Central Nervous System Recording (W2025)

Clinical Case Overview

• Patient Background

  • Mister W: Diabetic for 10 years

  • Complaints: Pain and numbness in feet

• Physical Observation

  • Weakness in muscles responsible for dorsiflexion of the foot

  • Affected nerves originate from the lumbar and sacral plexus (lumbosacral plexus)

Neurological Assessment

• Sensory Response

  • Physician pricked Mister W's foot with a needle

  • Result: No sensation suggesting an issue with the nerves transmitting impulses to the brain

  • Type of Neurons Involved:

    • Interneurons: Located within the spinal cord assisting in signal transmission

• Knee-Jerk Reflex

  • Action: Tapping below the knee to elicit a knee-jerk response

  • Terminology Used: This reaction is referred to as a reflex arc.

  • Neurons Involved:

    • Sensory neuron (receptor to spinal cord)

    • Interneuron (in spinal cord)

    • Motor neuron (exits spinal cord to effector)

  • Direction of Nerve Impulse: Impulse travels from the sensory receptor to the spinal cord, through interneurons, and back out to the motor neuron which activates the quadriceps muscle (effector).

Fight or Flight Response

• Scenario: Hearing unfamiliar sounds at home

• Physiological Changes Promoted by Sympathetic Nervous System:

  1. Increased Heart Rate: Enhances blood circulation.

  2. Increased Breathing: Often becomes rapid and shallow to supply more oxygen.

  3. Redistribution of Blood Flow: Blood supply shifts from non-essential organs (like the digestive system) to skeletal muscles in preparation for action.

  4. Pupil Dilation: Allows more light in for enhanced visibility.

  5. Slowed Digestion: Body prioritizes emergency responses over digestion.

Muscle Contractions Overview

• Types:

  • Isotonic Contractions: Muscles change length (either shortening or lengthening) while maintaining a constant tension.

  • Isometric Contractions: Muscles generate force without changing length, holding for a longer period.

  • Tetanic Contractions: Sustained muscle contractions where muscle fibers are stimulated at a high frequency, leading to a strong contraction over time.

Nervous System Structure

• Central Nervous System (CNS): Comprises the brain and spinal cord.

• Peripheral Nervous System: Includes all other nerves (cranial and spinal nerves).

• Neuroglia Types:

  • Astrocytes: Form the blood-brain barrier and regulate ion concentrations in the brain.

  • Microglia: Act as immune cells in the CNS, clearing out cellular debris.

  • Oligodendrocytes: Produce myelin sheaths for insulation around axons in the CNS.

  • Ependymal Cells: Produce cerebrospinal fluid (CSF).

Brain Anatomy

• Major Parts:

  • Brain Stem: Controls autonomic functions (breathing, heartbeat).

  • Cerebellum: Coordinates fine motor movements and balance.

  • Diencephalon: Contains thalamus (sensory relay) and hypothalamus (homeostasis, hormonal regulation).

  • Cerebrum: Responsible for higher-level cognitive functions, including thought and memory.

• Weight and Blood Supply:

  • Brain weighs approximately 3 lbs and consumes about 20% of the body's oxygen and blood supply.

  • Interruptions can lead to loss of consciousness (seconds to minutes) and potentially brain damage.

Cerebrospinal Fluid (CSF)

• Function: Cushions the brain, removes waste, and transports nutrients.

• Production: Made by ependymal cells in the brain’s ventricles and circulates within the subarachnoid space around the brain and spinal cord.

Spinal Cord Structure

• Spinal cord runs from the brainstem to the lumbar region of the spine.

• Composed of white matter (outside) and gray matter (inside).

• Gray Matter: Contains sensory and motor neurons, along with interneurons.

• White Matter: Composed of myelinated axons, carrying information up (ascending) and down (descending) the spinal cord.

Exam Overview

• Format: Approximately 101 questions total, including multiple-choice, true/false, matching, and short answer.

• Preparation: Emphasis on understanding and memorization of the nervous system anatomy and physiology; focus on clinical reasoning in clinical scenarios.