muscles Flashcards
(43 cards)
what are the roles of our muscles
-movement of bones. fluids (GIT), blood (vessels) and fluids (excretory system)
-thermoregulation: creates body heat
- energy metabolism and storage (glycolysis)
- appetite regulations (myokines and satiety)
-endocrine functions
what are muscles made of
-1% vitamins and minerals
- 5% fats
- 1% carbs
- 18% proteins
- 75% water
how much more muscle mass do males have compared to females
males have 40% body mass while females have 30% . this difference is greater in the upper body.
when do we have peak muscle mass and when does it start to degrade
age 25. by 40-70 we lose 8% muscle mass every decade
what are the properties of muscles
-contractility: shorten with force. requires energy and relaxes passively.
-excitabiity: respond to stimulation from nerves and electrical stimulation (heart)
- extend: stretch its normal resting length and beyond its limited degree, stomach/bladder expand as fill
- elastic: return or recoil to resting position when relaxed.
that are the three types of muscles
- skeletal
-cardiac - smooth
what is the skeletal muscle
attached to the skeleton- responsible for movement and involves voluntary movements
what is the cardiac muscle (myocardium)
forms the heart- responsible for pumping blood. involuntarily
what is smooth muscle
located in the tissues- responsible for controlling diameter of structures and peristalsis. involuntary movement.
structural of skeletal muscle
muscle - fascicle- cell -myofibril
what part of the muscle enable contraction
myofibril
whats interesting about the nuclei of the muscle cell
there’s multiple of them and they sit on the periphery of the cell. there’s lines like a zipper because of sarcomeres.
what is the muscle fibre structure that enable it to contract
the myofibril is responsible for contractions. it is made of sarcomeres which are made of actin and myosin which provide striation on muscle cells.
difference between actin and myosin
actin-thin myofilament
myosin: thick filament
they sit between two z discs and there’s a m line in the middle. we get contraction by the two sides by sliding each other and pulling the z lines together.
how do the actin and myosin move and slide together
myosin which are anchored on the sarcomere called the m line. the actin is anchored on the z line. when the filaments slide, the z line is pulled with it, making the muscle contact. the myosin pulls the actin along tis length. the cross bridges of the filaments attach to the actin filaments and exert force on them to move- sliding filament mechanism.
how are calcium release to the muscles
they are stored in the sacroplasmic reticulum and are released via signals from the nervous system to contract and the cell will undergo depolarisation.
how does a contraction begin and how does it use energy
ATP is hydrolysed to ADP causing the myosin to extend attach to the actin forming a cross bridge. the ADP is release until a new molecule rives and pulls ti again close to the m line. It is controlled by calcium. the thin actin filaments are associated with regulatory proteins called troponin and tropomyosin. when the muscle is relaxed, tropomyosin blocks the cross bridge site. but enough calcium and peresnce of ATP, the calcium will bind to the troponin which will expose the myosin binding sites to action and form a cross bridge site.
what are the 5 steps that allow muscle contraction
- ATP bound myosin is int he released position. 2. ATP is dephosporylated to ADP. it is positioned to form a cross bridge. if the calcium is low, the tropomyosin blocks this path
- electrical excitation of the muscles release calcium from the sacroplasmic reticulum where It will being to a troponin and move the tropomyos in out of the way and form the cross bridge to form.
- this drives the power stroke which is the release of the phosphate bound to myosin head- myosin moves along acid filament
- at the end of excitation. calcium pumps back into Sacroplasmic Reticulum allowing tropomyosin to block myosin binding against and ADP becomes ATP again.
what determined how quickly muscle cells can contract
the speed of ATP use and replacement
define the terms:
- sacro and myo:relating to muscle
- striated: parallel lines
- skeletal muscle: lots of bundles of muscles held together by connective tissue
- fascicle: bundle of muscle cells
-myofibril: located in the cytoplasm of muscle cell - myofilament: atin and myosin arranged to form fibrils
- sarcomere- repeating overlapping arrangement of myofilaments that crate the myofibril
- sacroplasmic reticulum; stores the calcium and is involved in muscle contraction
what are cardiac muscle and how does it compare to skeletal muscle
they both have striations and they have similar contraction mechanism. they have different structural features, cells. IMPORTANT to know that the nuclei is in the centre rather than peripheral. cardiac also usually has single nuclei and that skeletal is motor for involuntary movement and autonomic for involuntary pumping of blood. hypertrophy in skeletal muscle involves satellite cells- bring additional nuclei as muscle size grows while any hypertrophy in cardiac muscle is detrimental. There is no renewal
what are the two muscle fibre types
type 1: slow twitch
type 2: fast twitch
all muscles have both
explain type 1 fibres
they are slow twitch and considered red because they have high myoglobin content which transports oxygen. it contract slower but is also slower to fatigue. its supplied by nerves that activate to contract. uses aerobic metabolism to generate large amount of ATP- adapted to deliver oxygen to mitochondria to facilitate ATP because they rely on it.
explain type 2 fibres
they are fast fibres. they contract very quickly but also tire quicker. it does not have myoglobin so its less oxygen and is also considered blue. it uses anaerobic metabolism generate less ATP. its not adapted to deliver mitochondria.
