Be able to describe the structures and functions of these systems and how they work together; (name at least one structure for each system (for example Digestive System Structured-Intestines stomach)d function: to digest and break down food particles to be used for energy.

Here’s an overview of the structures and functions of the nervous, circulatory, respiratory, and muscular systems, as well as how these systems work together:

### Nervous System
- **Structures:** Brain, spinal cord, nerves
- **Function:** To coordinate and control body activities, process sensory information, and facilitate communication between different parts of the body. It allows for voluntary and involuntary responses to stimuli.

### Circulatory System
- **Structures:** Heart, blood vessels (arteries, veins, capillaries)
- **Function:** To transport nutrients, gases (such as oxygen and carbon dioxide), hormones, and waste products throughout the body. It plays a crucial role in maintaining homeostasis and ensuring that tissues receive the necessary materials for function.

### Respiratory System
- **Structures:** Lungs, trachea, bronchi
- **Function:** To facilitate gas exchange by bringing oxygen into the body and removing carbon dioxide. The respiratory system works closely with the circulatory system to ensure oxygen is delivered to cells and carbon dioxide is expelled.

### Muscular System
- **Structures:** Skeletal muscles, smooth muscles, cardiac muscle
- **Function:** To enable movement of the body and its parts, maintain posture, and produce heat through muscle contractions. This system is essential for voluntary movements (like walking) and involuntary movements (like the pumping of the heart).

### Integration of Systems
These systems work collaboratively to maintain overall body function.

- The **nervous system** sends signals to the **muscular system** to initiate movement based on sensory inputs.
- The **circulatory system** ensures that oxygen from the **respiratory system** reaches the muscles and other organs, providing the energy needed for function.
- Collectively, they help the body respond to environmental changes, perform daily activities, and maintain homeostasis. For instance, during exercise, the nervous system signals the heart to pump faster (circulatory system) and the lungs to increase oxygen intake (respiratory system) while the muscles work harder to generate movement.