Flashcards in Review posters 06/05/2016 Deck (41):
Which nerve has the parasympathetic supply to the heart?
Which neurotransmitter is released on parasympathetic stimulation and where does it act?
Neurotransmitter is acetyl choline. It acts on M2 muscirinic receptors.
What does stimulation of the parasympathetic supply to the heart cause?
Decreased heart rate and increased AV nodal delay
Name and describe the constant influence the parasympathetic nerves have on the heart?
Vagal tone- constantly over the SA and AV node. Brings intrinsic heart rate down from 100bpm to 70bpm.
Stimulation of the sympathetic supply to the heart.
Causes increased HR and decreased AV nodal delay. Also increases the force of contraction
Where do the sympathetic nerves supply?
Myocardium, AV node and SA node
Where do the parasympathetic nerves supply?
AV and SA node.
Name the neurotransmitter and the receptor to which it binds in the sympathetic supply to the heart
Binds to b1 adrenoceptors.
Name the 5 stages of the cardiac cycle
Isovolumetric ventricular contraction
Isovolumetric ventricular relaxation.
Describe passive filling
Pressure in atria and ventricles close to 0. Atrioventricular valve (mitral or tricuspid) open. Blood flows from SVC and IVC straight into ventricles. They become 80% filled.
Describe atrial contraction
To get the remaining 20% of the blood from the atria to the ventricles, the atria contract. This completes the end diastolic volume.
Describe isovolumetric ventricular contraction.
Ventricles begin to contract. When pressure in the ventricles rises above the pressure in the atria- the AV valves close. The aortic/pulmonary valves are also closed so the ventricles are a closed space.
When the pressure in the ventricles exceeds the pressure in the aorta- the aortic/pulmonary valve opens and the blood leaves the ventricles.
Stroke volume is ejected by each ventricle.
The blood left behind is the end systolic volume.
Isovolumetric ventricular relaxation
The ventricles start to relax so the pressure in the ventricles starts to decrease. The aortic/pulmonary valve shut and the AV valves open when the pressure in the ventricles is less than the pressure in the atria.
a= atrial contraction
c= tricuspid valve bulging into the ventricles when the ventricles contract
v= rise in atrial pressure during atrial filling
Describe the general process of oxidative phosphorylation
Electrons are brought to the electron transport chain on NADH and FADH. Here, the electrons are released and travel down a series of complexes via a series of oxidation and reduction reactions. These reactions provide the energy to pump H+ ions against their concentration gradient across the mitochondrial membrane into the intermembranous space. The final electron acceptor in the chain is oxygen which is reduced to form water.
The H+ ions then flow back down the concentration gradient through ATP synthase, phosphorylating ADP to ATP.
How does NADH and FADH get into the mitochondrial matrix from the cytoplasm?
Aspartate malate co-transporter.
Oxaloacetate and NADH combine to form Malate. Malate is then transported into the mitochondrial matrix where it breaks back down into oxaloacetate and NADH.
Why do we need NADH and FADH in the mitochondrial matrix?
NADH cannot cross the lining
Also NAD+ can't be used in oxidative phosphorylation.
How are NADH and FADH linked to ATP?
Electron transfer from NADH and FADH ultimately is converted to the phosphoryl transfer of ATP
What is a redox potential?
Reduced substance (X)- tendency to release electrons in comparison with hydrogen (h2)
Describe trends in redox potentials and how they are related to E0
As the E0 becomes more negative- it is more likely to be oxidised- therefore acting as a reducing agent.
As the E0 becomes more positive- it is more likely to be reduced- therefore acting as a oxidising agent.
What are the two steps to oxidative phosphorylation and what do they consist of?
Electron transfer- electrons from NADH and FADH ultimately transferred to O2.
Energy used to pump H+
ATP synthesis- electrochemical gradient of H+
Flow through ATP synthase energy used to phosphorylate ADP
What are cytochromes?
Proteins with haem groups. Haem groups contain iron which can reversibly bind to electrons.
Which complex does NADH release its electrons too?
Which complex does FADH release its electrons too?
Which complexes are cytochromes?
3 and 4
Which complex does not pump H+ across the membrane?
How does ATP synthase convert the flow of H+ to phosphorylating energy?
Flow of protons turns the rotor (made up of gamma, e and c subunits). This produces energy
Allows 'short circuiting' of the mitochondrial respiration.
Where is uncoupling protein found?
Brown adipose tissue. Used in hibernating animals and newborns.
Neural control of respiration
Pre-botzinger complex (in the medulla) stimulates rhythm. This causes the dorsal respiratory group of neurones to fire action potentials to the muscles of inspiration.
What happens if the dorsal respiratory group fire too often (hyperventilation)?
This stimulates a second respiratory group of neurones called the ventral respiratory group- they fire action potentials which stimulate accessory muscles and cause a forced expiration.
What role does the PONS play in respiration?
PONS alters signals. Pneumotaxic centre will be stimulated to stop long periods of inspiration with short expiratory gasps (apneusis). The apneustic centre does the opposite.
How are the respiratory sensors influenced?
Stretch receptors (Hering Bruer reflex)
Joint receptors (movement of joints increases breathing)
Juxtapulmonary receptors (stimulated by pulmonary cappilary congestion or oedema)
Higher brain influence
How does exercise influence respiration?
Increased joint movement- increases breathing
Accumulation of carbon dioxide
Increased body temp
Followed by closure of the trachea
Contraction of abdominal muscles
Opening of the trachea
What is the hypoxic drive?
Driven by peripheral chemoreceptors. When O2 saturations in the blood get below 8kpa. Important in patients with COPD
Hypercapnia and ventilation
Fast response- as carbon dioxide levels rise, ventilation increases massively
Hypoxia and ventilation
O2 levels become very low before the peripheral chemoreceptors catch on- not as reactive to oxygen as it is to carbon dioxide.
Acute effects of altitude training
Decreased partial pressure of oxygen means that hyperventilation and increased cardiac output occur.