Module 5-Midterm- Muscles Flashcards
1
Q
What are the three types of muscles?
A
- skeletal: primarily for voluntary motion
- cardiac: found in the heart
- smooth: walls of blood vessels, airways, ducts, bladder, uterus and digestive tract
2
Q
What is the purpose of muscles?
A
- movement
- heat production
- body support and posture
- 600 diff muscles in the body
3
Q
Structure of the muscle
A
- whole muscles are made up of bundles of fasiculi
- each fascicle is made up of muscle cell or fiber
- each muscle cell or fiber contains myofibrils
- myofibrils have thick and thin filaments
- thick myofilaments have myosin
- thin myofilaments have actin, troponin and tropomyosin
- fasciculi surrounded by perimysium
4
Q
what is the sarcolemma?
A
- surrounds muscle cell
- muscle cell membrane
- over where the action potential is transmitted
5
Q
what are the transverse tubules?
A
- tubelike projections off the sarcolemma that extend down into the cell
- conduct action potentials depp into the cell where the myofibrils are located
6
Q
what is the sarcoplasmic recticulum?
A
- surrounds myofibrils
- mesh like networks of tube containing Ca ions
7
Q
Terminal Cisternae
A
- at either end of sarcoplasmic reticulum
- a membranous enlargement of SR
8
Q
Thin myofilament
A
- made of globular protein actin
- contains special binding site for myosin
- tropomyosin protein found here (covers binding site when muscle is at rest)
- troponin A binds to actin
- troponin T binds to tropomyosin
- tropinin C binds to Ca+
- troponin C binds to Ca+ and pulls tropomyosin off the binding site
9
Q
Thick myofilament
A
- myosin
- long, bendable tail protein with two heads to attach to myosin binding site
- also has head that can bind to ATP that releases energy to myosin that powers contraction
- many myosin molecules arranged to make one thick filament
10
Q
Actin/Myosin Relationship
A
-thin and thick filaments arranged in a repeating pattern
-z disk= from one Z disc to another
-m line= centre of sacromere, group of thick fila extend outward from this line
-A bands= thick filaments
-I bands= think filaments
sacromere= from one z disc to another
11
Q
sliding filament theory
A
- head of myosin molecule attaches to myosin binding site on actin, forms and crossbridge and the myosin changes shape
- change in shape causes myosin head to swing, producing a power stroke
- powerstroke slides actin passed myosin
- thin or thick filaments DO NOT shorten during contraction
12
Q
Excitation contraction coupling
A
- process in which an AP in the cell membrane (sarcolemma) excites the muscle cell to produce a contraction
- the AP generated at the NMJ will spread out over the sarcolemma, down the T tubules into the core of muscle cell
- AP travels very close to the SR and will open Ca+ channels, causing a release of Ca+ from the terminal cisternae of the SR
- Ca+ binds to troponin C on the thin myofilament, causing tropomyosin to uncover the myosin binding sites
- myosin will attach to actin and the Powerstroke will occur
13
Q
Relaxation of the muscle
A
- once AP stops, Ca+ will no longer diffuse out of the SR
- special Ca+ pumps rapidly pump Ca+ back into the SR (up its concentration gradient, requires ATP)
- without calcium present in the cytoplasm of the cell, tropomyosin will cover the binding sites again, and the Powerstroke will not take place
- muscles will not relax if there is a build up of Ca+
14
Q
ATP cycle and muscle contraction
A
- ATP splits to ADP and PI head, releases energy to myosin and prepares the head from activity
- An action potential occurs, Ca+ is released from the SR and binds to troponin C. This rolls tropomyosin off the binding site on actin
- Powerstroke occurs, and the ADP and PI are released from the myosin head
- new ATP molecule binds to the myosin head
15
Q
Rigor Mortis
A
- 3/4 hours after death
- stiffness disappears after 24-48 hrs
- results from the loss of ATP in muscles
- slow degradation of the SR, causes a release of Ca+
- cross-bridge is formed, however without ATP the bonds cannot be broken (will eventually let go with cell degeneration)
