Nervous System Quiz - Chapter 4

Nervous System Overview

• The nervous system has three main functions: sensory input, integration, and motor output.
• Sensory input involves monitoring changes (stimuli) inside and outside the body.
• Integration processes and interprets sensory input and decides upon a response.
• Motor output is the response to stimuli, activating muscles or glands.

Structural Classification of the Nervous System

• The central nervous system (CNS) consists of the brain and spinal cord.
• The peripheral nervous system (PNS) comprises nerves outside the brain and spinal cord.

Functional Classification of the Peripheral Nervous System

• The sensory (afferent) division carries information to the CNS.
• The motor (efferent) division carries impulses away from the CNS.
• The motor division has two subdivisions: somatic (voluntary) and autonomic (involuntary).

Nervous Tissue: Support Cells (Neuroglia or Glia)

• Astrocytes are abundant, star-shaped cells forming a barrier between capillaries and neurons. They control the chemical environment of the brain (CNS).
• Microglia (CNS) are spider-like phagocytes that dispose of debris.
• Ependymal cells (CNS) line cavities of the brain and spinal cord, circulating cerebrospinal fluid.
• Oligodendrocytes (CNS) produce myelin sheaths in the central nervous system.

Neuroglia vs. Neurons

• Neuroglia cells divide; neurons do not.
• Most brain tumors (gliomas) involve neuroglia cells, not neurons.

Support Cells of the PNS

• Satellite cells protect neuron cell bodies.
• Schwann cells form myelin sheaths in the peripheral nervous system.

Nervous Tissue: Neurons

• Neurons are nerve cells specialized for transmitting messages.
• Major regions of neurons include the cell body (nucleus and metabolic center), processes extending from the cell body (dendrites and axons), and axons, dendrites, Nissl substance, Axon hillock ,neurofibrils , Axonal terminal.
• Cell body: includes the nucleus and large nucleolus.

Neuron Anatomy

• Extensions outside the cell body include dendrites (conducting impulses toward the cell body) and axons (conducting impulses away from the cell body, only one per neuron).

Axons and Nerve Impulses

• Axonal terminals contain neurotransmitters in vesicles.
• Synaptic cleft gap separates axonal terminals from the next neuron.
• Synapse is the junction between nerves.

Nerve Fiber Coverings

• Schwann cells produce myelin sheaths in a jelly-roll fashion.
• Nodes of Ranvier are gaps in the myelin sheath along the axon.

Clinical Application

• Multiple Sclerosis involves destruction of the myelin sheath, hardening it into scleroses. This is an autoimmune disorder.

Neuron Cell Body Location

• Most neuron cell bodies are in the CNS (central nervous system).
• Gray matter contains cell bodies and unmyelinated fibers.
• Nuclei are clusters of cell bodies within the white matter of the CNS.
• Ganglia are collections of cell bodies outside the CNS.

Functional Classification of Neurons

• Sensory (afferent) neurons carry impulses from receptors to the CNS.
• Motor (efferent) neurons carry impulses from the CNS to effectors (muscles or glands).
• Interneurons (association neurons) connect sensory and motor neurons within the CNS.

Structural Classification of Neurons

• Multipolar neurons have many extensions from the cell body.
• Bipolar neurons have one axon and one dendrite.
• Unipolar neurons have a short single process leaving the cell body.

How Neurons Function (Physiology)

• Irritability is the ability to respond to stimuli.
• Conductivity is the ability to transmit an impulse.
• The plasma membrane at rest is polarized (fewer positive ions inside the cell than outside).

Continuation of the Nerve Impulse between Neurons

• Impulses can cross the synapse to another nerve.
• Neurotransmitters are released from the axon terminal of the first neuron.
• Neurotransmitters stimulate receptors on the dendrites of the next neuron.

The Reflex Arc

• Reflex is a rapid, predictable, and involuntary response to stimuli.
• A reflex arc is a direct route from a sensory neuron to an interneuron to an effector.

Types of Reflexes and Regulation

• Autonomic reflexes regulate smooth muscle, heart and blood pressure, glands, and the digestive system.
• Somatic reflexes activate skeletal muscles.

Regions of the Brain

• Brain regions include: cerebral hemispheres, diencephalon, brain stem, and cerebellum.

Cerebral Hemispheres (Cerebrum)

• The cerebral hemispheres (cerebrum) are paired superior parts of the brain, comprising more than half of the brain mass.
• The surface has ridges (gyri) and grooves (sulci).

Lobes of the Cerebrum

• Fissures divide the cerebrum into four surface lobes : frontal, parietal, occipital, and temporal.

Specialized Areas of the Cerebrum

• Somatic sensory area receives impulses from the body's sensory receptors.
• Primary motor area sends impulses to skeletal muscles.
• Broca's area is involved in speech.
• Cerebral areas are involved in special senses including gustatory (taste), visual, auditory, and olfactory (smell) areas.
• Interpretation areas of the cerebrum include Speech/language, language comprehension, and general interpretation.

Layers of the Cerebrum

• Gray matter forms the outer layer, composed mostly of neuron cell bodies.
• White matter contains fiber tracts inside the gray matter.
• Examples of tracts include the corpus callosum, which connects the hemispheres.

Layers of the Cerebrum (basal nuclei)

• Basal nuclei are islands of gray matter within the cerebrum, regulating voluntary motor activities by modifying information sent to the motor cortex.

Diencephalon

• The diencephalon sits above the brain stem, enclosed by the cerebral hemispheres.
• It contains the thalamus, hypothalamus, and epithalamus.

Thalamus

• The thalamus surrounds the third ventricle and functions as a relay station for sensory impulses.

Hypothalamus

• Located under the thalamus, the hypothalamus is an important autonomic nervous system center and regulate body temperature, water balance, and metabolism.
• The hypothalamus is an important part of the limbic system and the pituitary gland is attached to it.

Epithalamus

• The epithalamus forms the roof of the third ventricle and houses the pineal body, an endocrine gland.
• It includes the choroid plexus, which forms cerebrospinal fluid.

Brain Stem

• The brain stem attaches to the spinal cord and consists of the midbrain, pons, and medulla oblongata.

Midbrain

• The midbrain is primarily composed of nerve fibers and contains reflex centers for vision and hearing.

Pons

• The pons is a bulging center part of the brain stem largely composed of fiber tracts, with nuclei involved in breathing control.

Medulla Oblongata

• The medulla oblongata is the lowest part of the brain stem, merging into the spinal cord.
• It includes important fiber tracts and contains control centers for heart rate, blood pressure, breathing, swallowing, and vomiting.

Cerebellum

• The cerebellum has two hemispheres with convoluted surfaces.
• It is responsible for involuntary coordination of body movements.

Protection of the Central Nervous System

• Protection methods include the scalp and skin, skull and vertebral column, and the meninges (dura mater, arachnoid layer, pia mater).

Cerebrospinal Fluid

• Cerebrospinal fluid is similar to blood plasma in composition.
• It is formed by the choroid plexus and acts as a watery cushion protecting the brain.
• It circulates in the arachnoid space, ventricles, and central canal of the spinal cord.

Spinal Cord

• The spinal cord extends from the medulla oblongata to the region of T12.
• Below T12 is the cauda equina, a collection of spinal nerves.
• Enlargements occur in the cervical and lumbar regions.

Spinal Cord Anatomy

• The spinal cord has an exterior white matter (conduction tracts) and an internal gray matter (mostly cell bodies).
• Regions include dorsal (posterior) and anterior (ventral) horns, and a central canal filled with cerebrospinal fluid.
• Meninges cover the spinal cord, and nerves leave at the level of each vertebra.

Peripheral Nervous System

• The PNS consists of nerves and ganglia outside the CNS.
• A nerve is a bundle of neuron fibers bundled by connective tissue.

Classification of Nerves

• Mixed nerves contain both sensory and motor fibers.
• Afferent (sensory) nerves carry impulses toward the CNS.
• Efferent (motor) nerves carry impulses away from the CNS.

Spinal Nerves

• There is a pair of spinal nerves at the level of each vertebra.

Test your knowledge on the functions and structures of the nervous system with this quiz focusing on key concepts from Chapter 4. Explore the roles of satellite cells, neurotransmission, myelin sheath, and more. Perfect for students looking to strengthen their understanding of neurobiology.