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BIOL 110 > Chapter 12 - Nervous Tissue > Flashcards

Chapter 12 - Nervous Tissue Flashcards

1
Q

neurons

A

functional unit of the nervous system (transmits info)

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2
Q

neuroglia

A

cells that support and maintain neuronal function

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3
Q

structural classification of neurons is based on…

A

the number of processes (axons or dendrites) extending from the cell body
-unipolar, bipolar, or multipolar neurons

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4
Q

describe sensory or afferent neurons

A
  • Convey AP into the CNS (central nervous system)

- Occurs through cranial or spinal nerves

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5
Q

describe motor or efferent neurons

A
  • Convey AP from CNS to the periphy

- Cause muscles to do something

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6
Q

describe interneurons

A

-Mainly located in CNS between sensory and motor neurons

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7
Q

what are the two types of electrical signals that neutrons use?

A 
1.Graded potentials   
Short distance communication
Only within dendrites and cell body – doesn’t travel down axon
Determine if AP will ocurr
2.Action potentials 
Allow for communication 
over long distances
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8
Q

what is Resting Membrane Potential (RMP)?

A
  • ion channels open or close in response to specific stimui
  • More positive charge outside the cell = RMP
  • The RMP is negative (-70mV)
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9
Q

Explain the process of maintaining a -70 mV RMP.

A
  • Na+/K+ ATPase pumps out 3 Na+ for every 2 K+ pumped in (net increase of + charge outside cell)
  • Leakage channels randomly opened or closed
  • More K+ leaks out than Na+ leaks in
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10
Q

explain electrochemical gradiets

A
  • when ion channels are open, specific ions can cross PM down the electrochemical gradient.
  • Cations (positive charge) move towards a negatively charged area; Anions (negative charge) move towards a positively charged area
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11
Q

what are the 3 types of gated channels?

A
  1. ligand-gated
  2. voltage gated
  3. mechanically gated
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12
Q

explain ligand-gated channels.

A
  • respond to a neurotransmitter

- concentrated near synapses, dendrites and cell body of sensory neurons

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13
Q

explain voltage gated channels.

A

Channels respond to changes in membrane

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14
Q

explain mechanically gated channels

A

respond to a mechanical or physical deformation

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15
Q

what is a polarized cell?

A

a cell that exhibits a resting membrane potential

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16
Q

polarized cells have the ability to produce what kind of potential. Explain.

A
  • graded potential
  • Open an ion channel, changes the membrane potential
  • Spreads for a short distance
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17
Q

depolarizing graded potential

A

Stimulus causes the cell to be less negatively charged

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18
Q

hyperpolarizing graded potential

A

Stimulus causes cell to be more negatively charged

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19
Q

When does an action potential occur

A

if the Axon Hillock reaches -55 mV (threshold)

20
Q

where do graded potentials occur?

A

dendrites and cell body, do not travel down the axon

21
Q

how do graded potentials differ from action potentials?

A
  • travel short distances

- can be added together to create a smaller or larger graded potential

22
Q

define action potential

A
  • a signal which travels the length of the neuron
  • If neuron reaches a threshold potential, an AP is produces and spreads down to axon terminals
  • If stimulus is not strong enough = no AP
23
Q

what are the 2 phases of an action potential?

A
  1. depolarizing phase

2. repolarizing phase

24
Q

what occurs when a graded potential reaches its threshold (-55 mV)

A
  1. Voltage-gated Na+ channels open
    - Na+ rushes into cell inside becomes more positive
    - Membrane potential reaches +30 MV
  2. During the repolarization phase, K+ channels open and K+ rushes outward.
  3. The cell returns to a more negative state
25
Q

in action potentials what causes after-hyperpolarization to occur? explain.

A
  1. open voltage gated channels let too much k+ flow out of the cell
  2. membrane potential becomes even more negative (~-90 mV)
  3. Voltage gates K+ channels close, membrane potential returns to resting
26
Q

explain the all or none principle for AP

A
  • if a stimulus reaches threshold, the action potential is always the same.
  • a stronger stimulus will not cause a larger AP
  • If you need a stronger reaction, send more AP’s
27
Q

what is the absolute refractory period? explain.

A
  • cell cannot generate another AP, no matter how strong the stimulus.
  • Period that coincides with the period of Na+ channel activation and inactivation
  • Na+ channels must return to resting state before next AP can occur
28
Q

what is the relative refractory period? explain.

A
  • period of time during which a second action potential can be initiated, but only by a larger-than-normal stimulus.
  • When K+ channels are still open, but Na+ channels are resting = hyperpolarizing phase
29
Q

where does propagation of an AP begin?

A

axon hillock

30
Q

how does propagation of an action potential proceed?

A
  1. continuous conduction - unmyelinated axons

2. saltatory conduction - myelinated axons

31
Q

what is the purpose for a myelinated axon?

A

insulation, increases speed of nerve impulse

32
Q

what are nodes of ranvier? (neurofibril nodes)

A

areas of axon without myelin

33
Q

explain signal transmission at the synapse

A

1.one-way transfer from a presynaptic neuron to a postsynaptic neuron.
2.AP reaches axon terminals, voltage gated Ca2+ channels open
3.Ca2+ flows in triggering
the release of Neurotransmitters into synaptic cleft.
4.neurotransmitters cross cleft and bind to ligand-gated receptors on postsynaptic membrane

34
Q

what mades the intensity of graded potentials increase?

A

increased number of neurotransmitters released to bind to postsynaptic membrane will increase graded potential in post synaptic cell

35
Q

explain the process of neurotransmitter removal.

A

Removal is accomplished by:

  • Diffusion out of the synaptic cleft
  • Loss through enzymatic degradation
  • Re-uptake by the cells
36
Q

neurological regeneration is dependent upon what?

A

neurilemmocytes

37
Q

where does neurological regeneration occur? and where does it not?

A

occurs in the Peripheral Nervous System (in neurilemmocytes) but does not occur in the central nervous system.

38
Q

In the CNS what occurs if nerve cells become damaged?

A

astrocytes form scar tissue.

39
Q

Describe the process of Neuronal Regeneration.

A

1) Axon is Injured
2) neurolemma forms regeneration tube
3) axon regenerates and re-mylenation occurs
4) Innervation to effector is restored

40
Q

What are the 2 main divisions of the nervous system.

A

Central Nervous system
- brain and spinal cord
Peripheral Nervous System
-nervous tissue outside the CNS (nerves and ganglia)

41
Q

Where do most stimuluses for muscle contraction and gland secretion begin?

A

central nervous system

42
Q

what are the divisions of the PNS?

A

1) Somatic Nervous System (SNS)
2) Autonomic Nervous System (ANS)
3) Enteric Nervous System (ENS)

43
Q

What are the components of the Somatic nervous system?

A

1) Somatic sensory neurons (afferent)
- to CNS
2) Somatic motor neurons (efferent)
- Away from CNS to skeletal muscle
3) Interneurons
- between afferent and efferent neurons

44
Q

What are the components of the autonomic nervous system?

A

1) Sensory Neurons
- info from sensory receptors in visceral organs (heart, lungs) to CNS
2) Motor Neurons (involuntary)
- impulses from CNS to smooth muscle, cardiac muscle, and glands

45
Q

name the 2 divisions of the autonomic nervous system

A

1) Sympathetic (fight or flight)

2) Parasympathetic (rest and digest)

46
Q

The Enteric Nervous system (ENS) is often referred to as the …..

A

brain of the gut

47
Q

what are the responsibilities of the ENS?

A
  • involuntarily controls the GI propulsion

- acid and hormonal secretions

BIOL 110 (17 decks)

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