Nervous System Flashcards
Nervous Sys
Master controlling and communicating system of body
How does nervous sys communicate?
Cells communicate via electrical and chemical signals,
How are the those signals described?
Rapid and specific
Primary cell of the nervous system
is the neuron
Neurons are the key to what?
The key to neural transmission
Sensory input –
info gathered by sensory receptors about internal and external changes (cold or hot)
Integration-
processing and interpretation of sensory input and decides what actions are required
Motor output-
activation of effector organs (muscles and glands) yields a response
5 parts after stimulus but before response in simple reflect arc
- Receptor
- sensory neuron
- integration center
- motor neuron
- effector
Central nervous system (CNS) parts and location
Brain and spinal cord of dorsal body cavity
CNS job 3 parts
- Integration and control center
- Interprets sensory input and dictates motor output
- Motor output is based on reflexes, past experience, and/or current situation
Peripheral nervous system (PNS) Location
The portion of the nervous system outside CNS
PNS Consists mainly of
nerves that extend from brain and spinal cord
Two types of nerves in PNS
Spinal and Cranial Nerves
Spinal nerves
to and from spinal cord
Cranial nerves
to and from brain
PNS response simple term (common)
FIGHT OR FLIGHT
Histology of nervous tissue
Highly cellular; little extracellular space
Tightly packed
What are the 2 principal nervous cell types?
Neuroglia
Neurons (nerve cells )
Neurons (nerve cells )
excitable cells that transmit electrical signals
Neuroglia
small cells that surround and wrap delicate neurons: AKA glial cells, 6 types
6 types of neuroglia
Astrocytes (CNS) Microglial cells (CNS) Ependymal cells (CNS) Oligodendrocytes (CNS) Satellite cells (PNS) Schwann cells (PNS)
What neuroglia is most abundant?
Astrocytes (CNS)
Astrocytes (CNS)
Most abundant, versatile, and highly branched glial cells with radiating processes that
What do astrocytes cling to?
Cling to neurons, synaptic endings, and capillaries
Astrocyte function
Functions include
Support and brace neurons and anchor them to their nutrient supply
Play role in exchanges between capillaries and neurons
Guide migration of young neurons
Control chemical environment around neurons and calcium concentration
Respond to nerve impulses and recycle neurotransmitters
Influence neuronal functioning
Participate in information processing in brain
Describe Microglial cells (CNS)
Small, ovoid cells with thorny processes that touch and monitor neurons
Microglial cells (CNS) monitor
Monitor the health of neurons then migrate toward injured neurons
Microglial cells (CNS) transform
Can transform into a type of macrophage to phagocytize microorganisms and neuronal debris
Why are microglial cells vital?
Important because immune cells aren’t very permeable through the blood-brain barrier
Describe Ependymal Cells
Range in shape from squamous to columnar
Ependymal Cells may be
ciliated
Ependymal Cells line
Line the central cavities of the brain and spinal column
Ependymal Cells form
Form permeable barrier between cerebrospinal fluid (CSF) in cavities and tissue fluid bathing CNS cells
Oligodendrocytes are
branched cells
Oligodendrocytes processes
Processes wrap CNS nerve fibers, forming insulating myelin sheaths thicker nerve fibers
What gets damaged in MS?
Oligodendrocytes
Autoimmune disease is when
immune system attacks itself, they use chemo to stop immune response they don’t know why human body does this.
Different types of MS
Satellite cells Function
similar to astrocytes of CNS
Surround neuron cell bodies in PNS
Satellite cells
Surround all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers
Schwann cells (neurolemmocytes)
Schwann cells (neurolemmocytes) Function
Similar function as oligodendrocytes
Schwann Cells (neurolemmocytes) vital to what?
Vital to regeneration of damaged peripheral nerve fibers
Satellite cells anchor
neurons nerves need constant blood flow
Schwann cells have different
mylein sheath in some
Nerve cell are
amitotic, they don’t divide
Neurons
Structural units of nervous system
Neurons size and f(x)
Large, highly specialized cells that conduct impulses
How long do neurons last?
Extreme longevity ( 100 yrs or more if healthy)
Neurons are Amitotic but?
with few exceptions (hippocampus: involved with memory and recall)
Neuron high metabolic rate why?
High metabolic rate—requires continuous supply of oxygen and glucose
All neurons have this?
All have a cell body and one or more processes
Biosynthetic center of neuron does what?
Synthesizes proteins, membranes, and other chems
Biosynthetic center of neuron has what?
Rough ER (chromatophillic substance or nissel bodie) Most active and best developed in body
Neuron cell body has?
Biosynthetic center of neuron
Spherical nucleus with nucleolus
Some contain pigments
In most, plasma membrane part of receptive region
Most neuron cell bodies in CNS
Nuclei – clusters of neuron cell bodies in CNS
Ganglia – lie along nerves in PNS (ganglion)
Ganglia –
lie along nerves in PNS (ganglion
Nuclei –
clusters of neuron cell bodies in CNS
Nucleolus develops what?
ribosomes
Chromatophilc-
stains easily
Neuron Processes
Armlike processes extend from body
Neuron Processes in CNS
Both neuron cell bodies and their processes
Neuron Processes PNS
Chiefly neuron processes
Tracts
Bundles of neuron processes in CNS
Nerves
Bundles of neuron processes in PNS
Two types of neuron processes
Dendrites (afferent**)
Axon (efferent**)
Dendrites In motor neurons how many?
100s of short, tapering, diffusely branched processes
Receptive (input) region of neuron
Large surface area for information collection
Synapses with other neurons (bring info to dend)
Convey incoming messages toward cell body as graded potentials (short distance signals)
In many brain areas fine dendrites specialized
Collect information with dendritic spines
Appendages with bulbous or spiky ends
Dendrites
Receive info from sensory receptors or other neurons
Processes allow large surface cuz a lot of info
Graded potential = ap but shorte distance r, ap goes a meter about
Slightly mylienated, no schwann cells
Specialized due to information goes to specific motor movement ex) vision different from moving arm or leg
Dendrites
Describe Axon Structure
One axon per cell arising from axon hillock
Cone-shaped area of cell body
In some neurons, the axon is short or absent (no msg)
In others, encompasses most of the length of neuron
Some 1 meter long
Long axons called nerve fibers
Occasional branches (axon collaterals)
Branches profusely at end (terminus)
Can be 10,000 terminal branches
Distal endings called axon terminals or terminal boutons
Long axons are called ?
nerve fibers
axon collaterals
Occasional branches
Branches profusely at end
terminus
distal endings are called what?
axon terminals or terminal boutons
more common is axon terminals
Axon absent are during
depol for other cells
Nerve fibers are collections
of axons
axon functional characteristics
Conducting region of neuron
Generates nerve impulses
Transmits them along axolemma (neuron cell membrane) to axon terminal
Secretory region (not where they are produced)
Neurotransmitters released into extracellular space
Either excite or inhibit neurons with which axons in close contact
Carries on many conversations with different neurons at same time (through electrical gradients)
Lacks rough ER and Golgi apparatus (don’t create protein)
Relies on cell body to renew proteins and membranes
Efficient transport mechisms for proteins and memrbanes
Quickly decay if cut or damaged (take a long time to regenerate)
What is the conducting region of the neuron?
axon
What part of neuron generates nerve impulses?
axon
What part of neuron transmits nerve impulses along the axolemma (neuron cell membrane) to axon terminal?
axon
What part of neuron is the secretory region of nerve impulses?
axon
Neurotransmitters released into extracellular space
and cause?
Either excite or inhibit neurons with which axons in close contact
What carries on many conversations with different neurons at same time (through electrical gradients)?
axon
What Lacks rough ER and Golgi apparatus (don’t create protein)?
axon
What Relies on cell body to renew proteins and membranes
axon
What Efficient transport mechisms for proteins and memrbanes?
axon
What will Quickly decay if cut or damaged (take a long time to regenerate)?
axon
Axons conduct info
away from the body
The myelin sheath is comprised of
mylein
Mylein
Whitish, protein-lipoid substance
Segmented sheath around most long or large-diameter axons
Dendrites are always non-myelinated (they have shwann cells)
Myelinated fibers
Function of myelin
Protects and electrically insulates axon
Increases speed of nerve impulse transmission
Nonmyelinated fibers conduct impulses more slowly
Mylein sheath
What is a Segmented sheath around most long or large-diameter axons?
mylein sheath
Dendrites are always non-myelinated or myelinated?
Dendrites are always non-myelinated (they have shwann cells)
2 functions of mylein
Protects and electrically insulates axon
Increases speed of nerve impulse transmission
What fiber conducts nerve impulses more slowly?
nonmyleninated fibers
mylein sheath is similar to what in your afsc?
welding coat on electrode that insulates the weld
jumps arc
Myelination in the PNS
Formed by schwann cells
Wrap around axon in jelly roll fashion
One cell forms one segment of myelin sheath
Myelin sheath
Concentric layers of schwann cell plasma membrane around axon
Outer collar of perinuclear cytoplasm (formerly called neurilemma)
Peripheral bulge of schwann cell containing nucleus and most of cytoplasm
How is myelination formed in PNS?
Formed by schwann cells
Wrap around axon in jelly roll fashion
One cell forms one segment of myelin sheath
What makes up myelin sheath in PNS?
Concentric layers of schwann cell plasma membrane around axon
Outer collar of perinuclear cytoplasm (formerly called neurilemma) is made of what?
Peripheral bulge of schwann cell containing nucleus and most of cytoplasm
Process of Myelination in PNS 3 steps
1.) Schwann cell develops an axon
2.) The Schwann cell then rotates
around the axon, wrapping its
plasma membrane loosely around
it in successive layers.
What gets damaged in ALS?
Myelination in PNS because Schwann cells get damaged and messes everything else up
Plasma membranes of myelinating cells have
less protein
Why do Plasma membranes of myelinating cells have
less protein?
No channels or carriers (don’t conduct electrical impulse)
Good electrical insulator
Interlocking proteins bind adjacent myelin membranes
Nodes of ranvier
(conduction of electrical impulse across the axon)
like arc welding
2 aspects of nodes of ranvier
Myelin sheath gaps between adjacent schwann cells
Sites where axon collaterals can emerge
Nonmyelinated fibers are
Thin fibers not wrapped in myelin; surrounded by schwann cells but no coiling; one cell may surround 15 different fibers
Myelin Sheaths in the CNS formed by
Formed by multiple, flat processes of oligodendrocytes, not whole cells
Myelin Sheaths in the CNS wrap how many axons at once
60 axons at once
Are nodes of ranvier present in Myelin Sheaths in the CNS formed by
Nodes of ranvier are present
No outer collar of perinuclear cytoplasm in Myelin Sheaths in the CNS
No outer collar of perinuclear cytoplasm
size of fibers and covered by what in Myelin Sheaths in the CNS
Thinnest fibers are unmyelinated
Covered by long extensions of adjacent neuroglia
White matter
Regions of brain and spinal cord with dense collections of myelinated fibers – usually fiber tracts
Gray matter
Mostly neuron cell bodies and nonmyelinated fibers
Function in gray matter
processing
What matter has role in MS and axons ?
white matter
Sensory Neurons
Transmit impulse from sensory receptors in skin/organs twd cns (integration)
Almost all are Unipolar
Sensory Neurons are what kind of polar?
unipolar
Where are the sensory neuron cell bodies located?
Cell bodies in ganglia in PNS
Motor Neurons Carry impulsess
from CNS to effectors
Motor Neurons are what polar?
Multipolar
Where are cell bodies of motor neurons located?
Most cell bodies in CNS (except some autonomic neurons)
Interneurons
(association neurons)
Where are interneurons located?
Lie btw motor and sensory neurons
What do interneurons do? Where?
Shuttle signals through CNS pathways where integration of information occurs; most are entirely within CNS
What are 99% of body’s neurons?
interneurons
Where are interneurons confined?
Most confined in CNS
Neurons are highly what (membrane potential)?
irritable
Neurons respond to what > (membrane potential)?
Respond to adequate/threshold stimulus by generating an action potential (nerve impulse) along the axon length
What is the impulse always in neurons regardless of what?
Impulse is always the same regardless of stimulus
what is the resting membrane potential?
Potential difference across membrane of resting cell
Numeric value for resting membrane potential and how come?
Approximately –70 mV in neurons (cytoplasmic side of membrane negatively charged relative to outside)
What is the actual voltage difference numeric value in resting membrane potential?
Actual voltage difference varies from -40 mV to -90 mV
What is membrane in resting potential termed?
Membrane termed polarized
What is the resting membrane potential generated by? 2 things
Generated by:
Differences in ionic makeup of ICF and ECF
Differential permeability of the plasma membrane
How is that generated by Differences in ionic makeup of ICF and ECF
Differential permeability of the plasma membrane? 2 things again
Higher K concentration inside the cell with protein anions creating a negative membrane charge
Large concentration of Na+ outside the cell making the outside environment more positive
Differences in Plasma Membrane Permeability Characteristics in Nerve cell
Impermeable large anionic proteins
Slightly permeable to Na+ (through leakage channels)
25 times more permeable to K+ than sodium (more leakage channels)
Potassium diffuses out of cell down concentration gradient
Quite permeable to Cl–
What happens with K+ during plasma membrane resting potential in nerve cell?
More potassium diffuses out than sodium diffuses in
What does Na+ K+ Pump do in resting membrane potential of nerve cell?
Sodium-potassium pump stabilizes resting membrane potential
How does sodium potassium pump work in resting memb potential in nerve cell?
Maintains concentration gradients for Na+ and K+
3 Na+ pumped out of cell; 2 K+ pumped in
Membrane potential changes when
Concentrations of ions across membrane change
Membrane permeability to ions changes
Changes produce two types signals
Graded potentials
Action potentials
Graded potentials
Incoming signals operating over short distances
Action potentials
Long-distance signals of axons
What do changes in membrane potential do in nerve cells?
Changes in membrane potential used as signals to receive, integrate, and send information
Terms of change of membrane potential are relative to what potential?
Terms describing membrane potential changes relative to resting membrane potential
What is occurring in depolarization of nerve cell membrane?
Decrease in membrane potential (toward zero and above)
Inside of membrane becomes less negative than resting membrane potential
Increases probability of producing a nerve impulse
Either graded or action potential
depolarization increases the probablity of what? what are they called?
Increases probability of producing a nerve impulse
Either graded or action potential
Hyperpolarization what occurs?
An increase in membrane potential (away from zero)
Inside of cell becomes more negative than resting membrane potential)
Hyperpolarization reduces probablity of ?
Reduces probability of producing a nerve impulse
Hyperpolarization is the action of what kind of drugs?
Action of anti-anxiety medicine
Why does hyperpolarization provide the reaction that it does?
No neural stimulus, keeps you relaxed since it reduces probability of producing a nerve impulse
How long are grade potentials and why?
Short-lived, localized changes in membrane potential
Magnitude varies with stimulus strength
Stronger stimulus more voltage changes; farther current flows
Graded potential is what polarization wave?
Either depolarization or hyperpolarization
Graded potential are triggered by what?
Triggered by stimulus that opens gated ion channels
GRADED POTENTIAL current flows and how?
Current flows but dissipates quickly and decays
Graded potentials are signals only over short distances
Positive ions move toward negative charges, therefore the charge flows in one direction
Why does Membrane potential decays with distance?
Because current is
lost through the “leaky” plasma membrane, the voltage declines with
distance from the stimulus (the voltage is decremental).
Consequently, graded potentials are short-distance signals.
What is AP?
Brief reversal of membrane potential with a change in voltage of ~100 mV
How are AP different from GP?
Do not decay over distance as graded potentials do
How does depolarization activate AP?
Depolarizing local currents open voltage-gated Na+ channels
Na+ influx causes more depolarization which opens more Na+ channels ICF less negative
What happens at threshold for depolarizaton to activate AP?
At threshold (–55 to –50 mV) positive feedback causes opening of all Na+ channels a reversal of membrane polarity to +30mV Spike of action potential
Repolarizing phase what happens?
Na+ channel slow inactivation gates close
Membrane permeability to Na+ declines to resting state
Slow voltage-gated K+ channels open
K+ exits the cell and internal negativity is restored
What stops increasing during repolarization
AP spike stops rising
What happens during hyper polarization?
Some K+ channels remain open, allowing excessive K+ efflux
This causes hyperpolarization of the membrane (slight dip below resting voltage)
Na+ channels begin to reset
What does hyperpolzartion do resting voltage?
This causes hyperpolarization of the membrane (slight dip below resting voltage)
What is constantly leaving during hyper polarization?
K constnaly leaving cell causes hyperpolarization
What happens with ions in Resting state?
No ions move through voltage-gated
channels.
Depolarization is caused by what ion?
Na+ flowing into the cell
Repolarization is caused by ion?
K+ flowing
out of the cell.
Hyperpolarization is
caused by
K+ continuing to
leave the cell.
What do not all depolarization events yield?
Not all depolarization events produce APs
What does an axon need to get triggered by?
For axon to “fire”, depolarization must reach thresholdThat voltage at which the AP is triggered
What happens at threshold during depolarization?
At threshold:
Membrane has been depolarized by 15 to 20 mV
Na+ permeability increases
Na influx exceeds K+ efflux
What cycle begins after threshold?
The positive feedback cycle begins
What kind of phenomenon is threshold?
All-or-None phenomenon
An AP either happens completely, or it does not happen at all
What is ALL or none phenomenon ?
All-or-None phenomenon
An AP either happens completely, or it does not happen at all
propagation
increase in numbers
spreading
Propagation allows
AP to serve as a signaling device
AP is a
signaling device
By propagation, what happens with ions?
Na+ influx causes local currents (electrical flow)
how does Na+ influx causes local currents (electrical flow)?
Local currents cause depolarization of adjacent membrane areas in direction away from AP origin (toward axon’s terminals)
Local currents trigger an AP there: From positive to negative, one way propagation
This causes the AP to propagate AWAY from the AP origin
Since Na+ channels closer to AP origin are (propagation)
inactivated no new AP is generated there
Once initiated an AP is what and how so?
self-propagating
In nonmyelinated axons each successive segment of membrane depolarizes, then repolarizes
Propagation in myelinated axons differs
Absolute refractory period is?
When voltage-gated Na+ channels open neuron cannot respond to another stimulus
Absolute refractory period Ensures
that each AP is an all-or-none event
Absolute refractory period Enforces
one-way transmission of nerve impulses
Conduction velocities of neurons
vary widely
Rate of AP propagation depends on
Axon diameter
Degree of myelination
Continuous conduction in unmyelinated axons is slower than saltatory conduction in myelinated axons
Function/ role of myelin sheath
Myelin sheaths insulate and prevent leakage of charge
Fasted conduction
Saltatory conduction (possible only in myelinated axons) is about 30times faster
Why is saltatory conduction the fastest?
think about arc welding
Voltage-gated Na+ channels are located at myelin sheath gaps
APs generated only at gaps
Electrical signal appears to jump rapidly from gap to gap
In bare plasma membranes, voltage decays.
Without voltage-gated channels, as on a dendrite,
voltage decays because current leaks across the
membrane.
In nonmyelinated axons, conduction is slow
continuous conduction
Voltage-gated Na+ and K+
channels regenerate the action potential at each point
along the axon, so voltage does not decay. Conduction
is slow because it takes time for ions and for gates of
channel proteins to move, and this must occur before
voltage can be regenerated.
In myelinated axons, conduction is fast (saltatory
conduction).
Myelin keeps current in axons
(voltage doesn’t decay much). APs are generated only
in the myelin sheath gaps and appear to jump rapidly
from gap to gap.
Group A fibers
Large diameter, thickly myelinated somatic sensory and motor fibers of skin, skeletal muscles, joints
Group B fibers
Intermediate diameter, lightly myelinated fibers
Group C fibers
Smallest diameter, unmyelinated ANS fibers
Why does nervous system work?
Nervous system works because information flows from neuron to neuron
What are Neurons functionally connected by ?
synapses
Synapses are what? how?
Junctions that mediate information transfer From one neuron to another neuron Or from one neuron to an effector cell
Presynaptic neuron role
Sends the information
Postsynaptic neuron location
(in PNS may be a neuron, muscle cell, or gland cell)
Postsynaptic neuron function
Receives the information
Postsynaptic neuron and Presynaptic neuron can what?
Most function as both
Transmission crosses what?
synaptic cleft
Tranmission across the synaptic cleft is what kind of event?
Chemical event (as opposed to an electrical one)
Synaptic cleft depends on what?
Depends on release, diffusion, and receptor binding of neurotransmitters
Synaptic cleft Ensures
Ensures unidirectional communication between neurons
AP arrives at what during transmission across chem synapsis?
axon terminal of presynaptic neuron
Info transfer across synaspes causes what? and how?
Causes voltage-gated Ca2+ channels to open
Ca2+ floods into cell
Synaptotagmin protein binds (info transfer chem synapse)
Ca2+ and promotes fusion of synaptic vesicles with axon membrane
What occurs after synaptotagmin protein binding during info transfer chem synapse ? and higher what ?
Exocytosis of neurotransmitter into synaptic cleft occurs
Higher impulse frequency –> more released
What diffuses across synapse during info chem transfer ?
Neurotransmitter diffuses across synapse
Neurotransmitter does what in chem transfer in synapse? how so?
Binds to receptors on postsynaptic neuron
Often chemically-gated ion channels
What are opened when there are neurotransmitter transmitted across synapse chem? What does that cause?
Ion channels are opened
Causes an excitatory or inhibitory event (graded potential)
Neurotransmitter effects terminated
Neurotransmitters are considered to be what of the nervous system?
Language of nervous system
How many neurotransmitter have been id?
50 or more neurotransmitters have been identified
What are neurotransmitters made up of? this exerts what?
Most neurons make two or more neurotransmitters
Neurons can exert several influences
When are neurotransmitters usually released?
Usually released at different stimulation frequencies
Neurotransmitters are classified by what?
Classified by chemical structure and by function
Acetylcholine
(ACh)
What neurotransmitter was the first identified?
ACh
What neurotransmitter is the best understood?
ACh
ACh is released by what?
Released at neuromuscular junctions ,by some ANS neurons, by some CNS neurons
ACh is synthesized from what?
Synthesized from acetic acid and choline by the enzyme choline acetyltransferase
ACh is degraded by what?
Degraded by enzyme acetylcholinesterase (AChE)
ACh is released by ?
Released by all neurons that stimulate skeletal muscles
ACh excitatory by what muscle?
Excitatory: Skeletal muscle
ACh inhibitory by what tissue?
Inhibitory: Cardiac tissue
How are neurotransmitters classified by?
chem structure
4 Chem structure classifications of neurotransmitters
- ) Biogenic Amines
- ) Amino Acids
- ) Peptides (Neuropiptides)
- ) Gases and Lipids (gasotransmitters)
Biogenic Amines 2 groups that make them up
Catecholamines
Indolamines
Catecholamines consist of …?
Dopamine, norepinephrine (NE), and epinephrine
Catecholamines are synthesized from?
Synthesized from the amino acid tyrosine
Indolamines
Serotonin and histamine
What is serotonin synthesized from ?
Serotonin synthesized from amino acid tryptophan;
What is histamine synthesized?
histamine synthesized from amino acid histidine
Biogenic Amines are distributed in brain how?
Broadly distributed in brain
Biogenic amines play a role in what?
Play roles in emotional behaviors and biological clock
Some ANS motor neurons release (especially NE)
Biogenic amines
What type of chem functional enzyme has Imbalances associated with mental illness
Biogenic amines
What 4 amino acids are chemical structure neurotransmitters?
Glutamate
Aspartate
Glycine
GABA—gamma ()-aminobutyric acid
Neuropeptides consist of what 3 ?
Substance P
Endorphins
Gut-brain peptides
Substance P role
Mediator of pain signals
Endorphins kinds
Beta endorphin, dynorphin and enkephalins
Endorphins act as what?
Act as natural opiates; reduce pain perception
Example of endorphins
Runners high
Gut-brain peptides types
Somatostatin and cholecystokinin
Examples of gasotransmitters
Nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide gases (H2S)
Gasotransmitters bind with what?
Bind with G protein–coupled receptors in the brain
gasotransmitters are what soluble?
Lipid soluble
Gasotransmitters are synthesized how?
Synthesized on demand
NO (g) gasotransmitter is involved in ?
NO involved in learning and formation of new memories; brain damage in stroke patients, smooth muscle relaxation in intestine
H2S acts as how?
H2S acts directly on ion channels to alter function
Effects of Neurotransmitter (two things)
excitatory versus inhibitory
Neurotransmitter effect can be what?
Neurotransmitter effects can be excitatory (depolarizing) and/or inhibitory (hyperpolarizing)
How is neurotransmitter effected by?
Effect determined by receptor to which it binds
GABA and glycine usually are what neurotransmitter effect?
inhibitory
Glutamate usually are what neurotransmitter effect ?
excitatory
How do ACh an NE work?
Acetylcholine and NE bind to at least two receptor types with opposite effects
ACh works how for skel muscle?
ACh excitatory at neuromuscular junctions in skeletal muscle
ACh functions how for cardiac muscle?
ACh inhibitory in cardiac muscle
How do neurons function?
Neurons function in groups
The neuron groups contribute to what?
Groups contribute to broader neural functions
Where are there billion of neurons?
There are billions of neurons in CNS
Why are there billions of neurons?
Must be integration so the individual parts fuse to make a smoothly operating whole
CNS is made up?
brain and spinal cord
What are the 4 adult brain regions?
1) Cerebral hemispheres
2) Diencephalon
3) Brain stem (midbrain, pons, and medulla)
4) Cerebellum
Brain
Similar pattern
Additional areas of gray matter in brain
Cerebral hemispheres and cerebellum
Cortex disappears in brain stem
Ventricles: 4 ventricles
What are ventricles of brain filled with?
Filled with cerebrospinal fluid (CSF)
Ventricles in brain are connected how?
Connected to one another and to central canal of spinal cord
Lateral ventricleS and third ventricle connected by what?
Lateral ventricles third ventricle via interventricular foramen
Third and and fourth ventricle are connected via?
Third ventricle fourth ventricle via cerebral aqueduct
Cerebral Hemispheres are what?
Surface markings
What are the cerebral hemispheres are surface markings identified by?
Elevated ridges (gyri), shallow grooves (sulci), and deep grooves (fissures) Longitudinal fissure
Transverse cerebral fissure
What are the 5 lobes of the cerebral hemispheres?
1) Frontal
2) Parietal
3) Temporal
4) Occipital
5) Insula
Central sulcus of cerebral hemispheres is what ?
Separates precentral gyrus of frontal lobe and postcentral gyrus of parietal lobe
Parieto-occipital sulcus Separates
occipital and parietal lobes
Lateral sulcus outlines the?
temporal lobes
Insula is what?
Fifth lobe of the cerebral hemisphere, buried within the lateral sulcus
Three basic regions of Cerebral Hemispheres
Cerebral cortex of gray matter superficially
White matter internally (communication)
Basal nuclei deep within white matter
Cerebral cortex
of gray matter superficially
White matter
internally (communication)
Basal nuclei deep
within white matter
Thin (2–4 mm) superficial layer of gray matter
40% mass of brain
Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding
Cerebral Cortex
What is the Thin (2–4 mm) superficial layer of gray matter
Cerebral cortex
What is 40% mass of brain?
Cerebral cortex
What part of the region of the cerebral hemisphere is the site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding?
Cerebral cortex
4 General Considerations of Cerebral Cortex
1) Three types of functional areas
1. ) Motor areas
2. ) Sensory areas
3. ) Association areas
2) Each hemisphere concerned with contralateral side of body
3) Lateralization (specialization)of cortical function in hemispheres
4) Conscious behavior involves entire cortex in some way
- No functional region of the brain acts alone
What is the Primary Motor Cortex located?
Located in the large pyramidal cells of precentral gyri
In Primary Motor Cortex there are Long axons that are called
pyramidal (corticospinal) tracts of spinal cord: Voluntary motor tracts
Function of Primary Motor Cortex
Allows conscious control of precise, skilled, skeletal muscle movements
In Primary Motor Cortex, Motor homunculi -
upside-down caricatures represent contralateral motor innervation of body regions
Premotor cortex does what?
Helps plan movements; staging area for skilled motor activities
Premotor cortex controls what?
Controls learned, repetitious, or patterned motor skills (typing, musical instrument) , and Controls voluntary actions that depend on sensory feedback
Premotor cortex coordinates what?
Coordinates simultaneous or sequential actions
Broca’s Area location
Present in one hemisphere (usually the left)
Broca’s area functions
Motor speech area that directs muscles of speech production
Broca’s area active in?
Active in planning speech and voluntary motor activities
Frontal Eye Field Controls
Controls voluntary eye movements
What are the sensory areas of the cerebral cortex?
Conscious awareness of sensation Occur in parietal, insular, temporal, and occipital lobes �Primary somatosensory cortex Somatosensory association cortex Visual areas Auditory areas �Vestibular cortex Olfactory cortex Gustatory cortex Visceral sensory area�
Anterior Association Area is aka what?
Prefrontal Cortex
What is the most common cortical region?
(Prefrontal Cortex) Anterior Association Area
(Prefrontal Cortex)Anterior Association Area is involved in what?
Involved with intellect, cognition, recall, and personality
What contains working memory needed for abstract ideas, judgment, reasoning, persistence, and planning ?
(Prefrontal Cortex)Anterior Association Area
Development depends on what in Prefrontal Cortex or Anterior Association Area?
feedback from social environment
Posterior Association Area is what region? and size?
Large region in temporal, parietal, and occipital lobes
What Plays role in recognizing patterns and faces and localizing us in space?
Posterior Association Area
What is Involved in understanding written and spoken language (Wernicke’s area)?
Posterior Association Area
Limbic Association Area is part of what?
Part of limbic system
What Involves cingulate gyrus, parahippocampal gyrus, and hippocampus?
Limbic Association Area
What provides emotional impact that makes scene important and helps establish memories ?
Limbic Association Area
In Lateralization of Cortical Function what are almost identical?
hemispheres
Lateralization -
division of labor between hemispheres
What is lateralization also called?
Also called split-brain concept
Cerebral dominance -
hemisphere dominant for language (left hemisphere - 90% people), mathematics, and logic
Left hemisphere (Lateralization of Cortical Function)
tba
Right hemisphere (Lateralization of Cortical Function)
tba
How quickly do the hemispheres communicate and how they do this?
Hemispheres communicate almost instantaneously via fiber tracts and functional integration
Cerebral White Matter is what?
Myelinated fibers and tracts
Cerebral White Matter does what?
Communication between cerebral areas, and between cortex and lower CNS
What 3 fibers make up Cerebral white matter?
Association fibers
Commissural fibers
Projection fibers
Association fibers—
horizontal; connect different parts of same hemisphere
Commissural fibers—
horizontal; connect gray matter of two hemispheres
Projection fibers—
vertical; connect hemispheres with lower brain or spinal cord
what makes up the Basal nuclei/ganglia?
Subcortical nuclei
- Caudate nucleus
- Putamen
- Globus pallidus
Caudate nucleus + putamen =
striatum
Putamen + globus pallidus =
lentiform nucleus
What is basal nuclei/ganglia associated with?
Associated with subthalamic nuclei (diencephalon) and substantia nigra (midbrain)
Basal nuclei 5 functions
Functions thought to be
1 Influence muscle movements
2 Role in cognition and emotion
3 Regulate intensity of slow or stereotyped movements
4 Filter out incorrect/inappropriate responses
5 Inhibit antagonistic/unnecessary movements
What Influence muscle movements?
Basal Nuclei
What part of brain has role in cognition and emotion?
Basal Nuclei
What Regulate intensity of slow or stereotyped movements?
Basal Nuclei
what Filter out incorrect/inappropriate responses?
Basal nuclei
What Inhibit antagonistic/unnecessary movements?
basal nuclei
What Three paired structures make up the Diencephalon ?
Thalamus
Hypothalamus
Epithalamus
What Encloses third ventricle?
Diencephalon
What is Gateway to cerebral cortex?
Thalamus
What Sorts, edits, and relays ascending input?
Thalamus
The Thalamus sorts, edits, and relays ascending inputs that what??
Impulses from hypothalamus for regulation of emotion and visceral function
Impulses from cerebellum and basal nuclei to help direct motor cortices
Impulses for memory or sensory integration
What Mediates sensation, motor activities, cortical arousal, learning, and memory?
Thalamus
What Controls autonomic nervous system (e.g., blood pressure, rate and force of heartbeat, digestive tract motility, respiration, pupil size, etc.)?
Hypothalamus
What takes a part in the Physical responses/manifestations to emotions (limbic system)?
Hypothalamus
Example of the hypothalamus with Physical responses/manifestations to emotions (limbic system):
Perception of pleasure, fear, and rage, and in biological rhythms and drives (sex drive)
What Regulates body temperature – sweating/shivering?
Hypothalamus
What Regulates hunger and satiety in response to nutrient blood levels or hormones?
Hypothalamus
What Regulates water balance and thirst?
hypothalamus
What is example of how the hypothalamus Regulates water balance and thirst?
ADH from pituitary to increase water concentration
What Regulates sleep-wake cycles?
Hypothalamus
Suprachiasmatic nucleus
(biological clock)
What Controls endocrine system?
hypothalamus
How does hypothalamus control endocrine sys?
Produces releasing hormones
Controls hormone secretions of anterior pituitary gland (adenohyp)
Produces posterior pituitary (neurohypophosis) hormones
What are posterior pit hormones?
ADH
Oxytocin
What are 3 regions of the brain stem?
Midbrain
Pons
Medulla oblongata
How is the brain stem different to spinal cord?
Similar structure to spinal cord but contains nuclei embedded in white matter
what Controls automatic behaviors necessary for survival
Brain stem
What Contains fiber tracts connecting higher and lower neural centers?
brain stem
The nuclei of brain stem are associated with what?
Nuclei associated with 10 of the 12 pairs of cranial nerves
What separates pons and cerebellum?
Fourth ventricle seperates pons and cerebellum
Fibers of pons do what?
Connect higher brain centers and spinal cord
Relay impulses between motor cortex and cerebellum
Origin of cranial nerves are (pons) ?
V (trigeminal), VI (abducens), and VII (facial)
Pons nuclei 2 things about them
Some nuclei of reticular formation
Nuclei help maintain normal rhythm of breathing
Medulla oblongata Joins?
spinal cord at foramen magnum
Medulla oblongata forms?
Forms part of ventral wall of fourth ventricle
Medulla oblongata contains?
Contains choroid plexus of fourth ventricle
Medulla oblongata pyramids have what?
Pyramids—contains two ventral longitudinal ridges formed by pyramidal tracts
MEdulla oblongata Decussation of the pyramids—
crossover of corticospinal tracts
Inferior olivary nuclei of medulla oblongata
—relay sensory information from muscles and joints to cerebellum
Cranial nerves VIII, IX, X, and XII are associated with what?
medulla
Vestibular nuclei (pons and medulla)—
mediate responses that maintain equilibrium
Several nuclei (e.g., nucleus cuneatus and nucleus gracilis) does what ?
relay sensory information to the somatosensory cortex
Functions of Medulla oblongata
Autonomic reflex center Functions overlap with hypothalamus Hypothalamus relays instructions via medulla Cardiovascular center Cardiac center
Vasomotor center Respiratory centers Generate respiratory rhythm Control rate and depth of breathing (with pontine centers) Additional centers: Regulate Vomiting Hiccuping Coughing Swallowing Sneezing
11% of brain mass is what?
Cerebellum
What is Dorsal to pons and medulla?
cerebellum
What gets Input from cortex, brain stem and sensory receptors ?
cerebellum
What
Allows smooth, coordinated movements?
cerebellum
Cerebellar hemispheres connected by?
vermis
Folia (of cerevellum) —
transversely oriented gyri
Each hemisphere of cerebellum has what?
three lobes
What are 3 lobes of each hemisphere of the cerebellum called?
Anterior, posterior, and flocculonodular
Arbor vitae— (cerebellum)
treelike pattern of cerebellar white matter
Cerebellum receives impulses from what ?
cerebral cortex of intent to initiate voluntary muscle contraction
Cerebellum signals are from?
Signals from proprioceptors and visual and equilibrium pathways continuously “inform” cerebellum of body’s position and momentum
Cerebellar cortex calculates what?
the best way to smoothly coordinate muscle contraction
Last step of cerebellum processing?
“Blueprint” of coordinated movement sent to cerebral motor cortex and brain stem nuclei
2 Cognitive Functions of Cerebellum�
Role in thinking, language, and emotion
May compare actual with expected output and adjust accordingly
�
Limbic System is what part of the brain?
Emotional or affective brain
What 2 are two parts of limbic system?
Amygdaloid body
Cingulate gyrus
Amygdaloid body—
recognizes angry or fearful facial expressions, assesses danger, and elicits fear response
Cingulate gyrus—
role in expressing emotions via gestures, and resolves mental conflict
What Puts emotional responses to odors?
Example: skunks smell bad
Limbic system
Where is Most output relayed via hypothalamus?
Limbic sys
What interacts with prefrontal lobes?
Limbic sys
What does the limbic sys interacts with prefrontal lobes do?
React emotionally to things we consciously understand to be happening
Consciously aware of emotional richness in our lives
Hippocampus and amygdaloid body play a role in what?
play a role in memory
What Sends impulses to cerebral cortex to keep it conscious and alert?
Reticular activating system (RAS)
This Filters out repetitive, familiar, or weak stimuli (~99% of all stimuli!)
Reticular activating system (RAS)
What has Strong impulses reach our consciousness?
RAS
What is Inhibited by sleep centers, alcohol, drugs?
RAS
A Severe injury of what results in permanent unconsciousness (coma)?
RAS
What RAS motor function?
Helps control coarse limb movements
Reticular autonomic centers regulate visceral motor functions
What are centers in RAS for motor function?
Vasomotor centers
Cardiac center
Respiratory centers
Memory
Storage and retrieval of information
What are the 2 stages of memory?
Short-term memory
Long-term memory
Short-term memory
(STM, or working memory)—temporary holding of information; limited to seven or eight pieces of information
Long-term memory has
limitless capacity (LTM)
Brain Structures Involved in Memory
Hippocampus and surrounding temporal lobes function in consolidation and access to memory
ACh from basal forebrain is necessary what?
for memory formation and retrieval
4 protections of BRain
- )Bone (skull)
- )Membranes (meninges)
- )Watery cushion (cerebrospinal fluid)
- ) Blood brain barrier
Membranes (meninges) cover and protect?
CNS
Protect blood vessels and enclose venous sinuses
Membranes (meninges) contain
Contain cerebrospinal fluid (CSF)
Membranes (meninges) form
Form partitions in skull
How many layers do Membranes (meninges) have and what are they called?
Dura mater
Arachnoid mater
Pia mater
Meningitis
Inflammation of meninges
Dura Mater latin words
Tough Mother
What is the Strongest meninx?
Dura Mater
Dura Matter definition
Two layers of fibrous connective tissue (around brain) separate to form dural venous sinuses
Middle layer with weblike extensions is what?
Arachnoid Mater
What is Separated from dura mater by subdural space?
Arachnoid Mater
What has Subarachnoid space ?
Arachnoid Mater
Subarachnoid space contains
contains CSF and largest blood vessels of brain
Arachnoid villi of Arachnoid Mater protrude into superior sagittal sinus and permit . . .?
CSF reabsorption into the venous blood
Pia Mater latin
Gentle mother
What is Pia Matter?
Delicate vascularized connective tissue that clings tightly to brain
CSF is Synthesized by what?
choroid plexus in epithalamus
CSF composition
Watery solution formed from blood plasma
Less protein and different ion concentrations than plasma
CSF has a constant what?
Constant volume
CSF provides? ow?
Gives buoyancy to CNS structures
Reduces weight by 97%
CSF function/ role
Protects CNS from blow and other trauma
Nourishes the brain and carries chemical signals
Blood Brain Barrier helps?
Helps maintain stable environment for brain
Blood brain barrier separates what?
Separates neurons from some bloodborne substances
Cellular make up Blood brain barrier?
Continuous endothelium of capillary walls
Tight junctions
What kind of barrier does the blood brain barrier have?
selective barrier
The selected barrier of blood brain barrier allows what by how?
Allows nutrients to move by facilitated diffusion
What does Blood Brain Barrier deny?
Metabolic wastes, proteins, toxins, most drugs, small nonessential amino acids, K+ denied
What substances are allowed through the blood brain barrier?
Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics
WHERE IS blood brain barrier absent?
Absent in some areas, e.g., vomiting center and hypothalamus, where necessary to monitor chemical composition of blood
Where does spinal cord begin?
Begins at the foramen magnum (C1)
Where does spinal cord end?
Ends at L1 or L2 vertebra
2 functions of the spinal cord?
Provides two-way communication to and from brain
Contains spinal reflex centers
Protection of spinal cord has what three things?
Bone, meninges, and CSF
Epidural space of spinal cord
Cushion of fat and network of veins in space between vertebrae and spinal dura mater
Where is CSF in spinal cord?
CSF in subarachnoid space
Dural and arachnoid membranes extend to what?
sacrum, beyond end of cord at L1 or L2
Where is site of lumbar puncture or tap?
sacrum, beyond end of cord at L1 or L2
Spinal nerves of spinal cord is part of what ?
PNS
Spinal nerves have how many pairs?
31
Cervical and lumbosacral enlargements of spinal cord
Nerves serving upper and lower limbs emerge here
Cauda equina of gray matter
Collection of nerve roots at inferior end of vertebral canal
Dorsal horns of gray matter-
interneurons that receive somatic and visceral sensory input
Ventral horns of gray matter
some interneurons; somatic motor neurons; axons exit cord via ventral roots
Lateral horns of gray matter
sympathetic neurons
(only in thoracic and superior lumbar regions) -
Dorsal roots of gray matter
– sensory input to cord (afferents)
Dorsal root (spinal) ganglia gray matter—
cell bodies of sensory neurons
Motor pathways involve two neurons:
Upper motor neurons
Lower motor neurons
Upper motor neurons
Pyramidal cells in primary motor cortex
Lower motor neurons
Ventral horn motor neurons
Innervate skeletal muscles
Peripheral Nervous Sys provides what?
Provides links from and to world outside body
What sys is All neural structures outside brain and spinal column?
PNS
What does PNS All neural structures outside brain and spinal column include?
Sensory receptors
Peripheral nerves and associated ganglia
Efferent motor endings
What are Specialized to respond to changes in environment (stimuli)?
Sensory Receptors
Activation of what results in graded potentials that trigger nerve impulses?
Sensory Receptors
Sensation (awareness of stimulus) and perception (interpretation of meaning of stimulus) occur in brain is what neural structure?
Sensory Receptors
Mechanoreceptors—
respond to touch, pressure, vibration, and stretch (tissue deformation)
Thermoreceptors—
sensitive to changes in temperature
Photoreceptors—
respond to light energy (e.g., retina)
Chemoreceptors—
respond to chemicals (e.g., smell, taste, changes in blood chemistry)
Nociceptors—
sensitive to pain-causing stimuli (e.g. extreme heat or cold, excessive pressure, inflammatory chemicals)
What are 5 sensory receptors by stimulus type?
Mechanoreceptors Thermoreceptors Photoreceptors Chemoreceptors Nociceptors
Exteroceptors
Receptors in skin for touch, pressure, pain, and temperature
Most special sense organs
Interoceptors (visceroceptors)
Sensitive to chemical changes, tissue stretch, and temperature changes
Sometimes cause discomfort, hunger, thirst, but usually unaware of their workings
Proprioceptors
Respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles
3 Sensory Receptor by location?
Proprioceptors
Interoceptors (visceroceptors)
Exteroceptors
