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Biology > 6A Response to Stimuli > Flashcards

6A Response to Stimuli Flashcards

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1
Q

Define a stimulus

A

change in the internal/external environment

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2
Q

What detects a stimulus?

A

receptors

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3
Q

What do effectors do? Give examples of effectors

A

bring about a response to stimuli eg. muscle cells and cells in glands

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4
Q

What is the simple difference between the central nervous system and the whole nervous system?

A

CNS= brain and spinal cord, coordinates info
NS= made up of all the neurons in the body. 3 main types are sensory, relay and motor

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5
Q

Simply describe what happens during a reflex action

A
  1. receptors in a sense organ detect a stimulus
  2. electrical impulses are sent along sensory neurons to the CNS
  3. the CNS sends electrical impulses to an effector along a motor neuron
  4. the effector then responds accordingly
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6
Q

Describe simply what a synapse is

A
  • the connection between 2 neurons
  • nerve signal is transferred by chemicals called neurotransmitters which diffuse across the gap
  • these chemicals set off a new electrical signal in the next neuron
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7
Q

What are auxins?

A
  • plant growth hormones
  • they control growth at the tips of shoots and roots
  • they move around the plant in solution
  • they stimulate growth in shoots and inhibit growth in roots
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8
Q

What is a taxis?

A
  • a directional response to a stimulus
  • eg. a woodlouse moving away from a light source which increases its chance of surviving predation
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9
Q

What is a kinesis?

A
  • a non-directional response to a stimulus
  • eg. woodlouse moving slowly in humid conditions which leaves them in humid conditions for longer so less water loss and increased survivability
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10
Q

What is a tropism?

A
  • directional response to a stimulus by a PLANT
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11
Q

Describe phototropism

A
  • directional response too light
  • positively phototropic = grows towards light
  • negatively phototropic = grows away from light
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12
Q

Describe gravitropism

A
  • directional response to gravity
  • positively gravitropic = grows towards gravity/downwards
  • negatively gravitropic = grows away from gravity/upwards
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13
Q

Describe the tendancies of plant roots

A
  • positively gravitropic
  • negatively photoropic
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14
Q

Describe the tendancies of plant shoots

A
  • negatively gravitropic
  • positively phototropic
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15
Q

What is indoleacetic acid?

A
  • IAA
  • a type of auxin of flowering plants
  • can diffuse into nearby cells or can be carried in the phloem
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16
Q

How is IAA responsible for phototropism?

A
  • diffuses to shady side of plants and encourages cell elongation so plant bends towards light (SHOOTS)
  • in ROOTS it inhibits cell elongation so the root grows away from the light
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17
Q

How is IAA responsible for gravitropism?

A
  • diffuses to the underside of shoots and roots
  • in the shoots this encourages upward growth because it elongates the cells on the underside
  • in shoots it inhibits cell elongation in the underside cells so it encourages downward growth
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18
Q

Give an example of receptors

A
  • rods and cones
  • photoreceptors in the eyes
  • allow for the detection of light
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19
Q

What does the CNS consist of?

A

brain and spinal cord

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20
Q

What does the PNS consist of?

A
  • the autonomic section and the voluntary section
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21
Q

What does the autonomic section of the PNS consist of?

A
  • sympathetic response (fight or flight)
  • parasympathetic response (rest or digest)
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22
Q

Compare and contrast the nervous system and the endocrine system

A
  • nervous is fast, endocrine is slow
  • nervous is short-lasting, endocrine is long-lasting
  • nervous is electrical, endocrine is chemical
  • nervous is a localised area, endocrine is a generalised area
  • nervous travels via neurons, endocrine travels in bloodstream
23
Q

What is the summary order of a reflex arc?

A
  • stimulus
  • receptor
  • sensory neuron
  • CNS (relay neuron)
  • motor neuron
  • effector
  • response
24
Q

What do receptors detect?

A
  • a single type of stimulus
  • eg. change in light, temp or pressure
25
Q

Describe what is happening with a receptor when it is resting

A
  • there’s a difference in electrical charge between the inside and outside of the cell
  • imbalance in charge is due to the differing concs of ions
  • this is resting potential
26
Q

At rest, which part of the cell is more negatively charged?

A
  • the inside is more negatively charged
27
Q

What do changes in electrical charge create?

A
  • voltage
  • the changes in charge are small so we use millivolts as the unit
28
Q

What are generator potentials?

A
  • small changes in voltage across cell membranes
  • receptor detects stimulus, membrane becomes excited
  • this means ions can move into the cell more easily
  • the influx of ions causes a voltage change
29
Q

What is an action potential?

A
  • when the generator potential is large enough an action potential is triggered
  • an action potential is an electrical impulse that travels down the neuron
  • a certain voltage must be reached for this to happen
30
Q

What is the threshold potential?

A
  • the certain voltage value that must be reached for the action potential to be sent down the neuron
31
Q

Are action potentials variable in size or always the same?

A
  • always the same
  • all or nothing principle
32
Q

What are Pacinian corpuscles?

A
  • mechanoreceptors found on the surface of the skin
33
Q

What do Pacinian corpuscles do?

A
  • they detect small vibrations or changes in pressure
  • they contribute to the sensation of touch
  • they contain sensory nerve endings that are surrounded by layers of tissue called lamellae
34
Q

Describe the sequence of events that occur when the Pacinian corpuscle is stimulated.

A
  1. Pacinian corpuscle is stimulated and the lamellae become deformed
  2. the lamellae then press on the nerve ending, opening stretch-mediated sodium ion channels
  3. sodium ions diffuse into the cell through these ion channels which creates a generator potential
  4. if the generator potential exceeds the threshold potential then an action potential is triggered
35
Q

Describe photoreceptors and where they are found

A
  • found in the eye
  • sensitive to changes in the eye
  • as light enters the eye, photoreceptors are stimulated
  • light enters through the pupil and light is focussed onto the retina
36
Q

What are the 2 types of photoreceptors found in the eye?

A
  • rods and cones
  • rods are at the edge of the retina
  • cones are at the centre of the retina
37
Q

Which out of rods and cones are for colour and which is for general light?

A
  • rod cells are very sensitive to changes in light
  • they give a black and white image
  • cone cells are less sensitive to light but offer coloured images
  • there are 3 types of cone cell, each containing different optical pigments
38
Q

Why are rod cells sensitive to light and how does this affect their function?

A
  • several rod cells join to one sensory neuron
  • this means that generator potentials can be combined to exceed the threshold potential and trigger an impulse
  • helps in low light situations
39
Q

Why do rod cells have low visual acuity?

A
  • rod cells provide a low ability to tell 2 objects apart from one another when they’re close together
  • many rods join to the same sensory neuron
  • this means that the brain interprets these separate points as a single point
40
Q

How are cone cells much less sensitive to light than rod cells?

A
  • each cone cell is joined to a single sensory neuron
  • more light is required to reach the threshold potential so it is harder to trigger an impulse
41
Q

How do cone cells have a high visual acuity?

A
  • each cone cell is attached to its own sensory neuron so the brain interprets impulses from each cone cell as separate
  • this means that cone cells can offer much more visual detail than rod cells
42
Q

How can the nervous system be divided?

A
  • CNS and PNS
  • PNS into somatic (conscious) and autonomic (unconscious)
  • autonomic into sympathetic (fight or flight) and parasympathetic (rest and digest)
43
Q

One word to describe the heart

A
  • myogenic
  • it can contract and relax without receiving signals from the nervous system
44
Q

Describe the process of the heart beating

A
  1. heartbeat originates at the sinoatrial node (SAN)
    - SAN has the ability to spontaneously produce an electrical impulse
  2. SAN causes contraction in both atria
    - a band of collagen (non-conductive tissue) prevents impulses directly passing to ventricles
  3. impulses travel to the AVN which sends the impulse to the bundle of His
    - there is a short delay first to allow the atria to contract and empty fully
  4. bundle of His carries the impulse to the Purkinje fibres
    - the conductive purkinje fibres carry the impulse from the apex of the heart up both the ventricles simultaneously
    - both ventricles contract
45
Q

What part of the body controls the heart rate?

A
  • the brain
  • more specifically, the medulla oblongata
46
Q

Where are baroreceptors found?

A
  • aorta
  • carotid artery
47
Q

What does the medulla do when coordinating a response for heart rate?

A
  • the medulla coordinates a response when it receives impulses from the baro/chemo receptors via the sensory neurons
  • it sends impulses to the SAN via the sympathetic or parasympathetic neurons depending on the required outcome
48
Q

What is the difference between if the sympathetic or parasympathetic system is used to control heart rate?

A
  • sympathetic = speeds up
  • parasympathetic = slows down
49
Q

What can the control of heart rate also be described as?

A

NEGATIVE FEEDBACK
- the body responds to a stimuli to bring it back to the norm

50
Q

How is high blood pressure dealt with by the body?

A
  • baroreceptor detects
  • medulla sends an impulse through parasympathetic nervous system
  • HR slows
  • BP decreases
51
Q

How is low blood pressure dealt with by the body?

A
  • baroreceptor detects
  • medulla sends an impulse through the sympathetic nervous system
  • HR speeds up
  • BP increases
52
Q

How is a high blood pH dealt with by the body?

A
  • chemoreceptor detects
  • medulla sends an impulse through the parasympathetic nervous system
  • HR slows
  • pH decreases
53
Q

How is a low blood pH dealt with by the body?

A
  • chemoreceptor detects
  • medulla sends an impulse through the sympathetic nervous system
  • HR speeds up
  • pH increases

Biology (17 decks)

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