Hormonal Control in Animals

Question 1

Basic components of a control system

Answer 1

(1) input, (2) process being controlled, (3) output, (4) sensing elements, and (5) controller and actuating devices.

Question 2

Difference between a positive and negative feedback system. Which is the most common in vertebrates?

Answer 2

Positive- response continue
Negative -response is reversed or negated
Vertebrate homeostatic control mechanism to display negative feedback.

Question 3

How does feedback occur?

Answer 3

The linkage of all components of the control system allows the output to be regulated on terms of the input-feedback occurs

Question 4

Define hormone?

Answer 4

A chemical produced by endocrine gland; part of control and coordination system; capable of bringing about specific response to a particular stimulus.

Question 5

What factors control the release of hormones?

Answer 5

• The presence of a specific metabolite in the blood
• Presence of another hormone in the blood
• The stimulation by the automatic nervous system

Question 6

How do hormones influence target cells?

Answer 6

• Change permeability of the membrane to particular chemicals
• Influence enzymes located in the membrane
• Influence cell organelles
• Activate genes to bring about specific protein production

Question 7

Role of the hypothalamus in hormone release?

Answer 7

• The hypothalamus produce releasing and release- inhibiting hormones
• The hypothalamus controls the release of hormones from adeonhypophysis (anterior pituitary)

Question 8

Why the hypothalamus the control centre?

Answer 8

• Collects information from other parts of the brain
• Monitors levels of hormones and other chemicals in the blood
• Produces ADH, oxytocin transported and stores in the neurohypophysis

Question 9

Why is the pituitary gland the master gland?

Answer 9

The multiplicity of hormones released by the pituitary gland

Question 10

What is the self regulating endocrine gland?

Answer 10

Some endocrine glands are not under the sole control of the hypothalamus and pituitary gland.
- Respond directly to changes of metabolites in the blood
Example- the secretion of insulin and glucagon from the pancreas are responses to blood sugar levels
Adrenal cortex- under direct nervous control