Unit 5 Nervous Flashcards
Central nervous system
Brain and spinal cord (inside dorsal bodycavity)
Peripheral nervous system
12 cranial nerves, 31 spinal nerves
Glial cells
‘Glue’ = support cells of neurons
Neuron
Major functional cell, main communicator
Soma
Cell body of neuron ( w/ nucleus etc.)
Process
Extensions from soma
Axon
Processes that connects neuron to its target
Dendrite
Processes that receive info. (Mainly from other neurons)
Gray matter
.neuron cell bodies, dendrites, unmyelinated axons
White matter
Axons W/ fatty coatings (myelin), myelinated axons
Nucleus
Found in CNS
Ganglion
Cluster of cell bodies in PNS
Node of ranvier
Gap in myelin sheath
Axon hillock
Initial segment
Axoplasm
Cytoplasm inside axon
Nissl bodies
Highly developed rough Er of soma
Unipolar(type of neuron)
1 process from soma (most sensory neurons)
Bipolar(type of neuron)
2 processes, rare (retina, olfaction)
Multipolar (type of neuron)
Several processes, most common by far(allmotor and association neurons)
How many glial cells in CNS?
4
Astrocytes (glial)
Maintain extracellular fluid (mop up ions, neurotransmitters); help from blood-brain barrier, least permeable
Ollgodendrocytes (glial)
Provides myelin of CNS
Migroglial cells (glial)
Resident macrophages- gobble up debris
Ependymal (glial)
Help form cerebral spinal fluid from blood plasma; line ventricles and cover each choroid plexus
Ventricles
Fluid filled cavities of CNS
Choroid plexus
Knot of capillaries w/ wehtricles
How many glial cells in PNS?
2
Satellite cells (glial/PNS)
Similar to astrocytes (no blood barrier though)
Schwann cells (glial/PNS)
Myelin sheath of PNS
Nerves
Bundles axons of PNS
Tracts
Bundled axons in CNS
Nervous system functions
Sensory, integration, response
Sensory ( nervous func.)
Sense changes/ stimuli in the env’t (internaland external)
Integration (nervous func.)
Associate stimuli and memories/learning/ emotion to determine responses
Response (nervous func.)
Send response instructions to effectors (glands/muscles) = motor function
Somatic nervous system
Conscious perception and voluntary response, effectors = skeletal muscle
Automatic nervous system
Involuntary control of most organ systems; effectors = smooth + cardiac muscle and glands
Parasympathetic
Rest and digest
Sympathetic
Fight or flight
Enteric nervous system
Autonomous func. Of digestive tract, can operate independent of CNS, contains more neurons of spinal cord
Transmembrane proteins and APs
To separate Lons and generate action potentials, transmembrane proteins required
What is pumped into sodium-potassium pump?
3 na+ pumped out of cell; 2k pumped in
Sodium potassium pump
Responsible for na+ as major extracellular cation, k+ major intracellular cation,ATP required, required to maintain restingmembrane potential
Ion channels
Ion flow by diffusion
Electrochemical exclusion ( ion channels)
Channels allow cations or anions,not both
Size exclusion (ion channels)
Pore size can exclude some ions
Nonspecific channels (ion channels)
Allow multiple ions to diffuse
Gated channels (ion channels)
Must be unlinked to open
Ligand - gated channels
Gated channels, molecules/neurotransmitter binds to channel, channel open, allow diffuse
Mechanically gated channels
Distortion of membrane opens channel, pressure, temp.
Voltage gated channel
Local depolarization (change in voltage)opens
Leakage channels
Open and close at random, neurons have both k+ and na+ leakage channels, Na and K must work constantly
Resting membrane potential
Build up of Na + ions outside, large anions ( proteins, phosphates) inside cell, k+ leaks out, attracts anions too big and wrong charge to pass, na-k pump maintains gradients
AP step 1 and 2
① stimulus causes gated Na channels to open, membrane depolarizes
② if enough Na enters @axon hillock, threshol is reached
Depolarize
Voltage moves closer to zero,membrane becomes ↓ polarized
AP step 3 and 4
③ voltage gated Na channels open
④ Na floods into cell, depolarization continues to + 30mv
AP steps 5 and 6
⑤ voltage gated Na channels close / inactivate
⑥ voltage gated k channels open and K floods out of the cell
Repolarize
Voltage moves back toward RMP
AP steps 7 and 8
⑦ membrane repolarizes
⑧ voltage gated K channels close
AP steps 9 and 10
⑨ membrane hyperpolarizes
10. Voltage gated k channels close
Hyperpolarize
Voltage goes below RMP, membrane over polarized
Refectory periods
AP only occur 1 at a time,
Absolute refectory period
No new AP can be initiated
Relative refectory period
AP possible, but stimulus> than normal threshold
Voltage gated Na channels have 2 gates
Activation/inactivation gate
- both gates must ‘reset’ before next AP possible
-Absolute refectory period = activation
① activation gate
Opens at threshold, Na floods in=depolarization
② inactivation gale
Closes immediately after, Na blocked,k channels open, k floods out= repolarization
- stop ion flow
Un myelinated neurons ( AP propagation )
Continuous conduction
- Na entering triggers adjacent Na gates to open
Myelinated neurons (ap propagation)
Saltatory conduction
- Na gates at nodes of ranvier,myelin prevents ion leakage, ap’s leap between segments
- saltatory 10X faster than continuous
Speed ↑ w/ axon diameter =
Less resistance
Graded potentials
Depend on stimulus strength, AP’S are all or none and all the same, changes in membrane potential that vary m size
Strong stimulus =
↑ graded potential
Generator potentials
Graded potentials or unipolar sensory neuron dendrites
Receptor potentials
Graded potentials of special sensory cells (like rods and cones) that communicate W/ sensory neurons
What do neurotransmitters generate?
Post synaptic potentials ( PSPs)
Excitatory post synaptic potentials(EPSPs)
- Depolarizing (closer to threshold) Na or ca enters
- depolarize membrane
Inhibitory post synaptic potentials (IPSP)
Hyperpolarizes (away from threshold) K exits or Cl enters
Where does graded potential summate?
At axon hillock(initial segment)
- If graded potentials summate to threshold, AP generated
Summation
Graded potentials ‘added up’ @ axon hillock,
Combine to reach threshold of AP
Temporal summation
Rapid succession of excitatory potentials lead to threshold
Spinal summation
Excitatory potential
The synapse - “connection’ between cells
2 types:
Electrical and chemical synapse
Electrical synapse
Gap junctions directly connect neurons (rare)
Chemical synapse
Junction between neurons where signals are transmitted vid the release of chemical messengers called neurotransmitters
Synapse steps 1,2,3
① AP arrives at synaptic end bulb
② voltage -gated ca channels open - Ca enters
③ synapse vesicles motor to presynaptic membrane
Synapse steps 4 and 5
④ neurotransmitters ↑ into synapse cleft via exocytosis
⑤ neurotransmitters diffuse across cleft, bind to receptors on post synaptic membrane
Synapse steps 6 and 7
⑥ receptors change conformation
⑦ neurotransmitters break↓ or re-uptake
Ionotropic receptor ( ligand gated)
Neurotransmitter binds, channel opens, ions flow
Metabotropic receptor
Neurotransmitter binds-metabolism changes ensue
- G protein coupled receptors that active second messenger systems
What is G protein activated by?
By GTP and moves to effector protein
What does effector protein generate?
Generates 2nd messenger (like camp)
What does 2nd messenger cause?
Cause changes (open or close ion channels, activate or deactivate enzymes, change gene transcription)
Where does nervous system develop?
Develop from ectoderm
Remnants of hollow center of neural tube =
CSF filled w/ventricles and central canal
Spinal bitida
Failure of neural tube to close
Occulata(spinal bifida)
‘Hidden’ - vert. Fail to fuse
Meningocele (spinal bitida)
Meninges (protective membranes) protrude
Myelomeningocele ( spinal bifida)
Meninges + spinal nerve
Cerebrum
Largest region of brain
- frontal, parietal, temporal, and occipital, and major landmarks like central sulcus and lateral sulcus
Cerebral cortex
Wrinkly outer few mm of grey matter
- primary sensory, association, integration
Central hemisphere
Right and left symmetrical regions connected by corpus callous
Cortex divided into 4 (or 5) lobes
- Frontal lobe, parietal lobe, temporal, occipital
Gyri and sulci (sulcus )
Gyros = ridges, sulcus = grooves
Lobes defined by prominent gyro and sulcus
Central sulcus
Frontal lobe anterior, parietal lobe posterior
Lateral sulcus
Temporal lobe inferior, occipital lobe posterior
5th lobe: deep to lateral sulcus
Insult
Cerebral contains 3 types of processing regions:
Primary, association, and integration
Primary cortical areas
Sensory info initially processed, or motor commands emerge
Association cortical areas
Adjacent primary areas further process medically
Multimodal integration cortical areas
Found where modality- specific regions meet; process multiple modalities to unify experience
Broadman’S areas =
Specialized cortex regions
Primary motor cortex (broadman’s)
Final motor commands, originate here (precentral gyros)
Primary somatosensory (broadmans)
Perception of general senses
Primary visual (broadmans)
Visual perception (posterior - medial occipital lobe)
Premotor cortex (broadmans)
Muscle memory, planned movements.
Somatosensory association cortex (broadmans)
Sensory memories
Visual association (broadmans)
Visual memories
Primary auditory (broadmans)
Sound perception
Auditory association(broadmans)
Sound memories
Broca’S area (broadman’s)
Language production,muscles for speech
Wernicke’S area (broadmans)
Understanding speech, learning vocab.
Prefrontal cortex (broadmans)
Logic, personality, consciousness, short-term memory (anterior integration area)
Frontal eye field (broadmans)
Eye movement
Subcortical nuclei of the cerebrum
Hippocampus, amygdala, basal forebrain
Hippocampus and amygdala
Emotional response, long-term, memory, major components of lambic system( links autonomic to consciousness motivation)
Basal forebralh
Produces ACH-moderates overall activity of cortex wakefulness
Conus medullaris (spinal cord)
End of cord (=L1 - L2)
Caudal equine (spinal cord)
Roots of lower lumbar, sacral, coccygeal nerves
Filum terminala (spinal cord)
Extension of pla mater, anchors cord
Spinal cord: gray matter
Dorsal (posterior) horn, ventral (anterior) horn, lateral horn
Dorsal (posterior) horn
Entering sensory axons and processing
Ventral (anterior) horn
Somatic motor neuron cell bodies
Lateral horn and sacral lateral horn
Autonomic motor neurons ( T 1- L2 = sympathetic motor,
Sacral lateral horn= parasympathetic motor (autonomic)
Spinal cord: whole matter
Posterior (dorsal) columns, lateral columns, anterior (ventral) columns
Posterior (dorsal) columns
All ascending (sensory) tracts
Lateral columns
Ascending + descending (motor)
Anterior (ventral) columns
Ascending + descending
Dorsal column system (ascending sensory pathways)
( Aka dorsal column) - medial leminscus pathway
What does 1st order neuron ascend w/? (Ascending sensory pathways)
Ascends via fascicles cune atussupper trunk, arms, neck) or fascicles gracilis (lower trunk, legs)
Synapse w/ 2nd order neuron? (Ascending sensory pathways)
WI 2nd order neuron in medulla and decussates (crosses overs
2nd order ascends? (Ascending sensors pathways)
Ascends via medial lemnisces synapses WI 3rd neuron in thalamus
3rd order to cortex? (Ascending sensors pathways)
Fine touch and proprocopion (body position)
Spinothalamic tract
1st order neuron synapses w/ 2nd order neuron in dorsal horn and decessates
- 2nd order ascends via spinothalamic (ventral or lateral)
Sensory homunculus
Contralateral ‘map’ of cortex projection n primary
- Perception depends on where cortex is stimulated-.
Spinocerebellar tract (sensory homunculus)
1st order neuron synapses w/ 2nd order neuron in dorsal horn
- 2nd order ascends, synapses on same Side (spilateral) in cerebellum
- no 3rd neuron
Corticosinal tract (descending pathway)
Large upper motor neurons of primary motor cortex descend to brain stem(canal motor) or spinal cord
- synapse w/ ventral horn
Subcortical nuclei of the cerebrum basal nuclei
3 nuclei:
Caudate nucleus, putamon, globus pallidus
Caudate nucleus + putamen= striatum
Main processing nuclei
. Receive info from various regions, cluster of neuron cell bodies in CNS
Globus pallidas
Main efferent path, excites or inhibits movements
- internal and external segment
Ganglia
Cluster of neuron cell bodies in the PNS
Types of transmembrane protein involved in generating AP
Voltage gated sodium,voltage gated potassium, sodium-potassium pump
Types of gated channels
Voltage-gated, ligand-gated,mechanically gated channels
- leakage channels are always open
Simple steps of AP
Depolarization, depolarization, hyper polarization
- occur do to opening and closing of voltage gated Lon channels
When do active gates open?
Open in response to depolarization
Saltatory conduction
Rapid transmission of AP along myelinated axons, where the impulse jumps from 1 node of ranvier to the next
Threshold
Membrane potential at which an AP is trigged
Basic parts of a chemical synapse
Presynaptic terminal, synaptic cleft, and post synaptic membrane
- they function to transmit signals via neurotransmitters
Types of spina bifida
Occult, meningocele, myclomeningocele
Major subcortical nuclei
Basal nuclei which are involved n movement regulation
Direct pathway of basal nuclei and indnect
Direct: encourage movement, indirect: discourages it
Major neurotransmitters of basal nuclei
Dopamine, GABA, glutamate
Major regions of diencepharon
Thalamus, hypothalamus,and epithalamus
Function of cerebellum
Coordinates movement and balance
Function of cerebella peduncle
Transmits specific types of info,
Major arteries of function of circle of Willis
Internal carotid and basilar artery
- provides collateral blood flow to brain
Major venous return vessels
Include internal jugular veins
What is arachnoid villi associated w/?
Return of CSF to venous system
