What Is Intrinsic Excitability?

Action potentials can occur more frequently as long there is a continued source of stimulation, as long as the relative refractory period has been reached, which in experiment 2 the refractory period was complete.

From molecular perspective, hyperforin has multidirectional mechanisms of action. It acts on ligand-gated (GABA, NMDA and AMPA receptors) (29, 30) and voltage-gated channels (Ca2+, K+, and Na+) (29, 31). In contrast to blockade of ion transport through the plasma membrane, hyperforin can increased an inward Ca2+ current. These processes are dose dependent and probably involved a few different cellular events. In the details, hyperforin in in vitro studies increased the Ca2+ intracellular level by activation of the non-selective canonical transient receptor potential 6 channels (TRPC6) or by the releasing Ca2+ from mitochondria (32–34). As has been previously shown hyperforin activates intracellular

To send a message, a neuron will send a ripple of electrical energy down its axon. This ripple is called "action potential." The way it works is by changing the chemical makeup of the axon's negatively charged interior. Positively charged sodium ions move into the cell and negatively charged potassium ions move out, then the ions move to their original positions. This produces a wave of positively charged

Once a presynaptic neuron is passive, an electrical current is spread along the length of the axon (Schiff, 2012). This is known as action potential (Pinel, 2011). Action potential happens once an abundant amount of depolarisation reaches the limit through the entry of sodium, by means of voltage gated sodium channels

D ) (1) diffused across the synaptic cleft to a receptor protein (2) neurotransmitter released (3) binding of the transmitter opens pores in the ion channels and positive ions move in.

A lesser amount of Potassium ions diffuse out across the membrane, leaving behind a less negative charge. The

As an action potential travels down the axon of the presynaptic neuron, the action potential reaches the axon terminal synaptic vesicles which migrate toward the synapse. They then release neurotransmitters into the synaptic cleft. The neurotransmitters travel through the synaptic cleft and bind to ligand-gated ion channels on the postsynaptic neuron membrane. The channels open and allow chemicals to enter the cell (i.e. sodium). Then positively charged sodium enters the cell and causes the cell to depolarize. The depolarization spreads down the axon and an action potential is generated. The process then starts over at the axon terminals.

___The concentration of extracellular K+ ions would be high and this would prevent more K+ ions from diffusing out of the cell.

In a normal and healthy nervous system, many electrical signals are received and sent through neurons. The arrival of those signals at the end of the neuron triggers the release of many chemicals, in specific, neurotransmitters (Brooker, 2011). These chemicals travel into a gap between the presynaptic (end of one neuron) and the beginning of he postsynaptic (next neuron). This gap is named a synapse (Brooker, 2011). Neurotransmitters are then released into the synapse and then bind to the ibid (post -synaptic neuron). When this

The neurons communicate by sending electrical impulses called the 'nerve impulse' through the axon. The pre-synaptic neuron is activated therefore the neurotransmitters at end of the pre-synaptic neuron release the message into the synapse which activates the receptors on the post-synaptic neuron.

Once in the synapses, the impulses triggers the release of chemical messages called neurotransmitters; which then bind to receptors on the receiving cell as the transmission of the impulse repeated again. The message or impulse continues traveling from one neuron to the next throughout the body until it reaches its destination as it relays a signal. All of this activity happens in less than a split second and without conscious thought. At the end of this process, the brain has the task of interpreting the message and making the decision as to what to do with this new information. (Carlson, 2011.Pg.45-52)

When a membrane is excited depolarization begins. When the membrane depolarizes the resting membrane potential of -70 mV becomes less negative. When the membrane potential reaches 0 mV, indicating there is no charge difference across the membrane. the sodium ion channels start to close and potassium ion channels open. By the time the sodium ion channels finally close. The membrane potential has reached +35 mV. The opening of the potassium channels allows K+ to flow out of the cell down its electrochemical gradient ( ion of like charge are repelled from each other). The flow of K+ out of the cell causes the membrane potential to move in a negative direction. This is referred to as repolarization. ( Marieb & Mitchell, 2009). As the transmembrane potential comes back down towards its resting potential level and the potassium channels begins to close, the trasmembrane potential level goes just below -90mV, causing a brief period of hyperpolarization (Martini, Nath & Bartholomew, 2012). Finally, as the potassium channels close, the membrane turns back to its resting potential until it is excited or inhibited again.

Lidocaine blocks the voltage-gated Na+ channels between R1 and R2, which blocks the propagation of the action potential from R1 to R2. The effect of lidocaine differs

Whenever the balance is altered, the process of transmitting electrical signals, which is called action potential initiates by carrying information across a neuron’s axon; which is called resting membrane potential. This process occurs as uneven ions distribution flow across cell membrane, creating electrical potential. As a result, the duration of active potential can be as fast as 1 ms. Similarly, the average resting membrane is between -40 mV and -80 mV. Since the membrane from inside is more negatively charged than the outside, it reflected on the negative average voltage readings of the resting membrane.

Most neurons do not make direct connections with surrounding neurons, signals (molecules) must make the transition from the presynaptic (upstream) neuron to the postsynaptic (downstream) neuron. This transition space is called the synaptic cleft. The exchange of information from the pre- to postsynaptic neuron is called a synapse.