B10 Human nervous system Flashcards
what is homeostasis
regulation of internal conditions to maintain optimum cell function in response to internal and external changes
what are 3 internal conditions that need to be kept balanced
body temperature
body water content
blood glucose concentration
what is an automatic control system
the system that detects changes and responds to them for example nervous responses in nervous system and chemical responses in hormone system
what are receptors
cells that detect changes (stimuli) in the internal or external environment
what is a coordination centre
areas that receive and process information from receptors. They send out signals and coordinate the response of the body eg brain, spinal cord and pancreas
what are effectors
muscles or glands that bring about responses to the stimulus that has been received
what happens when a sensory receptor detects a stimulus
the information is sent as an electrical impulse that passes along special cells called neurones (found in bundles known as nerves)
The impulse travels along the sensory neurone until it reaches the CNS (brain)
The brain sends impulses out along motor neurones which carry the information to the effectors which respond
what are reflexes
responses that are so fast that they happen subconsciously eg blinking
what are relay neurones
found in the CNS and they connect a sensory neurone and a motor neurone
what is the reflex arc pathway
receptor - sensory neurone- CNS - relay neurone- motor neurone- effector organ
what are synapses and how do they work
gaps between neurones. The electrical impulses have to travel across the synapses by chemical diffusion which is slower than the speed they travel in the neurone but is the only way
how is the reflex pathway different from a normal conscious action
in a reflex action the coordinator is a relay neurone either in the spinal cord or the unconscious area of the brain
what is the function of the cerebral cortex
consciousness, intelligence, memory and language
what is the function of the cerebellum
coordinating muscular activity and balance
what is the function of the medulla
unconscious activities eg controlling heartbeat, breathing and movement of the gut
what is the function of the hypothalamus
controlling body temperature
what is the sclera
white outer layer of the eye. tough and strong making the eyeball not easy to damage
what is the cornea
the transparent area at the front of the sclera. lets light into the eye and the curved surface is important for changing the direction of light as it enters the eye so that when they enter they are focused on the retina
what is the role of the muscular iris
controls the size of the pupil by contracting or relaxing to control the amount of light that enters the eye
what holds the lens in place in the eye
suspensory ligaments and ciliary muscles
what does the optic nerve do
carries impulses form the retina to the brain
how does the eye focus on a distant object
ciliary muscles relax so that the suspensory ligaments are pulled tight and the lens is pulled flat and thin. Only refracts light rays slightly so they are focused on the retina
how does the eye focus on a near object
ciliary muscles contract so the suspensory ligaments loosen. The lens is then thicker and more curved and refracts light rays strongly so they are focused on the retina
what causes you to see blurred images
when the light rays aren’t focused on the retina
why do many old people need reading glasses
as you age, the lens hardens, accomodation gets more difficult making it harder to focus on close objects
what is myopia
when you can’t see things far away because the light is focused in front of the retina maybe as a result of a lens that is too curved or a long eyeball
treated by wearing glasses with a concave lens
what is hyperopia
when close objects are blurred maybe as a result of a lens that is too flat and thin or a short eyeball. The light is focused behind the retina. Treated by wearing glasses with a convex lens
why is it difficult to study the brain
encased in the skull
delicate, easy to damage
why is it difficult to treat brain disorders
easy to cause damage during surgery
many drugs can’t pass through the surrounding membranes
how does light from an object form an image on the retina
light rays enter the eye through the cornea where they are refracted a little. they then travel through the pupil and lens. they are then refracted further to meet the retina and form an image upside down
