Heart Rate

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  • Created by: Hindleyc
  • Created on: 09-04-19 12:22
What is cardiac muscle? what does this mean?
Myogenic, means it can contract on its own without needing nerve impulses
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What is atrial systole
Atria contract which pumps blood into ventricles
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What is ventricular systole
ventricles contract
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What is diastole
Atria and ventricles relax, atria fill with blood
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What does the SAN do
Fires action potential, pacemaker, sends impulse
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Where are contractions initiated
within the heart by the SAN (pacemaker) in the right atrium, tissue acts as a clock and contracts spontaneously and rhythmically about once a second even when surgically removed from the heart
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What does cardiac cycle have
3 stages
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Atrial systole,
SAN transmits electrical impulse throughout the atria which both contract pumping blood into V
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What are the V
electrically insulated from the atria so they don't contract at this time, blood can't flow back into the veins because of the valves in the veins
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What is ventricular systole
Electircally impulse passes to the V via the atrioventricular node AVN, the bundle of his and the purkinje fibres
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What are these
Specialised fibres that don't contract but pass the electrical impulse to the base of the ventricles with a short but important delay of about 0.1s
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What does the delay allow
A to empty
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What do the ventricles therefore do
Contract shortly after the atria from the bottom up- efficient squeeze, squeezing blood upwards unto the arteries
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Why can't the blood go into the atria
because of the atrioventricular valves which are forced shut with a Lub sound
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What is diastole
Atria and ventricles relax while the atria fill with blood
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What valves shut
Semi lunar valves in the arteries as the arsenal blood pushed against them, making a dub sound
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What is the autonomic nervous system
organisation of human nervous system
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What does human nervous system do
Splits into CNS which is brain and spinal cord interneurone and Peripheral nervous system which is everything else sensory and motor neurones
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What does the peripheral nervous system split into
Somatic nervous system which is voluntary with input from sense organs and output to skeletal muscles (smile and speak) and the Autonomic nervous system which is involuntary with input from internal receptors and output to smooth muscle and glands
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EG
Pancreas- blood glucose control insulin and glucagon , temp control HR, water balance
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What does autonomic nervous system split into
Sympathetic motor system which is the prepare for action flight or flight response, has NT noradrenaline known as adrenergic systems
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What is it
Nervous, similar effect to hormone adrenaline speeds up HR BR and glucose
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What is its antagonistic- opposite where 1 does 1 thing and 1 does opposite to work against
The parasympathetic motor system
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what type of response
Relaxing with NT acetyl choline so known as 'Cholinergic system that brings boy back down so HR and BR decrease and glucose goes to glycogen
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How is the heart rate controlled
By the medulla important in the autonomic nervous system- sympathetic and parasympathetic
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What does it control
All non-skeletal muscle eg cardiac (heart) and smooth (lines tubes in digestive system, bronchi, arteries
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What does it control
Activities such as breathing, heart rate, sweating
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If co2 is detected what is sent
Impulse sent to SAN
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What is nervous impulse faster than
hormone
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What does it need
PNS and SNS
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What does PSN do
Slow down HR
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What does SNS do
Speed up HR
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What does it sometimes act by
Constricting some muscles and relaxing others
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Resting HR is 70bpm but what is essential
That this rate can be altered to meet varying demands for oxygen
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What are changes to the HR controlled by
Region of brain called medulla oblongata that has 2 centres
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What are the 2 centres
Centre that inc HR which is linked to the SAN by the sympathetic nervous system and centre that decreases HR which is linked to the SAN by the parasympathetic nervous system
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Which centre is stimulated depends on what
the information they receive from receptors which respond to a number of changes
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What are the changes
Chemical changes in the blood, pressure changes in the blood
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What are used
chemoreceptors
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What happens when muscles are more active
they respire more quickly and cause several changes to the blood such as Dec oxygen, inc co2 conc, decrease PH since co2 dissolved to form canonic acid
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What are all the changes detected by
The various receptor cells around the body but the ph changes are the most sensitive and therefore most important
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Where are the main chemoreceptors found in (receptor cells that can detect chemical changes
- walls of the aorta (aortic body) monitoring the blood as it leaves the heart, Walls of the carotid arteries (carotid bodies) monitoring the blood to the head and brain and the medulla monitoring TF in the brain
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What do the chemoreceptors do
Send the nerve impulses to the cardiovascular centre indicating that more respiration is taking place
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What does the cardiovascular centre in the medulla oblongata respond by
Increasing the frequency of nerve impulses to SAN which in turn increases Heart rate
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How is heart rate initiated
SAN fires impulse (AP) which spreads over both atria so they contract at the same time, Band of non-conducting tissue across atria stop impulse but AVN is conducting so detetects impulse and conducted down septum by bundle of his (fibres in septum)
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What next
V contract from bottom up from purkinje fibres
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What is most of human nervous system concerned with
Autonomic nervous system -routine, involuntary jobs such as homeostasis, digestion, posture, breathing
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What is motor functions split into
2 divisions with anatomically distinct neurone
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What are most body organs innervated by
2 separate sets of motor neurones one from the sympathetic system and one from parasympathetic system
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What do these neurones have
opposite or antagonistic effects
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In general what does the sympathetic system stimulate
the fight or flight responses to threatening situations
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While what does the parasympathetic do
relax the body
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HR sympathetic
speeds up HR
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HR parasympathetic
Slows down HR
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If exercise what happens
More cellular respiration in muscles, more co2 in blood, low blood ph, detected by chemoreceptors in aortic and carotid bodies, impulses to cardiovascular centre, impulses to SAN, inc HR
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How else can it be controlled
By pressure receptors
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Where do they occur
Within the walls of the carotid arteries and the aorta
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How do they opperate
When bp is higher than normal they transmit a nervous impulse to the centre in the medulla oblongata that decreases heart rate, this centre sends impulse via parasympathetic nervous system to the SAN of heart which dec the rate at which heart beats
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When bp is lower than normal what happens
They transmit a nervous impulse to the centre in the medulla oblongata that increases HR, this centre sends impulses via the sympathetic nervous system to the SAN of the heart which inc the rate at which the heart beats
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What is Medulla
Part of brain controlling heart rate- cardio vascular centre to ANS that goes to Symp which inc HR noradrenaline or para which dec HR using acetylcholine
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2 types of receptors
Chemo- oxygen/co2 PH- aorta carotid medulla or stretch - blood pressure -aorta/carotid
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Other cards in this set

Card 2

Front

What is atrial systole

Back

Atria contract which pumps blood into ventricles

Card 3

Front

What is ventricular systole

Back

Preview of the front of card 3

Card 4

Front

What is diastole

Back

Preview of the front of card 4

Card 5

Front

What does the SAN do

Back

Preview of the front of card 5
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