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NUR1112- Bioscience > 3: Nervous system > Flashcards

3: Nervous system Flashcards

1
Q

Define homeostasis

A

the process by which the body maintains a relatively stable internal environment.

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2
Q

What are the 3 systems that maintain homeostasis

A

1- sensory function (detects and sends)
2- Integrative function (analyses, interprets and generates a response)
3- motor function (issues output)

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3
Q

Define general sensory receptors

A 
located in the skin, skeletal muscles, tendons, joints and visceral organs. 
Include;
thermoreceptors 
nociceptors 
mechanoreceptors
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4
Q

What does the general sensory receptor thermoreceptors detect?

A

detect changes in the temperature

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5
Q

What does the general sensory receptor nociceptors detect?

A

detect painful stimuli

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6
Q

what are the three types of mechanoreceptors and what do they detect

A

tactile- touch, pressure and vibration
Baroreceptors- blood pressure
proprioceptors- changes in body position (proprioception)

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7
Q

Where are special sensory receptors located?

A

eyes, ears, mouth and nose

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8
Q

What are some examples of special sensory receptors

A

photoreceptors- detect light (vision)
Chemoreceptors- detect chemical solutions (taste and smell)
Mechanoreceptors called hair cells (detect hearing and balance)

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9
Q

What are the two divisions of the nervous system?

A

CNS and PNS

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10
Q

CNS structures and functions

A 
structure= brain and spinal cord 
Function= control centre that performs integration
  • controls emotions, behaviours and personality
  • performs intellectual (cognitive) functions
  • stores memories
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11
Q

PNS structures and functions

A

structure= contains sensor receptors, cranial, spinal and peripheral nerves.

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12
Q

Cranial nerves structure and function

A

branch primarily innervate structures of the head and neck.

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13
Q

Spinal nerves structure and function

A

Spinal nerves branch to form the peripheral nerves that innervate all parts of the body below the head.

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14
Q

What are the two divisions of the peripheral nervous system?

A

sensory (afferent)
- conveys sensory input from receptors to the CNS

motor (efferent)
- converts the motor output from CNS to muscles or glands

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15
Q

What are the two divisions of the motor division?

A

autonomic and somatic

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16
Q

Describe the somatic nervous system and what it controls.

A

conveys somatic motor output from CNS to skeletal muscles

Voluntary= skeletal muscle movement
involuntary= skeletal muscle movements (smoatic reflexes)
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17
Q

Describe the somatic nervous system and what it controls.

A

conveys autonomic motor output from CNS to glands, cardiac and smooth muscles

controls involuntary activities

e. g.
- heart rate
- respiration (respiratory air flow)
- blood vessel and pupil diameter
- digestion of food
- urination and defecation
- perspiration and salivation

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18
Q

What are the two functions of the autonomic nervous system

A

sympathetic

parasympathetic

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19
Q

Describe the sympathetic division

A

“fight or flight”- activities
- activated the body functions that support physical activity and inhibits those that don’t.

  • increases heart rate, respiratory air flow, blood flow to skeletal muscles and sweat gland activity.
  • dilates pupils
  • inhibits digestive function
  • inhibits urination and defecation
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20
Q

Describe the parasympathetic division

A

“rest and digest”- activities

  • conserves energy and promotes the body’s housekeeping functions
    e. g.
  • stimulates digestive function, urination and defecation
  • constricts pupils
  • decreases heart rate
  • decreases respiratory flow
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21
Q

What are the two key components of the nervous system

A
  • neuroglia

- neurons (nerve cells)

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22
Q

Define neuroglis

A

“nerve glue”
support neuron development and function, nourish, protect, insulate and structurally support neurons

Most brain tumours are made of neuroglia.

6 main types

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23
Q

What are the three basic functions of the nervous system?

A

1- detect chnages (stimuli) occuring inside and outside the body

2- respond to these changes by altering the activities of organ systems

3- coordinate the activities of all organ system

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24
Q

What are the four main types of effectors

A
  • skeletal muscles
  • cardiac muscles
  • smooth muscles
  • glands
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25
Q

Define neurons

A

the basic structure of the nervous system.
Function: communication.

  • when stimulated they generate electrical signals called graded potentials and action potentials to conduct sensory and motor information from one part of the body to another.

high metabolic rate
- Needing a high supply of oxygen and glucose for survival.

unable to divide and replace themselves if destroyed.

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26
Q

What are the 4 main components of a neuron

A
  1. Dendrites
  2. cell body
  3. axons (fiber)
  4. axon terminals
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27
Q

Describe dendrites

A

Structure= finger-like trees at the top of a nerve.

Function= main receptive (or input) region
- act as sensory receptors- detect stimuli

Large surface area= allows them to detect stimulus and receive info effectively.

convert info they receive to graded potentials which they send to cell body

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28
Q

Describe the cell body

A

contains nucleus and organelles

  • crecieves info, intergrates and sends incoming information to the axon
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29
Q

Describe the axon (aka fibre)

A

The conducting region.

“conducting region” that generates (initial segment) and conducts action potentials to convey information from the initial segment to the axon terminal.

  • can be mylinated
30
Q

Axon hillock

A

conducting region between cell body and axon

31
Q

Describe myelin

A 
structure= white and fatty 
function= speeds up transmission

produced by schwann cells and oligodendrocytes

32
Q

What diseases are associated with mylein damage

A

Loss of myelin slows myelin conduction and can determinate so much that conduction stops.
Aka multiple sclerosis

33
Q

Define nodes of ravier (internodes)

A

gaps in the myelin

34
Q

Describe the axon terminal

A

synapses with another cell

=secretory region

  • releases neurotransmitters (chemicals that carry info to another cell)
  • contain synaptic vesicles which store and release neurotransmitters (chemical that carry info)
35
Q

Where are nuclei (nucleus) and ganglia (ganglion) located and what are they?

A

nuclei (nucleus)= CNS
ganglia= PNS

  • they are clusters of neuron cell bodies
36
Q

What is the function of nuclei (nucleus)

A

Function= integration

  • Analyse and interpret sensory input
  • Analyse and decide on a motor response.

Some nuclei located in the brain

- Store memory 
- Determine personality 
- Regulate emotion 
- Perform intellectual function 
- Produce hormones
37
Q

neuron axions are bundled to form what in where?

A

Tract in the CNS
- conduct sensory and motor info through spinal cord and different areas of the brain.

Nerves in the PNS
-conduct sensory input to CNF and motor output away from CNS

38
Q

What are the three strutural clasifications of neurons and where are they found

A

Bipolar
(cell body in the middle, unmylenated)
- rare (in special sense organs e.g. ear, eye)

unipolar
(detached cell body)
- PNS

multipolar
(regular looking)
- CNS and PNS

39
Q

Structure and function of sensory neurons

A 
S= uniploar 
F= sensory input from receptors to CNS
40
Q

Structure and function of interneurons

A 
S= multipolar 
F= conduct information within CNS
41
Q

Structure and function of motor neurons

A

S- multipolar
F= conduct motor output away from the CNS to a muscle or gland

lower motor neuron= somatic motor output

pre and post ganglionic= autonomic output

42
Q

The basic principle of RMP

A

opposite changes attract so energy is required to keep them apart. aka. potential energy
stored/potential energy= measured in V or mV

43
Q

Define membrane potential

A

the potential energy that is separating the
internal negative
and the
external positive changes

44
Q

When does a change in membrane potential occur

A

when an ion k+ leaves or Na+ goes into the cell changing the charge strength.

this creates an electrical signal

summary= ions flow across the plasma membrane of a neuron- membrane potential (voltage) changes- electrical signal generated

45
Q

What must a neuron do they generate an electrical signal

A

their plasma membrane must;

  • exhibit a resting membrane potential (RMP)
  • contain protein channels that allow specific ions to diffuse down their concentration gradient.
46
Q

What are the two main types of channels that let K+ and Na+ ions though to change membrane potential?

A

leakage channels= always open, the small number allowed to cross

Gated channels= stimulated to open and close, large numbers allowed to cross

summary= when a stimulus opens gated ion channels, multiple/large number of ions move across

47
Q

What are the three types of gated channels?

A

chemically gated
mechanically gated
voltage-gated

48
Q

Explain simulation and location of chemically gated channels

A

open in response to chemical signals
e.g. neurotransmitter binds to a channel causing it to open. This means ions are free to cross

location= along plasma membrane of dendrites and cell bodies

49
Q

Explain simulation and location of mechanically gated channels

A

open in response to mechanical stimulation
e.g. touch, vibration and pressure

location= along the plasma membrane of dendrites

50
Q

Explain simulation and location of voltage gated channels

A

Open and close response to voltage changes or changes in membrane potential.

Location= along the plasma membrane od the axon and axon terminals.

51
Q

What gated channels are on the membranes of;
dendrites
cell bodies
axons and axon terminals

A

Dendrites: mechanically and chemically gated channels

Cell body: chemically gated

Axon and axon terminals: voltage gated channels

52
Q

Define resting membrane potential (RMP)

A

= the voltage across the plasma membrane of a resting (unstimulated) cell

it exists because of an uneven distribution of positive ions across the plasma membrane creates a charge difference across the membrane.
ECF= overall positive
ICF= overall negative

53
Q

what is the aprox RMP

A

-70mV

54
Q

Compare the ECF to ICF in terms of charge

A

ECF= high concentration of Na+ ions

  • more +ve ions
  • overall positive charge

ICF= hugh concr=entration of K+ ions

  • less +ve ions
  • overall negative charge
55
Q

Depolarisation=

A

the membrane becomes less negative
- means it moves from -70 towards 0.
D= depolarise= decrease negativity

sodium gated channels open letting Na= (more positive) into the less negative ICF—– this decreases the RMP to -60 e.g.

56
Q

Hyperpolarisation=

A

membrane becomes more negative

when a stimulus opens K+ gated channels allowing a great number of K+ ions into the ECF, the ICF becomes more negative (loses positive K+ ions)
RMP= more negative e.g. - 70mV to -80mV

57
Q

What happens to the RMP when hyperpolarisation and depolarisation occurs

A 
hyper= more negative 
depola= less negative
58
Q

Explain graded potentials

A
  • Small changes in membrane potential (de or hyperpolarisation)
  • Occur in dendrites or cell body when stimulus opens the chemically mechanically gated channels.
  • Short stimulus
  • strong stimulus= bigger change in membrane potential= further signal will travel
59
Q

Explain how a graded potential leads to an action potential

A
  • once stimulated by chemical or chemical stimulant on cell body or dendrite occurs, a graded potential is created. The short burst is send to the initial segment. the stronger the stimulus= treating RMP change= signal will travel further
  • AP depolarises initial segment to -55mV = threshold
  • this stimulates voltage-gated Na+ channels to open
  • this generates AP

Actions potential is generated if a stimulus is so loge the graded potential has enough strength to travel to the imitial segment wich depolarises the initial segment to -55mV= threshold which then stimulates voltage gated Na+ channels to open this then generates action potential.

60
Q

What are some properties of action potentials?

A
  • long distance
  • originate at initial segment
  • involve voltage-gated channels
  • self propelling aka. fist AP triggers 2nd AP triggers 3rd AP
61
Q

Action potential are generated by what three consecutive changes in the membrane potential?

A

depolarisation
depolarisation
hyperpolarisation

62
Q

Describe depolarisation

A

once at -55mV, voltage gated chnannels open to let even more Na+ past to get it +30mV

  • occurs at -55mV (membrane has got less natuage when Na+ channels have opened up and Na+ comes in)
  • axon interior becomes less negative
  • membrane potential shifts from -55mV to +30mV
63
Q

Desctibe repolarisation

A
  • occurs when membrane hits +30mV
  • voltage gated Na+ channels close and voltage gated K+ channels open to ket K+ out of the ICF
  • loss of K+ ions makes the RMP move closer to -70mV
64
Q

Describe hyperpolarisation

A

as the membrane aproaches -70mV it closes vo;tage gated channels however they are slow to close so K+ continue to flow into ECF

  • axon interior becomes more negative e.g. -70mV to -90mV
  • when K+ channels close, the movement of Na+ and K+ through leakage channels and ATPase pump resotres RMP back to -70mV
65
Q

Explain continuous conduction

A
  • occurs in unmyelinated axons
  • AP generated at voltage-gated channels along the axon
  • slow conduction (< 2m/s)
66
Q

Explain saltatory conduction

A
  • occurs in myelinated axons
  • action potentials generated at nodes of ravier
  • very fast >100m/s
  • signals skip and leap down axons via nodes od ravier
67
Q

How does localised anesthetic impact action potentials

A
  • blocks sodium gated channels so no pain or sensation can be conducted to the brain
  • block pain transmission by blocking Na+ gated channels. Therefor no Na+ entering axon so no depolarisation occurs.
68
Q

Define a chemical synapse

A

A junction that mediates the transfer of information from one neuron to another or neuron to a muscle or gland.

presynaptic neuron- post synaptic neuron through synaptic cleft via neuro transmitters

69
Q

Steps of information transfer

A

1- action potential arrives at axon terminal and depolarises
2- depolarisation stimulates voltage gated Ca2+ channels (on the membrane) to open and Ca2+ to enter the terminal
3- Ca2+ entrance triggers synaptic vesicles to release neurotransmitters into synaptic cleft
4- neurotransmitters diffuse across the synaptic cleft and bind to chemically gated channels on the post synaptic membrane of cell body or dendrite.
5- binding of neurotransmitter opens chemically gated channels- influx of Na+ into ICF=depolarisation= graded potential created (excitatory postsynaptic potential- EPSP)- EPSP travels and depolarises at initial segment of post synaptic neuron to threshold 9-55mV= action potential generated
- info successfully transmitted

70
Q

Describe the 3 terminations of synaptic transmission

A

1- neurotransmitters diffuse away from synaptic cleft
2- are degraded by enzymes in synaptic cleft
3- NT’s re-enters axon terminal and is destroyed by enzyme or reused, aka re uptake

NUR1112- Bioscience (10 decks)

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