Lecture 7 & 8 - Simple Circuits, Vision Flashcards
Describe convergent pathways of neurons, and give an example in the body
This is when many neurons fire onto on target cell
Describe divergent pathways of neurons and give an example in the body
This is one when neuron splits at the axons to interact with many target cells.
This happens with lower motor neurons, which split to active many muscle fibres making up a motor unit
Which part of the neuron receives input?
The dendrites
Distinguish IPSPs and EPSPs
EPSPs: when excitatory cells input to a neuron, they bring about the depolarisation of a small segment of the dendrite on the cell body. These will add together to trigger an action potential
IPSPs: when inhibitory cells input onto a neuron, they bring about a hyper polarisation of a region of the cell body. This makes it more unlikely that an action potential will fire
The axon hillock determines whether or not an action potential will fire based on the balance between …
IPSPs and EPSPs
What sort of input will have a greater impact on the likelyhood of an AP firing?
One near the axon hillock
What happens once an action potential reaches the axon terminal?
There is no more depolarisation at the terminal because there are no more sodium channels in the membrane
- Voltage gated calcium channels open, and calcium rushes into the cell
- Synaptic vesicles fuse with the membrane, releasing neurotransmitters into the synaptic cleft
- These neuro transmitters interact with receptors on the post-synaptic membrane
Why is time important when considering graded potentials?
If they occur in quick succession they will summate and cause an action potential to fire
If they are more spread out, they won’t summate and won’t get the axon hillock to threshold
How will a strong neurotransmitter stimulus alter the firing of action potentials compared to a weak stimulus?
It will not alter the magnitude of the action potential, only the firing rate
What is pre synaptic inhibition?
An inhibitory neuron inhibits one of the axon terminals just before it synapses
This selectively inhibits one of the targets
What is post-synaptic inhibition?
This is when an inhibitory cell inputs onto the cell body, inhibiting the entire cell.
All targets of this cell are now inhibited
… are variant and … are invariant
- Graded potentials
2. Action potentials
Differentiate between conscious sensing and unconscious sensing
Give some examples of each
Conscious: we know that we are perceiving these things
Vision, pain, heat, taste, smell
Unconscious: we don’t perceive them
Blood pressure, heart rate, osmolarity
Differentiate between senses that use neurons to sense the environment and senses that use specialised cells
Neurons: smell, ORC
Specialised cells: vision, hearing, mechanoreptioon
What are the four classes of receptor?
Thermoreceptor
Mechanoreceptor
Chemoreceptors
Photoreceptor
