GCSE Nervous System Flashcards
Define homeostasis
The maintenance of a constant internal environment
Define negative feedback
When a change from normal conditions is detected and prompts a response to return to normal
Give three procedures that homeostasis maintains
Temperature, blood glucose levels, water balance
What are the two communication systems in the body?
Hormonal and nervous systems
How does the nervous system send signals?
Via electrical impulses in neurones
Define stimulus
A signal to which an organism responds
Give the stimulus for smells
Chemicals
Describe the coordination pathway
Stimulus —> receptor (PNS) —> coordinator (CNS) —> effector
Give examples of stimuli
Pressure, temperature, sounds light, chemicals
Give examples of receptors
Skin, eyes, ears, nose, tongue
Give examples of coordinators
Brain, spinal cord
Give examples of effectors
Muscles and glands
What are nerves?
Bundles of neurones in the PNS
Where are electrical impulses generated?
Receptors
What are the three types of neurones?
Sensory, relay and motor
Where are the sensory neurones found?
From receptors to CNS
Where are relay neurones found?
CNS
Where are motor neurones found?
CNS to effectors
What does the reflex arc do?
Rapid, automatic responses to stimuli to protect the body
What part of the CNS do reflexes go through
Spinal cord (usually closer than brain)
What is a synapse?
The gap between neurones
How do synapses work?
The nerve signal is transferred by neurotransmitters which diffuse across the gap and set off a new electrical impulse in the next neurone
Describe how electrical impulses are transmitted across synapses
When the electrical impulses reaches the end of a neurone, vesicles move to join the cell membrane to release neurotransmitters into the synapse, which diffuse across the synapse and bind to receptors on the next neurone to begin a new impulse
Give an identifying feature of a sensory neurone
Cell body sticking out of axon
Give an identifying feature of a relay neurone
Short
Give an identifying feature of a motor neurone
Cell body attached to dendrites + effector on one end
What is the eye?
A sensory organ that detects light and converts light energy into electrical impulses
What are the rods responsible for?
Black and white vision in low light
What are the cones responsible for?
Coloured vision in high light
What do radial and circular muscles do?
radial muscles contract, circular muscles relax
What is accommodation?
The process by which the eye’s lens changes shape to focus near or far objects on the retina
How does accommodation work for distant images?
Ciliary muscles relax, suspensory ligaments contract, lens is long and thin (less refraction needed)
How does accommodation work for close images?
Ciliary muscles contract (bulge), suspensory ligaments relax, lens is short and fat (more refraction needed)
Why does the lens become fatter to see close objects?
The divergent rays are shining on the ends of the lens, so it makes it bulgy to focus the rays into the retina
What is myopia?
Short sightedness - unable to see distant objects - eye is too long / lens is too convex - image forms in front of retina
What is hyperopia?
Long sightedness - unable
What are the treatments for myopia and hyperopia?
Concave lens for myopia, convex lens for hyperopia
What part of the brain controls homeostasis?
The hypothalamus
What is the thermoregulatory system made up of?
Receptors that monitor blood temperature
What is negative feedback?
A response to a change in the body that reverses the change
What effectors does the thermoregulatory system use?
Sweat glands. blood vessels in skin and skeletal muscles
What is the body’s negative feedback loop to being too cold?
stimulus: too cold / receptor: thermoreceptors in the skin / coordinator: hypothalamus / effector + response: vasoconstriction, shivering, sweat production stops, piloerection / core body temperature rises.
Why does the body use vasoconstriction/dialation?
Vasodialation allows heat to be lost by radiation. Vasoconstriction stops heat from being radiated
Why does the body shiver?
Rapid skeletal muscle contraction causes high rates of respiration, which is an exothermic reaction
Why does the body use piloerection when cold?
To trap warm air between hairs
