B5 Flashcards
What is homeostasis?
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
What does homeostasis do?
- It maintains optimal conditions for enzyme action and all cell functions
- In the human body these include the control of blood glucose concentration,body temperature and water levels
What do automatic control systems involve?
Nervous responses or chemical responses
What do all control systems include?
- Cells called receptors, which detect stimuli (changes in the environment)
- Coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors
- Effectors, muscles or glands, which bring about responses which restore optimum levels.
What is the structure of the nervous system?
- The nervous system consists of the brain and spinal cord, which together form the central nervous system (CNS)
- The CNS is linked to sense organs by neurones, which form the peripheral nervous system (PNS)
- Neurones (nerve cells) are specialised cells which carry electrical impulses
How is the structure of the nervous system adapted to its functions?
- A bundle of neurons is called a nerve
- The features of neurons help them to carry out their function efficiently: they have a long fibre (axon ) so they can carry messages up and down the body over long distances
- In a stimulated neuron, an electrical nerve impulse passes along the axon
Structure of the nervous system in symbol equations
Stimulus –> receptor –> coordinator –> effector –> response
What does the nervous system enable humans to do?
- React to their surroundings
- Co-ordinate their behaviour
What are the structures in a reflex arc?
- Sensory neurone
- Sypnapse relay neurone
- Motor neurone
What is the structure of a sensory neurone?
Contains a cell body, axon and dendrites
What is the structure of a sypnapse relay neurone?
Contain lots of short dendrites, a cell body and a long axon
What is the structure of a motor neurone?
Contains a cell body, axon and dendrites
How is te structure of the sensory neurone related to its function?
The neurones that carry information as electrical impulses from the receptors to the CNS
How is the structure of the sypnapse relay neurone related to its function?
- Relay neurons connect various neurons within the brain and spinal cord and are easy to recognize due to their short axons
- Alike to motor neurons, interneurons are multipolar
- This means they have one axon and several dendrites
How is the structure of the motor neurone related to its function?
- The dendrites use these structures to send and receive information from other neurons
- The axon is the long extension structure stemming from the soma
- The axon works to transmit the information it receives down its body to the dendrites at the end of the neuron
What are reflex actions?
- Reflex actions are automatic and rapid
- They do not involve the conscious part of the brain
Note:
AQA says that students should be able to:
- Extract and interpret data from graphs charts and table about the functioning of the nervous system
- Students should be able to translate information about reaction times between numerical and graphical forms
Practical 6:
AAA
What are the principles of hormonal coordination and control by the human endrocine system?
- The endocrine system secretes hormones into the bloodstream from glands throughout the body
- Hormones produce an effect on specific target organs in the body and cause an effect
What is the endocrine system?
- A system composed of glands which secrete chemicals called hormones directly into the bloodstream
- The blood carries the hormone to a target organ where it produces an effect
- Compared to the nervous system the effects are slower but act for longer
What is the pituitary gland?
- It is the ‘master gland’ which secretes several hormones into the blood in response to body conditions
- These hormones in turn act on other glands to stimulate other hormones to be released to bring about effects
Note:
AQA says students should be able to identify the position of the following diagram of the human body
- Pituitary gland
- Pancreas
- Thyroid
- Adrenal gland
- Ovary
- Testes
(Check CGP page 62 to see the diagram)
(Go to showbie to write out the diagram – Year 11 Biology -> B11.The Endocrine System –> Endocrine System introduction –> Organs to label)
What is blood glucose concentration?
The amount of glucose in the blood
What is blood glucose concentration controlled by?
It is monitored and controlled by the pancreas
What happens if the blood glucose concentration?
The pancreas produces the hormone insulin that causes glucose to move from the blood into the cells
In the liver and muscle cells, what is excess glucose converted into?
Glycogen for storage
How does insulin control blood glucose (sugar) levels in the body?
Insulin acts in the liver to reduce blood glucose concentration by: increasing glucose absorption from the blood by the liver and muscles; converting excess glucose to glycogen which is stored mainly in liver but also muscle; increasing respiration in the liver.
What is type 1 diabetes and how is it normally treated?
- A disorder in which the pancreas fails to produce sufficient insulin
- It is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections
What is type 2 diabetes and how is it normally treated?
- Where the body cells no longer respond to insulin produced by the pancreas
- A carbohydrate controlled diet and an exercise regime are common treatments. Obesity is a risk factor for type 2 diabetes
Note:
AQA says that students should be able to extract information and interpret data from graphs that show the effect of insulin in blood glucose levels in both people with diabetes and people without diabetes
What happens if blood glucose concentration is low?
If the blood glucose concentration is law, the pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood
How does glucagon interact with insulin in a negative feedback feedback cycle to control glucose (sugar) levels in the body?
- If the blood glucose level is too low, the pancreas releases the hormone glucagon
- This travels to the liver in the blood and causes the break-down of glycogen into glucose
- The glucose enters the blood stream and glucose levels increase back to normal
- This is an example of negative feedback
What is the roles of hormones during human reproduction and what is produced for men and women
During puberty, reproductive hormones cause secondary sex characteristics to develop, testosterone for men and oestrogen for women(these are the main reproductive hormones for their respective genders)
What is the roles of hormones during the menstrual cycle?
- Several hormones are involved in the menstrual cycle of a woman: follicle stimulating hormone (FSH) causes the maturation of an egg in the ovary
- Luteinising hormone (LH) stimulates the release of the egg
- Oestrogen is involved in repairing and thickening the uterus lining, progesterone maintains it.
What is testosterone?
A hormone produced by the testes which controls the development of male secondary sexual characteristics , for example, facial hair.
What is oestrogen?
- The oestrogen causes growth and repair of the lining of the uterus wall
- Oestrogen inhibits FSH
- When oestrogen rises to a high enough level it causes a surge in LH from the pituitary which causes ovulation where an egg is released from the follicle (Day 14 of the cycle).
Note:
AQA says that students should be able to extract and interpret data from graphs showing hormone levels during the menstrual cycle
What are the different hormonal methods of contraception?
- Oral contraceptives that contain hormones to inhibit FSH production so that no eggs mature
- Injection, implant or skin patch of slow release progesterone to inhibit the maturation and release of eggs for a number of months or years
- Barrier methods such as condoms and diaphragms which prevent the sperm reaching an egg
- Intrauterine devices which prevent the implantation of an embryo or release a hormone
- Spermicidal agents which kill or disable sperm
- Abstaining from intercourse when an egg may be in the oviduct
- Surgical methods of male and female sterilisation.
What are the different non-hormonal methods of contraception?
- Oral contraceptives that contain hormones to inhibit FSH production so that no eggs mature
- Injection, implant or skin patch of slow release progesterone to inhibit the maturation and release of eggs for a number of months or years
- Barrier methods such as condoms and diaphragms which prevent the sperm reaching an egg
- Intrauterine devices which prevent the implantation of an embryo or release a hormone
- Spermicidal agents which kill or disable sperm
- Abstaining from intercourse when an egg may be in the oviduct
- Surgical methods of male and female sterilisation.
How is fertility controlled?
By a variety of hormonal and non-hormonal methods of contraception
What is the use of hormones in modern reproductive technologies to treat infertility?
- Fertility drugs contain FSH and LH , which stimulate eggs to mature in the ovary
- Fertility treatments increase a woman’s chance of becoming pregnant, although the treatment may not always work
- On the other hand, because the treatment boosts the production of mature eggs, it increases the chance of twins or triplets
What happens in In Vitro Fertilisation(IVF) treatment?
- IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs
- The eggs are collected from the mother and fertilised by sperm from the father in the laboratory
- The fertilised eggs develop into embryos
- At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb)
The benefit of fertility treatment is it allows woman to have the chance to have a baby of her own, but what are the drawbacks?
- Is very emotionally and physically stressful
- Success rates are not high
- Can lead to multiple births which are a risk to both the babies and the mother.
What is the role of thyroxine in the body?
- Thyroxine is from the thyroid gland which stimulate the basic metabolic rate
- It plays an important role in growth and development
What is the role of adrenaline in the body?
- Adrenaline is produced by the adrenal glands in times of fear or stress
- It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for “flight or fight’
How are thyroxine levels controlled?
By negative feedback
