Most important topics of SSLC biology chapter 1 sensation and responses,10 topics are given below with explanation with pdf,video,notes,questions

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1.Neuron:structure and functions


  • Branches of Dendron
  • FUNCTION;Part that receives impulses from adjacent neuron.


  • Short filament from the cell body.
  • FUNCTION;Carries impulses from dendrites to the cell body.


  • Longest filament from the cell body.
  • FUNCTION;Carries impulses from the cell body to outside


  • Branches of axon.
  • FUNCTION; Carries impulses to the synaptic knob

Synaptic knob

  • Tip of axonite.
  • FUNCTION;Secretes neurotransmitter

2.Functions of myelin sheath

  • Provide nutrients and oxygen to the axon.
  • Accelerate impulses.
  • Act as an electric insulator.
  • Protects the axon from external shocks.

3.Generation and transmission of impulses

The outer surface of the plasma membrane of the neuron is positively charged and the inner surface is negatively charged. This is due to the difference in the distribution of certain ions.When stimulated, the distribution of ions in that particular part changes and hence the inner surface becomes positively charged and the outer surface becomes negatively charged .This momentary charge difference stimulates its adjacent parts and similar changes occur there too. As this process proceeds, impulses get transmitted as electric charges. Nerve impulses are messages transmitted through the neurons

4.Synapse and neurotransmitters

It is the junction between neurons or between neurons and muscles or glands is known as the synapse. It helps to regulate the speed and direction of impulses. The impulses are transmitted across the synaptic cleft only through a chemical (neurotransmitter), secreted from the synaptic knobs.

Neurotransmitters; Acetyl choline and Dopamine

Function; Synapse helps to regulate the speed and direction of impulses

5.Functions of CSF

  • It provides nutrients and oxygen to brain tissues.
  • Regulates the pressure inside the brain.
  • Protects brain from injuries

6.Brain and it’s parts especially cerebrum and cerebellum


The largest part of the brain with many fissures and folds are seen


  • centre of thought, intelligence, memory and imagination.
  • evokes sensations.
  • controls voluntary movements


The second largest part. seen behind the cerebrum as two flaps

Function;Coordinates muscular activities and maintains equilibrium of the body.

7 The pathway of impulses in reflex action

recepter-sensory neuron-inter neuron-brain-motor neuron-related muscle

8.Reflex arc

Reflex arc is the pathway of impulses in the reflex action. Mainly spinal cord acts as the centre of reflex action and such reflexes are called spinal reflexes

9.Sympsthetic and parasympathetic system

10.Diseases affecting nervous system

Alzheimer’s disease

cause;Accumulation of an insoluble protein in the neural tissues of the
brain. Neurons get destroyed.

symptoms;Loss of memory, inability to recognize friends and relatives, inability to do routine works.

Parkinsons disease

cause;Destruction of specialised ganglions in the brain. Production of dopamine, a neurotransmitter in the brain gets reduced

symptoms;Loss of body balance, irregular movement of muscles, shivering of the body, profuse salivation


cause;Continuous and irregular flow of electric charges in the brain.

symptoms;Epilepsy due to continuous muscular contraction, frothy discharge from the mouth,clenching of the teeth following which the patient falls unconscious.


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