The-Peripheral-Nervous-System

The Peripheral Nervous System

Overview

  • The peripheral nervous system (PNS) consists of all the nerves located outside the central nervous system (CNS).

  • Function:

    • Connects the CNS to limbs, organs, and skin.

    • Enables the brain and spinal cord to receive and send information to other body areas, allowing reactions to the environment.

Components

Central Nervous System vs. Peripheral Nervous System

  • Central Nervous System (CNS) Includes:

    • Brain

    • Spinal cord

    • Relay neurons (interneurons)

  • Peripheral Nervous System (PNS) Includes:

    • Cranial nerves

    • Spinal nerves

    • Peripheral nerves

    • Contains sensory neurons and motor neurons.

Functions of the Peripheral Nervous System

  • Connects the CNS.

  • Carries sensory and motor information to and from various body parts.

  • Regulates involuntary functions like heartbeat and breathing.

Autonomic Nervous System

  • Part of the PNS regulating involuntary body functions such as:

    • Blood flow

    • Heartbeat

    • Digestion

    • Breathing

Parts of the Autonomic Nervous System

  • Parasympathetic System:

    • Maintains normal body functions and conserves resources.

    • Slows heart rate, breathing, and constricts pupils post-threat.

  • Sympathetic System:

    • Prepares body to expend energy in response to stress (fight-or-flight).

    • Accelerates heart rate, increases breathing, boosts blood flow to muscles, activates sweat, dilates pupils.

Autonomic Nerve Pathways

  • Connect different organs to the brain stem or spinal cord.

  • Key Neurotransmitters:

    • Acetylcholine:

      • Inhibitory effect in the parasympathetic system.

    • Norepinephrine:

      • Stimulating effect in the sympathetic system.

Dysautonomia - Disorder of the ANS

  • Symptoms May Include:

    • Difficulty in bladder emptying

    • Aches and pains

    • Dizziness upon standing

    • Erectile dysfunction

    • Faintness or fainting spells

    • Fatigue

    • Gastrointestinal symptoms

    • Hypotension (low blood pressure)

    • Lack of pupillary response

Functions of the Sympathetic and Parasympathetic Neurons

  • Organ Functions:

    • Salivary Gland:

      • Sympathetic: Decreases secretion; Parasympathetic: Increases secretion.

    • Heart:

      • Sympathetic: Increases heart rate; Parasympathetic: Decreases heart rate.

    • Blood Vessels:

      • Sympathetic: Constricts; Parasympathetic: Dilates in some organs.

    • Pupil Response:

      • Sympathetic: Dilates pupil; Parasympathetic: Constricts pupil.

    • Stomach/Intestine:

      • Sympathetic: No effect; Parasympathetic: Stimulates secretion.

    • Lungs:

      • Sympathetic: Dilates bronchioles; Parasympathetic: Constricts bronchioles.

Somatic Nervous System

Cranial Nerves

  1. Olfactory Nerve:

    • Transmits smell sensations.

  2. Optic Nerve:

    • Involved in vision.

  3. Oculomotor Nerve:

    • Controls eye muscle function and pupil response.

  4. Trochlear Nerve:

    • Controls downward, outward, and inward eye movement.

  5. Trigeminal Nerve:

    • Largest cranial nerve; has sensory and motor functions.

    • Divisions:

      • Ophthalmic: Sensory from upper face.

      • Maxillary: Sensory from middle face.

      • Mandibular: Sensory and motor functions for lower face.

  6. Abducens Nerve:

    • Controls lateral eye movement.

  7. Facial Nerve:

    • Controls facial expression muscles; taste sensation from tongue.

  8. Vestibulocochlear Nerve:

    • Involved in hearing and balance.

    • Components:

      • Cochlear portion: Sound detection.

      • Vestibular portion: Tracking head movements.

  9. Glossopharyngeal Nerve:

    • Functions in taste and throat muscle movement.

  10. Vagus Nerve:

  • Sensory/motor functions from ear to abdomen; longest cranial nerve.

  1. Accessory Nerve:

  • Controls neck muscles.

  1. Hypoglossal Nerve:

  • Controls tongue movements.

Cerebral Arteries (Circle of Willis)

Overview

  • The Circle of Willis is a component of cerebral circulation, comprising:

    • Anterior cerebral arteries (left and right)

    • Anterior communicating artery

    • Internal carotid arteries (left and right)

    • Posterior cerebral arteries (left and right)

    • Posterior communicating arteries (left and right)

References

  • Pinel, J. P. (2004). Biological Psychology, Allyn Bacon, USA.

  • Santiago, M., Della, C. & Lajom, J.A. (2008). Activity Manual in Biological Psychology, C&E Publishing, Manila, Philippines.