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Biology IGCSE > 2. Structure and function in living organisms - (j) Coordination > Flashcards

2. Structure and function in living organisms - (j) Coordination Flashcards

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1
Q

How do organisms respond to changes in the environment?

A
  • All living organisms need to respond to changes in environment for survival
  • Nervous system coordinated by the Brain allows body to respond to changes in environment
  • Organisms additionally have reflexes for fast involuntary actions that protect body from damage
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2
Q

What factors do we need to respond to the environment and what are they?

A

STIMULI - Change in environment

RECEPTOR - Specialised cells that detect changes in environment E.g, Sensory Neurones in the finger detect heat

EFFECTOR - Part of body that carries out response to Stimuli E.g Muscles in finger that contract to pull finger away from heat

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3
Q

What is homeostasis?

A

Maintaining a constant internal environment despite the external change so that enzymes can function at optimal conditions.

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4
Q

What is osmoregulation?

A

Maintenance of constant Water level in the body. It is an example of homeostasis.

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5
Q

What is thermoregulation?

A

Control of body temperature to ensure the optimum temperature for enzymes. It is an example of homeostasis.

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6
Q

How does the body keep it body temperature constant?

A

decrease in body temperature —> shivering, vasoconstriction —> increase in body temperature —> normal body temperature

increase in body temperature —> increased sweating, vasodilation —> decrease in body temperature —> normal body temperature

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7
Q

What is a coordinated response?

A

Process in which a reaction is carried out in response to a change in environment (stimuli)

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8
Q

What does a coordinated response involve?

A

a stimulus, a receptor and an

effector

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9
Q

How do plants respond to stimuli?

A

Plants are living organisms and therefore respond to change in environment (stimuli) for Survival E.g Abiotic Factors Such as Light, Water and and Biotic Factors such as Predators

  • Abiotic Factors: Water, light
  • Biotic Factors: Predators, Disease (Fungi and Bacteria)

Plants respond to stimuli by producing Auxin - a growth hormone, which controls the direction of growth of roots and stems

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10
Q

What are the 3 types of stimuli (plants)?

A

GRAVITY - Geotropism
LIGHT - Phototropism
WATER - Hydrotropism

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11
Q

What is a geotropic response and what part of the plant is positively geotropic?

A

Growth in response to the direction of gravity. The roots grow down in the same direction to the pull of gravity to get more minerals ions and anchor the plant.

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12
Q

What is a phototropic response and what part of the plant is positively phototropic?

A

Growth in response to the direction of light. The shoots grow towards the light in order to photosynthesise as much as possible.

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13
Q

What are auxins?

A

Plant hormone produced in the tip of stem and roots which controls the direction of growth

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14
Q

How does auxin cause the shoot to grow towards the light?

A
  • Auxin collets on the shading side
  • Auxin promotes cell growth
  • The shoot curves towards the light
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15
Q

How does negative geotropism occur?

A
  • During growth, Auxin produced at the tip will accumulate on the underside of the Stem due to gravity
  • As Auxins promote the growth of Stem cells, cells on the underside of the Stem will continue to grow larger and elongate (increase in elasticity allows cell to absorb more Water to grow larger in size), whilst cells on the upperside will grow at a slower rate
  • As a result, Stem will grow upwards against the direction of gravity - Negative Geotropism
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16
Q

How does negative phototropism occur?

A
  • During growth, Auxin produced at the tip will accumulate on the underside of the Stem due to gravity
  • As Auxins promote the growth of Stem cells, cells on the underside of the Stem will continue to grow larger and elongate (increase in elasticity allows cell to absorb more Water to grow larger in size), whilst cells on the upperside will grow at a slower rate
  • As a result, Stem will grow upwards against the direction of gravity - Negative Geotropism
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17
Q

What are 4 difference between the nervous system and the endocrine system?

A
  • Communication is via impulses that travel down neurons (nervous system), via hormones in the blood (endocrine system).
  • The response happens instantly (nervous system), the response can take a long time (endocrine system)
  • The response is short-lived (nervous system), the response can take a long time (endocrine system)
  • The impulse acts on one or a few cells only (nervous system), hormones can have a widespread affect on any cells and organs
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18
Q

Where is auxin produced?

A

It is produced at the tip of the shoot and diffuses downwards. It is evenly distributed so the shoot will grow evenly. Causes cell division and elongation.

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19
Q

What is the central nervous system?

A

Nervous system comprising the Brain and Spinal Cord that is linked to a network of nerve cells that carry impulses around the body

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20
Q

Describe the process of the CNS responding to a stimuli:

A
  • Central Nervous System (CNS) determines the response for a stimulus detected by the receptor
  • Stimuli is detected by receptors, stimulating Sensory Neurons that send electrical impulses to the Central Nervous System - Brain and Spinal cord
  • Central Nervous System relays impulse across the synpase (gaps between Neurones) to Relay Neurons via synaptic transmission
  • Relay Neurons relays impulse to Motor Neurons in the Effector, which will quickly carry out rapid response
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21
Q

What are neurons?

A

they are used in order to carry electrical impulses at rapid speeds around the nervous system to send electrical impulses to and from effectors and recpetos.

22
Q

What are the 3 different kinds of neurones?

A
  • sensory
  • motor
  • relay
23
Q

What do the sensory neurones do?

A

they pick up the signal from the receptors and they carry the signal into the CNS

24
Q

What do the relay neurones do?

A

Just inside the CNS and like a relay to coordinate what is going on, they might pass the signal around a few times and make different connects in your brain or spinal cord. At some point they will send a signal back out down the motor neurone.

25
Q

What do motor neurones do?

A

This is the neurone that ends up causing the effect by sending a signal to the effector (a muscle or a gland)

26
Q

What is a synapses?

A

Junction that separates Neurons from other cells (other Neurons and Receptor or Effector cells)

27
Q

What is a neurotransmitter?

A

Chemical messengers that are released from Neurons to transmit signals across the Synapse

28
Q

How does the electrical impulse get over the synapses?

A

As electrical impulses cannot pass across the Synapse, Neurons transmit information across by converting the electrical signal into a chemical signal called Neurotransmitters

29
Q

Explain synaptic transmission:

A
  • When an electrical impulse reaches the end of an Axon on pre-synaptic Neuron, this triggers the release of chemical messengers called Neurotransmitters via exocytosis
  • Neurotransmitter will diffuse across the Synapse and bind to receptors on the membrane of the post-synaptic Neuron
  • As a result, post-synaptic Neuron continues to transmit electrical impulse along Axon of Neuron
30
Q

What is a reflex response?

A

theyare automatic and rapid as the things you are responding to are dangourous. This responses prevent you from getting ingured or dying. e.g. the iris constricting in the light and touching something hot.

31
Q

How does the body react to touching something hot?

A
  • When Hand is near a hot object, heat (stimuli) is detected by the Finger (receptor), stimulating Sensory Neurons to send electrical impulses to the Central Nervous System - Brain and Spinal Cord
  • Central Nervous System will receive and interpret message, determining the appropriate reaction of pulling hand away from the hot object
  • This impulse is relayed across the Synpase to Relay Neurons via synaptic transmission
    Relay Neurons relays impulse to Motor Neurons in the Bicep
  • As a result, Bicep will contract to quickly draw hand away from the heat, allowing a rapid response to prevent harm to the body
32
Q

What is the cornea?

A

Transparent convex lens that refracts light (where light first enters the eye). protects the eye.

33
Q

What is the iris?

A

Pigmented membrane that controls the diameter and size of Pupil to alter the quantity of light reaching the Retina (controls how much light enters the pupil)

34
Q

What is the lens?

A

Transparent disc that changes shape to focus light onto the Retina

35
Q

What is the retina?

A

Light-sensitive nerve tissue containing Rods (night vision) and Cones (colour vision) to convert light into electrical impulses to be interpreted by the brain for visual recognition

36
Q

What is an optic nerve?

A

Nerve located in the back of the eye that contains Sensory Neurons to send electrical impulses to be interpreted by the brain for visual recognition

37
Q

What is the pupil?

A

Opening in the centre of Iris that allows light to enter the Eye

38
Q

What are the ciliary muscles?

A

Circular muscle surrounding the lens that that contracts and relaxes to adjust the thickness of lens

39
Q

What is the choroid?

A

It is black and stops any internal reflection of light and has all the blood vessels which supply the eye with the blood it needs.

40
Q

What is the fovea?

A

Area of the retina with the highest concentration of cone cells that provides sharp vision.

41
Q

What happens to the iris when the light is bright?

A
  • When in bright environment, Photoreceptors - Rods and Cones, detect the change in light intensity
  • circular mucles contract
  • radial muscles relax
  • pupils constrict to allow less light to enter the eye
42
Q

What happens to the iris in dim light?

A
  • When in dark environment, Photoreceptors - Rods and Cones, detect the change in light intensity
  • ciricular muscles relax
  • radial muscles contract
  • pupils dilates to allow more light to enter the eye
43
Q

How does the eye focus on a distant object?

A
  • ciliary muscles relax
  • suspnsory ligaments tighten
  • lens is pulled thin and less curved, refracting light rays less strongly to converge on the Retina
44
Q

How does the eye focus on a close object?

A
  • ciliary mucles contract
  • suspensory ligaments slacken
  • lens becomes fatter and more curved, refracting light rays more strongly to converge on the Retina
45
Q

What is the role of the skin when the body is too hot?

A
  • When in hot environment, increase in body temperature is detected by Thermoreceptors As a result, series of changes occurs in body via thermoregulation
  • Blood vessels near skin dilate via Vasodilation to increase blood flow to surface for heat loss
  • Sweat glands excrete sweat to cool skin via evaporative cooling
  • Hair Erector Muscles relax to lower Skin hair, trapping a thin insulating layer of air above the Skin for heat loss
46
Q

What is the role of the skin in a cold environment?

A
  • When in Cold environment, decrease in body temperature is detected by Thermoreceptors As a result, series of changes occurs in body via thermoregulation
  • Blood vessels near skin contract via Vasoconstriction to reduce blood flow to surface to minimise heat loss
  • Sweat glands do not excrete sweat to prevent evaporative cooling
  • Hair Erector Muscles contract to raise Skin hair, trapping a thick insulating layer of air above the skin to prevent heat loss
47
Q

What is the hormone adrenalines source, role, and effect?

A

Source: Adrenal glands
Role: Prepares body for ‘fight or flight’ response
Effects: Increases heart rate, blood sugar levels, blood flow to muscles and breathing rate

48
Q

What is the hormone insulin source, role, and effect?

A

Source: pancreas
role: controls blood sugar levels
Effects: Stimulates glucose to be stored as glycogen in the liver

49
Q

What is the hormone testosterone’s source, role and effect?

A

Source: Testes
Role: Male sex hormones
Effect: Increased levels initiate development of secondary sexual characteristics

50
Q

What is the hormone progesterone source, role and effect?

A

Source: Ovaries
role: Primary sex hormone in females to maintain pregnancy (supports pregnancy)
Effects: Maintains the Uterus lining to cushion fertilised Egg cell

51
Q

What is the hormone oestrogen’s source, role, and effect?

A

Source: Ovaries
Role: Primary sex hormone in Females
Effects: Increased levels initiate development of secondary sexual characteristics including the menstrual cycle

Biology IGCSE (10 decks)

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