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biology > Biology Topic 6.1: stimuli and response > Flashcards

Biology Topic 6.1: stimuli and response Flashcards

- survival and response - nervous communication - response in plants - receptors - control of heart rate

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1
Q

what do receptors do

A

convert the energy of the stimulus into the electrical energy used by neurones

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2
Q

what are types of receptors

A

ex: photoreceptors that connect to nervous system

ex: glucose receptors are proteins found in the cell membrane of pancreatic cells

specific to a stimulus and different types

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3
Q

what are the stages of how a receptor works

A
  • resting potential
  • the generating potential
  • the action potential
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4
Q

what occurs in the resting potential

A
  • difference in charge between inside and outside of cell (inside = negative)
  • means there is a voltage (potential difference) across the membrane
  • potential difference when is a cell is at rest =. resting potential
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5
Q

what is the resting potential generated by

A

sodium - potassium pumps and potassium ion channels

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6
Q

what occurs in generator potential

A
  • stimulus detected

-cell membrane is excited = becomes more permeable

  • more ion movement inside and outside
  • alters potential difference
  • a larger stimulus = larger movement of ions = larger generator potential
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7
Q

what is the generator potential

A

change in potential difference due to a stimulus

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8
Q

what is the action potential

A

-big enough generator potential = reached certain threshold = triggers action potential

  • strength of a stimulus measured on frequency of action potential as action potential are all one size
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9
Q

what is the action potential

A

an electrical impulse along a neurone

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10
Q

what type of stimuli does the pacinian corpuscles detect

A

mechanical stimuli

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11
Q

what stimulus does the pacinian corpuscles work on

A

pressure and vibrations

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12
Q

where is the pacinian corpuscles found

A

found in the skin

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13
Q

what is the structure of the pacinian corpuscles

A

contains end of sensory neurone = sensory nerve ending

sensory nerve ending wrapped in loads of layers of connective tissue = lamellae

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14
Q

how does the pacinian corpuscle work

A

lamellae deforms = presses on sensory nerve ending

sensory neurone cell membrane to stretch

deforms stretch-mediated sodium ion channels

channel opened sodium ion diffuses into the cell = creating generator potential

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15
Q

what is the structure of the back of the eye

A

retina = contains many photoreceptor cells

fovea = area of retina with lots of photoreceptor cells

optical nerve = carries nerve impulses from retina to brain
optic nerve is a bundle of neurons

blind spot - area where optic nerve leaves the eye= no photoreceptor cells = not sensitive to light

bipolar neurones = connect photoreceptors to optic nerve

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16
Q

how does the eye detect light to control the iris?

A
  • light hits the photoreceptors
  • and absorbed by light-sensitive optical pigments
  • light bleaches pigments
  • causes chemical change = alters permeability of membrane
  • generates a generator potential
  • if threshold reached nerve impulse sent a;ong bipolar neurone
  • then sent to brain via the optic nerve
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17
Q

what are the types of photoreceptors

A

rods and cones

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18
Q

where are the rods found

A

peripherel part of retina

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19
Q

where are cones found

A

packed together in the fovea

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20
Q

what is the difference between the rods and cones

A
  • contain different optical pigments = sensitive to different wavelengths
  • rods give info. in black and white (monochromatic)

-cones give info. in colour (trichromatic vision)

-rods are sensitive to light

-cones less sensitive to light

-rods give low visual acuity

  • cones have a high visual acuity

rods found on peripheral mainly

cones found in fovea

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21
Q

what are the three types of cones

A
  • red sensitive
  • green sensitive
  • blue sensitive
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22
Q

why do rods work well in dim light

A

rods are sensitive to light as many rods join one bipolar neuron therefore many weak generator potentials combine to reach threshold

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23
Q

why do cones work better in brighter light

A

less sensitive to light as one cone joints one bipolar neuron so it takes more light to reach threshold

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24
Q

why do rods give low visual acuity

A

many rods join one bipolar neurone so light from two points close together can’t be told apart
brain doesn’t get separate info.on two close points

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25
Q

why do cones have a high visual acuity

A

light from two points hits two cones = two action potential go to brain so two separate points can be distinguished

26
Q

what does the somatic nervous system and automatic nervous system control and which main system is it apart of

A

-the peripheral nervous system
-controls conscious activities = somatic
- controls unconscious activities = automatic

27
Q

what is the autonomic nervous system split into

A

sympathetic and parasympathetic

28
Q

what is the sympathetic nervous system

A

fight or flight mode = gets body ready for action

29
Q

what does the parasympathetic nervous system control

A

‘rest and digest’ system = calms the body down

30
Q

what does myogenic mean

A

means that it contracts and relaxes without receiving signals from nerves (heart muscles)

31
Q

where is the SAN (sinoatrial node) found and what is it

A

found in wall of the right atrium
it is a small mass of tissue

32
Q

what does the SAN do

A

like a pacemaker
sets rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls = contraction of right and left at same time

33
Q

what stops the electrical impulse of the SAN causing the ventricles to contract

A

a band of non-conducting collagen tissue prevents the waves of electrical activity to be passed from atria to ventricles

instead passed from SAN to AVN (atrioventricular node) directly

34
Q

what does the AVN do

A

passes the waves of electrical activity on to the bundle of His

35
Q

why is there a slight delay before the AVN reacts

A

to make sure the atria have emptied before ventricles contract

36
Q

what is the bundle of His

A

a group of muscle fibres
responsible for conducting the waves of electrical activity between ventricles to the apex (bottom of heart)

37
Q

how does the bundle of His conduct the waves of electrical activity between ventricles to the apex

A

bundle of His splits into finer fibres in right and left ventricles = Purkyne tissue

purkyne tissues carries electrical activity into muscular walls of right and left ventricles = contract simultaneously from bottom up

38
Q

what control the rate at which the SAN fires

A

the medulla

39
Q

what are internal stimulus detected by

A

pressure and chemical receptors

40
Q

what are pressure receptors called and where are they found and what are they stimulated by

A

called baroreceptors in aorta and carotid arteries (major arteries in the neck)

stimulated by high and low blood pressure

41
Q

what are chemical receptors called and where are they found and what are they stimulated by

A

chemoreceptors in the aorta, carotid arteries and in medulla

monitor oxygen levels in blood and carbon dioxide and PH

42
Q

what is the process of controlling the heart rate when there is a high blood pressure

A

baroreceptors detect it

send impulses along sensory neurons to medulla

which send impulses along parasympathetic neurons

these secrete acetylcholine

which binds to receptors on SAN

this causes heart rate to slow down

43
Q

what is the process of controlling the heart rate when there is a low blood pressure

A

baroreceptors detect it

send impulses along sensory neuron to medulla

sends impulse along sympathetic neuron

these secrete noradrenaline

binds to receptors on SAN

causes heart rate to speed up

44
Q

what are acetylcholine and noradrenaline

A

types of neurotransmitters

45
Q

what is the process of controlling the heart rate when there is a high blood oxygen,low carbon dioxide, high blood PH levels

A

chemoreceptors detect chemical change in blood

send impulses along sensory neurone to medulla

send impulse along parasympathetic

which secret acetylcholine

bind to receptors on SAN

causes heart rate to decrease

46
Q

what is the process of controlling the heart rate when there is a low blood oxygen,high carbon dioxide, low blood PH levels

A

chemoreceptors detect chemical change in blood

send impulses along sensory neuron to medulla

send impulse along sympathetic

which secret noradrenaline

bind to receptors on SAN

causes heart rate to increase

47
Q

during resting potential what is the movement of the sodium- potassium pump and the potassium channel

A
  • sodium- potassium pump uses active transport
  • moves 3 sodium ions out and two potassium in
    -membrane not permeable to sodium ions so sodium ions cannot diffuse back in
    -creates a electrochemical gradient = a concentration gradient of ions as it is more positive sodium ions outside than inside
  • potassium ion channels allow facilitated diffusion of potassium ions out of neuron down concentration gradient
    (more negative inside the cell)
  • at rest more potassium ion channels open= cell membrane is permeable to potassium ions so some diffuse back out through potassium ion channels

-high proportion of ions move out then enter so outside of cell is positive

48
Q

what is the stages of the change in potential difference across a neuron cell membrane during an action potential

A

stimulus
depolarisation
repolarisation
hyperpolarisation
resting potential

49
Q

what is the change in potential difference across a neuron cell membrane during an action potential

stimulus stage

A
  • stimulus excites neurons cell membrane = more permeable

-sodium ions diffuse into neuron down electrochemical gradient

-inside of neuron less negative

50
Q

what is the change in potential difference across a neuron cell membrane during an action potential

depolarisation stage

A

if potential difference = threshold

more sodium ion channels open

more sodium ions diffuse into neuron

51
Q

what is the change in potential difference across a neuron cell membrane during an action potential

repolarisation stage

A

at P.D of around +30mV
the sodium ion channels close otherwise membrane would remain depolarised

potassium ions channels open

membrane more permeable to potassium

so potassium diffuses out of neuron down conc. gradient

strats to get back to resting potential

52
Q

what is the change in potential difference across a neuron cell membrane during an action potential

hyperpolarisation stage

A

potassium ion channels slow to close
= slight ‘overshoot’
where too many potassium ions diffuse out of neuron

P.D becomes more negative than resting potential

53
Q

what is the change in potential difference across a neuron cell membrane during an action potential

resting potential stage

A

ion channels are reset

sodium -potassium pump returns membrane to its resting potential by pumping sodium ions out and potassium ions in

maintains resting potential until another stimulus excites membrane

54
Q

what is the refractory period

A

after action potential neuron cannot be excited again right away

ions channels are recovering

55
Q

what is the wave of depolarisation

A

some of the sodium ions that enter the neuron go sideways triggering the sodium ion channel to open in another part of the neuron creating a wave of depolarisation

this wave moves away from the area under the refractory period

56
Q

what is the all or nothing principle

A

once threshold is reached an action potential will always fire with the same change in voltage no matter how big stimulus is

a bigger stimulus will cause the action potential to be fired more frequently and will not cause a bigger action potential

57
Q

what are the factors affecting the speed of conduction of the action potential

A

myelination
axon diameter
temperature

58
Q

what is the structure of the neurons in the peripheral nervous system

A

in peripheral nervous system the myelin sheath is made up of a cell called a Schwann cell
between schwann cells = tiny bare patches called nodes of ranvier

sodium ion channels concentrated at nodes of ranvier

59
Q

how does myelination affect the speed of conduction of the action potential

A

saltatory conduction occurs

-depolarisation only happens at the nodes of ranvier in a myelinated neuron

  • neurons cytoplasm conducts enough electrical charge to depolarise the next node - so impulse jumps node to node

on non-myelinated neuron impulse travels as wave along the whole length of axon
depolarisation occurs through whole length
this process is slower than saltatory conduction

60
Q

how does the axon diameter affect the speed of conduction of the action potential

A

action potential conduction is quicker in axons with larger diameters
- less resistance to the flow of ions than in cytoplasm of smaller axon
- depolarisation can reach other parts of neuron quicker therefor

61
Q

how does the temperature affect the speed of conduction of the action potential

A

speed of conduction increases and temperature increases

bc ions diffuse faster

after around 40 degrees protein begins to denature and speed decreases

biology (10 decks)

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