Communication and homeostasis Flashcards
Compare nervous control and hormonal control
d
Compare nervous and hormonal control
Homeostasis definition
Maintenance of a stable internal environment around a set point, despite external / internal environment changes
What is negative feedback
A mechanism that reverses a change bringing the system back to optimum
What is positive feedback?
The mechanism that increases a change, taking the system further away from the optimum. This tends to be harmful and is not involved in homeostasis
Why is it necessary to control body temperature?
Optimum temperature for enzyme activity. Molecules have more kinetic energy so more frequent successful collisions so increased enzyme substrate complexes formed so increased rate of enzyme activity. If temperature gets too high, enzymes denature so rate fall. Too high temp = hyperthermia leads to organ failure. Too low temperature = hypothermia
What are endotherms?
Organisms that use heat from metabolic reactions to maintain body temperature so have higher metabolic rate. Body temp controlled within strict limits. Activity level independent of temperature
What are ectotherms?
Organisms that rely on external sources to maintain body temp - cannot increase rate of metabolism to increase body temp. Body temp fluctuates with external temp. Activity level depends on external temp - higher = more active as enzymes at optimum.
Advantages and disadvantages of ectotherms
ADVANTAGES:
-lower respiratory rate required
-lower food required
more of their food converted to growth
-can survive longer without food
DISADVANTAGES:
-more vulnerable to large fluctuations in external temp
-can not exploit as many locations
-more susceptible to predation as less active
Describe the hypothalamus
Monitors temperature of blood flowing through it. Receives impulses from peripheral temperature receptors in skin. Sends impulses via motor neurones to sweat glands, muscles in arterioles, skeletal muscles, hair erector muscles
What happens in vasodilation?
If body temp gets too high, smooth muscle in arteriole walls relaxes so that arterioles dilate. More blood flows through capillaries near surface of skin so more heat loss from body via radiation
What happens in vasoconstriction?
If core body temperature gets too low, smooth muscle in arteriole walls contracts which constricts the arterioles so they get more narrow. Less blood flows through capillaries close to surface of skin as blood is redirected through shunt vessels which are found in deeper layers of the skin, so less heat lost from body
How does sweating cause heatloss?
Glands in skin produce sweat. Water in sweat evaporates by absorbing heat from the body which requires lots of energy as water has a high latent heat of vaporisation
