A reflex arc Flashcards
What is the simplest type of nervous resonse to a stimulus?
A reflex arc
What are the two divisions of the nervous system?
- CNS
- PNS
What is CNS stand for?
Central Nervous System
What is CNS made up of?
The brain and the spinal cord
What does PNS stand for?
Peripheral nervous system
What is the PNS made up of?
Pairs of nerves that originate from either the brain or the spinal cord
What is the PNS divided into?
Sensory and motor nerounes
What is the sensory neruone carry?
Nerve impulses (electrical signals) from receptors towards the CNS
What do the motor neruone carry?
Carry nerve impulses away from the CNS to the effectors
What is the motor neurone further divided into?
Voluntary nervous system
and
automatic nervous system
What is the voluntary nervous system?
Carries nerve impulses to the body muscles and under voluntary (conscious) control
What is the autonomic nervous sytem?
Carries nerve impulses to glands, smooth muscle and cardiac muscle and is not unver voluntary control , it is involuntary (subconscious)
What is a spinal cord?
A column of nervous tissue that runs along the back and lies inside the vertebral column for protection
Diagram of reflex arc
What is a reflex?
It is a rapid response to a stimulus without conscious control
What is a reflex arc?
A pathway of neurones involved in a reflex
What is spinal reflex?
One of the neurones in the spinal cord
Sequence of reflex arc
- stimulus
- receptor
- Sensory neurone
- Coordinate/intermediate neurone
- Motor neurone
- Effector
- Response
Example of withdrawing hand from hot object
- Stimulus - heat from hot object
- Receptor - Temperature receptor in the skin on the back of hand, generates nerve impulses in the sensory neurone
- Sensory neurone - Passes nerve impulses to spinal cord
- Coordinate(intermediate neurone) - links to the sensory neruone to the motor neurone in the spinal cord
- Motor neurone- carries nerve impulses from the spinal cord to the muscle in upper arm
- Effector - muscle in upper arm which is stimulated to contract
- Response - pulling the hand away from hot object
Why is it important that reflexes are involuntary
- They do not require the decision of making powers of the brain
- Free to carry out more complex responses
- Brain is not overloaded with situations in which the response is same
- (if some impulses sent to brain and informed what is happening , override reflex)
Why is reflexes important for our body?
They protect the body from harm
Effective from bith and not have to learn
e.g infants
Why is it important that reflexes are fast?
- Fast - neurone pathway is short and very few synpases where neurones communicate with each other (synpases are slowest link in a neurone pathway)
- Important in withdrawl reflexes
- Absence of decision making process means action is rapid
