Human Physiology - Lecture 13: Muscles

Question 1

Types of Muscle Tissue

Answer 1

Skeletal, Cardiac & Smooth muscles

Question 2

Muscles are attached to bone via

Answer 2

tendons

Question 3

Muscles contract or pull only in one direction, so we always have them paired as flexor/extensor muscles

Answer 3

True

Question 4

Muscle Structure

Answer 4

Muscle fibers are long, cylindrical, multinucleated cells

Each fiber is sheathed in connective tissue and then bundled with other fibers to create muscle fascicles

Question 5

Fiber —–> (connective tissue) ——> fascicles

Answer 5

True.

This connective tissue sheath is continuous with the tendon’s connective tissue, and contains blood vessels

Question 6

Sarcolemma

Answer 6

= cell membrane or plasmalemma. The equivalent of Plasma membrane in a regular cell structure

Outer surface of sarcolemma is attached to collagen fibers in tendons or aponeurosis

Question 7

Sarcoplasm

Answer 7

= cytoplasm

Question 8

Transverse tubules (t-tubules)

Answer 8

are a continuation of the sarcolemma, and are capable of transmitting action potentials.

Question 9

Sarcoplasmic reticulum

Answer 9

Endoplastic recticulum

Question 10

Muscle fiber parts in short

Answer 10

R-R-R-T

Question 11

Sarcomeres

Answer 11

functional unit (contractal unit)of a muscle fiber.

Question 12

Sarcolemma, similar to the plasma membrane, delimits…

Answer 12

Muscle fibers

Question 13

Myofibrilles are attached to…

Answer 13

Sarcolemma

Question 14

The Triad

Answer 14

Junction between myofibrils?

Question 15

Draw and label a sacromere

Answer 15

show A-band, thick filament, thin filament, tintin, M-line, H-band, z-line

Question 16

Thin Filaments:

Answer 16

Made of actin. A long chain of actin

Question 17

Filamentous (F) actin

Answer 17

twisted strand of parallel 300-400 G-actin monomers

Question 18

Tropomyosin

Answer 18

covers active sites on G-actin, that can bind myosin

Question 19

G-actin;

Answer 19

Actin monomers

Question 20

Nebulin:

Answer 20

holds actin

Question 21

Titin

Answer 21

Elastic protein

From Z-line to thick filaments

Keeps thick and thin f. aligned

Resist extreme expansion

Helps relaxation

Question 22

Structure of Thick Filaments

Answer 22

Made up of Myosin molecules. 300 in parallel array.

Thick Filaments:

Myosin molecules (300) in parallel array

Myosin head binds to tail through a hinge

Head interacts with active site in actin

Hinge bends (ATP), sliding the thin filament over the thick filament

Question 23

During Muscle Contraction…

Answer 23

Muscle fibers become shorter.

Question 24

The Neuromuscular Junction

Answer 24

check notebook

Question 25

Excitation-Contraction Coupling

Answer 25

1. Action potential arrives to transverse tubules. 2. Voltage-gated calcium channels located at terminal cisternae of the sarcoplasmic reticulum release calcium. 3. Calcium concentration increases x100. 4. Sarcomeres contract.

Question 26

Myasthenia gravis is produced by autoimmune antibodies that recognize and block the acetylcholine receptor. What effect do you expect this disease to have on muscle contraction?

Answer 26

The motor end plate will no longer be able to generate an action potential, so muscle contraction will be impaired.

Question 27

A single motor neuron will trigger contraction of…

Answer 27

An entire muscle

Question 28

Upon arrival of an action potential the terminal cisternae release Ca2+ into the______.

Answer 28

Sarcoplasm

Question 29

Triad

Answer 29

= Terminal cisternae | T-tubule | Terminal cisternae. Terminal cisternae = bulges formed by sacropalsmic recticulum its a sandwich.

Question 30

Contraction Cycle (I)

Answer 30

1) Calcium ions arrive to the zone of overlap between thin and thick filaments 2) - Calcium ions bind troponin. - Troponin-tropomyosin changes position, uncovering active sites in actin. - Actin interacts with energized (ATP) myosin heads. 3) - Actin interacts with energized (ATP) myosin heads. 4) – Myosin head pivots towards M line in a “power stroke”. - ADP and phosphate are released. 5) New ATP binds, myosin head releases actin. 6) Myosin head energizes again by splitting ATP into ADP and P. A new cycle begins…

Question 31

One contraction cycle in a sarcomere requires _______.

Answer 31

As many molecules of ATP as myosin heads are present in that sarcomere.

Question 32

During relaxation sarcomers ______.

Answer 32

Require no ATP because relaxation is passive.