Stimuli and Responses Flashcards
(92 cards)
How do animals increase their chances of survival?
by responding to changes in their external environment, e.g. avoiding harmful environments that are too hot or too cold, and changes in their internal environment to ensure conditions are always optimal for their metabolism
How do plants increase their chances of survival?
by responding to changes in their environment
What is a stimulus?
any change in the internal or external environment
What are receptors?
cells or proteins on cell surface membranes that detect stimuli (loads of different types of receptors that detect different stimuli - are specific)
What are effectors?
cells that bring about a response to a stimulus, to produce an effect. (muscle cells and cells found in glands)
How do receptors communicate with effectors?
via the nervous system or hormonal system, or both
How does the nervous system send info?
as electrical impulses
What is the NS made up of?
a complex network of cells called neurones
What are the 3 main types of neurone?
sensory, motor, relay
What is the role of sensory neurones?
transmit electrical impulses from receptors to CNS - brain and spinal cord
What is the role of motor neurones?
transmit electrical impulses from CNS to effectors
What is the role of relay neurones?
transmit electrical impulses between sensory neurones and motor neurones
What are electrical impulses also called?
nerve impulses or action potentials
Describe process of a stimulus to response.
- stimulus is detected by receptor cells and electrical impulse is sent along sensory neurone
- when electrical impulse reaches end of neurone, neurotransmitters take info across to next neurone, which then send an electrical impulse
- CNS (coordinator) processes info and sends impulses along motor neurones to an effector
What is the CNS?
brains and spinal cord
What is the peripheral nervous system?
made up of neurones that connect CNS to rest of the body
2 systems of peripheral NS?
- somatic NS controls conscious activities
- autonomic NS controls unconscious activities e.g. digestion
2 divisions of autonomic NS?
- sympathetic NS gets body ready for action (‘fight or flight’ system)
- parasympathetic NS calms body down (‘rest and digest’ system)
What is a reflex?
body responds to stimulus without making a conscious decision to respond
How do reflexes help organisms protect the body?
they’re rapid (don’t spend time deciding how to respond so info travels really fast from receptors to effectors)
What is a reflex arc?
pathway of neurones linking receptors to effectors in a reflex
Describe the hand-withdrawal response to heat.
- thermoreceptors in skin detect heat stimulus
- sensory neurone carries impulse to relay neurone
- relay neurone connects to motor neurone
- motor neurone send impulse to effector (biceps muscle)
- muscle contracts to withdraw hand and stop it being damaged
How is it possible to override the reflex?
if there’s a relay neurone involved in the simple reflex arc, then its possible to override reflex, e.g. brain could tell hand to withstand heat
Why is NS communication described as localised?
when electrical impulse reaches end of neurone, neurotransmitters are secreted directly onto target cells (e.g. muscle cells) - so nervous response is localised