L23

Question 1

The contractile activity of cardiac muscle: (4)

Answer 1

• The regular beating of the heart is due to an intrinsic pacemaker activity of the heart.
• The contraction is therefore myogenic in origin.
• Cardiac muscle is supplied by nerve fibres that have their origin in the autonomic ganglia.
• Such nerves are called autonomic nerves and act to modulate the rate and force of the contraction of cardiac muscle.

Question 2

The pacemaker activity of the SA node can be

modulated by … - …..

Answer 2

autonomic nerves –

chronotropic regulation

Question 3

• Cardiac muscle is made up of …. cells linked together by ….. and connected electrically via gap junctions

Answer 3

discrete rod shaped

intercalated disks

Question 4

• The long plateau of the cardiac action potential is due to ….

Answer 4

Ca2+ influx through voltage-gated calcium channels.

Question 5

Przypomnienie:

Answer 5

• The cardiac action potential largely coincides with the contractile response so cardiac muscle cannot be tetanised.

Question 6

• The force with which cardiac muscle contracts is regulated by …..and by ….

Answer 6

the Frank-Starling mechanism (preload)

its inotropic state (intrinsic contractility)

Question 7

• Smooth muscle is the muscle found …..

Answer 7

in the walls of the hollow organs of the body and the blood vessels. It is also found in the eye.

Question 8

There are two main types of smooth muscle:

Answer 8

single unit smooth muscle and multi unit smooth muscle.

Question 9

In single unit smooth muscle the contractions are:

Answer 9

mainly myogenic in origin.

Question 10

In multi-unit smooth muscle the contractions are:

Answer 10

largely initiated by autonomic nerve fibres and are therefore neurogenic in origin.

Question 11

Smooth Muscle przypomnienie:

Answer 11

The loose arrangement of the contractile proteins allows a greater degree of shortening than seen in striated muscle

Question 12

Smooth Muscle przypomnienie:

Answer 12

The loose arrangement of the contractile proteins allows a greater degree of shortening than seen in striated muscle

Question 13

• Smooth muscle consists of …

Answer 13

sheets of spindle shaped cells.

Question 14

As the contractile proteins are not arranged in regular sarcomeres, there are …

Answer 14

no striations.

Question 15

• Smooth muscle can maintain a steady level of tension known as …. which is modulated by ……

Answer 15

tone

autonomic nerves, by local chemical factors (paracrine agents) and by circulating hormones.