P-wave=atrial depolarization

QRS complex=ventricular depolarization

T-wave=ventricular repolarization

Systole=contraction

Diastole=relaxation

heart never relaxes, there's always muscle tone

Parasympathetic Effects

mediated by ACh

Sympathetic Effects

mediated by NE released from postganlionic sympathetic nerve endings escapes into circulation.

Both Para & Sympa Nervous System have

Nicotinic Ach Receptor at preganglionic fiber

Para has muscarinic ACh receptors at target tissue

Sympathetic Nervous System

has

NE receptor a&b at Heart tissue.

Muscarinic Ach receptor at sweat gland

 Directly innervates adrenal medulla on Nicotinic Ach Receptor

Depolarization: interior voltage rise, more +

Nicotinic Ach receptors are ligand-gated ion channel, once activated by Ach, influx on Na⁺ and Ca⁺

Depolarize the cells.

Hyperpolarization: interior voltage - outflux of K⁺

Muscarinic Ach Receptor are GPCRs, once activated by ACh, K⁺ open, K⁺efflux, hyperpolarize the cell.

Parasympathetic Effect on Heart

Ach→muscarinic→G_i →decrease second messenger cAMP,→ open K channel→ Hyperpolarization

Sympathetic Effect on Heart

NE→beta₁ →increase second messenger cAMP→ depolarizationheart more excitable

Homeostatic Regulation of HR

Baroreceptor in carotid sinus and aorta send info to medulla oblongata which regulate the activation of Symppathetic and Parasympathetic NS.

It's a short-term control

Reserpine

first hypertensive drugs

used in emergency sitution

interferes with packaging of NE into vesicles. inhibit its release and excitatory action

4 ways of controlling BP

Regulate R of arterioles (a-receptors)

Capacitance of venules

Pump output

Kidneys release renin→angiotensin, Aldosteron release from adrenal cortex.