Biology Entrance Exam

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Identify the Parts of the Brain

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Structure and Function of the Brain

 Brain is the central part of the nervous system. The brain is protected inside the skull. It is covered by the meninges, a three-layered membrane. The cerebrospinal fluid is filled within the inner membranes of meninges and the ventricles of the brain. The cerebrospinal fluid formed from the blood is reabsorbed into the blood. The functions of the cerebrospinal fluid are to provide nutrients and oxygen to the tissues of the brain, regulate the pressure inside the brain and to protect the brain from injuries. 
Structure and Function of the Brain


A. Cerebrum

• the largest part of the brain. 

• numerous fissures and folds are seen. 

• The grey coloured outer part of cerebrum is called Cortex and the white coloured inner part is called Medulla.

 • centre of thought, intelligence, memory and imagination.

 • evokes sensations. 

• controls voluntary movements.

B. Cerebellum 

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• the second largest part of the brain

 • seen behind the cerebrum as two flaps.

• fissures and grooves are present. 

• coordinates muscular activities and maintains equilibrium of the body.

C. Medulla oblongata 

• the rod shaped medulla oblongata is seen below the cerebrum, located near the cerebellum.

 • controls involuntary actions like heart beat, breathing etc.

D. Thalamus

• situated below the cerebrum.

 • acts as relay station of impulses to and from the cerebrum. 

• analyses impulses from various parts of the body and sends the important ones to the cerebrum

E. Hypothalamus

• situated just below the thalamus.

 • plays a major role in the maintenance of homeostasis

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What is Synapse? Example of Neurotransmitters

What is Synapse

Synapse is the junction between two neurons or a neuron and a muscle cell or a neuron and a glandular cell. When electric impulses from the axon reach the synaptic knob, certain chemical substances are secreted from there to the synaptic cleft. These chemical substances are called neurotransmitters. They stimulate the adjacent dendrite or cell and new electric impulses are generated. Synapse helps to regulate the speed and direction of impulses.


 Example of neurotransmitters : Acetylcholine and Dopamine

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Structure and Function of Neuron

Neuron or nerve cell is the basic structural unit of the nervous system. Like all other cells, the neuron has a cell membrane, cytoplasm and nucleus.


Axon

 • Longest filament from the cell body. 

• Carries impulses from the cell body to outside.

Axonite 

• Branches of axon.

 • Carries impulses to the synaptic knob.

Dendrite 

• Branches of Dendron

. • Part that receives impulses from adjacent neuron.

Dendron 

• Short filament from the cell body. 

• Carries impulses from dendrites to the cell body.

Synaptic knob

 • Tip of axonite

. • Secretes neurotransmitter.

Schwann cell

 • Encircles the axon.

Axons of most of the neurons are repeatedly encircled by myelin, a membrane containing lipid. This is called myelin sheath.

 Nerve is a group of axons. Myelin sheath in the nerves is formed of Schwann cells. Myelin sheath in the brain and the spinal cord is formed of specialized cells called oligodendrocytes. The myelin sheath has a shiny white colour. The part of the brain and the spinal cord where myelinated nerve cells are present in abundance is called white matter and the part where non-myelinated nerves cells are present is called grey matter. 

The major functions of the myelin sheath are to provide nutrients and oxygen to the axon, accelerate impulses, act as an electric insulator and protect the axon from external shocks. 


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MCQ on Ecology and Environment

MCQ on Ecology and Environment
1. Increase in concentration of the toxicant at successive trophic level is known as
A. Biotransfomation
B. Biomagnification
C. Biogeochemical cycling 
D. Biodeterioration
Ans: B.Biomagnification
2.Which one of the following combination is wrong?
A.Rio convention – Air pollution
B. Kyoto Protocol – Climate Change
C.Montreal Protocol- Ozone Depletion
D. Ramsar convention-Wetland conservation
Ans: A.Rio convention – Air pollution
3. Example of secondary air pollutant is/ are
A. Smog
B. PAN
C. O3
D.All of these
Ans: D.All of these
4. Ionosphere is between  

A. Stratospere and mesosphere
B. Mesospere and thermosphere
C. Trophosphere and stratospere
D. Trospere and thermospere
Ans: B.Mesospere and thermosphere
5. Photochemical smog always contains
 A. O3
B. CO
C. PAN
D. All of these
Ans: A. O3
6. The polluting strength of sewage is usually characterized by
A. Eutrophication
B.Nitrogen content
C.Ozone content
D. BOD
Ans:D. BOD
7. The term ecosystem was coined by
 A. E. haeckel
B. E. Warming
C.E P Odum
D. AG Tansley
                                                                                                    Ans: D. AG Tansley
8.How many hotspot of biodiversity in the world have been identified till date by Norman Myers?
 A. 17
B. 34
C. 25
D. 43
                                                                                                                                                 Ans: B. 34 
9. What is the National aquatic animal of India?
A. Blue whale
B. Sea horse
C. Gangetic Shark
D. River Dolphin
                                                                                                       Ans: D. River Dolphin  
10. Depletion of which gas in the atmosphere can lead to an increased incidence of skin cancers?
 A. Ammonia
B. Ozone
C.Methane
D. Nitrous oxide
                                                                                                                  Ans: B. Ozone  
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