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This week: Sensing and Responding to the Environment
Sensing and reacting to the environment is critical
Failure to properly sense and react to the environment can be fatal
CB 48.3
Nerves allow us to perceive the environment while the brain integrates the incoming signals to determine an appropriate response.
CB 48.4Neurons: cells specialized fortransmitting signals
In the brain neurons are shorter and highly interconnected
Fig 48.5
Axon
Signals move through neurons in one direction
Signals
Fig 48.4
Axon
Signals move along a neuron via movement of ions across the membrane
Signals
Fig 48.4
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. The electrical signal is a depolarization that moves along the neuron.
Fig 48.11
electrical electricalat synapse chemical
At the synapse the electrical signal is converted to a chemical signal: neurotransmitters
CB 48.14
Neurons are commonly connected to many other neurons, and the effect of the different incoming signals determines what the neuron will do.
electrical electricalat synapse chemical
http://www.blackwellpublishing.com/matthews/actionp.html
CB 48.3
Nerves allow us to perceive the environment while the brain integrates the incoming signals to determine an appropriate response.
The brain and the central nervous system integrate the various incoming signals
CB 49.4
Different regions of the cerebral cortex integrate different inputs/outputs
CB 49.15
CB 49.17
Visualizing the specialization of brain regions
Some body parts have more sensory input/motor control
CB 49.16
CB 48.3
Some responses are to subtle stimuli
Circadian Rhythms: daily patterns set by light(northern flying squirrel)
CB 48.3
We are not conscious of much of what happens in the brain
Today’s video about different human reactions to cool:http://www.youtube.com/watch?v=XHmM7gJhscU
Nervous System Signaling
Stimulus
Transduction Transmission
Response
Integration
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
Fig 50.2
This stretch sensitive neuron transduces different signals depending on the amplitude of the stimulus
Fig 50.18
Light is detected in the eye by receptors on the retina
Fig 50.19
Some vision problems arise from misshapen eyeballs too long
too short
AAL 42.10
Light receptor neurons of the eye:Rods detect black and whiteCones detect colors…one type of cone for each color - red, blue, and green
Fig 50.22
Inhibitoryneuro-transmitter
No light
Membrane depolarized
No Signal
Fig 50.22Polar Membrane
light
Noinhibitoryneuro-transmitter
Signal sent
Fig 50.23
Vertebrate retina structure
Fig 46.1
Nerves allow us to perceive the environment while the brain integrates the incoming signals to determine an appropriate response.
Response
Responses can be release of hormones, change in cell activity, or muscle contraction