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Homeostasis
regulation of conditions inside the body to maintain a stable internal environment, in response to internal and external conditions
What things need to be controlled?
Core body temperature (enzymes)
pH (enzymes)
Blood glucose concentration (respiration)
Water and ion content (osmosis)
What is a reflex?
involuntary response to a stimulus
Receptors
specialised cells that detect stimuli - changes in environment
Coordination centres
process the information received from receptors and coordinate response eg. brain, spinal cord
Effectors
muscles or glands that carry out response to stimuli
Function of the nervous system
enables humans to react to their surroundings and coordinate their behaviour
Central Nervous System (CNS)
Coordination centre consisting of brain and spinal cord which contains relay neurones that coordinate the response of the effectors
Sensory neurones
carry impulses from receptors to CNS
Relay neurones
carry impulses through spinal cord
Motor neurones
carry impulses from the CNS to effectors
Synapses
junctions between connected neurones
How neurones pass impulses
When an impulse arrives at a synapse with a neurone a chemical is released which diffuses across the synapse and sets off a new electrical impulse at the next type of neurone
Order of response of nervous system
Stimulus -> Receptor -> Coordinator (CNS) -> Effector -> Response
Cerebral cortex
concerned with consciousness, memory, intelligence, language
Cerebellum
concerned with coordination of muscle activity
Medulla
concerned with unconscious activity eg. heart beating, breathing
Pituitary gland
produces hormones
Hypothalamus
regulating centre for temperature and water balance in body
3 ways scientists can study the brain
Studying people with brain damage
Electrically stimulating the brain
Scanning the brain: CT, MRI
Electrical stimulation (studying brain)
expose the brain by removing too of skull, stimulate different areas and see what effect it has
MRI scans (studying brain)
enables scientists to see exactly which area of the brain is affected and link behaviours to it
CT scans
X rays to produce cross sectional images of brain
Why is it so difficult to study the brain?
Wide range of things that could go wrong
Difficult to access and fix as it is well protected by skull an surrounding fragile brain tissue
Difficult to target with medications as it is so complex
Retina
contains light sensitive cells
Optic nerve
transmits impulses to brain, so we can see what we're looking at
Sclera
tough, white protective layer of eye
Cornea
refracts light
Iris
controls amount of light entering eye
Ciliary muscles
alters thickness of lens for focus
Suspenseful ligaments
attach lens to CM
Fovea (Yellow Spot)
most sensitive part of the retina where we sense colour
Pupil
lets light into eye
How our brain receives information about light entering eye
Retina contains light sensitive cells that pass impulses along neurone to the optic nerve, which can then be interpreted in the brain
Iris reflex - Bright light
circular muscles contract, radial muscles relax
pupil constricts, less light in eye
Iris reflex - Dim light
circular muscles relax, radial muscles contract
pupils dilate
more light enters the eye
Accommodation of the eye - Distant objects
ciliary muscle relax (outwards away from lens), suspension ligaments pulled tight
lens more rounded and pulled thin, less convex
lens refracts light less
Accommodation of the eye - Near objects
ciliary muscles contract (inwards towards lens), suspension ligaments slack
lens more rounded and relatively thick, more convex
lens refracts more light - light rays focus on retina
Myopia
shortsighted
near objects yes
distant objects no (light focused in front of retina)
Myopia treatment
Wear glasses with a concave lens - spread light from distant objects before it reaches the eye
Hyperopia
long sighted
distant objects yes
near objects no
(lens cannot refract rays of light strong enough)
Hyperopia treatment
Wear glasses with convex lens - bring rays of light together before they reach the eye
Reaction time practical - Method
1. Person 1 sits on a stool with good upright posture and places the forearm of their non-dominant arm across the table with their hand overhanging the edge
2. Person 2 holds a ruler vertically. The 0cm mark should be between person 1's thumb and first finger
3. Person 2 tells person 1 to prepare the catch the ruler and drops it at a random time. Person 1 has to catch the ruler with their thumb and first finger as quickly s possible when it drops
4. Person 2 records the measurement on the ruler that is level with the top of person 1's thumb
5. Test is repeated a number of times and a mean is calculated.
Reaction time variable
Independent variable - person having RT tested
Dependent variable - reaction time
Control variable - starting distance between thumb and first finger, room conditions eg lighting, background noise, where you measure from.
