Control and Coordination Test 26

Homeostasis is the maintenance of constant internal environment.
Adrenaline is an emergency hormone. It increases pulse rate, blood pressure during emergency and stimulates the breaking of liver glycogen into blood glucose.
Thyroxine is useful in metabolism. Insulin is secreted from thyroid gland. It regulates general growth and development and controls carbohydrate, lipid and protein metabolism.
Peptide hormones such as insulin, affect the properties of plasma membrane.
Insulin is secreted in pancreatic islets. It controls carbohydrate metabolism and maintains glucose level in the blood.
Sanger represents the structure of insulin.

Nissl granule is a large granular body found in neurons. It consists of rough endoplasmic reticulum and clusters of free ribosomes and are a site of protein synthesis. It was named after Franz Nissl, a German psychiatrist, who invented the Nissl staining method.
Thus, the correct answer is option (D), 'Ribosomes'.

The liver is divided into a large right lobe and a smaller left lobe and is completely covered by a tough fibrous sheath, Glisson's capsule. Kupffer cells are reticuloendothelial cells, which are present in the lining of the sinusoids, act to filter out and destroy bacteria present in the blood stream.
Clara cells are dome-shaped cells, with short microvilli found in the bronchioles of the lungs. Dust cell or an alveolar macrophage cell is a type of macrophage found in the pulmonary alveolus.
A neuron is an electrically excitable cell, that processes and transmits information through electrical and chemical signal present in the brain. An astrocyte is characteristic star-shaped cells present in the brain and spinal cord.
Thus, the correct answer is option D.

• The stimulus stimulates the pain receptors of the skin, which initiate an impulse in a sensory neuron.
• This travels to the spinal cord, where it passes, by means of a synapse, to a connecting neuron called the relay neuron situated in the spinal cord.
• The relay neuron, in turn, makes a synapse with one or more motor neurons that transmit the impulse to the muscles to initiate a response.
• Reflexes do not require the involvement of the brain.
  
  Hence, the correct option is A.

Correct option D

Explanation for the correct option: 

• Afferent and efferent fibres transport the nerve impulse.
• Afferent neurons is also known as sensory or receptor neurons.
• Afferent neurons carry nerve impulses from receptors or sense organs toward the central nervous system.
• Efferent nerves is also known as motor or effector neurons which carry nerve impulses away from the central nervous system to effectors, such as muscles or glands.
  Hence the correct option (D) is correct.

The corpus callosum also callosal commissure is a wide commissure, a flat bundle of commissural fibers, about 10 cm long beneath the cerebral cortex in the brains of the placental mammals. The brain is divided into a right and left hemisphere, and the two halves are connected by the corpus callosum in the mammalian brain. Since in the list given elephant is the only mammal, the correct option is A.

• The dendrites accept signals generated by other neurons. These signals may be excitatory or inhibitory. All signals present at the dendrites of a neuron are combined and the result will determine whether or not that neuron will fire. If a neuron fires, an electrical impulse is generated. 
• An axon, or nerve fibre, is a long slender projection of a nerve cell or neuron, that conducts electrical impulses away from the neuron's cell body or soma. 
• Axon terminals have knob-like swellings at the very end called synaptic knobs. The function of a synaptic knob is to change the action potential that is carried by axons into a chemical message. 

The myelin sheath of a neuron consists of fat-containing cells that insulate the axon from electrical activity. This insulation helps to increase the rate of transmission of signals. Myelin is made up of inter-twining hydrocarbon chains of sphingomyelin, which serve to strengthen the myelin sheath. Hence it also provides mechanical support to the neuron.

The lower part of brain stem forms the hindbrain which comprises of the medulla oblongata, pons, and cerebellum. Cerebrum serves to receive sensory inputs, to bring about integration before commanding voluntary motor responses, to coordinate the activities of another part of the brain, and to carry out higher thought processes for learning, memory, language and speech. The cerebrum is part of the forebrain. Medulla oblongata consists of reflex centres that control heartbeat, blood vessel diameter, and rhythm of breathing as well as other vital and involuntary functions. Cerebellum serves to coordinate the voluntary movements of skeletal muscles as well as posture, balance, and equilibrium. Therefore, the correct answer is option C.