What are receptor organs, and how do they work?
- Organs specialized to detect a certain stimulus
- Receptor cells within the organs convert stimuli into electrical signals
- They are very diverse but all end up converting stimuli into neuronal input
What is an adequate stimulus?
The type of stimulus to which a sensory organ is particularly adapted
- Example –> photic energy to the eye
What is sensory transduction?
Conversion of energy from stimulus into a change in membrane potential in a receptor cell
What does the doctrine of specific nerve energies say?
- Receptors and neural channels for different senses are independent.
- The concept of labeled lines says that the brain recognizes distinct senses because action potentials travel along separate nerve tracts
What do labeled lines consist of?
- Different lines for different senses
- We can even distinguish different types of touch because we have different receptors and lines for each type
What does Merkerl’s disc detect?
Fine touch
- Small, sharp borders
What does Meissner’s corpuscle detect?
Light touch
- Small, sharp borders
What does the hair follicle receptor detect?
Touch
What does the Pacinian corpuscle detect?
Vibration and pressure
- Large, vague borders
What does Ruffini’s ending detect?
Stretch
- Large, vague borders
What do free nerve endings in the epidermis detect?
Pain and temperature
How does the Pacinian corpuscle work?
- Skin receptor that detects vibration and pressure
- Stimulus opens stretch-sensitive sodium channels made of a protein called Piezo and produces a graded receptor potential
- When it reaches the threshold and AP is generated
- You only detect touch if the AP is generated
How is stimulus location detected?
- From the position of the activated receptors
How is the intensity of sensory effects detected?
- AP produced by the same sensory neurons always have the same size
- Intensity is encoded in the number and frequency of APs
What does it mean that some sensory systems have neurons that specialize?
- They specialize in one part of a range of intensities
- As the strength of a stimulus increases, more neurons sensitive to higher intensities are recruited
What is adaptation (in terms of sensory processing)?
The progressive loss of response to a maintained stimulus.
Sensory systems emphasize change in stimuli, as that is more important for survival.
This prevents the NS from being overwhelmed by too much information coming in
What are phasic receptors?
They display adaptation and decrease frequency of action potentials
What are tonic receptors?
Show slow or no decline in action potential frequency
What are other ways to control information?
- Accessory structures, such as eyelids
- Top-down processing - higher brain centers suppress some sensory inputs and amplify others
What is the dorsal column system, and how does it work?
- Delivers touch information to the brain.
- The stimulus triggers the receptive field of a neuron
- These receptors send projections via the dorsal column of the spinal cord, where they synapse on the dorsal column nuclei in the medulla
- Axons from neurons in the medulla cross the midline and go to the thalamus for initial processing, and then on to the primary somatosensory cortex
- So, the brain processes touch information from the contralateral side of the body
What is the receptive field, and how does it work?
- The region in which a stimulus will alter a sensory neuron’s firing rate
- They differ in size, shape, and responses to types of stimulation
- To determine what touch a cortical neuron responds to, you can record from the cell and touch different parts of the body
- The cell will fire when you touch the area it responds to
Are receptive fields bigger in the back or finger tips?
Back, which is why it’s harder to distinguish between touch at two points
What do the order and sizes of cortical representations for different regions of the skin depend on?
Information from the hand and fingers takes up much more room than does information from the shoulder. A larger area means more neurons; the size is not proportional to the size of the body part.
Are cortical representations fixed?
- No
- They can be changed by experience
- Intentional stimulation of a specific body region can expand its cortical stimulation.
- Loss of use will cause it to shrink
- Cells in the missing digit move to respond for other fingers –> re-organize
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Chapter 1: Behavioral Neuroscience: Scope and Outlook11
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Brain Dissection Quiz29
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Chapter 2: Functional Neuroanatomy: The Nervous System and Behavior23
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Chapter 351
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Chapter 4: Neurotransmitters and Neuropharmacology58
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Chapter 5 - Hormones and the brain30
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Chapter 12 - Sexual determination and differentiation21
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Chapter 12 - Sex: Evolutionary, Hormonal and Neural Bases31
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Chapter 7 - Life-span development of the brain and behavior43
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Chapter 13 - Homeostasis34
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History of biopsychology43
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Chapter 17 - Learning and Memory22
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Emotions, aggression and stress34
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Sensory processing40
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Hearing and taste42
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Vision24
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Mental disorders24
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Rhythms and sleep37
