Skeletal muscle and synaptic transmission Flashcards
What are the three main types of muscles in the human body?
The three main types of muscles are skeletal muscles, cardiac muscles, and smooth muscles.
Where can skeletal muscles be found in the body?
Skeletal muscles can be found in areas like the biceps, calves, thighs, diaphragm, and other regions involved in movement.
Where are smooth muscles located in the body?
Smooth muscles are found in the walls of arteries, the guts, the bladder, and reproductive organs.
What is one similarity between skeletal muscle and cardiac muscle?
Both skeletal and cardiac muscles have a striated appearance due to the regular arrangement of actin and myosin filaments.
How do skeletal muscle cells differ from cardiac muscle cells in terms of structure?
Skeletal muscle cells are very long, contain multiple nuclei, and have many mitochondria. In contrast, cardiac muscle cells typically have only one nucleus and exhibit a branching phenotype.
Why are smooth muscles not striated?
Smooth muscles are not striated because their actin and myosin filaments are not arranged in a regular pattern, and they are smaller in size compared to skeletal and cardiac muscles. Additionally, smooth muscle cells only have one nucleus.
What is the T-tubule system, and which types of muscles have it?
The T-tubule system is a network of membrane structures characteristic of skeletal and cardiac muscles. It plays a role in transmitting electrical signals deep into the muscle fibres.
What is a fascicle in skeletal muscle?
A fascicle is a bundle of muscle fibres (muscle cells) in skeletal muscle. Each fascicle contains many muscle fibres, and within each fibre are smaller structures called myofibrils.
How do muscles contract?
A motor nerve releases neurotransmitters like acetylcholine, which causes the muscle cells to shorten. This depolarizes the muscle, opening voltage-gated sodium or calcium channels, leading to the activation of muscle contraction mechanisms.
What role do sodium and calcium ions play in muscle contraction?
Sodium ions are involved in depolarizing the muscle fibres, while calcium ions are crucial for activating the contractile proteins actin and myosin, allowing the muscle to contract.
What are SNARE proteins, and what do they do?
SNARE proteins are involved in the release of neurotransmitters from vesicles. V-SNAREs (e.g., Synaptobrevin) are found in vesicles, and T-SNAREs are found in the cell membrane. These proteins are calcium-sensitive and help facilitate vesicle fusion.
What is botulism, and how does it affect muscle function?
Botulism is caused by a toxin that binds to glycoproteins on cholinergic neurons, preventing the release of acetylcholine, which inhibits muscle contraction, leading to paralysis.
What is the function of dihydropyridine receptors (DHPRs) in muscle cells?
DHPRs are voltage-sensitive calcium channels located in the muscle cell membrane. They play a role in activating ryanodine receptors, which release calcium from the sarcoplasmic reticulum to trigger muscle contraction.
What is Calcium-Induced Calcium Release (CICR)?
CICR is a mechanism where the entry of calcium ions into cardiac muscle cells activates the release of more calcium from the sarcoplasmic reticulum, amplifying the calcium signal and aiding in muscle contraction.
What is the role of troponin in muscle contraction?
Troponin is a calcium-sensing protein in skeletal and cardiac muscle that helps regulate the interaction between actin and myosin, enabling muscle contraction.
