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What is Homeostasis?
Property of system (cell/organism) that regulates its internal environment to maintain stable, constant conditions of various properties
To maintain homeostasis cells/organism must control
- 1. Concentration of oxygen and carbon dioxide
- 2. pH
- 3. Concentrations of nutrients and waste
- 4. Salt concentrations
- 5. Temperature
What mechanisms control homestasis?
Feedback mechanisms control homestasis
What provides feedback?
- Error signals provide feedback
- -suggest corrective actions
The most common mechanism to control homestasis
Negative feedback is used to....
to bring the system back to the "set point" level
the desired state the body wishes to achieve
Example of Negative feedback: Body temperature rises
- 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
Example of Negative feedback: Body temperature falls
- 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.
Example of Negative feedback: Blood Glucose is too high
- 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)
Homeostatic system utilizing positive feedback exhibit two primary characteristics
- 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
Homeostatic Regulation of Child Birth through Positive 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
Homeostasis depends on the action and interactions of a number of body systems to maintain optimal conditions
- 1.Nervous system
- 2. Endocrine system
- 3. cells
- 4. tissues
- 5. organs
4 kinds of tissue
- 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
- -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
Red blood cells
cells dispersed in an extensive liquid extracellular matrix called plasma.
- 1. senses stimuli and sends response impulses to the different parts of the body.
- -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
Tissues form _____
What types of tissues do organs include?
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
What covers the abdominal organs on the outside?
Epithelial and connective tissue to protect the system
What temperature do proteins start to denature?
What will happen to cells if temperature falls below 0C?
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
what temperature does most life exist?
Temperature s determined by external sources of heat
Body temperature is maintained by heat produced metabolicallyand through active mechanisms of heat loss
Advantages of being Endothermic
- 1. ability to span different environments (niche expansion and nocturnal ability)
- 2. reproduce when opportunity arises
- 3. can acquire resources (eat) at all times
Disadvantages of being Endothermic
- 1. High energy use to maintain body heat
- 2. Need to constantly acquire resources (eat)
Leaky Cell Hypothesis
- 1. Plasma membrane is more leaky for K+ and Na+;
- 2. More Na+ATPase pump activity to maintain ion concentrations.
By maintaining metabolic functions in cells, we provide _____ for our cells
so by maintaining metabolic functions in cells, we provide heat for our cells
Leaky Cell: Process of generating heat
- 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
Behavioral Regulation: Kangaroos
- 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
Behavorial Regulation: Elephants
1. Spray themselves with water
Behavorial Regulation: Birds
1. forms shade for their children for them to stay cool when there are not a lot of trees
Behavorial Regulation: Dogs
- -evaporates water on the tongue, cools themselves
Behavorial Regulation: Lizard
- 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
what does blood flow to the skin do for endo/ectotherms?
Helps them maintain body temperature
Increased blood flow to the skin increases_______ and lowers ________
Increased blood flow to the skin increases heatloss and lowers body temperature.
Constriction of blood vessels to the skin results in ______
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
Heat in =......
metabolism + solar radiation (Rabs)
Heat out =......
radiation (Rout) + convection + conduction + evaporation
The thermostat of the brain
Also sensors in the skin can shift the_______
- 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 ________ and cause the squirrel to ______(compensation
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 _______which causes body temperature__________
- Heating the hypothalamus causes the metabolic rate to drop which causes body temperature to drop
- -(suppresses metabolic heat production to favor hit loss