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| nerves cells which transmit nerve impulses |
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| The three types of neurons are: |
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| All neurons are made up of |
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| a cell body, one axon and several dendrites |
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| The cell body of a neuron contains |
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| the nucleus and most of the cytoplasm |
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| control centre of the cell’s metabolism and contains ribosomes |
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| The axon is a single nerve fibre that |
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| carries nerve impulses away from the cell body to the next neuron |
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| The direction of a nerve impulse is always |
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| dendrites cell body axon |
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| a myelin sheath which insulates it |
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| Gaps in the myelin sheath are called |
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| The presence of the myelin sheath |
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| increases the speed impulses can be transmitted |
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| Myelination continues from |
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| Diseases that destroy the myelin sheath include |
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| Polio, Multiple Sclerosis, Tay-Sachs disease |
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| physically support neurons and produce the myelin sheath |
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Definition
a tiny gap between the axon of one
neuron and the dendrite of another which contains sufficient neurotransmitter to continue the nerve impulse |
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Definition
| is the nerve cell before the synaptic cleft |
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| Neurons connect with other neurons, muscle fibres and endocrine glands |
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| are chemical messages relayed across synaptic clefts from neuron to neuron |
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| Examples of neurotransmitters are |
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| Acetylcholine and Norepinephrine |
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| Neurotranmitters are stored in |
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| vesicles before their release (pre-synaptic neuron) |
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| receptors on the nerve endings once they have diffused across the cleft |
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| Acetylcholine released between a motor neuron and a skeletal muscle fibre |
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| binds to receptors that have an excitatory effect on the muscle, making it contract |
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| Acetylcholine released between a motor neuron and a heart muscle fibre |
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| binds to receptors which have an inhibitory effect, reducing rate and strength of the muscle contraction |
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| Neurotransmitters can be removed |
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Definition
| by enzyme degradation and re-uptake |
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Definition
| a series of weak stimuli trigger enough neurotransmitter to fire an impulse |
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| Converging neural pathways increase sensitivity to excitatory and inhibitory signals by |
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| impulses from several sources meeting at a common point |
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| Diverging neural pathways influence several neurons |
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| at the same time by branching out from a common point |
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| Reverberating pathway neurons later in the pathway |
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| synapse with earlier ones, sending the impulse back through the circuit |
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| Plasticity of response is |
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Definition
| the brain cells’ ability to become altered as a result of new environmental experiences |
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Definition
| new neural pathways are developed |
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| Endorphins are neurotransmitters that |
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| act as natural pain killers |
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| Endorphin production increases in response to |
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| severe injury, prolonged exercise, physical and emotional stress and certain food stuff |
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| Increased levels of endorphins may bring about |
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| feelings of euphoria, regulate appetite and release sex hormones |
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| feeling of pleasure and rewards particular behaviour in the reward pathway |
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| Neurotransmitter related disorders |
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Definition
| include Alzheimer’s and Parkinson’s diseases |
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| Neurotransmitter-related disorders can be treated by |
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Definition
| agonists, antagonists and inhibitors |
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Definition
| and stimulate receptors mimicking the neurotransmitter |
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| specific receptors blocking the action of the neurotransmitter |
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Definition
| inhibit the enzymes which degrade the neurotransmitters or inhibit re-uptake |
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| Alzheimer’s disease is treated using |
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| cholinesterase inhibitors |
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| Parkinson’s disease is treated by using |
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| L-dopa, agonists that mimic dopamine |
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| Recreational drugs affect the transmission of nerve impulses |
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Definition
| in the reward circuit of the brain. |
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| Drug tolerance is said to have built up when |
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| reaction to a drug has decreased intensity even though the drug’s concentration remains the same |
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