Section 2j Excretion Flashcards
What are the three main organs of excretion?
Lungs - O2 & CO2
Kidneys - Urea, H2O, excess minerals (sodium)
Skin - H2O
How do kidneys carry out excretion and osmoregulation?
Excretion:
The kidney filters urea from the blood stream and combine it with water to to make urine which moves to the bladder.
Osmoregulation:
The kidneys react to a hormone called ADH made by the pituitary gland. When ADH is released more water is reabsorbed back into the blood from the collecting duct.
Describe the structure of the urinary system.
2 Kidneys 2 Ureters Bladder Sphincter Urethra
Describe structure of a nephron.
Afferent arteriole Glomerulus Efferent arteriole Bowman's capsule Proximal convoluted tubule Loop of Henlé Distal convoluted tubule Collecting duct
Describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate.
Unfiltered blood enters the glomerulus through the afferent arteriole. The glomerulus is made of multiple capillaries, which are very thin and have very high pressures. The smaller substances such as water, glucose and other nutrients/salts are pushed out of the pores of the glomerulus.
Bigger cells, proteins and urea cannot go through the pores because they are too large.
EXRTA:
The capsule then leads to the PCT; here, glucose is selectively reabsorbed into blood via active transport.
It then heads to the loop of Henlé where water is reabsorbed into the blood via osmosis.
Next, in the DCT, salts such as sodium is reabsorbed into the blood via active transport as well.
Excess nutrients such as water, urea and salts form urine and heads to the collecting duct. Collecting ducts from other nephrons come together to form the ureter, and this leads the urine to the bladder.
Where does selective reabsorption occur?
Glucose is selectively reabsorbed in the proximal convoluted tubule.
What does urine contain?
Water, urea and salts.
Stimuli - Receptor cells - Sensory neurone - spine - Relay neurone - Motor neurone - Effector
Homeostasis - maintenance of internal content of the body.
Nervous systems - Immediate response to stimuli
Endocrine system - Slow response to stimuli
Both systems respond to stimuli (changes in the environment).
Both systems have a detector (detects the stimuli).
Both systems have an effector (carries out response to correct stimuli effect).
Nervous system sends ELECTRICAL impulses
Endocrine sends HORMONES to target cells
Nervous system response is immediate
Endocrine response is slow
Central nervous system consists of the brain and spinal cord, which are connected to sense organs via nerves.
When you touch a hot object (the stimuli), receptor cells in your skin send electrical impulses along the sensory neurone which head to the spinal cord. The impulses first pass through a synapse, then head through a relay neurone in the spinal cord. They pass a synapse again and go through a motor neurone. This neurone takes the impulses to an effector, and carries out a response to correct the stimuli effect.
sclera - outer protective layer of eye
chloroid - contains many pigments that absorb light and prevent the light from being reflected around the inside of the eye.
fovea - sharpens images
optic nerve - sensory neurones that send electrical impulses to the brain.
pupil - light enters through the pupil
cornea - refracts light into eye
lens - allows focusing by changing shape
vitreous humor - maintains the shape of the eye
aqueous humor - maintains pressure in the eye and nourishes cornea
retina - contains cones and rods that help transduce light energy into electrical impulses
ciliary muscles - changes shape of the lens by pulling suspensory ligaments or relaxing them
iris - controls amount of light entering eye by adjusting size of pupil
Light is refracted into the eye via the cornea and hits photoreceptors that form the retina.
In dark light:
stimulus - retina - radial muscles contract, circular muscles relax - pupil diameter opens
In bright light:
stimulus - retina - radial muscles relax, circular muscles contract - pupil diameter closes
Focusing distant object:
ciliary muscles relax - suspensory ligaments contract - lens pulled thin
Focusing close object:
ciliary muscles contract - suspensory ligaments relax - lens gets fat
Progesterone - maintains lining of uterus and causes menstruation
Oestrogen - stimulates lining of uterus (indirectly) and causes ovulation
Sexual reproduction - fusion of two gametes to produce offspring genetically different to parent
Asexual reproduction - produce offspring genetically identical to the parent. no fusion of gametes
Fertilisation - Two gametes fuse together to form a zygote. The zygote divides by mitosis and forms an embryo.
Male reproductive system:
Testes - produce sperm
Vas deference - carries sperm to penis
Seminal vesicle - produces a liquid that mixes with sperm cells to become semen
Urethra - carries sperm/urine out of the penis
Female reproductive system:
Ovaries - produces egg
Oviducts/fallopian tube - carries eggs to the uterus
Uterus - site of fertilisation/developing of the egg on the placenta
Cervix - entrance to uterus
Testosterone: Causes spermatogenesis Causes voice to deepen Causes testes to drop and penis to enlarge Causes body hair to grow Causes muscles to grow
Oestrogen: Triggers ovulation Causes hips to widen Causes breasts to grow Causes pubic hair to grow Matures vagina
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