Nervous System Grecia Lopez, Per.1

Nervous System
Grecia Lopez, Per.1

Major Functions of the Nervous System

Coordinating and communicating system via electrical signals

Major divisions and Subdivisions of the Nervous System

Tissues

Connective Tissue Coverings

Major Parts and Functions of the Brain

Major Parts and Functions of the Spinal Cord

Action Potential and Nerve Impulse

12 Cranial Nerves

Spinal Nerves

Neurotransmitters

Autonomic Nervous System vs Somatic Nervous System

Reflex Arcs

Control the immediate response of the body to stimulus

Major Nervous System Disorders

Drugs of Abuse

Visceral Reflex Arcs:

Similar to the somatic reflex arcs (has everything 1-6 the same) BUT they differ in:

Visceral arcs have two consecutive neurons in motor pathway.
Afferent fibers are visceral sensory neurons.
Effectors are smooth muscles, cardiac muscle, and glands.

Somatic Reflex Arcs:

Stimulus
Receptor
Sensory Neuron
Integration Center
Motor Neuron
Effector

Activates Skeletal Muscles

Cerebellum

Mainatins balance and coordination

Brainstem

Cerebrum

Pons

Responsible for breathing
Relays communication and information

Medulla

Regulates the cardiovascular and respiratory systems

Mid Brain

Motor functions
Eye movement
Visual processing
Auditory processing

Parietal Lobe

Sensory functions

Occipital Lobe

Visual functions

Frontal Lobe

Motor functions

Temporal Lobe

Auditory functions

The Diencephalon

Releases signals, hormones, and rythms to the cerebral cortex.

Hypothalamus

Controls hormone release

Epithalamus

Connects the brain to the limbic system

Thalamus

Receives sensory information and sends it to the cerebral cortex

Pineal Gland

Melatonin for sleep cycles

Sutures and Fissures

Longitudinal Fissure
Transverse Fissure
Parieto-Occipital sulcus
Central sulcus
Lateral Fissure

III. Oculomotor Nerves

IV. Trochlear Nerve

II. Optic Nerves

V. Trigeminal nerve

I. Olfactory Nerves

VI. Abducens nerve

VII. Facial nerve

X. Vagus nerve

XII. Hypoglossal nerve

XI. Accessory nerve

VIII. Vestibulocochlear nerve

IX. Glossopharyngeal nerve

Glutamate:

Excitatory neurotransmitter in the cortex.
Involved in memory and learning

Serotonin:

"Happy Chemical"
Involved in sleep, appetite, emotion, and decision making.

Dopamine:

Reward mechanism
“Pleasure Chemical”
Involved in decision-making, movement, and reward processing.

Norepinephrine:

NE
Involved in mood, memory, and stress.

Acetylcholine:

ACh
Works primarily in muscle.
Translates impulses to actual actions.

gamma-Aminobutyric acid (GABA):

Inhibitory
Involved in learning.

PNS

Cranial and spinal nerves.
Communication between the CNS and the rest of the body

CNS

Brain + Spinal Cord
Integrative and control centers

Motor Division

Motor nerve fibers
CNS impulses to effectors (muscles and glands)

Sensory Division

Somatic and visceral sensory fibers
Impulses from CNS receptors

Autonomic System

Visceral (involuntary) motor fibers
CNS to cardiac muscles, skeletal muscles, and glands.

Somatic System

Somatic (voluntary) motor nerve fibers
CNS to skeletal muscles

Parasympathetic Divison

Meant to conserve energy.
House keeping functions.
Rest and Digest System.

Sympathetic Divison

Mobilizes body systems during activity.
Flight or Fight System.

Opioids

Heroine and morphine
Taken by pill, injecting, snorting, or smoking.
Depressants
Slow down the nervous system and cloud ones thoughts.
Can cause pinpoint pupil and a rush of pleasure and warmth.
Can lead to vomiting and nausea

Inhalents

Gases and sprays
Taken by inhaling them
Neither stimulants or depressants
Common household items
Impair coordination, speech, and judgement
May cause hallucinations, confusion, seizures, brain damage, and sudden death.

Nicotine

Tobacco and vapes
Taken by swallowing, smoking, inhaling, chewing, or dipping.
Stimulant
Increases one nerve activity and heart rate
Highly addictive
Has withdrawal symptoms: cravings, irritability, and trouble sleeping.
Can cause cancer, strokes and lung diseases.

MDMA

Ecstasy and molly
Taken by swallowing or snorting
Stimulant
Causes ones energy to increase and ones vision to distort.
Feelings of euphoria and empathy.
Has become popular at night clubs and raves

GHB and Rohypnol

Date rape drugs
Ingested orally or in liquid or powder form as they have no smell or color.
Depressants
Cause the heart to slow down breathing, blood pressure, and eventually ones thoughts
.

Dissociative Drugs

Also known as ketamine
Taken by swallowing, snorting, injecting, or smoking.
Hallucinogen
May lead one to feel detachment from the body and its surroundings.
Can cause fever, seizures, comas, and/or death.

Psychedelics

LSD
Taken by swallowing, snorting injecting, or smoking.
Hallucinogens
Causes hallucinations and distortions in perception.
Intensify emotions and sensations.

Mouse Party

Marijuana:

Interferes with inhibitory and dopamine neutransmitters
Releases dopamine by binding to cannaboid receptors
Causes ones movements to slow down, causing one to feel calm and relaxed
May cause hallucinations, cravings, and sleepiness

Methamphetamine:

Interferes with dopamine neurotransmitters
Meth acts as dopamine causing receptors to work in reverse
Works on the brains reward pathway
Users feel intense pleasure and exhilaration

Ecstasy:

Interferes with serotonin neurotransmitters
Serotonin becomes confused and is trapped in the synaptic cleft
Over-stimulation
Mild release of dopamine
One becomes addicted to the feeling of euphoria, peace, and relaxation.

Heroine:

Interferes with inhibitory and dopamine neurotransmitters.
Mimics natural opiate
Causes well being and pain killing.
Highly addictive.
Euphoria and sedation.

Alcohol:

Interferes with GABA inhinitory and glutamate neurotransmitters.
Affects parts of the brain responsible for memory, decision making, and impulse.
At first one feels happy due to dopamine and serotonin release.
The next day one comes down from the "high" and feels sad, tired, and depressed.

LSD:

Interferes with serotonin neurotransmitters.
Mimics and binds to serotonin receptors.
Has sensory effects such as hallucinations in the locus coeruleus and other sensory areas of the brain.
Feelings of wakefulness and empathy.

Cocaine:

Interferes with dopamine neurotransmitters
Concentrates in the reward pathway
Active in the part of the brain that controls involuntary movement, therefore causing abusers to become fidgety and unable to be still.

Classification of Neurons

Sensory Classification

Structural Classification

Bipolar:

Two processes
Pretty rare, found commonly in the retina and olfactory
1 axon, 1 dendrite

Unipolar:

One "T-like" process
Two axons

Multipolar:

Three or more processes
CNS
1 neuron, other dendrites

Sensory:

Impulses from sensory receptors to CNS
Cell bodies in ganglia in PNS
Unipolar

Motor:

Impulses from the CNS to the effectors
Multipolar
Cell bodies in the CNS

Interneurons:

Between motor and sensory neurons
Found in CNS pathways
Association neurons

Na+ channels open
Depolarization occurs and action potential starts to take place.
Na+ channels close, K+ channels open
Re-polarization occurs.
K channels close and return to resting point.
Refractory period occurs (muscle fiber can't be stimulated for a certain amount of time not matter what).

Change in the membrane potential depolarization followed by a return to the resting membrane potential.
It occurs through the action across the membrane of the neuron.

Neurons:

Excitable cells
Receive and transmit nerve impulses
Requires oxygen and glucose
Amitotic with extreme longevity and are highly metabolic.
All have a cell body, axon, and dendrites

Neuroglia (glial):

Small cells wrapped around neurons
Supports neurons
Glial cells do not have axons or dendrites
Do not conduct nerve impulses

Ependymal:

Ventral cavity of the brain and spinal cord
May be cilia-ted
Form permeable barriers
Squamous to columnar

Oligodendrocytes:

Wrap NS nerve fibers into myelin sheaths
Branched

Microglial:

Migrate towards injured neurons
Transform microorg. and debris

Astrocytes:

Cling to neurons
Respond to chemical environments, impulses, and neurotransmitters
Star shaped
Touch and monitor
Most abundant

Meninges

Arachnoid Mater:

Has a spiderweb like appearance
Transparent = looks like saran wrap
Several layers thick
Under the dura mater
Surrounds most of the spinal cord
Meant to protect

Pia Mater:

Found directly around the brain
Under the arachnoid mater
Acts as a protective barrier
Produces cerebrospinal fluid

Dura Mater:

Thick protective layer of the brain and spinal cord
Outlayer
Closest to the skull
White in color

Integration

Processing and interpretation of sensory input

Motor Output

Activation of effector organs to respond (mucles and glands)

Sensory

Responds to internal and external environmental and chemical changes

Functions:

Two way communication
Reflex center
Carries messages between the brain and muscles.

Spinal Cord: Enclosed in vertebral column

Epidural Space: Fat cushion of veins between vertebrae and spinal dura mater (filled with CSF).
Filum Terminate: Fibrous extension of conus covered with pia mater (anchors and extends to coccyx).
Denticulate Ligament: Pia mater secures core to dura.
Spinal Nerves: Each spinal cord segment is designated by paired spinal nerves that arise from it.
Cauda Equina: Nerve roots at inferior end of vertebral canal.

Cervical (C1 - C7)
Thoracic (T1 - T12)
Lumbar (L1 - L5)
Sacral (S1 - S5)
Coccyx (tailbone)

Both have motor and sensory fibers and involve visceral and skeletal organs to activate muscles. However, they differ in:

1. Effectors
SNS: Skeletal muscle.
ANS: Cardiac muscle, smooth muscle, and glands.

Efferent Pathways and Ganglia
SNS: Single thick myelinated group from the spinal or cranial nerves to the skeletal.
ANS: Two-neuron chain
Preganglianic: Lightly myelinated that leads to preganglianic axon.
Postganglianic: Nonmyelinated that leads to effector organ.

Target Responses to Neurotransmitters
SNS: ACh - stimulation
ANS: NE to stimulate or inhibit

Third Ventricle

Protects
Carries nutrients and waste

Both Lateral Ventricles

CSF
Protection

Fourth Ventricle

Protects from truama

Are mostly mixed nerves (there are 31 of them)
Supply all body parts except neck and head.
Ventral Roots: Motor efferent fibers from the ventral horn neurons to the skeletal muscles. Their function is to stimulate.
Dorsal Roots: Sensory afferent fibers whose sensory neurons connect to the dorsal root ganglia. They are meant to conduct impulses.
Both roots branch medically as roolets.

Cerebral Palsy: Poorly controlled or paralyzed voluntary muscles due to brain damage and lack of oxygen at birth.
Anencephaly: Parts of the brain that never developed.
Spina Bifida: Incomplete formation of verterbral arches.
Multiple Sclerosis: Autoimmune disease which causes myelin sheaths in CNS to be destroyed.
Visceral Pain: Stimulation of visceral organ receptors.
Referred Pain: Pain from one region but perceived from another.
Autonomic Neuropathy: Damage to autonomic nerves.
Hypertension: High blood pressure
Raynauds Disease: Fingers turn pale and yellow then cyanotic.
Autonomic Dysreflexion: Blood pressure sky rockets, causing strokes.

Endoneurium:

Loose CT axons and schwann cells
Found around each individual nerve axon.
Maintains fluid pressure

Perineurium:

Coarse CT
Makes up bundles of nerves called fascicles.
Forms a barrier to protect nerves

Epineurium:

Tough sheath around each individual nerve.
Prevent nerves from injury while stretching