the cells of the nervous system and neurotransmitters at synapses 3.4

Question 1

what is the nervous system consist of

Answer 1

a complex network of nerve cells called neurons

Question 2

neurons structure

Answer 2

have a nucleus, cytoplasm and cell membrane (cell body) and have long fibres called dendrites and axons

Question 3

what do the dendrites and axons on neurons allow

Answer 3

allow the neurons to carry electrical impulses

Question 4

where do dendrites carry electrical impulses

Answer 4

towards the cell body

Question 5

where do axons carry electrical impulses

Answer 5

away from the cell body

Question 6

the three types of neurons

Answer 6

sensory, inter and motor

Question 7

sensory neuron structure

Answer 7

• has dendrites in contact with sense organ receptors
• dendrites merge to form a dendron which carries impulses to the cell body
• has a short axon which forms connections with inter neurons

Question 8

inter neuron structure

Answer 8

• connects sensory neurons to motor neurons
• very short and contained inside the CNS
• many dendrites which form many complex connections

Question 9

motor neuron structure

Answer 9

• short dendrites which receive impulses from inter neurons
• long myelinated axon which carries nerve impulses to effectors

Question 10

what surrounds axons

Answer 10

a myelin sheath

Question 11

what does the myelin sheath contain

Answer 11

a fatty material which insulates the axon and increases the speed of impulse conduction

Question 12

what do glial cells provide

Answer 12

physical support for neurons and produce the myelin sheath

Question 13

myelination

Answer 13

the development of myelin sheath by glial cells which continues from birth to adolescence and as a result responses to stimuli in the first two years of life are not as rapid or coordinated as those of an older child or adult

Question 14

how can the myelin sheath be destroyed

Answer 14

certain disease causing loss of coordination example multiple sclerosis

Question 15

where do nerves connect with other nerves

Answer 15

synapse cleft

Question 16

neurons before the synaptic cleft

Answer 16

presynaptic neuron

Question 17

neuron after the synaptic cleft

Answer 17

postsynaptic neuron

Question 18

what do neurotransmitters do

Answer 18

relay impulses across the synaptic cleft

Question 19

where are neurotransmitters

Answer 19

are stored in the vesicles in the axon ending of the presynaptic neuron and are released into the cleft on arrival and diffuse across the cleft and binds to receptors on the membrane of the postsynaptic neuron

Question 20

why should you remove neurotransmitters

Answer 20

must rapidly remove as soon as the impulse has been transmitted to prevent the continuous stimulation of postsynaptic neurons

Question 21

how to remove neurotransmitters

Answer 21

• enzyme degradation and reabsorption of neurotransmitters by presynaptic neurons
• re uptake of neurotransmitters by presynaptic neurons

Question 22

what determines what signal is detected

Answer 22

the type of receptor that the neurotransmitter binds to

Question 23

types of signals

Answer 23

excitatory or inhibitory

Question 24

excitatory signals

Answer 24

causes an increase in action example causes muscle cells to contract

Question 25

inhibitory signals

Answer 25

causes a decrease in action example slow heart rate

Question 26

how to reach the threshold on the postsynaptic membrane

Answer 26

a minimum number of neurotransmitter molecules must attach to receptors

Question 27

what happens once the threshold on the postsynaptic membrane is reached

Answer 27

the impulse is transmitted

Question 28

when do synapses filter out weak stimuli

Answer 28

when there’s insufficient secretion of neurotransmitters

Question 29

summation

Answer 29

a series of weak stimuli can release enough neurotransmitters to trigger an impulse and converging pathways can release enough neurotransmitter molecules to reach threshold and trigger impulse

Question 30

endorphins

Answer 30

neurotransmitters that stimulate neurons involved in reducing the intensity of pain

Question 31

what are increased levels of endorphins linked to

Answer 31

feelings of pleasure obtained from activities such as eating, sex and prolonged exercise

Question 32

when does endorphin production increase

Answer 32

in response to severe injury, prolonged and continuous exercise, stress or certain foods

Question 33

dopamine

Answer 33

a neurotransmitter that induces feelings of pleasure by reinforcing particular behaviour by activating a reward pathway in the brain

Question 34

what does the reward pathway involve

Answer 34

neurons which secrete a response to dopamine

Question 35

when is dopamine activated

Answer 35

when an individual is engaged in behaviour which is beneficial to them example eating when hungry

Question 36

what is used to treat conditions relating neurotransmitters

Answer 36

drugs which many are agnostic or antagonistic

Question 37

antagonistic drugs

Answer 37

chemicals that bind to specific receptors blocking the action of a neurotransmitter at a synapse

Question 38

agnostic drugs

Answer 38

chemicals which bind to and stimulate specific receptors mimicking the action of a neurotransmitter at a synapse

Question 39

how do other drugs work

Answer 39

by inhibiting the enzymes that degrade neurotransmitters or by inhibiting the re uptake of the neurotransmitter at the synapse causing an enhanced effect

Question 40

how do recreational drugs act

Answer 40

agnostic or antagonistic

Question 41

how do recreational drugs interact with neurotransmitters

Answer 41

- stimulate the release of neurotransmitters - mimic their actions (agnostics) - block their binding (antagonists) - inhibit their enzyme degradation - inhibit their reuptake

Question 42

how can recreational drugs affect neurotransmitters

Answer 42

they affect neurotransmitters in the reward pathway of the brain and alter a persons neurochemistry which changes their mood, cognition, perception and behaviour

Question 43

what causes drug addiction

Answer 43

the repeated use of drugs which act as antagonists

Question 44

how do antagonistic drugs cause drug addiction

Answer 44

they block specific receptors causing the nervous system to increase both the number and sensitivity of these receptors and the sensitisation leads to addiction

Question 45

what causes drug tolerance

Answer 45

repeated use of drugs that act as agnostics

Question 46

how do agnostic drugs cause drug tolerance

Answer 46

stimulate specific receptors causing the nervous system to decrease both the number and sensitivity of these receptors and this desensitisation leads to drug tolerance