Homeostasis Flashcards
Paper 2 - B5
What is homeostasis?
Regulation of internal conditions of a cell or organisms to maintain optimum conditions for function in response to internal and external changes
Which molecules in the body are affected by homeostasis and need optimal conditions?
Enzymes
State 3 things that are controlled (kept constant) by homeostasis
Body temperature, blood glucose concentration, water levels
Homeostasis relies on automatic control systems. Which two systems are involve in coordinating these responses?
Nervous system, endocrine system
What do receptors do?
Detect stimuli (changes in the environment)
Name 3 coordination centres involved in different aspects of homeostasis
Brain, spinal cord, pancreas
Name the two types of effector which bring about responses in the body
Muscles or glands
What is the function (job) of the nervous system?
To enable humans to react to their surroundings and coordinate their behaviour
What type of signal travels along a nerve?
An electrical impulse
Which two organs make up the central nervous system (CNS)?
Brain and spinal cord
Put the following words in the correct order to show the stages in a reflex arc: effector, receptor, motor neurone, response, sensory neurone, coordinator (CNS), stimulus
Stimulus –> receptor –> sensory neurone –> coordinator –> motor neurone –> effector –> response
Where are relay neurones found?
Inside the central nervous system (brain and spinal cord)
What is a synapse?
A gap between two neurones
What happens at a synapse between two neurones?
A chemical is released so that a new impulse begins in the next neurone
What is a reflex action? Why are they important?
An automatic and rapid response to a stimulus. They are important for survival and protection from harm. They do not involve the conscious part of the brain
(Triple only) What is the brain made of?
Billions of interconnecting neurones
(Triple only) What is the function of Cerebral cortex in the brain?
It is responsible for conscious thought,
movement and processing sensory
information
(Triple only) What is the function of the cerebellum in the brain?
Balance and coordination of movement
(Triple only) What is the function of the medulla in the brain?
Unconscious processes such as control of heart rate and breathing rate
(Triple only) Why is it difficult to investigate brain function and treat brain damage/disease?
The brain is a very complex and delicate organ and difficult to map. Different areas of the brain often work together. Technologies to analyse brain activity are relatively new (and involve being inside a scanner).
(Triple only) Give three techniques used by scientists to map the regions of the brain to particular functions
Studying patients with brain damage; MRI scans; electrically stimulating different parts of the brain
(Triple only) What is ‘accommodation’ in the eye?
How the lens changes shape to focus on near and distant objects
(Triple only) Name the structures involved in accommodation in the eye
Lens, suspensory ligaments, ciliary muscles
(Triple only) How does the eye adapt to dim light and which structures are involved?
The pupil dilates to let in more light. This involves circular muscles in the iris relaxing and radial muscles contracting
(Triple only) What two things are the receptors in the eye sensitive to?
Light intensity and colour
(Triple only) What is the function of the retina in the eye?
Contains light sensitive receptors
(Triple only) How are impulses from the eye transmitted to the brain?
Via the optic nerve
(Triple only) Name the tough white outer coating of the eye
The sclera
(Triple only) What is the role of the cornea?
To refract light
(Triple only) What is the function of the lens?
To focus light to a point on the retina
(Triple only) In accommodation in the eye, when focusing on a near object, what do the ciliary muscles, suspensory ligaments and lens do?
Ciliary muscles contract, suspensory ligaments loosen, lens is thicker and refracts light rays more strongly
(Triple only) In accommodation in the eye, when focusing on a distant object, what do the ciliary muscles, suspensory ligaments and lens do?
Ciliary muscles relax, suspensory ligaments are pulled tight, lens is pulled thin and refracts light rays less
(Triple only) What is the scientific name for short-sightedness?
Myopia
(Triple only) What is the scientific name for long-sightedness?
Hyperopia
(Triple only) What type of lens is required to treat hyperopia?
Convex
(Triple only) What type of lens is required to treat myopia?
Concave
(Triple only) In which eye defect is light focused to a point in front of the retina rather than directly onto it?
Myopia
(Triple only) Give three alternatives to spectacle lenses to treat eye defects
Hard & soft contact lenses, laser surgery to change shape of cornea, replacement lens
(Triple only) Which part of the brain monitors and controls body temperature?
Thermoregulatory centre
(Triple only) Name two places in the body where temperature receptors are found and which temperature they detect
On skin to detect surface temperature; In thermoregulatory centre of brain to detect blood temperature
(Triple only) Which response to temperature involves blood vessels to the skin dilating, and does this occur when temperatures are too high or too low?
Vasodilation; when too high
(Triple only) What is vasoconstriction and when does it occur?
When blood vessels to the skin constrict, when body temperature is too low
(Triple only) Give the two body responses to an increase in body temperature
Sweating and vasodilation
(Triple only) Give the two body response to a decrease in body temperature
Shivering and vasoconstriction
(Triple only) How does shivering warm the body?
Rapid muscle contractions increase rate of respiration and release heat energy
Name the system in the body that controls hormonal communication
The endocrine system
What name is given to the organs of the endocrine system?
Glands
How do hormones travel around the body?
In the bloodstream
What name is used to refer to any part of the body that a hormone acts on
A target organ
Give two differences between a nervous and hormonal response
Hormonal is slower but acts for longer
Which gland is called the ‘master gland’ because it secretes hormones that act on other glands?
Pituitary gland
Where is the pituitary gland located?
At the base of the brain
Where is the pancreas located?
In the middle of the left side of the body, below the stomach, above intestines
Where is the thyroid gland located?
In the neck
Where are the adrenal glands located?
On top of the kidneys
Which organ monitors and controls blood glucose concentration?
Pancreas
Which hormone is released when blood glucose levels are too high?
Insulin
Which hormone is released when blood glucose levels are too low?
Glucagon
In control of blood glucose levels, what chemical is excess glucose converted into, and which two organs store this?
Glycogen in liver and muscle cells
Name the disease in which the pancreas fails to produce enough insulin
Type 1 diabetes
Name the disease in which the body cells no longer respond to insulin
Type 2 diabetes
Which type of diabetes is treated using insulin injections?
Type 1 diabetes
What is the usual treatment for type 2 diabetes?
A carbohydrate controlled diet and an exercise regime
What is the main risk factor for type 2 diabetes?
Obesity
What is Negative Feedback?
A process whereby a change in a factor brings about an action which reverses the change
(Triple only) Why is it important to maintain levels of water and salt in the body?
Osmotic effects on cells meaning they don’t function normally
(Triple only) Give three ways in which water is lost from the body
Urine, sweat, exhalation
(Triple only) Give two ways in which water loss occurs which the body has no control over
Sweat (via skin) and exhalation (via lungs). Kidneys control how much water lost via urine
(Triple only) Give two other components of sweat in addition to water
Ions and urea
(Triple only) Name the process by which excess amino acids are dealt with, the organ involved, and the product made
Deamination in liver, product is ammonia (immediately converted to urea)
(Triple only) What is the ammonia from deamination immediately converted into?
Urea
(Triple only) Which organ maintains water balance in the body?
Kidney
(Triple only) Name 3 substance that are selectively reabsorbed back into the blood by the kidneys
Glucose, some ions and water
(Triple only) Name the process by which the kidneys remove substances from the blood, and the process by which some of them are then returned to the blood
Filtration, selective reabsorption
(Triple only) Name the hormone involved in controlling the amount of water reabsorbed by the kidneys
ADH
(Triple only) What effect does ADH have on the kidneys?
Increases the permeability of the kidney tubules
(Triple only) Which organ releases ADH and which organ does it act on?
Released by pituitary gland, acts on kidneys
(Triple only) Under what conditions is ADH released?
When blood is too concentrated
(Triple only) Name two ways in which kidney disease can be treated
Organ transplant or dialysis
(Triple only) What is dialysis?
Where blood is removed from the body to be artificially filtered via a machine
(Triple only) Why does dialysis fluid contain glucose?
To prevent glucose leaving the blood via diffusion, and to ensure that water doesn’t move into the blood from the dialysis fluid by osmosis
What overall effect do hormones have in reproduction?
Cause the development of secondary sexual characteristics
Name the male reproductive hormone
Testosterone
Name the female reproductive hormone
Oestrogen
What is ovulation?
When an egg is released from the ovary in females (roughly once every 28 days)
What is the main role of testosterone in males?
To stimulate sperm production
Name the four hormones involved in control of the menstrual cycle
Oestrogen, progesterone, follicle stimulating
hormone (FSH), luteinising hormone (LH)
What is the role of follicle stimulating hormone (FSH) in the menstrual cycle?
Causes maturation (ripening) of an egg in the ovary
What is the role of luteinising hormone (LH) in the menstrual cycle?
Stimulates release of the egg
What is the role of oestrogen and progesterone in the menstrual cycle?
Build up and maintain the uterus lining
Where are oestrogen and progesterone produced?
In the ovaries
Where are FSH and LH hormones produced?
Pituitary gland
Name 4 hormonal methods of contraception
The pill, implant, injection, skin patch
Name 2 barrier methods of contraception
condom (male and female), diaphragm
How do barrier methods of contraception work?
Non-hormonal, prevent sperm reaching the egg
How do hormonal methods of contraception work?
Prevent egg from maturing in the ovary (e.g. the pill inhibits FSH production)
How do intrauterine devices prevent pregnancy?
Prevent implantation of an embryo in the uterus (may also release a hormone)
Why are surgical methods not commonly used as a method of contraception in younger people?
They are permanent
Which two hormones are in fertility drugs?
FSH and LH
What is In vitro fertilisation (IVF)?
Eggs are removed from the woman and fertilised by sperm outside the body with the embryo then implanted into the uterus to help a woman become pregnant
Give 3 problems with IVF treatment
Emotionally/physically stressful; low success rate; can lead to risky multiple births
What is the role of thyroxine in the body?
Stimulates basal metabolic rate
What effect does adrenaline have on the body?
Increases heart rate and boosts delivery of oxygen and glucose to the brain and muscles
How is thyroxine controlled by negative feedback?
When thyroxine levels are low, TSH is released by the pituitary gland and stimulate thyroid gland to produce more thyroxine.
(Triple only) Name the plant growth response to light
Phototropism
(Triple only) Name the plant growth response to gravity
Gravitropism or geotropism
(Triple only) Name the hormone involved in phototropism in plants and state it’s effect on cells
Auxin, causes cell elongation (on the shady side of the plant)
(Triple only) Name the plant hormone involved in initiating seed germination
Gibberellins
(Triple only) What is the role of ethene in plants?
Controls cell division and ripening of fruits
(Triple only) Give 3 ways in which auxins can be used in agriculture or horticulture
Weedkillers; rooting powders; promoting growth in tissue culture
(Triple only) How is ethene used in the food industry?
To control ripening of fruit during storage and transport
(Triple only) Give 3 ways in which gibberellins can be used in agriculture and horticulture
End seed dormancy; promote flowering; increase fruit size
