Lab 5: Endocrine System and Cardiac Conduction

Endocrine organs

Glands that produce hormones as messengers.

Hormones

act as chemical messengers regulating physiological processes.

Trophic effect

Hormones regulating other endocrine glands.

Hyperinsulinism

Excess insulin affecting glucose levels. As glucose was used up by the body, the brain was also deprived of glucose.

Lutenizing hormone (LH)

Hormone inducing ovulation in female frogs, found in the anterior pituitary gland

Acetylcholine (Ach)

Neurotransmitter affecting heart rate and contractions (___ causes a decrease in heart rate in parasympathetic)

Epinephrine (EP)

A hormone that increases heart rate and contraction strength. It's a neurotransmitter that mimics the effect of the sympathetic nervous system on the pacemaker.

Cardiac conduction system

Network controlling heart's electrical signals.

SA node

Primary pacemaker initiating heart rhythm.

AV node

Gateway for electrical signals to ventricles.

Bundle of His

Pathway for signals from AV node.

Purkinje fibers

Conducting fibers spreading signals in ventricles.

Myogenic

Heartbeat originating within the heart muscle.

Autorhythmic

Ability to generate spontaneous depolarization.

ECG (Electrocardiogram)

Recording of electrical activity of the heart.

P wave

Atrial depolarization and contraction phase.

QRS complex

AV Node fires, Ventricular depolarization and ventricular systole (contraction phase)

T wave

Ventricular repolarization phase.

Systole

Phase of heart contraction.

Diastole

Phase of heart relaxation.

Extrasystole

Extra heartbeat disrupting normal rhythm.

Arrhythmia

Irregular heart rhythm due to conduction failure of AV node

Frog heart

Three-chambered heart used in experiments.

Human heart

Four-chambered heart with separate blood flow.

Ventricular systole

Contraction phase of ventricles.

Atrial systole

Contraction phase of atria.

Asystole

Flatline indicating no heart activity.

Oscilloscope

Device measuring heart signal changes.

Chemical modifiers

Substances affecting heart rate and contractions.

Baseline signal

Initial measurement for comparison during experiments.

Nodal rhythm

no SA node activity (no P waves, meaning no atrial systole)

Conduction system pathway

SA node (pacemaker) , AV node, AV Bundle (buldne of his), Right &v Left Bundle Branches, Subendocardial conduction network (purkinje fibers)

Atropine

Blocks the effect of acetycholine released by the parasympathetic neurons

Pilocarpine

Stimulates the parasympathetic nervous system by stimulating ACH by the vagnus nerve into the hearts pacemaker to slow and control the rate of heart contractions

Digitalis

A drug commonly prescribed for heart patients with CHF (congestive heart failure) to decrease heart rate and increase force

Potassium

In hyperkalemia in a resting neuron (and muscle fiber), the K ion concentration is higher inside the cell than outside (Na is higher outside). Increasing the extracelluar K concentration makes the outside of the membrane even more positive, and the membrane becomes hyperpolarized. Heart rate may beat erractically, producing arrthmias, and stop beating

Sodium

Hypernatremia caused fluid retention (edma) and rasies BP (hypertension). Can lead to arrhythmia and congestive heart failure from edma.

Calcium

Hypercalcemia reduces Na+ permeability of plasma membrane and inhibits (stops) polarization of nerve and muscle causing muscle weakness, arrhythmia, and depressed nerve function. Decrease in heart rate