AaBbC 1 NormalStrong Styles Paragtaph Essay: Using all neuronal types involved a

Question

AaBbC 1 NormalStrong Styles Paragtaph Essay: Using all neuronal types involved and the related effector shown, explain what is happening in the below diagram of a reflex arc. The following concepts are a must: 1) summation of an AP at the axon hillock; 2) resting membrane potential in a neuron and how it is maintained by essential channels and pumps (diagram, please), 3) the conduction of an action potential showcasing essential channels and pumps and the meaning of "threshold" (diagram of this process and a AP labeling axes): 4) relay of the AP across a chemical synapse using excitatory neurotransmitters; 5) relay of the AP at the NMJ and the ultimate "sliding of filaments" in the sarcomere (diagram of relaxed and contracted sarcomere). ic representation of a reflex are involving a somatic (skeletal musele) motor neuron. ??

Explanation / Answer

Signals from various inputs would vary both spatially and temporally. These signals may lead to inhibitory or excitatory APs. Summation of all APs at axon hillock may or may not generated threshold potential to further generate an Action potential.

Resting membrane potential is -70mV and is closer to potassium equilibrium. In a cell the sodium ions are abundant outside while potassium are more inside. This potassium balances the anions, organic molecules like malate. However, in the membrane are some leaky potassium channels through which potassium keeps moving out making the inside of the membrane more negative and giving it a negative resting membrane potential

When a threshold potential is received, an action potential is generated. Voltage gated sodoum ions open in response to threshold potential through which sodium ions move in making the inside more positive and depolarising the membrane. As the membrane is repolarized further these sodium channels are inactivated during which potassium channels open and start the transport of potassium ions, this finally repolarized the membrane making the inside more negative. This process distributes the two ions different from when they were present at resting potential. another pump called Na/K pump, pumps 3 sodium ions out and 2 potassium ions inside, resdiatributing the ions so as to generate another action potential. Refractory periods are short periods after action potential during which another action potential cannot be generated. Absolute refractory period refers to the period when no matter how strong is the threshold another action potential won't be generated. This corresponds to the period when the voltage gated sodium channels are inactivated. Relative refractory period is when these channels are in a closed state and a high enough threshold can generate an action potential. Threshold is the minimum potential that is needed to generate an action potential

When the action potential reaches the axon terminals, synaptic vesicles which contain the neurotransmitters are released into the synapse. These neurotransmitters can be excitatory or inhibitory depending on which an excitatory action potential or inhibitory action potential is generated in the post synaptic neuron. The neurotransmitter released by the pre synaptic neuron is perceived by the receptors in the post synaptic neurons which leads to opening of cation channels. in case of excitatory potential, sodium enters the cell body of the postsynaptic neuron generating a threshold which is then relayed along the axon body.

At the NMJ, the pre synaptic neuron releases acetylcholine and is perceived by musacrinic receptors on post synaptic neurons. This leads to opening of cation channels that bring in sodium ions to generate an excitatory action potential.

As an action potential is received by the muscle fibre, the concentration of calcium ions are increased in the cytosol of sarcomere. This calcium bind the troponin that has masked the site sites of myosin at the actin filaments. As the myosin heads are able to now interact with the actin filaments, they undergo power stroke movement and cycles of it to undergo contraction and relaxation.

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