Tri B - The Cardiac System

Question 1

Describe the structure of veins and arteries

Answer 1

Tunica Intima - epithelia
Tunica Media - smooth muscle
Tunica Externa - connective tissue

Question 2

Describe arteries

Answer 2

Thick walled
High pressure
Mostly oxygenated blood
Some contain elastic tissue, some muscle

Question 3

Describe elastic arteries

Answer 3

Function - maintain forward flow during relaxation
- As blood is pumped, arteries are stretched
- They later recoil, pushing blood forward

Question 4

Describe arterioles

Answer 4

Small arteries - well defined smooth muscle
Contraction - Vasoconstriction
Relaxation - Vasodilation
Functions 1.Controls blood flow to capillaries
2. Major influence on blood pressure

Question 5

Describe capillaries

Answer 5

Site of oxygen and nutrient exchange
Blood flow is slow and low pressure
Pre-capillary sphincter controls blood flow

Question 6

Describe venules and veins

Answer 6

Thin walled
Blood at low pressure
Large volume of blood - ~60%
Gravity hinders blood flow in lower limbs
Valves are present in veins

Question 7

Describe some factors effecting venous return and the impact it has

Answer 7

Muscle activity = +
Breathing = +
Blood pressure gradient = +
Gravity = -

Question 8

What is the function of the heart?

Answer 8

Pumps blood to tissues
Supplies oxygens and nutrients

Question 9

Describe the structure of the heart

Answer 9

2 halves - both have an atria and ventricle
Composed of cardiac muscle
~12cm
Own blood supply - coronary artery

Question 10

Name the heart valves

Answer 10

A-V valves
1. Tricuspid - right side
2. Mitral - left side
Semi-lunar valves
3. Pulmonary - right side
4. Aortic - left side

Question 11

Describe cardiac muscle

Answer 11

Known as myocardium
Cells are short and branched
Joined at intercalated discs - contain gap junctions - allow AP spread
Many mitochondria

Question 12

Describe blood supply to the heart

Answer 12

Receives blood from coronary arteries
- Branch extensively
- Areas receive blood from multiple arteries
- reduce risk of lack of oxygen

Question 13

Describe autonomic innervation of the heart

Answer 13

Supplied by both para and sympathetic systems
Both can affect heart rate
Sympathetic NS can alter strength of cardiac muscle - increase contractility

Question 14

Describe the cardiac pacemaker

Answer 14

Muscle must be depolarised before contraction
AP produced by sino-atrial node
Membrane potential constantly changing

Question 15

Describe the spread of electrical activity through the heart

Answer 15

Sino atrial node
–> Av node
–> bundle of HIS
–> Left and right branches
–> Purkinje fibres

Question 16

Name and describe the components of an ECG wave

Answer 16

P-wave - atrial depolarisation
QRS-complex - ventricular depolarisation
T-wave - repolarisation of ventricles