Biopsycholohy: neurons and synaptic transmission

Question 1

What is a neuron?

Answer 1

The basic building blocks of the nervous system, neurons are nerve cells that process and transmit messages through electrical and chemical signals.

Question 2

What is a sensory neuron?

Answer 2

These carry messages from the PNS to the CNS. They have long dendrites and short exons.

Question 3

What is a relay neuron?

Answer 3

These connect the sensory neurons to the motor or other relay neurons.
They have short dendrites and short axons.

Question 4

What are motor neurons?

Answer 4

These connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons

Question 5

How many neurons are there in the human nervous system?

Answer 5

100 billion
80% of which are located in the barin

Question 6

How do neurons transmit signals?

Answer 6

Electrically and chemically

Question 7

What are the three types of neurons?

Answer 7

Sensory neurons, relay neurons and motor neurons

Question 8

What is the structure of a neuron?

Answer 8

Vary in size from from less than a millimetre up to a metre long, but all share the same basic structure.
The cell body includes a nucleus , which contains the genetic material of the cell.
Branchlike structures called dandrites protrude from the cell body.
These carry nerve impulses from neighbouring neurons towards the cell body.
The axon is covered in a fatty layer of myelin sheath that protects the axon and speeds up electrical transmission of the impulse.
The end of the axon are terminal buttons that communicate with the next neuron in the chain across a gap known as the synaps.

Question 9

What is the structure of the myelin sheath?

Answer 9

Segmented by gaps called nodes of Ranvier.
These speed up the stransmittion of the impulse by forcing it to ‘jump’ across the gaps to the axon.

Question 10

What is the location of the neurrons?

Answer 10

The cell bodies of motor neurons may be in the in the CNS but they have long axons which form part of the PNS.
Sensory neurons are located outside the CNS in the PNS in clusters known as Ganglia. Relay neurons make up 97% of all neurons and most are found withing the brain and the visual system.

Question 11

What is the process of the electrical transmittion - the firing of a neuron?

Answer 11

When a neuron is in a resting state the inside of the cell is negatively charged compared to the outside.
When a neuron is activated by a stimulous the inside of the cell becomes positively charged for a split second causing an action potential to occur. his creates an electrical impulse that travels down the axon towards the end of the neuron.

Question 12

What is synaptic transmission?

Answer 12

The process by which neighboring neurons communicate with each other by sending chemical messages across the gap that seperates them.

Question 13

What is a neurotransmitter?

Answer 13

Brain chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to another.
Neurotransmitters can be broadly divided into those that perform an excitatory function and those that perform an inhibitory function.

Question 14

What is excitation?

Answer 14

When a neurotransmitter such as adrenaline, increases the positive charge of the postsynaptic neuron. This increases the likelihoodthat the postsynaptic neuron will pass on the electrical impulse.

Question 15

What is inhibition?

Answer 15

When a neurotransmitter, such as serotonin, increases the negative charge of the posstsynaptic neuron. This decreases the likelihood that the postsynaptic neuron will pass on the electrical impulse.

Question 16

How do neurons communicate with each other?

Answer 16

Within groups known as neural netwroks.

Question 17

Are signals within neurons transmitted electrically or chemically?

Answer 17

Electrically

Question 18

Are signals between neurons transmitted electrically or chemically across the synaps?

Answer 18

chemically

Question 19

When electrical impulse reaches the end of the neuron it triggers the release of what?

Answer 19

neurotransmitter from tiny sacs called synaptic vesicles.

Question 20

Once a neurotransmitter crosses the gap, it is taken up by what?

Answer 20

Postsynaptic receptor site on the dendrites of the next neuron (axons take signals to the synaps, dendrites take signals away)

Question 21

What happens in the postsynaptic reseptor site?

Answer 21

The chemical message is converted back into an electrical impulse and the process of transmission begains again in this other neuron.

Question 22

Each neurotransmitter has its own what?

Answer 22

Specific molecular strucute that fits perfectly into a postsynaptic receptor site, similar to lock and key.

Question 23

Neurotransmitters have either of two what that have an effect on the neighbouring neuron?

Answer 23

Excitatory or inhibitory

Question 24

Neurotransmitters either have what of two effects on the neighboring neurons? Give an example of this and a contrast example?

Answer 24

Neurotransmitters either have an excitatory or inhibitory effect on the neighbouring neuron
eg, the neurotransmitter serotonin causes inhibition in the recieving neuron, resulting in the neuron becoming more negatively charged and less liekly to fire.
In contrast, adrenaline (an element of the stress response which is both a hormone and a neurotransmitter) causes excitation of the postsynaptic neuron by increasing its positive charge and making it more likely to fire.

Question 25

Weather a postsynaptic neuron fires is decided by what?

Answer 25

Weather a postsynaptic neuron fires is decided by the process of summation.

Question 26

The excitatory and inhibitory influences are summoned: if the net effect on the post synaptic neuron is inihitory then the postsynaptic neuron is what?

Answer 26

The excitatory and inhibitory influences are summoned: if the net effect on the post synaptic neuron is inhibitory then the postsynaptic neuron is less likely to fire.
If the net effect is excitatory it is more likely to fire.
Therefore the action potential of the postsynaptic neuron is only triggered if the sum of the excitatory and inhibatory signals at any one time reaches the threshold.

Question 27

Increased understanding of the mode of action of neurotransmitters in the brain has led to what? Name an example.

Answer 27

Increased understanding of the mode of action of neurotransmitters in the brain has led to the development of psychoactive drugs to treat mental disorders.
Eg, depression has been linked to low levels of serotonin, which is thought to play an important role in stabalising mood.

Question 28

A category of drugs known as SSRI’s such as what? Do what to the synapse?

Answer 28

A category of drugs known as SSRI’s such as Prozac, slow down the reuptake of serotonin after it has crossed the synapse, ensuring it stays active for longer in the synapse.