Neuroscience Quiz: Brain Structures and Functions

Learning Outcomes

• Describe the basic cells of the central and peripheral nervous systems
• Differentiate between a typical motor and sensory neuron
• Explain the role of myelin and define white matter versus gray matter
• Describe the structural and functional differences between the central and peripheral nervous systems, as well as the somatic and autonomic nervous systems.

Nervous System

• The central nervous system (CNS) is the main processing center and coordinator of all bodily functions. It includes the brain and spinal cord.
• The peripheral nervous system (PNS) includes all nerves that extend out into the periphery. It includes all nerves that extend outside of the CNS.

Cells of the Nervous System

• Neurons are the basic units of the nervous system, transmitting electrical impulses to communicate information.
• Neuroglia are non-neuronal, non-excitable cells that support neurons. They are 5 times more abundant than neurons.

Multipolar Motor Neuron

• Cell body (with nucleus)
• Dendrites (receive information)
• Axon hillock (sums signals)
• Axon (transmit signal)
• Myelin sheath (speeds signal)
• Axon terminals (synapse with next neuron or target organ)

Pseudounipolar Sensory Neuron

• Cell body (with nucleus)
• Centrally located axon that divides into two branches
• Peripheral process to receive information
• Central process transmitting signal to the CNS
• Myelin sheath (speeds signal)
• Axon terminals (synapse with next neuron)

Neuroglia Myelination

• Oligodendrocytes: CNS, form several sheaths around multiple axons
• Schwann cells: PNS, form one myelin sheath around one section of an axon
• Myelin sheath insulates axon, increasing signal speed.
• Multiple sclerosis is caused by the degradation of oligodendrocytes.

White versus Gray Matter

• White matter: appears white due to the lipid-rich myelin sheath, transmits signals between different CNS regions.
• Gray matter: contains neuron cell bodies, dendrites, and unmyelinated axons, appears grayish because of lack of myelin and the presence of many cell bodies.

Nervous System Functional Overview

• Motor: nerves that send signals from the CNS to target organs.
• Sensory: nerves that bring signals from the periphery to the CNS.
• Autonomic: involuntary control of viscera (organs and glands).
  • Sympathetic: "fight or flight" response
  • Parasympathetic: "rest and digest" response
• Somatic: voluntary motor control and peripheral sensation (e.g., touch, movement).

Neuronal Synapse

• It's a junction between two nerve cells (neurons), or a neuron and a target organ.
• Neurotransmitters are released and travel across the synaptic cleft.
• Neurotransmitter binds to receptors on the post-synaptic neuron inducing a new nerve impulse, creating a physiological response.

Spinal Cord

• The spinal cord terminates at L2 level
• The cauda equina are spinal nerves that branch out from the spinal cord below the end of the spinal cord to target areas below. They are named and arranged accordingly (e.g. lumbar, sacral, and coccygeal areas).

Spinal Cord Meninges

• Pia mater: delicate, inner layer
• Arachnoid mater: thin, middle layer
• Dura mater: tough, outer layer
• The spinal cord is wrapped in these meninges to protect and anchor it.
• A lumbar puncture is performed to collect cerebrospinal fluid from the subarachnoid space.

Spinal Nerves

• Spinal nerves are like the trunks of trees, with roots and rootlets anchoring them to the spinal cord.
• Branching rami (branches) extend into the periphery.
• Everything distal to the spinal nerve contains both motor and sensory information.
• Everything proximal to the spinal nerve contains either motor or sensory information.

Plexuses and Peripheral Nerves

• Spinal nerves mix to create complex peripheral nerve maps, contributing to multiple dermatomes.

Autonomic Nervous System

• A component of the peripheral nervous system (PNS).
• Involuntary control of viscera (internal organs and glands)
• Two-neuron system: presynaptic neuron in CNS, postsynaptic neuron in the periphery
  • Sympathetic: "fight or flight":
  • Parasympathetic: "rest or digest"; cranial nerves & sacral spinal levels

Sympathetic Pathways

• Originate in thoracic and lumbar spinal cord (T1-L2/L3)
• Two neuron system (preganglionic and postganglionic neurons).
• Preganglionic neurons release acetylcholine (ACh).
• Postganglionic neurons release norepinephrine (NE) (or ACh for sweat glands).

Referred Pain

• The brain may misinterpret visceral pain as coming from the periphery (a confusion of somatic and visceral pathways).
• The sympathetic nervous system is involved in the process.

Test your knowledge on the anatomy and functions of the brain with this quiz. Explore topics including the cerebellum, brain lobes, and the nervous system. Understanding these core concepts is essential for any neuroscience enthusiast.