The Nervous System Physiology Unit CA Biology Standard 9

 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

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.

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

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

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.

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

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

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

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.

The Reflex Arc 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

Stimuli Effector