P1 P2 ONLY EXCRETION 2i & 2j excretion + coordination and response Flashcards
why do humans need to excrete?
many of the necessary metabolic reactions that take place produce waste products
what is excretion?
it is the removal of the waste substances of metabolic reactions, toxic minerals and substances in excess of requirements
what are some of the metabolic waste produced in the human body?
- carbon dioxide and water from aerobic respiration in cells
- urea, produced by the breakdown of excess proteins in the liver
- other substances in excess such as medical drugs, and dietary minerals
what are the dangers of waste products?
if they are left in the body
- have toxic effects, like carbon dioxide which dissolves in water easily to from an acidic solution, lowers pH in cells, reduces activity of enzymes
- osmotic effect, concentrated body fluids can cause water to move out of cells, changing their water potential
- using up needed storage
what is the difference between excretion and egestion?
- egestion is the expulsion of food that has not been absorbed by the body, faeces etc
- excretion is the removal of metabolic waste products.
what are the organs of excretion?
- kidneys
- lungs
- skin
- liver
what does skin excrete?
water and mineral ions
what do the kidneys excrete?
urea, water and mineral ions
what do lungs excrete?
carbon dioxide and water
what does the liver excrete?
doesn’t excrete, is produces urea from the breakdown of amino acids
what are the main structures of the urinary system?
- kidney
- bladder
- ureter
- urethra
what do the kidneys do in the urinary system?
two bean shaped organs that filter the blood
what does the ureter do in the urinary system?
tube connecting the kidney to the bladder
what does the bladder do in the urinary system?
organ that stores urine (excess water, salts and urea) as it is produced by the kidney
what does the urethra do in the urinary system?
tube that connects the bladder to the exterior, where urine is released
what are the two main functions of the urinary system?
- to filter waste products from the blood and expel it from the body as urine
- to control the water levels of the body (osmoregulation)
what are the kidneys connected to?
- the renal artery which comes from the aorta and delivers oxygenated blood to the kidney
- and the renal vein which delivers the deoxygenated blood from the kidney to the vena cava
what are the three regions of the kidney and where are they?
- cortex, the outermost region
- medulla, the inner section of the kidney
- renal pelvis, the tube linking the kidney to the ureter
where are the nephrons in the kidney?
start at the cortex and loop down to the medulla and back up to the cortex
what is the nephron made up of?
- bowmans capsule
- proximal convoluted tubule
- loop of henlé
- collecting duct
- glomerulus
what happens in ultrafiltration?
blood is filtered
- first it travels through the glomerulus
- the narrow capillaries increases pressure of travelling blood so it causes smaller molecules to be forced out of the blood and into the bowmans capsule
- this is called the filtrate
what are the substances in the filtrate?
- glucose, water, urea and salt get pushed out of the blood
where does the reabsorption of glucose occur?
- first tube, or proximal convoluted
where does the reabsorption of water occur?
loop of henle and collecting duct
where does the reabsorption of salts occur?
loop of henle
where does the reabsorption of urea occur?
it isn’t reabsorbed
why can glucose only be reabsorbed at the first convoluted tubule?
only place that facilitates active transport of glucose
how does the glucose get reabsorbed?
active transport
how is the first tubule adapted for the reabsorption of glucose?
has many mitochondria to provide energy for the active transport of glucose molecules
how are water and salts reabsorbed?
as the filtrate drips through the loop of henle the necessary salts are reabsorbed back into the blood by diffusion
- as salts are reabsorbed water follows by osmosis
- water is also reabsorbed from the collection duct in different amounts dependent on how much the body needs
what happens to the remaining fluid in the collecting duct?
will form urine which is concentrated urea
what is homeostasis?
the maintenance of a constant internal environment
what is osmoregulation?
process of maintaining water and salt concentrations across membranes within the body
what is the importance of osmoregulation?
vital to prevent harmful changes occurring to cells as a result of osmosis
what happens if the body has too much water?
results in cells swelling as water moves into them, leads to cells bursting
what happens if the body has too little water?
cells lose water by osmosis the has a dehydrating effect and can lead to cell death
what are the three types of neurones?
sensory, motor and relay
- most common is the motor
- sensory brings info into the brain
- relay, takes info and passes it on
what is a synapse?
where dendrites of two neurones meet, to make a connection, a junction known as a synapse is formed
- they don’t actually touch
what happens at the synapse?
- electrical impluse travels through the presynaptic cell
- which trigger the vesicles move to the end of the pre synaptic membrane
- when they get there by diffusion they connect to the membrane and burst
- releases neurotransmitter chemical
- neurotransmitter locks on to the receptor protein, which is the the post synaptic cell
- this triggers a new electrical impulse in the protein which goes down the post synaptic cell
what directions can the impulses travel in a synapse?
only one and it will end if it is weak
what happens to the impulses when you take drugs?
bind to neurotransmitter receptors triggering impulses in different regions of the brain
- they also depress synaptic releases
what’s vasodilation of skin capillaries?
increase heat loss to cool the body
- so the body supplies the capillaries with greater volume of blood, which loses heat to the environment via radiation
- the muscles relax causing
arterioles to dilate allowing more blood flow
what are arterioles?
have muscles in their walls that can relax or contract to allow more or less blood flow through them
what are other responses when the body is too hot?
sweating
- secreated by sweat glands
- cools the skin by evaporation
flattening of hairs
- the hair erector muscles in the skin relax
- stops them formed an insulating layer and allows for heat loss through radiation
what is vasoconstriction of skin capillaries?
decrease heat loss to supply capillaries with a smaller volume of blood, minimising heat loss
- the muscles in the arteriole walls contract causing arterioles near the skin to constrict and allowing less blood flow
- this just reduces heat loss from the blood as it flows through the skin
what are other things that happen when body temp it too low?
shivering
- reflex action
- muscles contract in a rapid and regular manner
- metabolic reaction required generate sufficient heat to warm the blood and raise the core body temp
erection of hairs
- muscles contract
- forms an insulating layer stops heat from being lost by radiation
what is a reflex arc?
it is the pathway of a reflex response
what is an example of a reflex response?
pain-withdrawal reflex that occurs when someone steps on a pin
what is the response of the reflex arc when someone steps on a pin?
- the pin is detached by a (pain) receptor in the skin
- a sensory neurone sends electrical impulses to the spinal cord
- the impulse is passed to a relay neurone in the spinal cord
- a relay neurone synapses with a motor neurone
- a motor neurone carries an impulse to a muscle in the leg
- the muscle will contract and pull away from the object
how fast does the response of the reflex arc take?
fraction of a second, they do not involve a conscious part of the brain
what is the stimulus in the example?
the pin, so the thing that causes the reaction
- other example is heat or fired
what is the coordinator in the example?
spinal cord
what is the receptor in the example?
the thing that receives the pain so the foot
what is the response in the example?
when the muscle contracts and pulls it away from the stimulus
what is the effector in the example?
the muscle in the leg, thing that does an effect
what does a sensory neurone look like?
it has a round receptor cell at the top
had myelin sheath and axon
also has a cell body on the side
what does a relay neurone look like?
it has a dendrites around the cell body which looks like a tree
and an axon but no myelin sheath
what does a motor neurone look like?
it has a small cell body with some dendrites sticking out
and myelin sheath with axons
what is the function of the cornea?
transparent lens that refracts light as it enters the eye
what is the function of the iris?
controls how much light enters the pupil
what is the function of the lens?
transparent disc that can change the shape to focus light onto the retina
what is the function of the optic nerve?
sensory neurone that carries the impulses between the eye and the brain
what is the function of the pupil?
hole that allows light to enter the eye
what is the vitreous humour?
jelly- like liquid filling the eyeball
what is the aqueous humour?
the watery liquid between the cornea and the lens
what is the sclera?
the strong outer wall of the eyeball that helps to keep the eye in shape and provides a place of attachment for the muscles that move the eye
what are the suspensory ligaments?
ligaments that connect the ciliary muscle to the lens
what is the ciliary muscle?
a ring of muscle that contracts and relaxes to change the shape of the lens
what happens to the eye when an object is close?
- ciliary muscles contract
- causing suspensory ligaments to loosen
- stopping the suspensory ligaments from pulling on the lens, allowing it to become fatter
- light is refracted more
what happens to the eye when an object is far?
- ciliary muscles relax
- causing the suspensory ligaments to tighten
- then they pull on the lens causing it to become thinner
- light is refracted less
what happens to the eye in dim light?
the pupil dilates in order to allow as much light in as possible to improve vision
what happens to the eye in bright light?
pupil constricts in order to prevent too much light from entering the eye
why does the pupil change in response to change in light intensity?
the pupil reflex is a reflex action carried out to protect the retina from damage
where are hormones produced?
endocrine glands
where is insulin made and what does it do?
pancreas, regulates blood glucose levels
where is adrenaline made?
adrenal glands
where is testosterone made?
testes
where is oestrogen and progesterone made?
ovaries
what is thyroxine?
hormone that controls metabolic rates and affects growth
what does adrenaline do?
readies the body for a fight or flight response, it then increases heart rate and breathing rate
what is the effect of insulin?
causes excess glucose to be taken p by the muscles and liver, converts it into glycogen
what does the central nervous system consist of?
brain, spinal cord, and is linked to sense organs by nerves
difference of the endocrine system compared to nervous system?
method of transmission is bloodstream
speed of transmission is slower
length of effect is longer
sends chemical hormone messages not electrical impulses
what are auxins?
plant growth regulators to coordinate and control direction growth
where are auxins produced?
tips of shoots and roots, and they diffuse around the plant
how is the distribution of auxins affected?
in the shoots is affected by light and gravity
in the roots by gravity alone
what does auxins promote in shoots?
cell elongation, more auxin more cell growth
what does auxins promote in roots?
inhibits cell elongation, more auxin less growth
what is uneven growth in plants caused by?
uneven distribution of auxin
