KA4- Cells Of The Nervous System And Neurotransmitters At Synapses Flashcards
Structure of neurons
Dendrites
Cell body
Axons
Dendrite
Receives neurotransmitters from other neurons and signals from sense organs
Cell body
Contains nucleus, cytoplasm, ribosomes etc
Control centre of cells metabolism
Axon
Carries nerve impulses from the cell body to the next neuron
Direction of nerve impulse
Dendrite —> cell body —> axon
Myelin sheath
Axons are surrounded by a myelin sheath which insulates the axon and increases the speed of impulse conduction
Gaps in the myelin sheath
Nodes
Myelination
continues from birth to adolescence so responses to stimuli in the first two years of life are not as rapid or co-ordinated as those of an older child or adult
Destruction of myelin sheath
Certain diseases destroy the myelin sheath causing a loss of of coordination
Glial cells
Produce the myelin sheath and physically support neurons
Chemical transmission at the synapse by neurotransmitters
Vesicles
Synaptic cleft
Receptors
Presynaptic neuron
Neuron carrying signal before the synapse
Synapse is
the tiny region into which the axon end of one neuron releases its neurotransmitters
Vesicles containing neurotransmitters
occur only on one side of synapse to ensure nerve impulse is transmitted in one direction
Synapses can
filter out weak stimuli arising from insufficient secretion of neurotransmitters
Convergent neural pathways
can release enough neurotransmitter molecules to reach threshold and trigger an impulse
The function of endorphins
neurotransmitters that stimulate neurons involved in reducing the intensity of pain
Endorphin production increase in response to
Several injury
Prolonged and continuous exercise
Stress
Certain foods
Increased levels of endorphins are linked to
the feelings of pleasure obtained from activities such as eating, sex and prolonged exercises
The function of dopamine
a neurotransmitter that induces feelings of pleasure and reinforces particular behaviour by activating the reward pathway in the brain
The reward pathway involves
neurons which secrete or respond to dopamine
The reward pathway is activated when
an individual engages in a behaviour that is beneficial to them, for example eating when hungry
Drugs which are used to treat neurotransmitter-related disorders
Agonists
Antagonists
Inhibitors of neurotransmitter enzymes
Reuptake inhibitor
Agonists
chemicals that bind to and stimulate specific receptors mimicking the action of a neurotransmitter at a synapse
Antagonists
chemicals that bind to specific receptors blocking the action of a neurotransmitter at a synapse
Inhibitors of neurotransmitter enzymes
Inhibit the enzymes that degrade the neurotransmitters (in a synaptic cleft)
Reuptake inhibitor
Inhibit reuptake of neurotransmitter at the synapse causing an enhanced effect
Recreational drugs
can also act as agonists or antagonists
affected neurotransmission (many in the reward pathway) at synapses in the brain altering an individuals mood, cognition, perception and behaviour
Drug addiction
Caused by repeated use of drugs that act as antagonists
Antagonists block specific receptors causing the nervous system to increase both the number and sensitivity to these receptors
Sensitisation (antagonists)
leads to addiction where the individual craves more of the drug.
Drug tolerance
Caused by the repeated use of drugs that act as agonists
Agonists stimulate specific receptors causing the nervous system to decrease both the number and sensitivity of these receptors
Desensitisation (agonists)
Leads to drug tolerance where the individual must take more of the drug to get an effect
