Nervous System PP

Overview of the Nervous System

• Anatomical Divisions
  • Central Nervous System (CNS):
    • Comprises the brain and spinal cord
    • Functions as the body’s neural control center
  • Peripheral Nervous System (PNS):
    • Located outside the nervous system
    • Consists of nerves and sensory receptors
    • Receptors: Detect stimuli
    • Effectors: Act upon stimuli

Functions of the Nervous System

• Major Organs and Structures:
  • Brain, spinal cord, nerves
• Accessory Structures:
  • Meninges, sympathetic chain of ganglia
• Functions:
  • Communication
  • Motor control
  • Sensation

Functional Divisions

• Sensory Division (Afferent):
  • Carries impulses from sensory receptors to the CNS
• Motor Division (Efferent):
  • Carries impulses from CNS to effectors
  • Divisions of Motor Division:
    • Somatic Nervous System:
    • Voluntary control of skeletal muscle
    • Autonomic Nervous System:
    • Involuntary control of cardiac muscle, smooth muscle, and glands

Physiology of the Nervous System

Nerve Impulses

• Resting Membrane Potential:
  • Basis for nerve impulse, needed to be maintained
  • Polarized membrane: outside is positive, inside is negative
  • Depolarization: Sodium flows into the cell
  • Repolarization: Potassium flows out of the cell

Local Potentials

• Start at dendrite, travel towards trigger zone
• Characteristics:
  • Graded: strength varies with ion flow
  • Decremental: effects decrease with distance
  • Reversible: returns to normal after stimulation
  • Can be excitatory or inhibitory

Action Potentials

• Travel from trigger zone to synaptic knob
• Require a threshold stimulus
• Characteristics:
  • Not graded, decremental, or reversible
  • Speed is enhanced by myelination

Reflexes

• Involuntary, predictable motor response to a stimulus
• Reflex Arc Components:
  1. Receptor: Dendrite receiving stimulus
  2. Afferent Neuron: Sensory neuron carrying the signal to CNS
  3. Integrating Center: Brain or spinal cord
  4. Efferent Neuron: Motor neuron carrying the signal from CNS
  5. Effector: Structure causing the effect

Types of Memory

• Immediate Memory: Lasts a few seconds
• Short-term Memory: Lasts a few seconds to a few hours; disruption leads to forgetting
• Long-term Memory: Results from chemical changes in neurons
  • Involves growth of dendrites and new connections

Language Areas

• Wernicke’s Area:
  • Located in the temporal lobe
  • Interprets incoming language
• Broca’s Area:
  • Located in the frontal lobe
  • Responsible for finding words for outgoing language

Nutritional Requirements

• Sodium and Potassium: Necessary for maintaining resting membrane potentials
• Fats: Essential for myelination, particularly in children

Effects of Aging on the Nervous System

• Cognitive abilities increase in youth, remain stable in adulthood, decline in old age
• Short-term memory and verbal skills decline with age
• Intellectual performance may remain high until around age 80
• Reaction times slow down due to less efficient neurons

Diagnostic Tests for Nervous System Disorders

• Lumbar Puncture:
  • Collects and analyzes cerebrospinal fluid (CSF)
• Nerve Conduction Study:
  • Assesses conduction of nerve impulses along peripheral nerves

Nervous System Disorders

• Cerebrovascular Accident (CVA): Stroke caused by lack of blood supply to the brain
• Alzheimer’s Disease: Progressive, irreversible dementia
• Huntington’s Disease: Genetic disorder causing uncoordinated movements
• Parkinson’s Disease: Degenerative disorder due to dopamine cell degeneration
• Multiple Sclerosis: Demyelination of axons leading to loss of sensation and motor control
• Paralysis: Loss of muscle function due to brain-muscle pathway interruption
• Epilepsy: Characterized by recurring seizures from misfiring electrical signals
• Hydrocephalus: Accumulation of excess cerebrospinal fluid in the brain
• Cerebral Palsy: Symptoms arising from brain injury before age 5