Chapter 9 Flashcards
cells in the human body require an internal temp of roughly _____, which is normal body temperature.
37°C
- small variations from this temp can be damaging or deadly.
-A sustained body temp below 35 °C or greater than 37.8 °C can cause some bodily processes to malfunction.
human body has many mechanisms that regulate its internal temperature. Give 2 examples
1) When we get too hot, we sweat.
2) When our body temp drops, we shiver to make thermal energy
Most animals have _______________or _________________ adaptations that allow them to maintain a suitable temperature.
physiological, behavioural
there r many animals native to the Sahara Desert that thrive in the conditions using special adaptations. Elaborate
- Ex, the fennec fox (Vulpes zerda)
- Its enormous ears serve 2 important functions that enable it to live in such a hostile habitat
1) large ears enhance its hearing. –> allows it to hear predators coming from far away, as well as hear prey, even when underground
2) act as “radiators.”–> rmr the greater the SA,
the faster & more easily the temp can be regulated downward. –> The radiator ears give it a large surface area to dissipate thermal energy faster.
–> Maintaining an optimal internal temp helps
the fox thrive in temps below 0°C to above 50°C.
homeostasis is
- the physiological state of the body in which the internal physical & chem conditions r maintained within an acceptable or tolerable range that is suitable for essential biological processes
- purpose is to maintain internal physical and chemical conditions needed for the cells to function properly
- is not a “steady state” or a constant condition, but a dynamic process that is continuously adjusted in response to changes in the internal or external environment –> Ex, the body must maintain
its optimal range of conditions during exercise, fatigue, & extremes of temp.
The body has several key parts, fluids, and conditions that must be monitored and adjusted for the body’s homeostasis to be maintained. List some
- internal temperature
- hormone levels
- the pressure, pH, flow, and concentration of glucose and other solutes in the blood.
- some factors, like blood pH & internal temp, the tolerable range is fairly narrow.
- In others, such as blood flow, glucose levels, & hormone levels, the tolerable range is broader & there
can be considerable variation without harmful effects.
. When discussing homeostasis, what does the internal environment refer to? Intracellular fluid (the fluid inside of the cells) or extracellular fluid (fluid outside of the cells)?
Extracellular fluid (fluid outside of the cells)
internal environment is
the extracellular fluid, which consists of the fluid that
surrounds the cells and tissues in the body (interstitial fluid) & the plasma portion of the blood
- Every cell in the body= surrounded by the extracellular fluid
- avge adult has 15 L of extracellular fluid, which= 20% of body mass
- volume, temp, & chem composition of our internal environment can change quickly. –> Rigorous physical activity, other extreme conditions, and infection can tip the balance maintained in the extracellular fluid.
- These changes can have a dramatic (often bad) effect on cellular functions, so the body uses many systems to maintain and regulate its internal conditions
interstitial fluid is
the fluid that surrounds the body cells
purpose of extracellular fluid
- acts as a medium for delivering energy, transporting chemicals, and eliminating waste
- The regulated flow of energy, chemicals, & waste into & out of the extracellular fluid allows the cells, and thus systems, to function properly.
What role does each organ system play in homeostasis?
- Nervous System: Receives sensory data from environment, which informs the body of external conditions, & transmits signals to regulate homeostasis.
- Excretory System: Eliminates waste and maintains a clean internal environment.
- Endocrine System: Regulates hormone levels critical for life processes.
- Circulatory System: Distributes hormones, chemicals, and thermal energy throughout the body.
- Immune System: Protects against and combats infections.
- Integumentary System (Skin): Helps maintain constant body temp by interacting with the external environment.
The liver, an organ in the digestive system, has several roles in maintaining homeostasis.
- Regulates amino acid levels, by breaking down any amino acids that are not used
- Detoxifies harmful chemicals.
- Produces essential blood proteins.
All of the organ systems are coordinated to carry out the tasks necessary for the survival of the organism. No matter how simple or complex the animal, these functions include:
- taking in nutrients & other required chemicals (like 02) from the environment, processing & distributing them throughout the body, & disposing of the waste
- making proteins, fats, carbohydrates, & other
essential molecules for cell function & structure - sensing & responding to changes in the external environment, like temp, physical sensations, & pH
-protecting the body from injury & from infection by viruses, bacteria, & other disease-causing agents
- reproducing, protecting, & feeding offspring
- Together these tasks maintain homeostasis . –> Their functions & activities make up most of an animal’s actions during its life, cuz maintaining an internal dynamic equilibrium is the only way that life can continue
Many organs & organ systems coordinate their activities to maintain homeostasis; however, the ____________ & _____________systems are the most
important systems.
nervous, endocrine
- 02 & C02 conc = regulated by the nervous
system,
- blood glucose= mainly regulated by the endocrine system
- blood pH & internal temp r regulated by both systems.
- These are ex of the many homeostatic mechanisms that are responsible for maintaining homeostasis
homeostatic mechanism is
a system that monitors internal & external conditions & changes bodily functions to maintain homeostasis
- To understand how homeostatic mechanisms work, consider the regulation of body temp.
- When the body’s internal temp is too high, we sweat; evaporation of sweat from our skin= endothermic process, so the body has a net loss of thermal energy absorbed by the water during the change of state.
- When cold, we shiver; these tiny muscle contractions generate thermal energy & raise the internal temp.
- Even the sensations of hunger & thirst r mechanisms that trigger behavioural responses to ensure the adequate nutrition & hydration of an animal.
- Since homeostatic mechanisms respond to internal & external conditions, they r described as detection-correction or feedback systems
The detection-correction or feedback systems that the body uses to maintain homeostasis r constantly detecting internal & external conditions. What happens next?
- These homeostatic mechanisms then evaluate the conditions to determine whether or not they represent any deviations from the norm.
- If conditions r outside of the optimal functioning
range, the mechanisms take corrective action to bring the body back into balance.
The primary mechanism of homeostasis is __________________, which is
negative feedback
- is the response of a system that acts to maintain equilibrium by compensating for any changes made to
the system
- a stimulus resulting from a change in the external or internal environment triggers a response that compensates for the change.
Homeostatic mechanisms include three elements: List them
a sensor, an integrator, and an effector
- The sensor and integrator are usually part of
the nervous or endocrine system, whereas the effector may include parts of any tissues & organs.
The sensor is
the element of a feedback system that detects changes in the environment
- consists of tissues or organs that detect any change or stimulus in external or internal factors, such as the pH, temp, or conc of molecules (ex, hormone or glucose molecules)
The integrator is
the element of a feedback system that compares existing conditions with ideal conditions
- Once the sensor gathers the information, it is transmitted to the integrator
- The integrator compares the environmental conditions with the optimal functioning conditions= set points
A set point is
the optimal value for a given variable of a system
- the set point represents a range of values within which a condition controlled by the mechanism is to be maintained.
The effector is
the element (or elements) of a feedback system that acts to return the system to its optimal state
- If the environmental condition is outside the set point, the integrator activates the effector, which is the system that returns the measured condition to the desired set point. –> This action is= the response.
- To bring internal conditions back into balance, negative feedback mechanisms use antagonistic effectors. –> The “antagonistic” in their name means that they act to make the opposite effect of the change recorded by the sensor.
The Thermostat as a Negative Feedback Mechanism
- A thermostat maintains a constant temp using a sensor to measure the current temp.
- It compares the measured temp to a user-defined set point.
- A sensor inside the thermostat measures the temp
- A circuit (integrator) in the thermostat compares the measured temp to the set point programmed by the user.
- If the temp increases or decreases by any amount, the integrator circuit activates an electrical effector (either a furnace or an air conditioner), which returns the temp to the set point.
- When the temp falls, the furnace is activated and warmer air is added to the home until the temp rises to the set point.
- When the temp rises, the air conditioner is activated & colder air is added to the room until the temp falls to the set point.
Mammals and birds also have a homeostatic mechanism that maintains body temp. Elaborate
- Mammals and birds maintain body temp within a narrow range (set point). –> In humans, the set point is around 35–37.8 °C, centered on 37 °C.
- The integrator= located in a brain centre called the hypothalamus
- The hypothalamus acts as the body’s thermostat, specifically the preoptic region of the anterior hypothalamus. –> receive info from thermoreceptors in various locations, including the skin, the spinal cord, & the hypothalamus itself.
- If the temp deviates from the set point, the hypothalamus activates a set of physiological & behavioural responses to re-establish the normal body temp
- The particular set of effectors that is activated depends on whether our body temp is above or below the set point
Effectors activated if body temp drops below the set point
the hypothalamus activates effectors that induce vasoconstriction in the skin.
–> As blood flow through the skin is reduced, less thermal energy is lost to the environment, which causes our body temp to increase.
- Additional effectors may induce homeostatic behaviour, such as shivering, which generates body heat.
- Signals from hypothalamus make us aware of our lowered body temp, which may cause us to put on warmer clothes or move to a warmer place.
Effectors activated if body temp is above the set point
- hypothalamus triggers effectors that induce vasodilation in the skin, which increases blood flow to skin & loss of thermal energy to the environment.
- Signals from the hypothalamus make us aware of overheating, and we may take off warm clothing or
move to a cooler area. - Other effectors cause the body to sweat, which causes loss of thermal energy when the sweat evaporates.
Does the set point of body temp ever change?
Yes, there r times when the ideal tempe set point changes & the feedback mechanisms work to readjust body temp to the new set point.
–> ex, if u have an infection caused by a virus or bacteria, the homeostatic effectors increase
your temp, causing a fever. –> This increase helps the body fight off the infection.
- Once the infection is cleared, the set point is readjusted to its normal level.
All mammals use ___________ homeostatic mechanisms to maintain their body temp set point
similar
Birds & dogs _______ to release thermal energy from their body. Many terrestrial vertebrates use _______ to cool off.
pant, water
Mammals and birds are able to regulate their internal temp within a narrow range, but other orgamisms can thrive within a much broader range
- Reptiles rely on behavioral adjustments–> Basking in sunlight to absorb heat & moving to cooler areas to avoid overheating.
- Large fish (e.g., tuna, sharks) generate heat through muscle contractions to maintain a warmer body temp.
- Insects warm flight muscles by basking or contracting them (similar to shivering).
- Honeybees maintain hive temp in winter by forming masses & contracting flight muscles.
- plants have thermal energy control mechanisms, often toaid in their development and to attract pollinators. Ex, the lotus plant minimizes
transpiration to stay cool & breaks down carbs to increase thermal energy
Another type of feedback mechanism is ___________________, which is
positive feedback
- the response of a system that acts to increase the effect of any changes made to the system
- Positive feedback mechanisms usually (with few exceptions) don’t result in homeostasis, since they cause the system to become unstable.
- They almost always operate when a continuous increase in some internal variable is required.
–> Ex, when an animal is attacked, body releases
adrenaline & hormones to blood to prime the muscles & organ systems for “fight or flight” reactions. –> release of these chemicals stimulates further release,
in a positive feedback cycle, making the animal even more fit to survive the attack
- Positive feedback mechanisms often operate within a larger negative feedback mechanism, which ultimately works over the long term to bring the body back into balance.
More examples of positive feedback occur during reproduction and child care.
- During child birth, uterine contractions stimulate oxytocin release from the pituitary gland.–> Oxytocin intensifies contractions, creating a cycle of stronger contractions & more oxytocin release.–> This cycle continues until the baby is delivered, after which contractions & oxytocin release stop.
- During child rearing, mammalian young suckle milk from the mother.–> sensation of suckling stimulates glands in the mother to produce milk. –> this milk production leads to more suckling from the young, again causing further milk production in a positive feedback cycle. When the baby is satiated, and ceases to suckle, the milk production is triggered to stop.
thermoregulation is
AKA temperature regulation
- the process of regulating internal temp by negative feedback mechanisms
- Temp receptors= thermo-receptors, detect any deviations in the external & internal temps from an
internal set point & then trigger behavioural & physiological responses that act to maintain the internal temp at the set point
- responses include adjustments in the rate of exothermic reactions in the body (such as metabolism) & adjustments in the rate of thermal energy exchange through the surface of the body.
Are the mechanisms of thermal energy exchange universal for all organisms?
Yes,
- almost all thermal energy exchange occurs at the surface where the body comes in contact with the external environment.
- Like any physical body, animals absorb thermal E if cooler than environment, & release thermal E if warmer than environment.
thermal E exchange occurs through one of 4 mechanisms. List them
conduction, convection, radiation, and evaporation.
- All animals exchange thermal E with their environment through these 4 mechanisms, which usually act simultaneously
Conduction is
the flow of thermal E between molecules that are in direct contact.
–> Animals lose thermal E when they come in contact with a colder body & gain thermal E when they come in contact with a warmer body
Convection is
the transfer of thermal E within a fluid (liquid or gas)
( Warm blood flows from the body’s core to the skin’s surface, where it loses heat to cooler surroundings via convection with air or water. CHATGPT)
Radiation is
the transfer of thermal E in the form of electromagnetic radiation.
- All objects, regardless of temp, radiate thermal E, & this radiation increases with the temp of the object
- Animals r constantly losing thermal E to the environment through radiation
- they also gain thermal E through radiation, usually by absorbing it from the Sun
Evaporation
The transfer of thermal E can be aided by evaporation. –> Ex, sweat.
- Water on the surface of the skin evaporates, absorbing thermal E from the skin & causing it to cool.
Mechanisms of Thermal Energy Exchange: A runner
- Conduction: Heat transfers to cooler air or the ground via direct contact.
- Convection: Rising warm air near the skin is replaced by cooler air, enhancing heat loss.
- Evaporation: Sweat evaporates, cooling the skin and aiding heat transfer.
- Radiation: The body emits infrared radiation while absorbing solar radiation.
- To maintain a stable body temp, the amount of thermal E leaving the body must = the total of the
amount made by the body & the amount absorbed from the environment.
All animals can be categorized into two groups based on the stability of their body temp: List them
- Homeotherms
- Poikilotherms
- have diff strategies aimed at regulating their body temp, & they have diff responses to changes in external temp
A homeotherm is
an animal that maintains a stable body temp regardless of the temp of the external environment
- Birds & mammals r homeotherms–> maintain a body temp that is often above the ambient environmental temperature.
A poikilotherm is
an animal whose body temp varies with, & often matches, the temp of the external environment
- Fish, amphibians, reptiles, & most invertebrates= poikilotherms
- poikilotherms still have some degree of control over their body temp
An endotherm is
an animal that maintains its body temp by internal mechanisms
- Internal physiological mechanisms that create thermal E to regulate body temp r referred to as endothermy
An ectotherm is
an animal that maintains its body temp by absorbing thermal E from the environment
- Behavioural mechanisms that involve using external sources of E r considered ectothermy
Which are more successful at maintaining body temp? Endotherms or ectotherms
Endotherms= more successful at maintaining a stable body temp, but they aren’t necessarily more successful animals.