Week 6 The cardiovascular system (control of contraction) Flashcards
Vertebrate hearts are neurogenic/myogenic?
Myogenic
Define Myogenic.
ability to generate spontaneous rhymical depolarisations
the rate of depolarisation varies
What are pacemaker cells?
specialized cardiac muscle cells which are more excitable than the others and therefore contract first (Cardiac muscle contracts without neural stimulation)
- fast intrinsic rhythm of firing - determunes contraction rate
- Fish - sinus venosus
- Other vertebrates - sinoatrial node (SAN)
What type of cell is this?
rod shapped cardiac myocyte.
How does cardic muscle vary from skeletal muscles or others?
How they are joined together through intercalated discs containing desosomes enables cells to be myogenic and communicate very well with eachother (unobstructedly - no walls that take time to pass) - fluid like movement, depolisation moves uninterrupedly.
Cardiac muscle: What is the role of desosomes and gap junctions?
- desosomes: transfer the force from cell to cell
- gap junctions: allow passage of electrical signals
Cardiac muscle: how are intercalated discs formed?
- formed from plasma membrane of 3 adjacent cells which are intertwined and bounded together by gap junctions and desosomes
- cells binding together mechanically, chemically and electrically results in their acting together
How does sacromeres of cardiac muscle differ from skeletal muscle?
- have the same banding patters
- but cardiac sarcomeres have branching fibrillar networks which are continuous in three dimesion throughout the cytoplasm
How does the sacroplasmic reticulum and the T system function?
- The plasma membrane invaginates traversely forming tubular system (T tubules) between cisternae.
- contain voltage-sensor proteins which activate when membranes depolarize
- induced sarcoplasmic reticulum to release Ca2+
- T tubules and adjacent cisternae form a diad
Uses of Energy (ATP) in the heart:
- enormous energy demand is related primarily to ATP-dependent processes driving Excitation Contraction coupling (movement of ions)
- about 70–75% of total intracellular ATP is used for force generation powering work output
- remaining 25–30% is used for basal metabolism
What is the key regulator of EC in the heart?
Sodium-Potassium Pump, maintains sodium levels with a careful change.’
permiability of sodium increase/decreases the action potencial in heart , meaning the distribution of these ions across the cardic cell membrane to maintain an electrochemical gradient.
What does Cardiac Na/K ATPase play a role in?
Na/K ATPase controls the Na/K pump.
- trans-membrane transport
- ion homeostasis
- electrical excitability
- control of cell volume and contractility
What are the properties of the pacemaker cells?
- small, few myofibrils, mitochondira & other organelles
- do NOT contract
- unstable resting membrane potencial (RMP) –> pacemaker potencial
What is the hierarchy of pacemakers?
different action potencials for the pacemakers