Functional Structure Of Heart

Question 1

Mention importance of inelastic nature of percardium

Answer 1

Prevent sudden heart dilatation, but it allows for physiological variation in cardiac size.

Question 2

Pericardium can adapt to slow stretch during ….

Answer 2

Growth or cariac hypertrophy

Question 3

Functions of A-V ring

Answer 3

1. Cardiac skeleton for origin & insertion for cardiac muscles with atrial above & ventricular below.
2. Electric insulator between atria & ventricles. It is pierced by A-V bundle.

Question 4

Describe the left venticular aid, is the opposite true?

Answer 4

When there is failure of right ventricle, healthy left ventricle can give an aid to RV, where its contraction will pull upon the free trangular RV wall & compress blood within its chamber against thick IV septum, thus raising pressure inside RV.
There is no RV aid.

Question 5

Mention important of junction of cardiac muscle fibers

Answer 5

Gap junctions

Desmosomes

Question 6

Mention important proteins in skeletal msucles

Answer 6

Myosin, actin, tropomyosin & troponin

Question 7

T tubeles contain …., which are …..

Answer 7

Dihydropyridine receptors

Voltage-gated Ca++ channels

Question 8

Terminal cisternae has …., which is ….

Answer 8

Ryandodine receptors

Ca++ release channels

Question 9

Function of T-tubule

Answer 9

Rapid spread of excitation wave from surface membrane deep into interior of the muscle fiber.

Question 10

Describe Ca++ indiced Ca++ release

Answer 10

When DHP receptors are activated, the Ca++ entered though it from the ECF triggers the release of Ca++ from cisterns of SR via ryanodine receptors.

Question 11

What is meant by: the heart is a functional syncytium?

Answer 11

Acts as a single unit & doesn’t have multiple units unlike skeletal muscle motor units, thus to a thershold stimulus it responds fully, but with subthershold there is no response. All or none rule.

Question 12

Mention structures that allow heart to act AS IF it is a true syncytium & their functions

Answer 12

Gap junction: allow high electric conduction with low resistance (1/400 of the normal) (electric syncytium)
Desmosomes: strong mechanical attachments between adjacent cell membranes. (Mechanical syncytium)

Question 13

Mention cardiac characteristics which allow aerobic metabolism dominance.

Answer 13

Abundant blood supply
Hight content of myoglobin
Numerous and large elongated mitochondria

Question 14

GR: Cardiac action potential is not initiated by the neural activity

Answer 14

There is specialized muscle tissue which initiates its own action potential (autorhythmic tissue cells) which then spreads by the conductive tissue cells to contractile cells.

Question 15

Write a short note on nodal tissue

Answer 15

SAN & AVN

Specialized in initiation of the excitation wave at a regular rhythm

Question 16

Write a short note on junctional tissue

Answer 16

His bundle, Rt & Lt bundle branches & Purkinje fibers

Specialized system for conduction of the excitation waves ti the rest of the heart as fast as possible.

Question 17

Write a short note on contractile tissue

Answer 17

Atrial muscle & ventricular muscle

Its ability to contract and act as a pump