PSL300 Study Notes

Topics: Sensory system, Nervous system, Olfactory receptor neuron Pages: 17 (4661 words) Published: October 1, 2013
Each hemisphere of the brain also has a cingulate gyrus  part of the limbic system Limbic system  includes cingulate gyrus, amygdala, and hippocampus Emotion, learning, and memory
Cerebral cortex  consists of sensory, motor, and association areas Association areas integrate sensory data into perception
Motor outputs control target tissues
The noradrenergic system originates from the locus coeruleus in the pons Its axons terminate through the brain  disseminates noradrenaline throughout the entirety of brain Stress & panic
The serotonergic system originates from the raphe nuclei on the brain stem midline (pyramid) Axons also terminate throughout the entirety of the brain
Aggression, locomotion, sleep-wake cycles
The dopaminergic system originate from the substantia nigra and ventral tegmentum in the midbrain Axons terminate in the cerebral cortex and limbic system
Motor control and reward
The cholinergic system originates from the pons, midbrain, and base of the cerebrum Transmitter  acetylcholine
Axons terminate in the cerebrum, hippocampus, and thalamus
Learning, memory, transmitting sensory data through thalamus Receptors and Neurons
Receptors are cells that convert stimulus energy into electrical signals  conversion of one medium to another is called transduction They first convert stimulus energy into graded changes in membrane potential For instance, it may fire APs or release neurotransmitters

Each receptor has an adequate stimulus  the form of stimulus that it is most responsive to Receptors can be classified according to their adequate stimuli: Chemoreceptors  oxygen, pH, glucose
Mechanoreceptors  mechanical energy such as vibration, gravity, acceleration Thermoreceptors  temperature
Photoreceptors  light
Simple receptors  neurons with free nerve endings
These sense temperature and noxious stimuli
Complex neural receptors are neurons with their endings in connective-tissue capsules E.g. Pacinian corpuscle  senses touch
Consists of nerve ending encased in multiple layers of connective tissue Most special sense receptors are cells that release neurotransmitter onto sensory neurons Transduction involves ion channels in the receptor’s membrane Stimulus modulates ion channels directly or through a second messenger Channel is opened  Na and other cations depolarize membrane Example: light closes cation channels  hyperpolarizes the membrane Receptors have thresholds  minimum stimulus strength that will activate it Perceptual threshold differs  minimum stimulus strength for you to be aware of it Can be modulated based on attention and other things

Sensory systems involve series of neurons
First neurons  primary sensory neurons
Primary sensory neurons synapse onto secondary sensory neurons  tertiary… At each stage, presynaptic neurons may provide input to postsynaptic neurons, called convergence Allows combination of information from many receptors

Sensory systems carry information about many aspects of the stimulus Stimulus modality light, sound, touch, etc.
Sensory systems indicate this modality by labelled lines  activity on neurons on a specific pathway is interpreted by the CNS to be a specific modality of stimulus Coding Location
Stimulus location is represented in two ways:
Auditory system  differences in loudness and timing between ears Visual and somatic (voluntary control)  receptive fields
Any somatic sensory or visual neuron has a receptive field  region where stimuli affect the neuron’s activity Secondary cells that get input from less primary cells have smaller receptive fields  allow for greater 2-point discrimination Multiple sensory cells may converge on a single one  large receptive field because all of the stimulus will go to one secondary neuron  poor 2-point discrimination Lateral inhibition  increases localization

The primary cells located slightly away from the point of stimulus may detect it The primary cell with the greatest...
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