its function?
A synovial joint is a moveable joint where two bones meet, allowing a wide range of motion. Examples include the elbow, knee, shoulder, and hip joints
What structures are involved in a synovial joint?
Bones: provide structure
Cartilage: cushions the joint -> reducing friction
Synovial fluid: lubricates the joint for smooth movement
Ligaments: connect bones, stabilizing the joint
Tendons: attach muscles to bones, enabling movement
(Hip) what type of joint is the hip joint and how does it function?
The hip joint is a synovial joint in the type of a ball-and-socket joint, where the head of the femur fits into the pelvis. this structure allows for a wide range of motion in multiple directions
What roles does cartilage play in the hip joint?
Cartilage covers the ends of bones preventing bone on bone contact, reducing friction, and absorbing shock during movement
How do ligaments and tendons contribute to hip joint stability?
Ligaments; hold bones in place, providing stability while allowing movement
Tendons; attach muscles to bones, enabling movement of the hip joint
What is synovial fluid, and why is it important?
Synovial fluid is a lubricant found in synovial joints, including the hip, that reduces friction between bones and allows smooth movement
Pelvis structure; Pelvis + femur, function (hip)
Bones forming the ball-and-socket joint of the hip
Pelvis structure; cartilage, function (hip)
A smooth protective connective tissue that lines both the pelvis and femur within the hip joint
Pelvis structure; synovial fluid, function (hip)
Lubricating fluid within the hip joint that reduces friction
Pelvis structure; ligaments, function (hip)
Tough connective tissues that holds the bones of the hip joint in place
Pelvis structure; Tendons, function (hip)
Connective tissue that connects each of the muscles of the hip joint to its appropriate bones
Pelvis structure; muscles, function (hip)
Muscle tissues that contract and relax to enable movement of the femur within the socket of the pelvis
What is the device used to measure range of motion?
A goniometer is used to measure the range of motion of a joint. Range of motion is the distance and direction that a joint can move, and is usually measured in degrees.
The measurements can be used to document improvements in joint movement (After injury, etc). Some joints are capable of movement in a number of dimensions
What are intercostal muscles, and where are they located?
they are paired muscles between each rib that control ribcage movement during breathing. They consist of external intercostal muscles (outer layer) and internal intercostal muscles (inner layers)
What is the function of the external intercostal muscles?
The external intercostal muscles contract during inspiration, pulling the ribs upward and outwards, expanding the thoracic cavity to allow air intake
What is the role of the internal intercostal muscles?
these contract during expiration, pulling the ribs downward and inward, reducing thoracic cavity volume and helping push air out
How do intercostal muscles work as antagonistic pairs?
During inspiration, external muscles contract, and internal muscles relax to lift the ribcage
During expiration, internal muscles contract, and external muscles relax to lower the ribcage
How do intercostal muscles contribute to the mechanics of breathing?
By changing the volume of thoracic cavity, intercostal muscles help regulate air pressure in the lungs, allowing inhalation and exhalation to occur efficiently
How does muscle stretching occur during breathing?
When the external intercostal muscles contract, the ribcages expands, stretching the internal intercostal muscles. When internal intercostal muscles contract, the external intercostal muscles stretch
What role do titin fibres play in intercostal muscle function?
Titin fibres in the sarcomeres store potential energy when the opposite intercostal muscle stretches. This stored energy helps facilitate the next contraction
How does potential energy storage aid respiration?
The stretching of the relaxed intercostal muscle stores potential energy, which is later used to make contraction more efficient and reduce energy expenditure
What is locomotion?
the ability to move from place to place
Why do animals move?
- to find food
- to find mate
- to escape predators
- to migrate
Moving reason; food + example + description
Honey bees. They are flying from flower to flower to collect nectar and pollen
Moving reason; escaping danger + example + description
Flying fish. They are escaping predators by swimming fast and extending their very long pectoral fins to glide over the water
Moving reasons; mate + example + description
Loggerhead sea turtle. Both males and females swim back to the beach where they were hatched to mate and lay eggs
Moving reason; migration + example + description
Arctic tern. Migrating from their arctic breeding grounds to the antarctic region and back each year, to take advantage of available foot
Marine mammals (dolphins, whales, seals, etc)
They are all descended from ancestral species that once lived on land. Their internal anatomy is adapted to a marine environment but still has many similarities with their land ancestors
Adaptation of dolphins in order for them to be successful inhabitants of ocean waters
- have a streamlined body -> allowing the animal to move through water with ease and speed
- no body hair -> reduce drag through the water
- tail adapted to form a fluke -> allows up/down motion for propulsion
- front limbs adapted to flippers -> used for steering
- Have an airway -> to exchange air at periodic intervals with a minimum of the body leaving the water
- Can seal blowhole tightly -> water does not enter airway
- can stay underwater for several minutes -> they can make deep dives
- they still have retained some mammalian characteristics (being endothermic, producing milk for their young, having an advanced two-sides circulatory system, and long-term parental care of their young
