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biology year 2 > 6A Stimulus and response > Flashcards

6A Stimulus and response Flashcards

1
Q

What is a photoreceptor?

A

A receptor that detects light

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2
Q

What is kinesis?

A

This is a non directional random movement in response to the intensity of a stimulus

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3
Q

What is the resting potential of a stimulus?

A

When a nervous receptor is in its resting state theres a difference in the charge between the inside and outside of the cell (inside is -ve charged)
This creates a voltage (potential difference) across the membrane
The retsing potential is generated by ion pumps and channels

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4
Q

What controls the amount of light that is entering?

A

Muscles of the iris

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5
Q

What is a generator potential?

A

When a stimulus is detected the cell membrane becomes more permeable allowing ions to move in and out, which alters potential difference (voltage)

The change in voltage due to a stimulus : Generator potential

A bigger stimulus causes bigger movements of ions so a bigger change in voltage

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6
Q

What is an action potential?

A

If the generator potential is big enough it will trigger an action potential (an electrical impulse along a neurone)
Only generated if the generator potential reaches a threshold level
The strength of the stimulus is measured by the frequency of action potentials

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7
Q

What is a pacinian corpuscle?

A

This is a mechanoreceptor in the skin that detect pressure and vibrations

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8
Q

What is the sensory nerve ending of a PC wrapped in?

A

Connective tissue eg lamallae

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9
Q

Process of pacinian corpuscles after being stimulated??

A
  1. Lamalle deformed and press on sensory nerve ending
  2. Sensory neurones cell membrane to stretch deforming the stretch mediated ion sodium channels
  3. Sodium ions diffuse in creating a generator potential
  4. If the generator reaches the threshold, it triggers an action potential
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10
Q

Where are the photoreceptors found?

A

The retina

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11
Q

What is the fovea?

A

An area of the retina where there are loads of photoreceptors

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12
Q

What is a blind spot?

A

When the optic nerve leaves the eye

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13
Q

Where are nerve impulses from the photoreceptor cells carried too?

A

The retina to the brain by the optic nerve

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14
Q

How do photoreceptors work?

A
  1. Light enters eye, hits photoreceptors and observed by light sensitive optical pigments
  2. Light bleaches pigments, causing a chemical change and altering membrane permeability to sodium ions
  3. Generator potential created and if reaches threshold a nerve impulse is sent along a bipolar neurone
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15
Q

What is a bipolar neurone?

A

A neurone connect photoreceptors to the optic nerve which take impulses to the brain

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16
Q

Differences between rod and cone cells?

A

ROD
- Found in peripheral parts of retina
- Black and white
- Work well in dim light as very sensitive
- Many rods join one bipolar neurone
- Rods have low visual acuity as the brain doesnt get separate information
-

CONE
- Packed together in the fovea
- Colour
- Three types containing a different optical pigment : red/green/blue sensitive
- One cone joins one bipolar neurone so it takes more light to reach the threshold and trigger an action potential
- High visual acuity

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17
Q

What are receptors?

A

Cells or proteins that detect stimuli

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18
Q

What is the structure of the nervous system?

A

LOOK UP DIAGRAM ONLINE

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19
Q

What does myogenic mean?

A

Contract and relax without recieving signals from nerves which can control regular heartbeat

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20
Q

What is the process in the control of heart beat?

A
  1. Starts in SinoAtrialNode ( acts as a pacemaker by sending out regular waves of electrical activity to the atrial walls)
  2. Right and left atria contract at the same time
  3. Electrical acticity transferred from SAN to AtrioVentricularNode (passing waves to bundle of HIS)
  4. AVN has a delay before transferring to make sure atria haveemptied before ventrical contracts
  5. The bundle of HIS (group of muscle fibres responsible for conducting waves of electrical activity between ventricles to bottom of heart) splits into further muscle fibres called Purkyne tissue
  6. Tissue carries waves into muscular walls of ventricles causing them to contract simultaneously
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21
Q

What controls the rate of the SAN?

A

The medulla in the brain

22
Q

What and where are the pressure receptors in the brain controlled by?

A

Baroreceptors in the aorta and carotid arteries that are stimulated by high and low pressure

23
Q

What and where are chemical receptors in the heart controlled by?

A

Chemoreceptors in the aorta, carotid arteries and medulla that momitor o2, co2 and ph in the blood.

24
Q

What is the process of control of heart rate to different stimuli ?

A
  1. High Blood pressure
    - barorececptors send impulses along senspry neurones to medulla to parasympathetic neurone
    - secrete acetylcholine which causes heart rate to slow down by binding to SAN receptors
  2. Low blood pressure
    - sensory neurones to medulla to sympathetic
    - secrete noradrenaline which binds to receptors on SAN
    - heart rate speeds up
  3. High blood 02, low C02, high PH levels
    - chemoreceptors send to sensory neurone to medulla to parasympathetic
    - secrete acetylcholine which binds to receptors on SAN so heart rate can decrease bringing levels back to normal
  4. Low blood 02, high co2, low ph
    - chemoreceptors send to sensory neurone to medulla to sympathetic
    - secrete noradrenaline which binds to receptors on SAN
    - so heart rate can increase bringing levels back to normal
25
Q

What do relay neurones do?

A

They transmit impulses between sensory and motor

26
Q

Where are auxins produced?

A

Tip of shoots and diffuse backwards to stimulate elongation of cells

27
Q

What happens when an electrical impulse reaches the end of a neurone?

A

Neurotransmitters are secreted directly onto cells so the nervous response is localised

28
Q

Which one out of shoots or roots is negatively phototropic?

A

Roots as they grow away from light

29
Q

What does IAA do ?

A

It is moved around the plant to control tropisms via diffusion, active transport and phloem

30
Q

How do plants respond to stimuli ?

A

They do this by regulating their growth

31
Q

How does gravitropism work?

A

IAA moves to the underside of the roots so the cell elongates upwards and the roots go downwards

32
Q

How do receptors communicate with effectors?

A

They communicate via the nervous or hormonal system

33
Q

What is the pathway of communication in a reflex arc?

A

stimulus > receptors > (sensory neurone) > CNS (relay neurone in spinal cord) > (motor neurone) > effectors > response

34
Q

What is a stimulus?

A

Any change in the internal or external environment

35
Q

what is a taxis?

A

A directional movement in response to a stimulu

36
Q

What does an effector do?

A

cells that bring about a response to a stimulus

37
Q

what is a reflex?

A

A simple rapid involuntary movement in response to a stimulus

38
Q

What is gravitropism?

A

The growth of a plant in response to gravity

39
Q

How does phototropism work?

A

This is where IAA moves to the more shaded parts of the shoots and roots, causing elongation so the shoot bends towards the light. This means growth is inhibited in the roots so it bends away from the light

40
Q

What is a type of plant growth factor ?

A

Auxins

41
Q

What is a tropism?

A

Response of a plant to a directional stimulus

42
Q

What does the sensory neurone do?

A

These transmit electrical impulses from the receptors to the cns

43
Q

Which one out of shoots and roots is positively gravitropic?

A

Roots as they grow downwards

44
Q

What is the difference between a positive and negative taxis ?

A

A positive taxis is where they move towards a stimulus whereas a negative taxis is where they move away from the stimulus

45
Q

What do auxins do?

A

Thye stimulate growth in shoots but inhibit growth in roots

46
Q

what is the pathway of nervous communication?

A

stimulus > receptors > (sensory neurone) cns (motor neurone) > effectors > response

47
Q

What is the name of the tropism in response to light?

A

Phototropism

48
Q

How do neurotransmitters take the information to the next neurone?

A

They take the information through a synapse

49
Q

What does the motor neurone do?

A

The motor neurone transmits impulses from CNS to effectors

50
Q

Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.

A
  1. Atrium has higher pressure than ventricle (due to filling / contraction) causing atrioventricular valves to open;
  2. Ventricle has higher pressure than atrium (due to filling / contraction) causing atrioventricular valves to close;
  3. Ventricle has higher pressure than aorta causing semilunar valve to open;
  4. Higher pressure in aorta than ventricle (as heart relaxes) causing semilunar valve to close
  5. (Muscle / atrial / ventricular) contraction causes increase in pressure;

biology year 2 (11 decks)

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