B5 - Homeostasis And Response Flashcards
What is homeostasis?
Maintaining a stable internal environment for cells & enzymes to function properly
We have automatic control systems that regulate our internal conditions (e.g. water, temperature, & blood glucose levels)
Homeostasis ~ What are the 2 automatic control systems that regulate our internal conditions?
2 systems:
nervous system - rapid, short term, temporary response
endocrine system - slower, longer acting, sometimes permanent response
What is negative feedback?
If something in your body gets too high/too low, your body tries to reverse this by using negative feedback
How does negative feedback work?
- Receptor detects a stimulus - level is too high
- The coordination centre receives & processed the information, then organises a response
- Effector produces a response, which counteracts the change & restores the optimum level
Level decreases
- Receptor detects a stimulus - level is too low
- The coordination centre receives & processed the information, then organises a response
- Effector produces a response, which counteracts the change & restores the optimum level
Level increases
Sometimes the effectors can change the level too much in the opposite direction; the receptor detects this & negative feedback starts again.
What is the nervous system?
What are the parts of the nervous system?
Allows us to react to our surroundings & co-ordinate our behaviour
- Central nervous system (CNS)
= brain & spinal cord - Peripheral nervous system (PNS)
= nerves
What is a neurone?
What are the types of neurones?
Neurone = nerve cell
- they transmit information as electrical impulses
- Sensory neurone
= carries information from a receptor to CNS - Relay neurone (in CNS)
= joins sensory neurone to motor neurone - Motor neurone
= carries electrical impulses from CNS to erectors
What are receptors?
What are effectors?
What are the 2 types of effectors?
Receptors = specialised cells that detect a stimulus
(E.g. tastebuds, light sensitive cells in eyes, pressure receptors in skin, vibration sensitive cells in ears, etc)
Effectors = cause a change / response
1. Muscles (contract)
2. Glands (secrete hormones)
How does the nervous system work?
- Receptor
- Sensory neurone
- Relay neurone
- Motor neurone
- Effector
- Response
(2) Sensory neurones transmit signals to CNS
(3) Relay neurone processes the signal
(4) Motor neurone transmits the signal to the effector
(5) Effector carries out response
What is a synapse?
How do they work?
Synapse = a gap between 2 neurones
(They connect neurones)
- When an electrical impulse get to the end of a neurone it can’t go any further
- The nerve signal is transferred by chemicals which diffuse across the gap
- These chemicals then set off a new electrical signal in the next neurone
What are reflexes?
What do they do?
What is a reflex arc?
Reflexes
= rapid automatic responses to certain stimuli that don’t involve the conscious part of the brain
- help prevent injury
- help maintain homeostasis by regulating physiological processes
(E.g. control of heartbeat, control of breathing, & muscle contraction)
Reflex arc
= the passage of information in a reflex (from receptor to effector)
What is reaction time?
What factors affect reaction time?
(Learn practical - investigating reaction time)
Reaction time
= Time it takes to respond to a stimulus
Age, gender, drugs & alcohol
How do insulin and glucagon control blood glucose levels?
Insulin
= a hormone that lowers BGL
Glucagon
= a hormone that increases BGL
If BGL are too high:
1. Pancreas secretes insulin
2. Glucose moves from the blood into the liver & muscle cells
3. Glucose is turned into glycogen
If BGL are too low:
1. Pancreas secretes glucagon
2. Glycogen is turned into glucose
3. Glucose goes from the liver into the blood
Eating also increases BGL
& exercise decreases BGL
How does diabetes affect your ability to control blood glucose levels?
Type 1:
• Pancreas doesn’t produce insulin
• Insulin injections
Type 2:
• Body doesn’t respond to insulin
• Sometimes caused by obesity
• Change diet & exercise
What are the 4 stages of the menstrual cycle?
(Day 1 - 4)
1. period: lining of the uterus breaks down
(Day 4 - 14)
2. uterus lining builds up again - developing thick spongy layer with lots of blood vessels
(Day 14)
3. ovulation: egg develops in ovary & is released
(Until day 28)
4. uterus lining is maintained & if the egg is not fertilised the lining will break down again
What are the 4 hormones that control the menstrual cycle?
FSH
oestrogen
LH
Progesterone
What is FSH?
Where is it produced & what does it do?
Produced in: pituitary gland
Functions:
• Helps egg to mature
• Stimulates Oestrogen production
What is Oestrogen?
Where is it produced & what does it do?
Produced in: ovaries
Functions:
• Causes the lining of the uterus to grow
• Stimulates release of LH
• Inhibits FSH
What is LH?
Where is it produced & what does it do?
Produced in: pituitary gland
Functions:
• Stimulates ovulation
What is Progesterone?
Where is it produced & what does it do?
Produced in: ovaries
Functions:
• Maintains uterus lining in the second half of the menstrual cycle
(If pregnant)
• Levels of Progesterone stay high
• Progesterone inhibits FSH & LH
(If not pregnant)
• Levels of Progesterone drop
• So the lining can break down
What are the hormonal methods of contraception?
Oestrogen = prevents maturing & release of egg
Progesterone = produces thick mucus which stops sperm getting through
Combined pill = contains Oestrogen & Progesterone
• 99% effective
• no protection against STIs
• side effects: headaches & nausea
Other hormonal methods:
Oral pill, Patch, Implant, Injection
IUD = t shaped device that is put into the uterus & prevents implantation
What are the barrier methods of contraception?
Condoms
Female condoms
Diaphragm
Spermicide
What are the permanent methods of contraception?
Sterilisation
= cut fallopian tube OR
= cut sperm ducts
Abstinence = not having intercourse
Other:
“Natural” methods = avoiding intercourse when the woman is most fertile in her menstrual cycle
This is not very effective
What is one of the causes of infertility in women?
• Some women may not produce enough FSH
• This means the eggs do not mature & are not released
What are the pros and cons of fertility drugs?
Women can be given FSH & LH to help with fertility
Pros:
• Helps women get pregnant
Cons:
• Doesn’t always work
• Expensive
• Multiple pregnancies
• Stressful & upsetting
What is IVF?
In - vitro fertilisation
• FSH & LH given
• eggs collected from ovaries
• fertilised in a lab with sperm
• embryos become balls of cells
• implanted into uterus
What is Adrenaline?
Adrenaline = hormone that triggers the fight/flight/fright response
• Released from adrenal glands (on top of kidneys)
• Increases heart rate
• More O2 & glucose to cells
• Increases rate of respiration
• Releases more energy for muscle contraction
What is Thyroxine?
Thyroxine = hormone that regulates metabolism
• Released from thyroid glands (neck)
• TSH (thyroid stimulating hormone) is released form pituitary gland
• TSH causes the thyroid to release thyroxine
