Lecture 3 - Homeostasis

Question 1

What did Bernard say about the definition of homeostasis?

Answer 1

Its the consistency of the internal environment that is the condition of free and independent life

Question 2

Who coined the term homeostasis?

Answer 2

Cannon coined the term homeostasis, and its meaning of maintaining a constant internal environment

Question 3

What sort of fluctuations does the external environment have?

Answer 3

Large fluctuations in things such as diet, water availability and temperature

Question 4

What sort of fluctuations does the internal environment have?

Answer 4

Small fluctuations in things like temperature, pH, glucose and blood pressure

Question 5

What is negative feedback?

Answer 5

It aims to maintain a controlled variable at its set point, like in response to a rise and fall in blood pressure

Question 6

What is positive feedback?

Answer 6

Where an initial stimulus causes a response which reinforces itself

Question 7

What is an example of positive feedback occurring?

Answer 7

Blood clotting
Damage to the blood vessel occurs, leading to activation of clotting factors which activates thrombin, which causes formation of the blood clot

Question 8

What is the control system of the endocrine system in terms of homeostasis?

Answer 8

It has long term effects involving hormone control
The hormones often involve thyroid hormones which work with the metabolism, and growth hormones
Has positive and negative feedback systems

Question 9

What is the control system of the nervous system in terms of homeostasis?

Answer 9

Has rapid, short term effects

Question 10

What are the subdivisions of the nervous system?

Answer 10

• Central nervous system
• Peripheral nervous system, which splits into somatic and autonomic that splits further into sympathetic and parasympathetic

Question 11

What are the neurones involved in the autonomic nervous system?

Answer 11

The preganglionic neuron in the CNS, the postganglionic neuron in the peripheral which then reaches the target cell

Question 12

What is the length of the pre and post ganglionic neurons in the sympathetic division?

Answer 12

Preganglionic = short
Post ganglionic = long

Question 13

What is the length of the pre and post ganglionic neurons in the parasympathetic division?

Answer 13

Preganglionic=long
Postganglionic= short

Question 14

Where do the neurones originate in the sympathetic division?

Answer 14

In the thoracic and lumbar areas of the spine

Question 15

Where do the neurons originate in the parasympathetic division?

Answer 15

The cranial and sacral regions of the spine

Question 16

What do post ganglionic fibres release in the sympathetic division?

Answer 16

Noradrenaline which is received by the target cells a and B adrenergic receptors

Question 17

What do post ganglionic fibres release in the parasympathetic division?

Answer 17

Acetylcholine which is received by the target cells muscarinic receptors

Question 17

What are the stages of the negative feedback process?

Answer 17

A change in variable occurs, leading to the sensor which passes onto the integrating sensor. This is the afferent pathway
The integrating centre passes to the effector, which responds. This is the efferent pathway