Biopsychology - Neurons + Synaptic Transmssion

Question 1

Neurons

Answer 1

• Basic building blocks of the nervous system

- Nerve cells that process + transmit messages through electrical + chemical signals

Question 2

Sensory neurons (SN)

Answer 2

• carry messages from the PNS to CNS

=> have long dendrites + short axons

Question 3

Relay neurons (RN)

Answer 3

• connect the SNs to motor or other relay neurons

=> have short dendrites + axons

Question 4

Motor neurons

Answer 4

• connect the CNS to effectors (muscles, glands etc.)

=> short dendrites + long axons

Question 5

Structure of a neuron

Answer 5

(1) Cell body - w/ nucleus containing DNA + dendrites which carry impulses from neighbouring neurons towards it
(2) Axon - carries impulse away from cell down length of neuron

Question 6

Myelin sheath

Answer 6

• fatty layer that covers axon to protect it + speed up electrical tranmission
• segmented by nodes of Ranvier (gaps) which speed up transmission by forcing impulse to ‘jump’ across gaps

Question 7

Location of Motor Neurons

Answer 7

• MNs: cell bodies in CNS + long axons form part of PNS

Question 8

Location of Sensory neurons

Answer 8

• SNs : outside of CNS + are in cluster called ganglia in PNS

Question 9

Location of Relay Neurons

Answer 9

• RNs : make up 97% of all neurons - most in brain + visual system

Question 10

Electrical Transmission - firing of a neutron

Answer 10

In resting state, inside is -ve charged
When activated by stimulus - becomes +ve charged for split second
=> causes an action potential which creates electrical impulse down the axon

Question 11

Synaptic Transmission - Chemical

Answer 11

• Neurons communicate in groups - neural networks
• each separated by synapse where chemical signals transmit between them

=> when electrical impulse reaches end of neuron (presynaptic terminal) - triggers release of neurotransmitters from synaptic vesicles

Question 12

Neurotransmitters

Answer 12

Chemicals that diffuse across the synapse w/ specific molecular structure that fits at postsynaptic receptor site
=> like ‘lock + key’

Have specialist functions e.g. ACh found at each point where a MN meets a muscle - when released causes contraction

Question 13

Process of Neurotransmitters

Answer 13

(1) when a NT crosses the gap is taken up by postsynaptic receptor site on dendrites of next neuron
(2) chemical message => electrical impulse + process starts again

=> is a one way process - released from presynaptic neuron terminal + received by postsynaptic neuron

Question 14

Inhibition

Answer 14

When released causes more -ve charge in receiving neuron = less likely to fire

e.g. serotonin has an inhibitory effect

Question 15

Excitation

Answer 15

Causes a more +ve charge in postsynaptic neuron = more likely to fire

e.g. adrenaline (both a hormone + NT) has an excitatory effect

Question 16

Summation

Answer 16

Excitatory + inhibitory influences are summed

• net effect is excitatory = more likely to fire
• net effect is inhibitory = less likely to fire

=> Thus, action potential in postsynaptic nerve is only triggered if sum of signals, at any one time, reaches the threshold

Question 17

Applied to Psychoactive Drugs

Answer 17

Increased understanding of neurotransmitters in brain => allows treatment of mental disorders

e.g. depression linked to low serotonin levels
=> SSRIs used to slow serotonins reuptake after its crossed synapse - stays active longer - improves/stabilises mood