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neurons
specialized cells that transmit information through electrical and chemical signals. They are the building blocks of the nervous system and play a crucial role in processing and transmitting information
Excitable cells that contribute to the highly specialized cell function of nerve impulse transmission throughout the body.
Communicate with each other through synapses ( specialized junction between two nerve cells (neurons) or between a neuron and its target cell, such as a muscle or gland ) Two ways
Enabling the transmission of information and the coordination of various physiological and behavioral functions in the body
Has alot of help: Neuroglia, or glial cells, are non-neuronal cells that support, protect, and nourish neurons. Unlike neurons, they do not conduct nerve impulses but are essential for maintaining a healthy nervous system.
ion concentrations and fluids
must be in balance for optimal neural cell functioning.
sodium and potassium
These ions are essential for generating action potentials.
sodium-potassium pump
maintains the resting membrane potential by actively transporting Na⁺ out of the cell and K⁺ into the cell.
neuroglia (glial cells)
non-neuronal cells that support, protect, and nourish neurons. Unlike neurons, they do not conduct nerve impulses but are essential for maintaining a healthy nervous system.
sensory neurons (afferent neurons)
Carry signals from sensory receptors (e.g., skin, eyes, ears) to the central nervous system (CNS).
Detect stimuli such as temperature, pain, touch, and light.
motor neurons (efferent neurons)
Transmit signals from the CNS to muscles and glands, causing movement or secretion.
Two types:
Somatic – Control voluntary muscle movements.
Autonomic – Control involuntary functions (heart rate, digestion).
somatic motor neurons
Control voluntary muscle movements.
autonomic motor neurons
Control involuntary functions (heart rate, digestion).
interneurons (association neurons)
Connect sensory and motor neurons within the CNS.
Involved in reflexes, decision-making, and higher cognitive functions.
Make up most of the neurons in the brain and spinal cord.
neurotransmission
requires complex coordination between neural structures and the surrounding environment
It involves electrical and chemical signals to transmit information across the nervous system
How does it work?
Neurons communicate with other neurons and cells in the body by generating electrical signals called action potentials: This is the differences in electrical charge between the inside and outside the cell. This event travels across the entire neuron and allows neurons to communicate
Resting membrane potential
Depolarization phase
Repolarization phase
resting potential (neuron at rest)
The neuron maintains a negative charge due to the sodium-potassium pump actively moving Na⁺ out and K⁺ in.
The inside of the neuron is more negative than the outside, preparing it for activation
depolarization
Result of rapid movement of sodium into the cell through sodium channels in the plasma membrane. This inflow generates an electrical impulse. This impulse is transmitted along the axon to trigger the release of neurotransmitters
repolarization
After the peak of depolarization, the neuron needs to return to its resting state.
Voltage-gated potassium (K⁺) channels open, allowing K⁺ ions to flow out of the cell.
This restores the negative charge inside the neuron, ensures that the neuron can be ready for the next action potential.
electrical synapses
transmit impulses by passing current-carrying ions through small openings known as gap junctions.( protein channels that directly connect the cytoplasm of two neurons) .The transmission of electrical impulses through gap junctions is fast and direct. This mode of neurotransmission is multidirectional. Gap junctions are commonly involved in the transmission of electrical impulses that lead to cardiac contractions (fast and direct)
chemical synapses
impulses stimulated by neurotransmitters, though the synaptic cleft (tiny gap between the sending and receiving neurons) Use neurotransmitters carry signals between neurons and other excitable cells, including other neurons and muscle cells, to trigger a response in another cell (slow and highly regulated) muscles and glands .Complex processing and memory
chromatolysis
The swelling of a neuron because of injury
atrophy
Decrease in neuron size
generated
Unlike most other cells, new neurons are not _______ to replace those that have lost function through damage or death
Myelin that has been damaged is not replaced, leading to permanent neurologic deficit
The loss of neurons through cell damage or as a process of aging contributes to disability and is the basis for a variety of neurologic disorders.
80; ventricle; neurologic disorders; cataract
Developmental Considerations
By the age of 2 years, the brain is _% of its adult size
May have alterations in the nervous system due to decreased numbers of neurons, altered structure: due to age
Enlargement in the size of the _______ system
Decreased brain volume and weight
Increase in the appearance of _________________, such as stroke, Alzheimer disease, and Parkinson disease
Sensory changes, including _____ development, loss of focus, and diminished hearing, smell, and taste
central nervous system (brain and spinal cord)
Receives sensory information:
This gathers input from sensory organs (eyes, ears, skin, etc.) through peripheral nerves.
It processes sensations like touch, pain, temperature, and balance
Processes and Interprets Information
It handles cognition, memory, emotions, and learning.
Controls Movement and Reflexes
This sends motor signals to muscles and glands to control voluntary movements (walking, writing) and involuntary actions (breathing, heartbeat).
The spinal cord plays a major role in reflexes, allowing for quick, autonomic responses to stimuli (e.g., pulling your hand away from heat).
Coordinates Communication
This connects with the peripheral nervous system (PNS) to relay messages between the brain, spinal cord, and the rest of the body.
spinal cord
The nervous tissue of this is composed of both white and gray matter, based on the presence or absence of myelin (It has a gray matter center (where nerve cell bodies are located) and white matter around it (made up of nerve fibers for communication).
Parts:
Dorsal root brings sensory information into this.
Ventral root sends motor commands out of this to the muscles.
Sensory Information:
This receives sensory information from various parts of the body (skin, muscles, joints) and sends it to the brain for processing.
Motor Control:
This sends motor signals from the brain to muscles to control movements, whether voluntary (like walking) or involuntary (like breathing).
Reflexes:
It can trigger automatic reactions (reflexes) that help the body respond to certain stimuli quickly without involving the brain.
dorsal root of the spinal cord
brings sensory information into the spinal cord.
ventral root of the spinal cord
sends motor commands out of the spinal cord to the muscles.
peripheral nervous system
connects the CNS to limbs and organs, transmitting neural impulses via sensory pathways
Located outside of the boundaries of the CNS, the peripheral nervous system is not protected by the blood-brain barrier or bony support of the CNS, increasing the potential for damage due to toxic substances and mechanical injury
It’s job is to carry signals from the sensory organs (eyes, ears, skin) to the CNS, controls voluntary and involuntary movements. The cranial nerves and spinal nerves are part of this
somatic nervous system (SNS)
Function: Controls voluntary movements and transmits sensory information from sensory organs (like skin, eyes, and ears) to the brain.
Components:
Sensory (afferent) neurons: Carry sensory information from the body to the CNS.
Motor (efferent) neurons: Carry motor commands from the CNS to the skeletal muscles.
Example: Moving your arm or leg, feeling something hot or cold, or seeing an object.
autonomic nervous system (ANS)
Function: Controls involuntary functions, such as heart rate, digestion, respiration, and other functions of internal organs.
Components:
Sympathetic Nervous System: Activates the "fight or flight" response, preparing the body for stressful situations (e.g., increases heart rate, dilates pupils, etc.).
Parasympathetic Nervous System: Controls the "rest and digest" functions, helping the body relax and conserve energy(
sympathetic nervous system
Activates the "fight or flight" response, preparing the body for stressful situations (e.g., increases heart rate, dilates pupils, etc.).
parasympathetic nervous system
Controls the "rest and digest" functions, helping the body relax and conserve energy
neurocirculatory system
Interaction between the nervous system and circulatory system. Main vessels are carotid, vertebral and Circle of Willis (allows for blood flow, even if there is a blockage)
Blood–Brain Barrier -It protects by reducing permeability in capillaries that supply the brain, very selective of what comes in
Cerebrospinal Fluid- is a clear, colorless fluid that surrounds the brain and spinal cord system (CNS). It helps to cushion and protect the CNS from physical trauma, reduces pressure, transports hormones to remote parts of the brain
blood-brain barrier
It protects by reducing permeability in capillaries that supply the brain, very selective of what comes in
cerebrospinal fluid
is a clear, colorless fluid that surrounds the brain and spinal cord system (CNS). It helps to cushion and protect the CNS from physical trauma, reduces pressure, transports hormones to remote parts of the brain
traumatic CNS injuries
Traumatic Brain Injury
Traumatic Spinal Cord Injury
Ischemic CNS Injury
Excitation injury (Stroke, Seizures)
CNS Pressure Injury ( Increase ICP)
mechanisms of injury to the PNS
Traumatic Peripheral Nerve Injury
Peripheral Nervous System Pressure Injury
Peripheral Nervous System Motor Dysfunction
(Carpal Tunnel, Vascular injuries)
cerebral palsy (CP)
Group of disorders resulting from damage to upper motor neurons before, during or after birth
Signs are seen in the first few years of life
Central control of movement by the brain is altered
Cause is not fully known
Motor dysfunction classifications( movement, posture and muscle tone)
The timing and character of events during pregnancy and in labor may provide further evidence of cause of hypoxic–ischemic injury
Symptoms vary
Delay in milestones
Mild or severe disability
Limited fine motor
Lack of coordination and balance
Impaired cognitive function
Speech disorder
Seizures
cerebral palsy criteria
History & Physical
Neurologic exam
Motor skills
Evaluation of muscle tone
cerebral palsy treatment
Supportive treatment
Pharmacologic
Assistance devices
multiple sclerosis (MS)
Chronic autoimmune disease that affects the central nervous system
Pathophysiology is complex:
Immune system mistakenly attacks the myelin sheath
Immune cells, particularly T lymphocytes, infiltrate the CNS and trigger inflammation
The repeated cycles of inflammation and demyelination can lead to the formation of scar tissue or sclerosis
MS pathophysiology
Immune system mistakenly attacks the myelin sheath
Immune cells, particularly T lymphocytes, infiltrate the CNS and trigger inflammation
The repeated cycles of inflammation and demyelination can lead to the formation of scar tissue or sclerosis
MS signs/symptoms
Weakness
Numbness
Balance
Blurred vision
Dysphagia
Memory, Abstract reasoning
Depression
MS diagnostics
History and Physical
In depth neurology exam
Imaging- CT head, MRI/MRA
Labs- LP and CSF analysis
MS treatments
No Cure
Pharmacological and nonpharmacological treatment
incomplete spinal cord transection (ISCT)
Pathogenesis is related to the location, classification, type, and severity of the injury
Due to nerve root or myelinated tract damage, impairing the transduction of afferent or efferent neural impulses
Complete or Incomplete transection
Incomplete
Central Cord Syndrome
Anterior Cord Syndrome
Brown-Sequard Syndrome
Signs and Symptoms
Location
Classification
Severity
Diagnosis
Physical exam
Imaging studies
spinal cord injury treatment
Treat as a Trauma ( Board and collar to immobilize the spine)
Surgery
Promotion of functional abilities
parkinson’s disease
Chronic progressive neurologic
Degreeration of pigmented dopaminergic neurons of the basal ganglia
Impaired transport of dopamine
Presence of Lewy bodies (protein)
Neuronal injury from oxidative damage is suspected
parkinson’s signs/symptoms
Tremor
Rigidity
Jerky movements
Flat affect
Bradykinesia (slowed movement)
Shuffling gait and stooped posture
Postural instability
parkinson’s diagnosis
No single, definitive test exists to diagnose ___
Clinical findings based on the history and manifestations of the disease are used to diagnose.
Two commonly used scales for ________ _________ are the Hoehn and Yahr scale and the Unified P*******’s Disease Rating Scale.
Pharmacologic
Dopamine replacement (Levodopa)
Anticholinergics
Dopamine agonists
Surgical
Pallidotomy
Deep brain stimulation
pain
is complex
cannot be defined, identified, or measured by observer
is always a personal experience that is influenced to varying degrees by biological, psychological, and social factors.
This and nociception are different phenomena. This cannot be inferred solely from activity in sensory neurons.
Through their life experiences, individuals learn the concept of this.
A person’s report of an experience as this should be respected (ISAP, 2023)
pain origin
From our somatic senses of touch, pressure, vibration and pain
Complex sensory and emotional experience when the body detects harm to its tissues,
Nociceptors are specialized sensory nerve endings found in most tissues (skin, joint, organs)
These receptors respond to the stimulus that caused damage (mechanical, thermal, chemical)
When they are stimulated, they send electrical signals to the brain and spinal cord
pain mechanics
This organization allows for the relay and integration of sensory signals at different levels, from the periphery to the central nervous system (CNS) and finally to the brain
First order - This is the initial neuron that detects and transmits from peripheral receptors (nociceptors) to the spinal cord or brainstem.
Second order - Second-order neurons receive input from first-order neurons and transmit this information to higher brain centers. Go to the thalamus or medulla
Third order - receive input from second-order neurons and transmit the processed sensory information to the cerebral cortex for conscious perception ( it’s perceived or felt)
first-order neurons
This is the initial neuron that detects and transmits from peripheral receptors (nociceptors) to the spinal cord or brainstem.
second-order neurons
receive input from first-order neurons and transmit this information to higher brain centers. Go to the thalamus or medulla
third-order neurons
receive input from second-order neurons and transmit the processed sensory information to the cerebral cortex for conscious perception ( it’s perceived or felt)
types of pain
Acute- Last hours or day and resolves with healing
Chronic- Beyond expected time:, can be due to persistent inflammation, does not serve a biological or protective function > 3-6 months
Chronic __ can profoundly affect quality of life (Produces behaviors and physiological changes)
Neuropathic __ is due to an injury or malfunction of nervous tissue (burning, tingling, paresthesia)
Cutaneous refers to __ that originates from the skin or superficial tissues of the body. It is typically caused by damage or irritation to the skin's surface, such as from a cut, burn, or abrasion
Deep somatic is a type of ___ that originates from deeper tissues within the body, such as muscles, joints, bones, ligaments, and tendons.
Visceral is __ that originates from internal organs (such as the stomach, intestines, liver, or lungs) and is typically associated with deep, internal structures within the body. It is often caused by distension, inflammation, ischemia, or injury to the organs. (kidney stones, gallstones, appendicitis)
Referred is __ felt in a different part of the body than where it originates (e.g., heart attack pain in the arm).
Phantom is __ felt in a missing limb or body part after amputation, due to the brain's continued processing of sensory signals.
You need to know __ type to treat it!!
acute pain
Last hours or day and resolves with healing
chronic pain
Beyond expected time:, can be due to persistent inflammation, does not serve a biological or protective function > 3-6 months
can profoundly affect quality of life (Produces behaviors and physiological changes)
neuropathic pain
due to an injury or malfunction of nervous tissue (burning, tingling, paresthesia)
cutaneous pain
refers to pain that originates from the skin or superficial tissues of the body. It is typically caused by damage or irritation to the skin's surface, such as from a cut, burn, or abrasion
deep somatic pain
type of pain that originates from deeper tissues within the body, such as muscles, joints, bones, ligaments, and tendons.
visceral pain
pain that originates from internal organs (such as the stomach, intestines, liver, or lungs) and is typically associated with deep, internal structures within the body. It is often caused by distension, inflammation, ischemia, or injury to the organs. (kidney stones, gallstones, appendicitis)
referred pain
pain felt in a different part of the body than where it originates (e.g., heart attack pain in the arm).
phantom pain
pain felt in a missing limb or body part after amputation, due to the brain's continued processing of sensory signals.
infection
a state of cellular, tissue, and sometimes even organ destruction resulting from invasion by microorganisms (microbes)
Remember, if they get pass the three lines of defense, infection will happen
microbes
including bacteria, viruses, fungi, and protozoa, are everywhere in the human environment
Resident flora are microorganisms that live on or within the body in non sterile areas, such as the skin, mucous membranes, bowel, rectum, or vagina, without causing harm (these are fine unless broken)
pathogens
a disease-causing microbe
To cause disease in humans, they must be capable of binding to specific receptors on the human host cell (this provides clues)
(Influenza virus attaches to receptors only in respiratory tract epithelial cell)
How do they cause disease?
Direct destruction of the host cell by these
Interference with the host cell’s metabolic function
Exposing the host cell to toxins produced by these
pathogenicity
Qualities that promote the production of disease
Ways it can cause disease:
Virulence: A more virulent microorganism is one that causes severe disease in a large proportion
Toxigenicity: Ability of the pathogen to produce harmful toxins that increase host cell and tissue damage
Antigenic variability: mutate or change
Coinfection : Simultaneous occurrence of hosting two or more pathogens
Superinfection is an infection that arises in addition to one that is already present
virulence
A more ____ microorganism is one that causes severe disease in a large proportion
toxigenicity
Ability of the pathogen to produce harmful toxins that increase host cell and tissue damage
antigenic variability
mutate or change
coinfection
simultaneous occurrence of hosting two or more pathogens
superinfection
an infection that arises in addition to one that is already present
bacteria
single-celled microorganisms classified as prokaryote
Lacks a distinct membrane-bound nucleus
Reproduce outside of host cells
Those that require oxygen for growth are called aerobic; those that do not are called anaerobic ( how they require oxygen, tells you where they do the best at) - Anaerobic in deep tissue - hard to treat
These are described by their shape
rigid; synthesis; human cells
Bacteria have a ___ cell wall ( provides structure, shape, and protection)
Without it, the bacteria cannot survive in certain environments
Many antibiotics are designed to interfere with the ____ or function of the bacterial cell wall
_______ do not have a cell wall, so antibiotics that target the bacterial cell wall typically don't harm _________.
gram-positive and gram-negative bacteria
have different types of cell walls. GP bacteria have a thick cell wall, while GN bacteria have a thinner wall but an additional outer membrane
They are stained in the lab
Use blood cultures to identity the bacteria
This is how antibiotics are chosen
viruses
Cannot replicate outside of the host cell
Binds to specific receptors on the host cell and then moves into the host cell
Ability to either directly kill the cell or modify certain cellular functions, such as protein synthesis (it takes over to replicate)
Cell ultimately loses its ability to function. The virus next releases particles outside of the cell, called virions, which can enter and infect other nearby cells
As it moves, the immune response is activated. This exaggerated immune response allows neutralization of the virus and resolution of the infection
Infected host cells are eliminated, and the virus can no longer replicate (common cold)
chronic virus
(if not a good immune response)
The size of the virus that is inoculated into the body
The process of viral replication
The viral genotype
Host susceptibility
Period of latency (will stay dormant until a patient is immunocompromised)
Example of latency: herpes simplex infection
fungi (molds and yeast)
Large organisms compared to bacteria and viruses. They have a nuclear membrane, cytoplasm, and organelles
Superficial or deep tissue invasion occurs when molds or yeast multiply. This invasion results in inflammatory and immune responses
Inhabit the skin surface or mucous membranes and are controlled by intact integument, inflammatory, and immune cell
Opportunistic pathogens are those that cause disease only in a host with a compromised immune system
As previously mentioned, reduction of resident bacteria, often via antibiotics, disturbs this balance and allows f**** overgrowth
candida
One of the most common opportunistic yeast infections involves ____
_______ cutaneous invasion include skin redness, itching, and burning at the site. In oral candidiasis, lesions are white and resemble cottage cheese attached to an erythematous oral cavity
Lesions bleed easily and can be painful if scraped Vulvovaginal candidiasis also produces redness, itching, and burning at the site along with a thick, white, vaginal discharge
communicable diseases
infections that are spread from person to person, often through contact with infected blood and body fluids
Although all of these are infectious, not all infectious diseases are communicable
These are caused by microorganisms that live and reproduce in a human host
chain of infection
Reservoir: Include an infected person, an animal, or the environment, such as pond water
Portal of Exit: In human hosts, common portals of exit include the respiratory tract, GI tract, skin, mucous membranes, placenta, and blood
Portal of Entry: Access point for the microorganism into the host, or the individual who is exposed to, and contracts the infection.
Mode of Transmission: This contact can be direct or indirect. The mode of transmission refers to the mechanism of transference from the reservoir to the portal of entry. The modes of transmission include:
reservoir
Include an infected person, an animal, or the environment, such as pond water
portal of exit
In human hosts, common portals of exit include the respiratory tract, GI tract, skin, mucous membranes, placenta, and blood
portal of entry
Access point for the microorganism into the host, or the individual who is exposed to, and contracts the infection.
mode of transmission
This contact can be direct or indirect. This refers to the mechanism of transference from the reservoir to the portal of entry. These include:
Direct contact
Droplet transmission: Larger respiratory particles, produced by sneezing, coughing, or talking, can pass through the air from the reservoir to the host (Respiratory)
Airborne transmission: Smaller respiratory particles can remain suspended in the air and are subject to airborne transmission (chicken pox & TB)
Vector transmission: A vehicle that harbors the pathogen and carries it to the host (mosquitoes)
droplet transmission
Larger respiratory particles, produced by sneezing, coughing, or talking, can pass through the air from the reservoir to the host (Respiratory)
airborne transmission
Smaller respiratory particles can remain suspended in the air and are subject to airborne transmission (chicken pox & TB)
vector transmission
A vehicle that harbors the pathogen and carries it to the host (mosquitoes)
acute infection phases
1. Exposure: Exposure is contact with the pathogen through any of the modes of transmission
2. Incubation: The incubation phase extends from exposure to the onset of any signs or symptoms
3. Prodrome: The specific signs and symptoms related to the disease have not yet emerged
4. Clinical illness: Represents the signs and symptoms specific to the disease
5. Convalescence: Extends from waning clinical manifestations to full recovery from the disease
exposure
contact with the pathogen through any of the modes of transmission
incubation
This phase extends from exposure to the onset of any signs or symptoms
prodrome
The specific signs and symptoms related to the disease have not yet emerged
clinical illness
Represents the signs and symptoms specific to the disease
covalescence
Extends from waning clinical manifestations to full recovery from the disease
complications of infection
Acute infection can result in two major complications: septicemia and chronic infection
Septicemia occurs when microorganisms gain access to the blood and circulate throughout the body. When septicemia is caused by bacteria, the term bacteremia is often used.
Septic shock is a process of systemic vasodilation due to severe infection, often with Gram-negative bacteria
Chronic infection is defined as an infection that lasts for several weeks to years.
septicemia
occurs when microorganisms gain access to the blood and circulate throughout the body. When this is caused by bacteria, the term bacteremia is often used.
septic shock
a process of systemic vasodilation due to severe infection, often with Gram-negative bacteria
chronic infection
defined as an infection that lasts for several weeks to years.
influenza
a viral infection of the airway epithelial cells
The virus is transmitted via respiratory droplets from another infected person or contaminated surface
Three different types of these viruses (A, B, or C)- this is why you get it more than once
This virus enters the respiratory tract; attaches to the surface epithelial cells; impairs cilia, mucus, and antibodies; protein helps release new viral particles from infected cells.The infection spreads to neighboring cells, damaging the respiratory epithelium.
Can be a problem in a patient who is immunocompromised
influenza clinical manifestations
Cough, sore throat, nasal congestion and drainage, and shortness of breath
Systemic signs and symptoms of inflammation are also common and include chills, fever, body aches, weakness, and malaise.
influenza diagnostics
Usually based on history and symptoms
Nasopharyngeal secretions are quick (10 to 20 minutes) but can be false positive