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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

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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
Q

What is the order of the reflex arc?

A

stimulus, sensory neurone, synapse, relay/interneurone, motor neurone, effector, response

26
Q

What does heartrate effect?

A

blood pressure

27
Q

What can affect heartrate?

A

-adrenaline
-nerve input

28
Q

How does adrenaline increase heartrate?

A

-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
Q

Which part of the brain holds the cardiovascular centre?

A

medulla oblongata

30
Q

What are the antagonistic nerves that connect the medulla oblongata to the heart?

A

sympathetic - speeds up
parasympathetic - slows down

31
Q

How do the nerves increase heartrate/stroke volume?

A

increase/decrease stimulation to the SAN and the frequency of the waves of excitation

32
Q

What are chemoreceptors sensitive to?

A

changes in the pH of blood

33
Q

What are baroreceptors sensitive to?

A

changes in blood pressure

34
Q

Where are the chemo and baro receptors?

A

both in carotid artery, chemo also in medulla/aorta and baro also in vena cava/aorta

35
Q

Describe the reflex arc for the chemoreceptors?

A

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
Q

Describe the reflex arc for the baroreceptors?

A

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
Q

What are photoreceptors?

A

light receptors that are found in the retina in the eye

38
Q

What is the fovea?

A

an area in the eye where lots of photoreceptors are found

39
Q

Why is there a blindspot?

A

where the optic nerve leaves the eye, so no photoreceptors

40
Q

What are the two types of photoreceptors in the eye?

A

rods and cones

41
Q

Describe rod cells?
(light sens, acuity, colour, number)

A

-very sensitive to light
-low visual acuity
-black and white only
-120 million in each eye

42
Q

Describe cone cells?
(light sens, acuity, colour, number)

A

-less sensitive to light
-high visual acuity
-colour vision - red/green/blue
-7 million in each eye

43
Q

Explain how we see very briefly

A

-light enters the eye and hits the photoreceptors
-the receptors are broken down (bleaching)

44
Q

How does the breakdown of rhodopsin cause a nerve impulse to be transmitted?

A

-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
Q

What cells have dark adaption?

A

rod cells

46
Q

What is the difference between bright and dim light for rods?

A

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
Q

What does acuity mean?

A

clearness/clarity

48
Q

Why do rods have high light sensitivity?

A

-many rods join 1 bipolar neurone (retinal convergence)
-many weak generator potentials combine to reach threshold and trigger an action potential

49
Q

Why do cone cells have low light sensitivity?

A

-only one cone cell connects to one bipolar neurone
-so more light is needed to reach threshold potential and trigger an action potential

50
Q

Why do rods have low visual acuity?

A

-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
Q

Why do cones have high visual acuity?

A

-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
Q

How do we see different colours?

A

-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
Q

Compare the distributions of rod cells and cone cells?

A

rod cells - all over including peripheral
cone cells - mainly in fovea

54
Q

Compare rod and cone cells with regards to retinal convergence?

A

rods - yes
cones - no

55
Q

Compare the names of the pigments in rods and cones?

A

rods - rhodopsin
cones - iodopsin

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

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