The Peripheral Nervous System

The peripheral nervous system (PNS) is the division of the nervous system which contains all nerves which can be found outside of the central nervous system (CNS). Its role is to connect the central nervous system to the organs, muscles and glands found throughout the body.

peripheral nervous system
Retrieved from https://strongfitlibrary.com/knowledge-base/peripheral-nervous-system/ on 12th November 2021

Peripheral Nervous System Tissues

The peripheral nervous system is made up of the following tissues:

  • NERVES – bundles of axons that make up most of the peripheral nervous system tissues. They are classified as sensory, motor, or mixed.
  • GANGLIA – nervous tissues which act as relay stations for signals which are transmitted through nerves of the peripheral nervous system.
peripheral nervous system
Retrieved from http://scscvcepsychology34.weebly.com/divisions-of-the-pns.html on 12th November 2021

The Somatic Nervous System

The somatic nervous system has the ability to sense the external environment and control voluntary movements through signals originating within the cerebral cortex of the brain. In other words, perceptions of the outside world and responses to these perceptions result from the somatic nervous system.

The somatic nervous system consists of:

  • 12 pairs of cranial nerves
  • 31 pairs of spinal nerves

Out of 12 pairs of cranial nerves, 4 participate in both sensory and motor functions as mixed nerves, since they have both sensory and motor neurons.

Cranial Nerves

Cranial nerves, which connect directly to the brain, can be found in the head and neck. Sensory Cranial Nerves sense smells, tastes, light, sounds, and body position. Motor Cranial Nerves have the ability to control muscles of the face, tongue, eyeballs, throat, head, and shoulders, as well as swallowing and salivary glands.

cranial nerves
Retrieved from https://nurseszone.in/nurseszone/40-tips-and-mnemonics-in-remembering-the-12-cranial-nerves/43.html on 12th November 2021
cranial nerves
Retrieved from https://brain.oit.duke.edu/lab04/lab04.html on 12th November 2021

Spinal Nerves

spinal nerves
Retrieved from https://socratic.org/questions/what-are-spinal-nerves on 12th November 2021

Somatic VS Autonomic Nervous System

peripheral nervous system
Retrieved from https://www.pinterest.com.mx/pin/289356344804607523/ on 12th November 2021

Somatic Nervous System

Autonomic Nervous System

The Autonomic Nervous System (ANS) operates without conscious control via reflex arcs in the same way as the Somatic Nervous System. Autonomic sensory neurons can be found in the visceral organs and blood vessels. They trigger continuous nerve impulses that reach the integrating centres in the central nervous system. Impulses within the autonomic motor neurons are then transferred to smooth muscle, cardiac muscle, or glands. Reflexes triggered by the ANS are controlled by centres in the hypothalamus and the brainstem.

AUTONOMIC = AUTOMATIC: NOT CONTROLLABLE

peripheral nervous system
Retrieved from https://slideplayer.com/slide/3720951/ on 12th November 2021

Sympathetic VS Parasympathetic Nervous System

peripheral nervous system
Retrieved from https://americanaddictioncenters.org/health-complications-addiction/nervous-system on 12th November 2021

Condition: Trigeminal Neuralgia


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Nervous System Introduction For Nursing Students

The nervous system is the body’s control centre and communications network – it is the main controlling, regulatory and communicating system within the body. It is responsible for all mental activity, including thought, learning and memory.

The nervous system works in conjunction with the endocrine system to regulate and maintain homeostasis by picking up information about the external and internal environment through its receptors.

The 3 Functions of the Human Nervous System

  1. SENSORY – senses changes within the body as well as within the outside environment
  2. INTEGRATIVE – is able to interpret and understand changes
  3. MOTOR – provides a responsive action to its interpretation of sensed changes through muscular contractions or glandular secretions
nervous system
Retrieved from https://www.austincc.edu/apreview/PhysText/CNS.html on 29th October 2021

The 2 Principal Divisions Emerging From The Nervous System

nervous system
Retrieved from https://ib.bioninja.com.au/options/option-a-neurobiology-and/a2-the-human-brain/autonomic-control.html on 29th October 2021

The Central Nervous System

  • Consists of the brain and the spinal cord
  • Controls the entire nervous system
  • Responsible for thoughts, emotions and memories
  • Integrates and correlates all kinds of incoming sensory information thanks to receptors that relay the information
  • Triggers nerve impulses to stimulate muscle contractions and gland secretions
Retrieved from https://faculty.etsu.edu/forsman/CentralNervousSystemCompleteDiagram.htm on 29th October 2021

The Peripheral Nervous System

  • Made up of various nerve processes which connect the brain and spinal cord through receptors, muscles and glands
  • Divides into the Afferent System (nerve cells ‘afferent neurones’ that convey information from peripheral receptors to the CNS) and the Efferent System (nerve cells ‘efferent neurones’ that convey information from the CNS to muscles and glands)
  • The Efferent System subdivides into the Somatic Nervous System (voluntary effect by efferent neurones conducting impulses from the CNS to the skeletal muscle tissue) and the Autonomic Nervous System (involuntary effect by efferent neurones conveying impulses from the CNS to smooth muscle tissue, cardiac muscle tissue and glands)
nervous system
Retrieved from https://en.wikipedia.org/wiki/Central_nervous_system on 30th October 2021

Nervous Tissue Histology

Nervous tissue consists of 2 types of cells:

NEURONS:

  • Contain well developed excitability and conductivity properties that have the ability to respond to adequate stimulus by initiating an action potential that reaches to the cell’s other end, relaying the action potential to another
  • Responsible for the receiving and transmitting of nerve impulses such as sensing, thinking, remembering, controlling muscle activity, and regulating glandular secretions
  • Is made up of 3 parts, namely the CELL BODY, which contains a nucleus surrounded by cytoplasm with all organelles and nissl bodies; DENDRITES, responsible for receiving or input; and the AXON, which propagates nerve impulses towards another neuron, muscle fibre or gland cell
nervous system
Retrieved from https://www.sciencefacts.net/parts-of-a-neuron.html on 30th October 2021
Neuron Types

BIPOLAR NEURON (a.k.a. Interneuron)

  • One main dendrite
  • One axon
  • Commonly found in the retina of the eye, the inner ear and the brain’s olfactory area

UNIPOLAR NEURON (a.k.a. Sensory Neuron)

  • Begins in the embryo as bipolar neurons
  • Dendrites extend into the periphery from the axon
  • Axon branch extending into the CNS ends in synaptic end bulbs

MULTIPOLAR NEURON (a.k.a. Motor Neuron)

  • Several dendrites
  • One axon
  • Commonly found in the brain and the spinal cord
Retrieved from https://www.researchgate.net/figure/Basic-Neuron-types-Most-neurons-are-collected-into-packages-of-one-sort-or-another_fig4_293333043 on 30th October 2021

NEUROGLIA:

  • Smaller in size than neurons
  • Constitute half the CNS volume
  • Do not generate or propagate action potentials
  • Have the ability to multiply and divide within the mature nervous system
  • Support, nourish and protect neurons
  • Maintain homeostasis in the interstitial fluid that surrounds the neurons

Nervous System Cell Types

Retrieved from https://www.pinterest.com/pin/545357836125394127/ on 30th October 2021

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