Lecture 5 - Muscles pt. 1

Question 1

cardiac muscle
-look
-control
-speed

Answer 1

-striated
-involuntary pacemaker
-neural input can increase/decrease

Question 2

skeletal muscle
-look
-control
-speed

Answer 2

-striated
-voluntary
-can go fast, tire easily

Question 3

smooth muscle
-look
-control
-speed

Answer 3

-non-striated
-involuntary
-slow but sustained

Question 4

Muscle functions (4) + example

Answer 4

-movement = all
-posture = fight gravity
-stabilize = joints
-heat = body temp

Question 5

What are the 4 functional characteristics of the muscle?

Answer 5

-excitability = receive/respond stimulus
-contractability = shorten forcibly
-extendability = stretch/ extend
-elasticity = resume shape

Question 6

What are myofibrils made of?
=part

Answer 6

= sarcomere (1 z-disk to another)

= myofilaments
-actin (thin - I)
-myosin (think - A)

= z-disk (anchors)

= M zone (no thin filaments)

= M line (fine strands)

Question 7

Thick filament
-properties

Answer 7

-myosin molecules
-ATP binding sites

Question 8

Thin filaments
-properties

Answer 8

-2 actin strands in helix
-troponin
-tropomyosin

Question 9

Muscle contraction
- 6 steps

Answer 9

1. Ca2+ released from the sarcoplasmic reticulum
2. Ca2+ bind to troponin
3. troponin conformational change, more tropomyosin to uncover binding sites
4. cross-bridge formation (phosphate release, myosin attach)
5. power stroke (ADP release)
6. recovery stroke (ATP bind, myosin release)

Question 10

Rigor Mortis

Answer 10

-muscle stiffens as no ATP made means, no myosin let go

Question 11

What is the position of sarcolemma when the muscle is relaxed?

Answer 11

slight overlap of thick and thin

Question 12

What is the position of the sarcolemma when the muscle is contracted?

Answer 12

the thin filaments slide over into A band while Z-disks are pulled closer together

Question 13

What are the muscles constricted to in percent?

Answer 13

60-175% of the length that produces optimal strength

Question 14

How much muscle shortening occurs on average for 1 single power stroke?

Answer 14

1%

Question 15

sarcoplasmic reticulum

Answer 15

-a web of endoplasmic reticulum which wraps around the myofibril
-regulates and releases Ca2+

Question 16

T-tubules

Answer 16

-transverse tubules at A-I junctions to create hollow tube
-allow depolarization everywhere

Question 17

Triad

Answer 17

compromised of 3 structures
-terminal cisternae
-t-tubule
-terminal cisternae

Question 18

What are the events leading to a contraction and where do they happen?
=where
-what

Answer 18

=neromuscular junction
-motor neuron fires AP
-axon terminal releases Ach
-Ach binds to the receptor

=muscle fibre excitation
-AP in the sarcolemma

=excitation-contraction coupling
-travel down t-tubule
-sarcoplasmic reticulum releases Ca2+
-filaments start sliding

=cross-bridge cycle
-a contraction by cross-bridge cycling

Question 19

Isotonic contraction

Answer 19

-peak tension + low resistance = decrease rest + short muscle

Question 20

isometric contraction

Answer 20

-peak tension + high resistance = 100% rest + no shorten

Question 21

What is the air supply during muscle contraction?
=kind
-info
-time
-need o2?

Answer 21

=direct phosphorylation
-creatine phosphate (CP) + ADP = creatine + 1 ATP
-15 secs
-anaerobic

=anaerobic
-glucose = glycolysis + pyruvic acid + lactic acid = 2ATP + lactic acid
-30-40 secs
-anaerobic

=aerobic
-glucose = glycolysis + pyruvic acid + aerobic respiration = 32 ATP + O2 + CO2
-hours
-aerobic