Control and Coordination

Synapse

Step 1: Neurons don't touch each other directly; there's a small gap between them. Step 2: This gap or junction between two neurons is called a synapse. Step 3: When a nerve impulse reaches the end of one neuron, chemicals called neurotransmitters are released. Step 4: These chemicals cross the synaptic gap and start an impulse in the next neuron. Step 5: This allows information to pass from one neuron to another throughout the nervous system.

Goitre

Step 1: The thyroid gland in our neck needs iodine to make thyroid hormone. Step 2: When we don't get enough iodine in our diet, the thyroid gland enlarges to try to make more hormone. Step 3: This enlargement of the thyroid gland is visible as swelling in the neck, called goitre. Step 4: To prevent goitre, iodized salt is used which contains the required iodine. Step 5: Diabetes is due to insulin deficiency, while dwarfism and gigantism are due to growth hormone problems.

Medulla oblongata

Step 1: The medulla oblongata is the lowest part of the brain stem connected to the spinal cord. Step 2: It controls vital life functions that happen automatically without our conscious control. Step 3: These include breathing, heartbeat, blood pressure, and digestion. Step 4: Injury to the medulla can be fatal because these vital functions may stop. Step 5: The cerebrum controls voluntary actions, cerebellum controls balance, while spinal cord controls reflexes.

Motor, sensory, and connecting neurons

Step 1: Based on their function, neurons are classified into three types. Step 2: Sensory neurons carry messages from sense organs (eyes, ears, skin) to the brain and spinal cord. Step 3: Motor neurons carry messages from the brain and spinal cord to muscles and glands for action. Step 4: Connecting (association) neurons are found in the brain and spinal cord and connect sensory and motor neurons. Step 5: This classification is based on what job each type of neuron does in the nervous system.