Neurons and synpatic transmission Flashcards
Overview of neurons
100 billion in human nervous system
80% located in the brain
Electrical and chemical transmission
Primary means of communication for nervous system.
What do neuron do?
In resting state = negatively charged cell
When neuron is activated —-> the inside becomes positively charged.
Induces an action potential
Descibe a sensory neuron
Carry messages from peripheral nervous system to the central nervous system.
Found in receptors (skin/eyes)
Carry impulses to spinal cord and brain
Translated into sensations such as touch.
Describe motor neuron
Found in CNS
Connects CNS to effectors (muscles/glands)
=control of movements
When motor neurone stimulated —->release neurotransmitters which bind to receptors on the muscle
Triggers response —> movement
Describe relay neurons
Found between sensory input and motor output
Neurons mainly in brain and spinal cord allow sensory and motor neurons to communicate.
What is the structure of a neuron?
Dendrites = branch-like structures
+Receive nerve impulses from neighbouring receptors
+Carry signal to cell body.
Cell body = nucleus which contains genetic information
Axon = carries impulse in the form of electrical signals known as action potential towards axon terminal
Myelin sheath/Nodes of Ranvier = speed up transmission of impulses by forcing impulses to jump over gaps.
What is synaptic transmission?
Neurons communicate in groups —> neural networks
Each neuron separated by gap called synapse.
Information within neurons = electrically transmitted
Information between neurons = chemically transmitted
Describe process of synaptic transmission
Impulse arrives at presynaptic neuron.
Coverts electrical impulse into chemical messengers —–> neurotransmitters released from vesicles
Synaptic vesicles hold neurotransmitters
Neurotransmitters diffuse into a synapse.
Bind to receptor sites on postsynaptic neuron
Chemical messengers converted back to electrical impulses
Neurotransmitters broken down and reabsorbed into presynaptic neuron
ONE DIRECTION
What are neurotransmitters?
Chemicals that diffuse into synapse into next neuron in chain
Always a perfect fit (think lock and key)
Have specialised functions —> acetylcholine = muscle contraction
Examples of neurotransmitters + their functions.
Serotonin —> happiness/satisfaction
Dopamine —>love/passion
Acetylcholine —> learning/dreaming/memory
What do excitatory neurotransmitters do?
Some neurotransmitters cause other neurons to be positively charged
——> neurons more likely to be fired
E.g: adrenaline
What do inhibitory neurotransmitters do?
Some neurotransmitters cause other neurons to be negatively charged.
——–> Neurons more likely to be fired
E.g: serotonin
Describe the process summation.
Majority rules
If net effect is positive —-> more likely to fire neurons.
Action potential triggered if sum of excitatory/inhibitory signals reaches a particular threshold.
