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Biological Systems > Chapter 34 Nervous System > Flashcards

Chapter 34 Nervous System Flashcards

1
Q

How fast do mammalian neurons transmit signals

A

20-100 metres per second

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2
Q

What does it mean that neurons are excitable?

A

They generate and transmit electrical signals called action potentials

In excitable cells, APs generated at one point propagate over the whole membrane

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3
Q

What is a synapse?

A

cell-to-cell contact point specialized for signal transmission

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4
Q

What are the 4 regions of a neuron?

A

Dendrite
Cell body
Axon
presynaptic axon terminal

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5
Q

What is a nerve?

A

Bundle of axons outiside the brain and spinal cord (In brain and spinal cord they are called tracts)

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6
Q

What are the functions of glial cells?

A
  • Help orient neurons towards target cells during embryonic development
  • Provide metabolic support for neurons
  • Help regulate composition of extracellular fluids and perform immune functions
  • Assist signal transmission across sinapses
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7
Q

What cells produce myelin and where

A

Oligodendrocytes - CNS

Schwann cells - PNS

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8
Q

Define current

A

flow of electrical charges from place to place; in cells it is based on the flow of ions (e.g. Na+)

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9
Q

What is voltage?

A

electrical potential difference
- Present if positive charges are concentrated in one place and negative charges concentrated in a different place

Produces currents because opposite charges attract and move towards each other

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10
Q

What is membrane potential?

A

voltage across a membrane

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11
Q

What is resting potential of a neuron

A
  • 60 to -70 millivolts (mV)

- Negative sign means in side of cell is electrically negative compared to inside

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12
Q

How does ion redistribution occur?

A

through membrane channel proteins and ion transporters
e.g. sodium-potassium pump

Diffusion is controlled by concentration and electrical effect - when they are equal electrochemical equilibrium is reached

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13
Q

How does the sodium potassium pump work?

A

Moves:
3 Na outside of cell
2 K inside cell

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14
Q

What does the nernst equation calculate?

A

equilibrium potential of the ion

Electrochemical equilibrium

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15
Q

Most ion channels are gates. What are the types of gates?

A

Voltage gated - change in membrane potential
Stretch gated - tension applied to cell membrane
Ligand gated - when ligand binds to channel protein

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16
Q

What is depolarization?

A

When membrane becomes less negative inside

- Occurs when Na channels open, Na enters cell

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17
Q

What is hyperpolarization?

A

When charge inside becomes more negative

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18
Q

What types of membrane potential are there?

A

Graded - changes from resting potential that are less than the threshold of -50mV. Only spread a short distance and disperses
All or None - Depolarization to threshold of -50mV creates AP that does not get smaller and propagates along cell membrane

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19
Q

What does it mean for signals to be integrated and what is a key area for this to occur?

A

When graded hagnes are added together to make all or none chagnes

Key area is the axon hillock - where APs are most often generated and where axons leave the nerve body

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20
Q

What is an action potentail?

A

A rapid large change in membrane potential that reverses membrane polarity

21
Q

What are the steps of an action potential forming?

A

1) membrane depolarizes from -65mV to + 40mV
2) MP reaches threshold and voltage gated Na channels open, Na enters cell -> more depolarization -> AP
3) Voltage gated Na channels close, Voltage gated K channels open slowly, K moves out

22
Q

At what point does maximum depolarization occur?

A

when all Na channels are open

23
Q

Why do APs only travel in one direction?

A

Because Na channels have a refractory period wher they cnnot depolarize (or open)

24
Q

What causes APs to travel faster?

A

Myelin and larger diameter axons

25
Q

What are nodes of Ranvier?

A

gaps in myelin -> AP are only generated at nodes and jump from ode to node (Saltatory conduction)

26
Q

What positive feedback mechanism can be seen in the depolarization process?

A

When membrane is partially depolarized (reaches threshold) some Na channels open, more Na diffuses into cel , more Na channels open until all are open and maximum depolarization occurs

27
Q

What is a chemical sinapse?

A

Narrow spce between cells that action potentials cannot cross
- Where neurotransmitters are released

28
Q

How are neurotransmitters removed from the synaptic cleft?

A

Enzymatic breakdown
Uptake by other neuron or glial cells
Reuptake by presynaptic cleft

29
Q

What is an electrical synapse?

A

where cells are joined by gap junctions where cytoplasm is contrinuous so signals cross with essentially no delay

30
Q

What are neuromuscular junctions?

A

Chemical synapse between motor neurons and skeletal muscle cells

31
Q

Describe the process that follows an AP reaching a neuromuscular junction

A
  • AP reaches synapse
  • Voltage gated Ca channels open
  • ACh released via exocytosis diffuses across synatic cleft and binds to postsynaptic cell receptors
  • Receptors allow Na and K to flow through -> Na depolarizing membrane
  • Creates AP if threshold is reached
32
Q

What are the 3 categories of neurotransmitters?

A

Amino Acids - glutamate, glycine and GABA
Biogenic amines - ACh, dopamine, norepiniepherine and serotonin
Variety of peptides (strings of amino acids)

33
Q

What are the 2 major trends in evolution of the nervous system?

A

Centralizaion

Cephalization

34
Q

What makes up the CNS

A

integrating neurons and glial cells

35
Q

What are effectors?

A

cells or tissues that perform actions and carry out orders

36
Q

What are interneurons?

A

neurons confined to the CNS

37
Q

What are efferent neurons?

A

convey signals FROM CNS to muscles or other effectors

38
Q

What does the autonomic nervous system control?

A

effectors other than skeletal muscles

39
Q

What are the 3 divisons of vertebrate ANS

A
  • Enteric division - internal to gut wall
  • Sympathetic - fight or flight
  • Parasympathetic
40
Q

What are the parts of an autonomic efferent pathway?

A
  • Preganglionic neuron with cell body in CNS
  • axons synapse on neuron outside CNS in ganglion (collection of nerve cell bodies) - second neuron is postganglionic (axon leaves ganglion and synapses in the target cell)
41
Q

How are the efferent pathways in the Parasympathetic Nervous system different to Sympathetic Nervous System

A

Parasympathetic - ganglia are near target organs and preganglionic neurons exit CNS at brain and sacral retion

Sympathetic - ganglia are near spinal cord and neurons exit CNS at thoracic and lumbar retions

42
Q

What neurotransmitters are used by sympathetic postganglionic neurons?

A

Norepinepherine

43
Q

What neurotransmitters are used by parasympathetic postganglionic neurons?

A

acetylcholine

44
Q

What is the spinal reflex?

A

afferent information converts to efferent activity without going thought the brain

45
Q

What are the main regions of vertebrate brains?

A

Forebrain
Midbrain
Hindbrain

46
Q

What brain region has changed least through evolution

A

hindbrain

47
Q

What makes up the cerebral cortex?

A

outermost layer of the cerebral hemispheres - many cell bodies

48
Q

What is a technique that helps pinpoint brain activity

A

fMRI (functional magnetic resonance imaging)

PET

49
Q

What is the amygdala?

A

Responsible for emotions, survival instincts and memory

Rage centre

Biological Systems (20 decks)

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