Download Sensing the Environment

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
Nerves allow us to perceive the environment
while the brain integrates the incoming signals
to determine an appropriate response.
CB 48.3
Neurons: cells specialized for
transmitting signals
CB 48.4
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. 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
electrical
at synapse
chemical
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
http://www.blackwellpublishing.com/matthews/actionp.html
electrical
at synapse
chemical
electrical
Nerves allow us to perceive the environment
while the brain integrates the incoming
signals to determine an appropriate response.
CB 48.3
CB 49.4
The brain and the
central nervous
system integrate
the various
incoming signals
Different regions of the cerebral cortex
integrate different inputs/outputs
CB 49.15
Visualizing the specialization of brain regions
CB 49.17
Some body parts have more sensory input/
motor control
CB 49.16
Some responses are to subtle stimuli
CB 48.3
Circadian Rhythms: daily patterns set by light
(northern flying squirrel)
We are not conscious of much of what happens
in the brain
CB 48.3
Today’s video about different human
reactions to cool:
http://www.youtube.com/watch?v=XHmM7gJhscU
Nervous System Signaling
Stimulus
Integration
Transduction
Transmission
Response
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
too long
eyeballs
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
neurotransmitter
Fig 50.22
Membrane depolarized
light
Signal sent
No
inhibitory
neurotransmitter
Fig 50.22
Polar Membrane
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
Response
Responses can be
release of hormones,
change in cell activity,
or muscle contraction