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Biology Year 2 > Response to stimuli > Flashcards

Response to stimuli Flashcards

1
Q

What is a stimulus

A

a detectible change in the internal or external environment of an organism that results in a response

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2
Q

How is a stimulus detected

A

by receptors that are specific to one type of stimulus

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3
Q

What are the sequence of events that happen that result in a response

A
  • stimulus
  • receptor
  • coordinator
  • effector
  • responce
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4
Q

What is a taxes and what are types of taxis

A

a simple response whose direction is determined by the direction of the stimulus

  • positive phototaxis - plants towards light
  • negative phototaxis - away from light and predators
  • positive chemotaxis - towards glucose source
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5
Q

What is a kineses and what are types of kinesis

A

a form of response where organisms doesn’t move towards or away, instead it changes the speed in which it changes direction

-the further away from its favourable environment the faster it changes direction to go back

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6
Q

What is a tropism and what are types of tropisms

A

the growth of a part of a plant in response to a directional stimulus

  • plant grows towards light for photosynthesis - positive phototropism - negative gravitropism
  • plant roots grow away from the light for water -positive hydrotropism - negative phototropism - positive gravitropism
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7
Q

How does a shoot grow towards light

A
  • cells in the tip of the shoot produce IAA which is transported down the shoot
  • light causes IAA to move from the side exposed to light to the shaded side of the shoot
  • greater concentration of IAA builds up on the shaded side
  • IAA causes the elongation of shoot cells on the shaded side
  • the shaded side shoot cells elongate faster than the light side thus the shoot grows towards the light
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8
Q

How does a root grow horizontally into the soil

A
  • cells in the tip of the root produce IAA which is transported along the root
  • gravity causes the IAA to move from the upper to the lower side of the root
  • greater concentration of IAA builds up on the lower side
  • IAA inhibits the elongation of root cells so the cells on the lower side elongate less
  • the cells on the upper side elongate more than the lower side thus the root bends down towards the force of gravity
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9
Q

How does IAA increase plasticity of cells

A

it involves the active transport of hydrogen from the cytoplasm into spaces in the cell walls causing the cell wall to become more plastic allowing the cell to elongate

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10
Q

How is the role of IAA discovered

A
  • by having a control
  • covering one shoot with a light proof cover
  • cutting off the shoot tip
  • inserting a impermeable barrier of mica
  • gelatin block inserted under the tip
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11
Q

What is the central nervous system made up of

A

the brain and the spinal cord

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12
Q

What is the peripheral nervous system make up of

A

pairs of nerves that originate from either the brain or the spinal cord

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13
Q

What is the peripheral nervous system divided into

A

sensory neurones - carry nerve impulses form receptors towards the central nervous system

motor neurones - carry nerve impulses from the central nervous system to the effectors

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14
Q

What can the motor nervous system be divided into

A

voluntary nervous system - under VOLUNTARY (conscious) control which carries nerve impulses to body muscles

automatic nervous system - under INVOLUNTARY (subconscious) control which carries nerve impulses to glands, smooth muscle and cardiac muscle

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15
Q

What is the process of an arc reflex (involuntary response) when a hot object is touched with a hand

A
  • stimulus - heat from hod object
  • receptor - temperature receptors in hand generate nerve impulse
  • sensory neurone - passes nerve impulse to the spinal cord
  • coordinator (intermediate neurone) - links the sensory to motor neurone in the spinal cord
  • motor neurone - carries nerve impulse to muscle in the arm
  • effector - muscle gets stimulated to contract
  • the response - hand pulled away
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16
Q

What are the importances of arc reflexes

A
  • involuntary thus don’t require decision from brain so that it’s not overloaded decisions
  • they are fast because neurone pathway is short and no decision making process
  • don’t have to be leant
17
Q

How does the pacinian corpuscle convert energy from a stimulus into a generator potential

A
  • when pressure is applied the pacinian corpuscle deforms and the membrane around the neurone stretches widening the sodium ions channels
  • the influx of sodium ions changes the neurones membrane potential and becomes depolarised
  • producing a generator potential which creates an action potential which passes along neurone to the central nervous system
18
Q

What state is the pacinian corpuscle at resting

A

the stretch-mediated sodium channels of the membrane around the neurone ending are to narrow to allow sodium ions through

19
Q

Why are there three rod cells connected to a single bipolar neurone

A

because rod cells detect very low light intensities a certain threshold has to be exceeded before a generator potential is created in the bipolar cells, which cant be done by cone rod cell

20
Q

What is the pigment in rod cells which is needed to be broken down to create a generator potential

A

rhodopsin

21
Q

What are rod cells

A

one type of cell distributed more at the periphery of the retina which give low visual acuity and cant distinguish different wavelengths of light which lead to images being in black and white

22
Q

What are cone cells

A
  • three types of cells each responding to different wavelengths of light, fewer at the periphery concentrated at the fovea
  • each type contain a type of iodopsin which are sensitive to a specific range of wavelengths
  • each cone cell has a connection to a single bipolar neurone connected to a sensory neurone on the optic nerve giving high visual acuity
23
Q

Whats is the autonomic nervous system

A

controls the involuntary (subconscious) activities of internal muscles and glands

24
Q

What are the two types of autonomic nervous system

and what are they

A

sympathetic nervous system - stimulates the effectors and speeds up activity to help cope in stressful situations

parasympathetic nervous system - inhibits the effectors and slows the activity under relaxing conditions for conserving the body’s reserves

antagonistic - they normally oppose one another

25
Q

Where is the myogenic contraction of the heart initiated from

A

sinoatrial node (SAN) cells in the right atrium which has a basic rhythm of stimulation

26
Q

What are the sequence of events that control hear rate

A
  • wave of electrical excitation spreads from the sinoatrial node across both atria causing them to contract
  • the non-conductive atrioventricular septum prevents wave from spreading to the ventricles
  • then the excitation enders the atrioventricular node (AVN) cells which lie between the atria
  • after a short delay the wave of electrical excitation is passed along the PURKYNE tissue which make up the BUNDLE of His
  • the BUNDLE of His conducts the wave through the atrioventricular septum to the base of the ventricles to smaller fibres of PURKYNE tissue
  • the wave of excitation gets released causing the ventricles to contract from the bottom upwards
27
Q

Where are changes to heart rate controlled and why

A

in the Medulla Oblongata which has two centres:

  • increases the heart rate which is linked to the sinoatrial node by the sympathetic nervous system and increased blood flow removes carbon dioxide from exercise faster
  • decreases the heart rate which is linked to the sinoatrial node by the parasympathetic nervous system
28
Q

Where are chemoreceptors found and what are they sensitive to

A

in the wall of the carotid arteries and are sensitive to the changes in pH in the blood due to carbon dioxide concentrations

29
Q

What is the process of the action of chemoreceptors

A
  • when the blood has a higher level of carbon dioxide than normal the ph is lowered
  • the chemoreceptors detect this and increase the frequency of nervous impulses to the medulla oblongata
  • this increases the frequency of impulses via the sympathetic nerve to the sinoatrial node and increases heart rate
  • this causes more carbon dioxide to be removed from the lungs so blood carbon dioxide an pH levels return to normal
  • the chemoreceptors then reduce the frequency of nerve impulses to the medulla oblongata and reduces the heart rate

Biology Year 2 (12 decks)

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