Lecture Topic 3: Homeostasis

Who created the term ‘homeostasis’ and in what year?

Walter B. Cannon / 1929

What does homeostasis mean?

Maintenance of a constant internal environment

What is negative feedback control ?

Aims to maintain a controlled variable at its set point

What is a ‘controlled variable’?

Some aspect of the internal environment

What is a ‘set point’?

Value at which the variable should be maintained

What is positive feedback?

Initial stimulus causes a response which reinforces itself

State 3 examples of positive feedback.

Action potential / ovulation / blood clotting

What 2 categories does the CNS split into?

Somatic / autonomic

What 2 categories does autonomic nerves split into?

Parasympathetic / sympathetic

In sympathetic nervous system, would HR increase or decrease?

Increase

In parasympathetic nervous system, would HR increase or decrease?

Decrease 

What is the outflow from CNS in sympathetic

Thoracic / lumbar

What is the outflow from CNS in parasympathetic?

Cranial / sacral

Structure of the preganglionic fibre in sympathetic

Short

Structure of the preganglionic fibre in parasympathetic

Long

What is the ganglionic transmitter in sympathetic?

Ach (N2)

What is the ganglionic transmitter in parasympathetic?

ACh (N2)

Structure of post ganglionic fibre in sympathetic

Long

Structure of post ganglionic fibre in parasympathetic

Short

What is the neuroeffector transmitter in sympathetic?

NA (a or b)

What is the neuroeffector transmitter in parasympathetic?

ACh (M)

Between sympathetic and parasympathetic, which is more active in vegetative situations?

Parasympathetic