Muscle and motility Flashcards
What is the significance of movement in living organisms?
Movement is a universal feature of living organisms that allows them to find food, escape predators, reproduce, and adapt to changing environments. It plays a crucial role in survival and evolutionary success.
Define motile organisms and provide an example.
Motile organisms are those that can move independently and actively through their environment. An example is a fish, which uses fins to swim and navigate through water.
Define sessile organisms and provide an example.
Sessile organisms are those that remain fixed in one place and do not move actively. An example is a barnacle, which attaches itself to surfaces like rocks or ships and relies on water currents for feeding.
How do motile organisms adapt for movement?
Motile organisms have adaptations such as specialized limbs or fins for locomotion, flexible body structures for maneuverability, and sensory organs to navigate their environment effectively.
What adaptations do sessile organisms have for their lifestyle?
Sessile organisms often have adaptations such as strong attachment mechanisms (e.g., glue-like substances or hard shells) to anchor themselves, as well as structures like tentacles or filter-feeding systems to capture food from the surrounding environment.
Compare the energy expenditure of motile versus sessile organisms.
Motile organisms generally expend more energy for movement, requiring muscles and metabolic processes to facilitate locomotion. In contrast, sessile organisms have lower energy requirements since they do not actively move but rely on passive methods for feeding and reproduction.
How does movement contribute to the survival of motile species?
Movement allows motile species to explore new habitats, search for food, avoid predators, find mates, and migrate in response to environmental changes, all of which enhance their chances of survival.
What are some examples of environmental factors that influence movement in organisms?
Environmental factors influencing movement include:
- Availability of food sources
- Presence of predators
- Temperature and weather conditions
- Water currents (for aquatic organisms)
- Terrain type (land vs. water)
How does the concept of movement relate to evolution?
The ability to move has significant evolutionary implications; it can lead to diversification of species as they adapt to different environments. Movement-related adaptations can enhance reproductive success and survival, influencing natural selection.
Why is it important for students to explore both motile and sessile species?
Exploring both motile and sessile species helps students understand the diversity of life forms and their adaptations. It illustrates how different strategies for movement or lack thereof can be advantageous in various ecological niches.
What is the sliding filament model of muscle contraction?
The sliding filament model explains how muscle fibers contract through the sliding of actin and myosin filaments past each other within the sarcomere, leading to shortening of the muscle.
What are the key components of a sarcomere?
The key components of a sarcomere include:
- Actin filaments (thin filaments)
- Myosin filaments (thick filaments)
- Z-lines (boundaries of the sarcomere)
- M-line (center of the sarcomere)
How do actin and myosin interact during muscle contraction?
During muscle contraction, myosin heads attach to binding sites on actin filaments, forming cross-bridges. The myosin heads then pivot, pulling the actin filaments toward the center of the sarcomere, which shortens the muscle fiber.
What role does ATP play in muscle contraction?
TP provides the energy required for muscle contraction. It is necessary for:
- The detachment of myosin heads from actin after a power stroke
- The re-cocking of myosin heads to form new cross-bridges
What initiates the process of muscle contraction at the molecular level?
Muscle contraction is initiated by an action potential from a motor neuron, which triggers the release of calcium ions from the sarcoplasmic reticulum. Calcium binds to troponin, causing a conformational change that exposes binding sites on actin.
How does calcium ion concentration affect muscle contraction?
Increased calcium ion concentration in the cytoplasm facilitates the binding of myosin to actin by moving tropomyosin away from binding sites on actin. When calcium levels drop, tropomyosin re-covers these sites, leading to muscle relaxation.
Describe the power stroke in the sliding filament model.
The power stroke occurs when myosin heads pivot and pull actin filaments toward the center of the sarcomere after forming cross-bridges. This action shortens the sarcomere and generates force during contraction.
What happens to the sarcomere during muscle contraction?
During muscle contraction, the sarcomere shortens as actin filaments slide over myosin filaments. The distance between Z-lines decreases, while the lengths of actin and myosin filaments remain unchanged.
How does repeated stimulation affect muscle contraction?
Repeated stimulation can lead to sustained contractions (tetanus) as calcium remains elevated in the cytoplasm, allowing for continuous cross-bridge cycling and force generation until fatigue occurs.
Why is understanding the sliding filament model important in physiology?
Understanding the sliding filament model is crucial for comprehending how muscles contract and produce movement. It also provides insights into various muscular diseases and conditions that affect muscle function and performance.
What is the role of the protein titin in muscle function?
Titin is a large protein that helps sarcomeres recoil after stretching and prevents overstretching. It provides structural support and elasticity, allowing muscles to return to their resting length after contraction.
How does titin contribute to muscle elasticity?
Titin acts like a spring within the sarcomere. When a muscle is stretched, titin uncoils, storing elastic potential energy. Upon relaxation, it recoils, helping the muscle return to its original length.
What are antagonistic muscles?
Antagonistic muscles are pairs of muscles that work against each other to facilitate movement. When one muscle contracts (the agonist), the other muscle (the antagonist) relaxes to allow for controlled movement.
Why are antagonistic muscle pairs important for movement?
Antagonistic muscle pairs are essential because muscle tissue can only exert force when it contracts. The coordinated action of opposing muscles allows for smooth and controlled movements in joints.
Give an example of an antagonistic muscle pair.
An example of an antagonistic muscle pair is the biceps brachii and triceps brachii in the upper arm. When the biceps contract to flex the elbow, the triceps relax; conversely, when the triceps contract to extend the elbow, the biceps relax.
How does titin prevent overstretching of muscles?
Titin provides passive tension when a muscle is stretched beyond its optimal length. This resistance helps prevent excessive elongation of the sarcomere and protects muscle fibers from damage during extreme stretches.
What happens to titin during muscle contraction and relaxation?
During contraction, titin becomes taut as it stores elastic energy. Upon relaxation, it helps pull the actin and myosin filaments back to their resting positions, aiding in the recovery of muscle length.
How do antagonistic muscles contribute to joint stability?
Antagonistic muscles contribute to joint stability by maintaining tension around joints. This balance between opposing forces helps prevent injury and allows for precise control during movement.
Why is understanding titin and antagonistic muscles important in physiology?
Understanding titin and antagonistic muscles is important because it provides insights into how muscles function during movement and recovery. It also helps explain mechanisms behind injuries, rehabilitation, and overall musculoskeletal health.
How do titin and antagonistic muscles work together during physical activity?
During physical activity, titin aids in maintaining muscle elasticity and preventing overstretching while antagonistic muscles coordinate movements by contracting and relaxing in opposition, ensuring efficient and controlled motion.
What is a motor unit in skeletal muscle?
A motor unit consists of a single motor neuron and all the skeletal muscle fibers it innervates. It is the basic functional unit of muscle contraction.
How does a motor neuron communicate with muscle fibers?
A motor neuron communicates with muscle fibers at the neuromuscular junction (NMJ), where it releases the neurotransmitter acetylcholine (ACh) to stimulate muscle contraction.
What are the main components of a neuromuscular junction?
The main components of a neuromuscular junction include:
- Presynaptic terminal (axon terminal of the motor neuron)
- Synaptic cleft (the gap between the neuron and muscle fiber)
- Postsynaptic membrane (muscle fiber membrane with ACh receptors)
What happens at the neuromuscular junction during muscle contraction?
When an action potential reaches the presynaptic terminal, calcium ions enter, triggering the release of acetylcholine into the synaptic cleft. ACh binds to receptors on the muscle fiber, leading to depolarization and subsequent muscle contraction.
How does the structure of a motor unit affect its function?
The size of a motor unit varies; smaller units (e.g., eye muscles) allow for precise control of movement, while larger units (e.g., leg muscles) generate more force. All muscle fibers in a motor unit contract simultaneously when activated.
What role do synaptic vesicles play in neuromuscular transmission?
Synaptic vesicles in the presynaptic terminal store acetylcholine. Upon stimulation, they fuse with the membrane and release ACh into the synaptic cleft, facilitating communication between the motor neuron and muscle fiber.
What is the function of acetylcholine in muscle contraction?
Acetylcholine acts as a neurotransmitter that binds to receptors on the postsynaptic membrane of muscle fibers, initiating an action potential that leads to muscle contraction.
How does acetylcholinesterase contribute to neuromuscular function?
Acetylcholinesterase is an enzyme that breaks down acetylcholine in the synaptic cleft after it has activated receptors. This process prevents continuous stimulation of the muscle fiber, allowing for controlled contractions.
Why is understanding motor units important in physiology?
Understanding motor units is important because they are fundamental to how muscles contract and produce movement. Knowledge of their structure and function helps explain various muscular disorders and rehabilitation strategies.
How do multiple motor units work together during muscle activity?
Multiple motor units can be recruited simultaneously or sequentially to increase force production during activities. This recruitment allows for graded contractions, enabling fine control or powerful movements as needed.
