3.4- cells of the nervous system & neurotransmitters at synapses

Question 1

2 types of nerve cells in the nervous system

Answer 1

neurons

glial cells

Question 2

what do neurons do?

Answer 2

receive and transmit electrical signals

Question 3

3 things all neurons have

Answer 3

cell body

one axon

several dendrites

Question 4

what are dendrites?

Answer 4

thread like extensions of the cytoplasm which are often referred to as nerve fibres

Question 5

what do dendrites do?

Answer 5

receive nerve impulses and pass them towards a cell body

Question 6

what is the cell body?

Answer 6

contains the nucleus and most of the cytoplasm

Question 7

what is an axon and what do they do?

Answer 7

single nerve fibre that carries nerve impulses away from the cell body

Question 8

direction of nerve impulses

Answer 8

dendrites - cell body - axon

Question 9

where are myelin sheath found?

Answer 9

surrounding axons

Question 10

2 functions of myelin sheath

Answer 10

insulate axon by surrounding them

increases the speed of impulse conduction

Question 11

what is the effect of myelin sheath’s presence?

Answer 11

greatly increases the speed that impulses can be transmitted along the axon of a neuron

Question 12

when does myelination take place?

Answer 12

continues from birth to adolescence

Question 13

what effect does myelination have on responses to stimuli?

Answer 13

they aren’t as rapid or co-ordinated in the first 2 years as those of an older child or adult

Question 14

what can happen to the myelin sheath in some diseases?

Answer 14

becomes damaged and destroyed causing a loss of muscular co-ordination

Question 15

what do glial cells not do?

Answer 15

glial cells do not transmit nerve impulses

Question 16

function of glial cells

Answer 16

some are responsible for the production of the myelin sheath

Question 17

what are glial cells essential in?

Answer 17

glial cells are essential in providing neurons with physical support

Question 18

what is a synapse?

Answer 18

gap between the end of one neuron and the beginning of another

Question 19

how are synapses separated?

Answer 19

by a synaptic cleft

Question 20

what do neurons connect with and where?

Answer 20

neurons connect with muscle fibres and endocrine gland cells at the synaptic cleft

Question 21

what is the nerve cells before and after the synaptic cleft called?

Answer 21

presynaptic cleft

postsynaptic cleft

Question 22

function of neurotransmitters on the synaptic cleft

Answer 22

neurotransmitters on the synaptic cleft relay impulses across the synaptic cleft

Question 23

4 steps in the action of neurotransmitters

Answer 23

neurotransmitters are stored in the vesicles in the axon endings of the presynaptic cleft

when a nerve impulse passes through the presynaptic neuron, it reaches the synaptic terminal and stimulates the vesicles

this causes the vesicles to discharge the neurotransmitters into the synaptic cleft

neurotransmitters then diffuse across the synaptic cleft and bind to receptors on the postsynaptic neurones membrane

Question 24

where are neurotransmitters stored?

Answer 24

neurotransmitters stored in the vesicles in the axon endings of the presynaptic cleft

Question 25

what does the neurotransmitter **acetylcholine** do?

Answer 25

acetylcholine binds to receptors causing membrane to open which allows an increased flow of ions through the membrane

Question 26

**3 steps in the removal of neurotransmitters**

Answer 26

neurotransmitters are removed from the synaptic cleft immediately following the passing of any impulse if the neurotransmitter was left in the synaptic cleft, it would lead to continuous stimulation of the postsynaptic cleft the system would not be able to responds to new signals making precise control impossible

Question 27

2 ways **removal of neurotransmitters** from the **synaptic cleft** is **achieved**

Answer 27

enzyme degradation reuptake of neurotransmitters

Question 28

what happens during **enzyme degradation**?

Answer 28

some neurotransmitters are broken down by enzymes non-active products are reabsorbed by the presynaptic membrane

Question 29

what happens in the **reuptake of neurotransmitters**?

Answer 29

in the reuptake of neurotransmitters they are taken back up directly by the presynaptic membrane

Question 30

what 2 things can **signals** be?

Answer 30

excitatory inhibitory

Question 31

how is a signal determined to be **excitatory** or **inhibitory**?

Answer 31

the type of receptor involved in the bind to a neurotransmitter

Question 32

**2 steps of filtering out weak stimuli**

Answer 32

for a nerve impulse to be transmitted across a synapse and through the postsynaptic neuron it must first bring about the release of a certain minimum number of neurotransmitters this number is needed to affect a sufficient number of receptor sites on the postsynaptic neurons membrane

Question 33

what it is **called** when the certain number of neurotransmitter molecules needed for a nerve impulse to be transmitted is **achieved**?

Answer 33

reaching the membranes threshold

Question 34

how do **synapses filter out weak stimuli**?

Answer 34

from the insufficient secretion of neurotransmitters

Question 35

what is **summation** and what **happens**?

Answer 35

summation is when several weak stimuli reach a target neuron together and their effect is summated an impulse can be passed on

Question 36

example of **summation**

Answer 36

converging neural pathways can release enough neurotransmitter molecules to reach the threshold and trigger an impulse

Question 37

what are **endorphins** and how do they **work**?

Answer 37

chemicals that function like neurotransmitters and act as natural painkillers do this by combining with receptors at synapses and blocking the transmission of pain signals

Question 38

**where** are endorphins produced?

Answer 38

hypothalamus

Question 39

4 things that **increase production level** of endorphins

Answer 39

physical and emotional stress severe injury lengthy periods of vigorous exercise certain foods such as chocolate

Question 40

3 things that **increases** **level** of endorphins

Answer 40

prolonged exercise sexual activity eating favourite foods

Question 41

2 effects of **dopamine**

Answer 41

induces feelings of pleasure reinforces particular behaviour by activating the reward pathway in the brain

Question 42

what does the **reward pathway** involve?

Answer 42

neurons that secrete or respond to dopamine

Question 43

how is the reward pathway **activated**?

Answer 43

activated by beneficial behaviour such as eating when hungry

Question 44

what is the active pathway **associated** with?

Answer 44

memory and learning

Question 45

what are **agonists** and what do they **do**?

Answer 45

agonists are chemicals that bind to and stimulate specific receptors by mimicking the action of a neurotransmitter at a synapse

Question 46

what are **antagonists** and how do they **work**?

Answer 46

chemicals that bind to specific receptors preventing the normal neurotransmitter from acting on it greatly reduces or halts the normal transmission of nerve impulses in the pathway

Question 47

2 ways **other** **drugs** **act** and their **effect**

Answer 47

inhibiting enzymes that degrade neurotransmitters inhibiting reuptake of the neurotransmitter at the synapse causing an enhanced effect

Question 48

what do **recreational drugs affect**?

Answer 48

transmission of nerve impulses in the reward circuit in the brain

Question 49

4 things **recreational drugs** can **alter** in an individual

Answer 49

mood cognitive thinking perception behaviour

Question 50

2 **effects** recreational drugs have on **behaviour**

Answer 50

stay awake longer less inhibited

Question 51

what is a **drug addiction** and what is the **cause**?

Answer 51

chronic disease making one compulsively use drugs regardless of consequences repeated use of drugs that act as antagonists

Question 52

how do **antagonist** drugs cause **drug addiction**?

Answer 52

block specific receptors causing the nervous system to compensate by increasing both the number and sensitivity of these receptors

Question 53

what is a **drug tolerance** and what is the **cause**?

Answer 53

when the intensity of an addictive drug is decreased compared to previous uses at the same concentration repeated use of drugs that act as agonists

Question 54

how do **agonist** drugs cause **drug tolerance**?

Answer 54

stimulate specific receptors causing the nervous system to decrease them in both number and sensitivity