1. Smooth Muscle Characteristics Types Not striated
Dense bodies instead of Z disks as in skeletal muscle
Have noncontractile intermediate filaments
Ca2+ required to initiate contractions
Types
Visceral or unitary
Function as a unit
Multiunit
Cells or groups of cells act as independent units

3. Smooth Muscle Contraction

4. Electrical Properties of Smooth Muscle

5. Functional Properties of Smooth Muscle
Some visceral muscle exhibits autorhythmic contractions
Tends to contract in response to sudden stretch but no to slow increase in length
Exhibits relatively constant tension: Smooth muscle tone
Amplitude of contraction remains constant although muscle length varies

6. Smooth Muscle Regulation
Innervated by autonomic nervous system
Neurotransmitter are acetylcholine and norepinephrine
Hormones important as epinephrine and oxytocin
Receptors present on plasma membrane which neurotransmitters or hormones bind determines response

9. Cardiac Muscle Found only in heart Striated
Each cell usually has one nucleus
Has intercalated disks and gap junctions
Autorhythmic cells
Action potentials of longer duration and longer refractory period
Ca2+ regulates contraction

10. Cardiac Muscle
Elongated, branching cells containing 1-2 centrally located nuclei
Contains actin and myosin myofilaments
Intercalated disks: Specialized cell-cell contacts
Desmosomes hold cells together and gap junctions allow action potentials
Electrically, cardiac muscle behaves as single unit

12. Cardiac myocyte action potential:

13. Refractory Period
Absolute: Cardiac muscle cell completely insensitive to further stimulation
Relative: Cell exhibits reduced sensitivity to additional stimulation
Long refractory period prevents tetanic contractions

14. AP-contraction relationship:
AP in skeletal muscle is very short-lived
AP is basically over before an increase in muscle tension can be measured.
AP in cardiac muscle is very long-lived
AP has an extra component, which extends the duration.
The contraction is almost over before the action potential has finished.

15. Functions of the Heart Generating blood pressure Routing blood
Heart separates pulmonary and systemic circulations
Ensuring one-way blood flow
Heart valves ensure one-way flow
Regulating blood supply
Changes in contraction rate and force match blood delivery to changing metabolic needs

17. Orientation of cardiac muscle fibres:
Unlike skeletal muscles, cardiac muscles have to contract in more than one direction.
Cardiac muscle cells are striated, meaning they will only contract along their long axis.
In order to get contraction in two axis, the fibres wrap around.

18. Circulation circuits:

21. Heart Wall Three layers of tissue
Epicardium: This serous membrane of smooth outer surface of heart
Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting
Endocardium: Smooth inner surface of heart chambers

26. Valve function:

28. Coronary circulation:

29. Pacemaker potential:

30. Cardiac conducting system:

33. EKG:

34. Heart Sounds First heart sound or “lubb” Second heart sound or “dupp”
Atrioventricular valves and surrounding fluid vibrations as valves close at beginning of ventricular systole
Second heart sound or “dupp”
Results from closure of aortic and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer
Third heart sound (occasional)
Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

35. Heart sounds:

36. Cardiac Arrhythmias Tachycardia: Heart rate in excess of 100bpm
Bradycardia: Heart rate less than 60 bpm
Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration
Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

37. Mean Arterial Pressure (MAP)
Average blood pressure in aorta
MAP=CO x PR
CO is amount of blood pumped by heart per minute
CO=SV x HR
SV: Stroke volume of blood pumped during each heart beat
HR: Heart rate or number of times heart beats per minute
Cardiac reserve: Difference between CO at rest and maximum CO
PR is total resistance against which blood must be pumped

38. Pressure relationships:

39. Cardiac Cycle
Heart is two pumps that work together, right and left half
Repetitive contraction (systole) and relaxation (diastole) of heart chambers
Blood moves through circulatory system from areas of higher to lower pressure.
Contraction of heart produces the pressure

41. Factors Affecting MAP

42. Regulation of the Heart
Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation
Starling’s law of the heart
Extrinsic regulation: Involves neural and hormonal control
Parasympathetic stimulation
Supplied by vagus nerve, decreases heart rate, acetylcholine secreted
Sympathetic stimulation
Supplied by cardiac nerves, increases heart rate and force of contraction, epinephrine and norepinephrine released

43. Heart Homeostasis Effect of blood pressure
Baroreceptors monitor blood pressure
Effect of pH, carbon dioxide, oxygen
Chemoreceptors monitor
Effect of extracellular ion concentration
Increase or decrease in extracellular K+ decreases heart rate
Effect of body temperature
Heart rate increases when body temperature increases, heart rate decreases when body temperature decreases

44. Baroreceptor and Chemoreceptor Reflexes