811869
Description
Flashcards by Hannah Tribe, updated more than 1 year ago
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Created by Hannah Tribe
over 10 years ago
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| Question | Answer |
| Why does the circulation need to be controlled? | To regulate TPR and therefore BP |
| Is it intrinsically or extrinsically controlled? | Extrinsically |
| TPR and BP can be controlled by release of _____________ and ___________. | Neurotransmitters, hormones |
| How is the release of neurotransmitters mediated? | Baroreceptors and chemoreceptors in vessels send signals to the hypothalamus, which signals the RVLM to send excitatory signals to the thoracic spinal cord to stimulate the sympathetic fibres to the heart, vessels and adrenal medulla. |
| In blood vessels, sympathetic _____________ fibres exist in the T. ___________. On these fibres are ______ ___ ___________, and it is from here that ___ is released. | vasoconstrictor, adventitia, strings of varicosities, NA |
| How does this achieve vascular tone? | Low frequencies of NA are constantly being released, meaning the vessel is always in a slightly constricted state. This way it can be constricted more or relaxed according to need. |
| Where does the NA bind to? | Alpha 1 adrenergic receptors on vascular smooth muscle. |
| Give 2 reasons why this is helpful to meet the body's needs. | 1. Ensures that the brain and myocardium are always well perfused 2. Can direct blood flow to certain areas of the body and away from others. |
| How might this be useful in maintaining blood volume, for example? | If pre-capillaries are constricted, the capillary pressure will decrease and favour fluid reabsorption from the interstitial fluid, thus increasing blood volume. |
| Which other nerves can affect blood vessels but are less common? | Vasodilator nerves |
| What are the 3 types of vasodilator nerves? | 1. Parasympathetic 2. Sympathetic 3. Sensory (nociceptor C fibres) |
| Where are parasympathetic vasodilator fibres found, and which neurotransmitters activate them? (3) | 1. Salivary glands - ACh on M receptors, VIP on NANC receptors 2. Pancreas/intestinal mucosa - VIP on NANC receptors 3. Erectile tissue - NO and VIP on NANC receptors |
| Where are sympathetic vasodilator fibres found, and which gland are they associated with? (1) | Skin - sweat glands |
| When sensory vasodilator fibres are activated, what is this in response to and what happens at the area? | Trauma - redness and swelling |
| What is their mechanism of action? | Activates the C-fibre axon reflex. Causes release of substance P and dengranulation of mast cells to release histamine, which causes vasodilation and increases vessel permeability. |
| Name 4 hormones which help control circulation | 1. Adrenaline 2. Angiotensin II 3. Atrial Natriuretic Peptide 4. Vasopressin (ADH) |
| When and from where is adrenaline released? | Released from the adrenal medulla in response to: 1. exercise 2. Fear, fight or flight 3. hypotension 4. hypoglycaemia |
| Which receptors does adrenaline have higher affinity for? | beta adrenergic |
| Where are there beta 2 receptors that allow dilatation? (3) | Skeletal muscle, myocardium and liver |
| Which receptors cause vessel constriction? | Alpha 1 adrenergic |
| What is the effect of adrenaline? (4) | 1. Increased HR 2. Increased CO 3. Slight increased BP 4. Decreased TPR |
| What causes secretion of Renin from the kidneys? (2) | 1. Sympathetic stimulation 2. Low renal blood flow |
| What does Renin do? | converts angiotensinogen to Ang I, which gets converted by ACE to Ang II in lungs. |
| What does Ang II do? (3) | 1. Increases sympathetic drive 2. Causes thirst 3. Stimulates production of aldosterone from adrenal cortex |
| What does aldosterone do? | Retains Na+ and water, so blood volume increases, causing CVP to increase and thus increasing SV (Starling's Law), CO and BP. |
| Where is vasopressin (ADH) secreted from? | Posterior pituitary gland |
| What stimulates the secretion of ADH? (2) | 1. Switching on of CVLM in response to low blood pressure and volume signals hypothalamus 2. Osmoreceptors detect low blood volume and signal hypothalamus |
| What effect does ADH have? (2) | Increases water reabsorption so increases blood volume and thus BP. Also raises BP by causing vasoconstriction. |
| Where is ANP released from? | Atrial myocytes |
| What stimulates its release? (2) | 1. High BP 2. High blood volume |
| What receptor does ANP bind to? | Natriuretic Peptide Receptors |
| What effect does ANP have? | 1. Increases Na+ and water excretion 2. Vasorelaxation (by cGMP) 3. Increases permeability |
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