Unit 2 Topic 1 Maintaining the internal environment

Question 1

Differentiate between sensory and motor neurons

Answer 1

sensory - carry signals from outer part of body into CNS, short axon, consist of receptor, one long dendron, follow afferent pathway, unipolar, found in skin, eyes, tongue and nose
motor - carry signals from CNS to outer parts of body, long axon, don’t have receptor, many short dendrons, follow efferent pathway, multipolar and are found in muscles and glands

Question 2

Explain action potential

Answer 2

1. Resting potential at -70mV, uneven balance maintained
2. Depolarisation: sodium channels open -> more positive inside -> causes short burst of electrical energy along axon (action potential)
3. Repolarisation: action potential finished -> sodium channels close and potassium channels open -> positive charge outside membrane
4. Hyperpolarisation/refractory period: temporary overshoot (membrane potential slightly more negative than usual) until balance is achieved

Question 3

What is signal transduction?

Answer 3

set of chemcical reactions in a cell that occurs when a molecule attaches to a receptor on the cell membrane

Question 4

What are hormones?

Answer 4

regulatory chemicals of the control and coordination system; capable of bringing about a specific response to a particular stimulus

Question 5

How is a cell’s sensitivity to a specific hormone related to the number of receptors it displays for that hormone?

Answer 5

An increase in receptors = upregulation, decrease = downregulation

Question 6

What is the difference between an ectotherm and endotherm

Answer 6

ectotherm - regulation of body temp depends on surrounding environment
endotherm - can maintain a constant body temp independent of the environment

Question 7

What are structural features of thermoregulation in endotherms?

Answer 7

brown adipose tissue which stores large amounts of high-energy lipids, the cells of which contain large numbers of mitochondria, insulation which reduces the rate of heat transfer

Question 8

What are behavioral responses to thermoregulation in endotherms?

Answer 8

kleptothermy (huddling in groups to share body heat), hibernation (which is a decreased metabolic rate association of blood flow in animals during winter), aestivation (prolonged torpor in response to high environmental temperature and low water availability), topor (short-term state of decrease physiological activity in an animal, usually with a reduced body temp and metabolic rate as a result of cold conditions

Question 9

What are physiological mechanisms used in thermoregulation of endotherms?

Answer 9

countercurrent heat exchange, thermogenesis - heat production in organisms by metabolism

Question 10

what are homeostatic mechanisms used in thermoregulation of endotherms?

Answer 10

insulin and thyroid hormones

Question 11

what is the difference between osmoregulators and osmoconformers

Answer 11

osmoregulator - actively controls internal salt concentrations independently of the salt concentrations of the environment
osmoconformer - marine organism that maintains internal environment that is isotonic with its external environment

Question 12

What are some mechanisms that maintain water balance?

Answer 12

lungs, kidney, uric acid as nitrogenous waster, behavioral response to heat

Question 13

define hydrophytes

Answer 13

plant adapted to grow wholly or partly submerged in water or wet environments

Question 14

define mesophytes

Answer 14

plant adapted to grow in well-watered soil

Question 15

define xerophytes

Answer 15

plant that has adaptations to survive in an environment with little liquid

Question 16

define halophytes

Answer 16

plant that grows in waters of high salinity