Grey Matter Flashcards Preview

A Level Biology (Edexcel Salters) > Grey Matter > Flashcards

Flashcards in Grey Matter Deck (50)
Loading flashcards...
1
Q

Which direction do dendrites travel?

A

Towards the cell body.

2
Q

Which direction do axons travel?

A

Away from the cell body.

3
Q

Describe a reflex arc.

A

Receptors detect a stimulus. Sensory neurons conduct a nerve impulse to the CNS which enters the spinal cord through the dorsal route. A synapse is formed with a relay neuron and then a motor neuron via the ventral route. The motor neuron transmits the impulse to an effector.

4
Q

Describe the pupil reflex.

A

Light strikes photoreceptors in the retina. Sensory neurons pass nerve impulses along the optic nerve to the CNS. These impulses are sent along parasympathetic motor neurons. Circular muscles contract and radial muscles relax. The pupil constricts, reducing the amount of light entering the eye.

5
Q

Describe the resting potential.

A

-70mV.
The inside of the axon is more negative than the outside and hence the membrane is polarised.

Na+/K+ pump creates a concentration gradient. K+ diffuses out of the cell, down a concentration gradient, the membrane becomes polarised. The potential difference pulls K+ back inside the cell. There is no net movement of K+.

6
Q

Describe an action potential (depolarisation, repolarisation and hyperpolarisation).

A

Depolarisation occurs when voltage-dependent gated Na+ channels open, causing a flow of Na+ ions. All-or-nothing. Potential difference of +40mV. There is a refractory period to ensure that impulses only travel one way.
Repolarisation occurs when Na+ channels close but K+ channels open. K+ ions leave the axon down an electrochemical gradient, repolarising the membrane.
Hyperpolarisation happens when more ions move out of the cell than usual. K+ channels close and K+ diffuses back into the axon.

7
Q

What does the size of a stimulus affect?

A

Frequency of impulses.

Number of neurons in a nerve conducting impulses.

8
Q

Define saltatory conduction.

A

An impulse jumps from one node to the next due to an electrical current inducing an action potential.

9
Q

Describe speed of conduction.

A

Determined by the diameter of an axon. Speed is quicker for normal squid but slower for a giant squid.
The myelin sheath acts as an electrical insulator and the depolarisation occurs in the nodes of Ranvier.

10
Q

Describe the process of neurotransmission.

A

An action potential arrives at the pre-synapse. The membrane depolarised and Ca2+ channels open. Synaptic vesicles fuse with the pre-synapse membrane. The neurotransmitter is released into the synaptic cleft and binds with receptors on the post-synaptic membrane. Cation channels open and Na+ ions flow through. The membrane depolarises and causes an action potential. Neurotransmitter is taken up by the pre-synapse membrane.

11
Q

What are synapses used for?

A

Control of nerve pathways.

Integration of information from different neurons.

12
Q

Describe excitatory synapses.

A

Post-synaptic membrane is more permeable to Na+ ions.

13
Q

Define spatial summation.

A

Different synapses, different neurons.

14
Q

Define temporal summation.

A

Several impulses from a single neuron.

15
Q

Describe inhibitory synapses.

A

Less likely for there to be an action potential. Cl- and K+ channels are opened. Greater potential difference leads to hyperpolarisation.

16
Q

What are the differences between nervous and hormonal control?

A

Nerves transmit signals electrically, hormones transmit signals chemically.
Nerves are fast acting, hormones are slow acting.
Nerves create short-term changes, hormones create long-term changes.
Nerves are transmitted in action potentials, hormones are transported in blood.
Nerves have a local response, hormones have a widespread response.

17
Q

How does auxin work?

A

Stimulates growth in response to cell elongation.
Increased concentration on shaded side increases cell elongation, reduced concentration on illuminated side inhibits cell elongation.

18
Q

What other factors are plants sensitive to?

A

Gravity.
Touch.
Mechanical stress.

19
Q

Describe rod cells in the dark.

A

Na+ ions flow through non-specific cation channels and move down a concentration gradient. Depolarises the cell. Glutamate is released and binds to bipolar cells.

20
Q

Describe rod cells in the light.

A

Light falls on rhodopsin which breaks down into retinal and opsin. Opsin stimulates hydrolysis of nucleotides, closing cation channels, the inside of the cell is hyperpolarised. Glutamate is inhibited. The bipolar cell is depolarised, an action potential is induced.

21
Q

Describe phytochromes.

A

Pr absorbs red light.
Pfr absorbs from red light.
Sunlight converts Pr into Pfr, darkness converts Pfr into Pr.
Phytochromes develop leaves and pigments and inhibit elongation of internodes.

22
Q

What does Pfr do?

A

Inhibits germination.
Stimulates flowering in long-day plants.
Inhibits flowering in short-day plants.

23
Q

What happened to Phineas Gage?

A

A three foot iron bar went through the front of the left hemisphere.
He suffered personality changes.

24
Q

What happened to Lincoln Holmes?

A

A car accident that damaged the temporal lobe.

Can no longer recognise any faces.

25
Q

Describe the consequences of a stroke.

A

Problems with speech, understanding, reading and writing.

26
Q

What leads to recovery from a stroke?

A

Neural plasticity.

27
Q

Describe a CT scan.

A

Narrow beam x-rays.

3D picture.

28
Q

Describe an MRI scan.

A

Magnetic field and radio waves detect soft tissue. Nuclei line up with the magnetic field.
3D image.

29
Q

Describe an fMRI scan.

A

Follows areas of the brain by following uptake of oxygen. Deoxyhaemoglobin absorbs radio waves.

30
Q

Describe a PET scan.

A

Short half-life isotopes. Injected with a radiotracer. A positron collides with an electron and emits gamma rays.

31
Q

Describe how PET scans help diagnose Alzheimer’s.

A

The accumulation of beta amyloid is a sign of Alzheimer’s. Synapses become blocked by beta amyloid proteins. This can be tracked with an amyloid tracer.

32
Q

Describe visual development.

A

Columns of cells are stimulated in an alternating pattern. Formed during critical period.

Proven by injecting tracers into ferrets.

Light deprivation in one eye leads to narrower columns. Axons are not stimulated and synapses are weakened.

33
Q

Describe monocular deprivation.

A

Depriving vision from one eye.
Monocular deprivation as an infant leads to permanently impaired vision.
Removal of cataracts when older can return vision.

34
Q

Describe depth perception.

A

Close objects are seen from two angles and are stereoscopic. Distant objects are influenced by visual cues and past experiences.

Cross-culturally, depth perception is different. The Carpented World Hypothesis shows that Western cultures perceive depth differently, in accordance to the Müller-Lyer illusion, than those in circular cultures.

Babies encouraged to crawl across a glass table where a cliff ledge was pictured underneath proves that depth perception is not innate.

35
Q

How are memories created?

A

Patterns of connections.

Strength of synapse.

36
Q

Define habituation.

A

A learning style referring to the ability to ignore repeated, unimportant stimuli.

37
Q

Describe how habituation works.

A

Insufficient neurotransmitter is released. Ca2+ channels are less responsive and the post-synaptic membrane is not depolarised. The reflex arc is incomplete.

38
Q

Describe ethics involving animal use.

A

Animals cannot give consent.
Suffering of a small number of animals may lead to treatment for many.
Animal rights are questionable.
Not all animals have the same rights, invertebrates do not feel pain.
Animal welfare is paramount in an investigation.

39
Q

What are the symptoms are Parkinson’s Disease?

A

Muscle stiffness
Tremors
Poor balance and motor skills
Slurred speech.

40
Q

What causes Parkinson’s Disease?

A

Lack of dopamine as dopamine-secreting neurons in the basal ganglia die.

41
Q

What are the treatments for Parkinson’s Disease?

A

MAO inhibitors, slowing the loss of dopamine by inhibiting enzymes that break down dopamine.
L-Dopa, precursor to creating dopamine.
Dopamine agonists activate dopamine receptors.
Gene therapy.
Deep brain stimulation.

42
Q

Describe the cause of depression.

A

Multifactorial. Lack of serotonin, the gene, 5-HTT, increases susceptibility.
Diathesis-stress model.

43
Q

Describe the treatments for depression.

A

MAO inhibitors.

SSRIs.

44
Q

Describe drugs and synaptic transmission.

A

Neurotransmitter is synthesised and stored. The neurotransmitter is released and binds to the receptor. The neurotransmitter goes through reuptake and then breakdown.

SSRIs prevent the reuptake, increasing the serotonin levels in the post-synaptic membrane.

45
Q

Describe the effects of MDMA.

A

Increases serotonin in the synaptic cleft by binding molecules responsible for transporting serotonin to the cell.

Leads to hyperthermia, high blood pressure, irregular heartbeat, muscle breakdown, kidney failure.

46
Q

Describe the Human Genome Project.

A

Aims to discover all genes in the human species.

47
Q

Define single nucleotide polymorphisms.

A

DNA sequence varies, one nucleotide is affected in 1% of the population.

48
Q

How is genetic modification carried out?

A

Pharming: human gene is cut with restriction enzyme and spliced in plasmid. Modified plasmid is allowed to multiply, bacterial cells are destroyed and protein is extracted and purified.

Artificial selection: marker gene and wanted gene incorporated into a vector. Undergoes micropropagation (multiplication).

Gold or tungsten coated particles coated with DNA fired into a cell with a gene gun.

49
Q

What are the concerns of genetic modification?

A

Health: transfer of antibiotic resistant genes to microbes, formation of harmful products, transfer of viruses between animals and humans.

Environment: transfer of genes to non-target species, crops may increase chemicals in agriculture, breeding of superweeds.

Choice.

Ownership.

50
Q

Define propagation.

A

The breeding of plants or animal specimens from a parent cell/organism.