nervous system part 2

Question 1

what is the basic structural unit of the brain and how many do we have

Answer 1

neurons. we have 86 billion neuron’s and each can communicate to a 1000 other neuron’s

Question 2

how do neutrons communicate with each other

Answer 2

they communicate through synapses

Question 3

what are the parts of a neuron

Answer 3

single cell body- where the nucleus cell is. in this we have dendrites- receive information and axons- transmit information.

Question 4

how does the neurone work

Answer 4

each cell will have a single axon emitting from a single body with multiple dendrites. the axon will transmit information to the neighbouring neuron where it will make a synapse to the dendrite of a neighbouring neuron.

Question 4

why does it not matter that there is only a single axon and what does this do

Answer 4

the axon can branch and connect to more than one target neurons .

Question 5

how are information encoded

Answer 5

action potential

Question 6

what are the parts of a neuron

Answer 6

-dendrite
-nucleus
-axon
-myelin sheath
- node of river
- Schwann cell
- axon terminal

Question 7

what contributes to the negative state of the intracellular layer of the cell

Answer 7

there is a higher protein concentration inside the cell- it is slightly negative charged. another is the potassium channels. another is the potassium sodium pump where potassium goes out of the cell (because its moving against the concentration gradient) making it more negative

Question 8

explain what the equilibrium point is or the resting membrane potential

Answer 8

there is an equal voltage or charge outside and inside the cell. this is there is an equal amount of potassium inside and outside.

Question 9

what is the resting potential of a neuron and general cells

Answer 9

neurons are -65 but cells are generally -50 to -90

Question 10

what can alter the resting membrane potential

Answer 10

voltage gated ion channels that are specific for different ions.

Question 11

what type of stimulus can open channels

Answer 11

action potential arriving from a neighbouring neuron.

Question 12

how does action potential work.

Answer 12

• resting potential
• depolarisation
  -repolarisation
• resting potential
  refer to video on YouTube if needed

Question 13

how doest the propagation of action potential work

Answer 13

in response to a signal, the soma end of the axon becomes depolarised. as depolarisation work on that cell, it will trigger the depolarisation along the axon to trigger the action potential of a neighbouring neurons by reaching the axon terminal and connected by synapse. during this the whole process will start again.

Question 13

how come cells cannot be depolarised again for a while after it has depolorised

Answer 13

because it is in a repolarisation state where it is starting to move negative again.

Question 14

are all action potential the same eg. if you brush yourself with a feather vs hit yourself with a hammer.

Answer 14

yes. larger stimulus just means it increases the frequency. you can have multiple action potentials happening along the neuron BUT there s a wait as the neuron needs to finish depolarising and return to its normal state.

Question 15

aside from increasing frequency of action potential, how else can the nervous system encode a stronger stimulus

Answer 15

by recruiting different action potentials in different axons

Question 16

what is the benefit of the axons being wrapped in mylin

Answer 16

because mylin is lipid dense- made of 80%, its a good insulator and blocks ions diffusing across it. it also increases the speed of nerve conduction.

Question 17

what is the cell responsible for myelination

Answer 17

oligodendrocyte- not a neuron cell. its found in central nervous system. it supports neuron through the process of myelination

Question 18

how can’t are the nodes of ranvier

Answer 18

they are high concentration of voltage gated potattisum channels. these are areas of the axon that are umyelniated. this allows the action potential to travel faster by skipping areas and just jumping from node to node.

Question 19

what does the nodes of ranvier hav and what does this mean

Answer 19

they have high concentrations of potassium and sodium. this means that they are highly adapted to them and is always ready to fire.

Question 20

what happens if you damage oligodendrocyte

Answer 20

you lose some myelination and thus make the action potential travel slower and take longer to reach the axon terminal slowing down transmission in sensory and motor pathways. they can regenerate however so patients can recover.

Question 21

what properties impact the speed an action potential travels

Answer 21

• diameter: the larger the diameter the easier the action potential to generate and travel
  -fiber type
  -conduction velocity

Question 22

which fibres are myelinated and which are not and which of the myelinated ones are the strongest

Answer 22

A and B fibres are myelinated while C is not. A alpha is the most heavily myelinated, followed by beta, gamma and delta.

Question 23

what function does the A alpha control and what does other fibres control

Answer 23

A alpha controls efferent motor neurons while others carry afferent sensory information

Question 24

which fibres are the slowest fibres

Answer 24

C fibres

Question 25

how do we transmit pain

Answer 25

through 2 ways. delta fibres transmit first type of pain which is sharp and localised. the second is the C fibre is the dull ache that last for a little bit.

Question 26

what are neurotransmitters

Answer 26

they are chemical molecules in the neuron. They are synthesised in the cell body.

Question 27

how do action potentials reach the other axon

Answer 27

they do this through neurotransmitters. they get transported along the axon to the axon terminal packaged into vesicles and sit at the axon terminal until it is transported to the synapse and diffuse across the synapse, to the synaptic cleft and bind to the receptor (ligand gated channels) of the post synaptic membrane

Question 28

what triggers the release of neurotransmitters

Answer 28

its the action potential reaching the end of an axon which opens voltage gated calcium channels- positive ions that have higher concentration on the outside than inside. when it opens, the calcium floods in to the cell which serves as a stimulus.

Question 29

what is the name of the presynaptic membrane and the post synaptic membrane

Answer 29

axon terminal is the presynaptic membrane and the post synaptic membrane is the neighbouring neuron and contains the receptor for the neurotransmitter.

Question 30

why are neurotransmitters broken down and how

Answer 30

if it stays in the synapse, it will continue to activate receptors. it is removed by being broken down by enzymes or is taken back up into the presynaptic neurone and packed back into a vesicle

Question 31

how does removal of transmitters influence health interventions

Answer 31

they target the breakdown to prolong their effect. eg. depression- selective serotonin uptake. this allows the serotonin to stay in the synapse longer and allow it to stimulate the post synaptic neuron longer. this normalises the imbalance of having lower serotonin

Question 32

explain the different types of neurotransmitters and which ar the most important

Answer 32

Glutamate: major excitatory neurotransmitter (wants action potential to happen). the glutamate binds to I its receptor, it will cause the opening of the sodium channel in the post synaptic membrane, which is connected to the receptor. when sodium floods in, it increases the membrane potential getting closer to the threshold for triggering an action potential. this is called an excitatory post synaptic potentials (EPSPs). one of it is not enough so you will need multiple to reach the threshold. GABA: major inhibitory neurotransmitter (doesn't want action potential to happen). they are coupled to chloride channels but are negatively charged ions. they make the cell even more negative so the cell does not get depolarised. this is known as inhibitory post synaptic potential (IPSPs). acetylcholine: can be excitatory or inhibitory in the brain. it is in the central and peripheral nervous system. in the peripheral nervous system, at the neural muscular junction (specialised synapse where a motor neuron communicates with a muscular fibre, triggering the transmission of nerve signals to trigger muscle contraction), it is excitatory in the muscle

Question 33

since one EPSPs is not enough to trigger action potential, what do you do and what is this called.

Answer 33

summation: temporal summation which is time dependant. you get multiple EPSPs generated within a single dendrite- imported from a single neuron. OR spatial where EPSPs are generated from different dendrites from the pre synaptic membrane

Question 34

whats the difference between temporal summation and spatial summation

Answer 34

temporal summation uses just one dendrite and gets all the EPSPs from one neuron. there is not a lot of integration. better fro transferring info along pathways without changes. better in the peripheral nervous system in the spinal cord. spatial: integration from different neurons. better for complex processing.

Question 35

what do you call when the action potential jumps from one node of ranvier

Answer 35

saltatory conduction