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Nervous system (HAP:- 2):- Hand written notes


Describe the organization of the nervous system including the central
nervous system and the peripheral nervous system
• Distinguish among the three types of neurons: afferent neurons, ef-
ferent neurons, and interneurons
• List the three major levels of CNS function and describe their activ-
• Distinguish among the three types of tracts in the CNS: projection
tracts, association tracts, and commissural tracts
• Describe the activity of each of the functional areas of the cerebral
• Explain how language is processed in the cerebral cortex
• Describe the functions of the basal ganglia, thalamus, hypothalamus,
and brainstem
• Distinguish among the three regions of the cerebellum and their
• Compare and contrast the exchange of materials between the blood
and peripheral tissues with that of the blood and brain
• Explain the functions of the blood–brain barrier
• Explain the functions of cerebrospinal fluid

The nervous system is one of the two regulatory systems in the human body
that influences the activity of all the other organ systems. It consists of
literally billions of neurons interconnected in a highly organized manner to
form circuits. The number of neurons and the manner in which they are
interconnected in a given circuit distinguishes one region of the brain from
another and the brain of one individual from that of another. In addition,
plasticity, the ability to alter circuit connections and function in response to
Nervous system:
Organization of nervous system, neuron, neuroglia, classification and
properties of nerve fibre, electrophysiology, action potential, nerve
impulse, receptors, synapse, neurotransmitters
Central nervous system: Meninges, ventricles of brain and cerebrospinal
fluid.structure and functions of brain (cerebrum, brain stem, cerebellum),
spinal cord (gross structure, functions of afferent and efferent nerve
tracts,reflex activity)

sensory input and experiences adds further complexity and distinctiveness
to neurological responses and behavior. The nervous system is divided into
two anatomically distinct regions:
• Central nervous system
• Peripheral nervous system
The central nervous system (CNS) consists of the brain and spinal cord.
The peripheral nervous system (PNS) consists of 12 pairs of cranial nerves that
arise from the brainstem and 31 pairs of spinal nerves arising from the spinal
cord. These peripheral nerves carry information between the CNS and the
tissues of the body. The PNS consists of two divisions:
• Afferent division
• Efferent division
The afferent division carries sensory information toward the CNS and the
efferent division carries motor information away from the CNS toward the
effector tissues (muscles and glands). The efferent division is further divided
into two components: (1) the somatic nervous system, which consists of
motor neurons that innervate skeletal muscle; and (2) the autonomic nervous
system that innervates cardiac muscle, smooth muscle, and glands.
6.2 Classes of neurons
The human nervous system has three functional classes of neurons:
• Afferent neurons
• Efferent neurons
• Interneurons
Afferent neurons lie predominantly in the PNS (see Figure 6.1). Each has
a sensory receptor activated by a particular type of stimulus, a cell body
located adjacent to the spinal cord, and an axon. The peripheral axon extends
from the receptor to the cell body and the central axon continues from the
cell body into the spinal cord. Efferent neurons also lie predominantly in the
PNS. In this case, the cell bodies are found in the CNS in the spinal cord or
brainstem and the axons extend out into the periphery of the body where
they innervate the effector tissues. By way of convergence, the centrally
located cell bodies may receive inputs from several different regions of the
brain that will influence their activity.
The third class of neurons includes the interneurons, which lie entirely
within the CNS. Because the human brain and spinal cord contain well over
100 billion neurons, interneurons account for approximately 99% of all the
neurons in the body taken together. Interneurons lie between afferent and