study of behaviour (ethology)

Behaviour may be defined as the outwardly expressed course of action produced in organisms in response to stimuli from a given situation. The action modifies, in some way, the relationship between the organism and its environment and its adaptive significance is the perpetuation of the species. All living organisms exhibit a variety of forms of behaviorism activity deter-mined by the extent to which they are able to respond to stimuli. This varies from the relatively simple action of the growth of a plant stem towards a light source, to the complex sexual behavior patterns of territory defense, courtship and mating seen in birds and mammals. Plant behavior is restricted to movements produced by growth or turgid changes and is stereotyped and predictable. The two main activities associated with plant behavior are tropisms and taxes and details of these are described in section. Animal behavior is far more complex and diverse than plant behavior and therefore it is extremely difficult to investigate and account for with any degree of scientific validity. The three main approaches to behavioral studies are the capitalistic, mechanistic and ethological approaches. 

Vitalistic approach

This seeks to account for behavioral activities in terms of what animals are seen to do, and attempts to relate this to changes in the environment. It involves the total rejection of any study of the animal outside its natural environment. The technique has its foundations in natural history and has provided a wealth of valuable data, but it is essentially non scientific since all the observations relate to past events which cannot be tested experimentally.

The meninges and cerebrospinal fluid....

The central nervous system is surrounded by three layers or 'membranes' called meninges  and is completely encased within the protective bones of the skull and vertebral column. The outer membrane forms the tough dun mater which is attached to the skull and vertebrae, and the inner membrane forms the thin Pia mater which lies next to the nervous tissues. Between the two is the arachnid 'membrane'. This includes a space, the arachnophobia space, strands of connective tissue, blood vessels and cerebrovascular fluid (CS). Most of this fluid is contained in the central canal of the spinal cord and continues forward to occupy four expanded cavities within the brain called the ventricles. The fluid therefore comes into contact with the outside and inside of the brain, and blood vessels lie within it for the supply of nutrients and oxygen to the nervous tissues and the removal of wastes. It also contains lymphocytes to protect against infection. Meningitis is caused by an infection of the meninges. About 100 cm3 of fluid is present in the CNS and, apart from its nutritive, excretory and defensive functions, it supports the nervous tissues and protects them against mechanical shock. A continual circulation of fluid is maintained by cilia ted cells lining the ventricles and central canal. 

The Spinal Cord

The spinal cord is a cylinder of nervous tissue running from the base of the brain down the back. It is protected by the vertebrae of the backbone (vertebral column) and the meninges. It has a shaped central area of grey matter, composed of nerve cell bodies, dendrites and synapses surrounding a central canal which contains cerebrovascular fluid. Around the grey matter is an outer layer of white matter, containing nerve fibers whose fatty myelitis sheaths give it its characteristic color. There are 31 pairs of spinal nerves and these divide dose to the spinal cord to form two branches called the dorsal root and ventral root. 

 

The hip and thigh

The lower limb, similar in structure to the upper, is modified by its functions of support and propulsion of the body. During its development there is rotation medially on its long axis, so that the flexion surface lies posterior and the sole of the foot faces backwards and then downwards. The pelvic girdle, unlike the pectoral girdle, is firmly attached to the vertebral column, which allows the transmission of the body's weight through it to the lower limb. In the standing position the center of gravity passes behind the hip and in front of the knee and ankle joints. The weight is distributed between the heel and the balls of the toes, most of it being carried by bones and ligaments, with only a minimal amount of muscle activity being required to maintain balance.

The Deep Fascia

 The deep fascia of the gluten region and thigh forms a investigating layer, the fascia lats, from which medial and later inter muscular septa divide the thigh muscles into distinct com departments. Proximal it is attached in a continuous line to the inguinal ligament, lilac crest, posterior sacrum, sacra tuberous ligament, Islamophobic rams and the body of the pubic . Three centimeters below and 1 cm lateral to the pubic tubercle an oval deficiency in the fascia, the sousaphones opening, transmits the great sousaphones vein. The fascia lam is thickened on the lateral side of the thigh, the tibial tract, which is attached distally to the lateral tibial cotyledon. Glutenous maxims and tensor fascias latte gait Impeachment to the tract. Thus they may assist in extension and mobilization of the knee. Over the political fossa the fascia is by the small sousaphones vein. The fascia a is rather like a pair of women's tights.

The ear,intracranial region and cranial nerves

The organ of hearing and balance is divided into an external ear, conveying sound waves to the tympanic membrane; a middle ear relaying the membrane's vibrations to the internal ear; and the cochlea of the internal ear, which translates these vibrations into nerve impulses. The semicircular canals, the organ of balance, are also in the inner ear. The external ear consists of the auricle (pinny) and the external acoustic meats. The auricle is formed of an irregularly shaped piece of cartilage covered by firmly adherent skin. It has a dependent globule used for earrings and an anterior Travus which projects and overlaps the opening of the menus. The external acoustic meat us (SEAM) passes almost horizontally from the Travus to the tympanic membrane in a slightly anterior direction. It is about 4 cm long. Its cartilaginous lateral third is continuous with the cartilage of the auricle; the bony medial two-thirds are formed mainly by the temporal bone. The meat us is lined by skin containing many wax secreting (coterminous) glands. It is innervated by the horticulturalist nerve anterior and the vague nerve posterior. The translucent tympanic membrane (eardrum)  separating the external and middle ears is oval in shape and lies obliquely, with its outer (lateral) surface facing down-wards and forwards. The handle of the mallets is attached to its medial surface and produces a small elevation on the drum, which can be seen with an periscope as the dumbo. 
 
 The middle car (tympanic cavity;  lies within the temporal bone. It is about 15 mm high, 15 mm long, and its medial and lateral walls curve inwards, being about 2 nun apart in their middle and 6 mm apart at the roof. The cavity, lined in part by cilia ted columnar epithelium, contains three small bones, mallets, incs and spates  the auditory vesicles. The lateral wall is formed mainly by the tympanic membrane. Above and behind the membrane is an upward extension of the cavity, the tympanic recess, which contains part of the mallets and incs. The medial wall has a central bulge, the promontory, overlying the base of the cochlea (see below). Above and behind it is the fenestration vestibule (oval window) and below it the fenestration cochleae (round window). Both these formalin lead to the inner ear. The fenestration vestibule is closed by the footplate of the states and the fenestration cochleae by a fibrous membrane. The anterior wall has two openings, the upper for tensor tympani muscle, which attaches to the handle of the mallets, the lower for the auditory (Eustachian) tube, which communicates with the pharynx. High on the posterior wall is the audits, the opening into the mastoid ant rum. Below it formalin transmit the stampedes muscle to the spates and the chords tympani. The facial nerve grooves the medial wall and then descends the medial and part of the posterior wall in a bony canal.

GASEOUS EXCHANGE IN A MAMMAL

Structure of the respiratory system

The respiratory surface of a mammal consists of many air sacs called alveolar inside a pair of lungs. The lungs are situated next to the heart in the thoracic cavity and arc connected to the atmosphere by tubes. Air passes into the lungs through these tubes. Twelve pairs of bony ribs surround and protect the lungs and heart. intercontinental muscles are attached to the ribs, and a large diaphragm separates the thorax from the abdomen.

These are involved in the ventilation mechanism, as described in section. Air enters the body through two nostrils, each of which possesses a border of large hairs which trap particles in the air and filter them out of the system. While passing through the nasal passages the air is warmed and moistened and its dour detected. Air passes from the nasal passages, through the pharynx and into the trachea. This is a tube which lies in front of the esophagus and extends into the thoracic cavity. The wall of the tube is strengthened and held open by horizontally arranged C-shaped bands of cartilage. The open section of the C is next to the esophagus. The cartilage prevents collapse of the tube during inspiration (breathing in). The cartilage can be seen in a section of the trachea. At its lower end the trachea splits into two bronchi. Within the lungs each bronchus subdivides many times into 

much smaller tubes called bronchi oles. These in turn branch into finer and finer tubes, ending with the alveolar ducts which lead into sacs called alveolar sacs. Into each alveolar sac opens a group of alveolar. A summary of these structures and their main features is provided in. The walls of most of the respiratory passage are lined with cilia ted epithelial cells and goblet cells, which secrete mucus. Mucus traps any particles, such as dust and bacteria, that have managed to pass through the hairs of the nostrils. The beating of the cilia then carries the trapped particles to the back of the buccaneer cavity where the mucus is swallowed. Note that it is not the cilia which trap the particles don't confuse them with the hairs in the nose. Mucus also moistens the incoming air.