patho phys exam 2 Flashcards

1
Q

CHARACTERISTICS OF ACTION POTENTIALS

A

The frequency of action potentials depends on the strength of the stimulus - so the stronger the stimulus, the more frequent the action potential

Action Potentials occur in all or none fashion
- either it happens or it does not
- if the stimulus reaches the threshold then an AP will be generated
- A strong stimulus does not matter, what matters is if it reaches the threshold or not

The speed of action potentials depends on the diameter of nerve fiber & myelination
- if you go through a tunnel that is 3ft it is harder to walk through than a tunnel that is 7ft
- speed is proportional to the diameter of the nerve fiber and myelin sheath

larger stimulus = high frequency of AP = more NTs being released - hot object
smaller stimulus = low frequency of AP = few NTs being released - warm object

difference between a hot and warm object:
- hot object will generate a high frequency of AP because the stimulus is strong
- warm object will generate a low frequency of AP because the stimulus is not as strong

so we cannot change the duration or magnitude of an AP but we can change the frequency and that is how we know the difference between a hot or warm object - they both have different frequencies! :)

simplified:
- strong stimulus = more frequent action potential
- speed of action potentials depends on myelination & diameter of nerve fiber

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2
Q

MYELINATION

A

Schwann cells - make the myelin sheath in the peripheral nervous system while the oligodendrocytes make the myelin sheath in the central nervous system
- roll around the axon over and over again

myelin sheath
- mostly made of lipids

axon

nodes of Ranvier
- where the VGSC & VGPC are
- regions where there is no myelin sheath
- where the APs are generated

Saltatory conduction - the axon has myelin sheath
- increase conduction speed
- Conserves energy
- jumping
- uses nodes of Ranvier
- advantages of myelination
- works less, not generating as much APs

MULTIPLE SCLEROSIS
- Auto-immune disorder: damages the myelin sheath
- Slow or block the propagation of action potentials
- since there’s damage to the myelin sheath: the speed of the AP will be slow and over time the axon will lget affected

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3
Q

TYPES OF NERVE FIBERS

A

THREE TYPES
* Type A: myelinated, transmits cutaneous pressure, touch, cold sensation, mechanical pain & heat pain. Three types: Aa, AB & Agamma
- used for info that needs immediate attention - right because the action potential signal will travel the fastest here so the signal can be transmitted quickly
- biggest diameter and the fastest

  • Type B: myelinated, cutaneous, and subcutaneous mechanoreceptors

Type C: unmyelinated, warm-hot sensation, and mechanical, chemical, & heat-cold induced pain
- used for info that does not need immediate attention - because there is no myelin sheath the signal will not be transmitted as quickly
- no diameter

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4
Q

graded potentials

A

triggering event
- stimulus, a combination of neurotransmitters with receptors or inherent shifts in channel permeability

ion movement producing a change in potential
- net movement of Na+, K+, Cl- or Ca2+ across the plasma membrane by various means

coding of the magnitude of the triggering event
- graded potential change; magnitude varies with the magnitude of the triggering event

duration
- varies with the duration of the triggering event

magnitude of the potential change with distance from the initial site
- decremental conduction; magnitude diminishes with distance from the initial site

refractory period - period where an AP can be regenerated
- none

summation
- temporal, spatial

the direction of potential change
- depolarization or hyperpolarization

location
- specialized regions of the membrane designed to respond to the triggering event

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5
Q

SYNAPSES

A

The junction between two neurons consisting of
* Presynaptic neuron (axon terminals) - before synaptic cleft
* Postsynaptic neuron (dendrites/cell body) - after synaptic cleft
* Synaptic cleft: space in between the two

the AP is coming down the neuron whether it is myelinated or not

components:
synaptic knob

synaptic vesicle

synaptic cleft

subsynaptic membrane

VGCCs

NTs

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6
Q

WORKING OF SYNAPSES

A
  1. AP reaches presynaptic terminal
  2. VGCCs open, Ca++ enters the synaptic knob
  3. NT is released by exocytosis from synaptic vesicle
  4. NT binds to ion channels
  5. LGICs open
  6. Summation of GPs → APs
    - added together and brings membrane potential to threshold
  7. NT is removed quickly
    - tightly regulated
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7
Q

TYPES OF SYNAPSES

A

Excitatory synapse
- when AP reaches this synapse it generates a small EPSP
- generate a small depolarization

Inhibitory synapse
- when AP reaches this synapse it generates a small IPSP
- generate a small hyperpolarization

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8
Q

NEUROTRANSMITTERS VS. NEUROPEPTIDES

A

NEUROTRANSMITTERS
* Small molecules (amino acids)
* Act quickly, destroyed quickly
* Synthesized locally
* Stored in synaptic vesicles
* Most act to open LGICs, others use 2nd messenger systems in the post-synaptic neuron only
* Produce EPSPs or IPSPs

NEUROPEPTIDES
* Large molecules (2-40 AAs)
* Act slowly, prolonged response * Synthesized in cell body
* Stored in dense core vesicles
* Mostly use 2nd messenger systems, can act either pre- or post-synaptically
* Do not produce EPSPs or IPSPs so cannot transmit message from neuron to neuron

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9
Q

SYNAPTIC MODULATIONS

A

what do these modulations do? - Alter synthesis, transport, storage, or release of NT

  • Modify NT interaction with postsynaptic receptors
  • Modify NT reuptake or destruction - is this an SSRI?
  • Replace deficient NT with a substitute
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10
Q

summary

A

presynaptic inputs

postsynaptic neuron

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11
Q

EPSP & IPSP are examples of

graded potentials

action potentials

A

graded potentials

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12
Q

Theoretically speaking, which will generate an action potential faster?

A
Specialized afferent endings

B
Separate receptor cell

A

A
Specialized afferent endings - where the receptor and the nerve fiber are connected

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13
Q

Are neurons the only type of cells present in the CNS?

A
Yes

B
No

A

no
- there are glial cells which are actually 90% of the cells in the CNS

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14
Q

Brain tumors are due to unchecked division of:

A
Neurons

B
Glial cells

C
Both A & B

A

B
Glial cells - BECAUSE neurons do not divide and so if they do not divide then cancer cannot happen in them because canncer has to do with the cells dividing too much
but
glial cells do divide

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15
Q

ORGANIZATION OF THE NERVOUS SYSTEM

A

central nervous system: input to CNS from the afferent periphery, output from CNS to the efferent periphery
- brain and spinal cord

peripheral nervous system
- afferent division
- efferent division

afferent division
- receive sensory stimuli
- visceral stimuli like thirst, hunger

efferent division
- somatic nervous system - skeletal muscles like arms so we can control it
- autonomic nervous system - smooth muscle like heart and lungs so we can not control it

somatic nervous system
- motor neurons

motor neurons
- skeletal muscles

autonomic nervous system
- sympathetic nervous system
- parasympathetic nervous system
- stimuli in the digestive tract enteric nervous system to digestive enzymes only

sympathetic nervous system to the parasympathetic nervous system
- smooth muscle
- cardiac
- exocrine glands
- some endocrine glands

effector organs
- smooth muscle
- cardiac
- exocrine glands
- some endocrine glands
- skeletal muscles

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16
Q

TYPES OF NEURONS

A

Afferent neuron:
- Sends signals to the CNS
- Generates AP from sensory receptors
- Long axon in the PNS

Interneurons:
- Found entirely within CNS
- Lies between afferent & efferent neurons

Efferent neuron:
- Sends signals away from the CNS to effector organs (muscle/gland)
- Long axon in the PNS

pathway of neuronal info.:
peripheral nervous system - afferent neuron
- receive a signal in the sensory receptor - seems to be specialized nerve ending which is faster!
- signal travels through the peripheral axon (afferent fiber)
- cell body (kinda left alone I guess)
- central axon
- axon terminal sends a message to the dendrites of the interneuron

central nervous system - interneuron
- receives message
- sends decisions through axon terminals to the dendrites of the efferent neuron

peripheral nervous system - efferent neuron
- efferent neuron gets message and the message is sent through the axon (efferent fiber) to the axon terminals
- axons terminals release message to the effector organs (muscle or gland)

17
Q

AFFERENT NEURON: SENSORY RECEPTORS

A

SENSORY RECEPTORS
- Photoreceptors - light
- Mechanoreceptors: detect stimuli such as touch, pressure, vibration, and sound from the external and internal environments
- Thermoreceptors: temperature
- Nociceptors: pain
- Osmoreceptors: osmotic pressure
- Chemoreceptor: chemicals like taste

sensory receptors are
- Sensitive to different energy forms
- Responds to a stimulus
- Generates graded potentials and if enough, will generate an action potential

18
Q

afferent sensory receptors

A

sensory receptor is attached to the afferent neuron
1 - in sensory receptors that are specialed afferent neuron endings, stimulus opens stimulus-sensitive channels, permitting net Na+ entry that produces receptor potential

2 - local current flow between depolarized receptor ending and adjacent region opens voltage gated Na+ channels

3 - Na+ entry initiates action potential afferent fiber that self-propagates to CNS

sensory receptor is not attached to the afferent neuron
1 - in sensory receptors that are separate cells, sitmulus opens stimulus-sensitive channels, permitting net Na+ entry that produces receptor potential

2 - this local depolarization opens voltage-gated Ca+ channels

3 - Ca+ entry triggers exocytosis of neurotransmitter

4 - neurotransmitter binding opens chemically gated receptor channels at afferent ending permitting net Na+ entry

5 - resultant depolarization opens voltage-gated Na+ channels in adjacent region

6 - Na+ entry initiates action potential inn afferent fiber that self propagtes to CNS

19
Q

SENSORY RECEPTORS: ADAPTATION

A

Stimuli of same intensity do not produce same magnitude of receptor potentials from the same receptor

TONIC: TONE
- Do not adapt, or adapt slowly - Maintained information about stimulus is valuable
- so the stimulus is received and it is mainatined for a while until stimulus fades
- probably useful for pain

PHASIC: PHASE - Adapts rapidly, but generate an off response on removing the stimulus
- Change in stimulus intensity is important
- so stimulus is received and it is not maintained for a long time
- probably useful for touch that the body does not need to keep track of like putting glassess on your head

20
Q

TRANSMISSION OF STIMULUS

A

Information travels in labeled lines

Sensory units
- Transmit sensory information from the periphery to the CNS

Ascending pathways
- Communicate with reflex networks in spinal cord & travel to thalamus

Processing center
- Relay information from thalamus to cerebral cortex

21
Q

TYPES OF NERVE FIBERS

A

THREE TYPES
* Type A: myelinated, transmit cutaneous pressure, touch, cold sensation, mechanical pain & heat pain. Three types: A, A & A

  • Type B: myelinated, cutaneous and subcutaneous mechanoreceptors
  • Type C: unmyelinated, warm-hot sensation, and mechanical, chemical, & heat-cold induced pain
22
Q

COMPONENTS OF THE CNS

A

Axon terminals of afferent neuron

Interneurons

Dendrites & cell body of efferent neuron

23
Q

glial cells

A

do not send signals: provide physical, metabolic and functional support

90% of cells in CNS

24
Q

GLIAL CELLS

A

ASTROCYTES: star shaped cells
- Supports & guides neurons
- in a 3-D space
- Establishes blood brain barrier (tight junctions)
- Repairs brain injuries
- Takes up neurotransmitters (GABA/glutamate)
- Takes up K+ ions during high frequency APs
- Forms & strengthens synapses: thrombospondin

MICROGLIA
- Immune defenders
- Scavengers
- Secrete NGF - neuronal growth factor

EPENDYMAL CELLS
- Formation & flow of CSF
- Serve as neural stem cells

OLIGODENDROCYTES
- Forms myelin sheath around axons

25
Q

PROTECTION OF THE CNS

A

Bone: protective hard shell
- Cranium (brain)
- Vertebral column (spinal cord)

Mater membranes: protective/ nourishing
- Dura mater: tough, inelastic, outer layer - Arachnoid mater: vascularized, middle
- Pia mater: vascularized, adhering, inner

  • Subdural space: b/w dura & arachnoid
  • Subarachnoid space: b/w arachnoid & piaBlood Brain Barrier

Cerebrospinal fluid: shock absorber

26
Q

BLOOD BRAIN BARRIER

A

CSF is made in the choroid plexus

27
Q

action potentials

A

triggering event
- depolarization to the threshold, usually through the passive spread of depolarization from an adjacent undergoing a graded potential or an action potential

ion movement producing a change in potential
- sequential movement of Na+ into and K+, out of the cell through voltage-gated channels

coding of the magnitude of the triggering event
- all or no membrane response; the magnitude of the triggering event is coded in the frequency rather than the amplitude of action potentials

duration
- constant

magnitude of the potential change with distance from the initial site
- propagated throughout the membrane in an undiminishing fashion; self-regenerated in neighboring inactive areas of the membrane

refractory period
- relative, absolute

summation
- none

the direction of potential change
- always depolarization and reversal of charges

location
- regions of the membrane with an abundance of voltage-gated channels

28
Q

afferent division of the PNS

A

carries info about the internal or external environment to the CNS

29
Q

Sensory receptors

A

are specialized peripheral endings of afferent neurons

each receptor type (photo, mechano, thermo, chemi, osmo, noci) responds to an adequate stimulus (a change in the energy form or modality to which it is responsive) translating the stimulus energy form into electrical signals

30
Q

stimulus

A

typically brings about a graded, depolarizing receptor potentiald if of sufficient magnitude, ultimately generating action potentials in the affee=rent fiber next to the receptor

these AP self propagate along the afferent nerve fiber to the CNS. The strength of the stimulus determines the frequency of APs generated

31
Q

magnitude of the receptor potential

A

influenced by the extent of receptor adaptation which is a reduction in receptor potential despite sustained stimulation

1 - tonic receptors adapt slowly or not at all and thus provide continuous information about the stimuli they monitor

2 - phasic receptors adapt rapidly and frequently exhibit off responses thereby providing information about changes in the energy form they monitor

32
Q

labeled-line pathways

A

lead from the receptors to the CNS so that the CNS can decipher info about the type and location of stimuli