Nervous System Overview Quiz

Nervous System Overview

• The nervous system is responsible for sensory input, integration of information, and motor output, enabling movement and regulating bodily functions.
• It has two main divisions: Central Nervous System (CNS) and Peripheral Nervous System (PNS).
• CNS comprises the brain and spinal cord; PNS contains all nervous tissue outside the brain and spinal cord, including nerve clusters known as ganglia.

Reflex Arcs

• Reflex arcs are involuntary responses that protect the body.
• The process involves a receptor detecting a stimulus, sensory neuron relaying the signal to the spinal cord or brain, interneurons processing the information, motor neurons carrying a response signal to an effector, and an effector (muscle or gland) implementing the response.

Autonomic Nervous System

• The autonomic nervous system controls involuntary processes like smooth muscle action, internal organ function, and cardiac muscle action, operating outside conscious control.
• It has two divisions: parasympathetic and sympathetic.

Parasympathetic Nervous System

• Promotes "rest and digest" activities, conserves energy, and has longer pathways, resulting in slower responses.
• Uses acetylcholine as a primary neurotransmitter; this neurotransmitter stimulates contractions of smooth muscle within the body, dilates blood vessels, increases secretions from internal glands, and slows heart rate.

Sympathetic Nervous System

• Prepares the body for "fight or flight" responses, increasing energy availability.
• It has shorter pathways, resulting in faster responses.
• Primarily uses epinephrine and norepinephrine as neurotransmitters. These hormones increase blood glucose, blood pressure, heart rate, and, interestingly, although not mentioned in the text, it also slows heart rate when the threat/stimulus diminishes.

Cells of the Nervous System

• The nervous system consists of two main types of cells: neurons and neuroglia.

Neurons

• Neurons transmit nerve impulses.
• Humans possess approximately 86 billion neurons. These neurons establish approximately 100 trillion connections with one another.
• Sensory neurons (afferent) receive information from receptors and transmit it to the CNS.
• Motor neurons (efferent) carry signals from the CNS to effectors (muscles or glands).
• Interneurons connect sensory and motor neurons within the CNS, processing and integrating information.

Neuroglia (Glial Cells)

• Neuroglia support and protect neurons, maintain homeostasis, clean up debris, and form myelin sheaths.
• Schwann cells in the PNS and oligodendrocytes in the CNS form myelin sheaths around axons.
• Glial cell types include satellite cells (PNS), regulating nutrient levels and offering structural support; Schwann cell (PNS), myelination; oligodendrocytes (CNS) myelination; astrocytes (CNS), maintaining blood-brain barrier, synapse regulation, and nutrient supply; microglia (CNS), immune response; ependymal cells (CNS), creating and circulating cerebrospinal fluid.

Nerve Impulse

• Nerve impulses are electrical signals traveling along axons.
• Key stages in an action potential:
  • Resting potential: The inside of the neuron is negative compared to the outside, maintained by ion pumps (-70 mV).
  • Depolarization: Stimulus causes sodium (Na+) channels to open, Na+ rushes in, causing a positive shift in the membrane potential.
  • Repolarization and Hyperpolarization: Sodium channels close, potassium (K+) channels open, K+ rushes out, returning the membrane potential to negative, overshooting the resting potential briefly.
  • Re-establishment of resting potential: Sodium-potassium pumps restore the original ion distribution.
• Action potentials travel along axons via saltatory conduction, jumping between gaps in the myelin sheath called Nodes of Ranvier.

Myelin and its Effects

• Myelin is a fatty substance that insulates axons, increasing conduction speed.
• Glial cells like Schwann cells (PNS) and oligodendrocytes (CNS) produce myelin.
• Saltatory conduction enhances the speed of nerve impulses.

Multiple Sclerosis (MS)

• MS is an autoimmune disease damaging myelin and oligodendrocytes, leading to delayed or blocked nerve impulses.

Guillain-Barré Syndrome (GBS)

• GBS is an inflammatory condition resulting in demyelination of peripheral nerve axons.
• It causes muscle weakness progressing to paralysis, usually beginning in the extremities

Synaptic Transmission

• Synapses are the gaps between neurons.
• Neurotransmitters are chemicals released to transmit signals across synapses; some excitatory, some inhibitory.
• Excitatory neurotransmitters cause depolarization; inhibitory neurotransmitters prevent depolarization.
• Neurotransmitter release:
  • Action potential reaches axon terminal.
  • Calcium (Ca2+) channels open, Ca2+ enters axon terminal.
  • Ca2+ triggers release of neurotransmitters.
  • Neurotransmitters bind to receptors on the next neuron.

Drugs and the Nervous System

• Drugs can affect how neurons send, receive, and process information.
• Categories of drugs include depressants (e.g., benzodiazepines), stimulants (e.g., nicotine, MDMA), opioids, and hallucinogens (e.g., LSD).

Central Nervous System (CNS)

• The CNS includes the brain and spinal cord, where sensory information is processed, and motor control signals initiate action.
• The CNS is protected by the blood-brain barrier.
• Cerebrospinal fluid (CSF) cushions and nourishes the brain and spinal cord.

Brain Anatomy and Functions

• Major parts include the brainstem (midbrain, pons, medulla oblongata), cerebellum, diencephalon, and cerebrum.
• Each part has specific functions relating to various levels of bodily regulation (consciousness, involuntary actions, etc.). The cerebral cortex (outer part of cerebrum) is further divided into four lobes (frontal, parietal, temporal, and occipital) with unique functions regarding sensory, motor, and higher-order processing.

Review Questions (as listed in the original text)

• Differentiate between neurons and neuroglia.
• Compare and contrast motor neurons, sensory neurons, and interneurons.
• Label and describe functions of parts of a diagram (not present here).
• Explain how degradation of myelin sheath functions (not present here).
• Compare types of neuroglial cells (covered above).

Test your knowledge on the nervous system, including its structure and function. Explore the roles of the Central and Peripheral Nervous Systems, reflex arcs, and the autonomic nervous system. This quiz will help you understand how these components work together to facilitate bodily functions and responses.