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
