E-C Coupling HeartLab

Question 1

Where are the electrical signals that control the heart generated from

Answer 1

the heart itself

Question 2

what is the heart able to do in the absence of stimuli and what is this called

Answer 2

beating rhythmically
auto-rhythm

Question 2

what is the structure of cardiac muscle

Answer 2

striated

Question 3

each muscle fibre (cell) contains many what

Answer 3

Myofibrils

Question 4

Each muscle fibre (cell) contains many myofibrils, these are the _________ units of the muscle

Answer 4

contractile

Question 5

the actin (thin filaments) causes what appearance in myofibrils and fibres

Answer 5

lighter

Question 6

the myocin (thick filaments) causes what appearance in myofibrils and fibres

Answer 6

darker

Question 7

within each myofibril: actin and myocin are arranged into what

Answer 7

sarcomeres

Question 8

which two junctions connect cardiac muscle cells

Answer 8

desmosomes and gap junctions

Question 9

there are no what in cardiac muscles

Answer 9

NMJs

Question 10

there are no NMJs in cardiac muscle but cardiac myocytes are electrically coupled by what

Answer 10

gap junctions

Question 11

Gap Junctions are protein channels which form low resistance electrical communication pathways between what

Answer 11

neighbouring myocytes

Question 12

Gap Junctions ensure that each electrical excitation reaches all the cardiac myocytes, what law is this known as

Answer 12

All or none law of the heart

Question 13

The desmosomes within the intercalated discs provide what between adjacent cardiac cells

Answer 13

mechanical adhesion

Question 14

Desmosomes ensure that the tension developed by one cell is what

Answer 14

transmitted to the next

Question 15

Myosin chains are composed of two heavy chains arranged in what structure

Answer 15

head and tail

Question 16

the myosin chains wrap around eachother to form what

Answer 16

double helix structure for the tail

Question 17

the free ends of the myosin chan form what

Answer 17

the head

Question 18

each myosin complex has _ light chains, two associated with each head

Answer 18

four

Question 19

several myosin chains from the myosin filament (the ______ filament)

Answer 19

thick

Question 20

the head (cross birdges) protrude from where

Answer 20

the arm

Question 21

The myosin heads will interact with what

Answer 21

the actin filaments

Question 22

what binding sites are available on the myosin head

Answer 22

ATP binding sites

Question 23

Actin is composed of how many F actin strands

Answer 23

two

Question 24

What forms the troponin complex

Answer 24

Troponin T Troponin I Troponin C

Question 25

how is the tropomyosin arranged around the actin

Answer 25

in a double helix

Question 26

G actin has the bind site for what

Answer 26

the myosin head

Question 27

In the troponin complex, the different troponins are attached to different structures: Troponin T: Troponin I: Troponin C:

Answer 27

Troponin T: tropomyosin Troponin I: G-actin Troponin C: contains the Ca2+ binding site

Question 28

In the absense of Ca2+, the binding site for myosin on actin are covered by what

Answer 28

Tropomyosin

Question 29

Ca2+ binds to Troponin C, changing what of the troponin complex

Answer 29

When CA2+ binds to the Troponin C, the complex of the troponin complex is changed

Question 30

When Ca2+ binds to Troponin C, the conformation change in the Tropnin complex pulls tropomyosin away from ______, exposing the myosin binding sites

Answer 30

G-actin

Question 31

When Ca2+ binds to Troponin C, the conformation change in the Tropnin complex pulls tropomyosin away from the G-actin, exposing what

Answer 31

the myosin binding sites