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Biology 30S > Nervous System > Flashcards

Nervous System Flashcards

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1
Q

What are the functions of the nervous system, and why?

A
  • senses and responds to changes and regulates body‘s structures and processes to maintain homeostasis
  • monitors and controls automatic functions, voluntary actions, learning, thoughts, etc.
  • Because the body can only survive within a narrow range of conditions
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2
Q

What structures is the nervous system composed of?

A
  • Composed of brain, spinal cord, and nerves connecting to other body parts and systems
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3
Q

How many nerve cells does the brain have?

A
  • over 100 billion nerve cells
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4
Q

How many connections can each nerve have the other nerves?

A
  • they can have 10,000 connections to other nerves
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5
Q

How is the nervous system organized into? Aka what two parts of system

A

Central nervous system (CNS)

Peripheral Nervous system (PNS)

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6
Q

What does the central nervous system contain, and what does it do?

A
  • Brain and spinal cord

- Integrates and processes information from nerves

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7
Q

What does the peripheral nervous system contain, and what does it do?

A
  • contains nerves that carry sensory messages to the CNS and send information from CNS to muscles and glands
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8
Q

What two systems does the peripheral nervous system contain?

A

Somatic and autonomic systems

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9
Q

What is the somatic system of PNS?

A
  • Sensory receptors in head and extremities
  • nerves carrying sensory information to CNS
  • nerves carrying instructions from CNS to skeletal muscles
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10
Q

What is the autonomic system of PNS?

A
  • Controls glandular secretions and functioning of smooth and cardiac muscles
  • sympathetic and parasympathetic divisions work in opposition to each other to regulate involuntary processes of body
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11
Q

What are neurons and what do they do? (3)

A
  • specialized to respond to physical and chemical stimuli
  • conduct electrochemical signals
  • release regulating chemicals
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12
Q

What are glial cells and what do they do?

A
  • support neurons

- nourish, remove wastes, defend against infection, supporting framework for nervous tissue

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13
Q

What are neurons organized into?

A

Nerves

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14
Q

What are nerves?

A

Bundles of neurons with protective connective tissue

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15
Q

What are the three types of neurons?

A

Sensory neurons, interneurons, and motorneurons

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16
Q

What are sensory neurons?

A

Gather information from sensory receptors (sensory input) and transmit impulses to CNS

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17
Q

What are interneurons and what do they do? (3)

A
  • found entirely within the CNS
  • act as a link between sensory and motor neurons (integration)
  • process and integrate sensory information and relay motor information
    Note: collect info from sensory neurons, process it, and send to motorneurons)
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18
Q

What are the motor neurons?

A
  • transmit information (motor output) from CNS to effectors (muscles, glands, etc)
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19
Q

What does the reflex arc do?

A
  • Allows for rapid reaction to danger before being consciously aware of the threat
    Ex. Pulling hand away from hot object
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20
Q

When does the brain process what has happened after a reaction to danger?

A

The brain processes what has happened only after the reflex arc has occurred

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21
Q

How does the simple connection of the three neurons help in the reflex arc?

A
  1. Sensory neurons senses stimulus (ex. Pain on finger)
  2. Interneuronneuron processes information in spinal cord
  3. Motor neuron instructs muscles to contract and withdraw hand
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22
Q

What components make up the structure of a neuron? (4)

A

dendrites, cell body (soma), axon, branching ends

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23
Q

What are dendrites?

A
  • short branching terminals that receive nerve impulses from other neurons or sensory receptors, relaying them to the cell body
    -numerous, highly branched
    Note: they receive info, not send out
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24
Q

What is the cell body (soma) of a neuron?

A
  • Location of nucleus, metabolic reactions
  • processes input from dendrites, possibly relays message to axon
    Note: Neurons either send a yes or no message (1 per each neuron)
25
Q

What is the axon of a neuron?

A
  • conducts impulses away from the cell body

- SOME enclosed in fatty, insulated myelin sheath layer (myelinated vs. Unmyelinated)

26
Q

What are the branching ends of a neuron?

A
  • ends of axon release chemical signals to space between them and dendrites of neighbouring cells
27
Q

What is the Myelin sheath and where does it come from?

A
  • protects myelinated neuron, speeds rate of nerve impulse transmission
  • Comes from Schwann cells
28
Q

What is a Schwann cell?

A
  • type of glial cell forms myelin by wrapping itself around axon
29
Q

What do myelinated and unmyelinated neurons look like in CNS?

A
  • myelinated neurons form white matter and have a glistening appearance
  • Unmyelinated neurons form gray matter
30
Q

Are neurons in the PNS myelinated or unmyelinated?

A

Most are myelinated

31
Q

What does an inactive or resting neuron have?

A

An electrical potential difference or voltage across the neural membrane

32
Q

Why is it called membrane potential?

A
  • cytoplasmic side of membrane is negative relative to extracellular side of resting neuron
  • therefore this charge separation is a form of potential energy
33
Q

What is the resting membrane potential value in a resting neuron?

A

It is -70mV typically

34
Q

What is the function of the resting membrane potential in a resting neuron?

A
  • provide energy for nerve impulse if appropriate stimulus

- keeps neuron constantly ready for impulse to occur

35
Q

How is resting membrane potential generated?

A

Through a process called polarization, also known as separation of charge

36
Q

Why is a resting neuron polarized? In other words, what are the polarization mechanisms?

A
  1. Large, negatively-charged proteins present inside the cell but not outside and cannot pass membrane
  2. membrane impermeable to some smaller negative ions like chloride inside cell
  3. Most important is the sodium-potassium exchange pump
    - K+ diffuses out of cell faster down it’s concentration gradient than Na+ diffuses back into cell to maintain constant transmembrane potential of -70mV
37
Q

How does the sodium-potassium pump work?

A
  • Uses ATP to transport three sodium ions out of cell for every two potassium ions into cell
  • excess of positive charge outside cell
38
Q

What is a nerve impulse made up of?

A
  • made up of a series of action potentials, each on one segment of axon membrane
39
Q

When is the axon membrane depolarized?

A
  • whenever transmembrane potential is reduced to less than -70 mV (closer to zero than -70mV)
40
Q

What is the threshold potential?

A
  • if the transmembrane potential is reduced to -55mV, action potential occurs
41
Q

Why is action potential an “all or none” event?

A
  • depolarization between -70 mV and -55 mV has no effect

- Depolarization from -55 mV to 0 produces same affect

42
Q

What happens in an action potential in an unmyelinated neuron? (8)

A
  1. Voltage-gated sodium channels in membrane open
  2. Na+ ions rush into axon due to CG and potential difference
  3. In a millisecond or less, potential difference across membrane in tiny section becomes +35mV
  4. Change in potential (-70mV to +35) causes sodium channels to close and voltage-gated potassium channels to open
  5. K+ ions flow out of cell and cause membrane to repolarize to about -90mV (Hyperpolarization)
  6. potassium channels close
  7. Sodium-potassium exchange pump and diffusion bring transmembrane potential quickly back to -70mV
  8. For a few milliseconds after action potential, no new action potential can be carried out due to refractory period (recovery time)
43
Q

Where can action potentials only occur in myelinated neurons?

A
  • action potentials can only occur in gaps of myelin sheath called nodes of Ranvier
44
Q

How does action potential work in myelinated neurons?

A
  1. Sodium ions that rush into one node diffuse in both directions along the axon and depolarize the next node to threshold
  2. The previous node is in a refractory state, so only the next node undergoes an action potential so nerve impulse moves in one direction
  3. Action potentials‘s jump from node to node (nerve impulse) until it reaches the end of the neuron
45
Q

What does action potentials jumping from one node of Ranvier to the other constitute? Benefits of it?

A
  • it constitutes a “saltatory conduction”

- it is much faster (120 m/s) than the many side by side action potentials of an unmyelinated axon (0.5 m/s)

46
Q

What is multiple sclerosis, and what happens in the body?

A
  • autoimmune disorder where body’s immune system breaks down Myelin
  • Neurons cannot properly carry electrochemical signals
  • Blurred vision, loss of balance, muscle weakness, fatigue, slurred speech
47
Q

What is a synapse?

A
  • connections between two neurons or a neuron and an effector (muscle or gland)
48
Q

What is a neuromuscular junction?

A
  • Synapse between motor neuron and muscle cell
49
Q

What is the synaptic terminal or synaptic knob?

A
  • end of the branching end of a neuron

- after the impulse travels down the length of an axon, it reaches the far end called this

50
Q

What is the synaptic cleft?

A
  • Gap between two neurons
51
Q

What are neurotransmitters?

A
  • Chemical messengers that carry neural signal across synapse from presynaptic neuron to postsynaptic neuron or effector
52
Q

What happens along the way of the presynaptic and postsynaptic neuron?

A
  1. At the synaptic terminal, The impulse causes sacks of neurotransmitters (synaptic vesicles) to fuse with membrane of axon
  2. When they do so, they release neurotransmitters into synaptic cleft by exocytosis when they diffuse across synapse to dendrites of postsynaptic nerve or effector
  3. The neurotransmitter binds to receptors proteins in postsynaptic membrane
  4. This causes ion-specific channels to open (sodium channels)
  5. This depolarizes the postsynaptic membrane, and action potential is initiated if threshold potential
  6. Enzymes will break down neurotransmitters after the effect to inactivate them and the fragments are taken back into presynaptic membrane
53
Q

What are the two types of effects that the neurotransmitters can I have on the postsynaptic membrane? This is an integration question

A

Excitatory effect and inhibitory effect

54
Q

What is the excitatory effect of neurotransmitters on the postsynaptic membrane?

A
  • causes positive ions like sodium to flow into postsynaptic neuron
  • slightly depolarizes the is the membrane (to threshold)
55
Q

What is the inhibitory effect of neurotransmitters on the postsynaptic membrane?

A
  • causes potassium channels to open and allow potassium ions to flow out of cell
  • more negative transmembrane potential called hyperpolarization
56
Q

What is integration, and how does it happen in regards to neurotransmitters having an effect on the postsynaptic membrane?

A
  • to integrate is to combine
  • The cell body receives many signals and must integrate all of them to read the combined effective neurotransmitters
  • if excitatory stimuli is strong enough, the depolarization reaches the axon, generating a nerve impulse
57
Q

What is acetylcholine? What does it do?

A
  • neurotransmitter that crosses a neuromuscular junction

- excites muscle cell membrane, causing depolarization and contraction of muscle fiber

58
Q

What is cholinesterase?

A
  • fast-acting enzyme released to synapse
  • breaks down acetylcholine from protein receptors, allowing ion channels to close and membrane to repolarize
  • without cholinesterase, the muscle would remain contracted
59
Q

What is sarin?

A
  • nerve gas that blocks the release of cholinesterase
  • Constant contraction and paralysis
  • more than 50 substances in body act as neurotransmitters (needed to put that somewhere lol)

Biology 30S (14 decks)

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