Coordination in animals (A - level), lesson 1 of 2

Differences between nervous and endocrine system, action potential, impulse, none or nothing law, refractory period, synapse, transmission at the synapse, neuromuscular junction, functions of the synapses.




Differences between Nervous and Endocrine Systems:

1. Communication:
- Nervous System: Uses electrical impulses (action potentials) for rapid communication.
- Endocrine System: Uses chemical messengers called hormones for slower, long-distance communication.

2. Mode of Transmission:
- Nervous System: Transmits information through neurons via synapses.
- Endocrine System: Releases hormones into the bloodstream to target specific tissues or organs.

3. Speed of Response:
- Nervous System: Responds rapidly, enabling quick reflexes and immediate reactions.
- Endocrine System: Responds more slowly, with effects taking minutes to hours, but lasts longer.

4. Duration of Effect:
- Nervous System: Effects are short-lived.
- Endocrine System: Effects are long-lasting.

Action Potential:
- An action potential is a rapid electrical impulse that allows neurons to transmit signals throughout the nervous system.
- It is generated when the membrane potential of a neuron depolarizes, reaching a threshold level, causing a cascade of voltage-gated ion channels to open and initiate the action potential.
- The action potential propagates down the axon of a neuron, allowing for long-distance transmission of signals.

Impulse:
- An impulse refers to the rapid transmission of an action potential along the length of a neuron.
- It involves the depolarization and repolarization of the neuron's membrane.
- The impulse allows for the efficient and coordinated communication of signals in the nervous system.

All-or-None Law:
- The all-or-none law states that once a neuron's membrane potential reaches the threshold level, an action potential is generated and transmitted along the neuron.
- The size or intensity of the stimulus does not affect the amplitude or speed of the action potential; it either fires completely or does not fire at all.

Refractory Period:
- The refractory period is a brief period of time following an action potential when the neuron cannot generate another action potential.
- It allows the neuron to recover and reset its ion channels before firing again, ensuring proper signal transmission and preventing continuous firing.

Synapse:
- A synapse is a junction between two neurons or between a neuron and an effector cell (such as a muscle or gland).
- It is the site where communication occurs between these cells.
- At the synapse, the electrical signal of the presynaptic neuron is converted into a chemical signal in the form of neurotransmitters.

Transmission at the Synapse:
- Transmission at the synapse involves the release of neurotransmitters from the presynaptic neuron, which diffuse across the synaptic cleft and bind to receptors on the postsynaptic neuron or effector cell.
- This binding triggers a response in the postsynaptic neuron or effector cell, propagating the signal across the synapse.

Neuromuscular Junction:
- The neuromuscular junction is a specialized synapse between a motor neuron and a muscle fiber.
- It is responsible for transmitting signals from the motor neuron to the muscle, leading to muscle contraction.

Functions of Synapses:
- Mediating the transmission of signals between neurons, allowing for communication within the nervous system.
- Integrating and processing incoming signals, allowing for complex and coordinated responses.
- Modulating and amplifying signals, enabling effective communication and control of bodily functions.
- Allowing for synaptic plasticity, which is crucial for learning, memory formation, and neural adaptability.