PHYSIO MIDDY 2

Function of CV: Transport + Regulate..?

Diastole:

ventricles relaxed

Systole:

Ventricles contract

Dicrotic Notch

the small dip in arterial pressure tracing following the closure of the aortic valve, marking the end of systole.

Cardiac myocyte muscle properties:

Unnucleated —> smaller than skeletal muscles but still striated

Autorhythmic cells

specialized cardiac cells that spontaneously generate and conduct electrical impulses to set the rhythm of the heart without needing nervous system stimulation

Contractile cells

perform the mechanical contraction that pumps blood through the body.

intercalated disk

joins adjacent cardiac muscle cells (both autorhythmic and contractile) together, where you can contract the muscle that also have gap junctions that allow ion movement in the cells

Flow of charge in Heart cells

When the pacemaker cells create action potentials—> intercalated disk’s gap junctions allow the cells to receive them at once

why pleatau in action potential present in heart

The plateau phase in the cardiac action potential is present to prevent the heart muscle from locking up (tetanus) and to give the chambers time to fill with blood.

Use of Ca in heart action potential

Calcium ions slowly rush into the cell through special channels to keep the signal on to sustain the strength of contraction and slows down refractory period

L-type calcium channel

Long lasting calcium channel: open during membrane depolarization, allowing extracellular calcium (Ca²⁺) to flow into cells —> REASON FOR PLATEU

Ca+ spark

Causes massive flood of calcium into the cell, released from the sarcoplasmic reticulum

sarcoplasmic reticulum (SR)

Contraction: stores Ca+ in muscle cells —> ca+ triggers ryanodine receptors (RyRs) —→ makes SR release Ca+ into muscle cell

Relaxation: active transport pumps —> SERCA

Sarcoplasmic/Endoplasmic Reticulum Calcium ATPase

SERCA - forcefully pump Ca²⁺ back inside the SR against its concentration gradient.

Purkinje fibers

rapidly conduct electrical impulses to ensure a synchronized contraction of the ventricles

Chain of command …→

note: purkinje fibers can carry contraction but its not very powerful but too slow + contractions not coordinated

Vagus nerve is part of the ____ system and acts on the ___ and ___ and comes from the?

Parasympathetic, SA and AV nodes and comes from the medulla

The _______ cardiac nerve acts on the ___ , ___ and ____

Sympathetic, acts on the SA, AV and ventricular muscle cells

Autonomic control: Describe parasympathetic + Sympathetic stimulation

Parasympathetic: hyperpolarized and has a slower depolarization —> slow down heart (increase in K permeably causes hyper polarization) decrease Ca permeability slows rate of depolarization

Sympathetic: depolarize quicker If channels open earlier and stay open longer (increase in Na permeability) and increase in Ca = increase in depolarization

Frank starling mechanism

intrinsic ability of the heart to increase its force of contraction and stroke volume as the volume of blood filling the heart (end-diastolic volume or preload) increases, without needing external nervous or hormonal control