Nervous System Flashcards
Functions of the Nervous System
SIM
Sensory input
Integration
Motor output
The function of NS is gathering information
This monitor changes happening inside and outside the body
Sensory input
The function of NS processes and interprets sensory input and decides whether action is needed
Integration
The function of NS is a response, or effect, activates muscles or glands
Motor output
Nervous system classifications are based on:
- Structures (structural classification)
* Activities (functional classification)
2 Levels of organization
Central nervous systems
Peripheral nervous systems
The organs of CNS are:
B & S
- Brain
* Spinal cord
One of the NS that function as integration; command center
One of the NS that interprets incoming s ensory information
One of the NS that issues outgoing instructions
The main control center
The one that decide and give order
Central nervous system (CNS)
Nervous system that is extending from the brain and spinal cord
Allow your central nervous system to communicate with the rest of your body
One of the NS that serve as communication lines among sensory organs, the brain and spinal cord, and glands or muscles
Peripheral nervous system (PNS)
The 2 nerves of PNS are:
S& C
Spinal & Cranial nerves
nerves that carry impulses to and from the spinal cord
Spinal nerves
carry impulses to and from the brain
Cranial nerves
2 division of nerve fibers of PNS:
S&M
Sensory division & Motor division
Nerve fibers that carry information to the central nervous system
(afferent)
Sensory division
2 sensory division (S&V)
Somatic & Visceral
sensory fibers carry information from the skin, skeletal muscles, and joints
Somatic
sensory fibers carry information from visceral organs
Visceral
Nerve fibers that carry impulses away from the central nervous system organs to effector organs (muscles and glands)
Sends directions from your brain to the muscles and glands
(efferent)
Motor division
2 motor subdivisions (S&A)
Somatic nervous system
Autonomic nervous system
voluntary
Consciously controls skeletal muscles
That rules your skeletal muscle movement
Somatic nervous system
involuntary
Automatically controls smooth and cardiac muscles and glands
Further divided into the sympathetic and parasympathetic nervous systems
That keeps your heart beating, and your lungs breathing, and your stomach churning
Autonomic nervous system
Support cells in the CNS are grouped together as neuroglia
Nervous Tissue
The type of cells ____ respond to stimuli and transmit signals
neurons, or nerve cells
Nervous Tissue Functions (SIP)
Support
Insulate
Protect neurons
2 principal cell types
Supporting cells
Neurons
Cells that also called neuroglia, or glial cells, or glia
Provide support, nutrition, insulation, and help with signal transmission in the nervous system
Resemble neurons
Unable to conduct nerve impulses
Never lose the ability to divide
Glue that held neurons together
Supporting cells
4 CNS glial cells:
A, M, EC, O
astrocytes
microglia
ependymal cells
oligodendrocytes
- Most Abundant glia cells
- star-shaped cells
- Brace and anchor neurons to blood capillaries
- Protect neurons from harmful substances in blood
- Control the chemical environment of the brain
- Support, regulate ions
- Exchange of materials between neurons and capillaries
astrocytes
- Spiderlike phagocytes
- Monitor health of nearby neurons
- Dispose of debris
- Defend
- Act as the main source of immune defense against invading microorganisms in the brain and spinal cord
microglia
- Line cavities of the brain and spinal cord
* Create, secrete, & circulate cerebrospinal fluid that fills those cavities and cushions those organs
ependymal cells
- produce myelin sheaths around axons of the CNS
- Lack a neurilemma
- Wrap and insulate around neurons
- Producing an insulating barrier (myelin sheath)
oligodendrocytes
2 PNS glial cells (S&S)
Schwann cells
Satellite cells
- Form myelin sheath around nerve fibers in the PNS
- Do mainly in the peripheral system what astrocyte cells do in the central system
- They surround and support neuron cell bodies
Schwann cells
- Protect and cushion neuron cell bodies
- Insulate, help form myelin sheath
- Similar to your oligodendrocytes
- Wrap around axons and make that insulating myelin sheath
Satellite cells
nerve cells
Cells specialized to transmit messages (nerve impulses)
Neurons
3 things in common in Neurons
Neurons are some of the longest-lived cells in your body.
Neurons are irreplaceable
Neurons have huge appetites
2 Major regions of all neurons
C&P
Cell body
Processes
nucleus and metabolic center of the cell
the metabolic center of the neuron
Cell body
Fibers that extend from the cell body
A projecting part of an organic structure
Processes
The cell body Rough endoplasmic reticulum
Nissl bodies
The cell body Intermediate filaments that maintain cell shape
Neurofibrils
(cell body)
Neuron’s life support
Soma
2 Specialized project of neurons:
D&A
Dendrites
Axons
Conduct impulses toward the cell body
The listeners
They pick up messages, news, gossip from other cells and convey that information to the cell body
Dendrites
Conduct impulses away from the cell body
The talker
Can be super short or run a full meter from your spine down to your ankle
Axons
Neurons have hundreds of ___ and have only one ____ arising from the cell body
Dendrites - axon
- End of an axon, which contain vesicles with neurotransmitters
- Axon terminals are separated from the next neuron by a gap
Axon terminals
gap between axon terminals and the next neuron
Synaptic cleft
functional junction between nerves where a nerve impulse is transmitted
Synapse
- White, fatty material covering axons
- Protects and insulates fibers
- Speeds nerve impulse transmission
Myelin
sleeves of fatty tissue that protect your nerve cells
carries messages back and forth between your brain and the rest of your body
Myelin sheaths
part of the Schwann cell external to the myelin sheath
Neurilemma
gaps in myelin sheath along the axon
Nodes of Ranvier
• clusters of cell bodies in the CNS
Nuclei
• collections of cell bodies outside the CNS in the PNS
Ganglia
• bundles of nerve fibers in the CNS (T)
Tracts
• bundles of nerve fibers in the PNS (N)
Nerves
• matter of collections of myelinated fibers (tracts)
White matter
• matter that is mostly unmyelinated fibers and cell bodies
Gray matter
- association neurons
- Cell bodies located in the CNS
- Connect sensory and motor neurons
- Transmit impulses between those sensory and motor neurons
- Most abundant of your body’s neurons
- Mostly multipolar
Interneurons
5 Sensory (afferent) neurons (FMLGM)
A. Free nerve endings B. Meissner’s corpuscle C. Lamellar corpuscle D. Golgi tendon organ E. Muscle spindle
Pain and temperature receptors
Free nerve endings
Touch receptor
Meissner’s corpuscle
Deep pressure receptor
Lamellar corpuscle
Proprioceptor
Golgi tendon organ & Muscle spindle
- one axon and a bunch of dendrites
- Most common structural type
- Many extensions from the cell body
- Where 99 percent of all your neurons found
Multipolar neurons
- one axon and one dendrite
- Located in special sense organs, such as nose and eye
- Rare in adults (found only in a special-sensory places)
Bipolar neurons
- Have a short single process leaving the cell body
- Sensory neurons found in PNS ganglia
- Conduct impulses both toward and away from the cell body
Unipolar neurons
2 Functional properties of neurons
Irritability and Conductivity
• Ability to respond to a stimulus and convert it to a nerve impulse
Irritability
• Ability to transmit the impulse to other neurons, muscles, or glands
Conductivity
1st Step that the plasma membrane at rest is inactive
In neuron’s plasma, there are fewer positive ions inside than outside
- Resting membrane is polarized
In Resting membrane is polarized, K+ is the major positive ion ___ the cell
inside
In Resting membrane is polarized, Na+ is the major positive ion ___ the cell
outside
As long as the inside of the membrane is more negative (fewer positive ions) than the outside, the cell remains ___
inactive
- 2nd step that stimulus changes the permeability of the neuron’s membrane to sodium ions
- Sodium channels now open
- Sodium diffuses into the neuron
- Changes the polarity of the membrane at that site
- Stimulus initiates local depolarization
- 3rd steps that graded potential exists (inside more positive – outside more negative/less positive)
- If the stimulus is strong enough and sodium influx great enough, local depolarization activates the neuron to conduct an action potential (nerve impulse)
- Depolarization and generation of an action potential
4th step that the depolarization of the 1st membrane patch causes permeability changes in adjacent membrane and events in step 2 are repeated
• If enough sodium enters the cell, the action potential (nerve impulse) starts and is propagated over the entire axon
• All-or-none response means the nerve impulse either is propagated or is not
• Fibers with myelin sheaths conduct nerve impulses more quickly
- Propagation of the action potential
- 5th step that the membrane permeability changes again becoming impermeable to sodium ions and permeable to potassium ions
- Potassium ions rapidly diffuse out of the neuron, repolarizing the membrane
- Involves restoring the inside of the membrane to a negative charge and the outer surface to a positive charge
- Occurs in the same direction as depolarization
- Repolarization
- 6th step that are restored using the sodium-potassium pump
- This pump, using ATP, restores the original configuration
- 3 sodium ions are ejected from the cell, 2 potassium ions are returned to the cell
- Until repolarization is complete, a neuron cannot conduct another nerve impulse
- Initial Ionic conditions restored
Are rapid, predictable, and involuntary responses to stimuli
Reflexes
neural pathways in reflexes
Reflex arcs
2 types of reflexes
S&A
Somatic reflexes
Autonomic reflexes
Type of reflexes that stimulate the skeletal muscles
Involuntary
Example: pulling your hand away from a hot object
Somatic reflexes
Regulate the activity of smooth muscles, the heart, and glands
Example: regulation of smooth muscles, heart and blood pressure, glands, digestive system
Autonomic reflexes
Five elements of a reflex arc
Sr, Sn, Ic, Mn, Eo
Sensory receptor Sensory neuron Integration center Motor neuron Effector organ
reacts to a stimulus
Sensory receptor
carries message to the integration center
Sensory neuron
processes information and directs motor output
Integration center (CNS)
carries message to an effector
Motor neuron
is the muscle or gland to be stimulated
Effector organ
- Simplest type
* Example: patellar (knee-jerk) reflex
Two-neuron reflex arcs
- Consists of 5 elements: receptor, sensory neuron, interneuron, motor neuron, and effector
- Example: flexor (withdrawal) reflex
Three-neuron reflex arcs
5 elements
R,I,M,E,S
Receptor Interneuron Motor neuron Effector Sensory neuron
• Functional anatomy of the brain
Central Nervous System (CNS)
4 Brain regions (C,C,B,D)
Cerebral hemispheres
Cerebellum
Brain stem
Diencephalon
- Are paired (sagittal) superior parts of the brain
- Include more than half of the brain mass
- The surface is made of ridges and grooves
Cerebral hemispheres
are named for the cranial bones that lie over them
Lobes
Other term of ridges
gyri
Other term of grooves
sulci
Deeper grooves
Fissures
3 main regions of cerebral hemisphere
CIB
Cerebral cortex (gray matter)
Internal white matter
Basal nuclei
are deep pockets of gray matter
Basal nuclei
Functions of Major Brain Region (CCDB)
Cerebellum
Cerebral hemispheres
Diencephalon
Brain stem
- Located in parietal lobe posterior to central sulcus
- Receives impulses from the body’s sensory receptors
- Pain, temperature, light touch (except for special senses)
- Sensory homunculus is a spatial map
Primary somatic sensory area
Cerebral areas involved in special senses
OVA
Visual area, Auditory area, and Olfactory area
The lobe called in Visual area
occipital lobe
The lobe called in Auditory area & Olfactory area
temporal lobe
- Located anterior to the central sulcus in the frontal lobe
- Allows us to consciously move skeletal muscles
- Motor neurons form pyramidal (corticospinal) tract, which descends to spinal cord
- Motor homunculus is a spatial map
Primary motor area
(motor speech area)
Broca’s area
- Composed of fiber tracts deep to the gray matter
- Association fiber tracts connect areas within a hemisphere
- Projection fiber tracts connect the cerebrum with lower CNS centers
Cerebral white matter
Tracts are known as
commissures
Localizes and interprets sensory inputs
Controls voluntary and skilled muscle activity
Acts in intellectual and emotional processing
Cortex: Gray Matter
“Islands” of gray matter buried deep within the white matter of the cerebrum
Subcortical motor centers help control skeletal muscle movements
Basal nuclei
Sits on top of the brain stem
Enclosed by the cerebral hemispheres
Regulate things like homeostasis, alertness, and reproductive activity
Diencephalon
3 structures of Diencephalon (THE)
Thalamus, Epithalamus, and Hypothalamus
- Encloses the 3rd ventricle
- Relay station for sensory impulses passing upward to the cerebral cortex
- Transfers impulses to the correct part of the cortex for localization and interpretation
- Relays sensory impulses to cerebral cortex
- Relays impulses between cerebral motor cortex and lower motor centers
- Involved in memory
Thalamus
- Chief integration center of autonomic (involuntary) nervous system
- Regulates body temperature, food intake, water balance, and thirst
- Regulates hormonal output of anterior pituitary gland and acts as an endocrine organ (producing ADH and oxytocin)
- Makes up the floor of the diencephalon
- Important autonomic nervous system center
- Houses the limbic center for emotions
- Houses mammillary bodies for olfaction (smell)
Hypothalamus
- Forms the roof of the third ventricle
- Houses the pineal body (an endocrine gland)
- Includes the choroid plexus that forms cerebrospinal fluid
Epithalamus
• Attaches to the spinal cord
Brain stem
3 Parts of the brain stem (MMP)
Midbrain, Pons, and Medulla oblongata
- Extends from the mammillary bodies to the pons inferiorly
- Cerebral aqueduct (tiny canal) connects the third and fourth ventricles
- Two bulging fiber tracts, cerebral peduncles, convey ascending and descending impulses
- Contains visual and auditory reflex centers
- Contains subcortical motor centers
Midbrain
- Relays information front the cerebrum to the cerebellum
- Cooperates with the medullary centers to control respiratory rate and depth
- Contains nuclei of cranial nerves V-VII; contains projection fibers
- Mostly composed of fiber tracts
- Includes nuclei involved in the control of breathing
Pons
- Relays ascending sensory pathway impulses from • skin and proprioceptors
- Contains nuclei controlling heart rate, blood vessel diameter, respiratory rate, vomiting, etc.
- Contains nuclei of cranial nerves VIII-XII; contains projection fibers
- The most inferior part of the brain stem that merges into the spinal cord
- Includes important fiber tracts
Medulla oblongata
Medulla oblongata contains 5 important centers that control:
- Heart rate
- Blood pressure
- Breathing
- Swallowing
- Vomiting
4th ventricle lies posterior to: (P&M)
pons and medulla
Diffuse mass of gray matter along the brain stem
Involved in motor control of visceral organs
Reticular formation
Plays a role in awake/sleep cycles and consciousness
• Filter for incoming sensory information
Reticular activating system (RAS)
- Two hemispheres with convoluted surfaces
- Outer cortex of gray matter and inner region of white matter
- Controls balance
- Provides “instructions” to cerebral motor cortex and subcortical motor centers resulting in smooth, coordinated skeletal muscle movements
- Responsible for proper balance and posture
Cerebrum
3 Protection of the Central Nervous System (M, TC, CSF)
Meninges, Tentorium cerebelli, & Cerebrospinal fluid
Outermost leathery layer
Double-layered external covering
Folds inward in several areas
Dura mater
Cerebral falx also known as
Falx cerebri
attached to inner surface of the skull
Periosteum
outer covering of the brain
Meningeal layer
- Middle layer
- Weblike extensions span the subarachnoid space to attach it to the pia mater
- Subarachnoid space is filled with cerebrospinal fluid
- Arachnoid granulations protrude through the dura mater and absorb cerebrospinal fluid into venous blood
Arachnoid layer
Internal layer
Clings to the surface of the brain and spinal cord
Pia mater
- Similar to blood plasma in composition
- Formed continually by the choroid plexuses
- Forms a watery cushion to protect the brain and spinal cord
- Circulated in the arachnoid space, ventricles, and central canal of the spinal cord
Cerebrospinal fluid (CSF)
capillaries in the ventricles of the brain
Choroid plexuses
CSF Circulation
- CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord
- CSF flows through the subarachnoid space
- CSF is absorbed into the dural venous sinuses via the arachnoid villi
- CSF is produced by the choroid plexus of each ventricle
4, 1, 3, 2
- Includes the least permeable capillaries of the body
- Allows water, glucose, and amino acids to pass through the capillary walls
- Excludes many potentially harmful substances from entering the brain, such as wastes
- Useless as a barrier against some substances
Blood-brain barrier
• Traumatic brain injuries
Brain Dysfunctions
- Slight brain injury
* Little permanent brain damage occurs
Concussion
- Marked nervous tissue destruction occurs
* Coma may occur
Contusion
Death may occur after head blows due to:
Intracranial hemorrhage
Cerebral edema
- Also called stroke
- Results when blood circulation to a brain area is blocked and brain tissue dies
- Loss of some functions or death may result
Cerebrovascular accident (CVA)
one-sided paralysis
Hemiplegia
damage to speech center in left hemisphere
Aphasia
- Temporary brain ischemia
* Numbness, temporary paralysis, impaired speech
Transient ischemic attack (TIA)
restriction of blood flow
Ischemia
- Extends from the foramen magnum of the skull to the first or second lumbar vertebra
- Cauda equina is a collection of spinal nerves at the inferior end
- Provides a two-way conduction pathway to and from the brain
- 31 pairs of spinal nerves arise from the spinal cord
Spinal Cord
Internal gray matter is mostly cell bodies
Surrounds the cent
Gray matter
- house interneurons
- Receive information from sensory neurons in the dorsal root
- Cell bodies housed in dorsal root ganglion
Dorsal horns
- House motor neurons of the somatic nervous system
* Send information out ventral root
Anterior horns
Composed of myelinated fiber tracts
White matter
3 regions of white matter:
dorsal, lateral, ventral columns
conduct impulses toward brain
Sensory (afferent) tracts
carry impulses from brain to skeletal muscles
Motor (efferent) tracts
Consists of nerves and ganglia outside the CNS
Peripheral Nervous System (PNS)
are bundles of neurons found outside the CNS
Nerves
is a connective tissue sheath that surrounds each fiber
Endoneurium
wraps groups of fibers bound into a fascicle
Perineurium
binds groups of fascicles
Epineurium
• Contain both sensory and motor fibers
Mixed nerves
• Carry impulses toward the CNS
Sensory (afferent) nerves
• Carry impulses away from the CNS
Motor (efferent) nerves
- 12 pairs of nerves serve mostly the head and neck
* Only the pair of vagus nerves extends to thoracic and abdominal cavities
Cranial Nerves
Most are mixed nerves, but three are sensory only (O,O,V)
- Optic
- Olfactory
- Vestibulocochlear
- 31 pairs of nerves
- Formed by the combination of the ventral and dorsal roots of the spinal cord
- Named for the region of the spinal cord from which they arise
Spinal Nerves
Spinal nerves divide soon after leaving the spinal cord into a dorsal ___ and a ventral ___
Ramus
- branch of a spinal nerve
* contains both motor and sensory fibers
Ramus
• serve the skin and muscles of the posterior trunk
Dorsal rami
Ventral rami
• form the intercostal nerves that supply muscles and skin of the ribs and trunk
(T1–T12)
Ventral rami
• form a complex of networks (plexus) for the anterior
(except T1–T12)
- networks of nerves serving motor and sensory needs of the limbs
- Form from ventral rami of spinal nerves in the cervical, lumbar, and sacral regions
Plexus
Four plexuses (BLCS)
Brachial
Lumbar
Cervical
Sacral
- Motor subdivision of the PNS
- Consists only of motor nerves
- Controls the body automatically
- Known as the involuntary nervous system
- Regulates cardiac and smooth muscles and glands
Autonomic Nervous System
- Motor neuron cell bodies originate inside the CNS
* Axons extends to skeletal muscles that are served
Somatic nervous system
Chain of 2 motor neurons
Preganglionic & Postganglionic
neuron is in the brain or spinal cord
Preganglionic
neuron extends to the organ
Postganglionic
Has two arms
Sympathetic division
Parasympathetic division
division is also known as the craniosacral division
Parasympathetic division
Preganglionic neurons originate in:
- Cranial nerves III, VII, IX, and X
* S2 through S4 regions of the spinal cord
Preganglionic neurons synapse with____ ; from there, ____ axons extend to organs that are served
terminal ganglia – postganglionic
Division also known as the thoracolumbar division
Sympathetic division
Body organs served by the autonomic nervous system receive fibers from both divisions
Autonomic Functioning
Exceptions in autonomic functioning: blood vessels, structures of the skin, some glands, and the adrenal medulla
These exceptions receive only ____
sympathetic fibers
When body divisions serve the same organ, they cause antagonistic effects due to different
neurotransmitters
(cholinergic)
release acetylcholine
Parasympathetic fibers
(adrenergic)
release norepinephrine
Sympathetic postganglionic fibers
axons of both divisions (sym and para) release acetycholine
Preganglionic
• “fight or flight” division
• Response to unusual stimulus when emotionally or physically stressed or threatened
• Takes over to increase activities
• mobilizes the body into action and gets it all fired up
Remember as the “E” division
Sympathetic
4 “E” division of Sympathetic
Exercise
Excitement
Emergency
Embarrassment
• “housekeeping” activites • “Rest-and-digest” system • Conserves energy • Maintains daily necessary body functions relaxes the body and talks it down • Remember as the “D” division
Parasympathetic
3 “D” division Parasympathetic
Digestion
Defecation
Diuresis
Nervous system is formed during:
1st month of embryonic development
Any maternal infection can have ___ harmful effects
extremely
Oxygen deprivation destroys
brain cells
one of the last areas of the brain to develop
Hypothalamus
Premature babies have trouble regulating body temperature. Why?
the hypothalamus is one of the last brain areas to mature before birth
Development of motor control indicates the progressive (m&m) _______ of a child’s nervous system
myelination and maturation
Brain growth ends in
young adulthood
low blood pressure due to changes in body position
Orthostatic hypotension
is the major cause of declining mental function with age
Disease (cardiovascular disease)
is decreased elasticity of blood vessels
Arteriosclerosis
(a) Spatial summation
(b) Temporal summation
(c) Combined summation with both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs)
3 SUMMATION
- Action potentials 1 and 2 cause the production of graded potentials at two different dendrites.
- These graded potentials summate at the trigger zone to produce a graded potential that exceeds threshold, resulting in an action potential.
(a) Spatial summation
- Two action potentials arrive in close succession at the postsynaptic cell from the presynaptic terminal.
- The first action potential causes the production of a graded potential in the postsynaptic cell that does not reach threshold at the trigger zone.
- The second action potential results in the production of a second graded potential that summates with the first to reach threshold, resulting in the production of an action potential.
(b) Temporal summation.
• An action potential is produced at the trigger zone when the graded potentials produced as a result of the EPSPs and IPSPs summate to reach threshold.
(c) Combined summation with both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs).
Nerve impulse
Action Potential
Body as a whole is electrically neutral (with equal amounts of positive and negative charges floating around)
Electricity
The measure of potential energy generated by separated charges
millivolts
Voltage
In a cell, we refer to this difference in charge as the
membrane potential
The bigger the difference between the positive and negative areas,
the higher the voltage, and the larger the potential
The flow of electricity from one point to another
The amount of charge in a current is related both to its voltage and its resistance
Current
Whatever’s getting in the way of the current
Resistance
high resistance (plastic)
Insulator
low resistance (metal)
Conductor
A resting neuron is like a battery just sitting in that sack that is you
When it’s just sitting there, it’s more negative on the inside of the cell, relative to the extracellular space around it
This difference is known as the ____
neuron’s resting membrane potential
Charges come from
outside and inside
there’s a bunch of positive sodium ions floating around, just lingering outside the membrane
Outside
the neuron: holds potassium ions that are positive as well, but they’re mingled with bigger, negatively-charged proteins
Inside
Since there are more sodium ions outside than there are potassium ions inside, the cell’s interior has an overall ____
negative charge
When a neuron has a negative membrane potential
Polarized
- Arranged by one of the most important bits of machinery in nervous system
- This little protein straddles the membrane of the neuron and there are tons of them all along the axon
Sodium-potassium pump
For every 2 potassium ions it pumps into the cell, it pumps out
3 sodium ions
- Creates a difference in the concentration of sodium and potassium
- A difference in charges, making it more positive outside the neuron
Electrochemical gradient
Nature hates ____
• It wants to even out all of those inequalities, in concentration and in charge, to restore balance
• But the only way to even out that gradient, is for the ions to pass across the membrane
gradients
Open at certain membrane potentials, and close at others
Open and close in response to changes in membrane potential
Voltage-gated channels
Only open up when a specific neurotransmitter (like serotonin, or a hormone) latches on to it
Ligand-gated channels
open in response to physically stretching the membrane
Mechanically-gated channels
If only a few channels open, and only a bit of sodium enters the cell, that causes just a little change in the membrane potential in a localized part of the cell.
Graded potential
- Its ion channels are open, it can’t respond to any other stimulus, no matter how strong
- Help prevent signals from traveling in both directions down the axon at once
Refractory period
- The first phase of this period, from depolarization to repolarization
- It makes sure that each action potential is its own unique, all or nothing event
Absolute refractory period
The one that spans from repolarization through hyperpolarization and back to resting potential
Relative refractory period
The strength of that action potential is
always the same
A weak stimulus tends to trigger
less frequent action potentials
Action potentials also vary by speed or
conduction velocity
- Little gaps
- Kind of propagation is known as saltatory conduction
- From the Latin word for “leaping.”
Nodes of Ranvier
- The meeting point between two neurons
- The tiny communication links between neurons
- Comes from the Greek for “to clasp or join.”
- A junction or a crossroads
- Are what allow you to learn and remember
- The root of many psychiatric disorders
Synapse
Nerve cells have 2 main settings for communicating depending on
how fast the news needs to travel
Immediate group text
Electrical
Take more time to be received and read, but they’re used more often and are much easier to control, sending signals to only certain recipients.
Chemical
Why aren’t all of our synapses electrical?
A matter of control
the strengthening of a synapse through classic conditioning
Potential
when a synapse decreases its response to a common stimulus
Habituation
when a reaction to one stimulus causes other synapses to be more sensitive to reactions
Sensitization
The cell that’s sending the signal and it transmits through presynaptic terminal
Presynaptic neuron
A knoblike structure
The axon terminal
Presynaptic terminal
Mainly inhibitory and plays an important role in regulating mood, appetite, circadian rhythm, and sleep
Some antidepressants can help stabilize moods by stabilizing serotonin levels
Serotonin
Releases when you engage in pleasurable activities – like hugging a loved one, or having sex, or eating a really, really great donut – your brain, which influences emotion and attention, but mostly just makes you feel awesome
Dopamine
Amps you up by triggering your fight or flight response, increasing your heart rate, and priming muscles to engage, while an undersupply of the chemical can depress a mood
Norepinephrine
responsible for the ability to produce and process language
Broca’s area
leaves its sufferers with some ability to understand speech, but an inability to produce intelligible words
Broca’s aphasia
Our nervous system is divided into two main networks that work in harmony:
CNS and PNS
system consisting of brain and spinal cord
The central nervous system
system that is made up of the nerves coming out of that central nervous system
The peripheral nervous system
The central nervous system’s main game is
integrating the sensory information
The peripheral system collects information from all over the body, and responding to it by coordinating both
conscious and unconscious activity
Sorts out all that sensory information and gives orders
It also carries out your most complex functions, like thinking, and feeling, and remembering
Brain
Conducts two-way signals between your brain and the rest of your body
Governing basic muscle reflexes and patterns that don’t need your brain’s blessing to work
Spinal cord
Inside a developing embryo, the central nervous system starts off as a humble little
neural tube
Then the lower end of the tube stretches out, forming the
spinal cord
While the cranial end begins to ____ (ede) into 3 primary brain vesicles
expand, divide, and enlarge
3 brain chambers
Prosencephalon
Mesencephalon
Rhombencephalon
5 Secondary Vesicles
Telencephalon Diencephalon Metencephalon Myelencephalon Mesencephalon
Forebrain
Prosencephalon
Midbrain
Mesencephalon
Hindbrain
Rhombencephalon
Endbrain
Telencephalon
Interbrain
Diencephalon
Afterbrain
Metencephalon
Spinal brain
Myelencephalon
Midbrain
Mesencephalon
By an embryo’s fifth week of development, the main 3 chambers start morphing into ____ that essentially form the roots
5 secondary vesicles
Prosencephalon divides into two sections
telencephalon & diencephalon
In between telencephalon & diencephalon is the
mesencephalon
Rhombencephalon divides into two sections
Metencephalon & myelencephalon
The real action starts as the 5 secondary vesicles start developing into the
major adult brain regions
Major adult brain regions are: (BCC D/I)
Brainstem
Cerebellum
Diencephalon (known as interbrain)
Cerebral hemispheres
In order to go from a simple tube into brain, each of these five vesicles grows in
different ways
The least dramatic changes occur in the 3 most caudal sections which are: (3Ms)
mesencephalon
metencephalon
myelencephalon
The 3Ms form:
cerebellum and brainstem
helps coordinate muscular activity
Cerebellum
relaying information between the body and the higher regions of the brain
Brainstem
3 main components of brainstem: (MMP)
Midbrain
Pons
Medulla oblongata
Together ______ regulate keeping your heart on pace, lungs working, and controlling things
3 main components of brain
On the 3 brainstem parts, it’s your ____ that carries out the higher-level functions
midbrain
group of neurons in the brain that receive and process signals from sensory organs
Sensory center
receives and processes that sensory information and sends out the reflexive motor signals, so you react without thinking
Midbrain
the center for strong emotions, like fear.
also called the “reptilian brain”
Limbic system
During your brain’s growth, the ___ undergoes the biggest changes of all
telencephalon
It develops into the most part of your brain which is the
cerebrum
- cover the rest of your brain
- the largest region of the brain
- performs the highest functions
- rules our voluntary movements
Cerebrum
made up of the wrinkled, outer layer of “gray matter” called the _____ and the inner squishy layer of “white matter” beneath it
cerebral cortex
Higher processing requires lots of____, which require lots of nervous tissue
synapses
So as the cerebrum grew through time, it got more massive but our skull didn’t exactly keep up.
In order to squeeze all material into your skull, the brain forms
gyri and sulci
little creases
Gyri
larger grooves
Sulci
Two hemispheres communicate, through a series of myelinated axon fibers called the
corpus callosum
Each hemisphere has other, smaller fissures that divide it into
lobes
- Governs muscle control and cognitive functions like concentration
- Since Broca’s area lives in this lobe in the left hemisphere, it also is important in language comprehension and speech
Frontal lobe
- Processing bright visual cues
* If you’re enjoying a beautiful sunset
Occipital lobe
- Processes the sensations of touch, pain, and pressure
* The next time you step on a lego, you can curse it
Parietal lobe
- Helps sort out auditory information, including language
* It contains Wernicke’s area
Temporal lobe
• Another important region of the brain associated with the production of written and spoken language
Wernicke’s area
This part of the limbic system includes:
Hippocampus & Amygdala
short-term memory keeper
Hippocampus
controls sexual and social behavior
Amygdala
Spy on the world for the central nervous system
Sensory nerve receptors
Each sensory nerve type responds to different kinds of stimuli: (MCPT)
Mechanoreceptors, Chemoreceptors, Photoreceptors, Thermoreceptors
Respond to changes in temperature
Thermoreceptors
React to light
Photoreceptors
Pay attention to chemicals
Chemoreceptors
Respond to pressure, touch, and vibration
Mechanoreceptors
Specialized nerve receptors
Fire only to indicate pain
Nociceptors
- Receptor senses stimulus
- Sensory neuron transmits signal to PNS & CNS
- Integration center decodes signal
- Motor neuron sends directions back to the site of the stimulus
- Effector cells responds by contracting
5 steps of reflex arc
2 divisions of autonomic system
Sympathetic Nervous System
Parasympathetic Nervous System
Dedicated to amping you up and preparing you for activity
Sympathetic Nervous System
Talks you down and effectively undoes what its foil did
Parasympathetic Nervous System
The stress response includes two kinds of chemicals: (N & H)
Neurotransmitters
Hormones
- Are made and released from neurons themselves
* What neurons use to communicate with each other or their effector organs across a synapse
Neurotransmitters
- Are secreted by your glands
- Flow through bloodstream
- There are at least 50 different hormones at work in your body right now, and they do everything from regulating your sleep cycles to making your body retain water so you’re not dying of dehydration all over the place
Hormones
Hormones and neurotransmitters are 100% necessary for understanding how your
sympathetic division works
When the signals reach the synapses inside the ganglia, the nerve fibers then release a neurotransmitter – called
acetylcholine
When it comes to nervous communication, ACh is really the coin of the realm.
So, that acetylcholine crosses the synapse and, if there’s enough of it, it can stimulate action potentials in several neurons on the other end – in the
postganglionic fibers
And at the end of that second, postganglionic neuron, the fiber releases a different neurotransmitter called
norepinephrine
It is always ____ that’s released from postganglionic fibers in the sympathetic nervous system
norepinephrine
Preganglionic fiber releases
ACh
Postganglionic releases
norepinephrine
In addition to nerve fibers that lead to ganglia and then your effectors, there’s also a set leaving the spinal cord that goes directly to your
adrenal glands
Norepinephrine is both a ____, and which one it is depends on how it’s being use
neurotransmitter and hormone
If norepinephrine is being released from a neuron and travelling across a synapse, we refer to a messenger chemical as a
neurotransmitter
If norepinephrine is being secreted by a gland into the bloodstream for more widespread distribution, it’s a
hormone
How can the same chemical cause opposite responses?
Depends on the particular kind of ___ that an effector has for receiving that chemical
receptors
On the smooth muscle cells controlling some blood vessels, there are 2 receptors:
Alpha receptors & Beta receptors
When norepinephrine or epinephrine bind to those receptors, they make those smooth muscle cells contract, thereby restricting blood flow
Alpha receptors
For epinephrine and norepinephrine, and when they are activated, they make the muscles relax, letting more blood flow through
Beta receptors
Muscle cells contract
vasoconstriction
Muscles relax
vasodilation
The smooth muscle around your blood vessels, which feed skeletal muscles are covered in ____ because you want those blood vessels to relax, and provide plenty of oxygen to the muscles in your arms and legs
beta receptors
The blood vessels leading to your stomach and intestines have lots of ____, which reduce blood flow to those areas, because that burrito can wait until you’re out of the house
alpha receptors
Ganglia is located near the spinal cord
sympathetic ganglia
Ganglia is close to the effectors
parasympathetic side
In Parasympathetic Nervous System
Preganglionic Cell - Release ____
Postganglionic Cell - Release ____
Ach
In Sympathetic Nervous System
Preganglionic Cell - Release ____
Postganglionic Cell - Release ____
Ach
norepinephrine
They run right from the brain almost all the way to their effectors
They vary in terms of what kinds of neurons they contain
12 of these cranial nerves
Some of your cranial nerves also carry:
motor fibers
sensory fibers
that control voluntary functions
motor fibers
others carry only ___, which relay data to and from your sensory organs
sensory fibers
names and their functions. Know what each one is called, whether it’s a sensory nerve, a motor nerve, or both
Mnemonics
S-
M -
B -
sensory nerve
motor nerve
both
(S)
o Takes scent information gathered by the nose and sends it to the brain
Olfactory nerve
(S)
o Which does the same, but with visual data
Optic nerve
(M)
o Controls four of the six muscles that control the movements of your eyes.
Oculomotor
(M)
o Near the center of the brain’s ventral side
o Controls a single muscle in the eye
Trochlear nerve
(B)
o The largest of the cranial nerves
o Branches into 3 main strands and innervates the face and jaw muscles.
Trigeminal nerve
(M)
o Stimulates the muscles that let your eyes – from side to side
Abducens
(B)
o Operates the muscles that make most facial expressions possible.
Facial nerve
(S)
o Carries sensory information from the cochlea to the brain
Auditory nerve
(B)
o Leads to your tongue and your pharynx
Glossopharyngeal nerve
(B)
o Controls the heart and digestive tract among other functions
Vagus nerve
(M)
o Has to do with moving your head and shoulders
Spinal accessory nerve
(M)
o Allows you to swallow and talk
Hypoglossal
O-O-O T-T A-F-A G-V-S-H.
On Old Olympus’ Towering Top, A Fin And German Viewed Some Hops
Some Say Marry Money, But My Brother Says Big Brains Matter More.
Sequence of S’s, M’s and B’s to remember:
If you’re going to commit one cranial nerve type to memory, it should be 10th, the
vagus nerve
Come from latin for ‘wandering’ as in ‘vababond’
This long and extensive nerve stretches from near the brainstem down to most of your visceral organs, including your heart, lungs, and stomach
Vagus nerve
Vagus nerve work as a two-way street:
sensory information
transmitting motor instructions
from the peripheral system to the brain
sensory information
from the brain to the rest of the body
transmitting motor instructions
Looking at your body as a whole, you should picture them as two sides of a scale – sometimes
it’s balanced in the middle, and sometimes it leans to the left or right, depending on what’s happening
That balance is the essence of
homeostasis
