Homeostasis Flashcards
what is homeostasis?
the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
why is homeostasis important?
it maintains optimal conditions for enzymes and all cell functions
what does homeostasis control?
- body temp
- water levels
- blood glucose concentration
- ion levels
what controls homeostasis?
- receptors=detect stimuli
- co-ordination centres (brain+spinal chord+pancreas)=recieve & process info from receptors
- effectors (musclees+glands)= carry out response to restore optimum levels
what is a negative feedback loop?
a type of regulatory system that helps to maintain conditions in the body within an ideal range
what does the nervous system allows us to do?
- react to our surroundings
- co-ordinate our behaviour
conscious action
stimulus –> receptor –> sensory neurone –> coordinator (brain) –> motor neurone –> effector –> response
what is the reflex arc?
- stimulus detected by receptor
- electrical impulse carried to sensory neurone to CNS
- dendrites of sensory neurone=synapse=electrical impulse diffuses across through a chemical neurotransmitter to relay neurone in spinal cord
- electrical impulse carried through spinal cord
- reaches synapse= diffuses across through chemical neurotransmitter
- reaches motor neurone= carries electrical impulse to effector= carries put the response (a reflex)
why are reflexes important?
they protect us
why are reflexes quick?
they don’t pass through the brain
required practical: reaction time
- The person being tested should sit with arm resting on edge of table
- They should hold a ruler vertically between thumb and index finger at 0 cm
- let go at the ruler with no warning
- the person should catch the ruler as quickly as they can
- reaction time measured with the number they catch the ruler at
- read the number above the thumb
- repeat and calculate a mean
- the person being tested should then have a caffeinated drink eg. a can of coke
- after 10 mins repeat experiment again, their reaction time should speed up
- variables you need to control: same person, same hand, ruler dropped from same height
characteristics of the brain
- controls complex behaviour
- made of billions of interconnected neurones and has different regions that carry out different functions.
what are some key brain areas?
cerebral cortex (outer wrinkly layer of brain)
cerebellum or little brain (back of brain)
medulla or brain stem (base of brain, top of spinal cord)
what are their functions? Brain
- cerebral cortex=consciousness, intelligence, memory, language, senses
- cerebellum=controls balance, co-ordination
- medulla= controls unconscious activities eg. breathing, heart rate
how can we study the brain?
- studying patients with brain damage
- electrically stimulating the brain
- MRI scans
how do they work? Brain
electrical stimulation:
- tiny electrodes put in different brain parts
-tiny jolts of electricity stimulate these regions and the effects can be observed
MRI scans:
- magnetic fields have an effect on the protons in the water molecules of the body
- functional MRIs=images of different regions of the brain that are active during different activities eg. listening to music or recalling a memory=detect changes in blood flow=more active regions=increased blood flow
why is it difficult to investigate brain functions?
- research of the brain is risky= research is slower
- research relies on dead people donating their brain
- may be unethical= x informed consent from individuals
why is it difficult to treat diseases? Brain
- incredibly complex and delicate organ=extremely difficult for neuroscientists to study it to find out how it works
- limited understanding=so complex and different regions can’t be studied separately=treating brain damage+disease is very difficult;
- any potential treatment carries risks of further damage=more problems eg. speech or motor issues, permanent personality changes
pros and cons of treating brain damage/disease
- benefits=improving the quality of someone’s life (as the procedure is used to treat a disorder of some kind)
- risks=more permanent damage, some of these will be because we still don’t fully understand how the brain and nervous system works
- damaged neurones are hard to repair+they don’t repair themselves+ x way to repair them developed
- damage eg tumours=difficult to remove= x easily accessible
- surgery=dangerous=intricate procedure
- high risk of damage=tissue very delicate
what is the eye?
sense organ containing receptors sensitive to light intensity and colour.
what are the parts of the eye?
- retina
- optic nerve
- sclera
- cornea
- iris
- ciliary muscles
- suspensory ligaments
how are they adapted? Eye
- retina - has 2 types of receptors (sensitive to colour/light)
- optic nerve - carries signals from retina to brain
- sclera - tough, supporting eye wall
- cornea - transparent outer layer (refracts light into eye)
- iris - coloured part of eye (controls size of pupil)
- ciliary muscles - control shape of lens
- suspensory ligaments - control shape of lens
what is accommodation?
the process of changing the shape of the lens to focus on near or distant objects.
how does the eye focus on near objects?
- ciliary muscles contract
- suspensory ligaments loosen (slack)
- lens is then thicker and refracts light rays strongly.
how does the eye focus on far objects?
- ciliary muscles relax
- suspensory ligaments are pulled tight (taut)
- lens is then pulled thin and only slightly refracts light rays.
what the 2 common eye defects?
- myopia (short sighted)
light focuses before retina - hyperopia (long sighted)
light focuses behind retina
how can they be treated? Eye
myopia
- concave lenses
hyperopia
- convex lenses
both
- hard/soft contact lenses
- laser eye surgery
- lens replacement
what is thermoregulation?
how body temp is controlled
done by thermoregulatory centre in brain
