The Nervous System

1. The Nervous System Physiology Unit CA Biology Standard 9

2. Standard 9a: Students know how the complimentary activity of major body systems provides cells with oxygen and nutrients and removes toxic waste products such as carbon dioxide. • Think about it…..How do the following body systems act together to maintain homeostasis? Digestive System, Respiratory System, Circulatory System

3. Standard 9a • Digestive System • Breaks down food and delivers glucose to the circulatory system. • Respiratory System • Takes in Oxygen molecules through the lungs and delivers to the circulatory system. • Receives CO2 waste from the circulatory system and removes from the body through the lungs. • Circulatory System • Carries glucose and oxygen to cells so they can use them during cellular respiration to make ATP • Takes waste products like CO2 to the appropriate place for removal from the body.

4. What is the Nervous System? • Recognizes and coordinates the body’s response to changes in its internal and external environment. • Parts of the System: • Brain • Spinal Cord • Peripheral Nerves • A.K.A. Neurons or Nerve Cells

5. Divisions of the Nervous System • Central Nervous System (CNS) • The control center of the body • Relays messages, processes information, and analyzes information • Consists of the brain and the spinal cord • Peripheral Nervous System (PNS) • Lies outside of the CNS • Consists of all nerves and associated cells that are NOT included in the spinal cord • Sensory Division: Transmits impulses from sense organs to the CNS • Motor Division: Transmits impulses from the CNS to the muscles or glands

7. Neurons • Cells that transmit nerve responses. • 3 Main Types • Sensory Neurons: Receive signals from the external environment. • Interneurons: Carry messages to other neurons. • Motor Neurons: Tell muscles to move in response to external signal.

8. The Brain • Contains about 100 billion neurons • Weighs about 1.4 kg • Cerebrum • Voluntary, conscious activities • Cerebellum • Coordinates activity so muscles can move efficiently • Brain Stem • Connects the brain to the spinal cord • Controls blood pressure, heart rate, breathing & swallowing • Hypothalamus • Recognition of hunger, thirst, fatigue, anger and temperature. • Coordinates nervous & endocrine systems • Grey Matter • Mostly neuron cell bodies • White Matter • Mostly neuron axons

9. Spinal Cord • Main communication link between the brain and the rest of the body • 31 pairs of spinal nerves branch out from the spinal cord connecting the brain to all parts of the body • Reflexes are processed directly in the spinal cord

10. Standard 9b • Students know how the nervous system mediates communication between different parts of the body and the body’s interaction with the environment.

11. What is a Reflex? • Reflex: A quick, automatic response to a stimulus. Pathway occurs along the Central Nervous System (CNS). • Stimulus: Environmental item that is sensed by an individual. • Example: temperature, pressure, smells, tastes, light and sounds • Individuals become aware of the environment through the sense organs and other receptors • The body responds to stimuli through reflex arcs.

12. TheReflexArc • Stimuli is sensed by receptors in skin • Message detected by sensory neurons • Message sent to interneurons in the spinal cord • Motor neurons then tell the muscle to move and respond to the stimuli • The muscle is referred to as an effector

13. Stimuli Effector