Untitled Quiz

Nervous System Overview

• The nervous system is responsible for receiving and processing sensory information from both internal and external environments.
• The nervous system is divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
• CNS consists of the brain and spinal cord.
• PNS consists of nerves.

Nervous System Components

• Neurons: Cells that transmit nerve impulses between parts of the nervous system.
• Neuroglia (Glial cells): Support and nourish neurons.
  • Microglia: Remove bacteria and debris.
  • Astrocytes: Provide metabolic and structural support to neurons.
  • Oligodendrocytes: Form myelin sheath in the CNS.
  • Schwann cells: Form myelin sheath in the PNS.

Neuron Anatomy

• Cell body: Contains the nucleus and other organelles.
• Dendrites: Short extensions receiving signals from sensory receptors or other neurons.
• Axon: Conducts nerve impulses. Individual axons are nerve fibers, which form a nerve. Some axons are covered by a protective myelin sheath. The myelin sheath is interrupted by nodes of Ranvier.

Neuron Types

• Sensory neurons: Transmit nerve signals from sensory receptors to the CNS.
• Interneurons: Found entirely within the CNS, receiving input from sensory neurons and other interneurons.
• Motor neurons: Transmit nerve impulses away from the CNS to effectors (muscles, glands, or organs).

Action Potential

• The process of signal conduction is called an action potential, occurring in neuron axons.
• A stimulus triggers an action potential when the threshold voltage is reached (around -55mV).
• Action potentials are all-or-nothing events.
• Stimulus strength does not change the action potential strength, but can cause more action potentials to occur in a given period.

Action Potential Propagation

• Unmyelinated axons: Action potentials along the entire axon.
• Myelinated axons: Action potentials jump from node to node (saltatory conduction), which is faster.
• Myelin sheath: Insulates the axon, and when damaged/absent, nerve conduction can be impaired.

The Synapse

• Synapse: A small gap between sending and receiving neurons.
• Neurotransmitters: Chemical messengers that carry signals across the synapse.
• Neurotransmitters released into the synaptic cleft, bind with specific receptors on the receiving neuron.

Signal Transmission

• Calcium ions trigger neurotransmitter release.
• Neurotransmitters bind to receptors resulting in excitation or inhibition of receiving neurons.
• Neurotransmitters are removed from the cleft to prevent continual stimulation or inhibition.

Drug Therapy

• Neurological drugs promote, prevent, or replace the action of neurotransmitters at synapses.

Integration

• Integration: Summation of excitatory and inhibitory signals.
• Inhibitory impulses drive the neuron away from action potentials.
• Inhibitory signals can prevent action potentials if they outweigh excitatory ones.

Spinal Cord Function

• The spinal cord acts as a communication pathway between the brain and the peripheral nervous system.
• Sensory receptors sends signals in ascending tracts to the brain.
• Interneurons relay signals to motor neurons.
• Stimulus response involves motor axons causing muscles to contract.

Peripheral Nervous System

• The PNS consists of nerves outside the CNS.
• Cranial nerves arise from the brain, and spinal nerves arise from the spinal cord.
• Cranial nerves primarily control functions of the head, neck, and facial regions. Vagus nerve controls internal organs.
• Some nerves are sensory, some motor, others mixed.

Case Study (Sarah)

• Sarah exhibited symptoms indicative of Multiple Sclerosis (MS).
• MS damages the myelin sheath, affecting nerve signal conduction.
• Diagnostic tools like MRI and Somatosensory Evoked Potential (SSEP) can identify neurological issues.

Questions to Consider (from the slides)

• How does myelin sheath deterioration affect nerve cell function?
• How do MRI and SSEP tests reveal neurological problems?
• Why do many MS patients eventually require wheelchairs?