Anatomy of The PNS

Reminders

Upcoming Assessments

  • Wednesday: Quiz #1

  • Next Monday: Exam #1 covering Chapters 1 and 2.

Content to Review

  • What is Neuroscience (beginning at slide 10)

  • History of Neuroscience

  • Anatomy of the CNS (Central Nervous System)

  • Anatomy of the PNS (Peripheral Nervous System) & Overview of Blood Flow

  • Ventricles, Meninges, & CSF (Cerebrospinal Fluid)

Anatomy of the Peripheral Nervous System & Overview of Blood Flow

Somatic and Autonomic Divisions of the PNS

Overview of the Nervous System

  1. Central Nervous System (CNS)

  2. Peripheral Nervous System (PNS)

    • Somatic Nervous System

    • Autonomic Nervous System

      • Sympathetic Division

      • Parasympathetic Division

    • Sensory (Afferent) Nervous System

    • Motor (Efferent) Nervous System

    • Enteric Nervous System

The Somatic Nervous System

Functions

  • Control of Voluntary Muscles

Components

  • Sensory Input:

    • Somatic sensory neurons, which include receptors from skin, skeletal muscles, joints, and special senses.

  • Motor Output (Direct):

    • Somatic motor neurons that innervate skeletal muscles directly.

Anatomical Pathway

  • Somatic sensory neuron connects via the posterior root to the skin.

  • The anterior root connects somatic motor neurons to the skeletal muscle.

Autonomic Nervous System (ANS)

Functions

  • Regulates Internal Environments: Manages the body’s internal state.

  • Control of Involuntary Muscles and Glands: Functions automatically without conscious thought.

Subdivisions of the ANS

  1. Sympathetic Division:(Stress) Activates the 'fight or flight' response.

  2. Parasympathetic Division:(Peace) Manages rest and digestion processes.

Sympathetic Autonomic Nervous System Responses

  • Physiological Effects:

    • Dilates pupils

    • Inhibits salivation

    • Relaxes airways

    • Increases heart rate

    • Stimulates glucose production and release

    • Stimulates release of adrenaline

    • Inhibits digestion

    • Inhibits voiding of bladder

    • Stimulates orgasm

Target Organs and Responses

  • Eyes:

    • Sympathetic Effect: Pupillary dilation

    • Parasympathetic Effect: Pupillary constriction (restinf)

  • Salivary glands:

    • Sympathetic: ↓ saliva production

    • Parasympathetic: ↑ saliva production and stimulates tear production

  • Heart:

    • Sympathetic: ↑ heart rate

    • Parasympathetic: ↓ heart rate

  • Respiratory system:

    • Sympathetic: Dilates bronchi

    • Parasympathetic: Constricts bronchi

  • Digestive system:

    • Stomach:

      • Sympathetic: ↓ activity

      • Parasympathetic: ↑ activity

    • Small intestine:

      • Sympathetic: ↓ motility

      • Parasympathetic: ↑ motility

    • Large intestine:

      • Sympathetic: ↓ motility

      • Parasympathetic: ↑ motility

  • Kidneys and bladder:

    • Sympathetic: Inhibits urination

    • Parasympathetic: Stimulates urination

  • Gonads & genitalia:

    • Sympathetic: Stimulates ejaculation

    • Parasympathetic: Stimulates erection

Enteric Nervous System

Description

  • Coordinates activities of the digestive tract, including organs such as:

    • Esophagus

    • Stomach

    • Intestines

Characteristics

  • Composed of approximately half a billion nerve cells.

  • Receives signals from both sympathetic and parasympathetic systems.

  • Connected to the CNS via a communication network known as the gut-brain axis.

  • vagus nerve = Plays a crucial role in transmitting signals to and from the brain, influencing various bodily functions including heart rate and digestion.

Cranial & Spinal Nerves

Overview

  • 31 Spinal Nerves

  • 12 Cranial Nerves:

    • Enter and exit directly from the brain, primarily innervating the face, head, and neck, with the exception of the vagus nerve which extends to the internal organs.

Cranial Nerve Functions and Descriptions

Cranial Nerve

Function

Description

CN I

Olfactory nerve

Sensory - Sense of smell

CN II

Optic nerve

Sensory - Sense of vision

CN III

Oculomotor nerve

Motor/Sensory - Controls extraocular muscles; constriction of pupils; lens shape change

CN IV

Trochlear nerve

Motor - Controls superior oblique muscle of the eye

CN V

Trigeminal nerve

Sensory/Motor - Tactile/pain from face/mouth and muscles for chewing

CN VI

Abducens nerve

Motor - Controls lateral rectus muscle of the eye

CN VII

Facial nerve

Sensory/Motor - Facial expressions; taste from anterior 2/3 of tongue

CN VIII

Vestibulocochlear nerve

Sensory - Auditory and vestibular information

CN IX

Glossopharyngeal nerve

Sensory/Motor - Taste from posterior 1/3 of tongue; muscle for swallowing

CN X

Vagus nerve

Sensory/Motor - Controls internal organs via parasympathetic activity

CN XI

Accessory nerve

Motor - Controls sternocleidomastoid and trapezius muscles of the neck and shoulders

CN XII

Hypoglossal nerve

Motor - Controls tongue muscles

Memorization Aids for Cranial Nerves

  • A mnemonic for recalling the order of cranial nerves is:

    • On - Olfactory

    • Old - Optic

    • Olympus - Oculomotor

    • Towering - Trochlear

    • Tops - Trigeminal

    • A - Abducens

    • Finn - Facial

    • And - (formerly Auditory: NOW Vestibulocochlear)

    • German - Glossopharyngeal

    • Viewed - Vagus

    • A - Accessory

    • Hop - Hypoglossal

  • “Oh Oh Oh To Touch And Feel Very Good Velvet AH”

  • for the Os (L, P, U)

  • for the Ts( tro- one, tri- three)

Peripheral Nervous System Terminology

Definitions

  • Nerves: Bundles of axons transmitting signals.

  • Ganglia: Clusters of neuronal cell bodies in the PNS.

  • Proximal: Closer in proximity to the center of the body.

  • Distal: Further away from the center of the body.

  • Contralateral: Referring to structures on opposite sides of the body.

  • Ipsilateral: Referring to structures on the same side of the body.

Brain Circulation & Cerebral Blood Flow

Functions

  • Nutrient Supply: Provides essential nutrients and energy to the brain.

  • Waste Removal: Carries away metabolic waste products.

Arteries Involved

  • Blood flow from the aorta to the brain is primarily facilitated through:

    • Cerebral arteries

    • Basilar artery

    • Carotid arteries

    • Vertebral arteries

    • Middle cerebral artery

    • Anterior cerebral artery

    • Posterior cerebral artery

The Circle of Willis

  • A key anatomical structure which represents the convergence of major cerebral arteries, allowing for collateral blood flow in case of blockage, consisting of:

    • Anterior communicating artery

    • Middle cerebral artery

    • Anterior cerebral artery

    • Posterior communicating artery

    • Posterior cerebral artery

    • Basilar artery

    • Vertebral artery

Problems with Blood Flow: Stroke

Overview

  • Stroke: The second leading cause of death worldwide.

    • Ischemic Stroke: 80% of stroke cases; occurs when blood flow to the brain is blocked.

    • Hemorrhagic Stroke: Accounts for 20% of stroke cases; arises from bleeding in or around the brain.

The Blood-Brain Barrier (BBB)

Definition

  • The BBB is an anatomical adaptation that selectively transports necessary substances for biological function, while also excluding potentially harmful materials.

  • Structure: Formed by endothelial cells and supported by astrocytes, physically encasing blood vessels in the brain.

Conclusion

These notes encapsulate integral parts of the nervous system and assess the organization and function of both the Central and Peripheral Nervous Systems along with critical aspects of cerebral circulation and health risks related to blood flow problems such as strokes and the importance of the Blood-Brain Barrier.