Reflex arc Flashcards
Define reflex
rapid, involuntary response to stimulus
describe structures involved in a simple reflex arc
from receptor > sensory neurone> intermediate neurone > motor neurone > to effector
Explain how a simple reflex arc works
-stimulus detected by receptor which generates impulse in sensory neurone
-sensory neurone passes impulse to intermediate neurone in spinal ord
-impulse then passed to motor neurone which stimulate effector to carry out response
outline importance of reflex arcs
-protects body from harm and dont have to be learnt
-involuntary so leave brain free to carry out more complex responses
-fast to allow rapid removal from danger
CNS
made up of the brain and spinal cord
PNS
made up of nerves that originate from either brain or spinal cord
sensory neurone
carry nerve impulses from receptors towards CNS
motor neurone
carry nerve impulses away from the CNS to effectors
voluntary nervous system
carries nerve impulses to body muscles and is under conscious control
autonomic nervous system
carries nerve impulses to glands, smooth muscle and cardiac muscle and is not under voluntary control
spinal cord
column of nervous tissue that runs along the back lies inside vertebral column for protection
reflex arc example with candle
- stimulus heat from candle flame
-receptor from nerve ending in skin sensitive to heat
-sensory neurone passes nerve impulses to spinal cord
-intermediate neurone passes impulses across spinal cord
-motor neurone passes impulses to muscle
-effector contracts
-response is hand moved quickly away from flame
Response of reflex arc
- rapid
- short -lived
- localised
- involuntary
How many neuroses does reflex arc involve
3
Why is it good for reflexes to be involuntary
- don’t require decision making
- leaving the brain free to carry out more complex responses
- so brain is not overloaded with situations where response is all same
- brain is informed so what’s happening can sometimes override the reflex if necessary
