Reflex arcs Flashcards
What is a stimulus?
A detectable change in the internal of external environment of an organism
Stimuli are detected by …
Receptors
Name the structure labelled B on the diagram
Spinal cord
A response is produced by an ….
Effector
Give two examples of an effector
Gland or muscle
Name the type of neurone ahown on the diagram
Motor neurone
Name the strucutre labelled D on the diagram
Effector (in this case a muscle)
Give the sequence of events that lead from a stimulus to a response
Stimulus –> Receptor –> Coordinator–> Effector –> Response
The simplest type of nervous response is called a …
Reflex
The central nervous system consists of …
Brain and spinal cord
What is the function of a sensory neurone?
Carry electrical impulses from receptors to central nervous system
Name the neurone labelled C on the diagram
Motor neurone
What is the function of a motor neurone?
Carry electrical impulses from central nervous system to effectors.
Why are reflexes important?
Protect from danger
Maintain posture
Give two features of a reflex arc
Immediate - only 3 neurones involved. Minimum number of synapses
Specific - one stimulus leads to one response
Involuntary - happens without conscious though
Innate - present from birth
Name three receptors
Pacinian corpuscel
Rod cell
Cone cell
Thermoreceptor
Osmosreceptor
Chemoreceptor
Name the neurone labelled A on the diagram
Sensory neurone
When does the heart rate need to increase?
Exercise/increased muscle contraction
Fight or flight response
Name the receptors that detect and increase in carbon dioxide in the blood,.
Chemoreceptors
Where in the body are the chemoreceptors that detect an increase in carbon dioxide in the blood
Carotid arteries
Aortic arch
What effect does the sympathetic nervous system have on the rate rate?
Increases heart rate and stroke volume
What effect does noradrenaline have on the heart rate?
Increases heart rate
What effect does the parasympathetic system have on the heart rate?
Decreases heart rate
Name the neurotransmitters released by the sympathetic and parasympathetic system on the SAN
Sympathetic - noradrenaline
Parasympathetic - acetylcholine
What effect does the parasympathetic nervous system have on the heart rate?
Decreases heart rate and stroke volume
Name the three neurones found in a reflex arc
Sensory neurone
Relay neurone
Motor neurone
Where is the coordinator for the heart rate reflex?
Medulla or hypothalamus (in the brain)
For what is SAN an abbreviation for?
Sinoatrial node
For what is AVN and abbreviation for?
Atrioventricular node
Describe the role of the SAN and AVN in controlling the contraction of the heart
SAN generates a wave of excitation over the atria
Atria contract
Blood is forced into the ventricles
AVN sends electrical impulse down the bundle of His to heart apex
Impulse passes to Pukinje fibres which cause the ventricles to contract
Where is the SAN located?
Wall of the right atrium
When a wave of electrical activity reaches the AVN, there is a short delay before the impulse is generated in the Bundle of His. Explain why this is important.
Allow atria to empty/contract
Blood enters the ventricles
What is the function of the dendrites?
Pass elecrical impulses from the relay neurone to the cell body of the motor neurone
What is the function of the myelin sheath?
Elelctrical insulator
Allows impulses to jump between Nodes of Ranvier
Where in the body are the motor neurone cell body and dentrites found?
Spinal cord
What is the function of the axon?
Pass electrical impulses from the cell body to the axon terminals (muscle)
