control of heart rate Flashcards
what controls the regular beating of the heart
Cardiac Muscle Controls the Regular Beating of the Heart
the cardiac muscle is myogenic, what does this mean
— it can contract and relax with out receiving signals from nerves.
This pattern of contractions controls the regular heartbeat
what is step 1 of controlling the regular beating off the heart
The process starts in the sinoatrial
node (SAN), which is in the wall of
the right atrium.
what is step 2 of controlling the regular beating off the heart
The SAN is like a pacemaker —
it sets the rhythm of the heartbeat
by sending out regular waves of
electrical activity to the atrial walls
what is step 3 of controlling the regular beating off the heart
This causes the right and left atria
to co n tract at the same time
what is step 4 of controlling the regular beating off the heart
A band of non-conducting collagen
tissue prevents the waves of electrical
activity from being passed directly
from the atria to the ventricles
what is step 5 of controlling the regular beating off the heart
Instead, these waves of electrical
activity are transferred from the SAN
to the a trio ventricular node (AVN)
what is step 6 of controlling the regular beating off the heart
The AVN is responsible for passing the
waves o f electrical activity on to the
bundle o f His. But, there’s a slight delay
before the AVN reacts, to make sure the atria have emptied before the ventricles contract.
what is step 7 of controlling the regular beating off the heart
The bundle of His is a group of muscle fibres responsible for conducting the waves of
electrical activity between the ventricles to the apex (bottom) of the heart. The bundle splits
into finer muscle fibres in the right and left ventricle walls, called the Purkyne tissue.
what is step 8 of controlling the regular beating off the heart
The Purkyne tissue carries the waves of electrical activity into the muscular walls of the right and left
ventricles, causing them to contract simultaneously, from the bottom up.
what does control of the heart involve
the Brain and Autonomic Nervous System
what does the sinoatrial node generate
generates electrical impulses that cause the cardiac muscles to contract
what is the rate at which the SAN fires controlled by
The rate at which the SAN fires (i.e . heart rate) is unconsciously controlled by a part of the brain
called the medulla oblongata
how do animals respond to internal stimuli
Animals need to alter their he art rate to respond to internal stimuli, e.g. to prevent fainting due to low
blood pressure or to make sure the heart rate is high enough to sup ply the body with enough oxygen
what are stimuli detected by
Stimuli are detected by pressure receptors and chemical receptors:
what are the pressure receptors called
There are pressure receptors called baroreceptors in the aorta and the carotid arteries
(major arteries in the neck). They’re stimulated by high and low blood pressure
what are the chemical receptors called
There are chemical receptors called chemoreceptors in the aorta, the
carotid arteries and in the medulla. They monitor the oxygen level in the
blood and also carb o n dioxide and pH (which are indicators of 0 level).
what are electrical impulses from receptors sent to
Electrical impulses from receptors are sent to the medulla along sensory neurones.
The medulla processes the information and sends impulses to the SAN along sympathetic or parasympathetic
neurones (which are part of the au to nomic nervous system). There’s more on this on the next page.
what receptor detects high blood pressure
Baroreceptors
detect high
blood pressure.
what receptor detects low blood pressure
Baroreceptors
detect low
blood pressure
what receptor detects High blood
02/low C02
or high pH
levels
Chemoreceptors
detect chemical
changes in the
blood.
what receptor detects low blood O2, high CO2 or low pH levels
Chemoreceptors
detect chemical
changes in the
blood
what neurone and transmitter responds to high blood presure
Impulses are sent to the medulla, which sends impulses along parasympathetic neurones. These secrete acetylcholine (a neurotransmitter), which binds to receptors on the SAN.
what neurone and transmitter responds to low blood pressure
Impulses are sent to the medulla, which sends
impulses along sympathetic neurones. These
secrete noradrenaline (a neurotransmitter),
which binds to receptors on the SAN
what neurone and transmitter responds to high blood O2, low CO2 or high pH levels
Impulses are sent to the medulla, which sends
impulses along parasympathetic neurones.
These secrete ace tylcholine, which binds to
receptors on the SAN
what neurone and transmitter responds to low blood o2, high CO2, or low pH levels
Impulses are sent to the medulla, which
sends impulses along sympathetic neurones.
These secrete noradrenaline, which binds to
receptors on the SAN.
what effector responds to low blood pressure
Cardiac
muscles
what effector responds to high blood pressure
Cardiac
muscles
what effector responds to high blood O2, low CO2 or high pH
Cardiac
muscles
what effector responds to low blood )2, high CO2, or low Ph levels
Cardiac
muscles
what is the response to high blood pressure
Heart rate slows
d own to reduce
blood pressure back
to normal.
what is the response to low blood pressure
Heart rate speeds up
to increase blood
pressure back to
normal.
what is the response to high blood oxygen, low carbon dioxide or high pH levels
Heart rate decreases
to return 02, CO2
and pH levels back
to normal.
what is the response to low blood oxygen, high carbon dioxide or low pH levels
Heart rate increases
to return 02, CO2
and pH levels back
to normal.
