UNIT 14 [2NDPART] - 14.4 & onwards, HOMEOSTASIS Flashcards
desc: homeostasis
the maintenance of a
constant internal environment
insulin _____ blood glucose
concentration
insulin
DECREASES
blood glucose concentration
Homeostasis always tries to …
keep a variable in our body at a set point using negative feedback
meaning
If a variable changes from the set point it will be detected by a receptor, transmitted by nerves and an effector will be activated to return the variable to its set point
examples
insulin / glucagon for homeostasis of blood sugar levels,
ADH for homeostasis of blood water levels
homeostasis of body temperature
Heat losses must ______ heat gains to maintain a constant body temperature
EQUAL
Role of Insulin in Homeostasis
here, internal conditions within the body…
need to be kept within set limits in order to ensure that reactions in body cells can function and therefore the organism as a whole can live
body will not function properly otherwise
Insulin is secreted into the blood at times when blood glucose levels are high
e.g.
(most often) directly after a meal
kidneys can only cope with a certain level of glucose in the blood
so if the level gets too high, …
to avoid this…
then…
glucose gets excreted and is lost in the urine
To avoid this, insulin temporarily converts excess glucose into glycogen in the liver and muscles
glycogen is converted back to glucose several hours later when blood glucose levels have dipped due to respiration in all tissues
The Concept of Negative Feedback
occurs when…
negative feedback ==> conditions change from the ideal or set point and returns conditions to this set point
if the level of something rises, …
control systems are switched on to reduce it again
if the level of something falls, …
control systems are switched on to raise it again
Negative feedback mechanisms => usually a continuous cycle of bringing levels down and then bringing them back up so that overall, …
they stay within a narrow range of what is considered ‘normal’
Blood Glucose Control - levels are controlled by a negative feedback mechanism invol. the production of two hormones -
insulin and glucagon,
made in the pancreas
when is (soluble) insulin produced
when blood glucose rises and stimulates liver and muscle cells to convert excess glucose into glycogen to be stored
when is glucagon produced
glycogen = insoluble
when blood glucose falls & stimulates liver & muscle cells to convert stored glycogen into glucose to be released into the blood
adrenaline also speeds up conversion of glycogen to glucose
EXAM TIP;; difference btwn glucagon & glYcOgen
Glucagon is the hormone
Glycogen is the polysaccharide glucose is stored as
what is Type 1 Diabetes
a condition/disorder where the blood glucose levels are not able to be regulated
as the insulin-secreting cells in the pancreas are not able to produce insulin/pancreas fail to produce sufficient insulin
so blood glucose levels are often far too high
treated by
injecting insulin
extra insulin causes
the liver to convert glucose into glycogen, which reduces the blood glucose level
Symptoms of diabetes
extreme thirst, weakness or tiredness, blurred vision, weight loss and loss of consciousness in extreme cases
what is required of someone w/ T1D
monitor their blood glucose levels throughout the day
as their levels of physical activity and their diet affect the amount of insulin needed
what they can do
help to control their blood glucose level by being careful with their diet -
=> eating foods that will not cause large increases in blood glucose level,
& by exercising, which can lower blood glucose levels due to increased respiration in the muscles
;;; not in syllabus
TYPE 2: body cells no longer respond to insulin
treatment for type 2: carbohydrate-controlled diet & an exercise regime
Temperature Control, thermoregulation, The Skin;
=> human body maintains the temperature at which enzymes work best, around ____
around 37°C
if body temperature increases over 37, enzymes will …
denature and become less effective at catalysing reactions such as respiration
Regulation…
which contains…
- is controlled by the brain
- brain contains receptors sensitive to the temperature of the blood
the skin has…
sends NERVOUS IMPULSES…
skin also has temperature receptors and sends nervous impulses to the brain via sensory neurones
brain responds to this information by …
sending nerve impulses to effectors in the skin to maintain the temperature
within a narrow range of the optimum, 37°C
what does fatty tissue do
Fatty tissue under the dermis acts as a layer of insulation to prevent too much body heat being lost through the skin
hypothalamus…
- thermoregulatory centre in the hypothalamus senses the temperature of the blood flowing through it
- also receives information via sensory neurones from heat receptors in the skin
If the core body temperature starts to rise the hypothalamus triggers responses which increase heat losses
If the core body temperature starts to fall the hypothalamus triggers responses which either reduce heat losses OR generate more heat
SUMMARY ;; increase in body temperature
- thermoreceptors in the hypothalamus and skin detect change
=> increased sweating, vasodilation, hairs lie flat against skin
==> decrease in body temperature
decrease in body temp
- thermoreceptors in the hypothalamus and skin detect change
==> vasoconstriction, shivering, skin hairs erect
==> increase in body temp
Responses to changes in temperature:
- WHEN WE ARE HOT
- SWEAT is secreted by sweat glands.
cools skin by evaporation. heat energy from the body is lost as liquid water in sweat becomes water vapour (state change)
- WHEN WE ARE HOT ;;
- hairs lie flat against the skin, allowing air to freely circulate. this increases heat transfer to environment by radiation
- WHEN WE ARE COLD
- skeletal muscles contract rapidly and we SHIVER. these involuntary muscle contractions need energy from respiration and some of this is released as heat
- WHEN WE ARE COLD ;;
- erect HAIRS trap a layer of air around the skin which acts as an insulator, preventing heat loss by radiation
vasoconstriction
constrict = cold
blood flow in capillaries slows down because arterioles leading to the skin capillaries get narrower
- reduces the amount of heat lost from blood by radiation as less blood flows through the surface of the skin
vasodilation
when we are HOT
- blood flow in capillaries increases because blood vessels to the skin capillaries get wider
- cools the body as blood (which carries heat around the body) is flowing at a faster rate through the skin’s surface and so more heat is lost by radiation
tropism meaning
the growth response of an organism towards or away from a stimulus
- responses are usually much SLOWER than animals
what is gravitropism
a response in which parts of a plant grow towards or away from gravity
positive: towards roots
negative: towards shoots
what is phototropism
a response in which parts of a plant grow towards or away from the direction of the light source
pos: shoots
neg: roots
tropisms can either be positive or negative,
as in?
positive = towards stimulus
negative = away from stimulus
examples of the chemical control of plant growth
phototropism and gravitropism of a shoot
what is auxin?
a growth regulating hormone
- makes plant shoot cells elongate and inhibits elongation in roots
Explain the role of auxin in controlling shoot growth
auxin is made in the shoot tip [& MOVES AWAY FROM LIGHT]
auxin diffuses through the plant from the
shoot tip [diffuse AWAY FROM SHOOT & LIGHT; TOWARDS GRAVITY]
auxin is unequally distributed in response to light and gravity
auxin [LOOSENS CELL WALL &] stimulates cell elongation
- ensures shoots pos phototropic & roots pos gravitropic
opaque cap
no light goes through
responses shoots have
bc…
SHOOTS PPNG
shoots have a positive phototropic response and a negative gravitropic response
grow upwards to absorb sunlight
responses ROOTS have
bc…
ROOTS NPPG
negative phototropic response and a positive gravitropic response
- need to grow downwards into the soil, in order to anchor the plant and absorb water and minerals from the soil particles.
gravitropism -
where else is auxin produced
where does it sink
what happens to this place
auxin is also produced at ROOT tips
- has opposite effect on root cells, it inhibits cell elongation
- auxin sinks to the bottom side of roots
- inhibits cell elongation on the bottom side of the root, causing the root to grow down
in a test, state:
- direction of stimulus
- talk about where auxin diffuses to
- what effect does it have on cells? (elongation)
- what direction does the shoot grow
remember
auxin may be destroyed on the illuminated side, and the unilluminated side with more auxin elongates, causing the shoot to bend toward the light.
) Explain the advantage to the seedlings of this growth response.
/ plants / chloroplasts, get more light ;
more (light) energy, absorbed/ trapped/AW ;
more photosynthesis ;
more, growth
(auxins) made/produced, in (shoot), tip/ apex ;
pass /move/ diffuse/ spread (down the stem) ;
auxins collect in the side, in the dark / away from light ;
greater (cell) elongation on side in the dark ;
(auxins) made/produced, in (shoot), tip/ apex ;
pass /move/ diffuse/ spread (down the stem) ;
auxins collect in the side, in the dark / away from light ;
greater (cell) elongation on side in the dark ;
The response of the skin to cold weather is an involuntary action.
Explain how an involuntary action differs from a voluntary action. [3]
(involuntary responses are) automatic / does not involve thought
(higher centres of) brain not involved ;
faster/ immediate/rapid ;
response always the same
Describe how the nervous system coordinates the response of the skin to cold weather. [4]
cold is stimulus ;
temperature receptors (in skin) [detect change] ;
(electric) impulse [is sent] ;
travels through sensory neurone ;
to brain ;
relay / connector/ intermediate neurone ;
motor neurone ;
to effector
Explain how negative feedback is involved in the control of body temperature. [3]
change in temperature, is detected ;
to keep temperature constant or at optimum of 37 ;
opposite action by the body ;
return to normal temperature ;
which is homeostasis
hepatic portal vein is where?
LIVERHEPATICLIVERHEPATICLIVERHEPATIC
links liver to small intestine
Control of blood glucose by the liver is an example of homeostasis.
(i) Explain how the liver lowers blood glucose concentration when it is too high. [2]
(liver) responds to insulin (from pancreas) ;
increased respiration of glucose ;
glucose converted to glycogen ;
by enzymes
Name one other factor in the human body that is also controlled by homeostasis
temperature ;
water
Amino acids are processed by the liver.
Describe this process. [3]
deamination ;
(part of excess) amino acids converted to urea ;
(part of) amino acid converted to ammonia ;
ammonia converted to urea ;
ammonia is harmful
State one other function of the liver, besides homeostasis and processing amino acids.
bile production
State one reason why the concentration of glucose in the blood increases [1]
eaten/ absorbed, a (sugary / high carbohydrate) meal/AW ;
(secretion/effect, of) adrenaline ;
(secretion/effect, of) glucagon ;
dehydration/ loss of water ;
State one reason why the concentration of glucose in the blood decreases. [1]
used in respiration ;
(named) exercise/ physical activity ;
hungry / fasting/ starvation ;
(secretion/effect, of) insulin ;
Name two places in the body where glycogen is stored.
liver ;
muscle ;
kidney
testes
Explain how an increase in glucose concentration is controlled in the body [3]
pancreas detects increase in glucose concentration;
pancreas secretes /produces, insulin ;
transported in, blood/ plasma ;
liver/ muscle/ cells, convert glucose to glycogen ;
by enzymes ;
homeostasis
If the blood glucose concentration is very high there is a decrease in the water
potential of the blood. This may damage the red blood cells.
Explain how a decrease in water potential of the blood may damage red blood cells.
water, diffuses out of (red blood cells) ;
through, partially permeable membrane ;
by osmosis ;
down water potential gradient/ from high water potential to low water potential ;
(red cells) decrease in volume/ shrink / crenated
target organ releases glucose into the blood-stream as a result of the action of adrenaline?
liver
Explain how auxins control the growth response of the seedlings —
(auxins) made/produced, in (shoot), tip/ apex ;
pass /move/ diffuse/ spread (down the stem) ;
auxins collect in the side, in the dark / away from light ;
greater (cell) elongation on side in the dark ;
Adrenaline is often secreted during sporting competitions.
Outline how adrenaline affects the performance of a swimmer. [3]
heart rate / pulse increase ;
increase in breathing rate / depth ;
heighten alertness / faster reaction time / AW ;
vasodilation in muscle ;
Explain how adrenaline prepares the body for an extreme sport, such as making a
bungee jump. [5]
increase in, heart / pulse, rate ;
increase in, breathing rate / depth of breathing ;
more oxygen, taken in / absorbed ; linked to MP2
for (increase rate of) aerobic respiration ;
more energy released ;
lens less convex = further away
State how the ciliary muscles and suspensory ligaments act to change the shape
of the lens during the time marked E [MORE CONVEX] on Fig. 3.2.
ciliary muscles
suspensory ligaments
ciliary;;; CONTRACTS
suspensory;;; SLACKENS
closer up CCSS
Outline how humans are able to see in colour.
cones (in context of colour vision) ;
& two from
three different types ;
respond to, different wavelengths /red, green and blue ;
convert light into electrical impulses / signals ;
optic nerve ;
brain interprets impulses in terms of, colours /red, green and blue ;
Explain why glucose needs to be converted to glycogen for storage rather than
remaining dissolved in the blood.
glucose is soluble, glycogen is insoluble ;
glucose in blood would, lower water potential / AW e.g. (cause)
hyperglycemia ;
OR -
water leaves cells ;
by osmosis ;
Suggest why glucose is converted to glycogen rather than kept as glucose inside
the cells. [2]
this prevents a decrease in water potential ;
so reducing excess uptake of water ;
by osmosis ;
prevents cell bursting
State the effect that glucagon has on liver cells
stimulates liver cells
to break down glycogen and release glucose ;
Explain what is meant by the term involuntary action.
response / reaction , to stimulus ;
occurs without having to, think / use the brain / make decision ;
The arm shown in Fig. 5.1 moves in response to the detection of heat.
Explain how the parts of the reflex arc shown in Fig. 5.1 bring about this response [5]
receptor(s) detects heat / stimulus ;
(nervous / electrical) impulses ;
generated by (skin) receptor ;
travels to spinal cord along sensory neurone(s) (within spinal nerve) ;
relay neurone ;
motor neurone to effector / biceps / muscle ;
biceps contracts ;
advantages of simple reflexes
fast ;
automatic ;
protective
The organs of the human body are coordinated by the nervous system.
Outline one other way in which these organs are coordinated.
hormones ;
secreted into the blood / which travels in blood ;
stimulate target organs ;
identify
stimulus
receptor cells
effector
response
if someone has bright blue light shining into their eyes
stimulus: blue light
receptor cells: rods
effector: (circular) muscle in iris
response: pupil gets smaller
Describe how the nervous system coordinates the response shown [4]
(electrical) impulses ;
sent by retina ;
through, sensory neurone(s)
to, brain
(from the brain) along motor neurone
cones but no rods
;; no cones or rods
fovea
;; blind spot
Describe how rods and cones function. [4]
light absorbed (by a pigment) ;
rods detect low light (intensity) ;
do not detect colour
cones detect high light (intensity) ;
cones detect colour ;
any detail, e.g. three different types of cone ;
Name the type of control system used in homeostasis that returns the blood glucose
concentration to 80–90mg per 100cm3
negative feedback ;
In dangerous situations there is an increase in the secretion of adrenaline from the
adrenal glands.
Describe three ways in which this increase in adrenaline prepares the body for action.
heart beats faster ;
increased rate of breathing ;
dilate pupils ;
heightened sensitivity / increased mental
awareness
Explain why the control of the concentration of glucose in the blood is an example of negative feedback. [3]
homeostasis
glucose concentration is kept constant
any change (in concentration), is detected ;
it returns concentration to normal ;
