Homeostasis intro

Question 1

homeostasis

Answer 1

• body’s attempt to adjust to a fluctuating external environment to maintain internal conditions
• the body maintains a constant balance, or steady state, through a series of monitored adjustments

Question 2

optimal conditions for the body

Answer 2

• temp of 37
  blood sugar level of 0.1%
  blood ph of 7.35
  a systolic blood pressure of 120 mmHg

Question 3

dynamic equilibrium

Answer 3

• homeostasis is often referred to as dynamic equilibrium - a condition that remains stable within fluctuating limits

Question 4

3 functional components to dynamic equilibrium

Answer 4

3 functional components to dynamic equilibrium:
* - sensor–detects change in internal environment and sends signal to control centre
* - control centre–sets rande of values to be maintained, recieves info from sensor, sends signal to effector
* - effector–recieves signal from control centre, restores the normal balance (aka regulator)

Question 5

homeostasis –> blood glucose level

Answer 5

hyperglycemic
- stimulus –> rising blood glucose level
- beta cells of pancrease stimulates to release insulin into the blood, liver takes up glucose and stores it as glycogen, body cells take up more glucose, blood glucose level declines to a set point;simultes for insulin release diminishes
hypoglycemic
- removal of excess glucose from blood, low blood glucose
- alpha cells of pancreas stimulates to release glucagon into the blood, liver breaks down glycogen and releases glucose to the blood, blood glucose level rises to set point; stimulus for glucagon release diminishes

Question 6

homeostasis and feedback

Answer 6

• the body uses a feedback (deletion-correction) system to make adjustments
• two mechanisms: negative feedback and positive feedback

Question 7

positive feedback

Answer 7

• small effect is amplified
• move a controlled variable even further away fromt eh steady state
• allows a single physiological event to occur rapidly, then feedback stops
• less common in the body, example of + feedback loop is birthing process

Question 8

Negative feedback loops

Answer 8

• negative feedback is a process by which a mechanism is activated to restore conditions to their original state

Question 9

body temp (high) - feedback loop

Answer 9

• sensor: thermoreceptors signal increase in temperature
• integrator: hypothalamus turns on colling systems
• effector: skin blood vessels dilate; increased blood flow to skin; thermal energy loss from skin
• effector: sweat glands initiate sweating;evaporation of sweat causes cooling
• result: body temp decreases, hypothalamus turns off colling systems

Question 10

body temp (low) - feedback loop

Answer 10

• sensor: thermoreceptors signal a decrease in temperature
• integrator: hypothalamus turns on warming systems
• effector: skin blood vessels constrict; decreased blood flow to skin, reduced thermal energy loss from skin
• effector: skeletal muscles contract; shivering generates energy production; body hair becomes erect to conserve thermal energy
• result: body temperature increases; hypothalamus turns off warming systems

Question 11

More about Thermoregulation…

Answer 11

The process of regulating internal temperature by negative feedback mechanisms

Thermoreceptors detect deviations from optimal internal temperatures

Different species are adapted to different optimal ranges of temperature

Question 12

Thermoregulation

Answer 12

All organisms will interact with the environment to regulate internal temperatures

Thermal energy is exchanged through one of four mechanisms:
Conduction
Convection
Radiation
Evaporation

Question 13

Endotherms

Answer 13

Mammals (including humans) and birds are referred to as endotherms
They are able to maintain a constant body temperature regardless of their surroundings

Endotherms adjust to decreases in environmental temperatures by increasing the rate of cellular respiration to generate heat

The hypothalamus is the region of the vertebrate’s brain responsible for coordinating thermoregulation (core T° is 37°C in humans)

Question 14

Ectotherms

Answer 14

Invertebrates and most fish, amphibians and reptiles are referred to as ectotherms
They depend on air temperature to regulate metabolic rates

Some reptiles have developed behavioural adaptations to regulate body temperature:
Taking in sun while lying on rocks
Retreating to shaded areas

Some very active fish, such as tuna, have highly adapted circulatory systems designed to conserve heat
Some of their internal organs are significantly warmer than the surrounding water

**snakes can eat like once a month, because they dont need that much energy to fuel their warmth
**

Question 15

Response to Heat Stress

Answer 15

When thermoreceptors detect a rise in body temperature a nerve message is coordinated within the hypothalamus
a signal is sent to the sweat glands to initiate sweating
the evaporation of perspiration from the skin causes cooling

at the same time, a nerve message is sent to the blood vessels in the skin, causing them to dilate
this allows more blood to flow to the skin

along with water, valuable salts are also carried to the skin’s surface and lost with perspiration

• vasodialation

Question 16

Response to Cold Stress

Answer 16

When thermoreceptors detect a drop in body temperature a nerve message is coordinated within the hypothalamus

a signal is sent to organs and the arterioles of the skin to cause smooth muscles to contract and the arterioles to vasoconstrict
- this limits the amount of blood flow to the skin and retains heat in core

at the same time, nerve messages are carried to the smooth muscle that surrounds the hair follicles in your skin, causing the hair to “stand on end”…creating a small bump called a “goosebump”
- the erect hair traps warm, still air next to the surface of your skin and helps reduce heat loss

Question 17

Cold stress response –> shivering

Answer 17

In addition, the hypothalamus also sends nerve messages that initiate shivering
- the shivering response is a rhythmic contraction of skeletal muscle
- Cycles of rapid muscle contractions (10-20 times per minute) generate heat production by increasing metabolism

Prolonged exposure to cold can create a hormonal response that also elevates metabolism
- This type of heat production is most often associated with a special adipose tissue called brown fat
- Brown fat is especially important in newborns because they lack the ability to shiver

Question 18

Summary of Thermoregluation

Answer 18

Thermoregulation involves negative feedback:

Cooling the body:
Evaporation of sweat
Dilation of blood vessels (dissipates heat)

Conserving heat:
Constriction of blood vessels
Shivering
Erection of body hairs (more heat is generated by increased metabolism)

Question 19

hypothermia

Answer 19

A condition is which the body core temperature falls below the normal range (drop in 2°C)

However, some people, mainly small children, have survived sustained exposure to cold temperatures

Explained by the mammalian diving reflex
When a mammal is submerged in cold water, the heart rate slows down and blood is diverted to the brain and other vital organs to conserve heat