BIOL 273 - Unit 3.1 +3.2 Flashcards
What is a muscle?
tissue specialized to convert biochemical rections into mechanical work
4 functions of muscle
- generate motion and force
- only contract
- only expands when physically pulled by antagonistic muscle groups
- generate heat and contribute to body temperature homeostasis
What are the three types of muscle in the human body
skeletal, smooth, cardiac
describe skeletal muscle
- attached to bones of the skeleton to control body movement
- contract in response to signal from somatic motor neuron - cannot intitate contraction on its own/ be influenced by hormones
- attached to bones via tendons
describe smooth muscle
- primary muscle of internal organs and tubes (stomach, blood vessles, urinary bladder)
- influences movement of materials through the body)
- no striations
describe cardiac muscle
- found only in the heart - pump to move blood around the body
- striations
What percent of body weight do skeletal muscles consist of
40% of body weight
What are tendons composed of
dense regular connective tissue - collagen
What are outer connective tissue of skeletal muscle called
epimysium
What are the bundles of muscle tissue in skeletal muscle called and what do they contain
fascicles
- nerves and blood vessels
- muscle fibres
what are fascicles covered in
perimysium (connective tissue sheath)
What are muscle fibres within fascicles covered in
innermost connective tissue sheath: endomysium
What are contained within the muscle fibres
functional units: myofibrils
(takes up majority of space)
- contain contractile and elastic protein bundles
Describe the structure of a muscle fibre
- long/cylindrical cell
- several hundred nuclei on the surface of the fibre
- cell membrane is called sarcolemma
What are the endoplasmic reticulum in muscle fibres called
sarcoplasmic reticulum
What other structures are associated with sarcoplasmic reticulum in muscle fibres
- T tubules (transverse tubules)
- terminal cisternae (sequester Ca+2 storage)
- T tubule with flanking terminal cisternae : triad
What is the purpose of T tubules in muscle fibre
allow for rapid action potential diffusion into the muscle fibre
Myofibrils: what are the three types of bundles of contractile ealstic proteins
- Contractile proteins - actin and myosin
- Regulatory proteins - troponin and tropomyosin
- Accessory proteins - nebulin (aligns thin filament) and titin (elastic protein that returns stretched muscle to relaxed state)
Describe myosin (what do they consist, what do they form, how are they arranged)
- a motor protein that consists of two coiled protein molecules (chains) that have two important parts - head and tail region
- arranged so head are at the ends and tails are together
What do myosin join for form
- about 250 myosin molecules join to form THICK FILAMENT
Describe actin (subunits, what do they form)
- subunits G-actin (globular actin)
- G- actin subunits polymerize to form chain (F-actin) - filamentous
What do actin join to form , describe the full process of the formation of this structure
two F-actin chains twist together to form basis of THIN FILAMENT
- coiled F-actin associates with regulatory proteins - Troponin and Tropomyosin (regulate muscle contraction)
- forms completed thin filament
What are the thick and thin filament organization resultign in striations seen in skeletal muscle called
sarcomere
What are the five components of the sarcomere
- Z-line (disks)
- I- band (isotropic)
- A band (anisotropic)
- H zone (part of the A band)
- M line
sarcomere: Describe the Z-line (disks)
site of attachment for thin filaments
- one sarcomere is made of 2 Z discs and the filaments between them
sarcomere: Describe the I band
region containing ONLY thin filaments
- a Z disc runs through the middle of an I band - thus each 1/2 of the I band is part of a different sarcomere
sarcomere: describe the A band
region containing thick and think filaments
- thick and thin filaments overlap at the outer edges of the A band
- the center is occupied by thick filaments only
sarcomere: describe the H zone
region containing ONLY thick filaments
- central region is lighter than the outer edges
sarcomere: describe the M line
site of attachment for the thick filaments
- the M line is the center of the sarcomere
