Jette Hannibal - Inthinking The nervous system NS: gathers and processes information, produces responses to stimuli, coordinates the workings of different

Jette Hannibal - Inthinking

The nervous system

NS: gathers and processes information, produces responses to stimuli, coordinates the workings of different cells

CNS (brain + spinal cord): receives, processes, interprets, and stores incoming sensory information (e.g. Taste, state of internal organs)

PNS: deals with input and output of CNS through sensory and motor neurons.


The nervous system

Millions of neurons in different sizes and shapes organized in a network for transmission of information.

Communication between neurons: electric conduction and chemical transmission

A large concentration of neurons in the brain and the spinal cord. 80% are found in the brain’s Cerebral cortex

Neurons: basic structural unit of NS


Structure of neurons

Cell body or nucleus (contains DNA) Dendrites: information transmission Axons: the cell body. Terminal buttons: storage of

neurotransmitters. Synaptic gap: between dendrites and

terminal buttons. Where neurotransmitters “pass” information from neuron to neuron.


Neuron


Neuronal communication

Within neurons: Action potential Between neurons: Synaptic transmission

of neurotransmitters


Action potential

Electro-chemical messages AP occurs when a neuron sends

information down an axon AP caused by an exchange of Sodium and

Potassium ions across the neural membrane


Neurotransmitters

Chemical messengers from neuron to neuron.

Messages may also travel from neurons to to muscles and organs in the body, such as lungs or the intestines.


Synaptic gap

Synaptic vesicles with neurotransmitters at one side of the gap (terminal buttons): pre-synaptic gap. Like “keys”

Receptor sites for neurotransmitters (like locks) at the other side of the gap: post-synaptic gap

1/10000 of a second to travel across the synaptic gap


Brain, neurons, neurotransmitters – how it works

http://www.youtube.com/watch?v=haNoq8UbSyc


Neurotransmitters

Produced in the terminal buttons and diffused across the synaptic gap to bind to receptor sites.

The neuron on the postsynaptic side of the gap more or less likely to fire as a result of synaptic transmission.

Psychoactive drugs can change properties of neurotransmitter release, neurotransmitter reuptake and the availability of receptor binding sites.


Neurotransmitter processes

Excitatory: increases the frequency of action potential

Inhibitory: decreases the frequency of action potential

De-activation: effect of neurotransmitter stopped (destroyed by special enzyme)

Re-uptake: reabsorbed by the terminal buttons. Drugs can inhibit re-uptake so that the

neurotransmitter remains longer in the synaptic gap


Brief intro to principles of neurotransmission

Click here to see how neurotransmission works.


Examples of neurotransmitters

Dopamine: (inhibitory) Controls arousal levels in the brain; vital for physical motivation (e.g. associated with craving in addiction)

Serotonin: (inhibitory) Controls mood and anxiety levels High levels of serotonin are associated with optimism.

Acetylcholine (ACh): (excitatory) Controls activity in the brain connected with attention, learning and memory

Noradrenaline: (excitatory) involved in mental arousal and elevated mood


Dopamine and serotonin


The reward pathway - dopamine

Stimulation of the reward center is linked to release of dopamine

Rats will continuously press a lever that gives a small electrical stimulation to the pleasure center

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Jette Hannibal - Inthinking The nervous system NS: gathers and processes information, produces responses to stimuli, coordinates the workings of different