Background info part 2 Flashcards
components that make up the ANS
- sensory (afferent) and motor (efferent)
- sympathetic and parasympathetic
-affects cardiac function, digestion, respiration, salivation, sweating, pupil diameter, urination, and sexual arousal
sympathetic nervous system
outflow comes from the thoraco-lumbar region
- fight or flight
the neurotransmitter at the postganglionic nerve endings of the sympathetic NS is ? Whats the exception?
norepinephrine; exceptions are that ACh is the neurotransmitter for sympathetic postganglionic innervation of sweat glands
sympathetic preganglionic neurons are found in the?
- lateral horn of the grey matter in the thoracic and lumbar regions of the spinal cord
parasympathetic nervous system
outflow comes from the cranial and sacral regions of the spinal cord
- relaxed state
postganglionic nerve endings of the PNS is?
acetylcholine (ACh)
the parasympathetic preganglionic neurons are found in the?
cranial and sacral regions
preganglionic nerve fibers are contained in?
some of the cranial nerves (III - oculomotor, VII - facial, IX - glossopharyngeal, and X - vagus), in the sacral region the fibers emerge from the cord as the sacral outflow and innervate the gut and sexual organs
the fibers of the parasympathetic preganglionic neurons generally synapse with their?
post-ganglionic neurons close to the organ innervated, the fibers are very short
the neurotransmitter released from both preganglionic and postganglionic nerves is?
acetylcholine
how is median nerve simulation impacted when measuring autonomic nervous system skin potentials
- stimulation can be on either side
- it is stimulation of afferent fibers that is important in establishing the sweating response reflex
function of ANS in the cardiovascular system
regulates blood pressure by affecting heart rate and peripheral resistance
function of ANS in the skin
the sympathetic system supplies the blood vessels of the skin; hence it is involved in thermoregulation, also supplies the sweat glands
function of ANS in the gastrointestinal system
regulates all aspects of gastrointestinal function
function of ANS in the urinary and reproductive systems
innervates the bladder and internal urethral sphincter, also supplies the erectile tissue
function of ANS in the eyes
- the parasympathetic system supplies the pupillary and ciliary muscles
- the sympathetic system supplies muscle in the eyelids
RR interval
- one cycle
- a function of intrinsic properties of the sinus node as well as autonomic influences
how is sweat production are used to assess autonomic nerve function?
- eccrine sweat glands are innervated by sympathetic nerves
- sympathetic activity causes an increase in sweat production, which is commonly assessed by measuring an increase in skin conductance
- an alternative that you will use here is to simply measure changes in potential across the hand and foot following peripheral nerve stimulation
how is heart rate variability, are used to assess autonomic nerve function?
- heart rate varies from beat to beat as a consequence of changes in parasympathetic and sympathetic nerve activity
- measurement of 20 to 40 consecutive RR intervals on an ECG during quiet breathing followed by a further 20 to 40 consecutive intervals during deep breathing provides a clear indication of the extent of the autonomic control of the heart
how postural changes are used to assess autonomic nerve function
- an abrupt change from a supine to an erect posture is associated with alterations in heart rate and blood pressure
- any decrease in blood pressure results in increased sympathetic activity with an increase in the heart rate and force of contraction
orthostatic hypotension
- people who experience a decrease of 20 mmHg systolic pressure or at least 10 mmHg diastolic pressure within three minutes of standing
- often associated with autonomic dysfunction, although there are a variety of other causes.
how are pupillary reflexes used to assess autonomic nerve function
- pupillary light reflex involves four neurons that convey information from the retina to the midbrain, and then back to the small muscles of the eye
pupillary reflexes (PNS)
parasympathetic motor nerve fibers innervate the circular muscles of the iris; they cause the iris to constrict, reducing the aperture (diameter) of the pupil
pupillary reflexes (SNS)
- sympathetic motor nerve fibers supply the radial muscles of the iris; contraction of the radial muscles leads to dilation of the pupil
- sympathetic fibers also innervate muscles in the eyelids, holding the upper eyelid open
- damage to the sympathetic supply can result in a drooping upper eyelid (ptosis) and in a constricted pupil (Horner’s syndrome).
various neuropathies that can potentially be encountered by people with diabetes
peripheral, autonomic, proximal or focal
change in potential in the hand that would follow peripheral nerve stimulation
You can explain the change in potential across the hand that follows peripheral nerve stimulation because when the peripheral nerves are stimulated it travels to the brain and activates the sympathetic nervous system which then activates the sweat glands and we see the hands sweat.
heart rate variability (breathing)
- quiet breathing: smaller/normal
- deep breathing: greater
RR interval (breathing)
- quiet breathing: smaller/normal
- deep breathing: greater
Valsalva maneuver
- take a deep breath in and then attempt to expire with the glottis closed, the mouth kept shut, and with the nose pinched closed
- used to assess the integrity of the autonomic nerves supplying the heart and blood vessels
purpose of an EMG
records electrical activity of the innervated muscle fibers
ways that an EMG can be measured
- intramuscular: needle electrodes inserted through the skin into the muscle
- surface: electrodes placed on the skin surface
coactivation among antagonistic muscle groups
- a phenomenon in which contraction of a muscle leads to minor activity in the antagonistic muscle
- helps to stabilize the joint during isotonic contractions
- consider the example of an isotonic contraction such as lifting a weight with your arm. The biceps muscle contracts to lift the weight, and the triceps also contract to help control this lifting movement
concentric contractions
the contraction of the biceps provides an example of concentric contraction; the muscle is shortening as the contraction proceeds
eccentric contractions
the controlled contraction of the triceps provides an example of eccentric contraction; here the muscle is lengthening even though it is contracting
conditions that may lead to muscle fatigue
- depletion of ATP stores
- changes in the “sense of effort”
- loss of the “central drive”
- failure of neuromuscular propagation
- reduction in Ca2+ release in excitation-contraction coupling
- metabolic changes in the muscle cell (such as build up of lactic acid which can make the skeletal muscle acidic, inhibiting any further anaerobic glycolysis)
- reduction in muscle blood flow owing to compression of blood vessels
three ways that ATP can be produced
aerobic glycolysis, anaerobic glycolysis, phosphocreatine
aerobic glycolysis
when enough O2 is present, pyruvate (from the breakdown of fats, glycogen, or glucose) can enter the citric acid cycle and is broken down to CO2 and H2O. This process generates large amounts of ATP.
anaerobic glycolysis
if O2 supplies are insufficient, pyruvate cannot enter the citric acid cycle and instead is converted to lactic acid. This makes a small amount of ATP, but does not require O2.
phosphocreatine
in resting muscle, some ATP transfers a phosphate to creatine, creating a store of phosphocreatine. During intense exercise, phosphocreatine can be used to resynthesize ATP, and allows contraction to continue.
common diseases impacting skeletal muscle activity
- peripheral neuropathy
- NMJ diseases: LEMS, MG, botulism
- myopathies
EMG waveform is irregular
the EMG records the electrical activity of the muscle fibers whose motor units fire asynchronously whereas the the ECG records the hearts electrical activity that is produced synchronously
outcome of the EMG
As we added more books to the volunteer’s arm, the trace of amplitude (mV) began to increase for both the biceps and the triceps. We can infer based on our data that the biceps and triceps are working together in coactivation, to be able to withstand the increase weight for each trial.
outcome of the grip force
grip force increased with the amount of force applied
outcome of the muscle fatigue
grip force decreased as time continued
outcome of the force with encouragement
encouragement didn’t help as much as a brief period of rest did
outcome of the visual feedback experiments
visual feedback didn’t help, it was about the same grip force whether there was visual feedback or not
anatomy of skeletal muscle on the cellular level
muscle (organ) -> fascicle -> muscle fiber (cell) -> microfibril (largest to smallest)
neuromuscular junction
- action potentials arriving at the axon terminal trigger the release of acetylcholine into the synaptic cleft of the neuromuscular junction.
- the acetylcholine diffuses through the junctional cleft and binds to the nicotinic acetylcholine receptors on the motor end plate.
- the bound receptors open cation-selective ion channels, which depolarizes the muscle end plate and leads to the release of calcium from the sarcoplasmic reticulum.
- the increased cytosolic calcium sets in motion the biochemical events that underlie contraction.
- acetylcholine is rapidly hydrolyzed by acetylcholinesterase, which terminates the muscle contraction signals.
function of antibodies
a protein that specifically binds to an antigen and helps to neutralize foreign substances or prepare them for destruction by phagocytes
role antigens play in antibody production
antigens attack pathogens and create new antibodies
equation for cardiac output
CO = HR (beats/min, BPM) x SV (liters/beat)
stroke volume and cardiac output: athlete
- stroke volume: at rest is appreciably higher in very fit individuals
- cardiac output: in a fit athlete: CO before exercise = 5 L; HR = 40 BPM; SV = 0.125 L, higher in athletes
stroke volume and cardiac output: couch potato
- stroke volume: lower than athletes
- cardiac output: lower than athletes
electrical activity of the heart is impacted by exercise
- an increase in heart rate corresponds to a shortening of the cardiac cycle (RR interval decreases)
- most of this shortening occurs in the TP interval
- the QT interval also shortens, but only slightly
distribution of blood changes when a person is exercising
- smooth muscle relaxes to permit more blood to enter the particular capillary beds, if the cells in that organ require more arterial blood.
- this need can be due to a decrease in pH, oxygen levels, or an increase in carbon dioxide levels.
- the blood flow to the gut and kidneys accounts for about 50% of the resting blood flow.
- during exercise, this decreases significantly while the blood flow to the exercising skeletal muscles increases
factors that influence the increase in heart rate during exercise
- the mammalian nervous system controls heart rate via the autonomic nerves.
- stimulation of sympathetic nerves increases the rate and stimulation of the parasympathetic (vagal) nerve.
- at rest, the vagal effect predominates this is called vagal tone.
- however, during exercise vagal activity decreases and sympathetic activity increases. this combines with increased levels of circulating epinephrine, to result in increased heart rate.
how the heart rate and pulse amplitude changed both immediately after exercise and during recovery, physiological advantages of these observed changes
Immediately after exercise the heart rate increased and the pulse decreased, but during recovery the heart rate decreased and pulse increased. The physiological advantage of these changes is after exercise, during the resting period the blood flow goes to the skin to release heat and cool the body.
outcomes of the hand exercise activity and be able to describe what happened to the pulse amplitude and why this change occurred
- the pulse rate increased with more rest
- immediately after hand exercise, the amplitude was smaller than in the resting record
how blood pressure can be measured: directly
directly measure venous blood pressure in patients in intensive care- this is achieved with an apparatus; a plastic tube filled with saline connected to the vein
how blood pressure can be measured: indirectly
the auscultatory method: a stethoscope is used to listen to the heart sounds, and a blood pressure cuff is connected to a mercury sphygmomanometer so that cuff pressure can be measured
normal blood pressure levels
120/80 mmHg
high blood pressure levels
140/90 mmHg
low blood pressure levels
100/60 mmHg
relationship between blood pressure and blood flow
- each heartbeat ejects enough blood at a sufficient pressure to ensure that blood flow to the tissues is fast enough to provide the oxygen and nutrients required by cells
- waste products of metabolism must also be removed constantly so that they do not accumulate in body tissues
- the amount of blood flowing is proportional to the blood pressure that drives the flow.
- that is, if the width of a tube remains the same, the greater the pressure, the greater the flow
- narrower tubes provide more resistance to flow
- the blood flows through the arteries, arterioles, capillaries, and then back to the heart through the venules and veins
- these vessels provide resistance to the flow
- the greatest increase in resistance, and therefore the greatest decrease in blood pressure, occurs in the arterioles. therefore, the arterioles make the greatest contribution to the vascular peripheral resistance
systolic pressure
- the peak pressure reached during the cardiac cycle
- systolic = ventricle contraction
diastolic pressure
- when the arterial blood pressure is at its lowest, immediately before the contracting ventricle pushes blood into the arteries again
- diastolic = ventricle relaxation
regulation of arterial blood pressure
- arterial blood pressure is monitored by pressure receptors in the aortic arch and the first part of the internal carotid artery: the carotid sinus
- these baroreceptors monitor the degree of stretch of the arterial wall
- for example, acute blood loss will decrease arterial blood pressure. this is detected by the baroreceptors which activate the cardiovascular control centers in the brain. in turn, these stimulate the autonomic nerves to vasoconstrict the peripheral blood vessels, and increase the heart rate and force of contraction. the vasoconstriction increases peripheral resistance, and the increased rate and force of cardiac contraction increases cardiac output; so blood flow to the brain and other vital organs is maintained.
baroreceptors monitor the pressure of blood flowing through the _____, and the carotid sinus receptors monitor the pressure of the blood flowing to the ____
systemic arterial system; brain
acute increase in blood volume
- will cause peripheral vasodilation and a decreased heart rate
- to understand the regulation of blood pressure you can think about what happens when you take a hot bath. pale skin turns red as peripheral blood vessels dilate to encourage heat loss. this reduces peripheral resistance, and blood pressure starts to go down. you might notice this if you stand up to get out of the bath, and begin to feel dizzy. the baroreceptors quickly detect the falling blood pressure, and increase stimulation of heart rate and force of contraction. this is felt as pounding in the chest.
how body position impacts blood pressure
- convention is to reference all arterial blood pressure measurements to the position of the heart.
- if we measure the pressure in an artery that is below this level, then the pressure will be increased
- this is because of the effect of gravity on the column of blood in the vessels, which contributes to hydrostatic pressure
- this effect is quite large
- for example, if we measure the blood pressure in a femoral artery in the thigh with the person lying down, the artery is at the same level as the heart, so there is no extra pressure contributed by gravity. but if we measure this with the person sitting or standing up, then the height of the column of blood below the heart contributes around an additional 50 mmHg to the pressure. that is, if the person has a blood pressure measured at heart level of 120/80 mmHg, then the pressure in the femoral artery in the thigh will be 170/130 mmHg
- similarly, if we were to measure the blood pressure in the arm when the arm was raised above the head, it would be appreciably lower than it is at heart level
- it is essential to realize that this hydrostatic pressure affects all fluids at the same level. therefore, the interstitial fluid pressure, and the pressures of the blood in the capillaries and veins are all increased to the same extent. thus, the pressure difference between interstitial fluid and adjacent capillaries is exactly the same whether a person is standing or lying down
- the effect of gravity on pressure also affects veins
- because the veins are distensible, the increased pressure tends to cause blood to pool in the veins, thereby decreasing the return of the blood to the heart (venous return)
- this is counteracted by valves in the veins, which prevent blood backflow when standing or sitting
- in addition, skeletal muscle contraction presses on the veins and helps to increase venous pressure in legs to push blood back towards the heart
- this works well as long as we walk about, but not when we sit still
- for example, sitting still for hours in airplane seats can result in slowing of blood flow and this contributes to deep vein thrombosis
- in the head and brain, gravity has the opposite effect to veins as the head and brain are above the heart when standing
- since perfusion of the brain with blood is essential to life, it is not surprising that the pressure of the blood flowing to the brain is monitored separately (via the carotid sinus baroreceptors) from that of the blood going to the rest of the body
- remember that blood pressure is constantly measured and regulated, so lying down should lead to greater pressure being detected in the carotid baroreceptors with consequent slowing of heart rate
- position therefore affects not only the measurement of BP but also its regulation
hypertension
- hypertension refers to a chronic condition characterized by a resting blood pressure of 140/90 mmHg or greater
- although, many people have an occasional blood pressure reading greater than 140/90 mmHg; they are not necessarily hypertensive
- factors: age, an underlying cause to another illness, increased production of corticoids, increased epinephrine (adrenaline) production, chronic renal diseases
importance of Korotkoff sounds
Korotkoffs sounds identify systolic and diastolic blood pressure and allows physicians to check patient blood pressures and provide appropriate medical treatments
expected outcomes of the blood pressure lab activities and be able to describe these results regarding the relationship between the heart sounds and finger pulse
- blood pressure is lower when arm is above head than when arm is at heart level because the blood is fighting gravity to make it all the way up the arm
- the faster the blood pressure cuff is deflated the faster blood flow is when the artery opens back up
- the diastolic pressure cannot be determined by a finger pulse transducer (the pulse won’t disappear when the cuff pressure drops below diastolic pressure)
- when the pressure exerted by the cuff is greater than systolic pressure the brachial artery is completely collapsed, thus there is no blood flow and no finger pulse is detected. When the cuff pressure drops below systolicpressure the brachial artery partially opens, blood flow is returned and a finger pulse is detected
atrioventricular valves
- between the atrium and ventricle prevent backflow from ventricle to atrium
- the lower-pitched “lub” sound is produced by the closure of the AV (mitral and tricuspid) valves
semilunar valves
- between ventricle and artery prevent backflow of blood from the aorta and main pulmonary artery into the respective ventricle
- when the ventricles relax the blood pressure drops below that in the artery, and the semilunar valves (aortic and pulmonary) close producing the higher-pitched “dub” sound
a murmur
- an additional or unusual sound heard during a heartbeat
- malfunctions of the heart valves can often produce an audible murmur
cardiac cycle
- during ventricular diastole blood is returning to the heart
- deoxygenated blood from the periphery enters the right atrium, and flows into the right ventricle through the open AV valve
- oxygenated blood from the lungs enters the left atrium, and flows into the left ventricle through the open AV valve
- filling of the ventricles is completed when the atria contract (atrial systole)
- in the resting state, atrial systole accounts for some 20% of ventricular filling
- atrial contraction is followed by contraction of the ventricles (ventricular systole). Initially, as the ventricles begin to contract the pressure in them rises and exceeds that in the atria to close the AV valves
- the volume of the ventricles cannot change until the pressure in the left ventricle exceeds that in the aorta and in the right ventricle exceeds that in the main pulmonary artery (this is the isovolumic phase of ventricular contraction)
- when the pressure in the left ventricle finally exceeds that in the aorta (and the pressure in the right ventricle exceeds that in the main pulmonary artery) the semilunar valves open, and blood is ejected into the aorta and main pulmonary artery
- as the ventricular muscle relaxes, pressures in the ventricles fall below those in the aorta and main pulmonary artery, and the semilunar valves close
- ventricular pressure continues to fall and when it has fallen below that in the atria, the AV valves open and ventricular filling begins again
physiological components represented by each ECG component in the cardiac cycle
P wave, QRS complex, T wave
P wave
- atrial depolarization
- atrial contraction (systole)
QRS complex
- ventricular depolarization
- ventricular contraction (systole)
T wave
- ventricular repolarization
- ventricular relaxation (diastole)
where the heart sounds occur in the cardiac cycle
- first heart sound occurs at S
- second heart sound occurs at T
the electrical activity of the heart
- cardiac contractions are not dependent upon a nerve supply. however, innervation by the parasympathetic (vagus) and sympathetic nerves does modify the basic cardiac rhythm. the best known example of this is so-called sinus arrhythmia where respiratory activity affects the heart rate
- the cardiac cycle involves a sequential contraction of the atria and the ventricles
- the combined electrical activity of the different myocardial cells produces electrical currents that spread through the body fluids. these currents are large enough to be detected by recording electrodes placed on the skin. a recording of this electrical activity is an electrocardiogram (ECG)
- the action potentials recorded from atrial and ventricular fibers are different from those recorded from nerves and skeletal muscle
different types of valvular heart disease
mitral stenosis, mitral insufficiency, aortic stenosis, aortic insufficiency
mitral stenosis
a narrowing of the orifice of the mitral valve. Blood flows from left atrium to left ventricle through this valve during ventricular diastole. With mitral stenosis, a low pitched, middiastolic murmur is heard. There is often a louder than normal first sound as the mitral valve is shut more forcefully than normal.
mitral insufficiency
damage to the valve structure leads to a leak of blood back from the contracting ventricle to the left atrium. This leak results in a high-pitched murmur heard throughout systole. Because of the greater blood volume in the left atrium, there is a very rapid filling of the left ventricle when the mitral valve opens in early diastole. This gives rise to a third heart sound.
aortic stenosis
a narrowed aortic valve impedes blood flow into the aorta during ventricular systole. This results in a characteristic systolic murmur that increases in loudness to midsystole and then fades gradually. The second heart sound may be softer than normal too.
aortic insufficiency
the defective valve does not close properly so that, during early diastole, blood flows back into the ventricle. This results in an early diastolic murmur that follows the second heart sound and gradually decreases in intensity.
Wiggers diagram
it allows you to see the temporal relationships between the different parameters
observations regarding the relationship between the heart sounds and finger pulse
after the the first sound is heard the finger pulse begins to rise and as the finger pulse reaches it peak the second heart sound is heard
