Textbook Question
Differentiate between stroke volume and cardiac output. How is cardiac output calculated?
1302
views
Ch. 20 The Heart
Martini, Nath, Bartholomew11th EditionFundamentals of Anatomy & PhysiologyISBN: 9780136874089
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch. 1 An Introduction to Anatomy and Physiology26
- Ch. 2 The Chemical Level of Organization34
- Ch. 3 The Cellular Level of Organization30
- Ch. 4 The Tissue Level of Organization24
- Ch. 5 The Integumentary System17
- Ch. 6 Bones and Bone Structure36
- Ch. 7 The Axial Skeleton11
- Ch. 8 The Appendicular Skeleton17
- Ch. 9 Joints13
- Ch. 10 Muscle Tissue12
- Ch. 11 The Muscular System28
- Ch. 12 Nervous Tissue18
- Ch. 13 The Spinal Cord, Spinal Nerves, and Spinal Reflexes22
- Ch. 14 The Brain and Cranial Nerves20
- Ch. 15 Sensory Pathways and the Somatic Nervous System17
- Ch. 16 The Autonomic Nervous System and Higher-Order Functions30
- Ch. 17 The Special Senses16
- Ch. 18 The Endocrine System20
- Ch. 19 Blood31
- Ch. 20 The Heart31
- Ch. 21 Blood Vessels and Circulation29
- Ch. 22 The Lymphatic System and Immunity31
- Ch. 23 The Respiratory System12
- Ch. 24 The Digestive System18
- Ch. 26 The Urinary System31
- Ch. 27 Fluids & Electrolytes32
- Ch. 28 The Reproductive System12
- Ch. 29 Development and Inheritance23
Martini, Nath, Bartholomew11th EditionFundamentals of Anatomy & PhysiologyISBN: 9780136874089Not the one you use?Change textbook
Chapter 20, Problem 27
Describe the effects of epinephrine, norepinephrine, glucagon, and thyroid hormones on the contractility of the heart.
Verified step by step guidance1
Step 1: Understand the concept of cardiac contractility, which refers to the strength and force of the heart's contractions independent of preload and afterload. Contractility is influenced by various hormones and neurotransmitters that affect calcium availability in cardiac muscle cells.
Step 2: Analyze the effect of epinephrine and norepinephrine, which are catecholamines released by the adrenal medulla and sympathetic nerve endings. These hormones bind to beta-1 adrenergic receptors on cardiac muscle cells, leading to increased cyclic AMP (cAMP) production and enhanced calcium influx, thereby increasing contractility.
Step 3: Examine the role of glucagon, a hormone released by the pancreas during low blood glucose levels. Glucagon can also increase cardiac contractility by stimulating cAMP production in cardiac cells, similar to catecholamines, which enhances calcium availability and strengthens heart contractions.
Step 4: Consider the effects of thyroid hormones (mainly T3 and T4), which increase the expression of beta-adrenergic receptors and enhance the responsiveness of the heart to catecholamines. This results in increased heart rate and contractility over time by promoting greater calcium handling and energy metabolism in cardiac cells.
Step 5: Summarize that epinephrine, norepinephrine, and glucagon directly increase cardiac contractility through cAMP-mediated pathways, while thyroid hormones indirectly enhance contractility by upregulating beta-adrenergic receptors and improving cardiac cell function.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Role of Catecholamines (Epinephrine and Norepinephrine) in Cardiac Contractility
Epinephrine and norepinephrine are catecholamines that increase heart contractility by binding to beta-1 adrenergic receptors on cardiac muscle cells. This activates the cAMP pathway, enhancing calcium influx during action potentials, which strengthens myocardial contraction and increases heart rate.
Recommended video:
Guided course
3:49
Cardiac Action Potentials Example 1
Effect of Glucagon on the Heart
Glucagon, primarily known for regulating blood glucose, also increases cardiac contractility by stimulating adenylate cyclase via glucagon receptors. This raises cAMP levels in cardiac cells, similar to catecholamines, promoting stronger and more forceful heart contractions.
Recommended video:
1:32Effects of the Complement System
Influence of Thyroid Hormones on Cardiac Function
Thyroid hormones (T3 and T4) enhance heart contractility by increasing the expression of beta-adrenergic receptors and proteins involved in calcium handling. This leads to heightened sensitivity to catecholamines and improved calcium cycling, resulting in increased cardiac output and contractile strength.
Recommended video:
Guided course
13:06Review of Major Hormones
Related Practice
Textbook Question
What effect does sympathetic stimulation have on the heart? What effect does parasympathetic stimulation have on the heart?
894
views
Textbook Question
The following measurements were made on two individuals (the values recorded remained stable for 1 hour):
Person 1: heart rate, 75 bpm; stroke volume, 60 mL
Person 2: heart rate, 90 bpm; stroke volume, 95 mL
Which person has the greater venous return?
Which person has the longer ventricular filling time?
830
views
Textbook Question
What factors influence cardiac output?
1180
views
Textbook Question
Vern is suffering from cardiac arrhythmias and is brought into the emergency room of a hospital. In the emergency room he begins to exhibit tachycardia and as a result loses consciousness. Explain why Vern lost consciousness.
865
views
1
rank
Textbook Question
Harvey has a heart murmur in his left ventricle that produces a loud 'gurgling' sound at the beginning of systole. Which valve is probably faulty?
940
views