Physio (Rhythmical Excitation of the heart)

Question 1

Abnormal Paceakers –“Ectopic” Pacemaker

Answer 1

pacemaker elsewhere than the sinus node; called an “ectopic” pace maker

Question 2

What Causes?

• abnormal sequence of contraction
• can cause feeble heart pumping

Answer 2

ectopic pacemaker

Question 3

causes?

• blockage of transmission
• from sinus not to other parts of the heart

Answer 3

shift

Question 4

Syndrome

-delayed pickup of heartbeat

Answer 4

Stokes Adams syndrome

Question 5

Supplied by:

• sympathetic nerves
• parasympathetic nerves

Answer 5

the Heart

Question 6

-the Vagi

Answer 6

Parasympathetic

Question 7

Distributed to:

• SA nodes
• AV nodes

Answer 7

Vagi

Question 8

• distributed to all parts of the heart

- stron representation to ventricular muscle

Answer 8

sympathetic nerves

Question 9

• causes release of acetylcholine

hormone

Answer 9

stimulation of. parasympathetic nerves

Question 10

2 major effects this are:

• decreases rate of rhythm of the sinus node
• decreases the excitability of the AV junctional fibers between the atrial musculature & AV node

Answer 10

acetylcholine

hormone

Question 11

what causes vagi to:

• stop completely
  (rhythmical excitation by sinus node)

-block completely transmission of cardiac impulse
(atria into ventricles through the A-V node)

Answer 11

strong stimulation

Question 12

• ventricles stop beating for 5 to 20 seconds
• develops a rhythm of its own
• causes ventricular contraction at a rate of 15 to 40 beats/minute

Answer 12

ventricles stop beating; CALLED ventricular escape

Question 13

• released at vagal nerve endings

- increases (greatly) permeability of membranes to K+

Answer 13

acetylcholine

Question 14

• increased negativity inside the fibers

- makes tissues much less excitable

Answer 14

hyperpolarization

Question 15

-state of hyperpolarization

-decreases “resting” membrane potential of sinus nodal fibers
more negative than usual

Answer 15

sinus node

Question 16

caused by

• sodium leakages
• calcium leakages
• requires much longer reach the threshold potential for excitation

Answer 16

initial rise of sinus nodal membrane potential

Question 17

• caused by vagal stimulations

- makes it difficult for small atrial fibers to excite nodal fibers

Answer 17

hyperpolarization

Question 18

-moderate decrease

rate of rhythmicity

Answer 18

delays conduction

Question 19

-large decrease

rate of rhythmicity

Answer 19

blocks conduction

entirely

Question 20

• opposite effects on heart, compared to vagal stimulation

- increases overall activity of the heart

Answer 20

sympathetic stimulation

Question 21

• increases rate of sinus nodal discharge
• increases rate of conduction/level of excitability in all options of the heart

-increases force of contraction of all cardiac musculature
(atrial & ventricular)

Answer 21

effects of sympathetic stimulation on cardiac rhythm & conduction

Question 22

• triple frequency of heartbeat

- increase the strength of heart contraction (2x)

Answer 22

maximal stimulation

Question 23

-norepinephrine released
(hormone)

• at sympathetic nerve endings
• increases permeability of the fiber membrane to Na and Ca ions

Answer 23

stimulation of sympathetic nerves

Question 24

• in Sinus node

- causes increase of the heart rate

Answer 24

increase of Na-Ca permeability

Question 25

• in AV node & AV bundle

- conducting fiber bundles are easily excited?

Answer 25

increased sodium-calcium permeability