MEDICINE AND SURGERY
HUMAN PSHYCOLOGY 6
QUESTION 1
DESCRIBE THE ORGANIZATION OF THE NERVOUS SYSTEM
The nervous system consists of two parts::
1.The central nervous system (CNS) consists of the brain and spinal cord.
2.The peripheral nervous system (PNS) consists of nerves outside the CNS.
, PERIPHERAL NERVOUS SYSTEM
Nerves of the PNS are classified in three ways.
First, PNS nerves are classified by how they are connected to the CNS. Cranial nerves originate from or
terminate in the brain, while spinal nerves originate from or terminate at the spinal cord.
Second, nerves of the PNS are classified by the direction of nerve propagation. Sensory ( afferent)
neurons transmit impulses from skin and other sensory organs or from various places within the body to
the CNS. Motor ( efferent) neurons transmit impulses from the CNS to effectors (muscles or glands).
Third, motor neurons are further classified according to the effectors they target. The somatic nervous
system (SNS) directs the contraction of skeletal muscles. The autonomic nervous system (ANS) controls
the activities of organs, glands, and various involuntary muscles, such as cardiac and smooth muscles.
The autonomic nervous system has two divisions:
The sympathetic nervous system is involved in the stimulation of activities that prepare the body for
action, such as increasing the heart rate, increasing the release of sugar from the liver into the blood,
and other activities generally considered as fight‐or‐flight responses (responses that serve to fight off or
retreat from danger).
The parasympathetic nervous system activates tranquil functions, such as stimulating the secretion of
saliva or digestive enzymes into the stomach and small intestine.
Generally, both sympathetic and parasympathetic systems target the same organs, but often work
antagonistically. For example, the sympathetic system accelerates the heartbeat, while the
parasympathetic system slows the heartbeat. Each system is stimulated as is appropriate to maintain
homeostasis.
CENTRAL NERVOUS SYSTEM
The CNS includes the brain and spinal cord along with various centers that integrate all the sensory and
motor information in the body. These centers can be broadly subdivided into lower centers, including
the spinal cord and brain stem, that carry out essential body and organ-control functions and higher
centers within the brain that control more sophisticated information processing, including our thoughts
and perceptions.
HUMAN PSHYCOLOGY 6
QUESTION 1
DESCRIBE THE ORGANIZATION OF THE NERVOUS SYSTEM
The nervous system consists of two parts::
1.The central nervous system (CNS) consists of the brain and spinal cord.
2.The peripheral nervous system (PNS) consists of nerves outside the CNS.
, PERIPHERAL NERVOUS SYSTEM
Nerves of the PNS are classified in three ways.
First, PNS nerves are classified by how they are connected to the CNS. Cranial nerves originate from or
terminate in the brain, while spinal nerves originate from or terminate at the spinal cord.
Second, nerves of the PNS are classified by the direction of nerve propagation. Sensory ( afferent)
neurons transmit impulses from skin and other sensory organs or from various places within the body to
the CNS. Motor ( efferent) neurons transmit impulses from the CNS to effectors (muscles or glands).
Third, motor neurons are further classified according to the effectors they target. The somatic nervous
system (SNS) directs the contraction of skeletal muscles. The autonomic nervous system (ANS) controls
the activities of organs, glands, and various involuntary muscles, such as cardiac and smooth muscles.
The autonomic nervous system has two divisions:
The sympathetic nervous system is involved in the stimulation of activities that prepare the body for
action, such as increasing the heart rate, increasing the release of sugar from the liver into the blood,
and other activities generally considered as fight‐or‐flight responses (responses that serve to fight off or
retreat from danger).
The parasympathetic nervous system activates tranquil functions, such as stimulating the secretion of
saliva or digestive enzymes into the stomach and small intestine.
Generally, both sympathetic and parasympathetic systems target the same organs, but often work
antagonistically. For example, the sympathetic system accelerates the heartbeat, while the
parasympathetic system slows the heartbeat. Each system is stimulated as is appropriate to maintain
homeostasis.
CENTRAL NERVOUS SYSTEM
The CNS includes the brain and spinal cord along with various centers that integrate all the sensory and
motor information in the body. These centers can be broadly subdivided into lower centers, including
the spinal cord and brain stem, that carry out essential body and organ-control functions and higher
centers within the brain that control more sophisticated information processing, including our thoughts
and perceptions.
