Chapter 1 - Sensory Neuroscience and the Biology of Perception Flashcards
Important physiologists
Darwin - theory of evolution - continuity in the structure and function of senses and nervous systems of model organisms and humans
Muller - doctrine of specific nerve energies - only aware of activity in our nerves and are not aware of the world itself
Helmholtz - first to measure speed of neurons when they transmit signals
Ramon y Cajal - neurons are discrete entitites that do not acutally touch another
Sherrington - term synapse
Lowei - first neurotransmitter
Hodgkin - ionic basis of the resiting potential and AP
Efferent and AFFERENT information
Afferent - SENSORY information going toward the brain from external environment
Efferent - MOTOR components going away from the CNS
- contains visceral (involuntary) and somatic (voluntary)
Transduction
Transduction - conversion of external energy into electrical signal (receptor potential) through opening and closing of ion channels
How do receptor cells sense environmental signals
- Proteins on the plasma membrane respond to environmental signals
Acid binds to the outside of a protein , the ligan binds and it causes the gland to open allwing for ions to pass through
Ligan binds to receptor in plasma membrane but causes a chain reaction it causes activiation in G protein which acticates other molecules which either open or close ion chanells
In plasma membrane, linked to cytoskeloton of cell, when cell is pressed it is opened allowing cells to flow
This is whats going to cause a cell to become more positive or depolarized (since cells are charged ions)
The change in membrane potential of sensory receptors
When you touch the cell it rises the resting potential
from 60 then when you touch the external stimulus more positive ions come into the cell making it more positive and the membranes potential rises to a –52 = receptor potential
Receptor potential – neuron is responding to external stimulus and converting it t a biological signal
Depolarization
- neuron coding to identify the stimulus that gets neurons to fire
How do signals pass from one neuron
- relayed through synaptic transmission
- neurotransmitter - chemical messenger packaged into vesicles that bind to specific receptors on posy-synaptic cells
- if large enough = AP
- they move unilaterally
Receptors associated with synaptic transmission
- specialized proteins with high specificity for neurotransmitters
- activation changes directly or indirectly the membrane potential of postsynaptic cell
Steps of synaptic transmission:
- AP arrives at terminal
- depolarization opens voltage gated CA chanells
- Ca entry triggers vesicle fusion
- neurotransmitte diffuses across synaptic cleft and binds to receptors
- response in postsynaptic cell (usually includes changes in NA, K, Cl or Ca permeability)
- broken down by enzymes
- reuptake into presynaptic terminal, or by surrounding glial cells
- diffusion out of synaptic cleft
Binding of neurotransmitter to post-synaptic receptors causes the synaptic potential which….
causes ESP or ISP
ESP - bring membane potential above threshold - cause firing
ISP - bring membrane potential below threshold - inhibit firing
Unique sensory neuron structures
Bipolar - generally sensory, cell body in the middlle
Pseudo-unipolar - generally sensory, contains peripheral axon (AP can be generated here)
Multipolar - cell body is with dendrites, generally motor and internueons, most common
Principles of sensory coding
Stim location - Info from specific area gets generated there – there is only one area
Retina, skin, - information where that signal is – you touch the area and that same neuron goes towards the brain – receptive field
Intensity - How strong or how weak – amount of pressure needed to activate neuron is related to action potential
Weak touch = smaller receptive potential and initiates low frequency in action potential (vice versa) - rate code
We know its stronger by more frequency
Amount of pressure needed to activate neuron
All or none
Duration - How long is a stimulus present
Neurons will continue to fire until you remove the sensation
Some may stop quickly for example if you move your finger
Modality - What exactly is this sensory info telling us about
Temperature, pain, etc.
Ex) ouch receptors aren’t going to give us info about vision
Axes of human nervous system
- CNS - spinal cord and brain
- long axis of CNS has bend
- forebrain tilted forward
- important to know when talking about sections
Anatomical functional brain regions
Divided into 4 lobes
- gyri - crests of folded cortical tissue
- sulci - grooves that divide gyri
Cerebral cortex
- all sensory inputs first goes to primary receiving areas
- then info goes to cortical areas (association areas) - more than one sense is polysensory
- operations that occur here produce perceptual experiences
