Sensing and Responding to the Environment

Nerves allow us to perceive the environment while the brain integrates the incoming signals to determine an appropriate response. CB 48.3

http://www.boingboing.net/2011/04/11/how-magnets-affect-t.html CB 49.17

Neurons: cells specialized for transmitting signals CB 48.4 Neurons: cells specialized for transmitting signals

In the brain neurons are shorter and highly interconnected Fig 48.5

Signals move through neurons in one direction Fig 48.4 Axon Signals

Signals move along a neuron via movement of ions across the membrane Fig 48.4 Axon Signals

Ion movement across the membrane causes the signal to travel from one end to the other Fig 48.11

At rest a neuron is polarized At rest a neuron is polarized. The electrical signal is a depolarization that moves along the neuron. Fig 48.11

At the synapse the electrical signal is converted to a chemical signal: neurotransmitters at synapse chemical electrical electrical

at synapse chemical electrical electrical http://www.blackwellpublishing.com/matthews/actionp.html at synapse chemical electrical electrical

Neurons are commonly connected to many other neurons, and the effect of the different incoming signals determines what the neuron will do. CB 48.14

Nervous System Signaling Stimulus Integration Transduction Transmission Response

Smells are detected by receptor neurons in our nose Smells are detected by receptor neurons in our nose. Each receptor is sensitive to a different chemical Fig 50.15

Activating more neurons leads to stronger perception Fig 50.15

This stretch sensitive neuron transduces different signals depending on the amplitude of the stimulus Fig 50.2

Light is detected in the eye by receptors on the retina Fig 50.18

Some vision problems arise from misshapen eyeballs too long too short Fig 50.19

AAL 42.10

Light receptor neurons of the eye: Rods detect black and white Cones detect colors…one type of cone for each color - red, blue, and green

No light No Signal Inhibitory neuro- transmitter Membrane depolarized Fig 50.22

No inhibitory neuro- transmitter light Signal sent Polar Membrane Fig 50.22

Vertebrate retina structure Fig 50.23

Nerves allow us to perceive the environment while the brain integrates the incoming signals to determine an appropriate response. Fig 46.1 Responses can be release of hormones, change in cell activity, or muscle contraction Response

Next: Consciousness Reports due Th 4/21