B3 - organism level systems (from PMT) Flashcards
what is the difference between the central nervous system and the peripheral nervous system?
the central nervous system is the brain and the spinal cord, the peripheral nervous system is every other part of the nervous system
define a stimulus
a change in the environment
what type of neurone connects a receptor to the CNS
a sensory neurone
what is an effector
a part of the body that brings about the response to a stimulus like a muscle or a gland
what type of neurone connects the CNS to an effector?
a motor neurone
describe the reflex arc
-stimulus detected by receptor
-impulse passed along sensory neurone to CNS
-impulse passed along motor neurone to effector
-effector brings about the response
what is the cornea and what is its function?
the transparent layer in front of the eye that protects the eye from damage
what is the function of the lens?
the lens focuses the light rays onto the retina
what is the retina and what is its function?
the retina is the back part of the eye and it converts visual stimuli into electrical impulses
where is the cerebrum located and what is its function?
-it is located at the front of the brain
-it controls conscious functions, memory and language
where is the cerebellum located and what is its function?
-it is located at the back bottom of the brain
-it controls muscular movement and balance
where is the medulla located and what is its function?
-it is located in the brainstem in the middle at the bottom
-it controls unconscious functions like heart rate and breathing
what is the function of the hypothalamus?
it acts as the regulatory centre and controls things like body temperature, water content and salt balance
why is it difficult to treat brain disorders?
-the brain and spinal cord are very difficult to access
-tissues in the CNS cannot regenerate
-drugs cannot penetrate the blood-brain barrier
define target cells
target cells are cells with the specific receptor for a hormone that produce an effect when the hormone binds
what does the hormone thyroxine control in the body?
metabolic rate
describe thyroxine as a negative feedback system
-when the level of thyroxine decreases the pituitary gland produces thyroid stimulating hormone, which causes the thyroid gland to produce more thyroxine
-when the level of thyroxine increases, the pituitary gland produces less TSH
what is the function of oestrogen?
causes the uterus lining to thicken
what hormone does oestrogen inhibit?
FSH
what is the function of progesterone?
maintains the womb lining
what hormone does progesterone inhibit?
FSH
what is the function of FSH?
stimulates the follicle to mature + release oestrogen
what is the function of LH?
causes the release of an egg from a follicle - ovulation
how do oestrogen pills work to prevent pregnancy?
oestrogen pills inhibit FSH which stops the egg from maturing
how do progesterone pills work to prevent pregnancy?
cause a sticky mucus to form at the cervix which prevents the sperm from fertilising the egg
describe how IVF is carried out
-mother is given FSH
-sperm from the father and eggs from the mother are collected
-the egg is fertilised in a laboratory and allowed to develop into an embryo
-the embryo is then put into the mother’s uterus
what hormone is given in female fertility drugs?
FSH
what does auxin trigger?
growth of the main stem of the plant (+ inhibits the growth of side shoots)
what do gibberellins do?
-promote seed germination
-increase the length between stem nodes
-delays leaf shedding
what does ethene cause when it is applied to plants?
fruit ripening
what are parthenocarpic fruit?
seedless fruit
define homeostasis
the maintenance of a stable internal environment in the body despite fluctuations in internal and external conditions
state 3 conditions which need to be controlled within the body
-temperature
-water levels
-blood glucose concentration
why does the temperature need to be controlled?
to provide a suitable environment for enzymes so that they can work fastest at their optimum temperature
describe the process of vasodilation
-the body detects a wise in temperature
-blood vessels supplying the capillaries at the skin surface dilate
-more blood flows closer to the skin where more heat energy can be released
state 2 effects caused by insulin secretion
-more glucose is taken up by cells
-glucose is converted to glycogen for storage
what does the secretion of glucagon cause?
glucagon secretions cause glycogen to be broken down into glucose to raise the blood glucose concentration
what is the main difference between type 1 and type 2 diabetes?
type 1 - the body doesn’t produce enough insulin
type 2 - the body no longer responds to insulin
what happens if an animal cell is placed in a solution of lower water potential?
the cell will crenate
what happens if an animal cell is placed in a solution of higher water potential?
water will move into the cell and it will burst (lyse)
what is the function of the kidneys?
-maintaining the balance of water and other substances in the body through urine production
-filtering out the waste products, such as water, ions and urea (from amino acids) from the body
-selectively reabsorbing useful substances such as glucose, ions and water into the body
describe the general structure of a kidney
-contains a cortex and medulla
-renal artery carries blood to the kidney
-renal vein carries blood away from the kidney
-each kidney contains many nephrons
-ureter carries fluid from the kidneys to the bladder
what does ADH do?
-when ADH is secreted into the bloodstream it increases the permeability of the kidney tubules to water
-this increases the reabsorption of water, where more water leaves the tubules to move into the bloodstream
describe the negative feedback loop when dehydration is detected
-thirst signals activated
-more ADH released (water retained by kidneys)
describe the negative feedback loop when overhydration is detected
-less ADH is released
-dilute urine is produced
-salts are retained
