Homeostasis and Response Flashcards
Central Nervous System
The part of the nervous system made up of the brain and the spinal cord.
What are neurones?
Specialised cells that carry electrical impulses.
What are the five parts of control systems in the nervous system?
- Stimulus - environmental change
- Receptors - detect the change
- Coordinator - organises the response
- Effectors - create a response
- Response - caused by an effector
Synapse
A gap between two neurons.
Describe the parts of a reflex arc.
- Stimulus
- Receptor
- Sensory neurone - impulses travel along these to the spinal cord
- Relay neurone - located within the spinal cord, and connects sensory and motor neurones
- Motor neurone - connects the relay neurone to the effector
- Effector
- Response
What is a reflex arc?
The pathway of information from a sensory neuron through an inter neuron to a motor neuron.
Hormones
Chemicals produced by glands in the body
Describe the characteristics of a nerve response.
Fast, short lived, electrical response transmitted through neurones
Gland
An organ or tissue that makes a substance for release
What happens if blood glucose is too high?
Insulin is released, causing glucose to move from the blood into the liver cells.
What is Type 1 diabetes and how can it be controlled and monitored?
It occurs when the pancreas doesn’t produce enough insulin, meaning the body cells can’t take up glucose.
It can be controlled by monitoring the diet and injecting appropriate amounts of insulin. Exercise is also important as it uses glucose to create energy through respiration.
What is diabetes?
A disease in which the body is unable to regulate blood sugar.
What is type 2 diabetes and how is it controlled?
It is when the person’s body cells no longer respond to insulin produced by the pancreas.
It can be controlled by a low carbohydrate diet (carbohydrate is digested into glucose which raises the overall blood glucose level) and exercise.
Puberty definition and secondary sexual characteristics.
Changes that occur due to reproductive organs.
Boys - testosterone is released by the testes and stimulates sperm production
Girls - oestrogen is released by the ovaries and causes eggs to be released
Negative feedback
A mechanism where changes to conditions cause an action to reverse the change, keeping conditions stable.
Pituitary gland
An endocrine gland that is located just below the centre of the brain and releases a number of important hormones
Describe thyroxine.
Hormone produced by the thyroid gland which stimulates the basal metabolic rate.
Describe adrenaline.
Produced by the adrenal glands at times of fear or stress and creates a ‘flight or fight’ response.
Explain how negative feedback works in blood glucose control.
If the blood glucose levels are too high, insulin is secreted by the pancreas
Liver converts glucose to glycogen for storage and the blood glucose decreases
If the blood glucose is too low glucagon is secreted from the pancreas instead of insulin
The liver converts glycogen back to glucose and the blood glucose increases
Glucagon
A hormone produced by the pancreas that promotes the breakdown of glycogen into glucose in the liver
Glycogen
Animals store glucose as glycogen in their liver and muscle tissues
Which hormones are controlled by negative feedback?
Thyroxine and ADH
Why is glucose important in blood sugar regulation?
Excess glucose is stored in the liver.
Oestrogen
A female sex hormone produced in the ovaries, which is responsible for puberty in girls and the regulation of the menstrual cycle
Describe how different hormones affect the menstrual cycle.
- FSH causes eggs to mature in the ovary
- Oestrogen repairs and thickens the uterus lining
- LH triggers ovulation of the matured egg
- Progesterone maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy
Menstrual cycle
Recurring series of events in the human female reproductive system
What is Follicle Stimulating Hormone?
It stimulates oestrogen production and the growth of follicles in the ovary.
It is secreted by the pituitary gland.
What is Luteinising Hormone?
It is secreted by the pituitary gland and stimulates ovulation.
What are examples of hormonal methods of contraception?
- Oral contraceptive uses oestrogen or progesterone to prevent FSH being released so eggs can’t mature
- Injections, implants or patches release progesterone which inhibit maturation and release of eggs for many months or years
What are examples of non-hormonal contraceptives?
Intrauterine devices (IUDs) prevent the implantation of an embryo
Spermicidal agents kill sperm
Abstaining from sexual intercourse
Surgical methods such as sterilisation, which is irreversible
What are examples of fertility drugs and what are the risks of using them?
LH and FSH which stimulate eggs to mature in the ovaries.
RISK: Undergoing fertility treatments may result in multiple pregnancies, which can lead to medical and health complications.
What is IVF and the process of it?
It is used to help infertile couples have a baby.
Eggs are collected from the mother and fertilised by the father’s sperm in a laboratory.
Fertilised eggs develop into embryos.
One or two embryos are implanted into the woman’s uterus, to increase the chance of a successful pregnancy. There is also an increased chance of twins.
What are the advantages of infertility treatments?
Safe - been used since 1978
Helps infertile couples
Screening for genetic diseases can be included
What are the disadvantages of infertility treatments?
Emotionally and physically stressful
Multiple birth complaints
Low success rates
Ethical concerns
How how have recent scientific developments in technology helped IVF treatments?
Microscope developments have allowed more accurate techniques.
Why can’t everyone have IVF on the NHS?
There are many guidelines to see who can qualify for the treatment and it is a very expensive procedure.
What are two examples of effectors?
Glands and muscles.
Why do reflex arc signals not go immediately to the brain?
Because it would take longer to react if they did.
Describe the structure and function of the nerves in the nervous system.
- The central nervous system is made from the brain and spinal cord
- The peripheral nervous system is a network of nerves that cover the rest of the body
- Receptor cells in sense organs start electrical signals which travel along sensory neurones to the central nervous system
- Relay neurones carry electrical signals around the central nervous system
- Motor neurones carry electrical signals away from the central nervous system to effectors which are muscles or glands
- Gaps between neurones are called synapses
- All neurones have extended projects called axons along which electrical signals travel
- Axons are insulated by myelin sheaths to speed up the electrical signals
Describe what happens at a synapse.
- Where two neurones meet there is a small gap, a synapse.
- An electrical impulse travels along the first axon.
- This triggers the nerve-ending of a neurone to release chemical messengers called neurotransmitters into the synapse.
- These chemicals diffuse across the synapse (the gap) and bind with receptor molecules on the membrane of the second neurone.
- The receptor molecules on the second neurone bind only to the specific neurotransmitters released from the first neurone.
- This stimulates the second neurone to transmit the electrical impulse.
Similarities and differences between the role of hormones in the endocrine system and nerves in the nervous system.
Both hormones and electrical impulses in nerves send signals.
——————————————————
Electrical signals in nerves move quickly.
Hormones are released by glands.
Hormones move in the blood.
Hormones act upon a target organ.
Hormones control the menstrual cycle, homeostasis and puberty (three marks).
Electrical signals in nerves allow us to see, hear, feel, smell and taste.
How are nerve cells adapted for their function?
They have a long axon which carries the electrical signal.
The axon is insulated by the myelin sheath.
Nerve cells have tiny branches called dendrones.
These branch further into dendrites.
Dendrites receive signals from other nerve cells.
