Topic 8 exam questions Flashcards
depolarisation
Describe the interaction of the muscles in the eye that led to this dilation of the pupils (3)
-Antagonistic interaction of muscles
-In the iris
-Radial muscles contract and circular muscles relax
Decreasing the intensity of light entering the eye causes pupil dilation
Describe the roles of the circular and radial muscles in pupil dilation (2)
-Muscles work antagonistically
-Circular muscles relax
-Radial muscles contract
Suggest why the pupil appears black (1)
-Pigment at the back of the eye absorbs light / no light is reflected out
There are two sets of iris muscle, the radial muscle and the circular muscles. They work antagonistically to alter the size of the pupil
Explain why these two sets of muscles need to be antagonistic (3)
-Circular muscles contract and radial muscles relax constrict to constrict pupil
-Radial muscles contract and circular muscles relax to dilate the pupil
-These muscles can only shorten
-Antagonistic muscles have opposite effects
Describe the differences in the structure of a myelinated sensory neurone and a myelinated motor neurone (3)
-Sensory neurone has longer dendron
-Sensory neurone has dendron myelinated
-Axon is shorter in sensory neurone
- Sensory neuron has cell body containing nucleus on the side / towards the middle
Describe the role of the myelin sheath in the conduction of nerve impulses (4)
-Myelin sheath plays a role in electrical insulation
-Depolarisation at nodes
-Impulse jumps from node to node
-Saltatory conduction
-Leads to faster conduction
Name the type of cell that forms the myelin sheath (1)
Schwann cell
Describe the role of myelination in the conduction of a nerve impulse (2)
-Provides electrical insulation
-Enables saltatory conduction
Explain why there is a difference in the conduction velocity of these neurones (5)
-Schwann cells cover the axon in myelinated neurone
-Schwann cells / Myelin provide insulation
-Action potential / depolarisation at nodes of Ranvier
-Saltatory conduction in myelinated neurone
-Which means impulse jumps from node to node, leading to faster velocity of the nerve impulse
Describe the role of the dendrites in a neurone (3)
-Forms synapses with other neurones
-Receive impulses from other neurones
-Involved in summation
-Dendrites propagate a signal / initiate an action potential to the cell body / axon
Explain how the structure of the axon cell membrane is related to the conduction of nerve impulses (3)
-Phospholipid restricts ion movement
-Proteins span the membrane
-Sodium / Potassium pump moves ions
-protein gates / channels allow diffusion movement of ions
Explain how myelination increases the speed of transmission of nerve impulses in a sensory neurone (5)
-Neurone cell surface membrane exposed at nodes of Ranvier
-Nodes are the site of clusters of sodium-gate channel proteins
-Which open / close when impulse arrives
-Allowing depolarisation at nodes
-Myelin acts as an electrical insulator on neurone surface between nodes
-Myelin sheath are made of Schwann cells
-Impulse ‘jumps’ from node to node
-This is called saltatory conduction
-Saltatory conduction happens between the myelin layers of the Schwann cell
Describe the role of ion channels in the conduction of a nerve impulse (5)
-Sodium ion channels open
-Sodium ions diffuse in
-Causing depolarisation of the membrane
-Sodium ion channels close and potassium ions channels open
-Then potassium ions diffuse out
-Causing repolarisation of the membrane
Explain the role of ATP in the transmission of impulses along neurones (2)
-ATP required for sodium / potassium pumps
-To move ions against concentration
-To maintain potential difference across axon membrane
Describe how the neurotransmitter crosses this synapse (2)
-Vesicles fuse with presynaptic membrane by exocytosis
-The neurotransmitter crosses the synapse via diffusion
Describe how the arrival of a nerve impulse at a synapse causes the release of neurotransmitters (3)
-Ca2+ enters the synaptic knob / bouton
-Vesicles containing neurotransmitters
-Fuse with the presynaptic membrane and are released into the synaptic cleft
Describe and explain the sequence of events that occurs at the synapse after a neurotransmitter has been released (5)
-Neurotransmitter diffuses across the gap
-It binds to receptors on the post synaptic membrane
-Gated-channels opening / Na+ travels through post-synaptic membrane
-Causing depolarisation
-An action potential is set up in post-synaptic membrane
-Leads to temporal / spatial summation
-Neurotransmitter is broken down by enzymes so there is no prolonged action potential in post-synaptic membrane
-Neurotransmitter can be reabsorbed through pre-synaptic membrane
Explain how MDMA could affect levels of serotonin in the brain (3)
-Higher levels of serotonin
-In the synapse
-Inhibits reabsorption into neurone
Drugs called SSRI’s are used to reduce depression. They work by inhibiting the reabsorption of serotonin at a synapse.
Explain how SSRI’s help to maintain a feeling of well-being (3)
-SSRIs bind to channel / reuptake proteins
-Serotonin levels remain high in the synapse
-Serotonin binds to receptor proteins in post-synaptic membrane
-Depolarisation of post-synaptic membrane
-Action potentials / impulses / transmission continues
Double blind trials give scientists confidence in the results collected.
Explain two ways the design of this trial could be improved in order to increase confidence in the results (4)
-Use more patients / increase sample size / repeat the trial
-To increase reliability
-Use statistical analysis
-To see if the differences are significant
-Consider sample selection to use the same age / gender / ethnicity … of patients
-To control biotic variables
Describe how low serotonin levels in an individual can affect the transmission of impulses in their brain (2)
-Serotonin is a neurotransmitter / there will be less neurotransmitter
-Less serotonin results in fewer depolarisations of post synaptic membranes
-Threshold not achieved / less chance of action potential being produced in post-synaptic neurone
Describe how the use of MDMA could affect the transmission of impulses in the brain (2)
-MDMA prevents re-uptake / increases concentration of serotonin
-Blocking pre-synaptic receptors by bindings to post synaptic receptors
-Nerve pathways using serotonin are more likely to be stimulated so more action potentials generated
Individuals who use MDMA may develop symptoms of depression
Explain how the use of MDMA could result in the development of these symptoms (2)
-MDMA use leads to depletion of serotonin
-Post synaptic membrane becomes less responsive to serotonin / loss of receptors on post synaptic membrane
-Serotonin levels affect mood / lack of serotonin associated with depression
Some early studies of schizophrenia included identical twins raised in separate families
Explain how the design of these studies allows the influence of environmental factors on the development of schizophrenia to be investigated (2)
-Identical twins being raised apart allows for environmental factors to be investigated separately from genetic factors
-Therefore may be able to determine relative amount of risk due to genetic variation / relative amount of risk due to environment