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bio topic 6 > stimulus and response > Flashcards

stimulus and response Flashcards

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Biology 101 flashcards
1
Q

Stimulus

A

A detectable change in the internal or external environment that is detected by a receptor and elicits a response

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2
Q

Response

A

Is a reaction to a stimulus

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3
Q

Reflex

A

Is a rapid, innate, automatic response

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4
Q

How does the ability to respond to stimuli increase the chance of survival for an organism? [2]

A
  • There is always a selection pressure favouring organisms with more appropriate responses
  • Those organisms that survive have a greater chance of raising offspring and of passing their alleles to the next generation.
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5
Q

Reflex Pathway [10]

A

Stimulus
Receptor
Sensory Neurone
Synapse
Relay / Intermediate Neurone
CNS
Synapse
Motor Neurone
Effector
Response

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6
Q

Neurone [2]

A
  • Long thin nerve fibre (axon)
  • With a cell body, containing nucleus
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7
Q

Where is the relay neurone?

A

Within the CNS

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8
Q

Which takes longer, transport through axons or across synapses?

A

Synapse

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9
Q

Importance of Reflex Arc [5]

A
  • Protect the body from harmful stimuli
  • Effective from birth and do not have to be learnt
  • Fast, as neurone
    pathway short with very few synapses, important in withdrawal reflexes
  • Involuntary, don’t use the decision making powers of the brain, free to carry out more complex responses
  • Some responses still sent to the brain, can sometimes over-ride the reflex if
    necessary.
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10
Q

Receptor [3]

A
  • The stimulus is always some form of energy
  • e.g. heat, light, sound or mechanical energy
  • All receptors convert the energy of the stimulus into a nerve impulse known as a generator potential
  • Acting as a transducer
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11
Q

Examples of Receptors [4]

A

Skin
- pain, temperature, pressure

Eye
- light

Ear
- soundwaves

Nose, Tastebuds
- chemicals

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12
Q

Pacinian Corpuscle [3]

A
  • Filippo Pacini
  • Receptors are specific to one type
    of stimulus only
  • Pacinian corpuscles are found throughout our skin and respond to change in mechanical pressure.
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13
Q

Pacinian Corpuscle Structure [3]

A
  • A single nerve fiber is surrounded by a myelin sheath
  • Which is surrounded by a capsule made of concentric rings of connective tissue (rings have nuclei)
  • separated by gel
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14
Q

Pacinian Corpuscle Role [6]

A
  • Pressure deforms the membranes and layers
  • Causing stretch-mediated sodium ion channels to open
  • Sodium ions diffuse through the layers to the neurone
  • Causing the inside of the membrane to be relatively more positive compared to the outside
  • Depolarising the membrane and creating a generator potential
  • If the generator potential is big enough an action potential occurs
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15
Q

Label the eye [14]

A

Sclera
Choroid
Vitreous humour
Retina
Fovea
Optic disk/blind spot
Optic nerve
Ciliary muscle
Iris
Lens
Conjunctiva
Cornea
Aqueous humour
Suspensory ligaments

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16
Q

Sclera [3]

A
  • The sclera is the white outer coating of the eye
  • It is tough, fibrous tissue
  • functions as the supporting wall of the eyeball, helps maintain eyeball shape, and protects it from injury
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17
Q

Choroid [2]

A
  • The choroid is a dense network of blood vessels between the retina and the sclera
  • supplies nutrition to the eye
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18
Q

Vitreous Fluid / Humour

A
  • The vitreous humor provides nutrients to your eye and helps your eye keep its shape
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19
Q

Retina [4]

A
  • A layer of photoreceptor cells within the eye
  • captures incoming photons and transmits them along neuronal pathways
  • as both electrical and chemical signals
  • for the brain to perceive a visual picture
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20
Q

Fovea

A
  • a small depression within the retina where visual acuity is the highest
21
Q

Optic Disc [3]

A
  • entry point for the major blood vessels that supply the retina
  • has fewer photoreceptors
  • making it the blind spot of the eye
22
Q

Optic Nerve [2]

A
  • an extension of the central nervous system
  • transmits electrical impulses from the eyes to the brain
23
Q

Ciliary Muscles [2]

A
  • relaxes and contracts to change shape of lens
  • important for moving the eyes as they place an image on the fovea to get maximum resolution
24
Q

Iris [2]

A
  • the colored part of the eye that surrounds the pupil
  • It regulates the amount of light that enters the eye
25
Q

Lens

A
  • clear part of the eye behind the iris that helps to focus light and images on the retina
26
Q

Conjunctiva

A
  • thin, clear membrane that protects the eye
27
Q

Cornea [3]

A
  • clear window on the front of your eye
  • made of tough, transparent tissue helps protect your eye
  • keeps out dirt, germs and other particles and, also filters out some of the sun’s ultraviolet (UV) light.
28
Q

Aqueous Humour [2]

A
  • give the eye its shape
  • nourishes the cornea and lens by supplying nutrition
29
Q

Suspensory Ligaments

A
  • series of fibers that connect the ciliary body of the eye with the lens, holding it in place
  • contract and relax to change shape of the lens and adjust visual acuity
30
Q

Photoreceptors [3]

A
  • found in the retina
  • there are two types: Rods and Cones
  • act as transducers
31
Q

Structure of Rod Cells [3]

A

DIAGRAM

32
Q

How do Rod Cells work? [4]

A
  • a number of rod cells are attached to a single bipolar cell creating a retinal convergence
  • so there is a much greater chance that the threshold
    value will be exceeded
  • this allows a generator potential to stimulate the bipolar cell and cause an action potential
  • as a result, rod cells allow us to see in low light intensity, although only in black and white
33
Q

Visual Acuity of Rod Cells [4]

A
  • As many rod cells are joined to the same bipolar cells, only a single impulse will be stimulated
  • This means that they cannot distinguish
    between the separate sources of light that stimulated them
  • 2 dots close together will appear as a single blob
  • Rod cells therefore have low visual acuity.
34
Q

Structure of Cone Cells

A

DIAGRAM

35
Q

Cone Cells

A

There are 3 types of cone cell, red sensitive, blue sensitive and green
sensitive
- Each responds
to different wavelengths of light
- Depending on the proportion of each type that is stimulated, we can
perceive images in full colour

36
Q

How do Cone Cells work? [5]

A
  • Cone cells contain the pigment (iodopsin)
  • This requires a higher light intensity to be hydrolysed to create a generator potential
  • Each cone cell usually has its own bipolar cell connected to a sensory neurone
  • This means that often the generator potential is not exceeded
  • As a result, cone cells only respond to high light intensity and not
    to low light intensity
37
Q

Visual Acuity of Cone Cells [2]

A
  • As cone cells are attached to their own bipolar cell, if 2 adjacent cells are stimulated, the brain receives 2 separate impulses
  • Cone cells give very accurate vision, they have good visual acuity
38
Q

Photoreceptors at the Fovea [6]

A
  • Light is focused by the lens on a point known as the fovea.
  • The fovea therefore receives the highest intensity of light.
  • Therefore cone cells, but not rod cells, are found at the fovea.
  • The concentration of cone cells diminishes further away from the fovea.
  • At the peripheries of the retina, where light intensity is at its lowest, only the rod cells are found
  • As each receptor responds to different light intensities
39
Q

Colour Blindness [3]

A
  • These people lack red sensitive cones
  • But the green sensitive cones are stimulated by the red light
  • So all dots appear green
40
Q

How many types of rod cell are there?

A

one

41
Q

How many types of cone cell are there?

A

three
(red, green, blue sensitive)

42
Q

How many rod cells are there?

A

Rod cells are more numerous than cones.

43
Q

How many cone cells are there?

A

Cone cells are less numerous than rods

44
Q

What is the distribution of rod cells in the retina?

A

More in periphery

45
Q

What is the distribution of cone cells in the retina?

A

Fewer in periphery, concentrated in fovea

46
Q

Describe rod cells sensitivity to light

A

High sensitivity

47
Q

Describe cone cells sensitivity to light

A

Low sensitivity

48
Q

What pigment is present in rod cells?

A

Rhodopsin

49
Q

What pigment is present in cone cells?

A

Iodopsin

bio topic 6 (8 decks)

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