Heart Control

Question 1

Cardiac output

Answer 1

Volume of blood pumped by one ventricle of the heart in one minute (dm3min-1)

Question 2

Cardiac output depends upon

Answer 2

1) heart rate (bpm)

2) stroke volume

Question 3

Cardiac output

Answer 3

Heart rate x stroke volume

Question 4

Increasing cardiac outputs

Answer 4

Strong heart muscles with a higher stroke volume

Question 5

Pulse

Answer 5

• wave of pressure that pass along the arteries
• causes them to expand & recoil rhythmically
• not always same as heart rate, if heartbeat becomes irregular

Question 6

Myogenic contractions

Answer 6

When cardiac muscles are provided with O2, nutrients and mineral salts, they contract spontaneously (without nervous or hormonal stimulation)

Question 7

Sinoatrial node

Answer 7

Small patch of tissue which has its own inherent rhythm of contraction

Question 8

Cardiac impulses

Answer 8

Electrical impulses generated by the SA

Question 9

Chemoreceptors

Answer 9

• sensory receptors that detect changes in the concentration of chemicals in the blood (pH)
• found in the carotid and aortic sinuses and arteries
• act as transducers, transferring chemical energy into electrical energy; can be conducted as an action potential along a neurone

Question 10

Stretch receptors

Answer 10

• detect movement of the limbs
• located in the muscles
• transduce kinetic energy to electrical energy
• informs brain that more O2 may soon be needed

Question 11

Baroreceptors

Answer 11

• a type of stretch receptor
• detect changes in blood pressure that affect stretch of artery walls
• found in the walls of the carotid sinus

Question 12

Medulla oblongata

Answer 12

Contains the cardiorespiratory (cardiovascular) centre

Question 13

Autonomic nervous system

Answer 13

• responsible for controlling involuntary motor activities
• two divisions
i) sympathetic
ii) parasympathetic

Question 14

Sympathetic system

Answer 14

• excitatory
• accelerans nerve
• most active at times of stress
• uses noradrenaline
• increases heart rate
• dilates pupils
• increases ventilation rate
• reduces digestive activity

Question 15

Parasympathetic system

Answer 15

• inhibitory
• vagus nerve
• most active during sleep or relaxation
• uses acetylcholine
• opposite effects

Question 16

The process of cardiac control

Answer 16

1) sensory receptors (chemo, stretch) detect changes in internal/external environment
2) sensory neurones conduct electron impulses along the neuronal system to the medulla oblongata
3) medulla oblongata uses cell signalling through the autonomic nervous system to communicate with the sinoatrial node
4) the sinoatrial node effector changes the frequency of the initiation of the waves of excitation

Question 17

Venous return

Answer 17

• the volume of blood returning the heart
• causes variation in cardiac output
• high levels causes Bainbridge reflex and the Frank-Starling effect
• enables the heart to adjust strength and rate of contractions according to volume of blood passing through

Question 18

Bainbridge reflux

Answer 18

stretching of the walls of the right atrium, causing the heart to beat faster

Question 19

Frank-Starling effect

Answer 19

• stretching of the walls of the left ventricle, causing ventricles to contract more strongly
• gives a greater stroke volume