B10 - The human nervous system Flashcards
What is homeostasis
staying alive - the regulation of internal conditions to respond to stimuli
What is the main reason for maintaining specific conditions
to make sure enzymes work optimally
What are three internal conditions that need to be controllled
Body temperature
- water content
- blood glucose concentration
What are some stimuli the body must respond to
sunlight level
- temperature change
- eating a meal
What are receptors
cells that detect stimuli
What are coordination centres
areas that recieve and process the information from receptors. They send signals and coordinate the response of the body e.g. the brain, hormonal system, spinal cord, pancreas
What are effectors
muscles or glands that bring about responses to stimuli
How fast do nerve signals travel
between 1 and 120 metres per second
Where are receptor cells usually gathered
in organs such as eyes and skin
What happens after a stimulus is detected
stimulus -> receptor -> sensory neurone until the Central Nervous System -> relay neurones in CNS -> motor neurones to body parts -> effectors
What does CNS stand for
- what is it
Central Nervous System
- brain and spinal cord
What is a reflex action
an automatic, subconscious, quick response
Why are reflexes useful
they can save the body from danger
What part of the CNS do reflexes go through
- What is the path taken called
spinal cord
- reflex arc
Why don’t reflex arcs go through the brain
quicker response
What happens at the synapse
electrical impulses trigger release of chemicals that diffuse across and are picked up on the other side
What are the five main parts of the brain
- cerebral cortex
- cerebellum
- medulla
- hypothalamus
- pituitary gland
What is the cerebral cortex concerned with
consciousness, intelligence, memory and language
What is the cerebellum concerned with
coordinating muscular activity and balance
What is the medulla concerned with
unconscious activities e.g. movement of gut, heartbeat and breathing
What are three ways we can understand the brain
studying people with brain damage
- stimulating parts of the brain
- MRI scans
What does MRI stand for
- what does it do
Magnetic Resonance Imaging
- shows us which part of the brain has been affected
What are some issues with understanding the brain
- easily damaged and destroyed
- behind the skull
- very complex
- don’t know much about it
Where are the light sensitive cells in the eye located
retina
What are the 9 main parts of the eye
- iris
- lens
- pupil
cornea - sclera
- suspensory ligaments
- ciliary muscles
- optic nerve
- retina
What is the sclera
the white outer layer of the eye
What is the transparent part of the sclera known as
- where is it
cornea
- at the front
What does the curved surface of the cornea do
let light in and focus it on the retina
What does the iris do
control the size of the pupil to control the amount of light entering
What happens when bright light hits the eye
circular muscles contract
radial muscles relax
pupil constricts
What happens when dim light hits the eye
circular muscles relax
radial muscles contract
pupil dilates
What happens to light after it passes the pupil
goes through the lens
What holds the lens in place
suspensory ligaments and ciliary muscles
What does the lens do
focuses light on the retina
What happens when light hits the retina
light sensitive cells are stimulated which send impulses along sensory neurones in the optic nerve. The brain interprets these as a visual image
What is the blind spot
the place on the retina where the optic nerve is
What direction is the image formed on the retina
inverted
What is the name for the lens changing to see near and far
accomodation
How does the the lens focus a distant object
ciliary muscles relax, suspensory ligaments pulled tight, lens is made flat and thin
How does the lens focus a near object
ciliary muscles contract, suspensory ligaments loosen, lens is thicker and more curved
Why do many older people need reading glasses
accommodation becomes more difficlt
What is the name for short-sightedness
myopia
What is the name for long-sightedness
hyperopia
What happens in myopia
- what type of lens is it commonly treated with
light is focused in front of the retina
- concave
What happens in hyperopia
- what type of lens is it commonly treated with
light is focused behind the retina
- convex
What are four common ways of overcoming myopia and hyperopia
- contact lenses
- laser eye surgery
- replacement lenses
- glasses
What are the main risks of lens replacement
damage to retina, cataracts, infections
