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biology > Unit 6 - Responses To Change > Flashcards

Unit 6 - Responses To Change Flashcards

1
Q

Advantages of taxis to organisms

A
  • avoid competition
  • to find a mate
  • increase dispersal
  • to avoid predators
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2
Q

Advantages of simple reflexes

A
  • rapid
  • protect against damage to body tissues
  • do not have to be learnt
  • help escape from predators
  • enable homeostatic control
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3
Q

Use your knowledge of indoleacetic acid (IAA) to explain the curved growth of a shoot

A
  1. Tip produces IAA
  2. IAA diffuses down shoot
  3. Cells elongate more on one side than the other
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4
Q

Explain how the uneven distribution of IAA causes a root to bend

A
  1. High concentration of IAA inhibits cell elongation
  2. Root bends away from light
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5
Q

Describe the role of receptors and of the nervous system in the increasing of heart rate

A
  1. Chemoreceptors detect rise in CO2
  2. Send impulses to medulla
  3. Impulses to SAN
  4. By sympathetic nervous system
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6
Q

When the heart beats, both ventricles contract at the same time. Explain how this is coordinated in the heart after initiation of the heartbeat by the SAN

A
  1. Electrical activity only through bundle of His
  2. Wave of electrical activity passes over both ventricles at the same time
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7
Q

Describe how the heartbeat is initiated and coordinated

A
  1. SAN sends wave of electrical activity across atria and causes atrial contraction
  2. Non-conducting tissue prevents immediate contraction of ventricles
  3. AVN delays impulse whilst blood leaves atria
  4. AVN sends impulses down bundle of his
  5. Causing ventricles to contract from base up
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8
Q

The heart controls and coordinates the regular contraction of the atria and ventricles. Describe how

A
  1. SAN - AVN - bundle of his
  2. Impulses over atria
  3. Atria contracts
  4. Non conducting tissue
  5. Delay at AVN ensures atria empty
  6. Ventricles contract from base upwards
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9
Q

The cardiac cycle is controlled by the sinoatrial node (SAN) and the atria ventricular node (AVN). Describe how.

A
  1. SAN initiates heartbeat
  2. SAN sends impulses across atria causing atrial contraction
  3. AVN delays electrical impulses
    4.. Allowing atria to empty before ventricles contract
  4. AVN sends impulses down bundle of his
  5. Causes ventricles to contract from base upwards
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10
Q

Explain how a resting potential is maintained across the axon membrane in a neurone

A
  1. Higher concentration of potassium ions inside and higher concentrations of sodium ions outside the neurone
  2. Membrane more permeable to sodium ions
  3. Sodium ions transported out and potassium ions in
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11
Q

Explain why the speed of transmission impulses is faster along a myelinated axon than along a non-myelinated axon

A
  1. Myelination provides electrical insulation
  2. In myelinated depolarisation only occurs at nodes of ranvier
    In non myelinated depolarisation occurs along whole length of axon
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12
Q

Describe the sequence of events involved in transmission across a cholinergenic synapse

Do not include details on the breakdown of acetylcholine in your answer

A
  1. Depolarisation of membrane
  2. Calcium channels open and calcium ions enter
  3. Synaptic vesicles fuse with presynaptic membrane and release acetylcholine
  4. Acetylcholine diffuses across synaptic cleft
  5. Acetylcholine attaches to receptors on the postsynaptic membrane
  6. Sodium ions enter postsynaptic neurone leading to depolarisation
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13
Q

Describe how the influx negatively charged ions can inhibit postsynaptic neurones

A
  1. Inside of postsynaptic neurone becomes more negative
  2. More sodium ions required to reach threshold
  3. For depolarisation/action potential
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14
Q

Explain how blocking the calcium ion channels at some synapses can reduce impulses at the post synaptic membrane

A
  1. No calcium ions enter synaptic knob via calcium ion channels
  2. No synaptic vesicles fuse with presynaptic membrane and no neurotransmitter released
  3. No neurotransmitter diffuses across synaptic cleft
  4. No neurotransmitter attaches to receptors on the postsynaptic membrane
  5. No sodium ions enter postsynaptic neurone so no impulses sent to brain
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15
Q

Suggest and explain how the interaction between the circular and radial muscles could cause the pupil to constrict (narrow)

A

1.circular muscle contracts
2. Radial muscle relaxes

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16
Q

Explain how a fovea allows an organism to see in detail

A
  1. High visual acuity
  2. Each cone is connected to a single neurone
  3. Cones send separate impulses to brain
17
Q

Explain how a high density of rod cells allows an organism to have good night vision

A
  1. High visual sensitivity
  2. Several rods connected to a single neurone
  3. Enough neurotransmitter to reach threshold
18
Q

Describe how stimulation of a pacinian corpuscle produces a generator potential

A
  1. There are stretch-mediated sodium ion channels in the membrane
  2. Increased pressure deforms sensory neurone membrane
  3. Sodium ion channels open
  4. Sodium ions diffuse in
  5. Depolarisation leading to generator potential
19
Q

Describe the roles of ATP in muscle contraction

A
  1. To break actinomyosin bridges
  2. To move and bend myosin head
  3. so actin filaments are moved inwards
  4. For active transport of calcium ions into sarcoplasmic recticulum
20
Q

Explain how a decrease in the concentration of calcium ions within muscle tissues could cause decrease in the force of muscle contraction

A
  1. No tropomyosin moved from binding site
  2. No actinomyosin bridges formed
  3. Myosin head does not pull actin filaments
21
Q

Describe the role of glucagon in gluconeogenesis

A
  1. Attaches to receptors on target cells and activates enzymes
  2. Glycerol/amino acids/ fatty acids into glucose
22
Q

Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration

A
  1. Less ATP is converted to cAMP
  2. Less kinase is activated
  3. Less glycogen converted to glucose
23
Q

Explain why a pancreas transplant would not be suitable treatment for type 2 diabetes

A
  1. Type 2 produces insulin
  2. Cells/ receptors are less sensitive to insulin or faulty insulin receptors
  3. Treated/ controlled by diet/excerise
24
Q

Adrenaline binds to receptors in the plasma membranes of liver cells. Explain how this causes the blood glucose concentration to increase

A
  1. Adenylate cyclase activated
  2. Activates enzymes so glycogenolysis occurs

biology (7 decks)

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