week 5 microneuroanatomy

Question 1

What do glial cells do?

Answer 1

Provide nutrients to neuons.Provide structural support to the nervous system

Question 2

Name 3 types of neurons

Answer 2

1. Sensory neurons-transmit info from sensory receptors in body to the brain for further processing.May be very long.
2. Motor neurons-transmit info from the brain to muscles and organs in the body with further instructions on how to function.may be very long.
3. Interneurons-transmit from 1 neuron to another. These are the majority type of neuron in the brain.

Question 3

What is myelin?

Answer 3

Produced by subtpyes of glial cells.White and fatty, acts as an insulator. Coats the axons of neurons.

Question 4

What are the nodes of ranvier?

Answer 4

Unmyelinated gaps in the axon.

Question 5

Where does the action potential occur?

Answer 5

Starts at axon hillock and moves down the axon along the nodes of ranvier, through to terminal buttons.

Question 6

Describe the synapse

Answer 6

The tiny gap between the terminal buttons of one neuron and the dendrites of the next.

Question 7

Describe four morphologial types of neuron

Answer 7

1. Unipolar-has 1 projection from the cell body, which is either an axon or a dendrite
2. Bi-polar-has 2 projections from the cell body. Important role in the visual system
3. Multipolar neuron-has many projections.Most common type of neuron in the brain.
4. Pseudo-unipolar-has only 1 projection from the cell body but this comprises both dendrites and an axon.Most commonly the long motor and sensory neurons which traverse the body.

Question 8

Where do neurons interact with each other?

Answer 8

Across the synapse, or synaptic cleft.Terminal buttons release neurotransmitters which cross the synapse and bind with neuroreceptors in the dendrites of the post-synaptic neuron.

Question 9

What is grey matter?

Answer 9

Cell bodies and dendrites.Most of the outer cortex is grey matter.Some deeper grey matter regions also.

Question 10

What is white matter?

Answer 10

Myelinated axons.Majority of inner brain is white matter, also the spinal cord which has very long myelinated axons projecting to and from body and brain.the corpus callosum is entirely white matter.

Question 11

What is the difference between intra-neuron communication and inter-neuron communication?

Answer 11

Intra is electrical, inter is chemical.

Question 12

What are ions?

Answer 12

Charged molecules, cation = positive, and anion =negative.

Question 13

What is diffusion?

Answer 13

molecules tend to move from area of higher concentration to lower.

Question 14

What is electrostatic pressure?

Answer 14

Molecules tend to moveaway from same charge and towards opposite charge.

Question 15

What is meant by semi-permeability of the cell membrane?

Answer 15

Some particles can move through, but others cannot. Gradients of charge and concentration make them more or less permeable.Altered by opening ad closing of ion channels via electrical stimulation.

Question 16

What is the resting state of intra and extra-cellular space?

Answer 16

Intracellular resting is negative and extracellular resting is positive

Question 17

What is an excitatory potential?

Answer 17

Causes inside of cell to go closer to zero (become more positive), ie less polarised

Question 18

What is an inhibitory potential?

Answer 18

Causes inside of cell to become more negative (more polarised).

Question 19

Where do the graded potentials converge?

Answer 19

At the axon hillock

Question 20

What is the threshold of excitation?What happens when it is reached?

Answer 20

The membrane potential reaches-55 to -65mv, at which point, the neuron fires and an action potential occurs.

Question 21

What is depolarisation,hyperpolarisation and repolarisation?

Answer 21

Neuron becomes more positive, membarne potential goes to -55mv. Achieved by sodium channels opening and sodium entering cell.Then potassium channels open and potassium exits and neuron becomes more negative (repolarisation). As potassium channels stay open fraction longer than sodium, neuron actually goes briefly more negative than -70mv and this is hyperpolarisation.

Question 22

Why can action potentials only go 1 way?

Answer 22

Because ion channels go through a refractory stage where no further opening can occur.

Question 23

Where do action potentials occur? What is this called?

Answer 23

At axon hillock and passes down the nodes of ranvier-this is saltatory communication.

Question 24

What is the relationship between neurotransmitters and graded potentials?

Answer 24

Sum of neurotransmitters (exhitatory and inhibitory)= the potential which which results.Neurotransmitters work to influence which ion channels will be opened or closed.

Question 25

What is the difference between action potential and graded potential?

Answer 25

Graded potential-vary in size. Are the summation of excitatory and inhibitory ligand-gated ion channel proteins(eg neurotransmitters).. Occur at the post synaptic dendrites.
Action potential is all or nothing.Performed by voltage-gated channels.Is one way. Always has a repolarisation period.

Question 26

In general terms, how do psychoactive chemicals affect our brains, and therefore, experience?

Answer 26

Drugs bind to receptors in similar fashion to neurotransmitters. Generally, drugs of addiction stimulate our reward or pleasure centres, Neurotransmitters are linked to cognition/behaviour/emotion ie experience.

Question 27

What determines whether a neurotransmitter will bind to a post synaptic receptor?

Answer 27

a) is the receptor the correct type?
b) is the receptor available or already bound?
c) concentration of neurotransmitter
d) breakdown rate of neurotransmitter

Question 28

Which is faster, inter-neuronal or intra-neuronal transmission?

Answer 28

Intra-neuronal is faster because is electrical and myelin insulates. Inter-neuronal transmission is chemical and takes chemicals longer to traverse the synaptic cleft.

Question 29

How do neurons “know”to stop releasing neurotransmitter?

Answer 29

Feedback loop. Some neurotransmitters will bind to receptors at pre-synaptic neuron.

Question 30

What are the possible outcomes of a drug for neurotransmitters?

Answer 30

a) binds to receptor causing same effect as neurotrnsmitter
b) bind longer at receptor therefore preventing or prolonging action of neurotransmitter
c) enhance or inhibit the breakdown of neurotransmitter

Question 31

What does GABA do?

Answer 31

Most prevalent type of inhibitory neurotransmitter. Increased GABA causes loss of behaviour control, relaxation and sleep.Alcohol, xanax and valium all mimic activation of GABA.

Question 32

What neurotransmitter is activated by most drugs of dependence?

Answer 32

Dopamine. Activated dopamine+activated reward/pleasure pathways, therefore increases the dependence of the drug.

Question 33

What happens if you don’t have enough dopamine?

Answer 33

Tremors. Possibly Parkinson’s.

Question 34

What neurotransmitter is involved in sleep, mood and arousal regulation?

Answer 34

Serotonin.Serotonin is also an inhibitory neurotransmitter. It enhances the effects of Gaba.

Question 35

What does 3,4-methylenedioxy-methampetamine (aka MDA, ecstacy) do neurologically?

Answer 35

Increases serotonin levels therefore increasing empathy, decreasing aggression and decreasing antisocial behaviours. This tells us serotonin is also involved in emotions and empathy.

Question 36

What is aceylcholine involved in?

Answer 36

Involved in learning, memory, movement and muscle cordination. Many treatments for alzeimers are acetlycholinesterase inhibitors.

Question 37

What happens when a seizure occurs?

Answer 37

The brain is having difficulty inhibiting neurons.

Question 38

List the most common neurotransmitters.

Answer 38

Glutamate, GABA,dopamine,serotonin,acetlycholine,endorphins

Question 39

What is an IPSP

Answer 39

inhibitory postsynaptic potential (type of graded potential)

Question 40

What is an EPSP

Answer 40

excitatory postsynaptic potential (type of graded potential)

Question 41

How are neurotransmitters stored?

Answer 41

In vesicles with the neuron cell body

Question 42

how many known serotonin receptor types are there?

Answer 42

14. Some are inhibitory and some are excitatory.Different structures and different locations within the brain

Question 43

What is glutamate involved in?

Answer 43

Most prevalent excitatory neurotransmitter. Very commonly involved in producing EPSP’s. Also implicated in epilepsy and seizures. Very important for learning and memory

Question 44

Why can death occur from drinking too much alcohol?

Answer 44

Alcohol activates GABAnergic neurotransmitter networks causing inhibition of frontal lobes, therefore loss of behaviour control. If enough alcohol is drunk, death occurs due to brain shutdown. Anaesthetics also activate GABA

Question 45

What is dopamine involved in?

Answer 45

activated in reward pathways in brain.All drugs of abuse increase dopamine. Also involved in emotions,motivations,arousal and movement. High levels of dopamine have been linked to schizophrenia.Can have similar psychotic presentations with excessive methamphetamine or cocaine use..Many schizophrenic medicatons aim to reduce dopamine. Parkinson’s causes low levels of dopamine, therefore characteristic tremor. But drugs aiming to treat parkinsons by increasing dopamine risk psychotic episodes.

Question 46

What neurotransmitter do many antidepressants aim to increase?

Answer 46

Increase serotonin. Many anti-depressants are selective serotonin reuptake inhibitors, therefore less serotonin is broken down in the presynaptic neuron and more is available to bind to the post synaptic neuron. Taking antidepressants known to take weeks to months to work, yet known that the increase in serotonin happens very quickly. Why not effect seen sooner is not understood.

Question 47

What are endorphins involved in?

Answer 47

mood and reducing pain. Morphine and heroin increase the activity of endorphin neurons by mimicking the action of endorphins.