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Biology- topic 6 organisms respond to changes in their internal and external environments > Responding to internal/external stimuli > Flashcards

Responding to internal/external stimuli Flashcards

1
Q

What is a reflex?

A

an involuntary response to a sensory stimulus

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2
Q

Why is a reflex arc important?

A

-protects body from harmful stimuli
-effective from birth/innate
-fast/immediate due to short neurone pathway
-invariable - always the same response

INNATE, IMMEDIATE, INVOLUNTARY, INVARIABLE

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3
Q

What makes up the central nervous system?

A

brain and spinal cord

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4
Q

What is a stimulus?

A

a change in the environment

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5
Q

What is a receptor?

A

detects the stimulus

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6
Q

What is an effector?

A

carries out a response - muscle or gland

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7
Q

What is a sensory neurone?

A

transmit electrical impulses from a receptor to the coordinator/CNS

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8
Q

What is a motor neurone?

A

transmit electrical impulses from the CNS to the effector

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9
Q

What is a nerve?

A

a bundle of neurones

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10
Q

What is a neurone?

A

a nerve cell

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11
Q

What are the spiky bits of the neurone?

A

dendrites

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12
Q

What are the bits between the myelin sheath called?

A

node of ranvier

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13
Q

What is the cell inside the myelin sheath called?

A

schwann cells

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14
Q

What is the autonomic nervous system?

A

part of the nervous system dealing with involuntary actions/responses

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15
Q

What is the difference between parasympathetic/sympathetic?

A

sympathetic - stimulates from normal level

parasympathetic - relaxes/reduces to normal level

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16
Q

What type of muscles make up the heart?

A

cardiac muscle

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17
Q

How would you describe cardiac muscle?

A

myogenic

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18
Q

What group of muscles beats at a higher frequency?

A

atrial

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19
Q

What is the small patch of tissue called in the right atrium that generates electrical

A
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20
Q

What is the muscle tissue that separates the two ventricles called?

A

non-conducting fibrous tissue

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21
Q

What is the tissue called that takes the excitation wave to the apex of the heart?

A

purkinje fibres

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22
Q

Where are the pacemaker cells?

A

SA node

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23
Q

Where is the Bundle of His?

A

in the middle, after the AVN node, splits into two branches

24
Q

Describe the story of a heartbeat

A

-SA node emits spontaneous impulses and they spread rapidly across both atria
-this stimulates a wave of contraction within the atrial walls - atrial systole
-when electrical impulses reach the border between the atria and ventricles, they are blocked by non-conducting fibrous tissue
-to reach the ventricles, electrical ventricles must pass through the AV node, which slows down the speed of electrical transmission
-this delay allows the atria to complete their contraction before the ventricles begin to contract
-impulses are conducted from the AV node along the Bundle of His
-the bundle fibres divide into numerous purkinje fibres that permeate through the ventricle muscles
-the spread of electrical impulses throughout the ventricles triggers ventricular systole from the apex of the heart up

25
What is the order of the reflex arc?
stimulus, sensory neurone, synapse, relay/interneurone, motor neurone, effector, response
26
What does heartrate effect?
blood pressure
27
What can affect heartrate?
-adrenaline -nerve input
28
How does adrenaline increase heartrate?
-secreted by the adrenal glands during stress -diffuses into blood -transported to target organs -stimulates SAN to increase frequency of waves of excitation/strength of contraction
29
Which part of the brain holds the cardiovascular centre?
medulla oblongata
30
What are the antagonistic nerves that connect the medulla oblongata to the heart?
sympathetic - speeds up parasympathetic - slows down
31
How do the nerves increase heartrate/stroke volume?
increase/decrease stimulation to the SAN and the frequency of the waves of excitation
32
What are chemoreceptors sensitive to?
changes in the pH of blood
33
What are baroreceptors sensitive to?
changes in blood pressure
34
Where are the chemo and baro receptors?
both in carotid artery, chemo also in medulla/aorta and baro also in vena cava/aorta
35
Describe the reflex arc for the chemoreceptors?
stimulus - increased CO2 in blood, causes a fall in pH receptor - chemoreceptors in carotid artery detect this coordinator - cardiovascular centre in medulla effector - increased impulses along sympathetic nerve to SAN, more waves of excitation response - increased heartrate, more blood moving, more CO2 removed
36
Describe the reflex arc for the baroreceptors?
stimulus - high blood pressure stretches the arteries receptor - baroreceptors found in carotid artery detect this coordinator - cardiovascular centre in medulla effector - increased impulses along the parasympathetic nerve to SAN, less waves of excitation response - decreased heartrate, decrease in blood pressure
37
What are photoreceptors?
light receptors that are found in the retina in the eye
38
What is the fovea?
an area in the eye where lots of photoreceptors are found
39
Why is there a blindspot?
where the optic nerve leaves the eye, so no photoreceptors
40
What are the two types of photoreceptors in the eye?
rods and cones
41
Describe rod cells? (light sens, acuity, colour, number)
-very sensitive to light -low visual acuity -black and white only -120 million in each eye
42
Describe cone cells? (light sens, acuity, colour, number)
-less sensitive to light -high visual acuity -colour vision - red/green/blue -7 million in each eye
43
Explain how we see very briefly
-light enters the eye and hits the photoreceptors -the receptors are broken down (bleaching)
44
How does the breakdown of rhodopsin cause a nerve impulse to be transmitted?
-rhodopsin breaks down into opsin -opsin causes a change in the permeability of the rod cell to sodium, which initiates a generator potential -a nerve impulse is sent
45
What cells have dark adaption?
rod cells
46
What is the difference between bright and dim light for rods?
bright - rhodopsin is broken down faster than it is reformed so is of little use dim - breakdown of rhodopsin is lower, so production keeps up with breakdown
47
What does acuity mean?
clearness/clarity
48
Why do rods have high light sensitivity?
-many rods join 1 bipolar neurone (retinal convergence) -many weak generator potentials combine to reach threshold and trigger an action potential
49
Why do cone cells have low light sensitivity?
-only one cone cell connects to one bipolar neurone -so more light is needed to reach threshold potential and trigger an action potential
50
Why do rods have low visual acuity?
-retinal convergence, many rods join 1 bipolar neurone -so light from 2 points cannot be seen as separate as brain doesn't know EXACTLY where it came from
51
Why do cones have high visual acuity?
-1:1 ratio of cone:bipolar neurone -when light from two points hits two cones, both send an action potential to the brain, so it is able to distinguish between both points
52
How do we see different colours?
-we have three types of cone cell -each have a different type of iodopsin that responds to a different wavelength of light -colour seen depends on the relative degree of stimulation of the different types of cone cell
53
Compare the distributions of rod cells and cone cells?
rod cells - all over including peripheral cone cells - mainly in fovea
54
Compare rod and cone cells with regards to retinal convergence?
rods - yes cones - no
55
Compare the names of the pigments in rods and cones?
rods - rhodopsin cones - iodopsin

Biology- topic 6 organisms respond to changes in their internal and external environments (6 decks)

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