Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology Content > Response To Changes In Environment. > Flashcards

Response To Changes In Environment. Flashcards

1
Q

Define stimulus.

A

A change in internal or external environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define receptors.

A

Specialised cells or proteins in cell membranes which detect stimuli - they are specific to one type of stimuli.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define effector.

A

Cells which bring about a response to a stimuli.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define sensory neurons.

A

Transmit impulses from receptors to the CNS or relay neuron.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define motor neurons.

A

Transmit impulses from CNS/rely to the effectors.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define relay neurons.

A

Transmits impulses from sensory to motor neurons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which part of the nervous system controls unconscious activities?

A

Autonomic Nervous System.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define reflex.

A

A rapid, automatic response which does not need to be learnt.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the process of the reflex arc.

A
  1. Receptors detect stimuli.
  2. Sensory neuron sends an impulse to the spinal cord via the dorsal root.
  3. Relay neuron connects the sensory neuron to the motor neuron.
  4. Motor neuron sends impulse to an effector via the ventral root.
  5. Effector receives impulse and carries out movement.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Give 5 importance’s of a reflex arc.

A
  1. Rapid.
  2. Protect against damage to body tissues.
  3. Do not have to be learned.
  4. Help escape from the predators.
  5. Enables homeostasis control.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define taxes.

A

Organisms move towards or away from a directional stimulus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the difference between a positive and a negative taxis?

A

Positive taxis are when organisms move towards stimulus, whereas negative taxis are when organisms moves away from stimulus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Define kinesis.

A

The organisms’ movements is affected by a non-directional stimulus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does an organism respond to a kinesis?

A

By increasing speed of movement and more rapid change in direction, both slow down when favourable conditions are met.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a tropism?

A

A response in a flowering plant to a directional stimulus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is a positive tropism?

A

Towards the stimulus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a negative tropism?

A

Away from the stimulus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are auxins?

A

Growth factors, which stimulate the growth of shoots by cell elongation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Where are IAA molecules produced?

A

Meristem of shoots and roots.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the function of IAA molecules?

A

IAA stimulates growth by effecting the elongation of cells in roots and shoots.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does a higher concentration of IAA affect the plant?

A

Higher concentration of IAA can have an inhibitory effect on growth of the roots in plants and a stimulatory effect on shoots.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Explain the curvature of the shoot.

A
  1. Tip produces IAA.
  2. IAA diffuses into shoot.
  3. More elongation of cells on one side.
23
Q

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

A
  1. IAA at bottom of root where AII concentration high inhibits elongation of cells.
  2. IAA at the top of the root, where IAA low concentration leads to elongation of cells.
24
Q

What is meant by myogenic?

A

Generates own electrical impulse.

25
Q

Describe the role of the sinoatrial node?

A
  1. Sends out electrical impulses.
  2. Initiates the heartbeat.
26
Q

Describe and explain the initiation and co-ordination of a heartbeat?

A
  1. Sinoatrial node (SAN) initiates heartbeat by sending electrical impulse across arial walls.
  2. Excitation wave doesn’t pass ventricular walls as it is blocked by collagen non-conducting tissue.
  3. Atrioventricular node (AVN) delays impulse, then relays impulse to septum between ventricles. This allows atria to completely empty before ventricles contract.
  4. Bundle of His fibres running through septum conduct electrical impulse to apex of the heart.
  5. Purkyne tissue within Bundle of His carry excitation wave upwards through ventricle muscles from base.
  6. Ventricles contract simultaneously from base upwards.
27
Q

Explain importance of delay caused by AVN.

A
  1. Allows atria to completely empty of blood before ventricles contract.
28
Q

Explain how this is co-ordinated in the heart after initiation of heartbeat by SAN.

A
  1. Electrical impulse only through Bundle of His.
  2. Wave of electrical activity passes over.
29
Q

What are baroreceptors?

A

Pressure receptors that detect changes in blood pressure.

30
Q

Where are baroreceptors located?

A

Aorta and carotid arteries.

31
Q

What are chemoreceptors?

A

Chemical changes that detect changes in the concentration of oxygen and carbon dioxide and changes of pH in the blood.

32
Q

Where are chemoreceptors located?

A

Aorta, carotid receptors and medulla.

33
Q

How does heart respond to high blood pressure?

A
  1. Baroreceptors respond to blood pressure.
  2. More impulses along the parasympathetic neurons, which secrete acetylcholine that bind to receptors on the SAN.
    3.Heart rate slows to reduce blood pressure back to normal.
34
Q

How does the heart respond to low blood pressure?

A
  1. Baroreceptors respond to blood pressure.
  2. More impulses along the sympathetic neurons, which secrete noradrenaline that bind to receptors on the SAN.
    3.Heart rate speeds up to increase blood pressure back to normal.
35
Q

How does the heart respond to high blood oxygen/low cardon dioxide/high pH?

A
  1. Chemoreceptors detect changes in oxygen, carbon dioxide and pH.
  2. More impulses along parasympathetic neurons, which secretes acetylcholine that binds to receptors on the SAN.
  3. Heart rate slows to return oxygen, carbon dioxide and pH back to normal.
36
Q

How does the heart respond to low blood oxygen/high cardon dioxide/low pH?

A
  1. Chemoreceptors detect changes in oxygen, carbon dioxide and pH.
  2. More impulses along sympathetic neurons, which secretes noradrenaline that binds to receptors on the SAN.
  3. Heart rate speeds up to return oxygen, carbon dioxide and pH back to normal.
37
Q

What are dendrites?

A

Receives and carry impulses towards the cell body.

38
Q

What is an axon?

A

Long, membrane covered in cytoplasmic extension which generates action potentials and transmits impulses away from cell body.
Has axon endings which form synapses with effector.

39
Q

What are Schwann cells?

A

Grow around the axon forming a myelin sheath around the cell membrane.

40
Q

What is the myelin sheath?

A

Electrical insulation of the neuron, speeding up transmission of the impulse.

41
Q

What are the nodes of Ranvier?

A

The areas between Schwann cells causing gaps in the myelin sheath important in speeding up rate of transmission of the impulse.

42
Q

How is resting potential maintained and established?

A
  1. Na/K pump actively transports 3Na ions out and 2K ions into the axon membrane.
  2. Membrane is impermeable to Na ions, so Na cannot diffuse back in.
  3. Membrane is slightly permeable to K ions, so some K ions can diffuse back out of axon down electrochemical gradient.
43
Q

What is an action potential?

A

A sudden change in membrane voltage of a neuron in response to a stimulus.

44
Q

Describe what is known as the threshold potential.

A
  1. A stimulus must cause a change in voltage to reach -55mV.
  2. This causes the opening of sodium ion channels in membrane, allowing sodium ions to diffuse into axon down their gradient.
  3. This triggers an action potential.
45
Q

What happens when there is a bigger stimulus?

A

A bigger stimulus increases the frequencies of action potentials, resulting in more action potentials per second.

46
Q

What is the all or nothing principle?

A

If the threshold potential is not reached, there will be no action potential.

47
Q

Describe the generation of an action potential?

A
  1. A stimulus causes an increase in sodium ions inside the axon and it begins to depolarise. Voltage increases.
  2. Depolarisation - if voltage reaches threshold potential, sodium ion channels open, Membrane becomes more permeable to to sodium ions and sodium ions diffuse rapidly into neuron.
  3. Repolarisation - Sodium ion channels close and potassium ion channels open. Membrane is more permeable to potassium ions, potassium ions diffuse out of neuron down potassium ion gradient.
  4. Hyperpolarisation - Too many potassium ions diffuse out of neurone. Voltage is more positive than resting potential.
  5. Resting potential - sodium/potassium pump returns the membrane to -70mV until there is another stimulus.
48
Q

What is a refractory period?

A

A neuron is resistant to a second action potential during this period.

49
Q

What does it mean that the sodium ion channels cannot open during the refractory period?

A
  1. Action potentials don’t overlap.
  2. There is a limit to the frequency at which the nerve impulse can be transmitted.
  3. Action potentials are uni-directional.
50
Q

What are 3 factors which affect the rate of transmission of an impulse?

A
  1. Myelination.
  2. Increase in diameter of an axon.
  3. Higher body temperature.
51
Q

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

A
  1. Myelination provides electrical insulation.
  2. In myelinated, there is saltatory conduction.
  3. In non-myelinated, depolarisation occurs along whole length of axon.
52
Q

How does the diameter of an axon affect the transmission of an impulse?

A

An increase in the diameter of an axon means less resistance to the flow of ions in the cytoplasm.

53
Q

How does body temperature affect the rate of transmission?

A

At a higher body temperature, rate of diffusion of ions is faster.
However, over 40 degrees, proteins begin to denature , and the speed decreases.

54
Q

Describe the sequence of events during synaptic transmission.

A
  1. Action potential arrives at action terminal, depolarisation causes pre-synaptic membrane to become more permeable to Ca2+ as voltage gated Ca2+ ion channels open and Ca2+ enters by diffusion.
  2. Synaptic vesicles fuse with presynaptic membrane.
  3. Neurotransmitter released by exocytosis and diffuses across synaptic cleft.
  4. Neurotransmitter binds to receptors on post synaptic membrane, causing Na+ channels open.
  5. Na+ diffuses in through channels and depolarises the post synaptic membrane. If threshold potential is reached, action potential is generated.

Biology Content (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions