Biology 373 Unit 3
Signal Transduction - Graded Potentials - correct answer ✔✔-each sensory receptor has an adequate
stimulu
-type of energy to which it responds best
-thermoreceptors -> respond best to increase temp (vs pressure)
-mechanoreceptors -> deformations of membrane that open ion channels
-photoreceptors of the eye -> light
-stimulus opens or closes ion channels in receptor cell membrane
-directly to via second messenger systems
Mostly: open cation channels -> influx of Na or Ca -> depolarization
sometimes: efflux of K -> hyperpolerization
-Change in membrane potential (graded potential)= receptor potential
Sensory neurone have receptive fields - correct answer ✔✔somatosensory neurones and visual neurons
are activated by stimuli that fall within a certain physical area
-cutaneous receptors - patch of skin
-photoreceptors - light falling on area of retina
at least two afferent neurons in pathway to brain
-first oder (primary) sensory neuron
-directly associated with stimuli
-second order (secondary) neuron
-relays information from first neruon
receptive field often defined by neurons further up the pathway
, -sensory input can then be gathered from more than one primary sensory neuron
Sensory pathway to CNS - correct answer ✔✔somatic senses, hearing, vision, taste : to appropriate
cortex after processing in thalamus
Olfactory: direct to brain (olfactory bulb -> olfactory cortex)
Equilibrium: mostly to cerebellum, minor input to thalamus
What about visceral sensory information?
-mostly integrated in brain stem and spinal cord
-does not usually reach conscious perception
-completely subconscious -> blood pressure
-can reach consciousness -> 'fullness' (pressure), pain
Senstations are decoded and processed in the CNS - correct answer ✔✔-all stimuli converted to graded
potentials -> APs
-All APs are identical
So how are different sensations distinguished?
CNS must be able to decode:
-type of stimulus -> modality (sound, touch)
-location (where)
-intensity (how hard)
-duration (how long, start/stop)
Stimulus intensity - correct answer ✔✔Coded by:
1. number of receptors activated (population coding)
-different thresholds for stimulation among group of receptors
-with low intensity stimulus, most sensitive (lowest threshold) receptors recruited first
Signal Transduction - Graded Potentials - correct answer ✔✔-each sensory receptor has an adequate
stimulu
-type of energy to which it responds best
-thermoreceptors -> respond best to increase temp (vs pressure)
-mechanoreceptors -> deformations of membrane that open ion channels
-photoreceptors of the eye -> light
-stimulus opens or closes ion channels in receptor cell membrane
-directly to via second messenger systems
Mostly: open cation channels -> influx of Na or Ca -> depolarization
sometimes: efflux of K -> hyperpolerization
-Change in membrane potential (graded potential)= receptor potential
Sensory neurone have receptive fields - correct answer ✔✔somatosensory neurones and visual neurons
are activated by stimuli that fall within a certain physical area
-cutaneous receptors - patch of skin
-photoreceptors - light falling on area of retina
at least two afferent neurons in pathway to brain
-first oder (primary) sensory neuron
-directly associated with stimuli
-second order (secondary) neuron
-relays information from first neruon
receptive field often defined by neurons further up the pathway
, -sensory input can then be gathered from more than one primary sensory neuron
Sensory pathway to CNS - correct answer ✔✔somatic senses, hearing, vision, taste : to appropriate
cortex after processing in thalamus
Olfactory: direct to brain (olfactory bulb -> olfactory cortex)
Equilibrium: mostly to cerebellum, minor input to thalamus
What about visceral sensory information?
-mostly integrated in brain stem and spinal cord
-does not usually reach conscious perception
-completely subconscious -> blood pressure
-can reach consciousness -> 'fullness' (pressure), pain
Senstations are decoded and processed in the CNS - correct answer ✔✔-all stimuli converted to graded
potentials -> APs
-All APs are identical
So how are different sensations distinguished?
CNS must be able to decode:
-type of stimulus -> modality (sound, touch)
-location (where)
-intensity (how hard)
-duration (how long, start/stop)
Stimulus intensity - correct answer ✔✔Coded by:
1. number of receptors activated (population coding)
-different thresholds for stimulation among group of receptors
-with low intensity stimulus, most sensitive (lowest threshold) receptors recruited first
