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