Flashcards in HRV + dyslipidaemia Deck (84)
What are the neurotransmitters of the SNS and PNS?
presynaptic - acetylcholine
postsynaptic - noradrenaline
presynaptic - acetylcholine
postsynaptic - acetylcholine
HR is a balance between ... and ... activity
Additional SNS pathway:
Adrenal pathway with adrenaline released from adrenal medulla
Which parts of the heart does the PNS innervate?
Which parts of the heart does the SNS innervate?
Ventricles (inotropic effect)
Name the 2 receptors involved in the PNS pathway
Presynaptic - nicotinic
Postsynaptic - muscarinic
5 effectors of autonomic nervous system
Some endocrine glands/cells
Some adipose tissue
Post synaptic receptors of SNS include ... and ...-receptors
Pacemaker cells of heart have membrane potentials ... than that of cardiac muscle cells with naturally ... membranes allowing ... depolarisation to threshold producing an AP
SNS ... HR and increases ...
strength of contraction
Pacemaker membrane potential is usually ...
-60mV (versus -80 to -90mV for other cardiac cells)
Describe the process of SNS increasing HR
1. Increased SNS tone
2. Increased adrenaline and NA
3. activation of beta-receptors and increased calcium (and Na+) influx into myocardial cells
4. Depolarisation threshold reached quicker --> increased HR
5. Increased calcium availability --> increased contraction force
The ... of calcium from ... is important for the speed of contraction
The SNS causes a ... forceful contraction with a ... duration
With a slower HR (predominantly PNS), there is a ... depolarisation with ...
With a faster HR (predominantly SNS), there is a ... depolarisation with ... repolarisation
Describe the process of PNS decreasing HR
1. Increased vagal tone
2. Increased ACh release
3. Increased outflow of K+ from cells and decreased calcium influx leading to hyperpolarisation of myocardial cells
4. Depolarisation threshold reached more slowly
5. decreased HR
Beta-1 receptor main location and effects:
Increases HR, increases contractility
Beta-2 receptor main locations and effects:
Bronchiolar and arterial smooth muscle:
Relaxation of bronchial smooth muscle
Differential effect of cardiac SNS fibres: left fibres have a greater effect on ...; right fibres have a greater effect on increasing ...
The intrinsic HR of the heart is ...
As exercise intensity increases, there is more ... control of HR
In a study, participants were given propranolol (Beta-blocker) then atropine and vice versa: what HR response would you see?
Initial HR decrease with propranolol, then increase with atropine to reach intrinsic HR (as both receptors blocked)
Initial increase of HR with atropine, then decrease to intrinsic HR with propranolol as both SNS and PNS receptors blocked
Mean HR is an ... rate over one minute, sometimes the HR will be faster and other times are slower
Demands of the body for HR response:
Delivery of O2 and removal of wastes
HR variability on breathing:
Breathe out: slows down HR (PNS nerves inhibited)
Breathe in: speeds up HR (PNS nerves fire)
During a slower HR with more ... influence, there is ... variation between heart beats
During a quicker HR with more ... influence, there is ... variation between heart beats
Advantages of greater HR variability (3)
So the body can vary HR with all the demands
Variation reflects a healthy vagal system
Lack of variation indicates SNS predominance - hyperpolarised membrane with increased arrhythmia risk