MBLEx Nervous System

Structural Divisions of the Central and Peripheral Nervous Systems

  • Central Nervous System (CNS):

    • Consists of the brain and the spinal cord.

    • Brain: Located inside the cranium.

    • Spinal Cord: Located inside the vertebral canal of the spine.

    • Meninges: Three protective layers of connective tissue surrounding the brain and spinal cord:

    • Pia mater: The inner protective layer.

    • Arachnoid mater: The middle protective layer.

    • Dura mater: The outer protective layer.

    • Cerebrospinal Fluid (CSF): A clear fluid that surrounds the brain and spinal cord.

  • Peripheral Nervous System (PNS):

    • Consists of all nerves that connect the Central Nervous System (CNS) to the rest of the body.

Functional Divisions of the Nervous System

  • Autonomic Nervous System (ANS):

    • Core Function: Helps regulate homeostasis and controls involuntary responses involving internal organs, glands, and smooth muscle.

    • Volitional Control: Most ANS responses cannot be consciously controlled, with the exception of breathing.

    • Functional Divisions:

    • Sympathetic Nervous System:

      • Known as "Fight or Flight".

      • Activated during times of stress or danger.

      • Physiological effects: Increased heart rate, increased respiration, and increased blood pressure.

    • Parasympathetic Nervous System:

      • Known as "Rest + Digest".

      • Activated during relaxation to calm the body.

      • Physiological effects: Decreased heart rate, decreased respiration, and increased blood flow to the digestion system to increase peristalsis.

  • Somatic Nervous System:

    • Core Function: Regulates voluntary responses associated with skeletal muscles and joints.

    • Sensory Receptors Integration: Contains receptors for vision, hearing, taste, smell, and touch.

    • Volitional Control: Mostly voluntary in nature, with the exception of reflexes.

Classification and Structural Types of Nerves

  • Directional Signal Transmission:

    • Afferent (Sensory) Nerves: Transmit sensory information toward the Central Nervous System (CNS).

    • Efferent Nerves: Carry signals away from the CNS out to muscles and glands.

    • Mixed Nerves: Contain both afferent and efferent fibers.

  • Anatomical Origin and Nerve Counts:

    • Cranial Nerves: 12 pairs of nerves that arise directly from the brain.

    • Spinal Nerves: 31 pairs of nerves that arise directly from the spinal cord.

    • All 31 pairs of spinal nerves are categorized as mixed nerves.

Peripheral Nerve Plexuses and Specific Innervations

  • Cervical Plexus:

    • Location: Located in the neck.

    • Innervation: Supplies the neck and diaphragm muscles.

    • Specific Nerve: Phrenic Nerve — controls the diaphragm.

  • Brachial Plexus:

    • Location: Located in the shoulder and axilla.

    • Target: Controls the upper limbs.

    • Specific Nerves (5 total):

    • Radial Nerve: Located in the posterior arm and forearm; extends the elbow, wrist, and fingers.

    • Musculocutaneous Nerve: Located in the anterior arm; controls movement and feeling in the upper arm and forearm.

    • Axillary Nerve: Located in the armpit; controls movement and feeling in the shoulder (specifically targeting the deltoid and teres minor muscles).

    • Median Nerve: Located in the armpit and hand; controls movement and feeling to most forearm and hand muscles.

    • Ulnar Nerve: Also known as the "Funny Bone"; controls movement in the forearm and most small hand muscles; provides feeling to the pinky finger and half of the ring finger.

  • Lumbosacral Plexus:

    • Sciatic Nerve: The largest and longest nerve in the human body; controls movement and feeling in the lower body.

    • Femoral Nerve: Controls motor function in the front of the thigh and sensation in the front and inner leg.

    • Obturator Nerve: Controls movement and feeling in the inner thigh.

    • Tibial Nerve: Controls movement and feeling for the back of the lower leg and the bottom of the foot.

    • Common Peroneal Nerve: Controls movement in the lower leg and provides feeling to the outer leg and top of the foot.

    • Deep Peroneal Nerve: Lifts the foot upward, extends the toes, and provides feeling to the skin in the small web between the big toe and second toe.

    • Superficial Peroneal Nerve: Controls movement and feeling in the outer lower leg and top of the foot.

Sensory Receptors

  • Mechanoreceptors: Respond to changes in pressure and vibrations; found in the skin and body.

  • Thermoreceptors: Detect changes in temperature; located in the mouth and skin.

  • Photoreceptors: Detect changes in light; located in the retina.

  • Chemoreceptors: Detect sense of taste and smell; some detect changes in blood chemistry.

  • Nociceptors: Sense pain and damage.

  • Proprioceptors: Detect changes in muscle length.

Reflexes and Reflex Arc Mechanics

  • Autonomic Reflexes:

    • Function: Control internal organs and autonomic functions.

    • Example: Pupils getting smaller when exposed to sunlight.

  • Somatic Reflexes:

    • Function: Control skeletal muscles and body movement.

    • Example: Pulling away from pain.

  • Reflex Arc Pathway:

    • Stimulus / Pain Input: Pain or sensory stimulus creates sensory info.

    • Afferent Transmission: Afferent nerves transmit sensory info toward the CNS (Brain).

    • CNS Processing: Central Nervous System receives and processes the input.

    • Efferent Transmission: Efferent nerves transmit info away from the CNS to the target muscle to elicit a response.

Effects of Massage on the Nervous System

  • Promotes overall body relaxation.

  • Increases parasympathetic nervous activity while decreasing sympathetic nervous activity.

  • Reduces stress and anxiety.

  • Decreases pain perception.

  • Improves body awareness.