block B- systems physiology Flashcards
what is the autonomic nervous system?
its really important to regulate body function and agonists mediate functional responses via receptors (mostly GCPRs)
what direction do afferent neurons go?
from the peripheral nervous system towards the central nervous system
what dircetion do efferent neurons go?
towards the peripheral nervous system
what are the three types of peripheral nerves?
sensory, autonomic and somatic
what is the function of the sympathetic division?
its the emergency system in charge of fight or flight
what is the function of the parasympathetic division under non-stressful conditions?
it effects predominately during the times of ‘rest and repair’
what does the parasynthetic system do to the body?
it slows the heartbeat, promotes digestion and gland secretion
what are the receptors in the ANS?
they’re mostly G-protein coupled receptors which mediate the action of released transmitters
what are the 2 subgroups of ANS receptors?
acetylcholine and noradrenaline
what are the two types of acetylcholine receptors?
nicotinic and muscarinic
what do second messengers link in the ANS?
they link the functional outcomes important in the ANS-beta-1 receptors in the heart
what do beta-2 receptors do the airways via cAMP?
they cause relaxation
what do alpha-1 receptors in vascular smooth muscle do?
they cause contraction
- this could also be muscarinic M3 receptors in guinea pig ileum because receptors share signalling mechanisms
- these muscarinic receptors are found in the airways smooth muscle
what do different second messenger systems link receptors to different functional outcomes due to activation of receptors by?
agonists
what mediate the function of both the sympathetic and parasympathetic parts of the ANS?
receptors
what receptors are heterogenic and what are the two types of each?
alpha-Adrenoceptors
alpha-1 (postsynaptic at sympathetic neuroeffector synapses)
alpha-2 (presynaptic at sympathetic neuroeffector synapses)
beta-Adrenoceptors
beta-1 (heart, intestinal smooth muscle)
beta-2 (bronchial, vascular and uterine smooth muscle)
Acetylcholine receptors
nicotinic (in sympathetic and parasympathetic ganglia)
muscarinic (parasympathetic neuroeffector synapses)
what are sympathomimetrics?
theyre driugs that mimic the actions of noradrenaline and adrenaline
what do the 4 types of sympathomimetics do?
beta-2-agonists cause bronchial dilation and are used in the treatment of asthma
beta-1-agonists are sometimes used to stimulate the force of the heart contraction
alpha-1-agonists are used to treat blocked nose/ sinuses
alpha-2-agonists are centrally acting hypotensive drugs
what are the two types of selective adrenoceptor antagonists?
alpha-adrenoceptor antagonists - blockers for these receptors reduce arteriolar and venous tone
beta-adrenoceptor antagonists - blockers for these receptors reduce heart rate and force contraction of the heart with less effect on blood vessels and bronchioles
what are some of the uses of muscarenic receptor antagonists?
anti-pasmodics
mydratics
bronchodilators
bladder relaxants
antiemetic
why study the heart in pharmacology?
it keeps you alive and cardiovascular disease is one of the biggest health issues in the UK
what are the main functions of the cardiovascular system?
rapid transport of nutrients
removal of waste products of metabolism
hormonal control by transporting hromones to their target organs and by secreting its own hormones
temperature regulation by controlling heat distribution between the body core and the skin
host defense, transporting immune cells, antigens and other mediators
what are the walls of the heart called and what are they made up of?
they’re called the myocardium and are made of cardiac muscle
what is the endocardium?
inner surface of walls that is in contact with the blood
what is the epicardium?
its the inner lining of the pericardium which is continuous with the covering of the heart itself
what is the pericardium?
its where the heart is located within a fluid membranous sac
what are the two phases of the cardiac cycle?
the contractile phase (systole) and the relaxation, filling stage (diastole)
what changes occur in the heart during and following a single heart beat?
electrical and mechanical changes
what does the alternation between contranctiona nd relaxation produce?
it produces differences in pressure which push the blood into the heart chambers and the circulation
what are cardiac muscle cells joined together by?
gap junctions
what do gap junctions allow?
they allow for the spread of exitations from one cell to another and allow the cardiac muscle to act as a whole
what do the specialised cells in the myocarium make up? and what are they essential for?
they make up the conducting system and are essential for heart excitation
what blood vessels supply the myocardium with blood?
coronary arteries
what are the events leading up to cradiac contranction?
depolarisation of the plasma membrane
opening of voltage-sensitive Ca2+ ion channels
Ca2+ ions flow into the cell and Ca2+ release from sarcoplasmic reticulum
rise in cystolic Ca2+ concentration
CONTRACTION
what is the role of the sino-atrial node?
it acts as a pacemaker
how do the atrioventricular node, ventricular conducting fibres and ventircular myocardium spread electrical activity?
atrioventricular node- a tactical pause
ventricular myocardium - surface roads
ventricular conducting fibres - freeways
what is cardiac potential?
its an action potential - this is a transient depolarisation of the cell membrane and are initiated when the membrane is depolarised, they happen spontaneously and transmission is from adjacent myocytes through gap junctions
what are the two types of depolarising cells?
fast and slow
what are the two types of refractory periods?
absolute refractory period (ARP) ~250ms in myocytes
relative refractory period (RRP)
what is chronotropic control?
its changes in heart rate
how much does temperature affect pacemaker?
its estimated that heart rate increases by 10bpm for every degree C increase in temperature - this is why heart rate increases when a person has a fever
what system increases heart rate?
sympathetic fibres - noradrenaline -beta1 receptors increase the permeability of the nodal cell plasma membrane to Na+ and Ca2+
what system reduces heart rate?
parasympathetic- acetylcholine - M2 receptors increase permeability to K+ and decrease Na and Ca2+ permeability
how do you calculate cardiac output?
stroke volume x heart rate
what is stroke volume?
its the volume of blood pumped per contraction
what is end-diastolic volume (EDV)?
volume of blood in ventricle before contraction
how much of EDV (end-diastolic-volume) is usually pumped per contraction?
normally about 60% of the EDV is ejected on each contraction