T5 human nervous system Flashcards
function of the nervous system
allows the body to react to its surroundings and coordinate an appropriate response
how does a stimulus lead to a response being carried out by the body
stimulus is converted into an electrical impulse by the receptors
electrical impulse passes along sensory neurons to the CNS
CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector which carries out the response
what sequence of events describes how the nervous system work
Stimulus → receptor → coordinator →
effector → response
what is a reflex action
automatic and rapid response which doesn’t involve any conscious input from the brain
why are reflex actions important
aid survival by preventing harm to the body
describe how a reflex action occurs via a reflex arc
stimulus is detected by a receptor
electrical impulses passes along a sensory neurone to the spinal chord
at a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
at the effector, an appropriate response is carried out
what is the difference between a reflex pathway and a conscious pathway
within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain
in a conscious pathway, the coordination centre is in the conscious part of the brain
function of the cerebral cortex
controls consciousness, intelligence, memory and language
function of the cerebellum
controls muscular coordination
function of the medulla
controls unconscious activities
why is the investigation and treatment of the brain difficult
brain is complex and delicate
easily damaged and destroyed
certain membranes prevent drugs from reaching the brain
exact function of each part of the brain is unknown
what methods are used to determine brain function
studying patients with brain damage
electrical stimulation of the brain
MRI scans
what stimuli are the receptors of the eye sensitive to
light intensity and colour
2 main functions of structures found within the eye
focusing on near or distant objections - accommodation
adaptation to dim light
describe the structure and function of the retina
light-sensitive layer found at the back of eye
light stimulates the retinal cells, resulting in impulses being sent to the brain
describe the structure and function of the optic nerve
connects the eye and the brain
carries impulses to the brain so that an image can be visualised
describe the structure and function of the sclera
tough outer layer of the eye which protects its internal structures
describe the structure and function of the cornea
curved transparent layer at the front of the eye
lets light into the eye and allows light to be focused onto the retina
describe the structure and function of the iris
muscle which controls the size of the pupil by contracting or relaxing
allows the eye to adjust to bright or dim lighting
describe the structure and function of the ciliary muscles and suspensory ligaments
hold the lens in place and control its shape
describe how the iris alters the size of the pupil in bright and dim light
B: circular muscles contract and radial muscles relax - makes pupil smaller to avoid retinal damage
D: circular muscles relax and radial muscles contract - makes pupil larger so more light can enter the eye
what is accommodation
alteration of the lens shape in order to focus on near or distant objects
how does the eye focus on a nearby object
ciliary muscles contract
suspensory ligaments loosen
lens becomes thicker and more curved - light rays are refracted strongly
how does the eye focus on a far away object
ciliary muscles relax
suspensory ligaments tighten
lens becomes thinner - light rays are refracted weakly
what is myopia
short-sightedness - usually occurs when the lens of the eye is too curved
light is focused in front of the retina so images appear blurry
how can myopia be treated
glasses with a concave lense which spreads out light rays so they can be focused on the retina
what is hyperopia
long-sightedness - occurs when the lens of the eye is too flat
light is focused behind the retina so images appear out of focus
how can hyperopia be treated
glasses with a convex lense which brings the light rays together so they can be focused on the retina
two types of contact lenses
hard - rigid material, last a long time, must be kept sterile
soft - flexible material, last for a shorter time, more comfortable
what is laser eye surgery
use of lasers to fix visual defects in adults
m - lasers reduce the thickness of the cornea so light is refracted less strongly
h - lasers alter the curvature of the cornea so that light is refracted correctly
how can replacement lenses be used to treat visual defects
can be implanted into the eye (along with natural lens) or it may replace the natural lens altogether
risks of lens replacement
retinal damage, cataracts and infections
where is body temperature controlled in the body
by thermoregulatory centre in the hypothalamus of the brain
how is temperature monitored by the body
thermoregulatory centre has receptors sensitive to blood temperature
skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory centre
what physiological changes occur when the body temperature is too high
vasodilation - blood vessels near the surface of the skin dilate, more heat is radiated away
sweating - evaporation of water takes away heat energy from the surface of the skin
what physiological changes occur when the body temperature is too low
vasoconstriction - blood vessels near the surface of the skin contract, less heat is radiated away
shivering - respiration allows muscles to contract, exothermic so heat energy is released
sweating stops
