Paper 2: B5: Homeostasis Flashcards
Homeostasis
an organisms ability to regulate/ control it’s internal conditions so crucial reactions can happen at optimum rates
Nervous system is made up of:
CNS: central nervous system
PNS: peripheral nervous system
CNS
central nervous system
brain and spinal cord
PNS
all other nerves
receptor
detects a change due to a stimulus (change in environment)
Nerve travels how?
receptor —> sensory neurone —-> relay neurone —-> motor neurone —-> CNS —-> effector —> muscle or gland
travels between neurones via the neurotransmitter chemicals in the synapse (gap of empty space between both ends of a neurone)
reflex arc
signal bypasses the brain and goes straight through spine to the effector - much faster than a conscious decision
Practical: reaction times
- drop ruler between finger and thumb
- measure distance fallen before caught, repeat, calculate mean
- independent vatiable: Stimulant (eg energy drink or coffee) increases neurotransmission
- depressant (alcohol) decreases neurotransmission
Cerebral cortex (brain)
responsible for higher level functions:
- memory
- speech
- problem solving
Cerebellum (brain)
Responsible for motor skills:
- movement
- balance
- coordination
Medulla oblongata ( brain )
Controls unconscious actions:
- heart and breathing rate
- signals to adrenal glands to release adrenaline
Pituitary gland ( brain )
allows doctors to see brain activity without surgery via MRI scans
master gland: sends signals to other glands
Accommodation for far objects
Ciliary muscles relax, suspensory ligaments tighten, thin lens meaning light is only refracted a little bit, focusing the light on the retina
accommodation for near objects:
ciliary muscles contract, suspensory ligaments slacken, thick lens meaning light is refracted more, meaning the light comming from the object converges to the retina so you can see a clear image
pupil
hole in the iris
can change size depending on the light intensity hitting the eye
cornea
transparent outer layer through which light enters the eye
has a slight lensing effect
sclera
white surface covering the rest of the eyeball
Retina cells
- rods: only detect light intensity
- cones, three types, which detect green blue or red wavelengths of light
optic nerve
provides information from the retina to the brain
Myopia
short sightedness
hyperopia
long sightedness
how can myopia and hyperopia be treated?
both treated with glasses, contact lenses or laser eye surgery
thermoregulation
body controlling it’s internal temp by the brain sensing blood temp then sending nervous and hormonal signals to various effectors around your body in order for the body to lose heat to its surroundings
Examples of thermoregulation (hot)
Vasodilation: blood vessels dilating (widening) to increase blood flow to the skin to increase rate of heat loss
Sweating: sweat glands produce water which evaporated taking away heat
Examples of thermoregulation (cold)
- hairs stand on end to trap air - insulation
- shivering - muscles produce more heat
- vasoconstriction: blood vessels contract to minimise blood flow to skin, minimising heat loss
endocrine system
system of glands that secrete hormones to send signals to effectors, transported via blood (slower than nervous system)
pancreas
secretes insulin (and glucagon) to control blood sugar
thyroid
controls growth, metabolism digestive function
adrenal gland
releases adrenaline
ovaries
release eggs and secrete hormones
testes
produce sperm
high blood glucose levels:
- pancreas’s secretes insulinę
- causes glucose to move from bloodstream into cells to be used for respiration
- excess glucose converted into glycogen as energy store
Glycogen
- excess glucose is converted into glycogen as energy store
low blood glucose levels
- pancreas secretes glucagon
- causes liver and muscles to convert glycogen back into glucose
( example of negative feedback)
Type 1 diabetes
pancreas cannot produce enough insulin, injections needed
type 2 diabetes
cells no longer absorb glucose as they should
obesity increases risk of developing this type of
