BIOL 326 -
Animal Physiology Lecture Notes
Nervous and endocrine systems
February 3 -12 , 2010
Dr M. Sweeney-Nixon
Objectives: At the end of this section, you will be able to describe how organismal
homeostasis is maintained in animals.
organization of endocrine and nervous systems in animals.
names of endocrine glands and the hormones they release.
names & functions of hormones & some neurotransmitters (ACH, NA).
Basic homeostatic nervous and endocrine reflexes (including neuro-endocrine
Animals must maintain homeostasis in the face of ‘stress’.
For an animal, stress is not
necessarily what humans define as stress.
It is anything that threatens its survival.
: threatens the ability to produce ATP and do biological work;
changes osmolarity (consistency of blood).
: threatens muscle contraction, including the heart (which
beats/contracts constantly) and the diaphragm, which is essential for ventilation
: threatens blood circulation to the brain & other organs
: threatens tissue water/volume/shape etc
blood CO /
blood pH or O
: threatens proteins and the ability to make ATP
Other: predation, drought, fasting, weight loss, illness etc.
Biological control systems
An animal’s survival depends on receiving and correctly interpreting information from its
external environment (e.g. light, infrared radiation, sound waves, temperature, pressure,
chemicals [taste and smell, pheromones], electric &magnetic fields) and internal environment
(chemicals e.g. glucose, pH, body temperature, pressure).
All animals have
(see intro notes): sensors that monitor physiological variables, afferent and
efferent paths, and an integration center.
In a simple endocrine control system, the
system detects and responds, whereas in the majority of cases, the nervous
system detects and responds using
(see below) or
Thus, “animals have 2 systems of internal communication and regulation, the nervous
system and the endocrine system” (Campbell, 5th ed., p. 894 [from Chapter 45])”.
, as it consists of neurons firing electrical signals (action potentials)
that take only milliseconds.
The released chemical signal has a
contributes to the speed. In contrast, the
- responses require
release of hormones from secretory cells or glands into the circulation (blood or hemolymph);
some effects are on transcription and so responses takes minutes, hours, days and
There is a
endocrine gland or tissue
releases molecules (
) that affect target