12.1 What is Coordination and Response?
- Coordination: The process by which organisms respond to changes in their internal and external environments.
- Systems Involved: Nervous and endocrine systems.
12.2 The Nervous System
- Central Nervous System (CNS): Brain and spinal cord.
- Peripheral Nervous System (PNS): Nerves connecting CNS to the rest of the body.
- Neuron: A specialized cell that transmits electrical impulses.
| Part of Neuron | Function |
|---|
| Dendrites | Receive impulses from other cells. |
| Axon | Transmits impulses away from the cell body. |
| Myelin Sheath | Insulates axons, speeds up impulse transmission. |
| Synapse | The gap between two neurons. |
12.3 Reflex Action
- Definition: A quick, involuntary response to a stimulus.
- Example: Pulling hand away from a hot object.
- Reflex Arc: Stimulus → Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector (muscle).
12.4 Hormonal Coordination
- Endocrine System: Produces hormones that regulate various body functions.
- Pituitary Gland: Master gland, controls other glands.
- Thyroid Gland: Produces thyroxine, controls metabolism.
- Adrenal Glands: Produce adrenaline for the fight-or-flight response.
12.5 Plant Responses
- Phototropism: Growth towards light.
- Gravitropism: Growth in response to gravity.
- Auxins: Plant hormones that control growth in response to environmental stimuli.