Topic 8

Question 1

Action potential

Answer 1

-The axon has a resting potential of -70mV due to the sodium potassium pump which pumps out 3Na+ for every 2K+ that enter
-When threshold is reached the gated Na+ channels open and Na+ ions enter the cell. This causes depolarisation and an action potential + 40mV
-Na+ channels then close and gated K+ channels open allowing K+ ions to leave the axon causing repolarisation
-Hyperpolarisation occurs when too many K+ leave, but once K+ channels close the resting potential is returned

Question 2

Synaptic transmission

Answer 2

-Nerve impulses arrives at a presynaptic membrane
-Depolarisation causes calcium channels to open - calcium ions diffuse into the presynaptic neuron
-Synaptic vesicles containing the neurotransmitter molecules move towards the presynaptic membrane and fuse with it
-Synaptic vesicles release neurotransmitter into the synaptic cleft
-Neurotransmitter molecules bind to receptor sites on Na+ channels on the post synaptic membrane
-Na+ channels open, Na+ diffuses across the membrane → action potential

Question 3

Summation

Answer 3

Simultaneous release of neurotransmitter from the synapse of several neurons will be sufficient to cause sufficient depolarisation
to generate nerve impulses

Question 4

Explain how SSRIs help to maintain a feeling of well being

Answer 4

-SSRIs bind to channels/ reuptake proteins
-serotonin levels remain high in synapses \
-serertonin binds to receptor proteins in post synaptic membrane
-depolarisation of post synaptic membrane
- action potential continues

Question 5

Compare the use of computed tomography (CT) with magnetic resonance imaging (MRI) for studying brain structure

Answer 5

-image resolution higher in MRI than in CT
-CT therefore can only identify the main structures where as MRI can identify details such as tissues
-MRI use radio waves but CT use X rays
- both give 2d/3d images

Question 6

State two functions associated with the cerebral hemispheres

Answer 6

Think
Learn
Feel emotions
Personality
Ability to see

Question 7

Describe how positron emission tomography (PET) scans can be used to investigate brain structure

Answer 7

-PET make use of radioactive markers and glucose
-PET scans detect emission of positrons
-provides 3d image

Question 8

Describe how the use of MDMA could affect the transmission of impulses in the brain

Answer 8

-MDMA prevents reuptake of serotonin
-which blocks pre synaptic receptors binding to post synaptic receptors
-nerve pathways using serotonin are more likley to be stimulated so more actin potentials are produced

Question 9

Describe the process that occurs at a synapse that leads to habituation

Answer 9

-repeated stimulus decreases the permeability of pre synaptic membrane
- the calciu channels don’t open
-fewer calcium ions can eneter pre synaptic neurone
- fewer vesicles move towards / fuse with pre synaptic membrane
-neurotransmitter wont diffuse across gap
-action potentials is less likley to occur

Question 10

Eyes - in the darks

Answer 10

-Na diffuses in through open channels
- Na moves down concentration gradient
- the inside of the rod cell becomes more positively charged than outside so cell is depolarised
-the depolarisation causes a neurotransmitter to be relased which binds to the bipolar cell preventing it from depolraing
-this prevents any messages being sent to optic nerve to brain

Question 11

Eyes in light

Answer 11

-rhodopsin absorbs light and breaks down into retinol and opsin(bleaching )
- opsin sits over sodium channels blocking them and stopping sodium from entering the cell
- sodium ions are continually pumped out the cell so the inside of the cell becomes more negative (hyperopolaried)
-stops the release of inhibitory neurotransmitter glutamate
-bipolar neurone is depolarised
-impulse transmitted along optic nerve to visual cortext of brain

Question 12

Location of rhodopsin within rod cell

Answer 12

Outer segment

Question 13

Describe how light causes a change in the voltage across the cell surface membrane of a rod cell

Answer 13

-not enough rhodopsin is converted
-so change in voltage is insufficient
- neurotransmitter still relased from rod cell
-so the depolarisation of bipolar neurone is insufficient

Question 14

Describe the role of sodium ions in the functioning of a mammalian rod cell

Answer 14

-sodium ions are pumped out the rod cell
-in light sodium ions do not move back into rod cell - hyperolaised
-in the dark sodium ions can move back into the cell - depolarised

Question 15

Describe the interaction of the muscles in the eye that led to this dilation of the pupils

Answer 15

• antagonistic interaction of muscles
  -in the iris
  -reading muscles contract and circular muscles relax

Question 16

Explain how fMRI can be used to identify the part of the brain involved in interpreting information from the visual cortex

Answer 16

-FMRI detects blood flow in the brain
-increased brain activity results in increased blood flow/demand for oxygen in the are of activity
-oxyhaemoglobin absorbs fewer radio waves
-fmri detects areas where less signal Absorbed

Question 17

Sensory neurone

Answer 17

Transmitts nerve impulses from sensory receptor to CNS

Question 18

Motor neurone

Answer 18

Transmit nerve impulses from CNS to the effectors

Question 19

Relay neurone

Answer 19

found within the CNS to connect other neurones to
form neurone circuits; in the spinal cord they connect sensory and motor neurones

Question 20

Myelin sheaf

Answer 20

wraps around the neuron
Myelin speeds up transmission of impulses and insulates the cell from electrical activity in other nerve cells nearby

Question 21

Schwan cells

Answer 21

Make up the myelin sheath
support and protect neuronal cells
around the body

Question 22

Describe how bacteria can be genetically modified to produce a cytokine for the treatment of neurological and mental disorders

Answer 22

-isolate the gene for the cytokine from DNA
-use a bacterial plasmid as vector
-cut the human dna and the plasmid using the same restriction enzyme
- splice the gene and plasmid together using DNA ligase
-put the modified plasmids into bacterial cells

Question 23

Explain why L-dopa is used to treat people with parkinsons

Answer 23

-l dopa can reach brain unlike dopamine treatment
-converted to dopamine in the brain
-increase dopamine levels in the brain
-Parkinson’s disassemble has low dopamine levels which reduces symptoms of Parkinson’s disease

Question 24

What are in photoreceptors

Answer 24

-rod cells
-cone cells

Question 25

Rod cells detect what colour

Answer 25

Black and white in light and dark

Question 26

Cone cell detect what colour

Answer 26

Any colour in bright light

Question 27

What is a resting potential

Answer 27

-when a neurone is at rest
- -70 volts
-more negative inside than outside
-potassium pumps 3 out and only 2 ub
-therefore outside us more positive at resting poetical