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Physiology > Lecture 11 Neurons and Neural signals > Flashcards

Lecture 11 Neurons and Neural signals Flashcards

1
Q

Functions of the Nervous system

A

sensation
communication
integration
control

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2
Q

Neurons

A

functional cells of the nervous system
excitable cells- generate electrical signals (changes in membrane potentials)
communicate information in the form of electrical and chemical signals

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3
Q

Cell body of a neuron

A

contains the nucleus and most organelles

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4
Q

dendrites

A

branch from the cell body

receive signals from other cells through synapse

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5
Q

axon

A

extends from the cell body, conducts action potentials

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6
Q

axon hillock

A

region where axon joins the cell body

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7
Q

Trigger zone

A

initial segment adjacent to the axon hillock is the trigger zone for AP

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8
Q

axon terminals

A

contain vesicles with neurotransmitter, form synapses with other cells

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9
Q

Central Nervous system

A

brain and spinal cord

where most neurons are located

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10
Q

Peripheral Nervous System

A

Nerves, ganglia and sensory receptors
Afferent Division
Efferent Division

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11
Q

Afferent Division

A

Sensory neurons, input to CNS from sensory receptors
somatic sensory- from skin, muscles, bones & joints
Visceral sensory- from internal organs
Special senses- vision, hearing, equilibrium, olfaction, taste

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12
Q

Efferent Division

A

Motor neurons, output from CNS to effectors
Somatic Motor- to skeletal muscles (voluntary)
Autonomic (ANS) - to heart, smooth muscle, gland, adipose tissue (involuntary)
a.sympathetic
b. parasympathetic

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13
Q

Enteric Nervous System

A

Nerve network of the GI tract

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14
Q

Functional Types of Neurons

A

Sensory neurons
Motor neurons
Interneurons

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15
Q

Sensory Neurons

A

afferent
Input to CNS from sensory receptors; dendrites located at receptors, axon in nerves, cell bodies in ganglia outside the CNS

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16
Q

Motor Neurons

A

efferent
Output from CNS to effectors
cells bodies and dendrites located in the CNS, axons in nerves

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17
Q

Interneurons

A

communicate and integrate information within the CNS
located entirely within the CNS
Most common

18
Q

Astrocytes

A

CNS

structural and chemical support, blood-brain barrier

19
Q

Oligodendrocytes

A

CNS

Myelin in CNS

20
Q

Microglia

A

CNS

Phagocytes

21
Q

Ependymal cells

A

CNS

produce CSF

22
Q

Schwann cell

A

myelin in PNS

23
Q

satellite cells

A

in PNS ganglia

24
Q

Graded Potentials

A

small, localized changes in membrane potential
formed at the cell body and dendrites
can be depolarization or hyperpolarization
spread passively and weaken with distance
size depends on stimulus strength
seen at cell bodies and sensory receptors
Stimulates action potentials
caused by opening of chemically gated channels
must exceed threshold to start AP

25
Q

Action Potentials (nerve impulses)

A

large change in membrane potential
formed along the axon
rapid depolarization followed by repolarization
actively conducted along the axon
all or none- size is not dependent on stimulus strength
Doesn’t weaken with distance

26
Q

Phase 1 of action potentials

A

Rising (Depolarization) phase

  • initial depolarization stimulus must be above threshold to form an AP
  • voltage gated Na+ channels open
  • activation gate opens in response to initial depolarization
  • > rapid Na+ inflow -> rapid depolarization
27
Q

Phase 2 of action potentials

A 
Falling (repolarization) Phase 
-Voltage gated Na+ channels close 
  inactivation gate - closes when depolarization reaches peak 
-voltage gated K+ channels open 
->rapid K+ outflow-> repolarization
28
Q

Phase 3 of action potentials

A

Undershoot
voltage gated K+ channels remain open, high K+ permeability results in hyperpolarization
resting states of channels and resting potential restored at end of undershoot phase
-both voltage gates closed only the leak channels open when RP is restored

29
Q

Name the properties of action potentials

A

threshold
all or more
regenerative
refractory period

30
Q

Threshold

A

stimulus must be greater than a certain strength to evoke an AP
(subthreshold - cant start AP below threshold)
enough activation gates must open
-55mV

31
Q

“All or None”

A

once threshold is reached size of the AP is constant regardless of stimulus

32
Q

regenerative

A

AP is regenerated and does not decrease in strength along the axon

33
Q

Refractory period

A

short delay following an AP before another AP can be formed

34
Q

absolute refractory period

A

ARP

period in which another AP can not be formed

35
Q

relative refractory period

A

RRP

period in which a larger stimulus is required to form another AP

36
Q

Main importance of refractory period

A

ARP sets an upper limit on frequency of AP
During RRP, a stronger stimulus can result in increased frequency of APs
-stimulus intensity is coded by the frequency of APs
Refractory period prevents AP from traveling backward along the axon

37
Q

Are concentration gradients affected during an AP

A

No they are not, Na+/K+ pump still maintains gradients

38
Q

How are stimulus intensity coded

A

by the frequency of AP

39
Q

Unmyelinated Axons

A

AP depolarization spreads a short distance down the axon
depolarization stimulates formation of AP farther down the axon
axons are leaky to Na+ and K+; need to regenerate AP often along the axon -> slow conduction speed
increasing axon diameter increases conduction speed

40
Q

Myelinated Axons

A

myelin sheath formed by membrane of schwann cells in PNS and oligodendrocytes in CNS
insulates axon, reduced leakage of Na+ and K+
nodes of ranvier- gaps in myelin sheath are sites of AP regeneration
AP “jumps” from node to node (saltatory conduction)
faster conduction speeds (up to 120 m/s)

Physiology (33 decks)

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