MCDB 1B Study Guide - Midterm Guide: Skeletal Muscle, Sodium Chloride, Descending Limb Of Loop Of Henle
10 May 2018
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I. NUTRITION/TRANSPORT 1: CIRCULATORY SYSTEMS
➢ Having double circulation (two separate circuits) allows for a higher blood pressure in the
systemic circuit.
➢ Having more heart chambers allows for increased separation of deoxygenated and
oxygenated blood flow.
➢ Diastole means relaxation and systole means contraction; atria contract before ventricles
ut etiula otatio poides the ajo pup.
➢ Cardiac cells are connected by intercalated disks: this allows them to coordinate
contractions within chambers.
➢ SA Node has pacemaker activity and does not need a stimulus to create an action
potential.
• Pacemakers have an unstable resting potential which will gradually drift to threshold
before voltage-gated Ca2+ channels open and cause the cell to spontaneously
depolarize. Then, K+ channels are opened and K+ flows out and repolarizes the cell.
• Paeake ells do’t otat! The ol eate atio potetials.
• Muscle contraction ends when Ca2+ is taken up by the sarcoplasmic reticulum.
➢ AV Node delays the start of ventricular contraction by 0.1 seconds so the atria can fully
contract first!
➢ Action potentials in the heart are slower (400-600ms as opposed to 2-3 milliseconds in
neurons) and involve different ion channels.
➢ Gap junctions within the intercalated disks connect cells within heart chambers in order to
coordinate cardiac muscle contraction. There are no gap junctions connecting chambers –
only nodes.
• Ions can flow quickly through gap junctions; this electrical continuity allows action
potentials to spread rapidly.
• Macrophages increase electrical continuity in the AV node by adding extra gap
junctions.
➢ ECGs record the electrical activity of the heart by placing electrodes on the skin.
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➢ The nervous system controls heart rate in two ways:
• Sympathetic nerves release (nor)epinephrine to increase the heart rate by
increasing the permeability of Na+ and Ca2+ channels, making the action potentials
quicker and more frequent.
• Parasympathetic nerves release acetylcholine to decrease pacemaker activity and
slow the heart rate by increasing the permeability of K+ channels and decreasing the
permeability of Ca2+ channels. This makes the resting potential rise slower and thus
the action potentials are farther apart.
➢ There are 5 types of vessels: arteries, arterioles, capillaries, venules and veins.
➢ Arteries carry oxygenated blood away from the heart.
• They are narrower than veins because their walls are thicker – this helps them
withstand pressure as blood leaves the heart.
• The’e suouded thik laes of smooth muscle to allow them to contract and
expand, altering their resistance and therefore blood flow. They also contain elastic
fibers which allow them to withstand high pressures (same as arterioles).
• Atherosclerosis is the loggig of the ateies plaue uildup. This a ause a
thrombus (blood clot) to form which obstructs the arteries. To combat this, insert a
stent into the artery and use a balloon to enlarge it (and the artery), then remove it.
➢ Arterioles control the distribution of blood to specific capillary beds.
• The’e suouded thik laes of sooth usle to allo the to otat ad
expand, altering their resistance and therefore blood flow. They also contain elastic
fibers which allow them to withstand high pressures (same as arteries).
• Precapillary sphincters (small bits of smooth muscle) alter the diameter of the
arterioles and thus change their resistance to blood flow. This is subject to both local
and systemic control.
➢ Capillaries are the site of exchange between the blood and interstitial fluid. Open systems
do’t hae apillaies.
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Document Summary
Having double circulation (two separate circuits) allows for a higher blood pressure in the systemic circuit. Having more heart chambers allows for increased separation of deoxygenated and oxygenated blood flow. Diastole means relaxation and systole means contraction; atria contract before ventricles (cid:271)ut (cid:448)e(cid:374)t(cid:396)i(cid:272)ula(cid:396) (cid:272)o(cid:374)t(cid:396)a(cid:272)tio(cid:374) p(cid:396)o(cid:448)ides the (cid:862)(cid:373)ajo(cid:396) pu(cid:373)p(cid:863). Cardiac cells are connected by intercalated disks: this allows them to coordinate contractions within chambers. Then, k+ channels are opened and k+ flows out and repolarizes the cell: pa(cid:272)e(cid:373)ake(cid:396) (cid:272)ells do(cid:374)"t (cid:272)o(cid:374)t(cid:396)a(cid:272)t! The(cid:455) o(cid:374)l(cid:455) (cid:272)(cid:396)eate a(cid:272)tio(cid:374) pote(cid:374)tials: muscle contraction ends when ca2+ is taken up by the sarcoplasmic reticulum. Av node delays the start of ventricular contraction by 0. 1 seconds so the atria can fully contract first! Action potentials in the heart are slower (400-600ms as opposed to 2-3 milliseconds in neurons) and involve different ion channels. Gap junctions within the intercalated disks connect cells within heart chambers in order to coordinate cardiac muscle contraction.
