Review List three body systems that work together to create a response to a stimulus Sequence What is the correct sequence of the following in response to a stimuli: interneuron, motor neuron, sensory neuron, muscle Review What are two general ways in which nervous systems differ among animal groups 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 II 28.1 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 Sensory neurons 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 Medulla oblongata Coordinates movement and controls balance Controls functioning of many internal organs.

Optic lobes Olfactory bulbs Involved in vision 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.