Podcast
Questions and Answers
Which of the following best describes the function of transmitting (conducting) cells in the heart?
Which of the following best describes the function of transmitting (conducting) cells in the heart?
What is a key difference between a myogenic cardiac muscle and a neurogenic skeletal muscle?
What is a key difference between a myogenic cardiac muscle and a neurogenic skeletal muscle?
What best describes the 'funny' channel in pacemaker cells, and its primary consequence?
What best describes the 'funny' channel in pacemaker cells, and its primary consequence?
During the cardiac action potential, what role do voltage-gated calcium channels play?
During the cardiac action potential, what role do voltage-gated calcium channels play?
Signup and view all the answers
What is the effect of stimulating a cardiac muscle cell during its plateau phase of the action potential?
What is the effect of stimulating a cardiac muscle cell during its plateau phase of the action potential?
Signup and view all the answers
Which structures facilitate the rapid transmission of depolarization between cardiac muscle cells?
Which structures facilitate the rapid transmission of depolarization between cardiac muscle cells?
Signup and view all the answers
What is the significance of all cardiac muscle cells exhibiting membrane potential changes cyclically?
What is the significance of all cardiac muscle cells exhibiting membrane potential changes cyclically?
Signup and view all the answers
Which of the following is a consequence of gap junctions in cardiac muscle?
Which of the following is a consequence of gap junctions in cardiac muscle?
Signup and view all the answers
Which type of circulatory pump is characterized by specialized muscular chambers and valves that ensure one-way flow?
Which type of circulatory pump is characterized by specialized muscular chambers and valves that ensure one-way flow?
Signup and view all the answers
What is the primary function of the ligaments in a crab's heart?
What is the primary function of the ligaments in a crab's heart?
Signup and view all the answers
What is the correct definition of a neurogenic heart?
What is the correct definition of a neurogenic heart?
Signup and view all the answers
During which phase of the crab heart cycle does hemolymph enter the heart through the ostia?
During which phase of the crab heart cycle does hemolymph enter the heart through the ostia?
Signup and view all the answers
What is the role of pacemaker cells in vertebrate cardiac tissue?
What is the role of pacemaker cells in vertebrate cardiac tissue?
Signup and view all the answers
What happens to the ostia valves during the contraction phase of the crab heart?
What happens to the ostia valves during the contraction phase of the crab heart?
Signup and view all the answers
Which of the following is NOT a characteristic of ‘contractile elements not strictly part of the circulatory system’?
Which of the following is NOT a characteristic of ‘contractile elements not strictly part of the circulatory system’?
Signup and view all the answers
What is the role of the pericardial sinus in a crab's circulatory system?
What is the role of the pericardial sinus in a crab's circulatory system?
Signup and view all the answers
Study Notes
Lecture 10: Cardiac Muscle
- Topic: Hearts/Cardiac Muscle
- Readings: 561, 339-339, 329-330, 672-675, 694-697, Box 25.1
- Date: January 27th
Types of Circulatory Pumps
-
Specialized Muscular Chambers:
- Contain valves that ensure one-way blood flow.
- Found in most adult hearts.
-
Contractile Elements:
- Not part of the circulatory system.
- Aid in venous return to the heart.
- Examples include peristaltic contractions in some invertebrates and embryonic vertebrates.
Invertebrate Hearts
- Example (e.g.): Many arthropods
-
Neurogenic:
- Definition needed (see page 3).
- Posterior cardiac ganglion nerves stimulate spontaneous rhythmic depolarization.
- Anterior axons innervate the cardiac muscle.
Crab Heart
- Suspension: Suspended in a pericardial sinus by ligaments.
- Hemolymph Pooling: Incoming hemolymph from gills collects in the sinus.
- Hemolymph Entry: Hemolymph enters the heart through ostia.
- Diastole/Systole: "Sucked in" during relaxation (diastole) and contraction (systole), respectively.
- Ostia Valves: Heart contraction closes one-way ostia valves, which regulate blood flow.
- Blood Force: Blood is forced out through arteries.
- Ligament Elasticity: Ligaments stretch and store energy during heart contraction, essential for efficient blood expulsion. Then recoil, expanding the heart, and opening the ostia for inflow.
Vertebrate Cardiac Muscle
- Key Structures: Intercalated discs, gap junctions, and desmosomes are key structural elements that electrically couple cardiac cells.
- Importance: These structures enable efficient propagation of depolarization and synchronized contraction of cardiac muscle cells.
- Mitochondria: Mitochondria are an important component within cardiac muscle cells; responsible for energy production (ATP).
Vertebrate Cardiac Cell Types
-
Pacemaker Cells:
- Non-contractile cells that generate spontaneous action potentials (membrane potential changes).
- Found in sinus venosus (fish) and SA node (mammals).
-
Contractile Cells:
- Located in atria and ventricles.
-
Conducting Cells (Transmitting Cells):
- Non-contractile cells that transmit action potentials.
- Examples are the bundle of His, AV node, and Purkinje fibers.
Vertebrate Cardiac Muscle Contraction
- Myogenic: This type of heart contraction is self-excitable, meaning the heart generates contraction based on its own properties (no external nerves needed).
- Myogenic Mechanisms: Include a specific cell type called pacemakers that regulate rhythmicity of cardiac contraction (electrical signals).
Cardiac Action Potential
- Threshold: Factors or series of events that precede an action potential and push the membrane potential above the threshold.
- Depolarization/Repolarisation: Series of membrane potential fluctuations during contraction and relaxation (action potential steps).
- Plateau: An extended depolarization period that occurs during action potential (important time for contraction).
- Voltage-Gated Channels: Important ion-conducting channels for initiating and maintaining the plateau and subsequent repolarization.
Myogenic Mechanism
- Membrane Potential Changes: Cells experience cyclic changes in membrane potential (especially important in pacemaker cells).
- Funny Channels: These nonselective channels for ions play a key role in pacemaker potential (e.g. cell activity).
- Influx/Efflux: Na+ influx is more prominent than K+ efflux in the pacemaker cells, which contributes to the membrane potential fluctuation.
Cardiac Muscle Tetanus
- Plateau Phase Stimulation: Contraction and relaxation will not occur if stimulated at plateau phase (action potential); only during some of the phase.
Cardiac Muscle Cells: Electrical Conduction
- Gap Junctions: these junctions serve as low resistance pathways for the rapid movement of ions, facilitating the synchronized depolarization and contraction of cardiac muscle cells.
- Intercalated Discs: Gap junctions are concentrated in intercalated discs, which are specialized structures located between cardiac muscle cells.
- Depolarization Transmission: Rapid spread of electrical signal from one cardiac muscle to another.
Different Cells, Different Potentials
- Action Potentials: Each cell type exhibits characteristics features of the pacing and conduction.
- Timeframes: Timeframes during which the action potential and associated events occur in each cell.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the intricacies of cardiac muscle in hearts through key readings and concepts. This quiz delves into circulatory pumps, specialized muscular chambers, and the unique heart structures in invertebrates like crabs and arthropods. Test your knowledge on the mechanisms that regulate heart function across different species.
