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HSF > compendium 8 > Flashcards

compendium 8 Flashcards

1
Q

Functions of the nervous system

A
  1. Maintaining homeostasis
  2. Receives sensory input
    - Internal- works at subconscious level, such as digestion, beginning chemical and mechanical digestion
    - External- external inputs, such as touching hot stove or hearing a sound, conscious level
  3. Integrating information
  4. Motor output- actions that come about from muscles and glands
  5. Establish and maintain mental activity- thinking, memory, consciousness…
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2
Q

Structural divisions of the nervous system

A
  1. Central nervous system (CNS)
    - Brain and spinal cord
  2. Peripheral nervous system (PNS)
    - Spinal nerves and cranial nerves
    - Spinal nerves used for communication between body and spinal cord and hence a way of communicating with the CNS, 31 pairs
    - Cranial nerves, relating to neck and head, information passed between brain and body, 12 pairs
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3
Q

Neuron (nerve cell):

A

basic structural unit of the nervous system

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4
Q

Axon:

A

nerve fiber

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5
Q

Nerve:

A

bundle of axons (or nerve fibers) and their sheaths (outer covering)

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6
Q

Sensory receptors:

A

separate specialised cells which detect temperature, pain, touch, pressure, light, sound, odour and other stimuli

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7
Q

Action potential:

A

electrical signal, how messages are transmitted (down length of axon)

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8
Q

Effector organ or effector cell:

A

the organ, tissue or cell in which an effect or an action takes place

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9
Q

Ganglion:

A

collection of cell bodies located outside the CNS

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10
Q

Plexus:

A

extensive network of axons or cell bodies

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11
Q

Synapse:

A

junction of a neuron with another cell e.g. end of a neuron with a muscle cell or another neuron

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12
Q

Autonomic subdivision (controls cardiac and smooth muscles)

A
  • Involuntary and under subconscious control
  • Action potentials in the motor neurons travel from the CNS to smooth or cardiac muscle, or glands
  • Two-neuron system
  • Cell bodies of the neurons are located in the CNS and autonomic ganglion
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13
Q

Somatic subdivision (skeletal muscles)

A
  • Voluntary and under conscious control
  • Action potentials in the motor neurons travel from the CNS to skeletal muscles
  • Single neuron system
  • Cell bodies are located in the CNS
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14
Q

Enteric division

A
  • Found in digestive tract and controls and monitors digestive tracts actions, is integrated with autonomic
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15
Q

Motor vs. sensory pathways

A

the sensory neurons transmit information to the CNS via sensory receptors and that sensory neuron is travelling via the dorsal root. Then motor neurons transmit information from the CNS to your effector cells which travels via ventral root.

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16
Q

Bushwalking example

A

Somatic nervous system:
- Sensory information coming into the somatic nervous system in your bushwalking example is that; eye see snake, feet fell it through shoes, hear noise – this sensory information is sent to CNS where it is integrated and processed then comes back as motor output such as screaming and running away
Autonomic nervous system
- Sensory information coming into the ANS will be the same as info incoming into SNS – this sensory info is then directed and sent towards the CNS where it is integrated and processed and then comes away from CNS as motor output such as cardiac muscles in heart contract faster increasing heart rate, cardiac muscle beats harder so stroke volume increases, and blood vessels containing smooth muscles dilate sending blood to muscles, sweat glands produce sweat

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17
Q

Sympathetic vs. parasympathetic

A

Sympathetic – fight or flight, HR, sweating..
Parasympathetic – rest and digesting functions such as saliva production, digestion of food, urination..
- They work to complement each other

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18
Q
  1. Why do we need a nervous system, what is its function?
A 
It is the major control system in your body and functions are to 
-	Maintaining homeostasis
-	Receives sensory input
	Internal
	External
-	Integrating information
-	Motor output- actions that come about from muscles and glands
-	Establish and maintain mental activity
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19
Q
  1. What is the difference between the CNS and PNS?
A 
Structurally:
Central nervous system (CNS) 
-	Brain and spinal cord 
Peripheral nervous system (PNS)
-	Spinal nerves and cranial nerves
Functionally:
CNS:
-	responsible for integrating sensory information and responding accordingly
PNS: 
-	Transmits incoming information to the CNS, CNS will then process this info and integrate it and then send the output action back out by the PNS
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20
Q
  1. What are the different roles of the somatic, autonomic and enteric nervous system divisions?
A

Each of these subdivisions have a sensory arm and transmits incoming and a motor arm which transmits outgoing information
Peripheral NS:
Autonomic NS
- Involuntary and under subconscious control with effector be smooth tissue: cardiac muscle or glands
- Is a 2 neuron system and its cell bodies are located in the CNS and the autonomic ganglia
Somatic NS
- Voluntary and under conscious control, its action potentials travel from the CNS to skeletal muscle (voluntary) is a single neuron system and its cell bodies are located in the CNS
Enteric NS
- Pertains to the control of the gastrointestinal system
Autonomic NS:
Sympathetic – FOF, active during physical activity and actions that require quick response, e.g. increase HR and blood pressure, secretion of sweat form sweat glands, constriction of blood vessels, dilation of pupils,
Parasympathetic – RAD, regulates resting and digesting functions, release of saliva from salivary glands, digestion of food in the stomach, urination

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21
Q
  1. What are the differences between sensory, motor and interneurons?
A

Sensory
- Afferent
- Senses incoming information and sends the action potential or signals towards the CNS
- This neuron travels form the sensory receptor by the dorsal root of the spinal cord
Motor
- Efferent
- Sends action potentials from the CNS to the effector cell or organ which could be muscle or glands
- This neuron travels from the CNS via the ventral route, or the most anterior route here of the spinal nerve to its effector organ, tissue or glands
Interneuron
- Conducts electrical impulses or action potentials form one neuron to the other

22
Q

Cells of the nervous system

A

Neuron

Neuroglia

23
Q

neuron

A

basic structural unit of the nervous system

24
Q

Types of neurons

A 
Functional classification
-	Sensory 
-	Motor
-	Interneuron 
Structural classification
-	Multipolar
-	Bipolar
-	unipolar
25
Q

Multipolar

A
  • has many dendrites, and a single axon, most neurons in the central nervous system are multipolar
  • motor neurons
26
Q

Bipolar neuron

A
  • has two processes, has axon coming off one end of cell body and then on the other end you have your dendrites
  • rare
  • only found in special sense organs such as nose and eyes
27
Q

Unipolar

A
  • also known as pseudounipolar neuron and have one single process which is the axon coming from the cell body
  • sensory receptors pick up the information
28
Q

Neuroglia

A 
CNS
-	Astrocytes
-	Ependymal cells
-	Microglia
-	Oligodendrocytes
PNS
-	Schwann cells
-	Satellite cells
29
Q

Astrocyte cells

A
  • Most abundant of the neuroglial cells in CNS
  • Role 1. Forming a supporting framework for blood vessels and neurons, allow communication between then
  • Role 2. Assists in the formation of tight junctions between endothelial cells of the capillaries, these endothelial cells (simple squamous) of the capillaries form the blood-brain barrier and astrocytes aid to make sure the junction between the capillary endothelial cells remains tight to stop any unwanted substances passing into the brain and the spinal cord from the blood – forming that blood brain barrier
  • Named this because of star shape (astronomy)
  • Respond to tissue damage in the CNS by creating a barrier around the damaged tissue – so that tissue can heal quicker and limit any spread of inflammation to surrounding healthy tissue and astrocytes also limit the regeneration of axons to injured neurons
30
Q

Ependymal cells

A
  • Line the central cavities of the brain and spinal cord
  • Can be squamous, cuboidal or columnar and can be ciliated
  • Ependymal cells form the epithelial lining of these cavities (CSF) and the cilia on these cells assist in the movement of CSF through these cavities
31
Q

Microglial cells

A
  • Microglia is plural
  • Monitor the health of surrounding neurons in CNS using their extensions which branch out and touch the surrounding neurons to see how they’re going
  • Can become phagocytic if detects something unwanted. Phagocytose microorganisms, infection, trauma or inflammation
32
Q

Oligodendrocytes

A
  • Cover axons which forms an insulating sheath around them -> myelin sheath
  • Reworded: Form an insulating covering around them called myelin sheath
33
Q

Schwann cells

A
  • Also called neurolemmocytes

- Form an myelin sheath around axons -> insulating and faster conduction of action potential

34
Q

Satellite cell

A
  • Provide support and nutrition to cell bodies in ganglia
  • Protect cell bodies from harmful substances such as lead and mercury
  • Look like satellites
35
Q

Myelinated and unmyelinated axons

A

Myelinated axons
- Interruptions approximately 2-3 micrometres long called Nodes of Ranvier
Unmyelinated axon
- May have one schwann cell or one oligodendrocyte cell covering more than one axon

36
Q

Electrical signals

A
  • Action potentials
  • Membrane potential
  • Characteristics of the cell membrane which allow a membrane potential to be generated:
    1. Differences in ionic concentration (particularly for Na+ and K+) across the cell membrane
    2. Permeability of the cell membrane to ions
37
Q

Membrane ion channels

A

Non-gated ion channels
- Also known as ‘leak’ ion channels- always open but Each leak channel is specific to a particular ion (potassium channel, sodium channel…)
- Ion specific
- Cell membrane has more K+ leak ion channels compared to Na+ leak ion channels
Gated ion channels – require signals to open them
1) Ligand-gated ion channel (chemically gated ion channel) because these channels open when a ligand or a chemical binds to them. his chemical could be something like a hormone.
2) Voltage-gated ion channel these channels open their gates in responses to change in membrane potential, or the change in electrical charge across the cell membrane
3) Other-gated ion channel these ion channels open to stimuli such as touching, or change in temperature, or a change in pressure.

38
Q

Establishing resting membrane potential

A

Resting membrane potential – the difference in charge across the cell membrane in a resting cell due to the uneven distribution of ions across the cell
Intracellular side is more negative compared to extracellular, ‘more’ because it doesn’t mean that the intracellular side is negative and extra is positive, It means that the intracellular side is MORE negative

  • RMP of neurons = - 70 mV where the negative sign indicates the charge on the intracellular side of the cell. Can be minus 40 and minus 90 millivolts for other types of cells.
    Now that minus, or negative sign, indicates a charge on the intracellular side of the cell
    ions which are responsible for creating a negative resting membrane potential are
    mostly potassium ions and sodium ions to a lesser degree because cell membrane contains a larger number of K+ ion channels and potassium ions which are naturally abundant on the intracellular side of a cell, they would leak from the intracellular side to the extracellular side. And they do this by moving down their concentration gradient.
    Now when they do this, this leaves the accumulation of a more positively charged potassium ion on the extracellular side, thus a more positively charge extracellular side compared to the intracellular side. Making intracellular more negative and hence -70 millivolt charge. Sodium ions which are more abundant in extracellular will leak into intracelly by sodium ion channels and because theres fewer channels available it doesn’t make much of a difference to the resting membrane potential

RMP caused by leak ion channels and the Na+/K+ pump

  • Requires ATP
  • Sends out 3 sodium ion and bringing in 2 potassium ions, contributes to RMB by maintaining concentration of Na+ and K+ by actively moving them against their concentration gradient
39
Q

Changing the resting membrane potential

A

Depolarisation – when the membrane potential becomes more positive i.e. the inside of the cell becomes more positive. E.g. - 70 mV -> - 30 mV

Hyperpolarisation – when the membrane potential becomes more negative i.e. the inside of the cell becomes more negative. E.g. - 70 mV -> - 75 mV

Repolarisation – membrane potential returns to normal

40
Q

Graded potential

A
  • Graded potentials can lead to action potentials
  • Graded potential are short-lived, localised changes in membrane potential
  • Often occur in dendrites or the cell body of a neuron
  • Ability to summate (ability to change form small to large, so one change causes more of same change such as more channels opening)
  • Decremental - Not able to transfer information over long distances, reason for being the start of an action potential because action potential can spread across the distance of neuron whereas graded potential cannot.
41
Q

Action potential

A
  • Afterpotential – short period of hyperpolarisation of an action potential
  • Action potential takes a few milliseconds
  • Action potential is not decremental

When the graded potential summates (effect produced by one gradient potential’s is added onto the next) and the membrane potential reaches a threshold (-55 mV needed) so when graded potential summates an action potential will definitely take place and this summation of graded potential to action potential takes place in the trigger zone of neurons which contain a greater number of voltage gated channels
So action potential first goes into depolarisation and you can see by graph membrane potential becomes more positive here so the inside become more positive, then repolarisation where inside becomes more negative again then hyperpolarisation called after potential.

42
Q

propogation

A

Resting membrane potential:

  • All gated Na+ and K+ channels are closed.
  • K + leak channels (not visible on this image) are open which allow movement of K+ to the outside of the cell. This creates a negative intracellular charge = RMP.
  • Na+ /K+ pump (not visible on this image) also creates the RMP.Depolarisation:
  • Na+ gated channels open and Na+ moves into the cell and inside of the cell becomes more positive.
  • K + gated channels are closed.
  • Membrane potential becomes more positive.Repolarisation:
  • Na+ gated channels close.
  • K + gated channels open and K+ moves out of the cell and the intracellular side becomes more negative.
  • Membrane potential becomes more negative.End of repolarisation, and the afterpotential: hyperpolarisation
  • Na+ gated channels close.
  • K + gated channels close as well but they close slowly so K+ continues to leave the cell and this produces the afterpotential.
  • Membrane potential becomes very negative. Resting membrane potential:
  • Na+ gated channels are closed.
  • K + gated channels are closed.
  • Resting membrane potential is re-established by Na+/K+ pump (an active process as it is against their concentration gradients) which redistribute ions as all Na+ and K+ gated channels are closed.
43
Q

Synapse

A

Synapse: junction of a neuron with another cell e.g. end of a neuron with a muscle cell or another neuron
Pre-synaptic
Synapse
Post-synaptic

Electrical synapses - current
Chemical synapses - chemicals e.g. hormones, neurotransmitters

44
Q

the chemical synapse

A

Action potential arrives at the presynaptic terminal, This causes voltage gated calcium ion channels to open, so these channels only open when there’s a change in voltage and that change in voltage comes by the action potential. So these channels open allowing calcium to flood in to that presynaptic terminal and they move in moving down their concentration gradient. Calcium ions cause these synaptic vesicles to move closer to the presynaptic membrane and then these vesicle fuse with the membrane and release content (neurotransmitters) into the synaptic cleft (space between the 2 membranes). Neurotransmitters then diffuse across the cleft and bind to the ligand gated sodium ion channels, causing them to open allowing sodium ions to move into the cell. Action potential is generated such as muscle contraction if a muscle was the effector.

45
Q

Neurotransmitter removal

A
  • Breakdown by enzymes
  • Re-absorption back into the presynaptic terminal
  • Diffuse away from the synapse
46
Q

What is meant by the term resting membrane potential?

A

What is meant by the term resting membrane potential? Difference in charge across cell membrane

47
Q

What are the charges (voltage) either side of the cell membrane in a resting cell?

A

Inside is -70mV

48
Q

What changes occur in the RMP when a neuron is stimulated?

A

Depolarisation – when the membrane potential becomes more positive i.e. the inside of the cell becomes more positive. E.g. - 70 mV -> - 30 mV

Hyperpolarisation – when the membrane potential becomes more negative i.e. the inside of the cell becomes more negative. E.g. - 70 mV -> - 75 mV

Repolarisation – membrane potential returns to normal

49
Q

Why is there a difference in the conduction velocity of a myelinated cell compared to an unmyelinated one?

A

nodes of Ranvier speed up conduction

50
Q

What occurs at the synapse?

A

Action potential arrives at the presynaptic terminal, This causes voltage gated calcium ion channels to open, so these channels only open when there’s a change in voltage and that change in voltage comes by the action potential. So these channels open allowing calcium to flood in to that presynaptic terminal and they move in moving down their concentration gradient. Calcium ions cause these synaptic vesicles to move closer to the presynaptic membrane and then these vesicle fuse with the membrane and release content (neurotransmitters) into the synaptic cleft (space between the 2 membranes). Neurotransmitters then diffuse across the cleft and bind to the ligand gated sodium ion channels, causing them to open allowing sodium ions to move into the cell. Action potential is generated such as muscle contraction if a muscle was the effector.

51
Q

What are the main parts of a reflex arc?

A 
Sensory receptor 
Sensory neuron 
Interneuron 
Motor neuron 
Effector organ

HSF (8 decks)

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