3.4.1 Control Systems Involve Stimulus and Response Flashcards Preview

A-level Biology Oxford AQA > 3.4.1 Control Systems Involve Stimulus and Response > Flashcards

Flashcards in 3.4.1 Control Systems Involve Stimulus and Response Deck (28)
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What do receptors do?

Detect stimuli


What can receptors be?

Cells or proteins on cell surface membranes


What are effectors?

Cells that bring about a response to stimulus to produce an effect


Give examples of types of effectors cells

Muscle cells and cells found in glands e.g. pancreas


How do receptors communicate with effectors?

Via nervous system and/or hormonal system


Name 3 types of neurones 

  1. Sensory neurones 
  2. Motor neurones 
  3. Intermediate/relay neurones 


What do sensory neurones do?

Transmit electrical impulses from receptors to the CNS - the brain and spinal cord


What do motor neurones do?

Transmit electrical impulses from CNS to effectors


What do relay neurones do?

Transmit electrical impulses between sensory neurones and motor neurones


State the 5 stages of a response to a stimulus


What the central nervous system (CNS) made up of?

Brain and spinal cord


What is the peripheral nervous system (PNS) made up of?

Neurones that connect the CNS to the rest of the body


What does the somatic nervous system control?

Conscious activities e.g running and playing video games


What does the autonomic nervous system control?

Controls unconscious activities e.g. digestion


What does the sympathetic nervous system do?

Gets the body ready for action - 'flight or fight' system


What does the parasympathetic nervous system do?

Calms the body down - 'rest and digest' system


What is a reflex?

When body responds to stimulus without making a conscious decision to respond


What is a reflex arc?

Pathway of neurones linking receptors to effectors in a reflex


Describe the simple reflex arc for a hand-withdrawal response to heat

  1. Thermoreceptors in skin detect heat stimulus
  2. Sensory neurone carries impulses to relay neurone
  3. Relay neurone connects to motor neurone
  4. Motor neurone sends impulses to effector
  5. Muscle contracts to withdraw your hand and stop it being damaged


What does it mean if there's a relay neurone involved in a simple reflex arc?

It's possible to override the reflex

e.g. your brain could tell your hand to withstand the heat


Explain how nervous communication is localised 

When electrical impulse reaches end of neurone = neurotransmitters are secreted directly onto target cells


Explain how nervous communication is short-lived 

Neurotransmitters are quickly removed once they've done their job


State the 2 types of responses that simple mobile organisms have to keep them in a favourable environment

  • Tactic (taxes)
  • Kinetic (kineses)


Define taxes

Organisms move towards or away from a directional stimulus e.g. light 


Define kineses

Organisms' movement is affected by non-directional stimulus e.g. humidity


Give an example of taxes

  • e.g. woodlice show tactic response to light (phototaxis)
  • Move away from light source
  • Helps them to survive ∵ it keeps them concealed under stones during the day (where they're safe from predators) & keeps them in damp conditions (reduces water loss)


Give an example of kineses

  • e.g. woodlice show kinetic response to humidity
  • High humidity = move slowly and turn less often = so they stay where they are
  • Air gets drier = move faster and turn more often = move into new area
  • Response increases chance woodlouse will move to area with higher humidity
  • Improves survival chances of organisms = reduces their water loss & keeps them concealed 


Explain the importance of relfex actions (3)

  • Automatic / involuntary
  • Prevents injury 
  • Role in homeostasis 

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