(b) (i) What is a neuron? (ii) Distinguish between sensory, motor and interneurons (association neurons) - Leaving Cert Biology - Question b - 2006

1. Sensory Neurons: These neurons carry signals from sensory receptors towards the Central Nervous System (CNS). They are responsible for transmitting sensory information such as touch, pain, temperature, and pressure.

2. Motor Neurons: These neurons transmit impulses away from the CNS to effectors such as muscles and glands. They facilitate movement and response by executing actions based on signals received from the CNS.

3. Interneurons: Also known as association neurons, these neurons connect sensory and motor neurons within the CNS. They play a critical role in processing information and reflexes.

Neurotransmitters are chemical substances that transmit signals across a synapse from one neuron to another neuron, muscle, or gland. They are released from the presynaptic neuron and cross the synaptic cleft to bind to receptors on the postsynaptic neuron, triggering an impulse in the next neuron. This process is essential for communication within the nervous system.

1. Schwann Cells: Schwann cells are responsible for producing the myelin sheath that insulates axons in the peripheral nervous system, facilitating faster signal transmission.

2. Myelin Sheath: The myelin sheath acts as insulation for axons, which not only protects the axon but also speeds up the transmission of electrical impulses along the neuron.

1. A Possible Cause: A possible cause of Parkinson’s disease is the genetic predisposition or loss of dopamine-producing neurons in the brain, leading to difficulty in movement and coordination.

2. A Method of Treatment: Possible treatments include physical therapy to help maintain mobility and medication to manage symptoms, which may involve the use of dopaminergic drugs to alleviate the motor symptoms.