Why is the funny current called funny?

Funny current (or funny channel, or If) refers to a specific current in the heart. It is called “funny” because it has effects opposite to those of most other heart currents. Funny currents have been associated with cyclic-nucleotide-gated channels.

What is the funny current in the heart?

The pacemaker current (or If, or IKf, also referred to as the funny current) is an electric current in the heart that flows through the HCN channel or pacemaker channel. Such channels are important parts of the electrical conduction system of the heart and form a component of the natural pacemaker.

Does Funny current increase heart rate?

Ivabradine slows heart rate by reducing the I(f) current-regulated steepness of the diastolic depolarisation in SAN myocytes, thereby increasing diastolic duration, without altering action potential duration or causing negative inotropy.

Why are HCN channels called Funny channels?

HCN channels are encoded by four genes (HCN1, 2, 3, 4) and are widely expressed throughout the heart and the central nervous system. The current through HCN channels, designated If or Ih, plays a key role in the control of cardiac and neuronal rhythmicity and is called the pacemaker current or “funny” current.

Are Funny channels ligand gated?

For example, when an action potential is elicited in a cardiomyocyte, sodium channels transiently open and potassium channels close, which leads to depolarization….Ion Channels.

CHANNEL	CHARACTERISTICS
Slow Na+	“Funny” pacemaker current (If) in cardiac nodal tissue
Potassium Channels

What does the SA node stimulate?

SA node: The SA node (SA stands for sinoatrial) is one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood.

Do contractile cells have funny channels?

Contractile cells make up 99\% of cardiomyocytes, therefore are found throughout the heart. As a result of hyperpolarisation, voltage-gated sodium channels called funny channels open and Na+ enters the cell. There is closure of potassium channels, preventing them leaving.

What do HCN channels do?

HCN channels have a major role in controlling neuronal excitability, dendritic integration of synaptic potentials, synaptic transmission, and rhythmic oscillatory activity in individual neurons and neuronal networks.

What is HCN channel blockers?

In isolated sinoatrial node cells, ivabradine blocks HCN pacemaker currents in the low micromolar range with minimal or no off-target effects. Channel block is accomplished from the cytoplasmic side with a strong preference for the open channel state resulting in use-dependence characteristics.

Is diastole depolarized?

The voltage region encompassed by this transition is commonly known as pacemaker phase, or slow diastolic depolarization or phase 4. The duration of this slow diastolic depolarization (pacemaker phase) thus governs the cardiac chronotropism.

Are Funny channels voltage-gated?

The channels belong to the voltage-gated K+ channel superfamily, and like other members of this family are tetramers, with each transmembrane subunit containing a voltage sensor domain coupled to a pore domain (Fig. Two of four subunits shown for clarity.

What causes heartbeat?

Your heartbeat is triggered by electrical impulses that travel down a special pathway through your heart: SA node (sinoatrial node) – known as the heart’s natural pacemaker. The impulse starts in a small bundle of specialized cells located in the right atrium, called the SA node.

What is funfunny current?

Funny current or pacemaker current is seen mostly in the SA (sinoatrial node) and has been designated as I f . Diastolic or phase 4 depolarization is the hallmark of pacemaker cells of the heart.

What is the function of the funny current in the heart?

Since the funny current controls the rate of the sinus node activity, it determines the heart rate. I f increases on perfusion with adrenaline and thereby the slope of diastolic depolarization and the heart rate [1].

What is the funny current or pacemaker current?

Abstract: The funny current or pacemaker current is predominantly a feature of the sinoatrial node. Funny current or pacemaker current is seen mostly in the SA (sinoatrial node) and has been designated as I f . Diastolic or phase 4 depolarization is the hallmark of pacemaker cells of the heart.

What is the function of the inward F (funny) current?

The inward f (funny) current is a mixed sodium / potassium current which initiates the spontaneous depolarization of the sinus node, and hence controls the heart rate. Discovery of this channel lead to the development of Ivabradine, a useful drug in heart failure. , Paed. Cardiologist, Boston Children’s Hospital, 10+ Yrs Exp. Thanks for the A2A.