The skeletal muscle sends sensory information to the brain and receives motor impulses through the somatic nerves. The upper parts of the human body such as the head, eyes, ears, nose, mouth, neck, and other parts get their somatic nerve supply through cranial nerves. The thorax, abdomen, upper limb, lower limb, and various other organs in the middle and lower part of the body get somatic nerve supply through the spinal nerves.
The somatic nerve supply controls all the voluntary muscle movements. Stimuli from the precentral gyrus of the brain come down to the spinal cord through the corticospinal tract. It is then transmitted via the axons of motor neurons to the muscles of the body.
The somatic system also controls the process of a voluntary reflex arc. The reflex arc is a neural circuit between sensory input and specific motor output. It is a pathway followed by the nerves which carry sensory information just to the spinal cord and not to the brain. The spinal cord generates a response to effector organs which results in a much quicker reaction.
The sensory nerve supply or the afferent nerve supply of the organs carries sensory information to the central nervous system. The sensory nerves are all those nerves that can sense or recognize internal or external stimuli. The sensory nerves link different sensory neurons throughout the body. These nerves get information from the sensory receptors and enter the dorsal root ganglia of the spinal cord.
The information is then transferred to the brain. The muscles of the human body receive information through motor nerves. Motor nerves are also called efferent nerves because they carry information from the central nervous system to the effector muscles. Motor nerves are divided into three subtypes based on the type of motor neurons associated with them.
The motor nerves associated with alpha neurons target extrafusal muscles and are responsible for their contraction. The beta neurons innervate intrafusal fibers while the gamma motor neurons are not directly involved in any type of muscle contraction. The autonomic nerves are part of the autonomic nervous system which acts unconsciously and regulates body functions such as heart rate, respiratory rate, and digestion, etc.
Different organs of the body get their autonomic nerve supply through cranial and spinal nerves. The autonomic nerve supply is divided into sympathetic nerve supply, parasympathetic nerve supply, and enteric system. Most of the organs of the body are dually innervated by both sympathetic and parasympathetic nerves except adrenal medulla, sweat glands, arrector pili muscles, and most blood vessels which only get sympathetic nerve supply.
The sympathetic nerves arise from the thoracolumbar region of the spinal cord starting from the first thoracic vertebra to the second or third lumbar vertebra. They arise in the lateral grey column of the spinal cord. The sympathetic nerve fibers leave the spinal cord and become a part of the sympathetic chain. The sympathetic chain extends from the upper neck to the coccyx.
It has pairs of ganglia which include 3 cervical ganglia, 11 thoracic ganglia, 4 lumber ganglia, and sacral ganglia. It decreases urinary output and promotes emission before ejaculation in Ductus Deferens. The parasympathetic nerve fibers arise from the brain in the form of some cranial nerves and also from the sacral region of the spinal cord.
The cranial parasympathetic nerves fibers come from the third, seventh, ninth, and tenth cranial nerves and synapse at four parasympathetic ganglia. These four ganglia are ciliary, pterygopalatine, otic, and submandibular. From these ganglia, the parasympathetic nerves reach their target tissues through trigeminal nerve branches.
In the sacral region, the axons of pelvic splanchnic nerves exit the vertebral column as S2-S4 spinal nerves. These parasympathetic nerve fibers innervate the urinary bladder, ureters, urinary sphincters, prostate gland, vagina, and penis.
The parasympathetic system works when the body is at rest and there is no danger. Skeletal muscle has striations across its cells caused by the arrangement of the contractile proteins actin and myosin. These muscle cells are relatively long and have multiple nuclei along the edge of the cell. Skeletal muscle is under voluntary, somatic nervous system control and is found in the muscles that move bones.
Figure 1 illustrates the histology of skeletal muscle. Cardiac muscle, shown in Figure 1, is found only in the heart. Like skeletal muscle, it has cross striations in its cells, but cardiac muscle has a single, centrally located nucleus. Cardiac muscle is not under voluntary control but can be influenced by the autonomic nervous system to speed up or slow down. An added feature to cardiac muscle cells is a line than extends along the end of the cell as it abuts the next cardiac cell in the row.
This line is called an intercalated disc: it assists in passing electrical impulse efficiently from one cell to the next and maintains the strong connection between neighboring cardiac cells.
Figure 1. Smooth muscle cells do not have striations, while skeletal muscle cells do. Cardiac muscle cells have striations, but, unlike the multinucleate skeletal cells, they have only one nucleus. Cardiac muscle tissue also has intercalated discs, specialized regions running along the plasma membrane that join adjacent cardiac muscle cells and assist in passing an electrical impulse from cell to cell. Occasionally ingested food particles such as fish bone may get impacted in the fossa.
If care is not taken while removing the foreign particle, internal laryngeal nerve may be injured causing loss of sensations from the supraglottic part of larynx which leads to loss of protective cough reflex.
Touching soft palate or posterior third of tongue results in:. It prevents something from entering pharynx except as part of normal swallowing. Glossopharyngeal nerve carries the afferent fibers for the reflex and Vagus nerve carries the efferent fibers. Good day How do I access the rest of the information on short and long questions, diagrams, anatomical basis.
I am unable to access it. Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. Contents 1 What is the Extent of Pharynx? What are its subdivisions?
Adenoids Hypertrophy of pharyngeal tonsil is called adenoids.
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