LS2:Lecture 16

Property of system (cell/organism) that regulates its internal environment to maintain stable, constant conditions of various properties

• 1. Concentration of oxygen and carbon dioxide
• 2. pH
• 3. Concentrations of nutrients and waste
• 4. Salt concentrations
• 5. Temperature

Feedback mechanisms control homestasis

• Error signals provide feedback
• -suggest corrective actions

Negative feedback

to bring the system back to the "set point" level

the desired state the body wishes to achieve

• 1. Stimulus body temperature rises above 37.2 C,
• 2. receptor in hypothalamus receives this error signal
• 3. Blood vessels will be increased and sweat glands in skin
• 4. Increased blood flow to skin which causes increased sweating, the stimulus removed, homeostasis is restored

• 1. Stimulus: Body Temperature falls below 37.2 C
• 2. the body’s receptors pick up these signals and
• 3. the hypothalamus in the brain (thermoregulatory center in the brain Sends command to blood vessels and sweat glands in skin and the skeletal muscles
• 4. Response: decreased blood flow to skin, decreased sweating, shivering, stimulus removed, homeostasis is restored.

• 1. Beta cells secrete the hormone insulin
• 2. Increased rate of glucose transport into target cell, rate of glucose utilization and ATP generation,
• 3. conversion of glucose to glycogen (liver, skeletal muscle), increased amino acid and protein synthesis, and fat synthesis (adipose tissue)
• 4. Result is decreased blood glucose concentration and return to the set point

• 1. accelerates and amplifies/intensifies a response away from the “set point” level
• -(not common in biological systems, taking you away from set point)

• 1. time limitation-processes in the body that must be completed within a constrained time frame are usually modified by positive feedback
• 2. Intensification of stress- During a positive feedback process, the initial imbalance or stress is intensified rather than reduced as it is in negative feedback

• 1.Head of fetus pushes against cervix
• 2. Nerve impulses from the cervix are transmitted to the brain, where the brain stimulates the pituitary gland to secrete oxytocin
• 3. Oxytocin carried in the bloodstream to uterus, it then stimulates uterine contractions and pushes fetus towards cervix

• 1.Nervous system
• 2. Endocrine system
• 3. cells
• 4. tissues
• 5. organs

• 1. Epthelial
• 2. Muscle
• 3. Connectve
• 4. Nervous

• 1. Create boundaries between inside and outside of the body (give some examples)
• 2. Filtration and transport function

• 1. Generate forces and cause movement
• -Skeletal muscle
• -Cardiac muscle
• -Smooth muscle

attach to bones, responsible for locomotion

makes up the heart, responsible for the beating

involuntary movement caused by forces in hollow internal organs such as the gut, bladder

• 1.Dispersed populations of cells embedded in an extracellular matrix that they secrete
• -Chondrocytes
• -Adipose cells
• -Red blood cell

• 1. cartilage cells that provide rigid structural support.
• 2. Secrete an extracellular matrix rich in collagen and elastin fibers

• 1. loose connective tissue that stores lipids (fat used for stored energy).
• 2. Cushions organs and also provides a barrier to heat loss

cells dispersed in an extensive liquid extracellular matrix called plasma.

• 1. senses stimuli and sends response impulses to the different parts of the body.
• -Neurons
• -Glial cells

• 1. various shapes and sizes
• 2. encode information as electrical signals which travel along axons to communicate with other neurons or muscles by releasing neurotransmitters
• 3. (control organ systems)

• 1.do not generate or conduct electrical signals
• 2. provide supporting functions for neurons.
• 3. Glial cells outnumber neurons

organs

usually all types

• 1. digestive tract is lined with epithelial cells.
• 2. Some secrete mucus, digestive juices, hormones, and some absorb nutrients.

• 1. underlies the epithelium and contains the connective tissue (contains blood vessels, neurons and glands).
• 2.The smooth muscle layer contracts from the nervous tissue signals to move food through

Epithelial and connective tissue to protect the system

Around 40C

cells will die

• 1. water bears
• - can survive extreme conditions

• 1.wood frog.
• -Tend to remain very still until the cold passes, wait for ideal temps

between 0-40C

Temperature s determined by external sources of heat

Body temperature is maintained by heat produced metabolicallyand through active mechanisms of heat loss

• 1. ability to span different environments (niche expansion and nocturnal ability)
• 2. reproduce when opportunity arises
• 3. can acquire resources (eat) at all times

• 1. High energy use to maintain body heat
• 2. Need to constantly acquire resources (eat)

• 1. Plasma membrane is more leaky for K+ and Na+;
• 2. More Na+ATPase pump activity to maintain ion concentrations.

so by maintaining metabolic functions in cells, we provide heat for our cells

• 1. Leaky cell- K exits cell through its channels
• 2. voltage gated channels for Na+ are closed
• 3.At first you have the ions move with their gradient,
• 3. but taking the Na+/K+ pump moves them against their gradient in order to maintain the proper state for the cell.
• 4. Results in the side effect of generating heat

• 1. sit in the shade
• 2. lick their forearms to cool themselves off.
• -Licking their forearms causes blood vessels to expand which causes increased blood flow

1. Spray themselves with water

1. forms shade for their children for them to stay cool when there are not a lot of trees

• 1.painting
• -evaporates water on the tongue, cools themselves

• 1.The lizard moves outside when the sun comes out to increase its body temp,
• 2. move into the shade at the sun’s peak, moves back into the burrow come nightfall

Helps them maintain body temperature

Increased blood flow to the skin increases heatloss and lowers body temperature.

Constriction of blood vessels to the skin resultsin less heat loss.

• (+/-): to/from nearby objects
• Ex. lizard gains heat from sun, or loses heat to surroundings in shade

• (+/-): to/from touching objects
• Ex. lizard gains heat laying on warm rock or loses heat laying on surface of cool burrow

• (+/-): into wind/moving water
• Ex. body is warmed by hot wind or cooled by coldwind

(+): from body's generation of heat

(-): from moist body surfaces

metabolism + solar radiation (Rabs)

radiation (Rout) + convection + conduction + evaporation

the Hypothalamus

• Also sensors in the skin can shift the set point
• -(lower when skin warm)

As you cool the hypothalamus, the metabolic rate of the squirrel will rise and cause the squirrel to warm up (compensation for a cooling of the hypothalamus)

• Heating the hypothalamus causes the metabolic rate to drop which causes body temperature to drop
• -(suppresses metabolic heat production to favor hit loss