Introduction and The Central Nervous System Flashcards
What happens during summation?
Summation involves adding the effects of a number of nerve transmissions together in order to produce an impulse in the post-synaptic neuron. The excitatory and inhibitory influences are summed, if the net effect on the post synaptic neuron is inhibitory, the neuron will be less likely to ‘fire’ and if the net effect is excitatory, the neuron will be more likely to ‘fire’.
What do Excitatory NTs do?
Excitatory NTs increase the likelihood of an action potential arriving in the post synaptic neuron.
What do Inhibitory NTs do?
Inhibitory NTs reduce the likelihood of an action potential arriving in the post synaptic neuron.
When NTs ‘unlock’ the ion channels, what happens? What does this cause?
Ions then flow through the channel into the neuron along their specific pathways. This flooding of ions can cause a ‘potential’ in the dendrites. These potentials can be excitatory or inhibitory.
What is the relationship between NTs and ion channels similar to?
Similar to the ‘lock and key theory’ with enzymes.
What is specific about ion channels and thus NTs?
Only certain neurotransmitters can “unlock” an ion channel in certain receptors in the post-synaptic neuron.
Outline the process of synaptic transmission.
Action Potential/ electrical impulse travels down the presynaptic neuron.
Stimulates the vesicles (containing NTs) to move down towards the terminal of the cell.
The vesicles fuse with the membrane of the presynaptic neuron and the NTs diffuse into the synaptic fluid/ cleft.
NTs then diffuse across the synapse to the receptor sites on the postsynaptic neuron, where they will bind to the complementary sites.
An action potential may or may not be initiated in the post synaptic neuron.
Inhibitory NTs reduce the likelihood of an action potential arriving in the post synaptic neuron, whereas excitatory NTs increase the likelihood of an action potential arriving in the post synaptic neuron.
Finally, summation occurs, distributing the combined effect of the action potential on the post synaptic neuron.
If a threshold is reached, then a new action potential will form in the post synaptic neuron.
NTs can diffuse back into the synapse, broken down by enzymes or can be re-up taken by the presynaptic neuron.
What is a motor neuron?
Motor neuron: carry signals from the CNS which helps both organs, including glands and muscles, to function.
What is a relay neuron?
Relay neuron: carry messages from one part of the CNS to another. They connect with sensory neurone.
What is a sensory neuron?
Sensory neuron: tells the rest of the brain about the external and internal environment by processing information from any of the five senses.
What are the 3 types of neuron?
The 3 types of neuron are: sensory, relay, and motor.
State 3 characteristics and an example of the parasympathetic nervous system’s processes.
Rest and digest.
Body tries to conserve and store resources.
Opposite effect to sympathetic.
E.g. store glucose, decrease heart rate.
State 2 characteristics and an example of the sympathetic nervous system’s processes.
Fight or flight. Activates internal organs in situations that need arousal and energy. E.g. pupil dilation, increased heart rate.
What does the parasympathetic division of the CNS deal with?
Parasympathetic division: homeostasis.
Outline the Somatic NS
Somatic nervous system: comprised of sensory and moor pathways. Conscious control of smooth muscle.
