topic 9. powerpoint 9.1 Flashcards
What is cardiac output
CO= SV x HR
What is the difference between preload and afterload?
preload is end-diastolic volume aka amount of ventricular stretch
Afterload: the amount of pressure needed in the ventricles to surmount the aortic
and pulmonary pressure and thus propel blood into the aorta and lungs
How can the force of contraction be varied to change the stroke volume?
More blood returns, increases preload because end-diastolic volume is greater. This increases contractions and thus stroke volume(ml/beat pumped out left ventricle)
What is a sarcomere?
Functional unit of contraction of muscle fiber. Made up of myofilaments, actin and myosin. During muscle contraction, myosin heads attaches to actin and pulls towards center of sarcomere, causing muscle to shorten. Slide mechanism allows for movement
Frank-Starling Mechanism
physiological mechanism that allows the heart to adjust its pumping strength[increase contraction] based on the volume of blood it receives[preload]
If the ventricular end diastolic volume increases, we can expect the ___ to increase
stroke volume
EDV happens before SV
Besides greater blood return influencing contraction, what 2 other things can affect the force of contraction?
-Sympathetic Activity
-Parasympathetic Activity
Sympathetic Activity and Parasympathetic Activity can innervate the heart by?
influencing heart rate and stroke volume, ensuring that bp, blood O2/ CO2, and blood PH are in homeostasis
What are the two parts of the nervous system?
CNS: central nervous system
-brain and spinal cord
PNS: peripheral nervous system
-connect CNS to limbs and organs
-afferent and efferent
PNS has what two divisions?
Afferent: transmit signals to CNS
*includes sensory neurons/transmits sensory info
Efferent: transmit signals from CNS
**carries signals to muscles and glands
Efferent system has what two divisions?
Somatic:
Autonomic
What is somatic?
One of the two efferent divisions:
-mostly voluntary
-controls movements that are conscious
-utilizes motor neurons
-carries efferent signals from CNS to skeletal muscle
What is ANS?
The autonomic nervous system, one of the two efferent divisions
-a collection of motor neurons(ganglia) and the axonal connections of those neurons
-functions below the level of consciousness(involuntary)
Name the two divisions of the ANS?
Sympathetic
Parasympathetic
Sympathetic division
Fight or flight
Response to high emotional activity can result in increased bp, heart rate, suppress digestion
Parasympathetic division
Rest and digest
-located around the sympathetic nerve
-house keeping functions like digestion
What is the vagus nerve?
Cranial nerve 10, conveys sensory info about the state of the viscera to the CNS
viscera-internal organs such as those in abdominal regions
Vagus nerve carries ___ to the
heart (primarily)
parasympathetic nerve fibers
Parasympathetic nerve stimulation has an ____ effect-decreases____
inhibitory, heart rate
Explain how parasympathetic nerve stimulation decreases heart rate
Parasympathetic neurons are found in the vagus nerve, produce acetylcholine and exerts an inhibitory effect on ligand gated channels on cardiac cell membrane channels in the SA node by forcing k+ out, causing hyperpolarization. Hyperpolarization takes longer to depolarize, resulting in decrease in heart rate.
Neurotransmitter receptors can be classified into two categories:
metabotropic and ionotropic,
What is the difference between metabotropic and ionotropic?
Ionotropic receptors form an ion channel pore, while metabotropic receptors are indirectly linked with ion-channels through signal transduction mechanisms.
Acetylcholine binds to what receptor in the heart?
Metabotropic receptors; Muscarinic acetylcholine receptors
After acetylcholine binds to M2 Muscarinic receptors in the heart causing a inhibitory effect, the ___ can have stimulatory actions on the heart.
sympathetic nervous system
How does the sympathetic nervous system increase heart rate?
Sympathetic nerves from the thoracic region of the spinal cord project to the heart as cardiac nerve and innervate various components, increasing heart rate and force of contraction.
what is the cardioregulatory center?
A region in the brainstem(medulla) that is responsible for regulating and controlling the activity of the heart by sending signals to the heart via the autonomic nervous system to adjust heart rate and force of contraction.
parasympathetic nerve fibers extend to heart via __ and sympathetic nerve fibers extend to heart via ______
vagus nerve, cardiac nerve
How is epinephrine/norepinephrine secreted? Effect?
Sympathetic nerve fibers extend to adrenal medulla, sympathetic neurons increase secretion of epinephrine and norepinephrine, which increase HR and SV
How does norepinephrine have a stimulatory effect?
Increases the rate and degree of cardiac muscle depolarization, which causes an increase in the frequency of the action potential and the force and velocity of the
contraction.
Sympathetic effect results in increase in HR and SV, what two neurotransmitters are involved?
norepinephrine & epinephrine; which are classified as catecholamines aks derived from tyrosine *also act as hormones
Norepinephrine and epinephrine, which is derived from the other?
Epinephrine is derived/synthesized from norepinephrine
norepinephrine and epinephrine bind to what receptors?
note: both are catecholamines
Catecholamines bind to two different classes of receptors termed the α- and β-
adrenergic receptors
activation of β-adrenergic receptors leads to what?
can lead to an increase in heart rate and force of contraction.
how can you remember what neurotransmitter binds to α- and β-
adrenergic receptors?
adrenergic = adrenaline aka epinephrine
answer: epinephrine and norepinephrine
Epinephrine and norepinephrine are also called___
adrenergic neurotransmitters;
Noradrenergic neurons specifically secrete ___ as a neurotransmitter, while ___ secrete both norepinephrine and epinephrine.
norepinephrine, adrenergic neurons
agonist
agonist is a substance or molecule that activates or stimulates a receptor in the body
norepinephrine is what class of neurotransmitter?
Norepinephrine is metabotropic.
norepinephrine acts as an agonist for what? Explain the process
β-adrenergic receptors
1. metabotropic neurotransmitter, causes G-protein mediated synthesis and accumulation of cAMP
2. Ca+ channels open on plasma membrane and sarcoplasmic reticulum allowing depolarization
3. calcium troponin reaction
4.reuptake of Ca+ into SR
-overall it’s how increased force and velocity of contraction, HR is up
explain the calcium troponin reaction
Within cardiac muscle cells, calcium ions bind to troponin, it causes a conformational change that allows the actin and myosin filaments in the muscle fibers to interact and slide past each other, resulting in muscle contraction
Besides increasing force and velocity of contraction, what other sympathetic activities is epinephrine involved in?
increases cardiac output and blood glucose levels
if Ca+ enters back into the sarcoplasmic recitulm, what can we expect?
heart to relax, when Ca+ was leaving it increased heart rate and so we can expect the opposite
How can we increases heart rate?
beats can be shorter
resulting in more beats per unit time
By increasing contractility, you…
more completely empty the heart of blood because increased contraction means more blood is pumped out
t/F if you have the same end diastolic volume, you can’t increase heart contracility
false, the heart muscle is able to generate a stronger force of contraction, resulting in more blood being pumped out of the ventricles per beat. Ex: epinephrine can make this happen
