Muscle Physiology III

Question 1

Cardiac muscle cells

Answer 1

• Cylindric, branched cells
• AUTOMATICITY
• intercalated discs

Question 2

Intercalated discs:Transverse components

Answer 2

➢ Fascia adherens

➢ Desmosomes

Question 3

Intercalated discs-Lateral components

Answer 3

➢ Gap junctions

Question 4

Cardiac muscle -Long Action Potential with long

Refractory Period.

Answer 4

No temporal summation

• No tetanic contraction

Question 5

Cardiac muscle-GAP junctions

Answer 5

all cells are
interconnected
• No spatial summation

Question 6

Starling law of the heart

Answer 6

the stroke volume of the left ventricle will increase as the left ventricular volume increases due to the myocyte stretch causing a more forceful systolic contraction

Question 7

inc. in Ca++=

Answer 7

CONTRACTION

Question 8

T-tubule

Answer 8

extension of cell membrane into the cell

Contain Ca++

Question 9

Voltage-gated L-type 1,4 dihydropyridine receptor

Answer 9

Open the channel when an action potential stimulates the receptor

Question 10

Sarcoplasmic reticulum

Answer 10

Form DIAD

• Store Ca++

Question 11

RyR-2

Answer 11

Is stimulated by Ca++

• Release Ca++ from SR

Question 12

Calcium “spark”

Answer 12

calcium released by RyR from SR
as result of the Ca++
-induced Ca++ release “CICR”

Question 13

what type o Ca++ is ESSENTIAL in cardiac muscle contraction

Answer 13

Extracellular Ca++

Question 14

COMMON PATHWAY IN STRIATED MUSCLE CONTRACTION

Answer 14

Ca++ binds TROPONIN C TROPOMYOSIN moves away from myosin-binding
sites on the actin CROSSBRIDGE –muscle contraction

Question 15

80% Ca++ reuptake into-

Answer 15

SR:

• SERCApump

Question 16

20% Ca++ extruded into the-

Answer 16

extracellular fluid:
• Na+/Ca++ exchanger
• Ca++ATPase pump)

Question 17

Thick filaments:

Answer 17

• MYOSIN II

Question 18

Thin filaments:

Answer 18

ACTIN
• TROPONIN (only in striated muscle)
• TROPOMYOSIN

Question 19

Regulatory protein–Striated muscle

Answer 19

TROPONIN

Question 20

Regulatory proteins-Non-striated muscle

Answer 20

CALMODULIN

Question 21

Inotropism

Answer 21

the ability of the myocardial cells to change the force/strength of contraction
at the level of the cell and this modification can occur independently of any change in
force caused by alterations in preload or afterload on the heart

Question 22

Anrep effect

Answer 22

abrupt increase in afterload produces a modest increase in inotropy

Question 23

Bowditch effect

Answer 23

(increase in heart rate produces a small (+) inotropic effect

Question 24

Gs-protein linked receptors:

Answer 24

Stimulate muscle contractility

• Beta-1 receptors

Question 25

Gi-protein linked receptors:

Answer 25

• M2 receptors
Gi-protein activation predominates in the SA node
and in the AV node where the activation produce
decrease Heart Rate and Conduction Velocity

Question 26

Gq-Protein and IP3- Coupled

Answer 26

Signal Transduction

Question 27

+) Inotropic Drugs–Beta agonists: Gs-Protein linked receptors

Answer 27

• Dopamine
• Dobutamine
• Epinephrine

Question 28

(+) Inotropic Drugs-Milrinone

Answer 28

Phosphodiesterase inhibitors: increase cAMP

Question 29

Digoxin

Answer 29

-Cardiac glycoside.
-Direct inhibition of Na+/K+ATPase,
-decreases the
gradient of Na+ and
-indirectly inhibits Na+/Ca++
exchanger

Question 30

Clinical use-Digoxin

Answer 30

Systolic Heart

Failure

Question 31

Smooth muscle

Answer 31

-Non-striated pattern NO SARCOMERE

-

Question 32

Smooth muscle-Caveola

Answer 32

Analogue to T-tubule

Extracellular Ca++

Question 33

Smooth muscle-Sarcoplasmic reticulum

Answer 33

Poor developed

Intracellular Ca++

Question 34

Smooth muscle–Dense bodies

Answer 34

(α-actinin; analogous to Z-lines in striated muscles

-Intermediate filaments (desmin & vimentin)

Question 35

Smooth muscle-Thin filaments

Answer 35

Actin + Caldesmon + Calponin + Tropomyosin
Lack TROPONIN (regulation in striated muscle contraction)

Question 36

Smooth muscle-Thick filaments

Answer 36

Myosin II

Question 37

Smooth muscle-Actomyosin regulation

Answer 37

Thick filament:
phosphorylation of the
regulatory light chain of
Myosin II (myosin-linked
regulation) –Ca++/CaM
mediated

Question 38

Smooth muscle-muti eg.

Answer 38

Ciliary muscle of the eye
• Sphincter pupillae muscle
• Dilator pupillae muscle
• Piloerector muscles