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NUR112 > WEEK 3 BIOSCIENCE - INTRO TO THE NERVOUS SYSTEM > Flashcards

WEEK 3 BIOSCIENCE - INTRO TO THE NERVOUS SYSTEM Flashcards

1
Q

Functions of the nervous system

A
  • sensory function: receptors detect sensory input, which is sent to the control centre
  • integrative function: analyses and interprets sensory input, determines an appropriate response, generates motor output that causes the response
  • motor function: issues motor function to activate effector
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2
Q

general sensory receptors

A
  • thermoreceptors: detect changes in temperature
  • nociceptors: detect painful stimuli
  • mechanoreceptors: tactile receptors (touch, pressure & vibration), baroreceptors (changes in blood pressure), proprioceptors (body position)
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3
Q

special sensory receptors

A
  • photoreceptors: detect light
  • chemoreceptors: detect chemicals in solution
  • mechanoreceptors called hair cells: detect hearing and balance stimuli
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4
Q

motor output

A

Activates a specific muscle to contract or a gland to secrete to cause a response

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5
Q

CNS

A
  • consists of the brain and spinal cord
  • control centre -> performs the function of integration
  • controls our emotions, behaviours and personality
  • performs intellectual (cognitive) functions
  • stores memories
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6
Q

PNS

A
  • consists of sensory receptors and the cranial, spinal and peripheral nerves that link all parts of the body to the CNS
  • cranial nerves and their branches primarily innervate structures of the head and neck
  • spinal nerves branch to form the peripheral nerves that innervate all parts of the body below the head
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7
Q

PNS sensory division

A
  • afferent
  • conveys sensory input from receptors to the CNS
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8
Q

PNS motor division

A
  • efferent
  • conveys motor output from the CNS to a muscle or gland
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9
Q

Motor division: somatic nervous system

A
  • conveys “somatic” motor output from the CNS to the body’s skeletal muscles
  • somatic motor output controls voluntary skeletal muscle movements and involuntary skeletal muscle movements (somatic reflexes)
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10
Q

Motor division: autonomic nervous system

A
  • conveys “autonomic” motor output from the CNS to the body’s glands, cardiac and smooth muscles
  • autonomic motor output controls involuntary activities: heart rate, respiration, blood vessel and pupil diameter, digestion of food, urination and defecation, perspiration and salivation
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11
Q

autonomic NS: sympathetic division

A
  • controls “fight or flight” activities -> activates body functions that support physical activity and inhibits those that don’t
  • increases heart rate, respiratory airflow, blood flow to skeletal muscles and sweat gland activity
  • dilates pupils
  • inhibits digestive functions
  • inhibits urination and defecation
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12
Q

autonomic NS: parasympathetic division

A
  • controls “rest and digest” activities -> activates body functions that conserve and restore body energy
  • stimulates digestive functions, urination and defecation
  • constricts pupils
  • decreases heart rate
  • decreases respiratory airflow
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13
Q

neuroglia

A
  • support neuron development and function
  • six different types of cells which collectively nourish, protect, insulate and structurally support neurons
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14
Q

structural components of a neuron

A
  • dendrites
  • cell body
  • axon (fiber)
  • axon terminals
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15
Q

dendrites

A
  • short processes
  • are the central receptive (or input) region of a neuron
  • act as sensory receptors to detect stimuli
  • receive information from other neurons
  • convert the information they receive into a graded potential which conveys the information towards the cell body
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16
Q

cell body

A
  • Contains a nucleus and organelles, e.g., ribosomes, to synthesise chemical neurotransmitters
  • Receives information from other neurons & converts this information into a graded potential
  • Integrates information (graded potentials) and conveys information towards the initial segment (or first part) of the axon
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17
Q

axon

A
  • A single process that connects to the cell body at the axon hillock
  • Is the conducting region of a neuron
  • generates & conducts action potentials to convey information from the initial segment to the axon terminals
  • Can be covered with a segmented myelin sheath
18
Q

myelin sheath

A
  • produced by Schwann cells and oligodendrocytes
  • increases the speed of signal conduction
  • gaps separate segments called nodes of Ranvier (internodes)
  • the destruction of myelin (oligodendrocytes) in the CNS à multiple sclerosis
19
Q

axon terminals

A
  • Form a synapse with another cell i.e. a neuron, muscle or gland
  • Are the secretory region of a neuron
  • contain synaptic vesicles that store and release
    neurotransmitters chemicals that carry the
    information from one neuron to another
    or to a muscle cell or gland
20
Q

Neuron cell bodies are organised into…

A
  • nuclei (nucleus) in the CNS
  • ganglia (ganglion) in the PNS
21
Q

Neuron axons are bundled into…

A
  • tracts in the CNS
  • nerves in the PNS
22
Q

classifications of neurons

A

multipolar
bipolar
unipolar

23
Q

sensory neurons

A
  • Conduct sensory input from receptors to the CNS
  • Unipolar in structure
24
Q

interneurons

A
  • Conduct information within the CNS
  • Multipolar in structure
25
Q

motor neurons

A
  • Conduct motor output away from the CNS to a muscle or gland
  • lower motor neurons conduct somatic motor output
  • preganglionic & postganglionic neurons conduct autonomic motor output
  • Multipolar in structure
26
Q

chemically gated channels

A
  • Open in response to a chemical stimulus, e.g. neurotransmitters
  • Located along the plasma membrane of the dendrites & cell body
27
Q

mechanically gated channels

A
  • Open in response to mechanical stimulation e.g. touch, vibration and pressure
  • Located along the plasma membrane of
    the dendrites
28
Q

voltage-gated channels

A
  • Open and close in response to voltage changes (i.e. changes in membrane potential)
  • Located along the plasma membrane of the axon and axon terminals
29
Q

depolarization

A

= membrane potential becomes less negative
- When a stimulus opens Na+ gated channels:
-> influx of Na+ ions into the ICF
-> ICF gains +ve ions cell interior becomes less negative
-> membrane potential becomes less negative e.g. -70 mV to -60 mV

30
Q

hyperpolarization

A

= membrane potential becomes more negative
- When a stimulus opens K+ gated channels:
-> efflux of K+ ions out of the ICF
-> ICF loses +ve ions cell interior becomes more negative
-> membrane potential becomes more negative e.g. -70 mV to -80 mV

31
Q

graded potentials

A
  • Are small changes in the membrane potential (i.e., small depolarisation or hyperpolarisation)
  • Originate in the dendrites or cell body of a neuron, when
    a stimulus opens chemically-gated or mechanically-gated
    channels
  • Are short-distance signals
  • distance travelled is proportional to stimulus strength
  • stronger stimulus = bigger change in membrane potential = further signal will travel
32
Q

for an action potential to occur:

A
  • in response to a stimulus, a graded potential can:
    -> travel to the initial segment of an axon
    -> depolarise the initial segment to -55 mV = threshold
    -> stimulate voltage-gated Na+ channels to open
    -> generate an AP
33
Q

action potentials

A
  • Are long distance signals
  • Originate at the initial segment of an axon
  • Involve voltage-gated channels
  • Are self-propagating
34
Q

action potential: depolarisation

A

At threshold (-55 mv):
* voltage-gated Na+ channels open
* Na+ ions enter ICF
* membrane potential becomes LESS negative shifts from -55 mV to +30 mV

35
Q

action potential: repolarisation

A

At +30 mV:
* voltage-gated Na+ channels close
* voltage-gated K+ channels open
* K+ ions leave ICF
* membrane potential RETURNS to resting state shifts from +30 mV to -70 mV

36
Q

action potential: hyperpolarisation

A

As the membrane potential approaches -70 mV
* voltage-gated K+ channels close slowly
* excess K+ ions leave ICF
* membrane potential becomes MORE negative shifts from -70 mV to -90 mV

37
Q

continuous conduction

A
  • Occurs in unmyelinated axons
  • Action potentials are generated at the voltage-gated channels along the length of the axon
  • Conduction occurs at speeds ≤ 2 m/s
38
Q

saltatory conduction

A
  • Occurs in myelinated axons
  • Action potentials are generated at the nodes of Ranvier
  • Conduction occurs at speeds >100 m/s
39
Q

what can impair an action potential?

A
  • Local anesthetics block voltage-gated Na+ channels
    -> no action potential
    -> no conduction of pain signal to the brain
    -> no sensation of pain
  • Cold and pressure reduced pain sensations by impairing signal conduction
40
Q

chemical synapse

A
  • A junction that mediates the transfer of information
  • At a chemical synapse between two neurons:
    -> the neuron sending the information = presynaptic neuron
    -> the neuron receiving the information = postsynaptic neuron
    -> a synaptic cleft separates presynaptic and postsynaptic membranes
    -> signal transmission involves chemical neurotransmitters
41
Q

information transfer at a synapse

A
  1. Action potential arrives at and depolarises axon terminal.
  2. Voltage-gated Ca2+ channels open.
  3. Influx of Ca2+ triggers synaptic vesicles to release neurotransmitter into the synaptic cleft.
  4. Neurotransmitter binds to chemically-gated channels on the postsynaptic neuron (dendrites or cell body).
  5. Chemically-gated ion channels open Na+ ions enter ICF plasma membrane of postsynaptic neuron depolarises graded potential known as an “excitatory postsynaptic potential” (EPSP) is produced
  6. EPSP depolarises initial segment of postsynaptic neuron to threshold (-55 mV) action potential generated information successfully transmitted
42
Q

termination of synaptic transmission

A
  1. The neurotransmitter diffuses away from the synaptic cleft
  2. The neurotransmitter is degraded by enzymes present in the synaptic cleft
  3. The neurotransmitter re-enters the axon terminal and is destroyed by enzymes or reused. This process is known as reuptake.

NUR112 (10 decks)

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