1. Review List three body systems that work together to create a response to a stimulus

2. Sequence What is the correct sequence of the following in response to a stimuli: interneuron, motor neuron, sensory neuron, muscle

3. Review What are two general ways in which nervous systems differ among animal groups

4. Review Give an example of an animal with a very simple sensory system and an example of one with a complex sensory system

CH 28 ANIMAL SYSTEMS II28.1 Response

Neurons Specialized nerve cells in the nervous system Acquire information from their surroundings,

interpret that information, and then “decide” what to do about it.

Detecting Stimuli

Stimulus Information in the

environment that causes an organism to react

Sensory neurons Specialized cells that detect

stimuli.

Each type of sensory neuron responds to a particular stimulus such as light, heat, or chemicals

Animals notice light, taste, odor, temperature, sound, water, gravity, and pressure

Humans don’t notice very weak electric currents or Earth’s magnetic field.

Interneurons

Process information and determine how an animal responds to stimuli.

Number of interneurons and the ways those interneurons process information, determine how flexible and complex an animal’s behavior can be.

Some invertebrates have very few interneurons and are capable of only simple responses to stimuli.

Vertebrates have more highly developed nervous systems with large numbers of interneurons and are capable of more-complex behaviors.

Response

Specific reaction to a stimulus Responses are directed by the nervous system Responses are usually not carried out by nerve

cells.

Motor Neurons

Carry “directions” from interneurons to muscles.

Invertebrate Nervous Systems

Range from simple collections of nerve cells to complex organizations that include many interneurons.

Nerve Nets

Simple nervous systems Consist of neurons

connected into a netlike arrangement with few specializations.

Ganglia Interneurons are grouped together and connect with

one another Largest ganglia typically located in the head region and

called cerebral ganglia.

Brain Further organized cerebral ganglia.

Vertebrate Chordates

Show high degree of cephalization and have highly developed nervous systems

Interneurons in brain are connected with each other and with sensory neurons and motor neurons in the head and elsewhere in the body.

Parts of the Vertebrate Brain

Cerebrum

“Thinking” region of the brain Receives and interprets sensory information and

determines a response Also involved in learning, memory, and conscious

thought.

Cerebellum Coordinates movement and controls balance

Medulla oblongata Controls functioning of many internal organs.

Optic lobes Involved in vision

Olfactory bulbs Involved in the sense of smell.

Vertebrate brains connected to rest of the body by a spinal cord Thick collection of nerves Runs through a tube in the vertebral column.

Brain evolution follows a trend of increasing size and complexity from fishes, through amphibians and reptiles, to birds and mammals.

Invertebrate Sense Organs

Detect light, sound, vibrations, movement, body orientation, and chemicals in air or water.

Flatworms, for example, have simple eyespots that detect only the presence and direction of light.

More-cephalized invertebrates have specialized sensory tissues and well-developed sense organs Octopus have complex eyes that detect motion and

color and form images Compound eyes of mosquitoes detect minute changes

in movement and color.

Chordate Sense Organs

Nonvertebrate chordates have few specialized sense organs.

Most vertebrates have highly evolved sense organs Mammalian ears have the

same basic parts, they differ in ability to detect sound.