Reflex Arc Flashcards
What is the central nervou system
Consist of he brain and the spinal cord
What is the peripheral nervous system
Pairs of the nerves that originate from either the brain or the spinal cord
What is PNS subdivided into
Sensory, motor neurones
What are motor neurons
Carry nerve impulses away from CNS to towards effectors
Sensory neurons
Carry nerve impulses from receptors towards CNS
What are motor neurones sub divided into
Voluntary and autonomic nervous system
What is the voluntary nervous system
Carry nerve impulses to body’s muscles under voluntary conscious control
What is the autonomic NS
- not consciously controlled
- control involuntary systems - glands, muscles
What are the 2 major divisions autonomic nervous systems
Sympathetic and parasympathetic
Differences between sympathies and parasympathetic NS
Parasympathetic
- inhibit effectors, slows down activity
- controls activity under resting conditions
- conserving energy and helps replenish body’s reserves
Sympathetic
- stimulates effector, speeds up activity
- controls effectors when exercise strenuously or experience extreme emotions
- helps cope with stressful situations
Describe nerve cell structure
- cell body: part that contains nucleus
- dendrites: carries a nerve impulses towards the cell body
- axons/nerve fibres: carries nerve impulses away from the cell body
- nerve: a uncle of axons outside the CNS
- myelin sheath
Name 3 types of neurones
Sensory, motor, intermediate/relay
What is sensory neurons
- carry impulses from receptors to CNS
What is intermediate/ relay neurones
- large number of connections with other nerve cells
Describe motor neurons
- axons extend out to effectors
- extremely long
Stage 1 of the reflex action
Stimulus eg heat
Stage 2 of the reflex arc
Receptor - generates nerve impulses eg temperature receptors in skin
Stage 3 of a reflex arc
Sensory neurone - passes impulse to spinal cord
Stage 4 of the reflex arc
Coordinator - intermediate neurone links sensory neurone to motor neurone in the spinal cord
Stage 5 of the reflex arc
Motor neurone - Carries nerve impulses from spinal cord to effector
Stage 6 of the reflex arc
Effector - eg muscle/glands
Stage 7 of the reflex arc
Response- muscles contract and moves body way from stimulus eg heat
State reasons for why are reflex arcs good
- Involuntary
- protect boy from harm
- fast
- absence of decision making
Why are reflex arcs involuntary
- decision making in the brain is not needed
- ## brain is not overloaded
Protect from harm
It’s not leant we have it since birth
Fast
Short pathways with few synapses
Absence from decision making
Fast response
What is a synapse
Junction between neurones or neurone and a effector
What do synapses do to the transmission speed of nerve impulses
Slows them down
Why do we have synapses
- allows greater control
- multiple responses to one stimulus
- allows for the possibility of summation
