B10 Flashcards
Receptors
Cells that detect changes/stimuli in internal or external environment
Coordination centre
Areas that receive and process information from receptors. Send out signals to start response
Brain coordinates nervous system
Effectors
Muscles or glands that respond once stimuli received, restoring conditions to optimum levels
Central Nervous System (CNS)
In vertebrates consists of brain and spinal cord. In mammals connected to body by neurones
Sensory Neurones
Neurones that carry information as electrical impulses from receptors to CNS
Motor neurones
Carry electrical impulses from CNS to effectors
Synapses
The connection between two neurones
Nerve signal is transferred by chemicals that diffuse called neurotransmitters
Reflex arc
Neurones go through the spinal cord or through unconscious part of brain
Impulses sent along sensory neurone to relay neurone in CNS
Impulses passed along synapse between neurones
Impulse then travels along motor neurone to effector
Why are reflexes faster that normal reactions
Don’t involve conscious part of brain so no thought
Eg: pupils dilate in bright light
Reaction time
Time taken to respond to a stimulus
Affected by age, gender or drugs
Cerebral cortex
Outer wrinkly area
Responsable for consciousness, intelligence, memory and language
Medulla
Brain stem attached to spinal cord
Controls unconscious activity - breathing, heartbeat
Cerebellum
Lower rear section
Responsible for muscle coordination
Hypothalamus
Small region in centre of brain
Regulation centre - temperature
Meninges
Membranes underneath skull
Methods to study brain
Patients with brain damage - small part of brain damaged, effect on patient can tell what that part of brain does
Electrically stimulating - stimulating brain by pushing tiny electrode into tissue and giving small bit of electricity, then see what happens
MRI scans - Can see what parts of brain active when listening to music or recalling a memory
Sclera
Tough, supporting wall of eye
Cornea
Transparent outer layer at front of eye
Refracts light into eye
Iris
Contains muscles that control diameter of pupil exposed, so how much light enters eye
Lens
Focuses light onto retina
Retina
At back of eye
Contains receptor cells sensitive to light intensity and colour
Ciliary muscles and Suspensory ligaments
Control shape of lens
Optic nerve
Carries impulses from receptors on retina to brain
The Iris reflex - adjusting for bright light
Bright light can damage retina
Light receptors detect very bright light
Reflex is triggered that makes circular muscles in iris contract and radial muscles relax. This makes iris bigger, reducing size of pupil
In dim light
Circular muscles relax
Radial muscles contract
Makes pupil wider
Accommodation
Eye changes shape of lens to focus on retina
Near object
Ciliary muscles contract
Slackens suspensory ligaments
Lens becomes thicker
Increases amount of refraction
Distant objects
Ciliary muscles relax
Suspensory ligaments pull tight
Lens becomes thinner
Less refraction
Long sightedness (hyperopia)
Cannot see near objects
Occurs when lens is wrong shape (too thin) so doesn’t refract enough
So the refracted light focuses behind retina
Use convex lens (curves outwards)
Short sighted (myopia)
Cannot see distant object as refracts light too much and focuses before retina
Lens may be too thick
Concave lens (curves inwards)
Contact lenses
Thin lenses on surface of eye, almost invisible
Hard contact lenses last a long time and have to be taken out and sterilised overnight
Soft contact lenses are more comfortable, some can be worn more than once if sterilised overnight, others are one use and then disposed
Laser eye surgery
Laser used to vaporise tissue to change shape of cornea In laser eye surgery for myopia (short sightedness) they use lasers to reduce the thickness of the cornea so it refracts light less strongly. For hyperopia (long sightedness) they use lasers to change the curve of the lenses to refract light better
Replacement lens surgery
Natural lens removed and replaced with artificial one
