Nervous System - Overview Flashcards
A patient reports that they are having trouble moving ONE hand. In which system is the problem most likely coming from?
A) Nervous system
B) Endocrine system
C) Reproductive system
A) Nervous system
There must be an issue in the nervous system so that no nerve can be fired to the muscle tissue/NMJ to contract the muscle
Because the problem is so localized (only ONE hand is affected), this is an indication that it is coming from the nervous system, because the nervous system is highly specific
Why isn’t it the other systems?
B) Endocrine system - hormone problems would affect both hands, and not just one hand
C) Reproductive system - does not have any correlation to moving one hand(?)
If someone is unable to move their hand, why would you get out a hammer and nail?
To gently tap the patient’s immobile hand with the hammer and nail to see if they react to it (SENSATION)
Or more specifically to see if they have REFLEX
Testing for SENSATION and REFLEX
What are the main function of the nervous system? Describe some characteristics of the nervous system
- Coordinate the rest of the body
- specialized for rapid and specific information transfer
- highly specific and localized
- tells the body what to do
- direct immediate and delayed responses to stimuli, usually by coordinating the activities of other organ systems
One of the two organ systems that tells the body what to do (nervous system and endocrine system)
Describe the gross anatomy of the nervous system
Hub & Spoke Organization
- long peripheral nerves running to and from the brain and spinal cord to specific locations
- central nervous system consists of the brain and spinal cord
- branches out with nerve endings going in and out of the hub
Describe the histology of the nervous system
Neurons
- interconnected cells with really long processes/projections make up all parts of the nervous system
There are two ways to divide the nervous system: What are they?
Anatomically and functionally
What are the three ANATOMICAL components of the nervous system?
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
- Enteric Nervous System (ENS)
What is the Central Nervous System? (CNS)
- found within the vertebrae and cranial bones = BRAIN AND SPINAL CORD
- enclosed within bony shells
- information processing, integrates, processes, and coordinates sensory input
and motor commands
What is the Peripheral Nervous System? (PNS)
- outside the skull and spine, but directly connected to the CNS
- leaves the CNS, but every part of the PNS has a direction connection to the CNS
- includes all the nervous tissue outside
the CNS, except for that of the ENS - PNS carries motor commands from the
CNS to peripheral tissues and systems - contains the somatic and autonomic nervous system
What is the Enteric Nervous System? (ENS)
- neural cells within the DIGESTIVE SYSTEM which only indirectly connect to the CNS via the PNS
- separate set of neurons that embedded in the walls of digestive organs that aren’t directly connected to the CNS
- distinguished from the PNS nerves because they can operate independently
Differentiate the CNS from the PNS
CNS - BRAIN AND THE SPINAL CORD
- houses the vast majority of all neuronal cell bodies and their processes
- carries most of the weight of the nervous system
PNS - PERIPHERAL NERVES AND GANGLIA
Which parts of a neuron are in the CNS and which parts are in the PNS?
CNS: Brain
Contains more neurons than the spinal cord
CNS: Spinal cord
Contains most connections with the PNS
PNS: Nerves
Collections of long neuronal processes interacting with non-neuronal cells/organs
- go everywhere / long skinny projections
PNS: Ganglia
Groups of cell bodies outside the CNS
- bulges on nerves outside of the CNS
- group of cells
What are the three FUNCTIONAL classes of the nervous system?
- Sensory neurons (RECEPTORS) - afferent neurons
- Interneurons (INTEGRATORS) - spinal cord processing
- Motor neurons (EFFECTORS) - efferent neurons
What are sensory neurons?
Receptors
- passes information FROM OUTSIDE INTO the nervous system
- take info from outside the nervous system inside
- receives the information
What are receptors?
Receptors are sensory structures that detect changes in the internal or external environment
What are interneurons?
Integrators
- pass information between other neurons
- receives info from neurons and pass it to another neuron
- vast majority of neurons in the nervous system are interneurons
- only interact with other neurons
What are integrators?
Integrators are the brain and spinal cord
The brain functions in interpreting the messages from the nervous system
The spinal cord plays a role in relaying the information from the brain and different parts of the body
What are motor neurons?
Effectors
- pass information from neurons TO NON-NEURONAL CELLS
- receives info from interneurons and passes it to non-neuronal cells
- make other organs/tissues of the body do something
What are effectors?
Effectors are target organs and tissues that
respond to neural motor commands
Trace the path of a reflex arc
- Stimuli/receptor
- Sensory neuron
- Interneuron
- Motor neuron
- Effector/tissue/organ
How does the nervous system process and transfer information?
The nervous system uses electrical signals within excitable cells and chemical signals between cells
- receiving and passing along information from non-neurotic cells to neurons, neurons to neurons, and from neurons to non-neurotic cells
- modifies, filters, and integrates information
Match the following with the correct functional class of the nervous system:
- Receptor
- Effector
- Integrator
- Receptor
- sensory neuron - Effector
- motor neuron - Integrator
- interneuron
Where are electrical signals used?
Within excitable cells
Where are chemical signals used?
Between excitable cells
What are electrical signals?
- brief changes in the transmembrane potential of the plasma membrane
- two types: graded potential and action potential
- travels up and down the plasma membrane, passing information from one end of the cell to the other (WITHIN CELLS)
What are chemical signals?
- release of neurotransmitters into synapses (gaps) between neurons
- neuron communicating to another cell via sending neurotransmitters
- BETWEEN CELLS !!
Ex: ACh is a neurotransmitter
How are action potentials different from graded potentials?
Action potential - short, sharp, spike
- a rapid sequence of changes in the voltage across a membrane
- associated with the ratios of ions inside/outside of the membrane
- occurs down the axon away from the cell body
Graded potential - changes in the membrane potential that vary in size
- different shapes, sizes, and directions
- involving dendrites and cell bodies
Where do action potentials take place? Where do graded potentials take place?
AP
- occur down the axon, away from the cell body
GP
- occur in dendrites, cell bodies, or axon terminals
Differentiate electrical signals from chemical signals
in a chemical synapse, the nerve impulse is transmitted chemically via neurotransmitters
- BETWEEN CELLS
in an electrical synapse, the nerve impulse is transmitted electrically via channel proteins
- WITHIN CELLS
True or False: The term CNS refers to the brain and the brainstem
FALSE
- the brainstem is part of the brain
- the CNS refers to the brain and the spinal cord
True or False: The PNS is one of three functional divisions of the NS
FALSE
- the PNS is one of the ANATOMICAL divisions of the NS
- the three FUNCTIONAL classes of the NS include sensory neurons, interneurons, and motor neurons
True or False: Skeletal muscles are the organ system in the body that can be directly controlled by neurons
FALSE
- the nervous system can also control non-skeletal muscles such as the heart (cardiac muscle)
- it can control all three types of muscle tissue (skeletal, cardiac, and smooth)
- it can control any organ system
True or False: Interneurons are primarily found within the CNS
TRUE
- most neurons are found in the CNS
- enclosed in bony shells to protect the neurons
True or False: A nerve is not the same thing as an individual neuron
TRUE
- a nerve is a bundle of neurons
- made up of parts of neurons
- but they are not neurons
True or False: Action potentials are electrical signals that pass information across the gaps between neurons
FALSE
- electrical signals pass information within cells from one end to the other
- in the neuron, specifically the axon
- chemical signals pass information from cell to cell (between cells)
What are the two classes of cells in the nervous system?
- Neurons
- Neuroglia
What are neurons?
- a type of nerve cell which transmits information
- the principal cells of nervous tissue
- longest cells of the body
- made of 4 major structural components
- neurons have neurites
Neurons are nerve cells that send messages all over your body to allow you to do everything from breathing to talking, eating, walking, and thinking
What are neuroglia?
- play numerous supporting roles
- also known as glial cells
The neuroglia are a diverse class of cells that provide developmental, physiological, and metabolic support for neurons
What are neurites?
elongated cell processes/projections found in neurons
- includes the dendrites and axon
- make up neurons
What are the 4 structural components/major regions of a neuron?
- Dendrites
- Cell body (soma containing nucleus)
- Axon
- Axon terminals
What are glial cells?
- makes up half of all cells in nervous tissue
- protect and maintain neurons
- play supporting roles
- also act as glue to glue neurons together
What is dendrite? (Characteristics)
- receives inputs from other cells
- typical dendrites are highly
branched, with each branch bearing
fine/short processes called dendritic spines - CNS neurons receive most of their information primarily at the dendritic spines
What is a cell body/soma? (Characteristics)
- receives inputs and produces proteins
- contains organelles that provide
energy and synthesize the chemical
neurotransmitters that are important
in cell-to-cell communication - tends to also receive inputs from other cells
- houses the nucleus and ribosomes
- makes proteins and expresses genes
- proteins made must be shipped
What is an axon? (Characteristics)
- transmits action potentials to next cell
- longest, only one that comes off the soma
- made of four components
- where the action potential is actually generated
- long cytoplasmic process that extends away from the cell body
What is the longest neurite?
The longest neurite is almost always the AXON
- axis neurite
Neurons are highly ________ cells with different cell compartments specialized for different functions
Neurons are highly POLARIZED cells with different cell compartments specialized for different functions
What is an axon terminal? (Characteristics)
- converts action potentials to chemical signals
- allows for the passage of info from one neuron to the next
- takes AP to the axon terminals
- specializations where chemical signaling happens
- release of chemicals across the gaps to the next neuron
Differentiate dendrites, axons, and cell bodies
Dendrites - receive stimuli from the
environment or from other neurons
Cell bodies - contains the nucleus and
other organelles
Axons - carries information toward other cells
What are the four components of an axon?
- Axon hillock
- origin of the axon from the cell body - Axon initial segment
- lies distally adjacent to the axon hillock
- where an action potential is initiated. - Axolemma
- specialized portion of the plasma membrane that surrounds the cytoplasm (axoplasm) of the axon - Axoplasm
- cytoplasm for nerve cells
- contains neurofibrils, neurotubules,
small vesicles, lysosomes, mitochondria,
and various enzymes.
Information flow within a neuron is __________________ from dendrite to axon to axon terminal
UNIDIRECTIONAL
What does it mean that information flow in a neuron is unidirectional?
dendrite -> axon -> axon terminal
1. sensory neuron
2. interneuron
3. motor neuron
- information only travels in one direction
What are the three ways to classify neurons?
- Classified anatomically based on neurite arrangement
- They could be classified with the type of neurotransmitter that they carry
- Classified functionally based on which organ system they are connected to
- shape
- location
- type of chemical released
What are the four classes of neuron types?
- Multipolar
- Bipolar
- Pseudo-unipolar
- Anaxonic
What are multipolar neurons? (Characteristics)
- many (2+) dendrites and only one axon
- axons can branch later on but there is only one that comes off the soma
- most common type in the CNS
- axons of multipolar
neurons can be as long as
those of unipolar neurons
The longest carry motor commands
from the spinal cord to small
muscles that move the toes
What are bipolar neurons? (Characteristics)
- one dendrite and one axon
- two distinct processes—one
dendritic process that branches
extensively at its distal tip, and one
axon—with the cell body between
the two - rare but occur in special sense organs,
where they relay information about sight, smell, or hearing from receptor cells to other neurons - small
What are pseudo-unipolar neurons? (Characteristics)
- one axon connected to the soma but the dendrite connects to the axon
- include sensory neurons in the PNS (most in the PNS are unipolar)
- dendrites and axon are continuous—basically, fused—and the cell body lies off to one side
- have very long axons
The longest are those carrying
sensations from the tips of the toes to the
spinal cord.
What are anaxonic neurons? (Characteristics)
- many neurites that act as both dendrite and axon terminals
- VERY RARE
- small and lack anatomical features that distinguish dendrites from axons; all the cell processes look alike
- functions are poorly understood
Give an example of a multipolar neuron
Most common type of neuron in the CNS
Give an example of a bipolar neuron
Found in the retina of the eye, the roof of the nasal cavity, and the inner ear
Give an example of a pseudo-unipolar neuron
Spinal and cranial nerve ganglia
Give an example of an anaxonic neuron
Interneurons seen in the ganglia of the motor systems of various arthropods, including crayfish, locusts and cockroaches
How many types of neurotransmitters can a neuron release?
Each neuron can only release one single type of neurotransmitter at its axon terminals
- a neuron can be attached to multiple axon terminals, but they will all release the same type of neurotransmitter chemical
Different neuronsnsmitter effects depend on the ____________present on the next cell.
Different neurons release DIFFERENT neurotransmitters.
Transmitter effects depend on the RECEPTORS present on the next cell
What are the 8 most common/notorious neurotransmitters and what do they do?
- Noradrenaline/Norepinephrine - regulation of arousal, attention, cognitive function, and stress reactions; concentration
- Adrenaline/Epinephrine - “fight or flight” response, produced in stressful/dangerous situations
- Dopamine - chemical released in the brain that makes you feel good (temporary)
- Serotonin - controls your mood and is responsible for happiness (long-lasting)
- Gaba - calming effect, low levels cause anxiety, high levels improve focus
- Glutamate - memory neurotransmitter
- Acetylcholine - learning neurotransmitter, activates muscles in body
- Endorphins - euphoria neurotransmitter, reduces pain, sensation
What are the two subdivision systems of the peripheral nervous system?
- Somatic nervous system
- Autonomic nervous system
What is the somatic nervous system?
- motor neurons innervating skeletal muscles
- mostly about the motor system involving the skeletal muscle
- motor neurons -> axon terminals -> skeletal muscles to make it contract
- operates in circuits
Ex: sensory neurons in the skin, joints, muscles looking at the integument and skeletomuscular system
What is the visceral/autonomic nervous system?
- motor (effector) neurons innervating tissues OTHER THAN skeletal muscles
- sensory neurons innervating visceral organs
Ex: heart, lungs, liver, pancreas, etc.
- affecting smooth muscle, cardiac muscle, glands, adipose / squishy organs
Differentiate the somatic nervous system from the autonomic nervous system?
Somatic = skeletal muscles
Autonomic = smooth muscle, visceral organs, cardiac muscles, etc.
What are the two subdivisions of the autonomic nervous system?
- Parasympathetic division
- Sympathetic division
Which neurotransmitter is involved in the parasympathetic division? Sympathetic division?
Parasympathetic division?
- acetylcholine
- rest and digest
Sympathetic division?
- norepinephrine
- fight or flight
True of False: The somatic nervous system is voluntary and the autonomic nervous system is involuntary.
FALSE
Autonomic nervous system IS INVOLUNTARY because you cannot control it and the actions are unconscious
BUT the somatic nervous system is not automatically assumed to be voluntary
True or False - Explain why.
“The somatic nervous system creates voluntary movements and the autonomic nervous system creates involuntary movements.
The somatic nervous system can play a role in regulating voluntary movements, but it is also involved in involuntary movements such as reflexes.
When your muscles react and there is a reflex, this is an involuntary movement produced by the somatic system.
On the other hand, the autonomic
nervous system, we have no control over the ANS
What are the four types of glial cells found within the nervous system?
- Ependymal cells
- Microglia
- Myelinating cells
- Astrocytes/satellite cells (metabolic-support cells)
What are ependymal cells?
- form a simple cuboidal columnar epithelium (ependyma)
- lines fluid-filled passageways within the spinal cord and brain
- cerebrospinal fluid (CSF) fills these cavities
- assist in producing, monitoring, and circulating the CSF
What are microglia?
- developmentally related to monocytes and macrophages
- migrate into the CNS as the nervous system forms
- persist as mobile cells moving through the nervous tissue, removing cellular debris, wastes, and pathogens by phagocytosis
What are myelinating (oligodendrocytes) cells?
- provide a structural framework within the CNS by stabilizing the positions of axons
- produce myelin and myelin sheaths
- myelination allows electrical signals to travel rapidly and efficiently in axons
There are two distinct types of myelinating cells:
a) Schwann cells
b) Oligodendrocytes
What are astrocytes?
- maintain blood-brain barrier that isolates the CNS from the chemicals and hormones circulating in the blood
- provide structural support within nervous tissue
- regulate ion concentrations in ECF
- regulate local blood flow (oxygen and nutrient supply)
- regulate flow of CSF
- absorb and recycle/buffer neurotransmitters that are not broken down or reabsorbed at synapses
- form scar tissue after CNS injury
- regulate the extracellular environment around neurons, and maintain/modify synaptic connections
What is cerebrospinal fluid (CSF)?
- cerebrospinal fluid becomes the extracellular fluid in the CNS
- washes neurons free of toxicity because neurons generate a lot of waste and secrete weird stuff LMFAO
- bathes and cushions the brain from banging into the cranium
- fills the internal spaces and surrounds the brain and spinal cord
What is the blood-brain barrier?
layer of cells that shields the brain from toxic substances in the brain
What is myelin?
FAT AND PROTEIN
- fat insulating sheath for the axons of the neuron
- a membranous wrapping around axons that greatly increases the transmission speed of nerve impulses
- when myelinating an axon, the tip of oligodendrocyte process expands to form a wide pad that gets wound around the axon, forming concentric layers of plasma membrane
- layers create a myelin sheath
Which two types of glial cells are found inside the CNS?
- Ependymal cells
- Microglial cells
ONLY FOUND IN THE CNS AND NOT THE PNS
Describe the inside of the nervous system (canals/ventricles/etc)
There is a fluid-filled passageway within the spinal cord and the brain
The passageway narrows in the spinal cord and is called the CENTRAL CANAL
In the brain, the passageway forms cavities called ventricles -> ventricles run all the way through the CNS, are filled with fluid, and have cavities lined with ependymal cells
Cerebrospinal fluid (CSF) fills these internal spaces and also surrounds the brain and spinal cord
Summarize ependymal cells, microglia, oligodendrocytes/myelinating cells, and astrocytes/satellite cells
Ependymal cells - line ventricles and secrete cerebrospinal fluid, which bathes and cushions CNS
Microglia - white blood cells which perform immune functions for the CNS and also help modify connections between neurons
Oligodendrocytes - wrap cellular processes containing myelin around the axon of neurons
Astrocytes/satellite cells -provide diverse forms of metabolic and physiological support
True or False: All neurons are myelinated
FALSE
Where are myelinating cells found?
Myelinating cells provide electrical insulation in BOTH THE CNS AND THE PNS
What are the two distinct types of myelinating cells and where are they found?
- Schwann cells - PNS
- Oligodendrocytes - CNS
Differentiate Schwann cells from Oligodendrocytes?
Schwann cells
- make myelin to wrap around axons
- same function as oligodendrocytes
- different location
- PNS
Oligodendrocytes
- make myelin to wrap around axons
- same function as schwann cells
- different location
- CNS
What are satellite cells?
- play a role in metabolic and physiological support
- do most of the same things as astrocytes but in the PNS instead
How do astrocytes differ from satellite cells?
satellite cells are NOT found in the CNS, and cannot produce CSF
- satellite cells are found in the PNS
astrocytes are found in the CNS
True or False: There are about 9-10 glial cells for every neuron in the CNS
FALSE
There is only 1 glial cell for every neuron
True of False: Astrocytes support dendrites, axon terminals and cell bodies, while satellite cells support axons
FALSE
Schwann cells support axons (producing myelin for myelinating axons)
Astrocytes and satellite cells support the dendrites and soma
(astrocytes in the CNS and satellite cells in the PNS)
True or False: Myelin sheaths in the CNS are formed by oligodendrocytes while myelin sheaths in the PNS are formed by Schwann cells
TRUE
True or False: Microglia are a brain-specific type of epithelial cell
FALSE
Microglia are blood cells (connective cells)
True or False: Action potentials are shared between neurons and myelinating glia, but not other types of glia
FALSE
Only neurons can make action potentials, no glia can make action potentials
Other cells in the body, such as muscle cells are also capable of producing action potentials though
Can a neuron be repaired or replaced if it is damaged? Can nervous tissue be repaired/replaced?
NO!!
New neurons CANNOT be born into adulthood
- if a neuron dies, IT WILL NOT BE REPLACED WAA WAA
True or False: Nervous tissue CAN be repaired or replaced if it dies/is damaged
FALSE
New neurons cannot be born in adulthood
If a neuron dies, it will not be replaced
What are the three ways that neurons die?
- Physical trauma to cell body
- Excitotoxicity (excessive excitatory synaptic activity) aka NEURON DEATH
- Severing an axon
What happens during neuron death?
Neuron death happens during a stroke
If a neuron is too active electrically, it sends too many electric signals per unit time and it actually gets itself into a state where it commits apoptosis and it just chooses to die
(omg so relatable bestie)
What happens when an axon is severed?
- if you cut the axon from the neuron, it will die
- if the axon is severed FAR AWAY from the cell body, it might not die
- there is a chance that the axon will regrow if it was cut far from the cell body YIPPEE
What does it mean for neurons to be post-mitotic?
It means that they CANNOT RETURN TO THE CELL CYCLE
- they cannot replace themselves if they die
What happens after a neuron dies? What cell comes to clean up the mess?
MICROGLIA (white blood cells) remove the remains of dead neurons (YUM)
Differentiate neuron regeneration in the CNS and the PNS
CNS - neurons CANNOT spontaneously regenerate themselves
PNS - neurons/axons in the PNS can repair and regrow with the help of local glia
Only axons in the _______ nervous system can repair and regrow with the help of local glia if damaged
PERIPHERAL NERVOUS SYSTEM
- everything distal to the cut will die, but anything proximal to the cut may be able to repair/regrow
What kind of glial cell helps with the regeneration/repair of axons in the PNS?
Schwann cells promote axon regrowth!!
Recall: Schwann cells are found in the PNS and oligodendrocytes are found in the CNS
If an axon in the _________ nervous system is damaged, it typically CANNOT REPAIR OR REGROW
CENTRAL NERVOUS SYSTEM
Describe what happens when an axon is damaged in the CNS
- An axonal injury occurs
- There is no macrophage to clear the debris
- Astrocytes secrete inhibitory molecules that stop axon sprouting / shuts it off / cannot repair an axon in the CNS
- If an axon is severed in the CNS, it will detect that change after a while and then the neuron will die
- Glial cells actively stop it from repairing itself
= NO AXON REGENERATION!!
What are the CNS and PNS composed of?
Both the CNS and PNS are composed of nervous tissue (neurons and glia)
Everything in the CNS can be divided into white matter and grey matter
What is grey matter?
Grey matter INTEGRATES SENSORY AND MOTOR FUNCTIONS
- shows functional segregation
- neighbouring cells/axons usually process/carry similar information
- grey matter at different locations of the brain/spinal cord do different things
- contain astro/micro-glia cells
- contains neuron cell bodies / axon terminals
- functional area with neurons passing info
- synapses between neurons
What is white matter?
White matter CARRIES INFORMATION
- exclusively consists of myelinated axons (FAT) connecting one region to another
- no cell bodies
- no synapses
- only axons which are the transmission lines take info from one to another
Where is white and grey matter found?
in the CENTRAL NERVOUS SYSTEM (the brain and the spinal cord)
BRAIN
- outer cortex = grey matter
- closer to the centre of the brain = white matter
SPINAL CORD
- horn like shape in the centre = grey matter
- surrounding space = white matter
Compare and contrast grey and white matter
GREY MATTER
- made of neuronal cell bodies
- place where the processing of sensation, perception, voluntary movement, learning, speech and cognition takes place
WHITE MATTER
- made up of large networks of nerve fibers (axons)
- allow for the exchange of info and communication between different areas of the brain (grey matter to grey matter)
- nerve fibers/axons are covered in myelin sheath
Describe neural circuits throughout the nervous system:
Predictable or no?
Involuntary or voluntary?
The anatomy of neural circuits in the nervous system are HIGHLY PREDICTABLE
They support INVOLUNTARY REFLXES and CONSCIOUS/VOLUNTARY CONTROL
What does white matter in the spinal cord do?
Spinal cord white matter relays sensory and motor information to and from the brain
What does grey matter in the spinal cord do?
Circuits in the spinal cord grey matter are necessary and sufficient for simple reflexes, such as the withdrawal reflex
What are the four types of white/grey matter in the spinal cord?
- Lateral white matter
- descending projections from brain, voluntary motor control - Dorsal white matter
- projections to the brain, sensory awareness - Dorsal grey matter
- sensory processing - Ventral grey matter
- motor neuron somata
What is a reflex arc?
A reflex arc is a neural pathway that controls a reflex
In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord
This allows for faster reflex actions to occur by activating spinal motor neurons without the delay of routing signals through the brain
Trace the pathway of a reflex arc
- Sensory neuron - afferent neuron (stimulus/receptor)
- Spinal reflex arc (rapid, involuntary)
- Motor neuron - efferent neuron (effector/response)
What element of the spinal reflex arc/circuit might be damaged if:
The patient reports feeling the pin/hammer (and
flinches) but is unable to voluntarily move their hand.
Sensory neurons ✅
Reflex arc processing (reflex) ✅
Motor neurons ❌
It suggests a problem with the voluntary motor control component of the reflex arc.
The sensory neurons appear to be functioning because the patient perceives the stimulus, and the reflex arc is intact since the patient exhibits a reflexive response.
However, there may be an issue with the motor neurons or the muscles responsible for voluntary motor control.
What element of the spinal reflex arc/circuit might be damaged if:
The patient reports feeling the pin/hammer, but
doesn’t flinch, and is unable to voluntarily move
their hand.
Sensory neurons ✅
Reflex arc processing (reflex) ❌
Motor neurons ❌
The sensory neurons appear to be functioning because the patient perceives the stimulus, but there may be an issue with the transmission of sensory information to motor neurons or with the motor neurons and muscles responsible for the motor response
The lack of a flinch/reflex indicates that there could be an issue in the spinal cord
It suggests a problem with the motor component of the reflex arc which is causing the inability to move their hand
What element of the spinal reflex arc/circuit might be damaged if:
The patient doesn’t report feeling the
pin/hammer but can move the hand on command.
Sensory neurons ❌
Reflex arc processing (reflex) ❌
Motor neurons ✅
It suggests a problem with the sensory pathway, particularly the sensory neurons responsible for transmitting sensory information to the brain.
The lack of a reflex/flinch indicates that the spinal cord processing may be affected.
The ability to move the hand on command indicates that the motor component of the reflex arc, including motor neurons and muscles, is intact and functioning properly
What element of the spinal reflex arc/circuit might be damaged if:
The patient’s hand still flinches at the pin/hammer but the patient does not report feeling it.
Sensory neurons ❌
Reflex arc processing (reflex) ✅
Motor neurons ✅ (unaffected)
It suggests that there may be an issue with the sensory pathway, such as damage to the sensory neurons or interneurons responsible for transmitting sensory information to the brain for conscious perception
The patient flinches so the spinal cord processing is unaffected–And there is no mention of their ability to move their hand upon command (so it is assumed to be unaffected)
What is the function of the nervous system?
Coordinate the rest of the body - rapid and specific integration and transfer of information between different body systems and different regions using electrical and chemical signals
What are the two classes of cells in nervous tissue?
Neurons
Neuroglia
Both of these classes are highly diverse and can be divided into many subtypes with different structures and functions
What are the two divisions of the nervous system?
Nervous system can be divided into CENTRAL and PERIPHERAL divisions
Capacity for repair is mostly restricted to which division of the nervous system?
Repair is mostly restricted to the PERIPHERAL NERVOUS SYSTEM
Difference between sensory and motor and voluntary and involuntary/unconscious deficits
