Please enable JavaScript.
Coggle requires JavaScript to display documents.
Topic 5 Homeostasis and response By Bethan Poole (5.3 Hormonal…
Topic 5 Homeostasis and response
By Bethan Poole
5.1 Homeostasis
Homeostasis: Regulating internal conditions (optimum conditions)
Conditions include
Water Content
Ion Content
Glucose Concentration
Body Temperature
All control systems include
Cells (receptors)- detect stimulus
Coordination centres- receives and processes information
Effectors- muscles or glands- brings about responses to restore optimum levels
5.2 The Human Nervous System
5.2.1 Structure and function
Involuntary Responses
Receptor: Eyes
Response: Light
Receptor: Nose
Response: Chemicals
Receptor: Skin
Response: Touch- Pain, Pressure and Temperature
Receptor: Tongue
Response: Chemicals
Receptor: Ears
Sound
Nerve cell
Long
Large surface area
Insulated coating
Nucleus
Cytoplasm
Cell membrane
Stimulus
: Triggers reaction, e.g. Hot Object
Receptors
: Detect the stimulus, receives info
Sensory Neurone
: Electrical impulses. takes to CNS
Relay Neurone
: Central nervous system, entire neurone is in the CNS
Motor Neuron
: Takes away from the CNS
Effector
: Creates response- i.e. the muscles contract
Synapse
The gap between two neurones
Electrical impulses reach the synapse and chemicals (neurotransmitters) are released and diffuse across the gap
Diffusion of neurotransmitters takes longer than electrical impulses to carry
5.2.2 The Brain
Controls complex behaviour
Made of billions of interconnected neurones
Has different regions carrying out different functions
Neuroscientists map regions of the brain by:
studying patients with brain damage
Electrically stimulating different parts of the brain
Using MRI scanning
Hard to investigate and treat brain disorders as brain is so complex
5.3.3 The Eye
Sense organ
Retina
Contains receptors cells- sensitive to light
Optic nerve
carries impulses from retina to brain
Sclera
forms a tough outer layer, with a transparent region at the front called the cornea
Iris
Controls the size of the pupil and the amount of light reaching the retina
Ciliary muscles and suspensory ligaments
Can change shape of the lens to focus light onto the retina
Accommodation- process of changing the shape of the lens to focus on near or distant objects
Near objects
Ciliary muscles contract
Suspensory ligaments loosen
Lens becomes thick and
refracts light rays strongly
Distant objects
Ciliary muscles relax
Suspensory ligaments pull tight
Lens pulls thin and only slightly refract light rays
Eye defects
Hyperopia
(Long sightedness)
Treated with convex lenses
Reduce the focal length
Myopia
(shortsightedness)
Treated with a concave lens
Extend the focal length
New technologies i.e laser eye surgery and contacts change the shape of the cornea and replace eye lenses
5.2.4 Control of Body Temperature
Too hot
Sweat glands release sweat
Sweat evaporates removing heat energy from skin
Vasodilation
Blood vessels dilate- more blood can flow so more heat is lost
Hair muscles relax so heat can escape
Too cold
Muscles contract rapidly, shiver, energy release as heat
Vasoconstriction
Blood vessels constrict- less blood flows, more heat conserved
Hair muscles contract , heat trapped
Shunt vessels- extreme conditions
Redirect blood to keep organs warm and less heat's lost elsewhere
Control systems
Receptors (cells)
In the thermoregulatory centre
Sensitive to temperature of blood
Coordination centres
Thermoregulatory centre in the brain
Effectors
Muscles surrounding the vessel contract or relax to control blood flow
5.3 Hormonal Coordination in Humans
5.3.1 Human Endocrine System
Made up of glands that secrete hormones directly into the blood stream
Hormones
Chemical messenger
Made by endocrine glands
Released and produced in small quantities
Slower than nervous impulses but longer lasting effect
Carried in blood
Pituitary Gland
Master gland
Secretes several hormones in response to body conditions
Main glands that produce hormones in the body
Adrenaline
Produced by adrenal glands - stress and fear
Increases heart rate, boosts delivery of oxygen and glucose
Fight or flight
Thyroxine
Produced by thyroid gland
Increases metabolic rate
controls growth and development in young animals
5.3.2 Control of body glucose concentration
Too high
Pancreas releases insulin - insulin converts glucose into
glycogen
Glycogen stored in liver
Glucose levels drop, less glucose
Too low
Pancreas releases glucagon- glucagon converts glucagon into glucose
Increases glucose levels as there is more glucose
Glucose goes back into blood stream
Blood glucose are monitored by the pancreas
Diabetes
Type 1
disorder where the pancreas fails to produce enough insulin
Characterised by uncontrolled high blood glucose levels
Normally treated with insulin injects
Type 2
Body cells no longer respond to insulin produce by pancreas
Carb controlled diet and exercise regime are common treatments
Obesity - high risk factor
Controlling sugar levels
Diet
Exercise
Insulin
5.3.3 Maintaining water and nitrogen balance in the body
Water leaves body from the lungs (respiration), from the skin (sweat) and in urine (along with ions and urea)
If blood concentration changes body will lose or gain too much water by osmosis
Balance of water and ions regulated by the kidneys
They excrete urea (waste product produced by live from break down of proteins and contains nitrogen)
Digestion of proteins due to excess amino acids
In the liver mine acids converted into ammonia-
deamination
Ammonia is toxic so converted to urea and sent to kidneys for safe excretion
Kidneys produce urine by:
1)Filtering the blood
2)
Selective reabsorption
of useful substances (glucose, some ions and water)
3) This leaves urea and excess water, to form urine
Process takes place in millions of small tubes in kidneys called tubules
Water level in the body controlled by a hormone
ADH
Released by the pituitary gland when bloods to concentrated
Passes in the blood to the kidney tubules where it causes more water to be reabsorbed back into blood
Kidney failure
Dialysis
Pros
No shortage
No need for immune-suprressant drugs
Cons
Patients must limit salt and protein intake
Expensive for the NHS
Impacts lifestyle
A dialysis machine takes over the role of the kidneys
Transplant
Pros
can lead a normal life without watching diet
cheaper for NHS long term
Cons
Must take immuno-supressent drugs- increase risk of infection
Shortage of organ donors
only last 8-9years average
Any operation carries risks
5.3.4 Hormones in human reproduction
Menstrual Cycle
Puberty
Sex hormones cause secondary sexual characteristics to develop
Oestrogen
From ovaries, main female sex hormone
Testosterone
Main males sex hormone, produced in the testes stimulates sperm production
5.3.5 Contraception
Contraceptive Pill
Uses oestrogen and progesterone as contraceptives
Can be both oestrogen and progesterone or progesterone only
Works by:
Stopping FSH Production
Stopping the ovaries maturing the eggs
Other Methods
Injection, implant or skin patch
Slow release progesterone to inhabit the maturation and the release of the eggier a number of months or years
Barrier methods
Prevent sperm reaching egg
I.e. condom or diaphragms
Intrauterine devices
Prevent the implantation of an embryo or release of hormone
Spermicidal agents
Kill or disable sperm
Abstaining from intercourse when egg may be in the oviduct
Surgical methods of male and female sterilisation
5.3.6 The use of hormones to treat infertility
Fertility Treatments
Giving FSH injections to mature eggs
Giving LH injections to release eggs
IVF
Drawbacks
Cost
Emotionally and physically stressful
Low success rates
Can lead to multiple births, risky for mother and babies
FSH and LH used to mature eggs
Eggs collected and fertilised by sperm in a lab
Fertilised eggs develop into embryos
One or two embryos are inserted In to the mother's womb
5.3.7 Negative feedback
Temp control
Metabolic rate
Glucose control
Water control
Stress
5.4 Plant Hormones
5.4.1 Control and coordination
Tropism
Positive
Movement towards a stimulus
Negative
Movement away from a stimulus
A growth movement in response to a stimulus
Auxin in shoots speeds up growth
Auxin in roots slows down growth
Phototropism and auxins (light from one side)
More auxins on the shaded side of shoot so shaded side grows faster making bright side bend towards the light
Leaves face light so more photosynthesis
Geotropism (gravitropism) and auxins
Auxins slow down the growth on the lower side of the roots so roots curve down
Auxins speed up growth on the lower side of the stem so the stem curves up
5.4.2 Use of plant hormones
Auxins can be used in
Weed killers
Rooting powder
Promoting growth in a tissue culture
Gibberellins used to
End seed dormancy
Promote flowering
Increase fruit size
Ethene used in the food industry to control ripening of fruit during storage and transport
