Nervous System

• Synapse is the point of contact between the terminal branches of the axon of a neuron with the dendrites of another neuron separated by a fine gap.
• Neuron is the structural and functional unit of the nervous system
• Cyton/cell body/perikaryon contains a well-defined nucleus and granular cytoplasm (Nissl's granules)
• Cyton has all cell organelles except the centrosome, so neurons lose the ability to divide
• Dendrites are the cytoplasmic projections of the cell body, conducting nerve impulses to the cyton
• Axon is a long process from the cyton or an elongated dendron, surrounded by two protective coverings: outer neurilemma and inner myelin sheath
• Myelin sheath shows gaps throughout its length called Nodes of Ranvier
• Some axons have side branches called collaterals
• Terminal portions of the axon, called axon endings, have swollen end-like bulbs that store a neurotransmitter called acetylcholine
• Synaptic clefts are the gaps between the axon terminals of one neuron and the dendrites of the next neuron
• Jumping of an impulse
• Stimulus is an agent or sudden change in the external or internal environment that results in a change in an organism or any of its body parts
• Response is the change in an organism or any of its body parts brought about because of a stimulus
• Impulse is a wave of irritability or electrical disturbance that sweeps over a nerve cell
• Receptors are nerve cells that, on receiving the stimulus, set up waves of impulses towards the central nervous system
• Effectors are muscles or glands that, on receiving the impulse from the central nervous system, contract or secrete substances
• SRIER: S - Stimulus, R - Receptors, I - Impulse, E - Effectors, R - Response
• Types of neurons

  Sensory neurons/afferent neurons

  Association/relay neurons

  Motor neurons/ efferent neurons
• Association neurons/relay neurons
• Motor neurons/efferent neurons
• Types of nerves
• Sensory nerves carry signals to the brain for touch, taste, smell, and sight
• Motor nerves carry signals to muscles or glands for movement and function
• Mixed nerves perform both sensory and motor functions
• Central nervous system (CNS) includes the brain and spinal cord
• Peripheral nervous system (PNS)
• Somatic nervous system
• Autonomic nervous system
• Sympathetic nervous system
• Parasympathetic nervous system
• 12 pairs of cranial nerves
• 31 pairs of spinal nerves
• Protective structures of the brain
• Meninges: Dura (tough) mater, Arachnoid, Pia (tender) mater
• Cerebrospinal fluid
• Main visible parts of the brain
• Cerebrum: the big brain with right and left cerebral hemispheres
• Cerebral hemispheres have 4 lobes: frontal, parietal, occipital, temporal
• Cerebrum contains grey matter (cell bodies) and white matter (axons/nerve fibers)
• Corpus callosum connects the two cerebral hemispheres