Nerve Physiology Flashcards
What are the 3 ways cells communicate?
- Gap junctions
- Contact- dependent signals
- Autocrine/Paracrine signals
What is a gap junction?
A cytoplasmic connection between adjacent cells
What is a contact-dependent signal?
A communication that reguires interaction between 2 membrane molecules on 2 cells
What is an autocrine signal?
A signal that acts on the same cell that created it
What is a paracrine signal?
Signals secreted by one cell and diffuses to adjacent ones
What are neurotransmitters?
Chemicals secreted by neurons that diffuse along a small gap to the target cell
What are the 3 functional regions of a neuron?
- Dendrites
- Cell body
- Axon
What part of a neuron recieves the signal?
The dendrite
What part of a neuron sends the signal?
axon
What is the function of the cell body in a neuron?
- Integrates signals from dendrites
- Controls protein synthesis and cell metabolism
What is the axon hillock and its purpose?
- start of axon
- recieves signal from cell body
What is the role of the axon?
- transmitts binary signals
Where are neurotransmitters released?
Parasynaptic terminals
What is the structure of a dendrite?
- Excessive branching
- Receptors on post-synaptic membrane
What is the function of the dendrites?
- Recieve inputs from other nuerons
- Transmit signals to cell body
What is a membrane potential?
potential formed between extra cellular and cytoplasmic sides of membrane.
How do membranes move across a membrane potential?
Via a permeable membrane.
Why may a particle not follow the concentration gradient?
There may be a concentration gradient but also a charge gradient. The latter cancels out the former
What happens when a membrane potential in a neuron reaches a critical level?
A spike, or action potential, is generated.
What is the refractory period?
Time after a channel closes and membrane potential is overshot till a gate can reopen
Why do neurons only propogate information in one direction?
Action potential can only transfer to neighbouring particles and the previous will be in their refractory period, causing the AP to move forward
How do action potentials lead to the release of neurotransmitters?
- The AP depolarises the axon terminal
- This open the voltage-gated channel, allowing Ca to enter
- Ca triggers synaptic vesicle to empty its content (neurotransmitters)
- Neurotransmitters diffuse to post-synaptic cell
What is a major difference between presynaptic and postsynaptic potentials?
Postsynaptive are not binary
How are neuron firing rates related to blood vessel behaviour?
A faster firing rate = more AP which leads to more transmitters.
More transmitters will cause blood vessel to constrict
What is the difference between a slowly adpating receptor and a rapidly adapting receptor?
- Slowly: fire AP continuously while stimuli occuring
- Fastly: only fire AP at onset/offset
What is this?
Pacinian corpuscle
What is the structure of a pacinian corpuscle?
- one nerve surrounded by lamelle
Why are pacinian corpuscles rapidly adapting?
- Very sensitive, respond to small micro-level changes
- Respond to high frequency vibration
- Distort and ‘absorb’ force if stimulation sustained
What type of neuronal network is this?
Divergent
What type of neuronal network is this?
convergent
Explain what is happening here
- 3 presynaptic axons, each has insufficient graded potential
- When they enter the trigger zone, the potentials sum and now it is a sufficient value
- AP can now be generated
What type of spatial summation interaction is this?
negative
