Chapter 7- The Heart Flashcards
Similarities and differences of skeletal muscles and cardiac muscle
Sim:
Arrangements of proteins
Diff
Cardiac cells are much shorter and wider than skeletal muscles
One nucleus per cell
Explain adaptions of cardiac muscle cells
Cells are Y shaped and are joined end to end in a complex of interconnected cells
Where on cell is connected with another there is a specialised junction called an intercalated disc
Adaptions of intercalated disc
Consists of double membrane containing gap junctions which provide channels of connected cytoplasm between the cells - allows for rapid movement of ions and low electrical resistance
What are do the 2 previous adaptions of cardiac muscle allow for?
Wave of depolarisation to pass easily from one cell to a network of other cells leading to synchronisation of muscle contraction:”
Signals from the sinoatrial node that cause contractions cannot what?
Pass directly from atria to ventricle
What is the contraction of the heart chambers called ? What is relaxation of them called?
Systole
Diastole
Explain the journey of the signals from the sinoatrial node up to sty stole
Cause contractions within the atria can not pass directly from the atria to the ventricles, instead reaches atrioventricular node- from there spreads throughout heart muscle via specialised tissue called punkinje fibres- causes ventricles to undergo systole
Explain the journey of the signals from the sinoatrial node up to diastyole
Snaps atrioventricular valves shut
Ventricles are emptied, semilunar valves close
Ventricles begin diastole- atrioventricular valves open and ventricles fill with blood - finally all 4 chambers are opened - when 70% filled cycle has ended
What is there a delay btween
The arrival and passing on of a stimulus at the atrioventricular node
What are the features of the AV nodes that lead to a delayed initiation of contractions of the ventricles?
1) AV node cells have smaller diameter and do not conduct as quickly
2) reduced number of NA channels in membranes
3) fewer gap junctions
4) relatively more non- conductive connective tissue in the node
What does the delay time allow for?
Allow time for the atrial systole before the atrioventricular valves close-
Ensures atria contract and empty blood they contain into the ventricles before ventricles contract
What do conducting fibres do?
Atrioventricular bundle receives the impluse from the AV node and conducts the signal rapidly to a point where it splits into the right and left bundle branches - bundle branches connect the purkinje fibres which conduct the singal even more rapidly to the ventricles
What are the adaptions of fibres in the ventricles to make them move at high speed?
1) have few myofibrils
2) have bigger diameter
3) higher densities of voltage gates sodium channels
4) High numbers of mitochondria and high glycogen stores
What is the causes of sound of heartbeat?
By the atrioventricular valves and semilunar valves cashing changes in blood flow
Closing and opening of valves
Use of artificial pacemakers to regulate the heart
Fitted to patients with a malfunctioning sinoatrial node - purpose of device is To maintain. The rhythmic nature of the heartbeat when the heart doesn’t beat fast enough
Can either provide a regular heartbeat or discharge only when a heartbeat is missed
Use of defibrillation to treat life- threatening cardiac conditions
Cardiac arrest occurs when the blood supply to the heart becomes reduced and the heart tissues are deprived of oxygen- first negative consequences is ventricular fibrillation - the twitching of the ventricles due to rapid and chaotic contractions of muscle cells
When reach a scene and victims is not breathing- apply two paddles of a defibrillator to the chest of the patient- detects if fibrillation is happen and if it is an electrical discharge is given to restore normal heart beat
How are the heart muscles in appearance?
Striated
What is atherosclerosis?
Hardening of the arteries caused by formation of plaques on the inner lining of the arteries - plaques are areas that are swollen and accumulate a diversity of debris
What can the plaques trigger?
A clot or thrombosis which can lock blood flow through the artery and deny the tissue access to oxygen - consequences can be heart attack
What is hypertension
Greater resistance to the flow of blood can slow the flow of blood- result is higher pressure on walls of arteries
Consequences of hyper tension
1) damage to the cells that line the arteries - narrower and stiff
2) constant high blood pressure can weaken artery causing section of the wal to enlarge and form bulge- aneursym- can burst and cause internal bleeding
3) chronic high blood pressure- lead to stroke
4) chronic high blood pressure can lead to kidney failure
Number of factors that are correlated with a greater incidence of thrombosis or hypertension
1) having parents who have experienced heart attacks indicates a genetic precondition to either condition
2) old age leads to less flexible blood vessels
3) risk in females increases lost menopause correlated with fall in estrogen levels
4) males are at greater risk compared to females with Lowe levels of estrogen
5) smoking raises blood pressure
