[14.3] a reflex arc Flashcards
what are the 2 manjor divisions of the nervous system?
- central nervous system (CNS)
- peripheral nervous system (PNS)
what is the CNS made up of?
brain and spinal cord
what is the PNS made up of?
nerves that originate from either the brain or the spinal cord
what is the PNS divided into?
sensory neurones and motor neurones
what do sensory neurones do?
carry nerve impusles from receptors towards the CNS
what do motor neurones do?
carry nerve impulses away from the CNS to effectors
what is the motor nervous system subdivided into?
- voluntary nervous system
- autonomic nervous system
what does the voluntary nervous system do?
- carries nerve impluses to body muscles
- is under voluntary control
what does the autonomic nervous system do?
- carries nerve impulses to glands, smooth muscle and cardiac muscle
- involuntary
describe the spinal cord
- column of nervous tissue that runs along the back
- lies in vertebral column for protection
- at intervals, there are pairs of nerves (sensory and motor)
what is a reflex?
an involuntary response to a sensory stimulus
what is a reflex arc?
the pathway of neurones involved in a reflex
describe the reflex arc for touching a hot object
- stimulus - heat from hot object
- receptor - thermoreceptors in skin generates nerve impulses in sensory neurone
- sensory neurone - passes nerve impulses to spinal cord
- coordinator (relay neurone) - links sensory neurone to motor neurone in spinal cord
- motor neurone - carries nerve impulses from spinal cord to muscle in upper arm
- effector - muscle in upper arm, which is stimulated to contract
- response - pulling hand away from hot object
why are reflex arcs important?
- involuntary so doesn’t require decision making from brain, so it is not overloaded
- protect the body from harm
- effective from birth and do not have to be learnt
- fast
how are reflex arcs fast?
neurone pathway is short with 1 or 2 synapes where neurones communicate with each other
