ZOO301 Final Term Past Papers

NERVOUS SYSTEM: The

system that integrates, coordinates and communicates the various systems of the organism.

• Neurons-Functional

unit of Nervous system

• They are specialized

cells to produce signals, which are communicated from one part to the body to other. Neurons have two important propertiesthe excitability and conductivity. • Structurally the neuron is composed of dendrites, cell body and axon. • The language of neuron in the nerve impulse or action potential. The plasma membrane of a living neuron is polarized i.e. there is trans membrane potential. • Outside is positively charged and inside negatively charged. • The sodium-potassium ATPase pump and diffusion of ions across membrane channels maintain this polarization. When a stimulus is applied to a resting neuron, the neuron depolarizes causing an action potential. • In myelinated neuron the conduction of impulse is saltatory. • Nerve impulse is transmitted from one neuron to the next through synapsis, which involve neurotransmitters. The more complex an animal, the more detailed its i) Nervous System ii) Cephalization iii) Bilateral symmetry iv) More interneurons v) The more complicated behavior. THE VERTEBRATE NERVOUS SYSTEM

System (CNS) has two main divisions: brain and spinal cord. • 2. Perpheral Nervous System (PNS)- all the nerves out side the brain and spinal cord. THE VERTEBRATE BRAIN is divided into: fore brain, • mid brain and the • hind brain. • The fore brain is composed of cerebrum, thalamus, hypothalamus, pineal gland and the pituitary. The mid brain is a thickened region of grey matter that integrates visual and auditory signals. • The hind brain is continuous with spinal cord and includes the cerebellum, pons and medulla oblongata. THE SPINAL CORD serves two functions:

• a) It is the connecting

link between brain and the body.

• b) It is involved in the

reflex actions. CRANIAL NERVES: • In reptles, birds and mammals the CNs are 12 pairs: I. Olfactory S II. Optic S III. Oculomotor M IV. Trochlear M V. Trigeminal Mix VI Abducens M VII. Facial Mix VIII. Vestibulocochlear S IX. Glossophryneal Mix X. Vagus Mix XI. Accessory Mix XII Hypoglossal Mix • Fishes and Amphibians have 10 pairs of Cranial Nerves. AUTONOMIC NERVOUS SYSTEM: • ANS consists of:

a) Sympathetic and

1. Para sympathetic NS These are antagonistic to each other.

PARASYMPARHTIC NS:

• It contains nerves that

arise from the brain and sacral region of the spinal cord.

• It relaxes the body and

inhibits or slows many energy functions.

• Rest and digest SYMPATHETIC NS: • It contains nerves that arise from the thoracic and lumbar regions of the spinal cord. • It prepares body for intense physical activity. • Fight and Flight Receptors: 2. Their structure is

pathways. creating a generator potential. sensation, such as sound

INVERTEBRATE SENSORY RECEPTORS:

• Baroreceptors
• Chemoreceptors
• Georeceptors
• Hygroreceptors
• Photoreceptore
• Proprioceptors
• Tactile receptors VERTEBRATE SENSORY RECEPTORS • Lateral-line system and mechanoreceptors • Hearing & Equilibrium in air and water. • Skin sensors of heat and cold. • Skin sensors of mechamical stimuli. • Sonar. • Smell • Taste • Vision Receptors:

creating a generator potential. 2. Their structure is

pathways.

sensation, such as sound. INVERTEBRATE SENSORY RECEPTORS:

• Baroreceptors-

statocysts

• Chemoreceptors-
• Georeceptors-

statocysts, that respond to gravity

• Hygroreceptors-detect

water content of air.

• Phonoreceptors-such

as tympanic organs. Photoreceptorssuch as stigmata, ocelli, compound eyes, complex camera eyes that respond to light. • Proprioceptorsthat respond to mechanically induced changes caused by stretching. • Tactile receptorssuch as bristles, sensilla, spines, setae and tubercles that sense touch. VERTEBRATE SENSORY RECEPTORS • Lateral-line systemcontain neuromasts. They are present in the head area of most fishes, some amphibians and platypus. They are sensitive to water disturbance. Lateral Line System in jawless fishes, jawed fishes and certain amphibians contain ampulary organs, which are sensitive to electric currents in water and production of generator potential.

Hearing & Equilibrium in air and water. Hearing (audition) and equilibrium (balance) are considered together because both sensations are received in the same vertebrate organ—the ear. Skin Sensors of Heat and Cold. • Pit organs in snakes • Skin Sensors of Mechanical StimuliThey are: • Bare sensory nerve endings, • Meissner’s corpuscles, • Bulbs of Krause, • Paccinian Corpuscle • Vibrissae Vision: • Eyes, Median eye • Photoreceptor cellsrods and cones • Monocular and Binocular vision, • Accommodation, • Rhodopsin Sonar- • Echolocation in bats, whales, dolfin, cave dwelling birds. • Smell- • Receptor in nasal cavity • Jacobson’s organs. • Taste or gustation: • Taste buds on tongue. Barbles in fishes • Pharynx in birds are involved in:

• 1. Communication
• 2. Maintenance of

homeostasis in an animal’s body,

• 3. Body’s response to

various stimuli.

• One type of chemical

messenger is a hormone Only those cells that have specific receptors for a hormone can respond to that hormone. • Hormones work with nerves to communicate, coordinate, and integrate activities within the body of an animal. • Almost every invertebrate produces hormones physiology of invertebrate hormones is often quite different from that of vertebrate hormones. • The major endocrine glands of vertebrates include: • hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal, thymus, pancreas, and gonads. Various other tissues, however, such as the kidneys, heart, digestive system, and placenta also secrete hormones.

101Evolutionarily, new

messengers are uncommon.

• Instead, “old”

messengers are adapted to new purposes.

• For example, some

ancient protein hormones are in species ranging from bacteria to humanScientists suggest that

may initially have evolved in single-celled organisms to coordinate feeding or

• As multicellularity

evolved, more complex organs also evolved to govern the many individual coordination tasks, but control centers relied on the same kinds of messengers that were most animals commences with fertilization and the subsequent division of the zygote. • Further development then depends on continued cell proliferation, differentiation and growth.

Part I

• Integration communication, and coordination of all physiological processes, such as metabolism, respiration, excretion, movement, and reproduction, depend on chemical

Part I • The chemical messengers are the 104Biochemically the hormones may be the • i) Proteins (polypeptides) e.g. insulin • ii) Derivatives of amino acids (amines), e.g. TSH • iii) Steroids e.g. Sex hormones and adrenocortical hormones. Biochemistry of Hormones • iv) A few are fatty acid derivatives. For examplePostglndins • They are synthesized in the walls of blood vessels. • Regulate the contraction of smooth muscle tissue. • Involved in

105 General · of hormones are as · 108 Hormones modify the

involved.

mechanism.

• In this mechanism, an endocrine cell secretes a water-soluble hormone. • At the cells of the target organ, the hormone binds to a specific receptor site on the plasma membrane. • This forms a complex called hormone-receptor complex.