14.3- A REFLEX ARC Flashcards
What is the simplest type of nervous response to a stimulus?
reflex arc
What are the two major divisions of the nervous system?
central nervous system (CNS)
peripheral nervous system (PNS)
What is the central nervous system made up of?
brain + spinal cord
What is the peripheral nervous system made up of?
pairs if nerves that originate from either brain or spinal cord
What is the peripheral nervous system divided into? (2)
sensory neurones
motor neurones
What do sensory neurones do?
carry nerve impulses (electrical signals) from receptors towards CNS
What do motor neurones do?
carry nerve impulses away from CNS to effectors
How can the motor nervous system be further subdivided? (2)
voluntary nervous system
autonomic nervous system
What does the voluntary nervous system do?
carries nerve impulses to body muscles + under voluntary (conscious) control
What does the autonomic nervous system do?
carries nerve impulses to glands, smooth muscle + cardiac muscle + not under voluntary control, it’s involuntary (subconscious)
What is the spinal cord?
column of nervous tissue that runs along back + lies inside vertebral column for protection
How are reflex actions described to be?
rapid, short-lived, localised + totally involuntary
What is the pathway of neurones involved in a reflex known as?
reflex arc
How many neurones do reflex arcs involve?
3 neurones
Where is one of the neurones from the reflex arc and so what is this type of reflex called?
in spinal cord + so this type of reflex also called spinal reflex
Main stages of spinal reflex arc:
stimulus -> receptor -> sensory neurone -> coordinator -> motor neurone -> effector -> response
Why reflex actions important- involuntary
involuntary + so don’t require decision-making power of brain, so leaving it free to carry out more complex responses
some impulses nevertheless sent to brain, so it’s informed of what’s happening + can sometimes override reflex if necessary
Why reflex actions important- protection
protect body from harm + don’t have to be learnt
Why reflex actions important- they’re fast
fast as neurone pathway short with very few, typically one or two, synapses where neurones communicate with each other
important in withdrawal reflexes
Why reflex actions important- absence of decision-making process
action rapid
