Chapter 7 - The Structure of the Nervous System and Appendix (Slide Notes pt 2)

Introduction to Neuroscience (NRSC 2125)

Somatic Nervous System

  • Definition: Part of the peripheral nervous system.
  • Sensory Function:
  • Carries sensory signals from skin, skeletal muscles, joints, and sensory systems to the central nervous system (CNS).
  • Known as afferents to CNS.
  • Motor Function:
  • Carries instructions from the CNS to skeletal muscles.
  • Known as efferents from CNS.

Cranial Nerves Overview

  • Function: Deal with sensory and motor functions in the head and neck.
  • Types of Cranial Nerves:
  • Purely Sensory: Olfactory (smell), optic (vision), vestibulocochlear (balance, hearing).
  • Strictly Motor: Some cranial nerves.
  • Mixed: Contains both sensory and motor fibers.
  • Vagus Nerve: Unique as it wanders throughout the body's viscera rather than being limited to the head and neck.
  • Total: 12 pairs of cranial nerves.

Peripheral Nervous System

  • Definition: Everything except the brain, spinal cord, and retina.
  • Somatic Nervous System:
  • Involves sensory systems and skeletal muscles for movement.
  • Autonomic Nervous System: (Self-regulating)
  • Sympathetic Nervous System: Arousing response - “fight or flight.”
    • Increases heart rate, breathing, blood pressure, mobilizes glucose reserves.
  • Parasympathetic Nervous System: Calming response - “rest and digest.”
    • Decreases heart rate, breathing, blood pressure; increases digestive functions.
  • Neuron Chains: Both sympathetic and parasympathetic utilize a two-neuron chain (pre-ganglionic and post-ganglionic neurons).

Central Nervous System

  • Telencephalon: Topmost part of the brain; includes several key structures.
  • Sulcus: Small grooves in the brain (e.g., Central Sulcus).
  • Fissure: Deep grooves in the brain (e.g., Lateral Fissure).

Brain Lobes & Functions

  • Frontal Lobes:
  • Responsible for cognition, planning, decision-making, problem solving, attention, emotion regulation, and voluntary movement.
  • Parietal Lobes:
  • Involved in somatosensation and taste.
  • Temporal Lobes:
  • Associated with learning, memory, hearing, smell, and language.
  • Occipital Lobes:
  • Focused on vision processing.
  • Gyrus:
  • Bulges of tissue between grooves, important for primary motor and sensory functions.
    • Primary Motor Cortex: Located in pre-central gyrus; controls movement.
    • Primary Sensory Cortex: Located in post-central gyrus; processes body sensations.

Damage to Brain Lobes

  • Frontal Lobes:
  • Damage may impair decision-making and provoke inappropriate behavior.
  • Parietal Lobes:
  • Damage may interfere with the recognition of touch and pain; disrupts body spatial awareness.
  • Temporal Lobes:
  • Damage may lead to face recognition issues and memory loss.
  • Occipital Lobes:
  • Damage can severely impair vision, potentially leading to blindness.

Forebrain: Diencephalon

  • Thalamus:
  • Processes and relays most sensory information; often described as the “Gateway to the cerebral cortex.”
  • Damage results in altered sensitivity to sensory modalities.
  • Hypothalamus:
  • Regulates internal processes such as hormones and autonomic nervous system.
  • Damage may cause issues with body temperature regulation and emotional disturbances.

Midbrain: Mesencephalon

  • Structures:
  • Superior Colliculus: Visual function.
  • Inferior Colliculus: Auditory function.
  • Substantia Nigra: Dopaminergic neurons; associated with motor control (linked with Parkinson's disease).

Hindbrain: Myelencephalon and Metencephalon

  • Medulla:
  • Regulates vital functions such as heart rate and breathing.
  • Pons and Cerebellum:
  • Pons: Transmit signals between different parts of the brain.
  • Cerebellum: Coordinates fine motor movements; crucial for tasks requiring timing and posture control.

Limbic System

  • Function: Critical in emotions, memory, and social functions.
  • Medial Prefrontal Cortex: Emotion regulation and decision-making.
  • Hippocampus: Learning and memory.
  • Amygdala: Fear responses and threat detection.
  • Damage Effects:
  • Medial Prefrontal Cortex: Impairs social cognition and emotional regulation.
  • Hippocampus: Causes memory impairments (notable cases: Patient HM, Clive Wearing).
  • Amygdala: Leads to inappropriate aggression and emotional responses.

Deep Brain Stimulation (DBS)

  • Used in the treatment of conditions such as treatment-resistant depression.
  • Patients report experiences of acute effects such as calmness and enhanced sensory perception during stimulation.