Lecture 2 Flashcards
What is the relationship between the heart and the brain known as?
Neuro-cardiac axis
What are the typical Stroke volume values at rest?
60-65
What are the 3 types of neural control?
Higher brain centre control, sympathetic and parasympathetic nervous system control
What is the cardiovascular control centre?
Medulla oblongata
What is found in the sympathetic centre?
Distinct accelerator and augmentor
What is found in the parasympathetic centre?
Nucleus vagus and nucleus ambigous
What does the augmentor do?
Changes the contractility of the heart
What does the nucleus ambiguous do?
Collection of cells in the brain stem
What does the sympathetic nervous system release?
NA - noradrenaline
What does the sympathetic nervous system increase?
Heart rate and contractility
Describe the structure of the sympathetic nervous system
Short pre ganglion fibres and long autonomic ganglions
Where is the autonomic ganglion located in the sympathetic nervous system?
C6-C7, at the bottom for your neck
What is the stellate ganglion?
A collection of sympathetic nerves - it has a star apperance
What is released at the heart and the ganglion in sympathetic nervous system?
ACH at the ganglion and NA at the heart
What do Sympathetic nerves act on in the heart?
Beta 1 receptors
What is lusitopy?
The rate of relaxation, want the heart to fill, if the heart can relax properly then it cannot fill up with blood
Where do fibres coming from the right side of the heart go to?
The nodal
Where do fibres coming out of the left side of the heart go to?
Ventricular tissue
What is dromotropy?
The electrical conduction through the heart through the atrial ventricular node
What does a positive dromotropic effect do?
Speeds up the conduction of the electrical activity through the heart
Where are autonomic ganglion found in the parasympathetic nervous system?
On the heart
Describe the structure of the parasympathetic nervous system
Long pre ganglionic and short autonomic ganglionic
What neurotransmitters are released in parasympathetic?
Just ACH
What does the parasympathetic nervous system control?
SA node and AV node
What decreases in the parasympathetic nervous system?
Heart rate and it has little effect on the contractility
What receptors does the parasympathetic nervous system act on?
Muscarinic
What is found on the outside of the heart?
Epicardial fat
What branches off the epicardial fat surrounding the heart?
Vagus nerve
Where are the ganglia found?
Surrounding the SA node and the AV node
What happens when you add a beta blocker to the sympathetic nervous system?
A decrease in heart beat as you take away the accelerated function
What is an Example for a beta blocker?
Propranolol
What does atropine do?
Bocks the muscarinic receptors and increase in the heart rate
What is the predominant nervous system during fight or flight?
Sympathetic nervous system
What happens if you inhibit the parasympathetic nervous system?
It will lead to a rise in heart rate
What happens if you inhibit sympathetic nervous system?
Will decrease heart rate
Where is the Majority of the areas of the brain that play important roles in nervous regulation?
The vasomotor centre - lower third of the pons
What does the vasomotor centre transmit?
Sympathies impulses through the spinal chord and peripheral sympathetic nerves to all arteries, arterioles and veins of the body
Where do the sympathetic vasomotor nerve fibres leave the spinal cord through?
The thoracic spinal nerves and 1st one or two lumbar spinal nerves
What vessels are not innervated?
Capillaries, precapillary sphincters and metarterioles
What does innervation of the small arteries and arterioles allow?
Sympathetic stimulation to increase resistance to blood flow and decrease rate of blood flow through the tissue
What is synthetic innervation?
When there is a release of NA it will cause constriction of the vessels and cause increase resistance and decrease the flow (synthetic vascoconstriction)
What innervation to you have in a muscular artery?
Noradrenergic innervation
Where is NA released in a muscular artery?
Lumps/nodules
What happens when anaesthesia is added to the spinal cord?
Neural transmission stops and pressure drops
What happens when NA is added back into the neural flow?
Blood pressure increases - representing there is a neuronal control of blood flow
What neurotransmitters are released in signal transduction at sympathetic varicosity?
NA, ATP and neuropeptide-Y
What does neuropeptide-Y act on?
Acts on NPY-1 receptors
What determines flow in a vessel?
Pressure and resistance
What does resistance to flow depend on?
The radius of the vessel to the power of 4
What do small changes in the radius of the vessel alter?
The flow which alters the pressure
What is the main target for sympathies NS effect on vasaculture?
Small arteries and large arterioles (decreases blood flow by vasoconstriction)
Describe the venous system
Where the majority of the blood is in your veins at one time
What has component has poor innervation?
Muscle veins
What happens if central BP drops?
Venoconstriction diverts blood to systemic circulation - blood can be shifted to where it is needed
What is sympathetic vasodilation mediated by?
Circulating adrenaline or a cholinergic sensitive NA release
What specific tissues does parasympathetic vasodilation target?
No important in cardiovascular but in salivary glands, pancreas, GI tract and genital erectile tissue
What are the 4 main endocrine systems that regulate blood pressure?
Adrenaline, Antidiuretic hormone, renin-angiotensin system and natriuretic peptides
Where does adrenaline come from?
Comes from the adrenal medulla on top of the kidneys
What are the transmitters for adrenaline?
Alpha 1, beta 1 and 2
What does alpha 1 do?
Constricts blood vessels
What does adrenaline coming from the adrenal medulla do?
Increases cardiac output
When is ADH released?
When sensors in the brain detect changes in osmolarity
What are osmoreceptors?
They are collections of cells located in the hypothalamus that lead to a production in ADH
What are some examples of osmoreceptors?
Supraoptic nuclei and paraventricular nuclei
Where are the osmoreceptors secreted to?
Down to the posterior element of the pituitary gland
When is ADH released?
When blood plasma increases above the set point of 280mOsm
In non Osmolar when is ADH triggered?
Below 10%
When is Renin-angiotensin stimulated?
When there is a drop in blood pressure
What does renin act on?
Angiotensin
What does angiotensin cleave?
Angiotensin 1
What enzyme does angiotensin 1 act on?
ACE (angiotensin converting enzyme)
What is formed when ACE acts on angiotensin 1?
An ocotpeptide called angiotensin 2
Where is ACE released from?
Endothelial cells
What is angiotensin 2?
A potent vasoconstrictor
What is a common first line treatment for people will high blood pressure? (Hypertension)
ACE inhibitors
What is a way of reducing vasoconstriction?
Preventing the conversion of angiotensin 1 to 2
What are the 2 types of natriuretic peptides?
ANP (Atrial) and BNP (brain)
What do natriuretic peptides do?
Get rid of sodium and water
What do Natriuretic peptides decrease?
Blood volume which decreases blood pressure
