skeletal muscles Flashcards
(54 cards)
1
Q
describe the role of muscles
A
- act in antagonistic pairs
- against an incompressible skeleton
- creating movement
- part of reflex or controlled by conscious thought
2
Q
what is a myofibril?
A
- fused cell
- shares a nucleus & cytoplasm (sarcoplasm)
- has many mitochondria
- membrane bound channels (sarcoplasmic reticulum)
3
Q
what are myofibrils made up of?
A
myosin and actin proteins forming a sarcomere
4
Q
describe the myosin proteins
A
thick protein filament
5
Q
describe the actin proteins
A
thin protein filament
6
Q
describe the position of the sarcomere proteins
A
each myosin filament surrounded by six actin filaments
7
Q
what is the sliding filament theory?
A
when an action potential reaches a muscle, it stimulates the response
8
Q
first stage of sliding filament
A
Ca2+ ions enter and cause trypomyosin to move and uncover binding sites
9
Q
describe the position of the trypomyosin
A
- wrapped around actin protein
- blocks binding sites for myosin head when muscle is relaxed
10
Q
second stage of sliding filament
A
- ADP is attached to myosin head
- myosin head binds to binding site on actin, forming a cross bridge
11
Q
third stage of sliding filament
A
- angle created in cross bridge creates tension
- actin filament is pulled and slides along the myosin
- releasing ADP
12
Q
fourth stage of sliding filament
A
- ATP molecule binds to myosin
- causes it to change shape and detach from actin
13
Q
fifth stage of sliding filament
A
- Ca2+ ions activate enzyme ATPase in sarcoplasm
- ATPase hydrolyses ATP on myosin head into ADP and releases enough energy for myosin head to return to original position
14
Q
what happens when aerobic respiration cannot create enough ATP to meet the demand?
A
- anaerobic respiration
- phosphocreatine which is stored in muscles, provides phosphate to regenerate ATP from ADP
15
Q
what does the I band show?
A
only actin
16
Q
what does the A band show?
A
total width of myosin
17
Q
what does the H zone show?
A
only myosin
18
Q
what is the M line?
A
middle point of myosin
19
Q
what is the Z line?
A
the point where actin filaments attach to each other
20
Q
how do micrographs show thick and thin filament?
A
actin is paler and myosin is darker
21
Q
what happens to the I band during muscle contraction?
A
decreases
22
Q
what happens to the H zone during muscle contraction?
A
decreases
23
Q
what happens to the A band during muscle contraction?
A
nothing
- myosin isn’t moving
24
Q
what happens to the Z lines during muscle contraction?
A
they slide closer together, shortens the sarcomere
25
describe the structure of slow twitch fibres
- small diameter
- contains a large store of myoglobin, rich blood supply and many mitochondria
- red due to containing a lot of myoglobin
26
where are slow twitch fibres located?
calf muscles
27
what are the general properties of slow twitch fibres?
- slower contraction
- aerobic respiration for long periods of time due to rich blood supply and myoglobin O2 store
- adapted for endurance work
28
describe the structure of fast twitch fibres
- larger diameter
- more myosin filaments
- large store of glycogen, store of phosphocreatine to help make ATP from ADP
- high conc of enzymes involved in anaerobic respiration
29
where are fast twitch fibres located?
biceps
30
describe the general properties of fast twitch fibres
- fast contraction
- provides short bursts of powerful contraction
- adapted for intense exercise
31
explain why muscle fibres contain many mitochondria (2)
- they produce ATP during aerobic respiration
- ATP is needed to provide energy for muscle contraction
32
suggest the advantage of having myoglobin in slow twitch muscle fibres (3)
- acts as an oxygen store
- allows muscle fibre to respire aerobically
- even when blood can't supply enough oxygen directly
33
what is the sarcomere?
distance between 2 Z lines
34
describe the structure of skeletal muscle (3)
- made up of bundles of muscle fibres
- each fibre made up of bundles of myofibrils
- myofibrils made up of actin and myosin protein filaments
35
name the protein present in the I band
actin
36
name the proteins present in the A band
actin and myosin
37
name the protein present in the H zone
myosin
38
when the sarcomere contracts, what happens to the I, A and H band/zone?
I gets shorter
A stays the same
H gets shorter or disappears
39
describe the role played by Ca2+ in the contraction of striated muscle (3)
- released from sarcoplasmic reticulum
- binds to troponin
- troponin changes shape
- tropomyosin moves so myosin binding site is exposed
- myosin head binds to actin
40
describe the role of ATP in muscle contraction
- broken down by ATPase
- provides energy to move myosin head which pulls actin filament
- provides energy to break cross bridge so that myosin head detaches from actin
- used up very quickly so has to be continuously generated
41
describe aerobic respiration as energy production for muscle contraction
- most ATP generated via oxidative phosphorylation in cell mitochondria
- aerobic reps only works when oxygen is present
- good for long periods of low intensity exercise
42
describe aerobic respiration as energy production for muscle contraction
- ATP is made rapidly by glycolysis
- end product is pyruvate which is converted to lactate
- lactate can quickly build up in muscles and cause muscle fatigue
- good for short periods of intense exercise
43
describe ATP CP system as energy production for muscle contraction
- ATP is made by phosphorylating ADP
- creatine phosphate is stored inside cells and the system generates ATP quickly
- CP runs out after a few seconds
- good for short bursts of vigorous exercise
- anaerobic & lactic
44
give one advantage and one disadvantage of generating ATP via the ATP creatine phosphate system
+ quick
+ used for short bursts of vigorous exercise
+ don't require oxygen
- not long lasting
45
describe the function of skeletal muscle
- contraction is controlled consciously
- made of muscle fibres that contract quickly or slowly
46
describe the structure of skeletal muscle
- alternating shade colour stripes: A and I bands
- long muscle fibres
- many nuclei in each muscle fibre
47
describe the function of smooth muscle
- involuntary
- controlled unconsciously
- contract slowly
48
describe the structure of smooth muscle
- no striped appearance
- found in the walls of hollow internal organs
- one nucleus in muscle fibres
- spindle shaped muscle fibres
49
describe the function of the cardiac muscle
- contracts on its own (myogenic)
- pumps blood around the body
- contract rhymically and don't fatigue
50
describe the structure of the cardiac muscle
- found in heart walls
- made of muscle fibres connected by intercalated discs
- low electrical resistance so nerve impulses pass easily between cells
- muscle fibres are branched to allow nerve impulses to spread quickly
- each cardiac muscle has 1 nucleus
- muscle fibres are shaped like cylinders
51
describe the similarities between all 3 muscle types
- contains actin and myosin which interact to bring about contraction
- antagonistic pairs ( eg one contracts whilst other elongates)
52
what is an EMG?
electromyogram
53
what does an EMG look at?
electrical impulses to muscles
- motor neurone activity
54
how does an EMG work?
- electrical signals in muscles can be detected by electrodes on the skin
- electrodes connected to a computer
