What do receptors do?
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
- Sensory neurones
- Motor neurones
- 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
- Thermoreceptors in skin detect heat stimulus
- Sensory neurone carries impulses to relay neurone
- Relay neurone connects to motor neurone
- Motor neurone sends impulses to effector
- 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)
Organisms move towards or away from a directional stimulus e.g. light
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)