B5 - Homeostasis Flashcards
Homeostasis
The maintenance, balance and regulation of a constant internal environment
Why do we need homeostasis?
Cells need the right conditions to function properly, including the right right conditions for enzyme action.
Give some automatic control system examples in your body
- Nervous
- Hormonal
Homeostasis examples
- Body temperature
- Blood glucose level
- Water potential
- Negative feedback
- pH
- CO2 concentration
What are all automatic control systems made up of?
Receptors, coordination centres and effectors
Negative feedback
- When the level of something gets too high or too low (from the ideal or set point), the body uses negative feedback to bring it back to normal
Negative feedback order for high/low levels
1) receptors detects a stimulus level is too high/too low
2) Coordination centre receives and processes the information, then organises a response
3) Effector produces a response, which counteracts the change and restores the optimum level
Why do humans need the nervous system?
So they can react to their surroundings and coordinate their behaviour
Central Nervous System
- In vertebrates, it consists of the brain and spinal chord only.
- In mammals, the CNS is connected to the body by neurones and motor neurones
Sensory neurones
Neurones that carry information as electrical impulses from the receptors to the CNS
Motor neurones
Neurones that carry information as electrical impulses from the receptors to the CNS
Effectors
All the muscles and glands, which respond to the nervous impulses
Receptors
- Cells that detect stimuli
- Can form part of larger, complex organs
- Different types for different purposes (taste receptors, sound receptors etc)
Effectors
- Respond to nervous impulses and bring about a change
- Muscles and Glands
How do muscles react to nervous impulses
Contract
How do glands react to nervous impulses?
Secrete hormones
Order of CNS
1) Stimulus
2) Receptor
3) Sensory Neurone
4) CNS
5) Motor Neurone
6) Effector
7) Response
Stimulus
Any change in your environment (sound, light, taste, pressure, touch, smell etc.)
Synapse
The connection between 2 neurones
How do the nerve signals transfer?
Chemicals diffuse the signal across the gap which then set off a new electrical signal in the next neurone
Reflexes
Rapid, automatic responses to certain stimuli that don’t involve tge conscious part of the brain
Give examples of reflexes
- Eye adjusting to light concentration
- Adrenaline levels
Reflex arc
The passage of information in a reflex (from receptor to effector)
Order of Reflex Arc
1) Neurones in reflex arcs go though the spinal cord or through an unconscious part of the brain
2) Stimulus detected by receptors, impulses sent along sensory neurone to a relay neurone in the CNS
3) Relay neurone triggered with synapses
4) Impulses sent to motor neurone
5) Impulses travel along the motor neurone to the effector
What factors can affect reaction time?
- Age
- Gender
- Drugs
Hormone
A chemical substance, produced by a gland and released directly in the bloodstream, which alters the activity of specific target organs
Target organs
The organ where they are affected by a specific hormone
Where are hormones produced?
Endocrine glands
Endocrine system
Various endocrine glands which release hormones (body’s response to the environment)
Give some examples of glands
- Pituitary glands
- Thyroid
- Ovaries
- Testes
- Pancreas
- Adrenal gland
Pituitary gland
The ‘master gland’ because there hormones act on other glands, directing them to release hormones that bring about change. It produces hormones that regulate the body conditions
Thyroid
Produces thyroxine
Ovaries
Produces, oestrogen which is involved in the menstrual cycle
Testes
Produces testosterone which controls puberty and sperm production in males
Adrenal gland
Produces adrenaline
Pancreas
Produces insulin which is used to regulate the blood glucose level
Differences between nerves and hormones
Nerves are fast, act for a very short time and on a very precise area. Hormones are slower, act for a long time, and in a more general way
How can blood glucose levels be regulated without insulin and glucagon (not diabetes)?
- Metabolism of cells removes glucose from the blood
- Vigorous exercises remove much more glucose from the blood
- Excess glucose can be stored in the liver and in the muscles
How does the Pancreas regulate blood glucose level?
Releasing hormones such as insulin and glucagon
What happens if there is too much glucose?
- Negative impact on osmosis
- Excess glucose turned into glycogen and will be stored
What happens of there is too little glucose?
- Organism cannot produce enough energy from respiration
- Stored glycogen will be converted back into glucose
What happens when blood glucose levels are too high?
- Insulin secreted by Pancreas
- Receptors stimulated by the insulin
- Cells are forced to absorb more glucose
- Insulin and blood glucose levels stabilize
What happens if blood glucose levels are too low?
- Glucagon secreted by pancreas
- Liver stimulated by glycogen and turns glycogen into glucose
- Glucose levels stabilize
Glucagon
Release some of the stored glycogen into the blood
Insulin
Sends signal to liver, muscles and other cells to store excess glucose
Diabetes
The condition where it affects the ability to conteol blood glucose level
Type 1 diabetes
- Pancreas causes little to no insulin
- Develops during childhood
What can help patients with type 1 diabetes (note that there is no cure)?
- Insulin therapy (depends on the fitness level of the person)
- Limited diet
- Exercise
Type 2 diabetes
- A person becomes resistant to their own insulin (the pancreas still produces insulin)
- Usually develops later in life
- Overweight is also a factor
Type 2 diabetes causes
- Obesity
- Lack of exercise
- Unhealthy diet
How to control type 2 diabetes?
- Eating a carbohydrate-controlled diet
- Getting regular exercise
- Injecting insulin not good because its ineffective
Puberty
- Body starts releasing sex hormones that trigger off secondary sexual characteristics
Puberty in men (hormones)
- Testes produces testosterone which stimulates sperm production
- Underarm, facial and pubic hair grow
- Voice deepens
Puberty in woman (hormones)
- Ovaries produce oestrogen
- Starts menstrual cycle
- Breasts enlarge
- Underarm and pubic hair grow
(Stage 1) Day 1 menstruation cycle
- Menstruation starts
- Uterus lining breaks down for about 4 days
(Stage 2) Day 4 menstruation cycle
- Uterus lining builds up again
- From day 4 to 14, uterus lining builds up into a thick spongy layer full of blood vessels, ready to receive a fertilised egg
(Stage 3) Day 14 menstruation
- Ovulation happens
(Stage 4) Day 28 menstruation cycle
- Wall is maintained for about 14 days until day 28
- If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down and the whole cycle starts again
Ovulation
An egg develops and is released
What are the 4 hormones which control the menstruation cycle?
FSH, Oestrogen, LH, Progesterone
- FSH (Follicle-Stimulating Hormone) 1-4
- Produced in the pituitary gland
- Causes an egg to mature in one of the ovaries
- Stimulates the ovaries to produce oestrogen
- Lining breaks down and results in ‘period’
- Oestrogen 4-14
- Produced in the ovaries
- Causes the lining of the uterus to grow
- Stimulates the release of LH (which causes the release of an egg) and inhibits the release of FSH
- LH (Luteinising Hormone) 14
- Produced by the pituitary gland
- Stimulates the release of an egg at day 14 (ovulation)
- Progesterone 15-28
- Produced in the ovaries by the remains of the follicle after ovulation
- Maintains the lining of the uterus during the second half of the cycle. When the level of progesterone falls, the lining breaks down.
- Inhibits the release of LH and FSH
Fight or Flight
Adrenaline is used to prepare the body to move and think quickly in response to danger
Adrenaline
- Prepares the body for a ‘fight or flight’ response
- Enlarges air passages of lungs and alters metabolism order to boost delivery of oxygen and glucose to the brain and muscles
- Adrenaline increases heart rate and blood pressure, dilates eye pupils
Thyroxine
Involved in regulating things like the basal rate of metabolism, heart rate and temperature. It is also responsible for regulating the growth and brain development of young animals
Fertility drugs
- Drugs that contain a mixture of FSH and LH
- Can cause n egg to be released in the ovaries
IVF (In-vitro fertilisation)
- FSH and LH given to stimulate lots of growth of eggs
- Collected before being fertilised in a petri dish with sperm from father
- Grow into embryos and are implanted into woman’s uterus
Why might a woman be infertile?
Not enough FSH
