Nervous System Flashcards by Marie Claire Pasil

Functions of the Nervous System

SIM

Sensory input
Integration
Motor output

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The function of NS is gathering information

This monitor changes happening inside and outside the body

Sensory input

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The function of NS processes and interprets sensory input and decides whether action is needed

Integration

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The function of NS is a response, or effect, activates muscles or glands

Motor output

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Nervous system classifications are based on:

Structures (structural classification)

* Activities (functional classification)

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2 Levels of organization

Central nervous systems

Peripheral nervous systems

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The organs of CNS are:

B & S

Brain

* Spinal cord

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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)

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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)

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The 2 nerves of PNS are:

S& C

Spinal & Cranial nerves

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nerves that carry impulses to and from the spinal cord

Spinal nerves

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carry impulses to and from the brain

Cranial nerves

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2 division of nerve fibers of PNS:

S&M

Sensory division & Motor division

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Nerve fibers that carry information to the central nervous system
(afferent)

Sensory division

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2 sensory division (S&V)

Somatic & Visceral

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sensory fibers carry information from the skin, skeletal muscles, and joints

Somatic

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sensory fibers carry information from visceral organs

Visceral

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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

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2 motor subdivisions (S&A)

Somatic nervous system

Autonomic nervous system

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voluntary

Consciously controls skeletal muscles

That rules your skeletal muscle movement

Somatic nervous system

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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

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Support cells in the CNS are grouped together as neuroglia

Nervous Tissue

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The type of cells ____ respond to stimuli and transmit signals

neurons, or nerve cells

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Nervous Tissue Functions (SIP)

Support
Insulate
Protect neurons

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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

1. 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

2. 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)

3. 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

4. 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

5. 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

6. 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:

1. Heart rate 2. Blood pressure 3. Breathing 4. Swallowing 5. 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 1. 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 2. CSF flows through the subarachnoid space 3. CSF is absorbed into the dural venous sinuses via the arachnoid villi 4. 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)

1. Optic 2. Olfactory 3. 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

1. Receptor senses stimulus 2. Sensory neuron transmits signal to PNS & CNS 3. Integration center decodes signal 4. Motor neuron sends directions back to the site of the stimulus 5. 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

Nervous System Flashcards

(372 cards)