Distinguish between genotype and phenotype; homozygous and heterozygous

Genotype is the gene makeup of the organism Ex: Gg while phenotype is the physical description to the trait Ex: green

Homozygous is when both alleles for the trait are the same Ex: GG and gg while heterozygous is when the alleles are different Ex: Gg

Explain nerve impulse transmission from a receptor to effector in the simplest nerve pathway.

<ul> <li>Receptor: It all starts with a receptor, which is like a sensor in your body that detects a stimulus (like touch, heat, light, etc.). For example, if you touch something hot, the receptors in your skin detect the heat.</li> <li>Sensory Neuron: When the receptor detects a stimulus, it sends a signal along a sensory neuron. Think of a sensory neuron as a messenger that carries the message from the receptor to the next stop.</li> <li>Spinal Cord: The sensory neuron sends the signal to the spinal cord, which is like a relay station in your body. It's a bundle of nerves that runs down your back.</li> <li>Interneuron (Optional): Sometimes, the signal might need to pass through an interneuron in the spinal cord. Interneurons help process and relay information within the spinal cord.</li> <li>Motor Neuron: Once the signal reaches the spinal cord (or sometimes directly from the sensory neuron), it travels along a motor neuron. Motor neurons carry messages from the spinal cord to muscles or glands.</li> <li>Effector: Finally, the signal reaches the effector, which is the muscle or gland that responds to the stimulus. For example, if you touched something hot, the effector might be the muscles in your arm that quickly pull your hand away.</li> </ul> <br>

Explain the transmission of a nerve impulse along an axon- an Action potential

1. Resting State: The axon (a part of the neuron) is like a tiny wire with a negative charge inside.
2. Stimulus: When something triggers the neuron, like a touch, it lets positive ions inside. This makes the inside less negative, or "depolarized".
3. Depolarization: This change in charge starts a chain reaction where nearby areas of the axon also become less negative, creating a wave called an action potential.
4. Propagation: The action potential travels along the axon like a wave, pushing the message forward.
5. Recharge: After passing, the axon recharges by pushing positive ions out, making the inside negative again.
6. One-Way Traffic: Once it fires, the axon needs a moment to recharge before it can fire again. This ensures the message moves in one direction.
7. Passing the Message: At the end of the axon, the message is passed to the next neuron by releasing chemicals called neurotransmitters into a gap.

Describe the changes in polarity along an axon during an action potential

• Resting State: At rest, the inside of the axon is negatively charged compared to the outside. This is because there are more negative ions inside and positive ions outside.
• Depolarization: When a stimulus triggers the neuron, like a touch, sodium channels open, allowing positive sodium ions to rush into the axon. This makes the inside less negative and starts depolarization.
• Action Potential: As more sodium ions flow in, the inside becomes positive compared to the outside. This rapid change in charge along the axon is the action potential.
• Repolarization: After the action potential passes, potassium channels open, allowing positive potassium ions to leave the axon. This restores the negative charge inside, repolarizing the axon.
• Hyperpolarization (Optional): Sometimes, potassium channels stay open a bit longer, causing the inside of the axon to become even more negative than at rest. This is called hyperpolarization.
• Resting State Restored: Eventually, the sodium-potassium pumps work to restore the original balance of ions, bringing the axon back to its resting state.