Overview of the Peripheral Nervous System

Summary

In this educational video, Dr. Mike explores the intricacies of the peripheral nervous system (PNS), distinguishing it from the central nervous system. He delves into the PNS's two main divisions: the autonomic nervous system, responsible for involuntary actions, and the somatic nervous system, which controls voluntary movements. The video also breaks down the 12 cranial nerves and their functions, as well as the spinal nerves categorized by regions of the spinal cord. Furthermore, Dr. Mike explains the sympathetic and parasympathetic subdivisions of the autonomic nervous system, detailing their roles in fight-or-flight responses and rest-and-digest states, respectively.

Takeaways

• 🧠 The peripheral nervous system (PNS) includes all nerves outside the brain, brainstem, and spinal cord, which are part of the central nervous system (CNS).
• 🔍 The PNS is divided into the autonomic nervous system (ANS), which controls involuntary functions, and the somatic nervous system, which controls voluntary movements.
• 🕊️ The ANS is further divided into the sympathetic (fight or flight) and parasympathetic (rest and digest) systems, which have opposite functions and are activated in response to different situations.
• 🧡 The sympathetic division is thoracolumbar, originating from the thoracic and lumbar regions of the spinal cord, and is associated with stress responses.
• 💚 The parasympathetic division is craniosacral, originating from the cranial nerves and sacral regions, promoting relaxation and digestion.
• 👀 Cranial nerves are paired and numbered with Roman numerals; there are 12 in total, each with specific sensory and/or motor functions.
• 🔑 A mnemonic to remember the names of the cranial nerves is 'ooo to touch and feel very good velvet are heaven', with the first letter of each word corresponding to the first letter of each nerve.
• 🔍 Some cranial nerves are purely sensory, some are purely motor, and some are both, allowing for the transmission of information to and from the brain.
• 🦴 Spinal nerves are categorized into cervical, thoracic, lumbar, sacral, and coccygeal, based on the regions of the spinal cord from which they emerge.
• 📈 The number of spinal nerve pairs corresponds to the divisions of the spinal cord: cervical (8 pairs), thoracic (12 pairs), lumbar (5 pairs), sacral (5 pairs), and coccygeal (1 pair).
• 📚 The autonomic nervous system's sympathetic and parasympathetic branches innervate various organs and structures to regulate bodily functions in response to stress or relaxation.

Q & A

What is the peripheral nervous system?

The peripheral nervous system is all the nervous tissue that is not part of the brain, brainstem, or spinal cord. It includes all the nerves that extend out from and return to the central nervous system.

What are the two functional subdivisions of the peripheral nervous system?

The two functional subdivisions of the peripheral nervous system are the autonomic nervous system, which controls involuntary functions, and the somatic nervous system, which controls voluntary movements and sensations.

What is the autonomic nervous system responsible for?

The autonomic nervous system is responsible for controlling involuntary actions such as sensory information from organs, heart contractions, smooth muscle movements in the gastrointestinal tract, blood vessels, and genitourinary tract, and the release of hormones from glands.

What is the somatic nervous system responsible for?

The somatic nervous system is responsible for conscious control of the body, including sensory input from the periphery and motor output to skeletal muscles, allowing for voluntary movements like walking, talking, singing, dancing, and other physical activities.

How many cranial nerves are there and what are they called?

There are 12 paired cranial nerves. They are named Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Pharyngeal (Vagus), Accessory, and Hypoglossal.

What is a mnemonic to remember the names of the cranial nerves?

A mnemonic to remember the names of the cranial nerves is 'Oh Oh Oh To Touch And Feel Very Good Velvet Are Heaven', with the first letter of each word representing the first letter of each cranial nerve name.

What is the difference between sensory and motor nerves in the context of cranial nerves?

Sensory nerves bring information about the environment into the brain, while motor nerves send information out from the brain to cause movement or other actions. Some cranial nerves are both sensory and motor, performing both functions.

Which cranial nerves are part of the parasympathetic division of the autonomic nervous system?

The parasympathetic division of the autonomic nervous system includes cranial nerves III (Oculomotor), VII (Facial), IX (Glossopharyngeal), and X (Vagus).

What is the sympathetic division of the autonomic nervous system and where does it originate from?

The sympathetic division of the autonomic nervous system is responsible for the 'fight or flight' response and originates from the thoracic and lumbar regions of the spinal cord.

How does the sympathetic division differ from the parasympathetic division in terms of activation?

The sympathetic division is activated during times of stress, preparing the body for action by increasing heart rate, dilating pupils, and promoting other 'fight or flight' responses. In contrast, the parasympathetic division is activated during rest and digestion, promoting relaxation and digestion.

What is the structure of the spinal cord and how is it related to the spinal nerves?

The spinal cord is divided into cervical, thoracic, lumbar, sacral, and coccygeal regions, each giving rise to pairs of spinal nerves. The number of pairs in each region corresponds to the number of vertebrae in that region, with cervical nerves having eight pairs, thoracic twelve pairs, lumbar five pairs, sacral five pairs, and coccygeal one pair.