B3 Flashcards
Homeostasis
regulation (balance) of the internal conditions of a cell or organism to maintain optimum conditions for enzyme function and all cell functions in response to internal and external changes.
what does homeostasis control
blood glucose concentration
body temperature
water levels.
Receptor cells
these are specialised cells that detect a stimulus (changes in the environment).
The human nervous system order
stimulus 🡪 receptor 🡪 coordinator 🡪 effector 🡪 response
Sensory neurone
these carry impulses from the receptors to the central nervous system (CNS).
Relay neurones
these connect the sensory neurones to the motor neurones in the CNS.
Motor neurones
these carry impulses from the CNS to an effector.
brain
e brain controls complex behaviour. It is made of billions of interconnected neurones and has different regions that carry out different functions.
three main structure in the brain
cerebral cortex – is the outer ‘wrinkled’ layer of the brain. It is responsible for intelligence, language, memory and consciousness.
cerebellum – is located at the lower part of the back of the brain and is responsible for voluntary coordination of the muscles.
medulla – is located in the lower part of the brain stem. It is responsible for involuntary coordination such as breathing, swallowing and heart rate.
cornea
Transparent layer at the front of the eye; it refracts light into the eye.
iris
The coloured part of the eye; contains muscles that control the amount of light entering the eye.
pupil
The hole in the middle of the iris that lets light in. Its diameter is controlled by the iris.
lens
A transparent, biconvex structure in the eye that refracts light onto the retina.
retina
Thin layer of tissue at the back of the eye that contains receptor cells for light and colour.
sclera
Tough white supporting wall of the eye.
ciliary muscles
Muscles that are connected to the lens by the suspensory ligaments; they change the shape of the lens.
suspensory ligaments
These connect the lens to the ciliary muscles.
optic nerve
Carries impulses from the retina to the brain.
What is hyperopia? How can it be corrected?
Long-sightedness, it can be corrected with convex lenses
What is myopia? How can it be corrected?
Short-sightedness, it can be corrected with concave lenses
endocrine system
The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream.
pituitary gland
The pituitary gland in the brain is often called a ‘master gland’ as it produces and secretes many hormones into the blood.
The hormones are released in response to changes in body conditions.
thyroid
The thyroid produces and secretes the hormone thyroxine. Thyroxine regulates the metabolic rate, this is the rate at which energy is released in the body. Thyroxine also regulates breathing, heart rate and body temperature.
Negative feedback:
occurs when there is a change in the body (i.e. blood glucose increases)
the nervous system detects the change
this stimulates an opposite hormonal response
this reverses the effect back to homeostasis.
Positive Feedback: (less common)
a change starts
the nervous system detects the change
then stimulates more hormones to be released to accelerate the change.
ovaries
he ovaries produce and secrete the hormones oestrogen and progesterone. Oestrogen controls the development of secondary sexual characteristics in females and inhibits FSH and stimulates the pituitary gland to produce LH.
Progesterone maintains the lining of the uterus during the menstrual cycle.
testes
The testes produce and secrete the hormone testosterone. It controls the development of secondary sexual characteristics in
males.
FSH
pituitary glands
Stimulates egg ripening and oestrogen production (in ovaries
Oestrogen
Ovaries
Lining of the womb to develop. Stimulates pituitary gland to make LH
LH
Pituitary Gland
Stimulates egg release and progesterone production in the ovaries
Progesterone
Ovaries
Maintains the lining of the womb
Vasoconstriction
If the body temperature is too low, blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver).
Vasodilation
If the body temperature is too high, blood vessels dilate (vasodilation) and sweat is produced from the sweat glands. Both these mechanisms cause a transfer of energy from the skin to the environment.
Blood glucose concentration
Blood glucose concentration TOO HIGH
The PANCREAS releases insulin
GLUCOSE is moved from the blood into the cells
LIVER and MUSCLE cells convert excess GLUCOSE into GLYCOGEN for storage
Type 1 diabetes
A disorder in which the pancreas fails to produce enough insulin.
The lack of insulin causes uncontrolled high blood glucose levels.
Type 1 is normally treated with insulin injections.
Type 2 diabetes
A disorder where the body cells no longer respond to insulin produced by the pancreas.
Obesity is a risk factor for type 2 diabetes.
Type 2 is normally treated by controlling the carbohydrate in the diet and by exercise.
Hypertonic
more concentrated solution than in the cells
Isotonic
same concentration as the solution in the cell
Hypotonic
more dilute than the solution in the cells
high diet in protein
Diet high in proteins
Digestive system
proteins 🡪 amino acids
Liver
amino acids 🡪 ammonia
(deaminated)
ammonia 🡪 urea
Kidneys
Urea is filtered from the blood and excreted from the body in urine
What does deaminated mean?
An amino group is removed from an amino acid.
