Muscles 1 Flashcards
(35 cards)
3 muscle types and briefly what they do:
Smooth muscles: mainly line hollow organs (gut, blood vessels) and are not under voluntary control
Cardiac muscles: located only in the heart, generates force to pup blood around the body and is not under voluntary control
Skeletal muscles: apply a force to the bones to control posture and body movements. Is under voluntary control. Striated/striped.
Primary Job of skeletal muscles
To develop tension or force
- muscles develop force in only one direction and they do this by shortening
(Skeletal muscle is important for movement and posture)
Secondary jobs of skeletal tissue
- support and protection for soft internal organs (e.g muscles of abdominal wall)
- provides voluntary control over major openings (allows the passage of substances into or out of our body)
- converts energy (in part) to heat which is used to maintain core temperature (eg shivering)
- provides major storage for energy and protein
SPCP
Structural features
-skeletal muscle fibres are huge and multinucleate cells containing large amounts of protein
- connective tissues ensheath the muscle, and connect fibres to the bones
- skeletal muscle is richly supplied with blood vessels and nerve fibres
Whole muscle structure
- muscle fibres are gathered into bundles called fascicles
- fasicles are gathered into bundles called muscles
- fibres, fascicles and muscles are each ensheathed in connective tissue
- connective tissue investments are gathered together to form tendons
- tendons connect muscles to bones
How various cells are arranged to form skeletal muscles
- muscles are attached to bone via tendon
- muscles are comprised of muscle tissue, nerves, blood vessels and connective tissue
- each muscle is made of multiple muscle fibres
- each muscle fibre is made of multiple myofibrils
Endomysium
Surround each muscle fibre
Perimysium
Surround each fascicle (bundle of muscle fibres)
Epimysium
Surround entire muscle
Surround each muscle fibre
Endomysium
Surround each facicle
Perimysium
Surround entire muscle
Epimysium
How many nuclei in a muscle fibre
Hundreds to thousands - on the outside
How big are muscle fibres
20-40 micrometers in diameter but may be centimetres long
Key structural composition of a muscle fibre
- comprised of bundles of myofibrils
- myofibrils are made of repeating units known as sarcomeres
- sarcomeres are made of contractile proteins or myofilaments (actin - thin filament, myosin - thick filament)
Two mayofilaments
- actin (thin filaments)
- myosin (thick filaments)
What gives muscle its striated (striped) appearance
The organisation of the myofilaments
Describe the purpose of the system of structures muscle fibres posses and some of these structures
- Muscle fibres possess a system of structures organised to regulate the activity of the force-producing elements
- Transverse tubules
SR
Two myofilaments are:
- actin (thin filaments)
- myosin (thick filaments)
Definition of transverse tubules (T-tubules) and their function
Tubular extention (invaginations) of the surface membrane
Function: to conduct electrical signals (action potentials) deep into the core of the fibre
Sacroplasmic reticulum (SR) definition
SR is an extensive membranous tubular network associated precisely with the T tubules at regular intervals.
How the membrane triplet (triad) is formed
The terminal chambers (terminal cisternae) of each SR structure associate with the T-tubules to form a membrane triplet called a triad
Function of the sacroplasmic Reticulum
- to take up and store calcium
- to release Ca2+ into the cytoplasm on the receipt of an action potential conducted along the associated T-tubules
The sacromeric structure of the myofilaments arise do to:
The arrangement if contractile proteins
- thick filaments (primarily myosin) interlace with thin filaments (primarily actin)
