Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

biology > skeletal muscles are stimulated to contract by nerves and act as effectors > Flashcards

skeletal muscles are stimulated to contract by nerves and act as effectors Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

what does the phrase “antagonistic pair of muscles” mean

A
  • muscles can only pull so they work in pairs to move bones around joints
  • pairs pull in opposite directions: agonist contracts while antagonist is relaxed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

define ligaments

A

attach bones to bones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

define tendons

A

attach bones to muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what do agonist muscles do

A

contract (pull)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what do antagonist muscles do

A

relax (push)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

name the 3 types of muscle in the body and where they are located

A
  1. cardiac - heart (contract with no conscious control)
  2. smooth - walls of blood vessels and intestines (contract with no conscious control)
  3. skeletal - attached to incompressible skeleton by tendons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

describe the gross structure of skeletal muscles

A
  • muscle cells are fused together to form bundles of parallel muscle fibres called myofibrils
  • muscle fibres are multinucleate
  • arrangement ensures there is no point of weakness between cells
  • each myofibril is surrounded by an endomycium (loose connective tissue with many capillaries)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe the microscopic structure of a skeletal muscle

A
  • myofibrils: site of contraction
  • sarcoplasm: shared nuclei and cytoplasm with lots of mitochondria (for respiration to provide ATP) and endoplasmic reticulum
  • sarcolemma: folds inwards towards sarcoplasm to form transverse (t) tubules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

describe the ultrastructure of a myofibril

A
  1. Z-line: boundary between sarcomes
  2. I-band: only actin (light colour on electron micrograph)
  3. A-band: overlap of actin and myosin (dark colour on electron micrograph)
  4. H-zone: only myosin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how do you differentiate between A-band and I-band on an electron micrograph

A
  • I-band: thin and light
  • A-band: thick and dark
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the function of tropomyosin

A

blocking/inhibiting the actin-myosin binding site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

describe a relaxed muscle

A
  • the actin-myosin binding site is blocked by tropomyosin
  • this prevents an actinomyosin bridge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe a contracted sarcomere

A
  • myosin and actin filaments slide over one another to make the sarcomeres contract
  • sarcomere becomes shorter
  • I-band becomes shorter
  • H-zone becomes shorter
  • a-band stays the same
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

describe the role of calcium ions and ATP in myofibril contraction (sliding filament theory)

A
  • calcium ions cause the tropomyosin to move out of the actin-myosin binding site
  • allowing the actinomyosin bridge to form
  • calcium ions activate ATPase (catalyses hydrolysis of ATP)
  • atp is used to change the shape of the myosin head (power stroke)
  • continues as long as the binding site is open (calcium ions = action potential)
  • atp is used to detach the myosin head from the binding site
  • atp is used to return the myosin head to resting (original) position
  • atp is needed to reabsorbed calcium ions via active transport against concentration gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

explain how muscle contraction is stimulated

A
  • in neuromuscular junction action potential occurs opening voltage-gated calcium channels
  • vesicles move towards and fuse with presynaptic membrane
  • exocytosis of acetylcholine which diffuses across synaptic cleft
  • acetylcholine binds to receptors on Na+ channel protein on skeletal muscle cell membrane
  • influx of Na+ causes depolarisation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

explain the role of Ca2+ in muscle contraction

A
  • action potential moves through t-tubules in the sarcoplasm, ca2+ channels in sarcoplasmic reticulum open
  • ca2+ binds to troponin, triggering conformational change in tropomyosin
  • exposes binding sites on actin filaments so actinomyosin bridges can form
17
Q

outline the role of ATP and phosphocreatine in muscle contraction

A
  1. phosphocreatine
    • phosphate group is from phosphocreatine is removed and added to adp to synthesise atp
    • cells store phosphocreatine, it is a short and simple reaction so fastest way to create atp
    • phosophocreatine is used up quickly so is used for high intensity and short duration
    • anaerobic process
    • alactic process (no lactic acid produced)
  2. anaerobic respiration (glycolysis)
    • 2x ATP made by glycosis
    • pyruvate is converted into lactate (causes muscle fatigue)
    • short duration, high intensity
  3. aerobic respiration
    • lots of atp mostly by oxidative phosphorylation
    • slow, requires many reactions but no harmful waste products
18
Q

where are slow and fast-twitch muscle fibres found in the body

A
  • slow twitch: sites of sustained contraction e.g calf muscle
  • fast twitch: sites of short-term, rapid powerful contraction e.g biceps
19
Q

explain the role of slow and fast-twitch muscle fibres

A
  • slow-twitch: long-duration contraction, well-adapted to aerobic respiration to prevent lactate buildup
  • fast-twitch: powerful short-term contraction, well-adapted to anaerobic respiration
20
Q

explain the structure and properties of slow-twitch muscle fibres

A
  • glycogen store: many terminal ends can be hydrolysed to release glucose for respiration
  • contain myoglobin: higher affinity for oxygen than haemoglobin at lower partial pressures
  • many mitochondria: aerobic respiration produces more atp
  • surrounded by many blood vessels: high supply of oxygen and glucose
  • darker in colour

biology (46 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions