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 48.4 Neurons: cells specialized for transmitting 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 at synapse chemical At the synapse the electrical signal is converted to a chemical signal: neurotransmitters

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

electrical at synapse chemical

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 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:

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 Light is detected in the eye by receptors on the retina

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

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

Fig Inhibitory neuro- transmitter No light Membrane depolarized No Signal

Fig Polar Membrane light No inhibitory neuro- transmitter Signal sent

Fig 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