Cardiovascular System Flashcards 2

Questions and Answers

What is the sinoatrial node and what is its function?

The sinoatrial (SA) node is a section of nodal tissue located in the upper wall of the right atrium; it sets the rate of contraction for the heart by generating nerve impulses that cause both atria to contract.

Name the chambers of the heart.

Right atrium, left atrium, right ventricle, left ventricle.

Describe the effect on cardiac function of decreased core body temperature.

Decreased core body temperature reduces excitability of the sinoatrial node, leading to a reduced rate of impulse generation, weaker muscle contraction, and a fall in heart rate and stroke volume.

Describe the stages of the cardiac cycle and the order of contraction of the chambers of the heart.

<ol> <li>Right and left atrial systole; 2. Right and left ventricular systole; 3. Relaxation period (atrial and ventricular diastole).</li> </ol> Signup and view all the answers

How is cardiac output calculated?

Cardiac output is calculated by multiplying stroke volume (mls/beat) by heart rate (beats/min). Signup and view all the answers

Calculate cardiac output per minute when the heart rate is 84 beats per minute and stroke volume is 80 ml.

The cardiac output is 6,720 mls/min (or 6.72 litres). Signup and view all the answers

Outline the functions of the autonomic nervous system (ANS).

The ANS controls involuntary activities in the body; it includes regulating functions like growth, reproduction, food and water intake, sleep, and temperature control. Signup and view all the answers

Describe the two divisions of the ANS and explain the acronym SLUDD.

The two divisions are the sympathetic system (responsible for stress responses) and the parasympathetic system (promotes rest and restoration). SLUDD stands for salivation, lachrymation, urination, digestion, and defecation. Signup and view all the answers

What neurotransmitter is released onto the sinoatrial node by the cardiac accelerator nerve, and what is its effect?

The cardiac accelerator nerve releases adrenaline and noradrenaline, increasing the excitability of the SA node and the heart rate. Signup and view all the answers

What neurotransmitter is released by the vagus nerve and what is its effect?

The vagus nerve releases acetylcholine, which inhibits the SA node, leading to a slower heart rate. Signup and view all the answers

Explain why the inherent rate of discharge of the S-A node is 100 impulses per minute, yet the resting heart rate of an adult is, on average, 72 beats/minute.

The resting heart rate is about 72 beats/minute because parasympathetic activity predominates, releasing acetylcholine that inhibits impulse generation in the SA node. Signup and view all the answers

Study Notes

Sinoatrial Node

Located in the upper wall of the right atrium, the sinoatrial (SA) node is known as the heart's pacemaker.
Functionally, it sets the heart's contraction rate by generating spontaneous nerve impulses that trigger atrial contraction.

Cardiac Function and Temperature

Decreased core body temperature reduces the excitability of the SA node.
This results in a lower rate of impulse generation and weaker muscle contractions.
Ultimately, both heart rate and stroke volume decrease.

Cardiac Cycle

The cardiac cycle consists of three main phases:
- Right and left atrial systole (contraction).
- Right and left ventricular systole (contraction).
- Relaxation period for both atria and ventricles (diastole).

Cardiac Output Calculation

Cardiac output can be calculated using the formula: Stroke volume (mls/beat) x Heart rate (beats/min) = Cardiac output (mls/min).

Cardiac Output Example

When the heart rate is 84 beats per minute and stroke volume is 80ml, the cardiac output is 6,720 mls/min (6.72 litres).

Autonomic Nervous System (ANS)

The ANS regulates involuntary bodily functions, including growth, reproduction, and temperature control, mediated by the hypothalamus.
It has two divisions:
- Sympathetic: coordinates stress responses.
- Parasympathetic: promotes rest and restoration.

Functions of the Two Divisions of ANS

The sympathetic system is tied to the four 'E' situations: exercise, excitement, emergency, and embarrassment.
'SLUDD' (salivation, lachrymation, urination, digestion, defecation) represents functions of the parasympathetic system.
Typically, when one division is active, the other is suppressed, adapting to information from sensory receptors and chemical signals.

Neurotransmitters and Cardiac Function

The cardiac accelerator nerve releases adrenaline and nor-adrenaline, increasing SA node excitability and heart contraction rate, enhancing stroke volume.
The vagus nerve releases acetylcholine, which inhibits the SA node, slowing the heart's rate of contraction.

Inherent Rate of SA Node vs. Resting Heart Rate

The SA node has an inherent rate of 100 impulses per minute, but the average resting heart rate for adults is about 72 beats/minute due to predominant parasympathetic activity inhibiting impulse generation.

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Description

Explore key concepts about the cardiovascular system with these flashcards. Learn about the sinoatrial node, its definition, and its crucial function in regulating heart contractions. Perfect for students studying human anatomy and physiology.