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Biology > 6 - Coordination and Responding to Stimuli > Flashcards

6 - Coordination and Responding to Stimuli Flashcards

1
Q

What is a stimulus?

A

Any change in the internal or external environment

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2
Q

What are receptors?

A
  • Detect a stimulus
  • Receptors in the sense organs are groups of cells that detect external stimuli
  • e.g. Rod and cone cells in the eye detect changes in light
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3
Q

What are effectors?

A
  • Cells that bring about a response to a stimuli
  • Include muscle cells and cells found in glands (e.g. the pancreas)
  • Effectors respond in different way (muscles contract whereas glands secrete hormones)
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4
Q

How do receptors and effectors communicate?

A

Via the nervous system, the hormonal system or both

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5
Q

What are sense organs?

A

The eyes, ears, nose, tongue and skin

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6
Q

What is the CNS?

A
  • Central nervous system
  • Made of neurons
  • Consists of the brain and spinal chord only
  • The job is to coordinate a response
  • The high speed electrical impulses produce a rapid response
  • When receptors detect and stimulus they send electrical impulses along sensory neurons to the CNS
  • The CNS sends electrical impulses to an effector along a motor neuron
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7
Q

What are the neurons in the CNS?

A

Sensory, Relay, Motor

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8
Q

What are reflexes?

A

Automatic responses to certain stimuli which reduce changes of being injured
e.g. if a bright light is shone in the eye the pupil automatically get smaller to stop them being injured

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9
Q

Give an example of the reflex arc

A
  • Cupcake candle burns finger
  • Stimulation of pain in the receptors
  • Impulses travel along the sensory neuron
  • Impulses are passed along a relay neuron via a synapse
  • Impulses travel along a motor neuron via a synapse
  • When impulses reach muscles it contracts
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10
Q

What is the reflex arc?

A

Stimulus - Receptor - Sensory neuron - relay neuron - Motor Neuron - Effector - Response

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11
Q

What is the reflex arc?

A

Stimulus - Receptor - Sensory neuron - relay neuron - Motor Neuron - Effector - Response

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12
Q

What is the role of the cornea?

A

Refracts light into the eye

- Transparent with no blood vessels to supply it with oxygen so oxygen diffuses in from the outer surface

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13
Q

What is the role of the conjunctiva?

A

Lubricates and protects the surface of the eye

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14
Q

What is the role of the iris?

A

Controls the diameter of the pupil allowing how much light is let in

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15
Q

What is the role of the lens?

A

Focuses light on the retina (the light-sensitive part covered in light receptors called rods and cones)

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16
Q

Rods and Cones

A

Rods - more sensitive in dim light but can’t sense colour

Cones - sensitive to colours but aren’t so good in dim light. Found all over the retina but are loads at the fovea

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17
Q

What is the role of the optic nerve?

A

Carries impulses from the receptors to the brain

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18
Q

How does the eye adjust to bright light?

A
  • Bright light triggers a reflex that makes the pupil smaller, allowing less light in
  • Light receptors detect light and send a message along sensory neurons to the brain. The message travels along a relay neuron to a motor neuron which tells circular muscles to contract
  • The opposite happens in dark light
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19
Q

How does the eye look at distant objects?

A
  • Ciliary muscles relax
  • Suspensory ligaments pull tight
  • This makes the lens go thin (less curved)
20
Q

How does the eye look at near objects?

A
  • Ciliary muscles contract
  • Slackens the suspensory ligaments
  • The lens becomes fat (more curved)
21
Q

Long-sighted people

A
  • Unable to focus on near objects
  • The cornea or lens doesn’t bend the light enough or the eyeball is too short
  • The images of near objects are brought into focus behind the retina
22
Q

Short-sighted people

A
  • Unable to focus on distant objects
  • The cornea or lens bends the light too much or the eyeball is too long
  • The images of distant objects are brought into focus in front of the retina
23
Q

Short-sighted people

A
  • Unable to focus on distant objects
  • The cornea or lens bends the light too much or the eyeball is too long
  • The images of distant objects are brought into focus in front of the retina
24
Q

What are hormones?

A

Chemicals released directly into the blood

  • Carried in the blood plasma to other parts of the body but only affect particular cells (called target cells) in particular places
  • Control things in organs and cells that need constant adjustment
  • Produced in various glands
  • Travel slowly and last for a long time
25
Q

ADH

A

Source - Pituitary gland (brain)
Role - Controls water content
Effect - Increases water permeability of the kidney tubules to water

26
Q

Adrenaline

A

Source - Adrenal glands (on top of kidney)
Role - Readies the body for a ‘fight or flight’ response
Effect - Increases heart rate, blood flow to muscles and blood sugar levels

27
Q

Insulin

A

Source - Pancreas
Role - Helps control blood sugar lever
Effect - Stimulates the liver to turn glucose into glycogen for storage

28
Q

Testosterone

A

Source - Testes
Role - Male sex hormone
Effect - promotes male secondary characteristics (e.g. facial hair)

29
Q

Progesterone

A

Source - Ovary
Role - Supports pregnancy
Effect - Maintains the lining of the uterus

30
Q

Oestrogen

A

Source - Ovaries
Role - Female sex hormone
Effect - Controls the menstrual cycle and promotes female secondary characteristics (e.g. widening of hips)

31
Q

Nerve characteristics

A
  • Fast message
  • Acts for a short time
  • Acts on a precise area
32
Q

Hormone characteristics

A
  • Slow message
  • Acts for a long time
  • Acts in a more general way
33
Q

What is homeostasis?

A

The maintenance of a constant internal environment
Water - A balance between water gain and water lost
Temperature - Lose heat when you’re hot, gain it when you’re cold

34
Q

Describe the water lost on a hot day

A
  • Sweat a lot
  • Produce less urine but more concentrated
  • Lose more water through breath by breathing faster
35
Q

Describe the water lost on a cold day

A
  • Little sweat

- Produce more urine which is pale and more diluted

36
Q

How is a body temperature maintained?

A
  • Optimum temperature is 37*C

- The brain detects the temperature

37
Q

How is a body temperature maintained?

A
  • Optimum temperature is 37*C

- The brain detects the temperature

38
Q

What happens to the skin when you’re hot?

A
  • Lots of sweat (when it evaporates it transfers heat from you to the environment cooling you down)
  • Blood vessels close to the surface of the skin widen (vasodilation) which allows more blood to flow near the surface so it can radiate more heat to the surroundings)
  • Hairs lie flat
39
Q

What happens to the skin when you’re cold?

A
  • Very little sweat produced
  • Blood vessels near the surface constrict (vasoconstriction) so less heat can be transferred form the blood to the surroundings
  • Shivering which generates more heat in the muscles
  • Hairs stand on end to trap an insulating layer of air which helps keep you warm
40
Q

Why do smaller organisms cool down quicker?

A
  • Bigger surface area to volume ration meaning there is more area for the heat to transfer across
  • Animals in cold climates are often round to keep their surface area to a minimum, reducing heat loss
41
Q

Why do smaller organisms cool down quicker?

A
  • Bigger surface area to volume ration meaning there is more area for the heat to transfer across
  • Animals in cold climates are often round to keep their surface area to a minimum, reducing heat loss
42
Q

How do plants respond to stimuli in their environment?

A
  • Sense light and grow towards it to maximise photosynthesis
  • Sense gravity so roots and shoots grow in the right direction
  • Climbing plants have a sense of touch so they can find things to climb and reach the sunlight
43
Q

How do plants respond to stimuli in the presence of predators?

A
  • White clover plant produces substances that are toxic to cattle to avoid being eaten
44
Q

How do plants respond to stimuli in abiotic stress?

A

Abiotic stress = anything that is harmful but non-living e.g. a drought
- Carrots produce antifreeze proteins at low temperatures to bind ice crystals and lower the temperature that water freezes at to stop ice crystals from growing

45
Q

What are auxins?

A

Plant hormones that control growth at the tips and shoots

  • Produced in the tips and diffuses back to stimulate the cell elongation process which occurs in cells just behind the tips
  • Promotes growth in the shoot but inhibits the growth in the root
46
Q

What is gravitropism/geotropism?

A

When the stimulus for plant growth is gravity

  • Shoots are negatively geotropic/gravitropic (grow away from gravity)
  • Roots are positively geotropic/gravitropic (grow towards gravity
47
Q

What is phototropism?

A

When the stimulus for plant growth is light

  • Shoots are positively phototrophic (grow towards light)
  • The cell grows faster on the shaded side so the shoot bends towards the light

Biology (9 decks)

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