b10 Flashcards
what is homeostasis?
the regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
what are receptors?
cells which detect stimuli - a change in the environment
what is the coordination center?
brain/spinal chord/ pancreas. they recieve and process information from receptors
what are effectors?
muscles or glands which bring about responses which restore optimum levels.
how is the nervous system adapted to it’s function?
they contain neurones with axons that can be over a meter in length which is more efficient than having many neurons as less time is wasted transferring electrical impulses from one cell to another.
describe what happens when there is a stimulus
the info from the receptors passes along cells (neurons) as electrical impulses to the CNS - brain or spinal chord. the CNS coordinates the response of the effectors which might be muscles contracting or glands secreting hormones
what is a reflex action?
an automatic and rapid action that does not involve the conscious part of the brain.
what is the sensory neuron?
carries impulses from sense organs to CNS
what is the relay neuron
found inside CNS and connect sensory and motor neurons
what is motor neuron?
carries impulses from CNS to effectors - muscles or glands
what is a synapse?
the gaps between neurones through which electrical impulses pass through in the form of a neurotransmitter
what is the brain
made up of billions of interconnected neurones and has different regions that carry out different functions
what does the cerebral cortex do?
outer layer of brain. responsible for intelligence, memory, consciousness and personality
what does the cerebellum do?
under cerebral cortex and manages balance, muscle coordination and movement
what does the medulla do?
controls unconscious activities such as heart rate and breathing
why is investigating and treating the brain hard?
it is very complex and delicate and because different regions cannot be studied in isolation
how can neuroscientists study the brain?
they can study patients with brain damage, they can electrically stimulate different parts of the brain and use MRI scanning technigues
function of cornea
transparent lens that refracts light as it enters the eye
function of iris
controls how much light enters the pupil
function of the lens
transparent disc that can change shape to focus light onto the retina
function of optic nerve
sensory neuron that carries impulses between the eye and the brain
function of pupil
hole that allows light to enter the eye
pupil reflex in dark light
receptors detect change in environment.
impulse passes along (sensory) neurone - the optic nerve - to the relay neuron in the coordinator which passes to the motor neurons which are the muscles in the eyes:
radial muscles contract and circular muscles relax
the pupil dilates (widens)
so more light enters the eye
pupil reflex in bright light
receptors detect change in environment.
impulse passes along (sensory) neurone - the optic nerve - to the relay neuron in the coordinator which passes to the motor neurons which are the muscles in the eyes:
radial muscles relax and circular muscles contract
the pupil constricts
less light enters the eyes
what is accomodation?
the process of changing the shape of the lens to focus on near or distant objects
what happens when you focus on a near object?
the ciliary muscles contract, so ciliary muscles have a smaller diameter so suspensory ligaments loosen / slacken, so lens thickens or lens becomes more curved / rounded. light is refracted more - bends more, so light rays / image focused on retina.
what happens when you focus on a distant object?
the ciliary muscles slacken so they have a larger diameter, the suspensory ligaments tighten so lens becomes thinner. light is refracted less so then the light rays focus on the retina.
what is myopia and what happens?
short sightedness - the eye is too elongated or the lens is too thick so the image is focused infront of the retina
function of retina
contains light receptor cells - rods and cones.
what is hyperopia and what happens?
the eyeball is too short so the image is brought to focus behind the retina.
how do spectacle lenses help correct eye problems?
concave - corrects the rays so they focus on retina (myopia)
convex - refracts light rays so that they focus on the retina (hyperopia)
what are some other technologies that help correct vision?
hard and soft contact lenses, laser surgery to change the shape of cornea, and a replacement lens in the eye
