Bio unit 4

Homeostasis

• State of the body where internal physical and chemical conditions are regulated/ kept within a range that is suitable for life processes

• It is not a constant condition

• Continuously adjusted in response to changes in the internal or external environment

Internal Environment

the fluid that surrounds the cells and tissues in the body and the plasma

portion of the blood

Interstitial Fluid

the fluid that surrounds the body cells

Homeostatic Mechanism

a system that monitors internal and external conditions and changes bodily functions to maintain homeostasis

What key parts, fluids, and conditions in the body that must be monitored and adjusted?

• Internal temperature,

• hormone levels,

• blood pressure,

• blood pH,

• blood flow,

• concentration of glucose and other solutes in the blood.

What are the Human Body’s Ideal Conditions

• 37° C

• 0.1% blood sugar

• blood pH 7.35

What does extracellular fluid act as?

a medium for delivering energy, transporting chemicals, and eliminating waste

what does Homeostasis focus on and depend on?

• Focus on the fluid outside of a cell

• Depend on multiple body systems

What causes Volume, temperature, and chemical composition of internal environment to change quickly?

• Due to things like: exercise, extreme conditions, infection

what are the Organ Systems Involved in Homeostasis

• Nervous system

• Endocrine system

• Muscular system

• Integumentary system

• Excretory system

• Reproductive System

About the nervous system (what it does, main organs)

Receives sensory data from the environment which informs the body of

external conditions. and Transmits signals throughout the body to regulate homeostasis.

Main Organs:

• Brain

• Spinal Cord

• Peripheral Nerves

• Sensory Organs

About the Endocrine System (what it does, and main organs)

Regulates the levels of various hormones that are essential to life processes.

Main Organs:

• Pituitary Gland

• Thyroid

• Adrenal Glands

• Pancreas

• etc…

About the Excretory System (what it does, and main organs)

Works to rid the body of waste and maintain a clean internal environment.

Main Organs:

• Kidneys

• Bladder

• Ureter

• Urethra

About the Muscular System (what it does, and main organs)

Gives the body structure, protects organs, allows for locomotion

Main organs:

• Skeletal muscle

• Cardiac muscle

• Smooth muscle

About the Integumentary System (what it does, and main organs)

Important for maintaining a constant body temperature

Main Organs:

• Skin

• Sweat Glands

• Hair

• Nails

About the Reproductive System (what it does, and main organs)

Allows for sexual reproduction of organisms

Main Organs:

Female

• Ovaries

• Oviducts

• Uterus

• Vagina

• Mammary Glands

Male

• Testes

• Sperm Ducts

• Accessory Glands

• Penis

What are some Homeostatic Mechanisms?

• When internal temperature is too high, we sweat

• When internal temperature is too low, we shiver

• Hunger and thirst are mechanisms that ensure adequate nutrition and hydration

Negative Feedback

The response of a system that acts to maintain equilibrium by compensating for any change made to the system

Sensor

• the element of a feedback system that detects changes in the environment

• consists of tissues or organs

• (detects pH, temp, concentration of molecules)

Integrator

• the element of a feedback system that compares existing conditions with ideal conditions

• gets information from sensor

Set Point

the optimal value for a given system / The range of values within which a condition controlled by the mechanism is to be maintained.

Effector

• the element (or elements) of a feedback system that acts to return the system to its optimal state

• activated if the environmental conditions do not match set points.

Positive Feedback

the response of a system that acts to increase the effect of any changes made to the system

Why Do We Need “Feedback Mechanisms”?

Because the body is constantly monitoring internal and external conditions and checking if they are different from the normal/optimal environment. If they are homeostatic mechanisms bring the body back to homeostasis

3 Components to Homeostasis

1. Sensor – sensors in organs, detect changes in the environment and signal integrator when out of balance

2. Integrator – compares existing conditions to ideal conditions (set points)- relays info to effector

3. Effector – restores normal balance

what is the primary mechanism of homeostasis

• Negative feedback

• aka a systems response to compensate for any changes made

• restores conditions to original state

• Prevents changes from continuing in the same direction

what is special about mammals and birds body temperature ?

they must maintain body temperature within a relatively narrow range around a set point

Where is the integrator located in mammals and birds?

• in the hypothalamus

• Portions of the hypothalamus act like a thermostat for the body

• neurons in the hypothalamus get info from thermometers and compare temperature to set point of 37C

Where does the activation of effectors depend on in mammals and birds? (too low/high)

• weather our body temp is above or below the set point

• Too low = vasoconstriction is enacted and shivering starts

• Too high = vasodilation is enacted and sweating commences

what do Positive Feedback Systems do?

• Increase the change in the environmental condition

• Do not result in homeostasis

• Cause the system to become unstable

• Almost always operate when a continuous increase in some internal variable is required

EX: Fight or Flight (The release of adrenaline further stimulates the release of more adrenaline.) Childbirth (Oxytocin stimulates and intensifies contractions as well as the release of more oxytocin.) Lactation (Sensation of suckling stimulates lactation which leads to more sucking from the young)

Thermoregulation

the regulation of internal temperature by negative mechanisms

Homeotherm

an animal that maintains a stable body temperature regardless of the temperature of the external environment

Poikilotherm

an animal whose body temperature follows the temperature of the external environment

Endotherm

an animal that maintains its body temperature by internal mechanisms

Ectotherm

an animal that maintains its body temperature by absorbing thermal energy from the environment

Thermal Acclimatization

process by which an animal gradually adjusts to temperature changes in its environment

Torpor

a short-term state of reduced metabolic rate and body temperature that reduces the demand for energy during the night or day

Hibernation

a state of greatly reduced metabolic rate and activity that enables an animal to survive the winter by reducing the demand for energy when food is unavailable

Estivation

a state of torpor that enables an animal to survive the summer by reducing the demand for energy

what do Thermometers do?

• they detect any deviations in the external and internal temperatures from an internal set point and then trigger behavioral and physiological responses that act to maintain the internal set point.

• Can adjust metabolism and rate of thermal energy exchange

  through the surface of the body.

where does almost all thermal energy exchange occur?

at the surface where the body comes into contact with the external environment

what are the Mechanisms of Thermal Energy Exchange

1. Conduction: Flow of thermal energy b/w molecules in direct contact.

2. Convection: Transfer of thermal energy within a fluid (liquid or gas).

3. Radiation: Transfer of thermal energy by electromagnetic radiation. (Infared)

4. Evaporation; absorption of thermal energy from skin by water as it evaporates

(All animals exchange thermal energy through these four mechanisms (usually simultaneously))

Mechanisms for Thermal Energy Exchange (cold vs. hot)

• If an organism is cold it will absorb thermal energy from the environment

• If an organism is warm it will release thermal energy into the environment

what two groups can all animals be categorized into based on the stability of their body temperature

Homeotherms

• Maintain a stable internal temperature, regardless of external

conditions.

• Ex. Birds and mammals

Poikilotherms

• Animals with a body temperature that varies considerably in

response to external conditions.

• Ex. Fish, amphibians, reptiles, and invertebrate

what are the Two general types of mechanisms that animals use to regulate their body temperature

Endotherms

• Animals that are able to internally regulate their own body temperature

by physiological processes.

Ectotherms

• Animals that use behavioral mechanisms to regulate their body temperature and absorb thermal energy from their environment

what are Endotherms more successful at than ectotherms?

• maintaining a stable body temperature

• Endotherms keep their bodies at optimal temperature by regulating the amount of thermal energy that is generated

what are some behavioural and physiological adaptations that help endotherms thrive

1. Torpor

• A short-term state of reduced metabolic rate and body temperature that reduces the demand for energy during the night or day.

• Ex. Bats, hummingbirds.

2. Hibernation

• A state of greatly reduced metabolic rate and activity that enables an animal to survive the winter by reducing the demand for energy when food is unavailable.

• Ex. Bears, Arctic ground squirrel

3. Estivation

• A state of torpor that enables an animal to survive the summer by reducing the demand for energy.

• Ex. Lungfish, Toads, Frg

what are some other other thermoregulatory behavioural and physiological adaptations used by different species.

Ex. Insects - core body temp. maintained by exercise (exercise endotherms)

Ex. Dogs – uneven distribution of fur that aids thermoregulation; fur is thickest over the back and sides of body and tail, and thinnest over the belly and legs… when dogs are cold, they curl into a ball so only the thickest hair surfaces are exposed to the air

Osmotic pressure

results from the difference in solute concentration across a

selectively permeable membrane

Hyperosmotic (hypertonic)

solution that has the lower concentration of water

Hypoosmotic (hypotonic)

solution that has the higher concentration of water

Isoosmotic (isotonic)

two solutions have equal water concentration

hydrostatic/water pressure

• this is important in plan cells (cell wall)

• Balance between hydrostatic pressure on one side of a membrane must equal the osmotic pressure on other side because Water movement stops even if concentration is different

Osmoregulation and Excretion

• Process of actively regulating osmotic pressure of bodily fluids

• Cells regulate ionic & pH balance in addition to osmotic pressure

– Ions and toxic compounds (nitrogenous components) must be eliminated and filtered out of bodily fluids by liver and kidneys

what are the ways different animals get rid of amino groups (Deanimation)

1. Ammonia - Fish, larva amphibians, aquatic invertebrates

2. Urea - mammals, sharks, rays, aquatic reptiles, adult amphibians

3. Uric acid - Terrestrial reptiles, birds, insects

Complex compounds

simple compounds (some are useful or toxic)

what do the Kidneys do?

• Remove waste

• Balance pH

• Maintain H2O balance

where does Deanimation occur

in the liver

how much water to humans lose a day and how?

humans lose 2L H2O per day through urine, perspire, exhale

what affects out decreases in water have?

1. decrease 1% = thirst

2. decrease 5% = faint/pain

3. decrease 10% = death (can only last 2 days without water)