quiz 8 Flashcards
significance of maintaining bodily pH
- tons of bodily reactions driven by enzymes with specific optimal pH ranges
- pH varies in different areas of the body (even in different cell organelles) but all enzymes have narrow optimal pH
- overall body pH is 7.4, drop to even 6.8 would be huge
how does pH play a role in perms?
strong pH denatures proteins in hair
what receptors signal a change in breathing rate in the body?
- peripheral chemoreceptors (carotid bodies)
- central chemoreceptors (medulla in brain)
- stretch receptors in lungs
- emotions
differences between peripheral and central chemoreceptors
- peripheral chemoreceptors are carotid bodies, they sense O2 levels
- central chemoreceptors are located in medulla, they sense CO2 and pH levels
how does the heart contribute to human metabolism?
- heart is a pump; provides propulsion of blood through capillaries for nutrient/waste exchange
- metabolism increase can be sustained by increase in pump function (higher HR or stroke volume)
*higher oxygen demand for organisms requires greater separation of oxygenated/deoxygenated blood and higher blood pressure
two parts of the heart
we consider the heart to have 2 functional pumps for 2 circuits:
- low pressure pulmonary/lung circuit
- high pressure arterial/body circuit
open vs closed circulatory design
open systems: hemolymph (in insects) or other blood not enclosed in vessels, heart is a mixing chamber
closed system: everything enclosed in vessels/tubing, heart is a pump
how do open circulatory systems work in insects?
- dorsal heart tube along back contracts to move/mix blood
- hemolymph let in via small holes called otria
- contracts in both directions, blood squirts out excurrent openings on both ends
neuorogenic vs myogenic hearts
neurogenic hearts
- crustaceans, insects, annelids
- contraction under nervous control; no nerve = no heartbeat
myogenic hearts
- vertebrates, mollusks
- contraction initiated by heart cells
- nervous system can modify rate but isn’t required for beating
what triggers heart contractions in neurogenic hearts?
- regulated by peptide release from nerves
- on imaging, white areas around heart tubes are where peptides are released
different types of heart design
1-chamber (non-vertebrate): insects
2-chamber: fish; low pressure because blood travels far
3-chamber: amphibians; 2 atriums and 1 ventricle
3-chamber septated: reptiles; allows for less mixing within ventricle
4-chamber: birds and mammals; full septum
flow of blood in and out of the heart
pulmonary circuit:
vena cava - right atria - tricuspid valve - right ventricle - semilunar values - pulmonary artery - lungs
arterial circuit:
pulmonary veins - left atria - bicuspid/mitral valve - left ventricle - aorta
*values are key to one-way flow!
how is blood supplied to keep the heart functioning?
- coronary vessels penetrate heart from the surface
- blood supply to heart occurs between contractions
how is coronary blood flow blocked, and how is it fixed?
buildup of plaque in coronary arteries can threaten blood flow to heart
- bypass: blood vessels harvested to transport blood flow around problem area
- cardiac stents: mesh expanded via balloon; mesh pushes out against narrowing vessel
how do gap junctions work?
- each cardiac muscle cell has one connexon (hemichannel) which come together to form a gap junction
- each connexon has 6 subunits
- gap junctions allow passage of ATP, ions, signaling molecules, and electrical signaling for heart beat
how does cardiac contraction work? (electric signaling)
conduction pathway: contraction signal is spread by electrical vectors; cardiac myocytes connected through gap junctions
- myogenic cells in the sinoatrial (SA) node initiate heartbeat–atria contract
- AV node slows signal to allow for ventricular filling (takes time)
- signal goes through bundle of His
- signal goes through right and left bundle fibers
- signal reaches Purkinje fibers–ventricles contract
timing/sequence of cardiac contraction
systole: cardiac contraction (artia, then ventricle)
diastole: cardiac relaxation
p-wave: atrial contraction
qrs complex: ventrical contraction
t-wave: ventricular recovery
solutions for problems with cardiac signaling
if SA node is not functioning well to initiate heartbeat, electrodes can be placed in various places to stimulate heart muscle (fix abnormal heart rhythm)
normal heart rate, stroke volume, and cardiac output at rest
heart rate: 60-80 bpm
stroke volume: 50-100 ml
cardiac output: 5 L per minute
how can cardiac output be increased?
- increasing heart rate
- increasing stroke volume (blood pumped for each beat)
how does neural regulation play a role in heart rate?
regulated by the autonomic nervous system in medulla
*will never stop heart or cause HR too high, as there isn’t enough time for filling
- vagus nerve: decreases heart rate/extent of contraction (SV)
- sympathetic cardiac nerves: increase heart rate/extent of contraction (SV)
what factors influence blood pressure?
- flow (cardiac output; HR x SV)
- peripheral resistance (radius/diameter of vessel)
what does blood pressure reflect?
perfusion of tissue by blood
blood pressure equation
P = Q x R
P: pressure
Q: flow
R: resistance
how is blood pressure monitored?
- carotid and aortic baroreceptors monitor blood pressure
- they project to medulla areas associated with autonomic cardiac function (vagus and sympathetic nerves)
what do blood pressure numbers indicate? what are hypertension values?
- first # systolic; 2nd # diastolic
- prehypertension starts above 120/80
complications associated with uncontrolled hypertension
- can contribute to stroke, cardiovascular disease, Atherosclerosis, dementia
difference in blood vessel anatomy between arteries and veins
arteries
- more smooth muscle layer in tunica media
- thicker collagen fibers in tunica externa
- pressure ~100 mmHg
- flow driven by heart contraction
veins
- little smooth muscle in tunica media
- thinner tunica externa; thin vessel
- pressures ~10 mmHg
- valves prevent pooling of blood and keep flow going
how do aneurysms form and why are they dangerous?
- fibers of tunica externa break, causing vessels to thin and web out
- because vessel is thin, it’s at risk of rupturing–hard to plug
- generally leaks before rupturing
how do we utilize our blood for all our bodies’ needs?
- capillaries everywhere but only ~5L blood in our bodies–not enough to maintain maximal flow to organs/tissues
- blood generally redirected from inactive to active tissue via autonomic nervous system
how is blood flow through capillaries regulated?
- metarteriole runs between arteriole and venule
- precapillary sphincters regulate how much flow goes into capillary beds
- local control–high pH/low oxygen in capillary beds in tissues can relax (open) sphincters to allow blood flow into capillaries
types of capillaries
3 types–tightest to leakiest
continuous, fenestrated, discontinuous
2 factors impacting movement in across capillary membrane
- hydrostatic pressure: biggest factor impacting flow, high pressure in vessel causes blood to seep out
- osmotic pressure: solute can move water through a selectively permeable membrane, mainly caused by high levels of albumin in blood vessels (it can’t escape) so water comes in
- materials flow through water in between vessels/interstitial space
starling forces across capillary wall
blood out:
- capillary hydrostatic pressure
- osmotic force due to interstitial fluid protein conc.
blood in:
- interstitial fluid hydrostatic pressure
- osmotic force due to plasma protein conc.
overall changes in pressures through the capillaries
- osmotic pressure stays constant through capillaries
- hydrostatic pressure starts high, then lowers as fluid exits
- vessel hydrostatic pressure dominates at the arterial side (blood flow out)
- vessel osmotic pressure dominates at the venous side (blood flow in)
