Topic 5 - Homeostasis Flashcards
What is homeostasis?
The regulations of conditions inside a body or cell
Why is homeostasis important?
To maintain optimum conditions in response to an internal or external conditions
What three things does homeostasis control?
-blood glucose concentration
-temperature
-water levels
What is a receptor?
A cell which detects a stimuli
What is an effector?
Muscles or glands, which bring about responses which
restore optimum levels.
What is the point of the nervous system?
The nervous system enables humans to react to their surroundings and
to coordinate their behaviour.
Name two parts of the central nervous system
-spinal cord
-brain
How are messages passed through the nervous system?
Via. electrical impulses
What is the reflex arc in order
Stimuli, receptor, sensory neurone, synapse, relay neurone, synapse, motor neurone, effector, response
What is a reflex action?
Automatic and rapid actions which do not involve the conscious part of the brain.
What is a synapse?
The gap between two neurones where messages are sent by chemical diffusion
Why are reflex actions important?
To avoid damage to the cells
Why do synapses slow down a reflex action?
Chemical diffusion is slower than electrical impulses
What is the brain made up of?
Millions of interconnected neurones
What are the three main parts of the brain?
-Cerebral cortex
-Cerebellum
-Medulla
What is the function of the cerebral cortex?
conscious thought
What is the function of the cerebellum?
balance and movement
What is the function of the medulla?
unconscious activities such as breathing, heart rate.
Why is investigating brain function and treating brain damage and disease problematic?
The complexity and delicacy of the brain makes investigating and treating brain disorders very difficult.
What is the function of the retina?
retina- detects light
What is the function of the optic nerve?
optic nerve- carries electrical impulses to the CNS
What is the function of the cornea?
cornea- refracts (bends) light as it enters the eye
What is the function of the sclera?
sclera- outer layer protects the eye
What is the function of the iris?
iris- controls how much light enters the eye
What is the function of the ciliary muscles?
ciliary muscles- contract or relax to control focusing
What is the function of the suspensory ligaments?
suspensory ligaments- connect cliliary muscle to the lens
what part of the body controls and monitors temperature?
The thermoregulatory centre in the brain
where are temperature receptors located in the body?
In the skin
What 2 things happen when body temperatures are too high
Vasodialation and sweating
What 3 things happen when body temperatures are too low?
Vasoconstriction, shivering and hairs standing on end.
How are messages passed on in the human endocrine system?
Through hormones in the bloodstream
What are the six glands and the hormone they produce?
Pituitary gland - many hormones
Thyroid - Thyroxin
Adrenal - Adrenaline
Pancreas - insulin
Ovaries - oestrogen
Testes - testosterone
Which is faster the endocrine or the nervous system?
The nervous system as electrical impulses travel much faster
What is accommodation?
How the eye can adjust to focus on things at different distances
How do we focus on objects at far distances?
The ciliary muscles relax
How do we focus on objects at close distances?
The ciliary muscles contract
What are two common defects of the eyes?
Myopia (short-sightedness): the light is refracted too much, so the focal point is in front of the retina. Hyperopia (long-sightedness): the light is not refrated enough, so the focal point is beyond the retina.
What is myopia?
Myopia (short-sightedness): the light is refracted too much, so the focal point is in front of the retina.
What is hyperopia?
Hyperopia (long-sightedness): the light is not refrated enough, so the focal point is beyond the retina.
What are ways to correct vision?
Glasses or laser eye surgery
What part of the body controls glucose levels
the pancreas
What happens if blood glucose concentration is too low?
the pancreas
produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood.
What is the treatment for type 1 diabetes?
Insulin injection
What happens if blood glucose concentration is too high?
the pancreas produces insulin that causes glucose to move from the blood into the cells. In the liver excess glucose is converted to glycogen for storage.
What hormone is produced when blood glucose is too high
insulin
What is type 1 diabetes?
A disorder in which the pancreas fails to produce sufficient insulin.
What is type 2 diabetes?
It occurs when the body cells no longer respond to insulin produced by the pancreas.
What is a risk factor for type 2 diabetes?
Obesity
How can type 2 diabetes be controlled?
A carbohydrate controlled diet and an exercise regime
What is released when blood glucose concentration is too low?
Glucagon
What happens to blood cells when there is too much water?
The cells gain water by osmosis and burst
What happens to blood cells when there is too little water?
The cells lose water by osmosis and shrivel.
In what 3 ways is water lost?
-breathing (exhalation)
-sweating
-urination
How are excess ions and urea lost ?
-sweating
-urination
How is excess protein dealt with in the body?
Protein is converted into amino acids which turns into ammonia through the process of deamination. The ammonia is toxic so it is immediately converted into urea which can be safely excreted.
What is produced in the kidneys and what does it contain?
Urine, containing water, urea and ions
What two processes take place in the kidneys?
Filtration - ions, water, glucose and urea are pushed out the blood stream into the kidney tubule
Reabsorbtion - some ions some water and glucose is reabsorbed back into the bloodstream
What does ADH do to the permeability of the tubule?
ADH increases the permeability of the kidney tubule
What happens to ADH levels when there is too little water?
The pituitary gland releases more ADH which make the tubule more permeable meaning that more water will be reabsorbed so water levels return to normal.
Describe the process of dialysis
Blood is filtered by a machine and returned to the body. Must be done at least 3 times a week.
What are the two treatments for kidney failure?
Dialysis and kidney transplant
What is an advantage and disadvantage of dialysis
+ provides help whilst waiting for a donor so the patients body can function
- Very restrictive lifestyle , 3 times a week
What is an advantage and disadvantage of kidney transplants?
+ Patients can lead a normal lifestyle, cheaper long term
- Shortage of kidney donors, risk of rejection
Name the male reproductive hormones and its function and where it is produced
Testosterone - produced by testes, sperm production begins and voice deepens
Name the female reproductive hormones and its function and where it is produced
Oestrogen - produced by the ovaries, menstrual cycle begins, breast enlarge
What is ovulation?
The release of an egg from the ovary
How long des the menstrual cycle last?
Aprox. 28 days
What is the role of FSH
FSH: causes egg to mature in the ovary.
What is the role of LH
LH: causes ovulation.
What is the role of oestrogen and progesterone?
Oestrogen and progesterone: develop and maintain uterus lining
How do all the female hormones interact during the menstrual cycle?
FSH: causes oestrogen to be released. Oestrogen: stops FSH and starts LH production. LH: stops oestrogen and casues progesterone release.
Name two non hormonal contraceptives
Condoms, copper coil
Name 3 types of hormonal contraceptives
Pill, Patch, injection
What is the role of hormones in hormonal contraception?
The hormones inhibit the release and maturity of an egg
What is an IUD and what does it prevent?
A copper IUD prevents the implantation of a fertilised egg in the uterus
What are two other methods of contraception?
Abstinence (not having sex), sterilisation (permanently restricting pregnancy)
How is IVF taken place?
An egg is taken from a woman and fertilised by sperm in a lab. An embryo can then develop in the lab and be inserted into a uterus
What are some drawbacks of IVF?
-Expensive
-Low success rate
-Emotionally and Physically straining
How are hormones used in IVF
To stimulate egg release and maturity
What is IVF?
In-vitro-fertilisation, fertilising an egg outside the female body
What is the role thyroxine ?
To stimulate basal metabolic rate
What is the role of adrenaline?
To increase heart rate in stressful situations
What is a negative feedback cycle?
A mechanism to lower levels of something which is too high, and raise levels of something that is too low.
Name two examples of negative feedback cycles
-Menstural cycle
-Control of water levels
-Blood glucose concentration
What is phototropism?
The plants response to light, plant will grow towards the light
What is gravitropism?
The plants response to gravity, shoots grow away from gravity, roots grow towards gravity
What causes gravitropism and phototropism?
Uneven distribution of auxin
What is the role of gibberellins ?
Initiating seed germination
What is the role of ethene?
Controls cell division and the ripening of fruits
Describe the use of auxins
-as weed killers
- as rooting powders
- for promoting growth in tissue culture.
Describe the use of ethene
used in the food industry to control ripening of fruit during
storage and transport.
