Category Archives: Animal Physiology

Endocrine function

Invertebrate endocrine systems The endocrine or hormonal system (i.e. the use of body fluid-borne chemical messengers) together with the nervous system make up the control and coordinating systems of animals. However, there are major differences in the way in which control is achieved within the two systems. Firstly, the endocrine system works by transmitting chemical… Read More »

The mechanism of hormone action

For any hormone to exert its biological effect it must interact with its own specific receptor. The receptor, usually a large protein molecule, has a unique three-dimensional shape that will only bind a particular hormone or analogs of that hormone {compounds which possess a chemical structure which is very similar to the hormone concerned). As… Read More »

Invertebrate endocrine systems

Invertebrate animals rely heavily upon neuroendocrine control systems as opposed to classical endocrine systems. However, as invertebrates have become more and more complex, both in structure and physiology, so have the physiological functions controlled by the endocrine system. This is partly because higher invertebrates, e.g. molluscs, have better-developed circulatory systems than lower invertebrates such as… Read More »

Vertebrate endocrine systems

In contrast to the invertebrate endocrine system, the emphasis in the vertebrate endocrine system is on classical endocrine organs with many physiological processes controlled by these organs. However, the nervous system still exerts an influence over the endocrine system since some of the peripheral endocrine organs are under the control of the anterior pituitary, which… Read More »

Receptors and effectors

So far, the functioning of individual nerve cells and how they can be used collectively to form nervous systems has been described. Collectively, nervous systems provide information about what is happening in the immediate environment of an animal. This may either be the internal environment, e.g. the concentrations of particular ions in the body fluids,… Read More »

Sensory receptor function

The overall job of sensory receptors is to act as transducers. That is, they convert (transduce) energy from one form, e.g. light, temperature, into electrical activity, ultimately action potentials. The first step in the process is a change in the ionic permeability of the membrane of the sensory receptor, thus altering its ionic conductance. This… Read More »

Sensory reception

Listed earlier were the types of sensory information that could be detected by animals. What follows is a brief elaboration, detailing what types of sensation within these general groupings can be detected by animals. Chemoreception Chemoreception is the detection of specific chemicals by a sensory receptor. Interaction of the chemical with its receptor results in… Read More »

Effectors ― the responses to sensory information

Having gathered various types of sensory information, animals have to take appropriate action based upon the information gathered. Effectors may be defined as anything capable of producing a biological response. This can range from muscles producing movement ― an overt biological response ― to endocrine glands secreting hormones to alter some aspect of metabolism, e.g.… Read More »

Muscle and movement

Muscle types Muscle may be roughly divided into two types: striated muscle and smooth muscle. Striated muscle itself may be further subdivided into skeletal muscle and cardiac muscle. Skeletal muscle is under voluntary control. The fine structure of skeletal muscle will be described later. Cardiac muscle, as the name suggests is muscle which makes up… Read More »

Skeletal systems

Muscles only do biological work when they contract; relaxation is a passive process. Therefore, muscles are usually found in antagonistic pairs, so that when one muscle group contracts and performs work the other relaxes. However, in order to perform useful work, such as movement, muscles need something to pull against. In vertebrates, it is the… Read More »