Zoology Flashcards
Introduction of Pre-erythrocytic cycle
The infected female Anopheles bite a human, along with the saliva, injects the sporozoite stage of Plasmodium into the human blood stream.
What are sporozoite and their functions?
The sporozoite is a minute, thread-like organism tapering at both ends. After half an hour, the sporozoite penetrates a liver parenchymal cell. Within the liver cell, The sporozoite grows to form a large round schizont. By dividing its multiple fission, the schizont forms a large number of merozoites in 8 days. This asexual multiplication is called pre-erythrocytic Schizogony but it doesn’t occur in the red blood corpuscles, the erythrocyte cell.
Exo-erythrocytic cycle
The weakened parasitised liver cell P.vivax, P.malariae,P.ovale rupture freeing the merozoites , some of which re-enter the liver cell and repeat the cycle called exo-erythrocytic schizogony But most of them enter the blood stream and invade the blood corpuscles. P.falciparum is well known as it doesn’t enter the liver cell
Processes of Respiration: Respiratory System
(1)External respiration
during which a simple exchange of O2 and CO2 occurs between the body and environment of individuals.
(2)Gaseous transport
during which blood transports O2 to body tissues and CO2 from cells to respiratory organs.
(3)Internal respiration
during which gaseous exchange between blood and body cells occurs through the medium of tissue fluid.
(4)Cellular respiration
during which chemical degradation of food substances occurs within the cells for obtaining bio-energy from these.
Bronchial tree
Trachea and its several braches entering into lungs are known as bronchial tree. Each primary bronchus (branch of trachea) divides into several secondary bronchi which divide into tertiary bronchi. Each tertiary bronchus divides into many bronchioles which divide into few terminal bronchioles (6 in man). Each terminal bronchiole divides into a number of respiratory bronchioles:
Each of these divides into 7 to 11 alveolar ducts, each in turn divides into few atria.
Ventilation of lungs
-Ventilation of lungs is fixed at a rate throughout life.The air going to be aspired is made free from large sized bacteria,particles,dust and spores which get entangled in the hairs of nasal speculum and its temperature is brought to body temperature by mucus and blood supply of the wall.
-During inspiration, the diaphragm flattened, the anterior intercostals pull the ribs forward and raise the sternum, the lungs strentched and the alveoli are distended. The pressure of air in alveoli becomes negative (-1 to -3 mm of Hg) and the air is sucked into the alveoli via the conducting part of the respiratory system.
-During expiration, all muscles contracted during inspiration relax the lungs recoil . The air pressure rises (+1 to +3 mm of Hg) than atmospheric pressure and air is expelled out of the lungs.
Double circulation
Double circulation: In tetrapoda, the atrium is divided into the auricles by an interauricular septum thus oxygenated blood comes to the left auricle and deoxygenated blood into the right auricle. this blood has to go to the lungs for aeration, and this necessitates a double circulation through the hean, once an oxygenated blood stream coming to the heart, and once a deoxygenatedblood stream from the great veins. Such heart is a pulmonary heart.
In amphibians the ventricle is partially divided and there is some mixing of oxygenated and deoxygenated blood in the heart. So it is called incomplete double circulation.
Beginning with reptiles the ventricle begins to show a division into two parts by an interventricular septum, this division is complete in crocodilians, birds and mammals, which have two separated ventricles. It is called complete double circulation. The two blood streams never mix, the oxygenated blood lies in the left auricle and ventricle, and deoxygenated blood in the right auricle and ventricle.
Capillaries
Capillaries are found at the ends of the finest arterioles and connect the arterial and venous systems. They have walls of only a single layer of endothelial cells. The total length of an adult man’s capillaries is estimated at 96000 km, giving an enormous surface area for gas, food and waste exchange. There are three types of capillary:
• continuous capillaries in muscle cells;
• fenestrated capillaries (with pores) in kidneys and endocrine glands;
• sinusoids (discontinuous capillaries) with membrane-covered gaps between endothelial cells in liver and spleen.
Capillary blood flow
Blood leaves the heart flowing at 30-40 cm sec’ but slows to 2.5 cm sec-‘ in arterioles and to less than 1 mm sec’ in capillaries, where it stays for a few seconds while gas and nutrient interchange occurs. The single-cell endothelium permits small molecules to pass through while retaining large molecules and cells. Hydrostatic arterial blood pressure forces water and small solutes into the tissue fluid spaces at the arteriolar end of the capillary. The colloidal osmotic pressure of the plasma proteins pulls water and small solute back into the blood by osmosis at the venous end of the capillary.
Fluid not reabsorbed by capillary is drained by the lymphatic system.
Veins
Venules drain form capillaries. Tiny venules unite to from veins. The smallest venules are important for pulling back the tissue fluid. The veins drain the blood from the venules to the right atrium of the heart (via venae cavae). The pulmonary vein carries oxygenated blood from the lungs to the left atrium. The hepatic poral vein carries the blood from the capillaries of gut to the capillaries of the liver. Veins have the same tissue layer as arteries but they have much thinner tunica media and have less elastic tissue and muscle in the wall. Thus veins are compressible and distensible. Venous pressure is low but the flow of blood is assisted by the massaging of body muscle during movement and in exercise.
Parts of a neuron
Like other cells, a neuron has a nucleus and cytoplasm. But the cytoplasm extends far beyond the main body of the cell. A neuron is made of three parts,
The cell body contains a nucleus and several organelles responsible for maintaining metabolism, growth and repair. They may grow and be repaired to a degree, they cannot reproduce. Once a mature nerve cell of the brain or spinal cord dies, it cannot be replaced.
Dendrites are numerous, short, thread-like processes extending out from the cell body. A dendrite may be excited or inhabited. They carry impulses toward the cell body. A neuron has as many as 200 dendrites.
Each neuron generally has a single axon, a long process extending as much 1 or 2 meters from the cell body. An axon carries the impulses away from the cell body. Unlike dendrites, an axon is only excited, passing the stimulation on to the next cell.
An axon is enclosed in a fatty insulation sheath called myelin, aids in conducting the electrical impulses. Another covering the Schwann cells which may be present surrounding the nerve cells outside the brain and spinal cord. They enhance peripheral nerve cells which does not include in the brain and spinal cord.
Parts of a neuron
There are three types of neurons classified according to their functions.
The afferent neuron or sensory neuron carries the impulses to the central nervous system. They carry the impulses to the brain or spinal cord from the distant parts of the body where the stimuli are received. There is no sensation until the massage is relayed to the brain and spinal cord. Dendrites of the afferent neurons carry the impulses from the receptor cells that pick up the stimuli.
The efferent neuron or motor neuron carry the impulses away from the central nervous system to the glands or muscles where the physical activities actually occurs. Axons of the efferent neurons terminates in the effectors such as the muscle or glands.
Interneurons lie entirely within the brain and spinal cord and constitute the bulk of nerve cells. They carry impulses from the sensory neuron to the motor neurons and they are involved in processing of the input information of complex activities such as learning, languages and emotion
Anterior pituitary hormone
Anterior pituitary peptide or protein hormone made by discrete cells include
prolactin (PRL) controlling production and secretion of milk, avian nest-building and maintenance of larval state in the amphibians.
Growth hormone promotes body growth.
Gonadotrophins or follicle-stimulating hormone and lutenizing hormone stimulates sex steroid synthesis and release from the gonad.
Thyroid stimulating hormone stimultes production of thyroid hormones.
Adrenocorticotropic hormone stimulates corticosteroid release from the adrenal cortex.
Posterior pituitary hormone
Posterior lobe stores and releases two hormones by the neurosecretory cells from the hypothalamus. Vasopressin or audiuretic hormone (ADH)increases the absorption of water in the kidney tubules and constriction of smooth muscles in the arterioles. Oxytocin causes the contraction of smooth muscles in the uterus during birth and ejection of milk from mammary glands.
Insulin
Insulin lowers blood glucose levels. Of the islet cells, 60% are beta cells; these releases beta cells. Insulin is stored in the islets cells in granules bound to zinc. It is released in response to blood with a high blood glucose level flowing through the pancreas.
Insulin receptors are on the liver, fat and muscles. When insulin interacts with its receptors, glycogenesis is stimulated . In obesity, the levels of glucose and insulin are often both very high. Fasting can increase the number of insulin receptors.
