Chapter 2: Basic Principles of Sensory Physiology Flashcards
neurons
store electrical signals
cell body
contains mechanisms to keep the cell alive
dendrites
branch out from the cell body to receive electrical signals from other neurons
axon
filled with fluid that conducts electrical signals
sensory receptors
neurons specialized to respond to environmental stimuli
how are electrical signals measured
using small electrodes
recording electrode
an electrode with its recording tip inside the neuron
reference electrode
an electrode located some distance away from the neuron so it is not affected by the electrical signals
what is the resting potential of a neuron?
the negative charge of the neuron relative to its surroundings (-70 mV)
action potential
a predictable rise and fall of the charge inside the axon relative to the outside
what is the neuron’s membrane potential at the peak of an action potential?
40 mV
propagated response
once the response is triggered, it travels down the axon without decreasing in size
refractory period
the interval between the time one nerve impulse occurs and the next one can be generated in the axon
spontaneous activity
action potentials that occur in the absence of environmental stimuli
size of an action potential
remains the same no matter how intense the stimulus is
changing the stimulus intensity & action potentials
affects the rate of firing
ions
molecules that carry an electric charge
where is Na+ most concentrated
outside the axon
where is K+ most concentrated?
inside the axon
permeability
the ease with which a molecule can pass through the membrane
depolarization
an increase in positive charge inside the neuron
what causes depolarization
an inflow of positively charged sodium ions
hyperpolarization
an increase in the negative charge inside the neuron
what causes hyperpolarization
the rush of positively charged potassium ions out of the neuron
sodium-potassium pump
continuously pumps sodium out and potassium into the neuron to maintain the resting potential
synapse
the small space between neurons
neurotransmitter
chemical messengers that are stored in synaptic vesicles
excitatory response
When the neuron becomes depolarized and the inside of the neuron becomes more positive
inhibitory response
when the neuron becomes hyperpolarized and the inside of the neuron becomes more negative
sensory coding
how neurons represent various characteristics in the environment
specificity coding
a specialized neuron that responds only to one concept or stimulus
grandmother cell
another word for specificity coding
quiroga neural representation study
in patients undergoing brain surgery for epilepsy, some neurons responded to many ways of representing a person or building
sparse coding
when a particular stimulus is represented by a pattern of firing of only a small group of neurons, with the majority of the neurons remaining silent
population coding
our experiences are represented by the pattern of firing across a large number of neurons
phrenology
observing the skull to determine an individual’s psychological attributes
modularity
specific brain areas are specialized to respond to specific types of stimuli or functions. Made evident by Broca’s & Wernicke’s areas
broca’s area
an area in the left frontal lobe responsible for speech production
wernicke’s area
an area in the temporal lobe involved in understanding speech
neuropsychology
relating the location of brain damage to specific effects on behaviour
brain imaging
recording brain responses to create pictures of the location of the brain’s activity
Magnetic Resonance Imagining (MRI)
a technique used to reveal brain structures
Functional Magnetic Resonance Imaging (fMRI)
enables researchers to determine how various types of cognitions activate different areas of the brain
how do fMRIs work?
Takes advantage of the fact that blood flow increases in activated brain areas. Hemoglobin, which carries oxygen in the blood contains a ferrous molecule and has magnetic properties
voxels
small cube-shaped subdivisions of the brain
reading an fMRI
Hotter colours indicate higher activation and cooler colours indicate lower activation. Coloured areas represent the difference between the task-related and resting-state fMRI
Task-related fMRI
the fMRI measured when a person is engaged in a specific task
resting-state fMRI
the fMRI measured when the brain is not involved in a specific task
distributed representation
Occurs when a stimulus causes neural activity in several different areas of the brain, so the activity is distributed across the brain
structural connectivity
the road map of fibres connecting different areas of the brain
functional connectivity
the neural activity associated with a particular function that is flowing through this structural network
measuring resting state functional connectivity
- Use task-related fMRI to determine the seed location: brain location associated with carrying out a specific task
- Measure the resting-state fMRI at the seed location
- Measure the resting state fMRI at another location, called the test location
- Calculate the correlation between the seed and test location responses
functional vs. structural connections
Just because two areas are functionally connected doesn’t mean that they are structurally connected (directly communicate by neural pathways). But, they are related; regions with high structural connectivity often have high functional connectivity
the mind-body problem
How do physical processes become transformed into the richness of perceptual experience?
what kind of problem is the mind-body problem
causational
Selective
The fibre is permeable to one specific type of molecule
how long does an action potential last
1ms
basic properties of action potentials
- Propagated response
- Remain the same size regardless of stimulus intensity
- Increase in rate to increase in stimulus intensity
- Have a refractory period of 1 ms
- Upper firing rate is 500-800 impulses per second
- Show spontaneous activity that occurs without stimulation
when are electrical signals generated in neurons?
when ions cross the membranes of neurons
the release of neurotransmitters
by the presynaptic neuron from vesicles. Received by the postsynaptic neuron on receptor sites. Matched, like a key to a lock, into specific receptor sites. Used as triggers for voltage change in the postsynaptic neuron
ways to activate receptors
Membrane deformation
Voltage gated
Neurotransmitter gated
how can modularity be studied?
by recording brain responses in neurologically normal humans using brain imaging, making it possible to create pictures of the location of the brain’s activity
what does the distributed approach focus on?
the activity in multiple brain areas and the connections between those areas
