Nervous System Overview Quiz

Nervous System Overview

• The nervous system is a complex system, responsible for bodily functions.
• It detects changes, feels sensations, initiates responses and organizes information.
• Functions are directly related to normal physiology and homeostasis.

Learning Objectives

• Identify the divisions and parts of the nervous system.
• Detail the components and function of a neuron.
• Understand the role of Schwann cells and neuroglia.
• Explain nerve impulse transmission and synapse function.
• Detail types of neurons and nerve tracts.
• Locate and describe spinal nerves, functions of brain parts.
• Define meninges and cerebrospinal fluid.
• Describe cranial nerves and their functions.
• Explain the sympathetic and parasympathetic nervous system's roles in stress response and normal functioning.

Nervous Tissue

• Neurons: Functional units of the nervous system.
  • Cell body: Contains nucleus and organelles; regulates neuron function.
  • Dendrites: Receive impulses, carry towards cell body.
  • Axon: Carries impulses away from cell body.
  • Myelin sheath: Multilayered lipid/protein covering (Schwann cells in PNS, oligodendrocytes in CNS); allows rapid impulse conduction.
  • Nodes of Ranvier: Gaps in myelin sheath.
• Neuroglia (glial cells): Non-neuronal cells of the CNS.
  • Oligodendrocytes: Produce myelin in CNS.
  • Microglia: Phagocytes of pathogens and damaged tissue.
  • Astrocytes: Support neurons and maintain chemical environment.
  • Ependymal cells: Line ventricles and central canal, circulate cerebrospinal fluid.

Nerve Tissue (cont'd)

• White matter: Myelinated axons of many neurons in CNS
• Gray matter: Primarily cell bodies of neurons in CNS
• Types of neurons:
  • Sensory (afferent): Carry impulses from receptors to CNS.
  • Motor (efferent): Carry impulses from CNS to effectors (muscles/glands).
• Nerve: Bundle of neuronal axons/dendrites outside the CNS.
  • Sensory: Only sensory neurons
  • Motor: Only motor neurons
  • Mixed: Both sensory and motor neurons
• Nerve tract: Bundle of nerve axons within the CNS.

Nerve Impulse

• Polarization: Resting state; positive outside, negative inside.
• Depolarization: Stimulus causes Na+ ions to enter membrane; reverses charge.
• Propagation: Impulse travels from stimulus point.
• Saltatory Conduction: Rapid impulse transmission between nodes of Ranvier.
• Repolarization: K+ ions exit; restores original charge.

Spinal Cord

• Encased in vertebral canal
• Gray matter: Cell bodies of motor neurons and interneurons
• White matter: Myelinated axons of neurons
• Contains cerebrospinal fluid

Spinal Cord (cont'd)

• Functions:
  • Conducts sensory impulses to brain
  • Conducts motor impulses from brain to muscles/glands
  • Reflex activities (simple, rapid, autonomic responses)
• Spinal nerves: 31 pairs
  • Cervical plexus
  • Brachial plexus
  • Lumbosacral plexus

Reflex Arc

• Components:
  • Receptor
  • Sensory neuron (afferent)
  • Integrating center (in CNS)
  • Motor neuron (efferent)
  • Effector (muscle/gland)
• Involuntary response to a stimulus

Brain

• Cerebrum: Largest part, divided into hemispheres.
  • Main areas: Frontal, parietal, temporal, occipital lobes.
• Diencephalon: Between cerebrum and brain stem (thalamus, hypothalamus, pineal gland).
• Cerebellum: Below cerebrum; coordinates movement and balance.
• Brainstem: Connects cerebrum and diencephalon with spinal cord.
  • Midbrain, pons, medulla oblongata.

Cranial Nerves

• 12 pairs emerging from brain; sensory, motor, or mixed functions.
• Examples: Olfactory, optic, oculomotor, trochlear.

Autonomic Nervous System (ANS)

• Part of PNS; controls involuntary functions.
• Sympathetic: "Fight or flight" responses (increase heart rate, dilate pupils etc.)
  • Neurotransmitter: Norepinephrine
• Parasympathetic: "Rest and digest" responses (slow heart rate, constrict pupils etc.)
  • Neurotransmitter: Acetylcholine

Additional Information

• Meninges: Protective membranes surrounding brain and spinal cord (dura mater, arachnoid mater, pia mater).
• Cerebrospinal fluid (CSF): Clear fluid surrounding brain and spinal cord for cushion and nutrient transport and waste removal.
• Ventricles: Spaces in the brain containing CSF.
• Neuroplasticity: Brain's ability to adapt and reorganize itself.
• Reflex actions: Automatic responses protecting the body from harm.
• Brain can store vast amounts of information.