Biology: Mod 8 - Non-Infectious Diseases and Disorders

what is homeostasis (def)

maintenance by an organism of a relatively constant internal state, regardless of external environmental changes

what is the reason for homeostasis and what factors can affect homeostasis?

• Necessary to maintain metabolic processes for survival 

• Factors: enzyme activity, temperature, pH, concentration of substrates, osmotic pressure

in mammals what two systems are involved in homeostasis?

endocrine and nervous system

what does “relatively constant internal state” actually mean in homeostasis?

• a narrow range of fluctuation within the internal environment

• If fluctuation is larger, mechanism comes into operation to return body to normal range

• 

what does tolerance limits mean in homeostasis?

variables in the internal environment that are maintained within a narrow range (temp, glucose concentration)

what are set points in homeostasis?

• the ideal/normal value of each of these variables (temp, glucose )

why is the negative feedback system “negative”?

Feedback = message from receptors to control centre, response from control centre to change original stimulus

• Is negative = response counteracts the stimulus

what are the 2 stages of the negative feedback system?

1. detecting change

2. counteracting change

explain the negative feedback system in steps

explain the negative feedback loop for glucose regulation

explain the negative feedback loop for body temperature

what are the responses the body does if there is high blood sugar?

secretes insulin =

• promotes glucose uptake (by liver, muscles, fat cells)

• reduces glucose production (released from liver)

• converts glucose into glycogen (in liver muscles)

what are the bodys responses for low blood sugar?

secretes glucagon:

• stimulates breakdown of glycogen into glucose

• promotes glucose synthesis from non-carbohydrate sources

what are the body’s responses for high internal temperature?

1. vasodilation = blood closer to skin = heat evaporates into air

2. sweat = evaporation = heat loss

3. cell reduces metabolic rate = less heat produced

what are the body’s responses for low internal temperature?

1. blood vessels constrict = reduced heat loss

2. muscles contract rapidly = shivering = heat

3. release of thyroid stimulating hormone = increase in thyroxin = increase in cell metabolism = heat

4. erect hair = traps warm air around body

what happens if blood is brought to the surface of the body?

• Blood is mostly water → carries a lot of heat → if brought to surface of body → heat will dissipate into environment

what is the role of the nervous system in the homestasis?

•  relays information in body thru nervous impulses → along the nerves

what ist he role of the endocrine system in homeostasis?

• relays information by hormones (chemical messengers) → in the blood

what are receptors?

both systems use it to detect stimuli (a change from the tolerance limits)

• Contain sensory cells and have different forms based on their related stimuli

• Complex receptors are concentrated in an area to form sense organs

what is interoceptors?

receptors in the body that detect internal stimuli linked to homeostasis

what are the 3 types of interoceptors and their role in homeostasis?

Thermoreceptors 🌡	Detects change in temperature In the skin: nerve endings sensitive to heat/cold → send info to brain regarding external temp In hypothalamus: detect temp of blood as it flows thru brain
Chemoreceptors 🧪	Detect concentration of certain chemicals (CO2, O2), pH levels Located in certain blood vessels
Osmoreceptors 💦	Detects change in osmotic pressure, located in hypothalamus

what are thermoreceptors?

Detects change in temperature

• In the skin: nerve endings sensitive to heat/cold → send info to brain regarding external temp

• In hypothalamus: detect temp of blood as it flows thru brain

what are chemoreceptors?

Detect concentration of certain chemicals (CO2, O2), pH levels Located in certain blood vessels

what are osmoreceptors?

Detects change in osmotic pressure, located in hypothalamus

what are the two types of nervous system?

Peripheral Nervous System

Central Nervous System

what is in the peripheral nervous system?

Other nerves not part of CNS Carries information to and from CNS by nerves through electrochemical impulses

what is the central nervous system?

Has the brain, spinal cord + nerves

• The control centre for heart rate, temperature, blood pressure, [O] and [CO₂] in blood

Hypothalamus (in brain) 

• links nervous system and endocrine system

• Hormone secretion

Spinal Cord

• Pathway for nerve impulses

• Coordinates reflex actions

what is a neuron?

cell body (w. nucleus), dendrites (receive messages), single axon (messages away)

• To transfer a nervous impulse from the axon of a neuron to the other neurons dendrites: crosses a synapse (small gap)

• Starts the electrical impulse in next neuron

what are the 3 types of neurons?

sensory, relay, motor

what is a sensory neuron?

1. from sensory receptors → CNS (long dendron, short axon)

what is a relay neuron

1. transmit information within the CNS (short dendrites)

what is a motor neuron?

from CNS to effectors (muscles/glands) (short dendrites, long axon)

how do the neurons work together from a stimulus?

what does the endocrine system consist of?

• Glands → stimulated by messengers in neurons/receptors/hormones → secrete hormones

  • Influence enzyme activity/concentration

what is the pituary gland?

Master gland → releases hormones to regulate other glands

• Anterior section is controlled by hypothalamus

• Posterior section controlled by nerve impulses

what is the thyroid gland?

TSH (thyroid stimulating hormone) released from pituitary gland → thyroxine produced in thyroid gland → metabolic rate adjusted

what is the adrenal gland?

Hydrocortisone: regulates stress, converts carbs, fats, protein → energy

what does the pancreas do?

Insulin and Glucagon produced

what are endotherms?

Endotherm (“warm blooded”)

Adjust internal metabolism to maintain body temperature Heat in endotherms are generated from metabolic processes  Usually terrestrial organisms Adapt to assist in thermoregulation

what are ecotherms?

Ecotherm (“cold blooded”)

Adjust body temperature based on the environment Usually aquatic organisms

what are 3 behavioural adaptations endotherms do to regulate homeostasis and an example of an animal?

Endotherms change their body orientation, seek shade, move into burrows/water = change S.A of body in contact with sunlight	Fairy Penguins:  Move into the water to cool down Huddle in the cold - ↓ S.A exposed to cold
Nocturnal Activity for organisms that live in areas of high daytime temperatures	Bilby shelters in burrow during day, nocturnal
Migrate to warmer waters in colder temperatures	Humpback Whales

what are 2 structural adaptations endotherms do to regulate homeostasis and an example of an animal?

Insulation (skin, fur, hair, feathers, blubber) = trap layer of air next to skin	Fairy Penguins feathers = insulation = less heat loss In cool weather: feathers life from skin = increased air layer = insulation
Animals in colder climates have a lower SA: V  In hotter climates have larger SA:V	Biliby (hot) = large ears = highly vascularised = heat from blood evaporates = heat loss

what are 3 physiological adaptations endotherms do to regulate homeostasis and an example of an animal?

Hibernation: heat rate + oxygen consumption ↓, but body temp = 30℃ Torpor (short-termed hibernation): body temp lowers significantly, metabolism, heart rate, respiratory rate ↓	pygmy possum
Concurrent exchange of blood: warm blood in arteries heat the cooler blood in veins coming from the cold extremities	Platypus, Australian fur seal
Organisms that fluctuate b/w maintaining constant body temp Can fluctuate with environment	Roost: temp ↓, rises again before end of roost Lowering body temp at night = prevents heat loss E.g. Laughing Kookaburra

how does water loss occur in plants?

• from transpiration = evaporation of water from stomata of leaves

what is the benefit of stomata and transpiration?

• Helps lift water and dissolved ions from roots

• Forms evaporative cooling that regulates temperature in plants

• Stomata open for gas exchange for photosynthesis

what are xerophytes?

plants that live in arid conditions and have adapted to achieve a water balance to survive

e.g cactus

list the 5 ways plants adapt to minimise water loss and maintain water balance

1. reduce internal temperature

2. reduce exposure of transpiring plant structures to sunlight

3. regulation of opening and closing of stomata

4. water storage

5. woody fruits

what adaptations do plants do to reduce their internal temperature?

Plants use less water for evaporative cooling while maintaining effective temperature for metabolism

• Leaves coated in shiny/waxy OR thick/leathery cuticle = epidermal cells are waterproof = prevents water loss by evaporation 

• Leaf has white hairs to reflect sunlight =  ↓ temp on surface of leaf = ↓ evaporation

what do plants do to reduce exposure of transpiring plant structures to sunlight?

• Orientation of leaves changed to ensure lower exposure of stomata to direct sunlight

• Reduced S.A of organs that have high proportions of stomata:

  • Smaller leaves: photosynthetic function taken over by cladodes (stems) and phyllodes (leaf stalks) = have fewer stomata (sunken) + hair = less water lost 

  • Shedding leaves

• No transpiring plant organs (leaves, flowers, petals etc): have extra adaptations to prevent overheating, ensure photosynthesis and pollination

what do plants do to regulate opening and closing of stoamta?

• Stomata only opens during cooler parts of the day - temp is lower = evaporation  ↓

• Create smaller “microclimate” in the air surrounding each leaf:

  • Hairy, rolled leaves + sunken stomata trap water → keeps air around plant humid (prevents moist air being moved by wind) = barrier to evaporation

  • Can keep stomata open for longer 

CAM (Crassulacean Acid Metabolism) Photosynthesis

what is CAM photosynthesis?

CAM (Crassulacean Acid Metabolism) Photosynthesis

Stomata opened at night → convert CO₂ to acid → stored in vacuole → day: stomata closes → acid converted back to CO₂ → light dependent stage of photosynthesis occurs

E.g. pigface

what do plants do for water storage?

Fleshy stems, leaves that swell up and retain moisture when available → survive by using moisture in dry periods (e.g. succulents)

what do plants do with their fruits to maintain water balance?

Woody fruits produced (rather than fleshy) to  ↓ water lost when fruit falls off