• heart can beat rhythmically with coordinated contraction without any neural input

• heart is a functional syncytium

• contractile cells- working myocardium
• conductile (2 cell types)
  • pacemaker cells that fire spontaneously and repetitively
  • cells in the specialized conduction pathway

• steady sodium and calcium influx through I_f channel
• do not have K1 channels that would act to hyperpolarize and inhibit the cell
  • found in ventricular cells

• I(f) channel- slow steady depolarization by allowing sodium, calcium into cell
• voltage gated calcium channel- depol. leads to open rapidly, so beginning of AP
• voltage gated potassium channel- depol. leads to opening slowly, leading to repolarization of cell

• resting membrane potential more negative
• it will not spontaneously depolarize

• voltage gated sodium channel
  • opens very rapidly during depolarization and closes very rapidly during depolarization
• voltage gated calcium channel- depol. cause rapidly opening
• voltage gated potassium channel- depol. cause slow opening
• K1 channel- depolarization closes these channels

1. Phase 4- K1 channel open during resting
2. Phase 0- when cell gets "invaded" by neighbors that reaches threshold, voltage gated sodium channels open rapidly (upstroke)
   • open more rapidly due to more negative resting membrane potential
3. Phase 1- closure of voltage gated sodium channels and opening of voltage gated calcium channel
4. Phase 2- plateau due to maintaing opening of voltage gated calcium channels
5. Phase 3- voltage gated potassium channel opens and calcium channels close, leading to repolarization

• ST interval between vent. depol. and repol.
• atrial depolarization as well

• calcium binds to tropomyosin
• allow crossbinding between actin and myosin heads, generating force for contraction

Strength of contraction proportional to intracellular calcium during AP in addition to initial length (preload volume)

• greater calcium through cell membrane cause increase calcium from SR

• Na/Ca- it allows us to move calcium out of the cell so we can have relaxation of muscle
  • one calcium out and three sodiums in
• Na/K- allows us to keep EC Na high and IC K high
  • clinical app.- digitalis will decrease potassium in cell and increase sodium conc. in cell
    • this will inhibit Na/Ca exchanger, leading to increase calcium in cell, so stronger contraction

• measure of strength of cadiac contraction at any given cardiac muscle length
  • ability of heart to generate pressure without change in length
• related to calcium fluxes and conentrations before and during a contraction

• increase influx of calcium
• more calcium pumped into SR
• more calcium released from SR during each beat, leading to increased strength of contraction and is an example of increase contractility

• in the ascending part of the curve
  • if you increase the volume, you increase the strength of contraction
  • this relationship is continuous in a "passive curve"
• when you reach the top part of the curve, further increases in volume do not affect ability of heart to increase contraction strength
• when you go to descending part of curve, further increase in volumes decrease strength of contraction

• they are on the descending part of the curve
• they heart has hypertrophied, and its preload has increased to a point continued increases in preload cause decrease in the strength of contraction

• increase preload will increase stroke volume

1. diastole- when atrial pressure exceeds vent. pressure, AV valves open
2. atrial contraction- forces the rest of blood into ventricle
3. isovol. contraction- when vent. exceeds atrial pressure, AV valves close (first heart sound)
   • build up of pressure at constant volume
4. rapid ventricular ejection- when vent. pressure exceeds aortic P, aortic valve opens
5. isovolemic relaxation- when aortic P exceeds ventricular P, aortic valve close (second heart sound)
   • drop in pressure at constant volume

thoracic

lumbar

• sacral
• cranial
  • midbrain- to eyes, salivary glands
  • medulla- to heart, lungs, stomach, intestines

• pregang. fibers go long distance almost to the target organ
• postgang. fibers go short distance

• short preganglionic fibers that synapse at paravertebral ganglia
• long postganglionic fibers

However, adrenal medulla is innervated directly by preganglionic fibers

• pregang. release ACh to act on nicotinic R on postgang. R
• post gang. release predominantly norepi to act predominantly on alpha and beta receptors on effector organ

• pregang. release ACh to act on nicotinic R on postgang. R
• postgang. release ACh to act on muscarinc reeceptors on effector organs

• stimulation of muscarinic R opens a different potassium channel, leading to hyperpolarization
  • starts at a more negative resting membrane potential, leading to less AP's in same amount of time
• shift the pacemaker potential curve to right

• stimulating beta receptor cause phosphorylation of voltage calcium channel
  • reach threshold at more negative potential, leading to more AP's in a shorter amount of time
• increase influx through If channel

• increase calcium influx, leading to increase calcium release from SR evoke increase in contractility

• cholinergic- decrease HR
• adrenergic- increase HR, contractility (beta 1)

• cholinergics- NONE
• adrenergic
  • constriction via symp. nerves (alpha one)
  • dilation via circulating epinepherine activating beta 2 in skel. muscle arterioles

• cholinergics- NONE
• adrenergic
  • renin release (beta 1)

• cholinergics- contraction
• adrenergics- relaxation (beta 2)

• cholinergic
  • increase tone and motility
  • stimulate secretion
  • relax sphincters
• adrenergic
  • decrease tone and motility (alpha)
  • inhibit secretion
  • contract sphincters (alpha)

• cholinergics- NONE
• adrenergics- lipolysis (beta 3)

• cholinergics- NONE
• adrenergics- glycogenolysis (beta 2)

• cholinergics- contraction for near vision
• adrenergics- relax for far vision (beta 2)

• cholinergics- vaginal engorgement, penile erection
• adrenergics- ejaculation/orgasm (alpha)

• cholinergics- secretion (Ach BUT SYMP.)
• adrenergics- NONE