Efferent division
Somatic(voluntary) and autonomic(involuntary)
Somatic
Motoneurons(motorneurons) in somata in CNS -> axon directly to muscle
Autonomic
Pre and postganglionic
Preganlionic
Cells extending axons from the CNS to the autonomic ganglia
Postganglionic
Cells extending axons from the autonomic ganglia to the target
Postganglionic autonomic fibers
Modulate existing activity
Somatic motoneurons
Directly drive muscle contraction
Sympathetic vs parasympathetic differ how?
1) where nerves emerge from CNS
2) location of ganglia
3) neurotransmitter released by postganglionic neurons
Where nerves emerge
Parasympathetic-Brain stem and most inferior parts of the spine
Sympathetic-Most of the spine, but not most inferior parts
Location of ganglia
Parasympathetic-very close to or embedded in target tissue
Sympathetic-chains or collateral ganglia
Transmitter for preganglionic fibers or cells of both divisions
Acetylcholine
Postganglionic cells of both divisions respond via ________(ligand-gated channel) receptors, ionotropic
Nicotinic
Postganglionic parasympathetic neurons also release? Targets respond via _________ receptors, metabotropic?
Acetylcholine;Muscarinic
The neurotransmitter for postganglionic sympathetic cells is?
Norepinephrine (NE)
Norepinephrine acts via ________ receptors which operate metabotropically
Adrenergic
Some preganglionic sympathetic fibers synapse onto endocrine cells in the ________? They secrete ________ and a smaller amount of ________ as hormones?
Adrenal medulla; Epinephrine and Norepinephrine
Where is the adrenal medulla located?
Above and next to the kidney
What is the adrenal medulla?
A modified sympathetic ganglion
What makes the adrenal medulla different than regular "postganglionic" cells?
They lack axons and secrete hormones into the interstitial fluid
The adrenal medulla effects usually reinforce the effects of which transmitter?
Norepinephrine
Parasympathetic and sympathetic both display tone
Some level of activity that can be increased or decreased
Which division (parasympathetic or sympathetic) tends to act as a whole?
Sympathetic
True or false: All tissues are innervated by both divisions (parasympathetic and sympathetic)
False: Only some tissues are innervated by both.
True or false: Often the two divisions of the autonomic nervous system have a synergistic effect.
False: Often the two divisions have an opposing effect
What are some characteristics of skeletal muscle?
1) Usually attached to skeleton
2) Voluntary
3) Striped or striated
4) Contractions are always triggered by a motor neuron
If muscle contractions are triggered by a motor neuron, the contractions are considered _________?
Neurogenic
Define neurogenic
Originating from the nervous system
Muscle cells are called?
Myofibers or muscle fibers
When tension or force is applied to a muscle, it is called a ________?
Contraction
A contraction pulls on _______?
Tendons
What is an isometric contraction?
Where the length of the muscle does not change.
What is an isotonic contraction?
It is where the length of the muscle changes.
Somatic motoneurons
Directly drive muscle contraction
What is the contraction called when the muscle gets shorter? Longer?
Concentric; Eccentric
2 cerebra are made up of______
2 cerebra cortices and basal nuclei or basal ganglia
Cerebral cortex is made up of
Frontal, parietal, occipital, temporal lobes
What structures are found under the cerebra?
Two thalami
What structures are found under thalami
Two hypothalami
Primitive" brain
Medula, midbrain, pons, cerebellum
Phrenology
No two areas share the same function
If you injure a single part of the brain what is the effect and does that support or refute phrenology?
There is slight impairment of many functions. Refutes phrenology.
What happened when there was a lesion on the posterior frontal lobe
Broca's area, we speak with left hemisphere, shows that there is some specialization in specific areas of the brain
What happened when the posterior edge of the frontal lobe in dogs was electrically stimulated
Triggered movement on opposite side. Conclusion that there was some specialization
Carl Wenicke's stroke patient had a lesion where and what was the result, and what were his conclusions?
Posterior temporal lobe, could not comprehend speech, fundamental functions are assigned to specific cortical regions. Higher functions arise through interconnections
What structures do sense stimuli go through
Primary sensory neurons, projection neurons in spinal cord, projection neurons in thalamus, anterior parietal cortex
What is the anterior parietal cortex also called?
Somatosensory cortex, somatic sensory cortex
Thalamus
Projection neurons+intrinsic neurons, short distance communication
Where do neurons in the somatosensory cortex have receptor fields?
Body surface
Explain relationship in regard to acuity of neurons and their receptive fields
Few neurons, large receptive fields, low acuity
What makes up the optic nerve?
Axons of retinas projections neurons called ganglion cells
Explain the process of visual stimulation
Retina, optic nerve, thalamus, occipital lobe
True or false: all info from her right eye goes to the left side of the brain and vice versa
False, only part crosses over
Partial crossover of visual stimulation allows areas of the brain to get input from both eyes, how is this helpful?
Depth perception
How does auditory stimulation travel
Thalamus, temporal lobe
What is the result of partial crossover of auditory stimulation?
allows you to determine location of source of sound
Perception is done by the __________ and _______
cortex, thalamus
if you electronically stimulate the cortex what is the result and are you testing for necessity or sufficiency?
there is perceptions, sufficiency
if you damage the cortex what is the result and are you testing for necessity or sufficiency?
impairs perception, necessity
thalamic(definition)
awareness
all sense except ________ travel through the thalamus
smell(olfaction)
what are areas that receive input directly from the thalamus described as?
primary ex. primary visual, primary auditory
True or false: areas adjacent to the primary areas do not process information
false, they do more processing
adjacent areas to the primary areas are called
secondary _______ cortex, or _______ association cortex (visual, auditory, somatosensory etc)
What is the area called where all sense are combined?
general interpretive center, parietal-temporal-occiptal association cortex, or gnostic region
What is cerebral lateralization
specialization of left or right side in various functions (eg speech)
how do you test for lateralization?
WADA testing-inject Na amytal into left or right corotid and that anesthetizes that hemisphere and then you ask the patient to speak,
if anesthetizing a hemisphere prevents speaking, is the hemisphere considered dominant?
yes
what is the dominant hemisphere
the hemisphere responsible for a function, such as speech and language
Are right hemisphere dominant people more artistic?
No
What is the function of the non-speech side of Broca's area and Wernicke's area
express emotion in speech, understand emotion in speech
What is the difference between the dominant and dominant hemispheres when decoding signals?
the dominant decodes signals in sequence, non-dominant decodes signals that arrive all at the same time and work in object and facial recognition and spatial relations
the posterior frontal lobe is also known as
primary motor cortex
how do nerves travel to muscles
neurons in primary motor cortex, motor neurons in spinal cord, those synapse directly onto skeletal muscle cells
True or False: all motor signals cross over
TRUE
Besides motor functions, what is the frontal lobe responsible for?
plan future movements elaborated in humans-ambition, consequences, no long trains of thought, short attention span
what is the function of the hypothalamus?
involuntary physiology-eating behavior, water balance, temperature control; pleasure, fear and anger centers
Cerebellum function
fine tunes motor acts, predicts trajectories, learning timing of certain movements
pons
some cell bodies, not well defined.
has tracts connecting cerebellum and cerebral cortex. respiration and sleep-wake cycle
medulla
involuntary physiology-respiration, blood pressure, heart rate
One motor neuron and the myofibers it controls is called?
Motor unit
What are synapses called
Neuromuscular junctions
How many motor neurons do myofibers receive synaptic input from?
One
Whats the sequence for muscle stimulation?
1)Motor neuron fires one action potential
2)One event of synaptic transmission at each innervated myofiber
3)one large depolarization at each innervated at each myofiber
4)Each myofiber fires one action potential
5)Each myofiber has one event of excitation-contraction coupling
6)Each myofiber engages in the cross-bridge cycle
7)Each myofiber generates one pulse of tension called a twitch
What are the step of synaptic transmission at the neuromuscular junction(NMJ)?
1)Action potential reaches terminal at NMJ
2)Depolarization opens voltage gated calcium channels
3)Influx of calcium
4)Exocytosis of ACh (neurotransmitter regulated secretion)
5)Doffuses across synaptic cleft
6)Binds nicotinic receptor and opens channels(mixed ion channel)
7)Pna=Pk results in depolarization
8)One spike in myofiber
9)AChE breaks down ACh which terminates the signal
10)Choline is taken back up into the pre-synaptic membrane
How does synaptic transmission at the NMJ differ than in the CNS?
The response is different.
What is it called when a spike leads to increased concentration of Ca2+ inside the cell?
Excitation-Contraction (EC coupling)
Mechanism of EC coupling?
1)Spike pass along transverse tubules
2)Confirmation change in a voltage-sensor protein aka dihydropyridine receptor in the transverse tubule
3)Conformational change in the DHP receptor causes Ca2+ channels int he sarcoplasmic reticulum to open due to physical, mechanical connection (mechanically gated channels)
4)Ca2+ pours out of SR into cytosol
5)DHP receptor reverts to intial confirmation causing Ca2+ channels to close
6)Ca2+ pumped back into SR by Ca2+ ATPase. Primary active transport (lots of ATP used)
Myofibrils are found where?
Myofibers
A-band
Thick filaments made of myosin
I-band
No myosin (actin, troponin, and tropomyosin found here and extend into A-band)
Z-lines
Anchor the thin filaments
Z-line to Z-line is called what?
One sarcomere aka one muscle unit
What is happening when muscles shorten?
Thin and thick filaments slide past each other, myofibrils get shorter, myofibers get shorter, and muscle gets shorter
Cross-Bridge cycle
Causes the filaments to slide
1)Myosin heads are attached to ADP and Pi
2)Ca2+ binds troponin and changes its shape
3)Causes tropomyosin to move and expose a myosin head binding site on actin
4)Myosin binds actin
5)Releases phosphate (Pi)
6)Myosin heads swivel forcing filaments past each other
7)Myosin heads release ADP
8)ATP attaches to myosin head
9)Causing it to separate from actin
10)The breakdown of ATP (ATP -> ADP + Pi) causes head to be cocked back
which are larger, skeletal or smooth muscle cells?
skeletal
Which contracts and relaxes more slowly, skeletal or smooth muscle cells?
smooth
Which varies more in from place to place, skeletal or smooth muscle cells?
smooth
Where does the Ca2+ that causes the contraction of smooth muscle come from
sarcoplasmic reticulum and extracellular fluid
What is another name for single-unit smooth muscle and why is it so named?
visceral smooth muscle because it lines the inside of internal organs (ie the intestine and blood vessels)
True or False: single-unit smooth muscle cells all contract independently due to different action potentials
False; single-unit smooth muscle cells contract as a SINGLE UNIT due to a single action potential that travels from cell to cell via gap junctions which electrically connect all cells in the unit
How does the action potential spread from cell to cell in single-unit smooth muscle?
gap junctions
If single-unit smooth muscle cells are already contracted and an increase in force is needed, what would need to occur first in order for the force to be increased?
the single-unit smooth muscle cells would need to relax because the whole unit contracts together leaving no reserve units to be recruited
What determines the force of the contraction in single-unit smooth muscle
the amount of Ca2+ entering the cell
How does calcium cause contraction in smooth muscle?
Ca2+ initiates a cascade that ends with the phosphorylation of myosin
1) increase in cytosolic Ca2+ initiates contraction. Ca2+ is released from the sarcoplasmic reticulum and also enters from the extracellular fluid
2) Ca2+ binds to calmodulin(binding protein found in cytosol)
3)Ca2+ binding to calmodulin is the first step in a cascade that ends in phosphorylation of myosin
4) phosphorylation of myosin enhances mysosin ATPase activity and results in contraction
tendons
made of collagen, attach skeletal muscle to bones
origin(skeletal muscle)
the end of the muscle that is attached closest to the trunk or to the more stationary bone
insertion(skeletal muscle)
the end of the muscle that is attached more distal or more mobile attachment
flexor(skeletal muscle)
the center of the connected bones are brought closer together when the muscle contracts, movement is called FLEXION
extensor(skeletal muscle)
the center of the connected bones move away from each other when the muscle contracts, movement is called EXTENSION
antagonistic muscle groups
flexor-extensor pairs; each muscle can only move in one direction, so in order to move the bone in opposing directions, you would need both a flexor and an extensor
In skeletal muscle contraction, if Ca2+ is present after a single cross-bridge cycle is completed, what happens?
myosin head attaches to actin and cycle repeats
In skeletal muscle contraction, if Ca2+ is removed after a single cross-bridge cycle is completed, what happens?
tropomyosin moves back over the myosin binding site and blocks it
tension also called
force
Is tension exerted on muscles or by them?
tension/force is exerted by muscles
what are two ways we can control the amount of tension generated by muscles?
spike frequency in motorneurons and the size and number of motor units involved
what happens when sarcomeres shorten?
stretch the connective tissue in the muscle and the tendons
what causes slack in the skeletal muscle contraction system?
stretchable components called called the "series elastic elements
why does it take time for force to be exerted on the "series elastic elements"(tendons and connective tissues)
in order for force to be exerted on the elastic elements, all slack must be removed (water skiing analogy)
Explain the difference in force exerted on elastic attachments by skeletal muscles when there is a single twitch and when there is a high frequency(multiple) of twitches
When there is a single twitch, Ca is removed from cytosol before the series elastic component is taken up, when there is a high frequency of EC(excitation-contraction) coupling events allow Ca to stay in cytosol longer thus allowing for the slack to be taken up and more force can be exerted
If more force is needed, what does that mean in regard to motor units
More motor units activated and they are larger
The more tension the (more/less) motor units activated, and the (bigger/smaller) those motor units are.
More, bigger
Recruitment of motor units is ____ for low tension and ____ for very high tension
Asynchronous, synchronous
Motor units are specialized for ___ for low tensions and for ___ for high tension
Sustained aerobic metabolism, brief fermentation
Spike frequency in motor units is ___ for low tension and ___ for high tension
Low, high
The result of tension is ___ in low tension, ___ in more tension, ___ in lots of tension
Twitches, unfused tetanus, fused tetanus
How is tension influenced by the length of muscle fibers?
The longer the fibers, the more stretched out they generally are, so it takes more force for tension to be increased
What happens when the muscle fiber length is larger than optimal?
Some myosin heads don't overlap with thin filaments
What happens when the length of a muscle fiber is less than optimal
Thin filaments overlap each other and block myosin binding sites, thick filaments bump into Z-lines and buckle
At rest, skeletal muscle relies on ____
Beta oxidation
The catabolism of fatty acids is an example of____
Beta oxidation
Phosphocreatine plays a particularly important role in tissues that have high, fluctuating energy demands such as muscle. How is a pool of creatine phosphate maintained?
In excess of ATP, it reacts with creatine leaving ADP and creatine phosphate. The creatine phosphate is used after an intense muscular effort by donating a phosphate to ADP to form ATP
Le Chatelier's principle
If external stress is applied to a system in equilibrium, the system will adjust such that the stress is partially offset
Explain the process that takes place in muscles during moderate exercise
Existing ATP and ATP from phosphocreatine are used for aerobic respiration
Explain the process that takes place in muscles with intense exercise
Existing ATP and ATP from phosphocreatine leads to aerobic respiration and fermentation which leads to fatigue
Fermentation generates____
Lactic acid
Does lactic acid cause fatigue?
No
Frequent use of muscles causes myofibers to secrete____
Myokines(muscle cytokines)
The secretion of myokines leads to___
Enlargement of existing muscle cells
Hypertrophy
Enlargement of muscle cells
IGF-I (insulin growth factor) use autocrine signaling, what does this mean?
It acts on the same cell that secretes it
What are the 3 different types of muscle fibers?
Slow-twitch oxidative, slow-twitch oxidative-glycolytic, fast-twitch glycolytic
Myoglobin
A red hemoglobin-like molecule present in the cytosol of skeletal and cardiac muscle cells
Myoglobin reversibly binds ____
Oxygen
What is myoglobins role in aerobic respiration?
In blood, oxygen is removed from hemoglobin and then diffused into muscle fibers where it binds to myoglobin and is stored
How do we know myoglobin supports aerobic respiration?
Blocking its ability to bind oxygen causes decreased oxygen consumption and decreased work is performed
What were the results of myoglobin knock out mice
Healthy, increased hermatocrit, high capillary density
Hermatocrit
The amount of blood volume occupied by red blood cells
Hypoxia
Low oxygen
How does myoglobin support aerobic respiration?
Functions as an oxygen store OR myoglobin increases the diffusion rate of oxygen within the myofiber
Myoglobin has a (higher/lower) affinity for oxygen than hemoglobin
Higher
What happens to the concentration of O2 inside the cell during muscle contractions and why does this occur?
The concentration of O2 decreases because the blood vessels in the muscle are compressed
How does the circulatory system affect the interstitial fluid?
It controls the quality of the interstitial fluid
What makes up the cardiovascular system?
Heart, blood vessels, blood
Division of circulation system in the lungs is called____
Pulmonary circulation
Division of circulatory system throughout majority of body is called ____
Systemic circulation
Division of circulatory system in the heart is called______
Coronary circulation
auscultation
listening to the heart through the chest wall
Gallops
with certain abnormal conditions, extra heart sounds can become audible with a stethoscope
What are 2 other heart sounds and what causes them?
clicking caused by an abnormal movement of one of the valves
murmurs caused by blood leaking through an incompletely closed valve
The blood flows through the right side of the heart _______ to ________
systemic to pulmonary
The blood flows through the left side of the heart _____ to ______
pulmonary to systemic
The blood in arteries flows (towards/away from) the heart and in veins flows (towards/away from) the heart
away from, towards
What is the main artery leading away from the heart
aorta
What are the main systemic veins leading into the heart?
superior/inferior vena cava
What is the main pulmonary artery?
pulmonary trunk
What are the main pulmonary veins?
pulmonary veins
Describe the cycle of the blood through the circulatory system
right atrium, tricuspid valve, right ventricle, semilunar valve, pulmonary arteries, lungs, pulmonary veins, left atrium, bicuspid valve(mitrol valve), left ventricle, aortic valve, aorta, systemic circulation, inferior/superior vena cava
What is compliance and elasticity in arteries?
compliance: artery stretching
elasticity: artery springing back
What happens to arteries during ventricular diastole and systole?
during systole, the arteries stretch and during diastole, the arteries spring back
What is happening to blood during ventricular diastole?
blood keeps flowing
Frank-Starling mechanism
the more the ventricles stretch, the more powerfully they contract
end-diastolic volume
the volume of ventricle right before it contracts
stroke volume
volume of blood ejected per contraction
What is the timing of the heart cycle's components at rest?
quiescent: 400 ms
atrial systole: 100 ms
ventricular systole: 300 ms
total:800 ms
cardiac muscle cells
cardiac myocytes, striated, transverse tubules and sarcoplasmic reticulum
How are cardiac muscle cells connected to each other?
gap junctions and intercalated discs
what is name of the property where the heart contracts on its own without nervous stimulation and what is the name of the contraction?
automaticity or autorhythmicity, myogenic contraction
automaticity is due to specialized myocytes that do what?
generate action potential spontaneously
pass action potentials very quickly
where are the specialized myocytes located and what is important about that location?
sinoatrial node (SA node) which is where the action potential begins
cells at the SA node spike around 70-80 beats per minutes. this determines what?
heart rate
cells in the AV node (slow/fast) conduction velocity making the impulse (delayed/sped up).
slow, delayed
What makes the bundle of His?
left and right bundle branches which each have Purkinje fibers
What would happen if skeletal myofibers were connected by gap junctions?
all motor units would contract instead of one
why is the impulse normally generated in the sinus node instead of within the ventricular conduction system?
It fires more frequently and the cells at the bottom of the heart that fires less frequently don't get a chance.
What would happen if the impulse couldn't pass through the AV node?
the cells at the bottom of the heart begin to fire on their own and act as a pace maker
What determines the duration of a contraction?
the duration of the action potential
EC coupling process
1) spike in myocite
2) spike in t-tubule
3) depolarization opens voltage gated Ca2+ channels
4) Ca2+ enters
5) Ca2+ binds to Ca2+ channels on the SR and opens them this process is called calcium induced calcium release(CICR)
6) Ca2+ channels close
7) Ca2+ removed by several types of active transport
How is cardiac EC coupling different from skeletal EC coupling?
DHP receptors(m-gated channels)
How does calcium trigger the cross bridge cycle?
it works just like in skeletal muscle
Gases and liquids are called?
Fluids, which have the same properties. They flow from high pressure to low pressure.
What causes valves to "pop" open?
Increased pressures forces them open.
What is quiescent period?
Atrial and ventricular diastole.
What happens when atrial pressure is greater than ventricular pressure?
The mitral (bicuspid) valve opens and blood flows through.
When aortic pressure is equal to 90 mm Hg but greater than the ventricular pressure, what happens?
The aortic semilunar valve is closed.
What happens during atrial systole?
Atrium contracts, and pushes a little more blood into the ventricles. The final volume is end-diastolic volume.
When the ventricle enters systole, what happens to the atrium?
The atrium enters diastole.
Ventricular systole cause the ventricular pressure to rise. When the ventricular pressure is greater than the atrial pressure, what happens?
The mitral(biscupid) valve closes.
When the aortic pressure is greater than the ventricular pressure after the mitral valve closes, what then happens?
aoritc semilunar valve is closed
period of isovolumic(isovolumetric) ventricular contraction
when ventricle is in systole and both valves are closed
When the atrium fills and the ventricle is in systole, what occurs?
ventricular ejection
When ventricular pressure is greater than aortic pressure what happens?
semilunar valve opens
What happens to the pressure when ventricle enters diastole?
The pressure decreases rapidly.
When the ventricle enters diastole and the pressure falls rapidly, what happens to the semilunar valve?
It closes.
Stroke volume measures the __________ of the contraction.
Force
Isovolumetric relaxation
Ventricular pressure is greater than atrial pressure.
When does the mitral valve open?
When the ventricular pressure is less than the atrial pressure.
What is the importance of blood pressure in large systemic arteries like the aorta?
Pushes the blood through the vessels and stretches the arteries (compliance).
Systolic blood pressure
Systole pressure in left ventricle is 120 mm Hg.
Diastolic blood pressure
Recoil in diastole which exerts about 80 mm Hg (elasticity) and this closes the aortic semilunar valve and keeps blood moving forwards.
Pathologies of the heart
1)Atherosclerosis-angina or myocardial infarction
2)Valve problems
3)Chronic/Congestive heart failure
4)Disrhythmias (arhythmia)
Atherosclerosis
The wall of an artery becomes narrow from a cholesterol rich plaque.
Where does atherosclerosis take place?
Left side of the heart.
Where does plaque build up occur?
Between endothelial cells and connective tissue.
Explain how atherosclerosis can lead to angina (pain with exertion)?
The vessel can suplly enough oxygen to support low levels of heart activity but not the increased activity that goes with stress or exertion.
Hypoxia with stress or exertion causes what?
Pain
Agina pectoris
Pain in the chest or arm treated with nitroglycerin.
Explain how atherosclerosis can lead to myocardial infarction (heart attack)?
The plaque may rupture and a blood clot forms at the rupture site. The clot may break free and block the vessel somewhere down stream. A blocked coronary artery qualifies as a heart attack.
How does a clot form?
Blood exposed to collagen.
What are the ways heart attack can lead to death?
1)Reduced cardiac output
2)Damming of blood in pulmonary circulation
3)Ventricular fibrillation
What is reduced cardiac output, and what does it cause?
The lowering of the volume of blood pumped per minute. The heart cannot sustain itself because the blood is required to sustain tissue.
What are the consequences of damming of blood in pulmonary circulation?
Heart attacks nearly always occur on the left side. If the left ventricle is weakened, it cannot keep up with the right ventricle. Starlings law cannot match the two sides. Pulmonary pressure increases forcing fluid out of blood vessels into the lungs.
What causes a ventricle to be weakened?
When any of the tissue is damaged, it is replaced with scar tissue. This makes it weaker.
Pulmonary adema
Adema in the lungs. Build up of fluid
Ventricular fibrillation
A potentially fatal abnormal rhythm. The ventricles quiver rather than beat in an unified fashion
What is it called when a valve won't close completely?
the valve is incompetent (valvular insufficiency)
What is it called when a valve won't open completely?
the valve is stenotic (stenosis)
chronic (congestive) heart failure
heart progressively weakens until it can no longer pump enough blood to sustain itself
chronic
progressive over months or years
what are some potential causes of chronic heart failure?
damage from a heart attack, genetic disease (mutated proteins), increased workload (incompetent/stenotic valves)
What does valve incompetence cause?
regurgitation, blood flowing backwards
Explain how chronic heart failure can be fatal.
Weak heart, pumps less blood. Heart gets weaker. Heart pumps less blood. Heart gets weaker. Heart cannot sustain itself. Or ventricular fibrillation. DEAD!
Electrocardiagram
Also called electromyogram and it is the electrocellular recording of voltage changes caused by heart electrical activity
How is an EKG taken
Electrodes are placed on body.
EKG deflections on the trace
caused by waves of depolarization and re-polarization SWEEPING across myocardium.
Wave of depolarization sweeps across atria
P wave
Atria depolarized
no wave
Wave of depolarization sweeps across the ventricles
QRS complex
Ventricles depolarized
No wave
Wave of repolarization of the atria
T wave
What is an EKG used for
diagnosing disrhythmias
Dysrhythmia
abnormal heart rhythm often called an arrhythmia
Sinus bradycardia
Heart rate < 60 beats per minute usually someone in good shape
Sinus tachycardia
Heart rate > 100 beats per minute usually due to stress or heart failure or hyperthyroidism
Atrial fibrillation
Patches of atrial myocardium contract independently of one another. Atria do not contract as a whole
No P wave
Might be replaced by a heavy base line
QRS-T complexes
Occur at random intervals and at high frequencies
1st degree AV block
Unusually slow conduction in AV node or in the bundles of His.
P to Q interval with a 1st degree AV block
> 200 ms asymptomatic, but can progress to 2nd and 3rd blocks
2nd degree AV block
Several kinds. Involve some impulses passing AV node and some not. May be due to prior heart attack or an indication of a present heart attack.
3rd degree AV block
No impulses pass through the AV node. Commonly someone may suddenly progress from 2nd to 3rd degree block.
Pacemaker
Wires threaded into the heart and attached to the inside of a ventricle and sometimes atrium. Driven by a subcutaneous stimulator.
Premature ventricular contraction (PVC)
aka premature ventricular complex or ventricular premature contraction (VPC)
What is a PVC?
Where the cells fire prematurely, generating an action potential, and the ventricles then contract prematurely. An ectopic site triggers spike instead of waiting for one from conducting system.
What does a PVC look like on an EKG?
It appears as a highly distorted PVC.
What happens when the correct impulse arrives when someone is having a PVC?
The ventricles are refractory and they do not beat (skipped beat)
True or False: PVC's during the Q wave can lead to death.
False, PVC's during the T wave can cause death.
When does ventricular fibrillation usually occur
During or after a heart attack. Survivors of heart attacks can be more prone to v-fib due to damage
Defibrillation
A large voltage applied for a very short period of time. Coordinates myocytes. Now often chronically installed in patients.
Pressure in large systemic arteries is determined by what?
Cardiac Output (CO) and Total Principal Rsistance (TPR)
Blood pressure is proportional to what?
CO x TPR
Cardiac Output
amount of blood pumped from left ventricle per minute
TPR
is the resistance of flow through circulation. most of it depends on the diameter of arterioles
Heart Rate (HR) is measured in what units?
beats/minutes
Stroke Volume (SV) is measured in what units?
mL/beat
Cardiac output sustains ____________ and not _____________.
life; blood pressure (just needs to be high enough to keep you from passing out)
Baroreceptors
Sensory neurons with dendrites wrapped around large arteries. Especially the aorta and carotids.
Blood pressure stretches carotid bodies
Spikes are then sent to the brain
Blood pressure drops (Baroreceptors)
Fewer spikes are sent to the brain so reflex is initiated.
Baroreceptor reflex
Corrects the blood pressure in either direction that it needs. It is always in action. It does NOT hold it constant. Just limits fluctuations.
Homeostasis
Limiting the fluctuations in one's internal environment. Usually involves negative feedback inhibition.
What happens if you lose a lot of blood?
The result is hemorrhagic shock or hypovolemic shock
Decreased blood volume causes a (increase/decrease) in cardiac output.
Decrease
Shock
Insufficient cardiac output to provide oxygen and nutrient to tissues
If someone has congestive heart failure, why to do they commonly have pale skin and sinus tachycardia?
Congestive heart failure causes the heart to weaken and therefore be able to pump blood less efficiently. The pale skin is due to slower circulation of blood. Tachycardia occurs as a way to make up for the heart not being able to function as efficiently