Lecture 8 Muscle tissue Flashcards
Describe the basic properties of muscular tissue
◦Excitability- responds to stimuli from the nervous system
◦Contractibility- shortens
◦Elasticity - ability to return to original shape and form
◦Extensibility- stretch further than normal length
Describe the functions of muscular tissue
◦Movement ◦Maintenance of posture ◦temperature regulation- contraction of muscles generates heat ◦storage and movement of materials ◦support abdominal organs ◦Joint stabilization
What are the characteristics of cardiac muscles
◦striated ◦found in the heart ◦branched/Y shaped ◦uni/binucleate ◦Involuntary ◦Intercalated discs ◦Auto-rhythmic
What are the characteristics of smooth muscles?
◦non-striated ◦involuntary ◦fusiform/ football shape ◦Fatigue resistant ◦found in walls of visceral organs
What are the characteristics of skeletal muscles?
◦voluntary ◦cylindrical in shape ◦multinucleate ◦striated ◦innervated- Neuromuscular joints vascular
Briefly explain how skeletal muscle cells develop from myoblasts.
Myoblasts fuse together to form a muscle cell (getting longer and connected). A satellite cell fuses to the outside. The many myoblasts fusing together means that there are several nuclei in each cell.
What is meant by the terms “origin” and “insertion” when discussing skeletal muscle attachments? What is the difference between a tendon and an aponeurosis?
•Origin: Less movable attachment site
•Insertion: More movable attachment site
•Tendon: connects bone to muscle
◦Aponeurosis is a flat tendon
What are the basic compositions and functions of each of the structures in a muscle fiber
sarcolemma: cell membrane
sarcoplasm: Cytoplasm in a myo cell
Transverse tubules (t-tubules): continuous with sarcolemma; when electricity goes into the muscle, it goes down into t-tubules as well.
Sarcoplasmic reticulum: calcium store; includes terminal cisternae
Nuclei: several in each muscle cell
Mitochondria: makes ATP
Myofibrils: bundles of myofilaments
Myo filaments: most deep structures in this diagram.
What is the composition of thick filaments
Thick filaments are composed of the protein, myosin. It has many heads that look like golf clubs coming from it.
What is the composition of thin filaments
Thin filaments are composed of an actin core and contains the calcium binding protein troponin as well as tropomyosin which covers the myosin binding site.
Briefly explain the events involved in muscle contraction.
- A nerve impulse sends electricity across the sarcolemma
- The electricity enters the myofiber through the T-tubules which then activates the release of calcium from the terminal cisternae
- The calcium enters the myofilament and binds to troponin, which causes the tropomyosin to shift and reveal the binding sites on the actin
- The myosin bind to actin and pull the thin filament inward, causing the muscle to contract
- Calcium pumps (powered by ATP) cause the muscle to relax and the tropomyosin return to their position covering the actin
Discuss rigor mortis,
◦Death is a process because cells life after the brain, heart and lungs fail.
◦ATP runs out a few hours after death, so myosin cannot detach from actin
◦Calcium cannot be taken up by sarcoplasmic reticulum
◦Both combine to cause muscles to be continuously contracted
Discuss tetanus
◦Caused by a bacteria Clostridium tetani, which gets into an open wound. Common after getting pierced by a rusty, metal object (nail).
◦leads to excessive muscle contraction; Lock Jaw
Discuss botulism
◦Caused by bacterium Clostridium botulinum, which grows in anaerobic states
◦Usually due to improper canning of food
◦leads to muscular paralysis
◦Small amounts are legal in the form of Botox, which lets the muscles relax to lessen wrinkles.
how do skeletal muscles develop from myotomes.
muscle comes from mesoderm.
