Pathophysiology Test 3

Central Nervous System

Brain and Spinal Cord

Peripheral Nervous System

-Cranial nerves

-Spinal nerves

-Afferent (Ascending)

-Efferent (Descending)

Peripheral Nervous System Branches Into

-Somatic nervous sytem

-Autonomic nervous system

Somatic Nervous System

Regulates Voluntary Control

Autonomic Nervous System

-Regulating body's internal environment through involuntary control

-Coordinates and maintains a steady state among visceral (internal) organs

-Considered part of the PNS, but components are located in both CNS and PNS

Cells of the Nervous System

Neurons & Neurologic cells

Neurons

-Primary cells of nervous system

-Transmits and receives information

-Vary in size and structure throughout the nervous system

Neurologic cells

Provides structural support, protection, and nutrition for neurons

Cellular Constituents of Neurons

Microtubules, Neurofibrils, Nissi substances, Microfilaments

Microtubules

Spiral strands of protein molecules that form a tubelike structure

Neurofibrils

Bundles of neurofilaments that provide support for dendrites and axon

Microfilaments

Long, thin fibers that function in the movement and support of the cell

Structural Components of Neurons

-Cell body (Soma)

-Dendrites

-Axons

Cell Body (Soma) of Neurons

Mostly in the CNS

Dendrites of Neurons

Extensions that carry impulses toward the cell body

Axons of Neurons

Carry impulses away from the cell body

Structural Classifications of Neurons

Unipolar, Pseudounipolar, Bipolar, and Multipolar

Unipolar Neurons

Have a short single process leaving the cell body

Pseudounipolar Neurons

Have only one fused axon that extends from cell body and divides into two processes

-One process carries sensory information from sensory receptors to cell body

-Other process carries sensory information from cell body to spinal cord

-Sensory neurons that carry information related to pain, touch, and pressure

Bipolar Neurons

One axon and one dendrite

Multipolar Neurons

Many extensions from the cell body

Functional Classifications of Neurons

-Sensory (Afferent)

-Interneurons (Associational)

-Motor (Efferent)

Sensory (Afferent)

Transmit impulses toward the CNS

Interneurons (Associational)

Lie w/in CNS receive signals from incoming sensory neurons, interpret them and stimulate outgoing motor neurons

Motor (Efferent)

Carry impulses away from the CNS

Neuroglia

"Nerve glue"

-Makes up half of the total volume of the brain and spinal cord

Astrocytes

-Form specialized contacts between neuronal surfaces and blood vessels

-Provide rapid transport for nutrients and metabolites

-Thought to form an essential component of the blood-brain barrier

-Appear to be scar-forming cells of the CNS, which may be foci for seizures

-Appear to work with neurons in processing information and memory storage

Oligodendroglia (Oligodendrocytes)

Formation of myelin sheath in the CNS

Microglia

Responsible for clearing cellular debris (phagocytic properties) and the key immune cells in the CNS

Ependymal Cells

Serve as a lining for verticals and choroid plexuses involved in production of cerebrospinal fluid

Schwann Cells

-Formation of myelin sheath in the PNS

-Direct axonal regrowth and function recovery in the PNS

Nonmyelinating Schwann Cells

Provide neuronal metabolic support and regeneration in the PNS

Satellite Glial Cells

Surround sensory, sympathetic, and parasympathetic nerve cell bodies and ganglia to provide protection and promote cellular communication

-Similar to astrocytes in the CNS

Nerve Impulse

Neurons generate and conduct electrical and chemical impulses

Synapses

Region between 2 neurons

Neurotransmitters

Carry signals from one nerve cell (neurons) to another across a tiny gap called a synapse

Brain

Enable person to reason, function intellectually, express mood, and interact

3 Major Divisions the Brain

-Forebrain (Prosencephalon)

-Midbrain (Mesencephalon)

-Hindbrain (Rhombencephalon)

Forebrain (Prosencephalon)

Complex perceptual, cognitive, and behavioral processes

-Telencephalon & Diencephalon

Midbrain (Mesencephalon)

Receives sensory and motor information from the rest of the body

Hindbrain (Rhombencephalon)

The rear division of the brain, which in the mature vertebrate contains the cerebellum, pons, and medulla

-Metencephalon & Myelencephalon

Spinal Cord

Lies within vertebral canal, protected by vertebral column

Coverings of the Spinal Cord

-Dura mater

-Arachnoid mater

-Pia mater

Dura Mater

Thick, outermost layer of the meninges surrounding and protecting the brain and spinal cord

Arachnoid Mater

-Weblike middle layer of the three meninges

-Middle layer of the meninges

Pia Mater

Thin, delicate inner membrane of the meninges

Functions of the Spinal Cord

-Connects the brain and the body

-Conduct somatic and autonomic reflexes

-Provides motor pattern control centers

-Modulates sensory and motor function

Gray Matter of the Spinal Cord

Nerve cell bodies arranged in a butterfly shape with anterior and posterior "horns"

White Matter of the Spinal Cord

Surrounds the gray matter

-Composed of both myelinated and unmyelinated axons

-It has three regions, anterior, lateral, and posterior columns

Upper Motor Neurons

Motor neurons in the central nervous system that control the lower motor neurons in the peripheral nervous system

Lower Motor Neurons

Axons leave the CNS, extend through PNS to skeletal muscles

-Cell bodies in anterior horns of spinal cord and in cranial nerve nuclei of brainstem

Neuromuscular Junction

Point of contact between a motor neuron and a skeletal muscle cell

Cranium

-8 bones

-Encloses and protects brain and associated structures

Meninges

Protective membranes surrounding the brain and spinal cord

Cerebrospinal Fluid

Clear, colorless fluid that protects brain and spinal cord from jolts and blows

Ventricles

Cavities where CSF circulates

Vertebral Column

-33 vertebrae

-Intervertebral disks

CNS Blood Supply

-Brain receives 20% of Cardiac output (800-1000 mL/min)

-Blood supply to the spinal cord comes from vertebral arteries and the aorta

Brain Blood Supply

20% of Cardiac output

-800-1000 mL/min

Spinal Cord Blood Supply

Comes from vertebral arteries and the aorta

Cranial Nerves

12 pairs

-From brain

-Sensory, motor, and mixed

Spinal Nerves

31 pairs

-From spinal cord

-Mixed nerves

2 Divisions of Autonomic Nervous System

Sympathetic & Parasympathetic

Sympathetic Nervous System

The division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations

-"Fight or Flight"

-Innervation from cell bodies located from T1 through L2 regions of spinal cord

Parasympathetic Nervous System

The division of the autonomic nervous system that calms the body, conserving its energy

-"Rest and Tranquility"

-Innervation from cell bodies located in the cranial nerve nuclei and sacral region of the spinal cord

Neurons of the Autonomic Nervous System

Preganglionic & Postganglionic

Preganglionic Neuron

In the autonomic nervous system of the PNS

-Neuron that has its cell body located in the CNS and whose axon extends into the PNS to synapse with a second neuron at an autonomic ganglion

-The second neuron's axon synapses with the target organ

Postganglion Neuron

An autonomic motor neuron that extends from an autonomic ganglion to a visceral effector

Pain

-Unpleasant but protective phenomenon

-Unique experience by each individual

-Cannot be defined, identified, or measured by observer

Stimuli that Activate Skin Pain

Pricking, Cutting, Crushing, Burning, Freezing

Stimuli that Activate GI Tract Pain

-Engorged or inflamed mucosa

-Distention or spasm of smooth muscles

-Traction on mesenteric attachment

Stimuli that Activate Skeletal Muscles Pain

Ischemia, Injuries of connective tissue sheets, Necrosis, Hemorrhage, Prolonged contraction, Injection of irritating solutions

Stimuli that Activate Joint Pain

Synovial membrane inflammation

Stimuli that Activate Artery Pain

Piercing, Inflammation

Stimuli that Activate Head Pain

Traction, Inflammation, Displacement of arteries, Meningeal structures, and Sinuses

-Prolonged muscle contraction

Stimuli that Activate Heart Pain

Ischemia & Inflammation

Stimuli that Activate Bone Pain

Periosteal injury: Fractures, Tumor, Inflammation

Thermoregulation

Fever, Hyperthermia, Hypothermia, Trauma & Temp

Hyperthermia

Abnormally high body temperature

Hypothermia

Abnormally low body temperature

What Causes Heat Production

-Chemical reactions of metabolism

-Skeletal muscle contraction

-Nonshivering thermogenesis

Heat Production During Chemical Reactions of Metabolism

Occur during ingestion and metabolism of food and while maintaining the body at rest (basal metabolism)

-Occur in the body core (ex: liver)

Heat Production During Skeletal Muscle Contraction

Gradual increase in muscle tone or raid muscle oscillations (shivering)

Heat Production During Nonshivering Thermogenesis

Epinephrine is released and produces a rapid, transient increase in heat production by increasing the basal metabolic rate

-A quick, brief effect that counters heat lost through conduction and convection

-Involves brown adipose tissue, which decreases markedly in older adults

Thyroid Hormone

Increases metabolism

Heat Loss Through Radiation

Heat loss through electromagnetic waves emanating from surfaces with a temp higher than the surrounding air

Heat Loss Through Conduction

Heat loss by direct molecule-to-molecule transfer from one surface to another so the warmer surface loses heat to the cooler surface

Heat Loss Through Convection

Transfer of heat through currents of gases or liquid

-Exchanges warmer air at the body's surface with cooler air in the surrounding space

Heat Loss Through Vasodilation

Diverts core-warmed blood to the surface of the body, with heat transferred by conduction to the skin surface and from there to the surrounding environment

-Occurs in response to autonomic stimulation under control of the hypothalamus

Heat Loss Through Evaporation

Body water evaporates from the surface of the skin and the linings of mucous membranes

-A major source of heat reduction connected with increased sweating in warmer surroundings

Heat Loss Through Decreased Muscle Tone

Exhausted feeling caused by moderately reduced muscle tone and curtailed voluntary muscle activity

Heat Loss Through Increased Respiration

Air is exchanged with the environment through a normal process

-Minimal effect

Heat Loss Through Voluntary Mechanisms

"Stretching out" and "Slowing down" in response to high body temperatures

-Increasing body surface area available for heat loss

-Dressing in light-colored, loose-fitting garments

Heat Loss Through Adaptation to Warmer Climates

Gradual process beginning with lassitude, weakness, and faintness

-Proceeding through increased sweating

-Lowered sodium content

-Decreased HR

-Increased stroke volume and extracellular fluid volume

-Terminating in improved warm-weather functioning

-Decreased symptoms of heat intolerance

-Work output, endurance, and coordination increase

-Subjective feelings of discomfort decrease

REM

Sleep in which vivid dreams typically occur

-This type of sleep increases as the night progresses while stage 4 sleep decreases

Non-REM

The form of sleep with few eye movements, which are slow rather than fast

Insomnia

Recurring problems in falling or staying asleep

Obstructive Sleep Apnea

A disorder in which a person, while asleep, stops breathing because his or her throat close

-The condition results in frequent awakenings during the night

Hypersomnia

Excessive daytime sleepiness

Narcolepsy

A sleep disorder characterized by uncontrollable sleep attacks

-The sufferer may lapse directly into REM sleep, often at inopportune times