Esther Ramirez
Period #5
Nervous System

Drugs of Abuse

Neurotransmitters

Major Parts and Functions of the Brain

Classification of Neurons

Connective Tissue Covering

Cranial Nerves

Spinal Nerves

Divisions and Subdivisions of the NS

Disorders/Diseases

Tissues

Action potential & the Nerve Impulse

Compare & contrast the ANS with the SNS

Major Parts and Functions of the Spinal Cord

Major Functions of the NS

Functions

Provides two-way communication to and from the brain and body. Major reflex center: reflexes are initiated and completed at sthe pinal cord

White Matter: Myelinated and nonmyelinated nerve fibers allow communication between parts of
spinal cord, and spinal cord and brain

Spinal roots:

  • Dorsal horns: interneurons that receive somatic and visceral sensory input
  • Ventral horns: some interneurons; somatic motor neurons
  • Lateral horns (only in thoracic and superior lumbar regions): sympathetic
    neurons
  • Ventral roots: bundle of motor neuron axons that exit the spinal cord
  • Dorsal roots: sensory input to cord
  • Dorsal root (spinal) ganglia: cell bodies of sensory neurons
  • Spinal nerves: formed by fusion of dorsal and ventral roots

Gray Matter is divided up into four groups: Somatic sensory (SS), visceral sensory (VS), visceral (autonomic) motor
(VM) and somatic motor (SM)

White matter is divided up into 3 white columns (funiculi): Dorsal, Ventral, and Lateral.

Spinal Cord Trauma and Disorders:

  • Paresthesias: caused by damage to dorsal roots or sensory tracts
  • Paralysis: caused by damage to ventral roots or ventral horn cells
  • Paraplegia: transection between T1 and L1
  • Quadriplegia: transection in cervical region
  • Spinal shock: transient period of functional loss caudal to lesion
  • Amyotrophic lateral sclerosis (ALS)

Functions:

1.) Sensory Input: information gathered by sensory receptors about internal and external changes
2.) Integration: Processing and interpretation of sensory input
3.) Motor Output: Activation of effector organs (muscles and glands) produces a response

CNS uses the integration and the core center. PNS uses spinal nerves and cranial nerves.

Sensory (afferent) division
Somatic sensory fibers: convey impulses from skin, skeletal muscles, and joints
to CNS
Visceral sensory fibers: convey impulses from visceral organs to CNS


Motor (efferent) Division
Transmits impulses from CNS to effector organs
1.) Somatic NS (voluntary)
2.) Autonomic NS (involuntary)

Neuroglia

Neuroglia (glial cells): small cells that surround and wrap delicate neurons
Neurons (nerve cells): excitable cells that transmit electrical signals

Subdivisions:

Divisions:

PNS: Provides links from and to world outside our body, Consists of all neural structures outside brain and spinal cord that can be broken down into four parts: sdnsory receptors, Transmission Lines: Nerves and Their Structure and Repair, Motor Endings and Motor Activity, and the reflex activity

CNS: - Consists of only the brain and spinal cord -

ANS

SNS: cell body is in CNS, and a single, thick myelinated group A axon extends in spinal or cranial nerves directly to skeletal muscle

Preganglionic neuron: cell body in CNS with thin, lightly myelinated preganglionic axon extending to ganglion

Postganglionic (ganglionic) neuron (outside CNS): cell body synapses with preganglionic axon in autonomic ganglion with nonmyelinated postganglionic axon that extends to effector organ

Releases ACh

Major neurotransmitters of ANS are acetylcholine (ACh) and
norepinephrine (NE)

Ach (same as ACh used by somatic motor neuron) is released by
cholinergic fibers at:

Effects of neurotransmitter depends on whether it binds to cholinergic
receptor or adrenergic receptor

Location: Brain stem and spinal cord, hypothalamus, and cerebral cortex

contains motor neurons that Innervate smooth muscles, cardiac muscle, and glands. Make adjustments to ensure optimal support for body activities; aka involuntary nervous system or general visceral motor
system

Disorders of ANS:

  • Hypertension (High BP)
  • Raynaud's Disease
  • Autonomic Dysreflexia

Reflex Arc

Visceral reflex arcs have same components as somatic reflex arcs: receptor, sensory neuron, integration center, motor neuron, and effector, but three main differences:
1.) Visceral reflex arc has two consecutive neurons in the motor pathway
2.) Afferents fibers are visceral sensory neurons
3.) Effectors are smooth muscle, cardiac muscle, and glands rather than skeletal muscles

Cerebral Hemispheres, diencephalon, brain stem (consisting of the midbrain, pons, and medula), cerebellum, Basal Nuclei (Ganglia), gray mater, and white mater.

Basic pattern found in CNS: central cavity surrounded by gray matter, with white matter
external to gray matter

Cerebral cortex is the "Executive site" of the brain

Site of conscious mind: awareness, sensory perception, voluntary motor initiation,
communication, memory storage, understanding

Cerebral White Mater: Association, commissural, and projection fibers. Responsible for communication between cerebral areas, and between cortex and lower
CNS

Basal Nuclei (Ganglia):

Brain Diseases:

  • Parkinson’s disease and Huntington’s disease are disorders of the basal nuclei

Diecephalon: consists of thalamus, hypothalamus, epithalamus

Hypothalamus: main visceral control and regulating center that is vital to
homeostasis

Thalamus: Main thalamic function is to act as relay station for information coming into cortex

Epithalamus: forms roof of 4th ventricle

Hypothalamic disturbances cause a number of disorders such as:

  • Sever body wasting
  • Obesity
  • Sleep disturbances
  • Dehidration
  • Emotional Imbalances
    *Can be damaged by tumors, radiation, surgery or trauma

Medulla Oblongata: Blends into spinal cord at foramen magnum, contains the fourth ventricle, and Contains choroid plexus: capillary-rich membrane that forms cerebral spinal fluid.

Cerebrum: Plays role in thinking, language, and emotion, Balance and coordination, and Processes input from cortex, brain stem, and sensory receptors to provide precise, coordinated movements of skeletal muscles

Sensory receptors: specialized to respond to changes in environment (stimuli)

Activation results in graded potentials that trigger nerve impulses

Awareness of stimulus (sensation) and interpretation of meaning of stimulus (perception)
occur in brain

Three ways to classify receptors: by type of stimulus, body location, and structural
complexity

Classification by Location
Exteroceptors:

  • Respond to stimuli arising outside body
  • Receptors in skin for touch, pressure, pain, and temperature
  • Most special sense organs

Interoceptors (visceroceptors):

  • Respond to stimuli arising in internal viscera and blood vessels
  • Sensitive to chemical changes, tissue stretch, and temperature changes
  • Sometimes cause discomfort but usually a person is unaware of their workings

Proprioceptors:

  • Respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective
    tissue coverings of bones and muscles
  • Inform's brain of movements

Sensation and perception

Nerve: cordlike organ of PNS

Bundle of myelinated and nonmyelinated peripheral axons enclosed by connective
tissue

Endoneurium: loose connective tissue that encloses axons and their myelin
sheaths (Schwann cells)

Perineurium: coarse connective tissue that bundles fibers into fascicles

Epineurium: tough fibrous sheath around all fascicles to form the nerve

Ganglia: contain neuron cell bodies associated with nerves in PNS

Pure sensory (afferent) or pure motor (efferent) nerves are rare; most nerves are mixed

12 pairs of cranial nerves are associated with brain

Most are mixed nerves, but two pairs purely sensory

Olfactory nerves, optic nerves, oculomotor nerves, trochelar nerves, trigeminal nerves, abducen nerves, facial nerves, Vestibulocochlear nerves, Glossopharyngeal nerves, vagus nerves, accessory nerves, and Hypoglossal nerves

31 pairs of spinal nerves; Supply all body parts except head and part of neck

Ventral roots: Contain motor (efferent) fibers from ventral horn motor neurons that innervate
skeletal muscles

Dorsal roots: Contain sensory (afferent) fibers from sensory neurons in dorsal root ganglia
that conduct impulses from peripheral receptors

Inborn (intrinsic) reflex: rapid, involuntary, predictable motor response to stimulus

Components of a Reflex Arc (neural path):
1.) Receptor: site of stimulus action
2.) Sensory neuron: transmits afferent impulses to CNS
3.) Integration center: either monosynaptic or polysynaptic region within CNS
4.) Motor neuron: conducts efferent impulses from integration center to effector
organ
5.) Effector: muscle fiber or gland cell that responds to efferent impulses by
contracting or secreting

Reflexes are classified as:

  • Somatic Reflexes; active skeletal muscles)
    • Autonomic (visceral) reflexes; Activate visceral effectors (smooth or cardiac muscle or glands)

Automatic nervous system (ANS) consists of motor neurons that:

  • Innervate smooth muscles, cardiac muscle, and glands
    -Make adjustments to ensure optimal support for body activities
  • AKA involuntary nervous system or general visceral motor
    system

Comparison: Most spinal and many cranial nerves contain both somatic and
autonomic fibers. Also, the higher part of the brain centers regulate and coordinate both systems. Adaptations usually involve both skeletal muscles and visceral organs.

Traumatic brain injuries: Concussion, contusion, Subdural or subarachnoid hemorrhage, and cerebral edema

31 pairs of spinal nerves; Supply all body parts except head and part of neck

Action potentials: Long-distance signals of axons

Arachnoid Mater: The arachnoid mater is places underneath the dura mater. It is the second protctant layer and looks glossy. It is easier to take off.

Pia Mater: The pia mater is the last protectant layer and is can be taken off very easily. This is already embedded within the actual brain tissue.

Dura Mater: upper most layer on the superficial superior side of the brain and skull. It is the otter most protectant layer for the brain. Very difficult to take off.

Action potentials only occur in the muscle cells and axon of neurons

Action potentials (APs) do not decay over distance as graded potentials do

The 4 Steps to activate an Action Potential:
1.) Resting state: All gated Na+ and K+ channels are closed
2.) Depolarization: Na+channels open
3.) Repolarization: Na+ channels are inactivating, and K+ channels open
4.) Hyperpolarization: Some K+ channels remain open, and Na+ channels reset

Methamphetamie: meth enters the sopamine vesicles forcing the dopamine meurotransmitters to get out. It makes users feel intense pleasure and exhilaration.

Alcohol: It interacts with GABA receptors to make them even more inhibitory. Alcohol effects memory formation, decision making, and impulse control.

Cocaine: Cocaine blocks the transporters leaving dopamine in the synaptic cleft; thus, dopamine binds again and again. Cocaine affects the reward pathway and controls the voluntary movements.

LSD: LSD interacts with some serotonin neurotransmitters, blocking them. It is responsible for feelings of wakefulness and evokes a startled response to unexpected stimuli.

Heroine: Mimics inhibitory, turning off dopamine inhibition. Heroine affects the pain signals, stress response and emotional attachment.

Ecstasy: Acts like serotonin and is transported in the neuron. This alters transporter and does job inverse. It is responsible for mood, sleep, perception, and appetite.

Mariguana: THC, chemical in mariguana, mimics anadamide and binds to cannabinoid receptors. Is responsible to feeling relaxed and calm, and is unnecessary in short term memories.