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PHYL 2041 > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

Nervous system

define

general functions (3)

A
  • A communication and control network that allows an organism to interact with its environment
  1. Sensory detection
  2. info processing
  3. expression of behaviour
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2
Q

Central nervous system made up of

A

brain and spinal cord

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3
Q

divisions of peripheral ns?

A

Afferent/sensory division

Afferent/motor division

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4
Q

What makes up the nervous system? (4)

A
  1. Neurons - functional unit
  2. Neuroglial cells - microglial, astrocytes, dendrocytes
  3. Blood vessels - provide nutrients and energy
  4. Connective tissue - provide support
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5
Q

Where does inhibitory and excitatory input go on neuron?

A

Inhibitory onto cell body and excitatory onto dendrites

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6
Q

Features of:

cell body

soma

dendrites

axons

axon hillock

neural network

A
  • contain organelles
  • factory of cell - makes proteins + membrane structures
  • input transmission - carry info to neuron
  • output transmission
  • Important for AP generation - contains all necesary ion channels
  • APs fire along neural network to ensure that NS functions properly
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7
Q

unpolar neurons dominant in

A

invertebrates

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8
Q

Bipolar neurons extend to?

A

One end to CNS and one to PNS

Carry info from PNS to CNS

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9
Q

pseudounipolar neurons

A
  • develop from bipolar neurons
  • One extension from cell body that divides
  • One end to PNS and one to CNS
  • Sensory neurons
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10
Q

Multipolar neurons

A
  • Dominant in vertebrates
  • One axon that carries info to muscle cells
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11
Q

Distribution of neurons in body

A
  • 90% interneurons - multipolar, make connections
  • 9% Motor neurons - mostly multipolar
  • 1% sensory neurons - mostly bipolar and pseudounipolar. Carry info from receptor cells in sensory organ to upper level neurons
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12
Q

Axonal tranport

Fast:

Slow:

Anterograde:

Retrograde:

Importance:

A
  • Dast transport for membrane bound organelles and mitochondria
  • Slow transport for proteins
  • Anterograde - from soma toward terminals. Uses kinesin
  • Retrograde - from terminals toward soma. Uses dynien
  • Important for neurotransmission bc many structure in cell body need to get to nerve terminal that can’t do it through diffusion
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13
Q

Why can Shingles affect the skn after many years latency?

A
  • Caused by chicken pox firus
  • Stays dormant in cells for many years after infection
  • Virus can reactivate and will be transported from cell, down axon - affecting skin
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14
Q

Supportive matrix of CNS

A

provides local environment for nearons to function (neuroglia)

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15
Q

Neuroglia in CNS (list)

A
  • Astrocytes
  • Oligodendrocytes
  • Microglia
  • Ependyomal cells
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16
Q

Astrocytes

A

Neuroglia in CNS

structural support, metabolic support, encourage NT uptake/release, nervous system repair, ion homeostasis, synaptic plasticity

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17
Q

Oligodendroglia

A

Neuroglia in CNS

myelination of CNS axons

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18
Q

Microglia

A

Neuroglia of CNS

  • Immune defense => phagocytes
  • Activated when CNS is injured, release factors to help with repair
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19
Q

Ependymal Cells

A

Neuroglia of CNS

produce cerebrospinal fluid

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20
Q

Neuroglia in PNS

A
  1. Satellite cells - function similarly to astrocytes (around the cell body)
  2. Schwaan cells - 1 group does myelin, other do debris clearance and nerve regeneration
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21
Q

Myelination in CNS vs PNS

A
  • CNS - oligodendroglia. Single oligodendrocyte myelinates many axons
  • PNS - Schwann Cells - Each cell myelinates only one axon
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22
Q

neurons vs neuroglia

A

Neurons

  • Lots of brances, one long axon
  • Can generate APs
  • Cab regulate functions
  • Can’t divide

Neuroglia

  • Don’t branch extensively
  • Not excitable
  • Supporting unit of nerve cell
  • Can divide - replication afected by tumors
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23
Q

What cells can give rise to brain tumors in the adult brain?

In infants?

A

Atrocytoma, oligodendroglioma, ependyoma

In infants: neuroblastoma

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24
Q

Grey matter

vs

white matter

A

soma and dendrites (axons, glial cells, capillaries)

acons (glial cells, capillaries). White bc of myelination

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25
Q

Why does grey matter have a higher metabolic rate?

A

Cell body located in grey matter. Factory for all proteins and cell components for neuron, therefore has higher metabolic rate.

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26
Q

Brainstem made up of

A

(not hypothalmus though it sits on top)

Midbrain

Pons

Medulla

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27
Q

Functions of the brainstem and its components

A
  • Brainstem - autonomic centres and relay nuclei
  • Midbrain: micturition, eye movement, auditory and visual systems
  • Pons: balance, maintenance of posture, breathing
  • Medulla: breathing, blood pressure, swallowing, coughing, vomiting reflexes
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28
Q

Cerebellum

location

functions

A
  • Between cerebral cortex and spinal cord. Attached to brainstem and lies dorsal to pons and medulla
  • Coordination of movement, maintenance of posture and balance
  • Receives important info from spinal cord
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29
Q

Thalamus and hypothalamus

A
  • Between cerebral hemispheres and brainstem - in diencephalon (meaning bt brain)
  • Thalamus processes sensory information going to cerebral cortex and motor info coming from cerebral cortex to brainstem+spinal cord
  • Hypothalamus regulates body temp, food intake, water balance, hormone secretions or pituitary
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30
Q

Cerebrum

location

structure

consists of

functions

A
  • Located in anterior (front) portion of brain
  • Divided into left and right hemispheres that are connected by corpus callosum (axon bundle)
  • Cerebral himispheres consist of cerebral cortex (grey matter) and underlying what matter and 3 deep nuclei (basal ganglia, hippocampus, amygdala)
  • Functions: perception, higher motor functions, cognition, memory and emotion
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31
Q

3 deep nuclei in cerebrum

A

basal ganglia, hippocampus and amygdala

  • Basal ganglia - base of forebrain, movement, parkinson’s disease, huntington’s disease
  • Hippocampus - located in temporal lobe, memory
  • Amygdala - In temporal lobe, emotion
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32
Q

Cerebral Cortex

gyrus

sulcus

lobe divisions

areas

functions

A
  • gyrus = ridges on cortex
  • sulcus = grooves on cortex
  • Divides into frontal, parietal, occipital and temporal lobes
    • Sylvian/lateral fissure divides frontal/temporal and parietal/temporal
    • Longitudinal fissure divides the two hemispheres
  • Areas: motor, sensory, association areas
  • Functions: recieves and processes sensory information and integrates motor functions
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33
Q

Most of the brain is made up of associations areas (Eg the somatomotor cortex has the motor cortex and the association area of that cortex that is much larger)

why is this?

A

Higher brain function = perception

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34
Q

The ventricular system

A
  • The system that the cerebrospinal fluid runs through
  • 4 ventricles in brain
  • Connected by foramina:
    • Interventricular foramina connects ventricles 1 + 2
    • cerebral aqueduct connects 3 + 4
      *
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35
Q

cerebrospinal fluid

what is it?

produced by

can be sampled by

function

A

Liquid that fills and circulates within the ventricular system of brain

  • Produced by choroid plexus
  • Can be sampled by a lumbar puncture (lumbar cistern)
  • Distributes nutritive materials to and removes waste from nervous tissue; protection of the brain
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36
Q

hydrocephalus

A
  • Abnormal accumulation of cerebrospinal fluid in ventricles
  • Increased pressure that causes disease
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37
Q

Nervous system reaction to injury

A
  1. Degeneration
    • Effector denervated
    • Wallerian degeneration - axon pulls up toward the cell body
    • Chromatolysis = dissolution of nissl bodies in cell body
  2. Regeneration - in PNS but not in CNS
    • Severed axon begins to srpout and can allow regeneration
  3. Axon growth = trophic factors (NGF, neurotrophin, CNF)
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38
Q

Nissl Body

A

large granular body founf in neurons. Rough ER with free ribosomes and parts of golgi. Seen in soma and dendrites. Not axon.

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39
Q

Non-traditional senses

A
  • Nocicpetion - pain, helps you avoid damage
  • Equilibrioception - body balance when walking/standing
  • Proprioception - Sense of relative body parts
  • Thermoception - sense of temperature around skin
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40
Q

Sensory receptors are

3 types

A

specialized structure activated by stimuli, that convert a stimulus into neuronal activity (electrical activity)

they are one of:

  1. Endings - most simple. Nerve terminal of afferent neurons (somatosensory and olfactory systems)
  2. Specialized epithelial cells adjacent to an afferent neuron (visual, taste and auditory systems)
  3. Specialized structure associated with nerve terminals (Pacinian corpuscule)
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41
Q

Mechanoreceptors

modality

receptor

location

A
  • Touch (pressure), audition, vestibular
  • Pacinian corpuscule, hair cell
  • Skin, organ of Corti, semicircular canal
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42
Q

Photoreceptors

modality

receptor

location

A
  • Vision
  • Rods + cones
  • Retina
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43
Q

Chemoreceptors

Modality

Receptor

Location

A
  • Olfaction, arterial oxygen levels, oH of cerebrospinal fluid
  • Olfactory receptor
  • Olfactory mucosa, carotid and aortic bodies, ventrolateral medulla
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44
Q

Thermoreceptors

Modality

Receptor

Location

A
  • Temperature
  • Cold receptor, warn receptor
  • Skin
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45
Q

Nociceptors

modality

receptor

location

A
  • Stimuli causing tissue damage
  • Thermal nociceptor, mechanical nociceptor, polymodal nociceptor
  • Skin
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46
Q

A stimulus is converted to electrical energy by opening and closing of ion channels in sensory receptors, which results in receptor potentials

A
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47
Q

receptor potential

A
  • graded change in membrane potential of the sensory receptor.
  • Can be depolarizing or hyperpolarizing
  • Depolarizing receptor potential spreads within afferent neuron until it reaches a region with high density VGSCs
    • If receptor potential threshold is reached, AP generated
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48
Q

Receptor potential vs action potential

A

Receptor potential is a graded potential. The amplitude is graded with stimulus intensity. These potentials cannot propogate, only spread along the membrane.

Receptor potential can be hyperpolarizing or depolarizing

AP can only be triggered by a depolarizing current

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49
Q

Sensory Unit

A
  • Primary sensory neuron and all sensory receptors (endings or associated sensory receptor cells)
  • The smallest unit of sensory response
  • If the sensory receptor is a neuron terminal, then the sensory neuron is a sensory unit. If there is some associated epithelial cell + sensory neuron, then that is the sensory unit
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50
Q

Receptive Field

A
  • An area of the body surface that when stiumlated results in a change in firing of a sensory neuron.
  • vary in size
    • Smaller receptive field = more precise sensation
  • Higher order of CNS neuron, more complex receptive field
  • Receptive field can be excitatory or inhibitory depending on the change in firing rate
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51
Q

Sensory systems mainly code which 4 aspects of a stimulus?

A
  1. Stimulus Modality - type of stimulus
  2. Stimulus Intensity
  3. Stimulus location
  4. Stimulus duration: adaption
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52
Q

Adequate stimulus

A

Each sensory receptor is particularly sensitive to one stimulus type

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53
Q

Labeled line

A
  • The distinct anotomical pathways from sensory receptors to a specific region of the CNS associated with a particular stimulus modality
  • The attachment from the sensory receptor + higher level neurons + eventually to a specific region of the cerebral cortex = labeled line
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54
Q

Stimulus intensity encoded by

A
  1. Number of receptors that are activated
  2. Differences in firing rates of sensory neurons in a pathway. Increased Stim = increased AP frequency
  3. Activating different types of receptors (eg nociceptors as well)
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55
Q

Acuity

A
  • precision of stimulus location
  • Dense arrangement of sensory units => better acuity
  • Large receptive field => bad acuity
  • Lips and hands have good acuity
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56
Q

Lateral inhibition

A
  • The capacity of an excited neuron to reduce the activity of its neighbors
  • Further enhance sensory acuity

In image - firing frequency is decreased in all 3 secondary neurons, but the middle is suppressed less.

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57
Q

Adaption

A

Sensory receptors decrease in sensitivity to a stimulus of constant strength (AP frequency decreases)

  • Phasic = rapidly adapting sensory receptor. Generates RP and AP on onset, but quickly stops responding. Detects CHANGES in stimulus
  • Tonic = slowly adapting sensory receptor. Encodes DURANTION AND INTENSITY of a stimulus
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58
Q

Microneurography

A

Invasive method for visualizing normal traffic of nerve impulses

  • Can map receptove field of a neuron
  • Whenever a stimulus brings about a neuronal response, the response can be trecorded by an amplifyer
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59
Q

General features of sensory system (4)

A
  1. Synaptic relays
  2. Topographic organization
  3. Decussation
  4. Different types of nerve fibres
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60
Q

General feature of the Sensory System:

Synaptic relays

A
  • Relay nuclei in the thalamus integrate converging info from neurons in CNS. One neuron tends to get info from many lower neurons
  • Relay nuclei contain interneurons and projection neurons
    • Interneurons have important role in analyzing converging info/perception => association neurons
    • Projection neurons: sit along axon + send to higher order CNS. Carry info from relay nuclei to other parts of the brain
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61
Q

General Features of the Sensory System:

Topographic Organization

A
  • Neural maps
  • Somatotopic Map in somotosensory system (Sensory Homunculous)
  • Retinotopic map in visual system
  • Tonotopic map in the auditory system
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62
Q

General Features of the Sensory System

Decussation

A
  • Crossing of sensory (and motor) pathways in the spinal cord
    • Comissure - contains only axons (eg corpus callosum)
    • Optic Chiasma
  • Most sensory info will be conveyed to contralateral side of the brain
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63
Q

Convergence and divergence of ascending pathways

A
  • Divergence = one primary neuron synapses onto many higher order neurons
  • Convergence = A higher order sensroy neurons recieves input from more than 1 primary sensory neuron
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64
Q

Sensory processing in the Cortex (General)

A
  1. Ascending pathways terminate in specific sensory areas (eg innervation at eyes ==> visual cortex)
  2. Further processing occurs in associational areas where complete integration occurs
  3. Perception- understanding of sensations
    4.
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65
Q

Inhibition of ascending pathways by descending pathways

A
  • Directly or indirectly
  • Form of controlling ascending pathways
  • Not all sensory information reaches consciousness
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66
Q

Subdivisions of the Somatosensory System

A
  1. Proprioceptive division
  2. Enteroceptive division
  3. Exteroceptive division - responsible for providing information about contact of skin with objects in external world
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67
Q

3 major receptors of exteroceptive division of somatosensory system

A
  1. Mechanoreceptor
  2. Thermoreceptor
  3. Nociceptors
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68
Q

Somatosensory modalities

A

Information about touch, position, pain and temperature

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69
Q

Meissner’s corpunscule

location

adaption

sensation encoded

A
  • Mechanoreceptor
  • Only located in non-hairy skin
  • rapid adaption
  • Point discrimination, tapping, flutter
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70
Q

Pacinian Corpunscule

location

adaption

sensation encoded

A
  • Hairy and non hairy skin, intramuscular
  • very rapidly adapting
  • vibration, tapping
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71
Q

Hair follicles (mechanoreceptors)

location

adaption

sensation encoded

A
  • Hair skin
  • rapid adaption
  • Velocity, direction of movement
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72
Q

Ruffin’s corpunscule

A
  • hairy and non hairy skin
  • Slow adaption
  • stretch, joint rotation
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73
Q

Merkel’s receptors

location

adaption

sensation encoded

A
  • Nonhairy skin
  • slowly adapting
  • verticle identification of skin, light touch
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74
Q

Tactile disks (mechanoreceptors)

location

adaption

sensation encoded

A
  • Hairy skin
  • slow
  • verticle identation of skin
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75
Q

Operation of thermoreceptors

A
  • Respond to temperature change
  • Slowly adapting
  • Cold and warm receptors
  • Nociceptors activated by extreme heat
  • At body temp, both acting equally
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76
Q

TRP Channels

what are they

how many

structure

what ions

A
  • Associated with thermosensation. Responsible for some nociception
  • 27 types, 6 groups - respond to diff temps and chemicals
  • 6 TM domains and 1 imbedded domain between 5 and 6
  • Permeable to Na and Ca
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77
Q

Why does spicy food make you feel hot? Why does mint make you feel cool?

A

TRPV1 can be activated by spicy things and it’s also a heat receptor. TRPM8 activated by menthal and also a cold receptor.

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78
Q

TRP channels activated by high body temp and high external temp

A

TRP V1 and TRPV2

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79
Q

Thermal or mechanical nociceptors

A
  • Fast conducting
  • Adelta nerve fibres
  • Respond to mechanical or thermal stimuli such as sharp pricking pain
  • Fast first pain
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80
Q

polymodal nociceptor

A
  • Slow-conducting C fibres
  • Respond to high intensity mechanical, chemical and thermal stimuli
  • Slow second pain
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81
Q

Hyperalgesia

A

an amplified response to a noxious stimuli

sensitization of pain

82
Q

Allydonia

A

A painful response to a normally innocuous stimuli (like taking a bath when you have a sunburn)

83
Q

Inflammatory soup

A

Peptides, lipids, NTs, cacitonin gene-related protein and neurotrophins that are released by damaged tissue to help with repair

84
Q

Extreme cold TRP channels

A

TRPM8

TRP A1

85
Q

Innervation of the body by primary sensory neurons located in the ___________

A

dorsal root ganglion

86
Q

Dermatomal organization

A
  • Certain dorsal nerves arrive from ganglia in skin dermatomes
  • 31 nerve haris and 30 dermatomes (no dermatome for C1)
  • 1 dermatome = 1 dorsal nerve and the visceral and skin area that it innervates
87
Q

Shingles disease

A
  • After chicken pox infection, virus remains in dorsal rooted ganglion
  • When reactivated, virus transported along dorsal root axons to the area of skin in the dermatome
88
Q

Innervation of the face

A

by primary sensory neurons located in the trigeminal ganglion

89
Q

Dorsal column medial leminscus system

functions and process

A
  • Sensations: fine touch, pressure, two point discrimination, vibration
  • Graphthesia: the ability to recognize numbers or letters when traced on skin
  • 1st order neuron: large, myelinated (Aa, AB)
  • Fibres stay ipsilateral in spinal cord
  • 2nd order neuron in nucleus gracilis (upper body) or nucleus cuneatus (lower body) in the medulla
    • Decussation
  • 3rd order neuron in ventral posterior lateral nucleus of the thalamus
  • 4th order neuron in somatosensory cortex
90
Q

Anterolateral/Spinothalamic Pathway

A
  • Pain, temperature, crude touch
  • 1st order neuron - small, lightly myelinated and unmyelinated axons (Group III/IV). Synpase in grey matter.
  • 2nd order neuron in spinal cord
    • Decussation
  • 3rd order neuron in ventral postinferior nucleus of thalamus
91
Q

Damage to the sensory pathways

A

Damage below decussation will lead to loss of sensation on same side of lesion

Damage above decussation will lead to contralateral deficits

92
Q

Somatosensory Homunculous

A

Represents each part of the body in proportion to its number of sensory neural connections, but not its actual size

93
Q

Nociceptor fibres

A
  • Ad and C
  • Fast/first pain from Ad
    • Rapid onset and offset
    • Precisely located
    • Serves as warning signal
  • Slow/second pain from C fibres
    • More prologued, less intense
    • Poorly localized
    • More complex emotional response
94
Q

3 types of pain

A

nociceptive

inflammatory

neuropathic

95
Q

Nociceptive Pain

  1. Sensory neuron
  2. Site
  3. Involvement of TRP channels
  4. Clinical Setting
  5. Function
  6. Pain sensitivity
A
  1. Noxious
  2. Nociceptor
  3. PNS
  4. Yes TRP
  5. Acute Trauma
  6. Protective
  7. High Threshold
96
Q

Inflammatory Pain

  1. Sensory neuron
  2. Site
  3. Involvement of TRP channels
  4. Clinical Setting
  5. Function
  6. Pain sensitivity
A
  1. Inflammation
  2. nociceptor and non-nociceptor (high motor neurons involved)
  3. PNS and CNS
  4. Yes TRP
  5. Post operative pain and arthritis
  6. Healing/repair
  7. Low threshold
97
Q

Neuropathic pain

  1. Sensory neuron
  2. Site
  3. Involvement of TRP channels
  4. Clinical Setting
  5. Function
  6. Pain sensitivity
A
  1. neural damage to nerve passage or ectopic firing
  2. nociceptor and non-nociceptor
  3. PNS and CNS
  4. TRP unclear
  5. PNS and CNS lesions, diabetic neuropathy, lumbar radioculopathy, spinal cord injury
  6. Pathological
  7. Low threshold
98
Q

What type of pain for trigeminal neuralgia?

Trigger?

Treatment?

A
  • Can happen to elderly; Chronic pain
  • Neuropathic because artery gives a mechanical stimulus
  • Not because of inflammation or trauma
  • Treated by displacing the artery
99
Q

Gate control theory of pain

A
  • Innocuous stimuli are able to suppress pain
  • Mechanism: activation of inhibitory interneurons by innocuous stimuli applies to AB fibres results in inhibitiion of pain signals transmitted via C fibres to CNS
  • Eg patting head
100
Q

Referred Pain

A
  • Sensation of pain that is experienced at a site other than the injured tissue
  • Visceral origin - neurons in dorsal ganglia innervate sensory receptors in skin and visceral organs
  • Pain referred to a structure that originates from the same dermatome as the source of pain
  • Eg referred pain from heart to left arm
101
Q

Endogenous Analgesia System

A
  • Sensory information can be modiefied by your emotion
  • opioids released by NS bind to receptors that activate pathways that reduce pain via inhibitory interneurons
  • Morphine is an agonist for opioids receptors
102
Q

opioid examples

A

enkephalin, endorphins, dynorphin

103
Q

Treating Morphine OD

A

Naloxone - antagonist

104
Q

How does morphine relieve pain?

A
  • Morphine mimics opioids functions by activating endogenous analgesia system.
  • Use naloxone to treat overdose because it can bind to receptors and counter the effects of morphine
105
Q
  • descending pathways can inhibit (directly or indirectly) the transduction of sensory information to the brain*
  • ==> not all sensory information reaches consciousness*
106
Q

Efferent division of PNS divides into

A

Somatic NS

Autonomic NS

107
Q

Somatic Nervous System

A

voluntary control of body movements via skeletal muscles

voluntary nervous system

108
Q

Autonomic Nervous System

A

Involuntary controls of visceral organs via smooth muscles, cardiac muscles and glands

109
Q

Somatic NS

  1. Control type
  2. Number of neurons in pathway
  3. Cell body location
  4. Effectors
  5. Neurotransmitter and receptor
A
  1. Voluntary
  2. Single (motorneuron)
  3. CNS
  4. Skeletal muscles
  5. ACh/nAChR
110
Q

Autonomic NS

  1. Control type
  2. Number of neurons in pathway
  3. Cell body location
  4. Effectors
  5. Neurotransmitter and receptor
A
  1. Involuntary
  2. Two (preganglionic and post ganglionic)
  3. CNS (preganglionic neuron) and autonomic ganglion (post ganglionic neuron)
  4. Cardiac muscles, smooth muscles, glands
    • Preganglionic neuron: ACh/nAChR
    • Postganglionic neuron: ACh/mAChR and norepinephrine/a1, a2, B1, B2
111
Q

Autonomic nervous system divides into

A
  1. Sympathetic (fight or flight)
  2. parasympathetic (rest and digest, sexual arousal and salivation)

most organs innervated by both

112
Q

Sympathetic Divsion

  1. Set up
  2. Origin of preganglionic nerve
  3. Location of ganglia
  4. Length of preganglionic nerve
  5. Length of Postganglionic nerve
A
  1. 2 neurons in series connect the spinal cord and the effector
  2. Thoracolumbar
  3. Far from effector organs
  4. Short
  5. Long
113
Q

Adrenal Gland

A
  • Specialized sympathetic ganglion
  • Cell bodies of adrenal gland’s preganglionic neurons are located in the thoracic spinal cord
  • Axons of preganglionic neurons pass through the sympathetic chain and the celiac ganglion without synapsing and travel to the adrenal medulla where they synapse on chromaffin cells
114
Q

Parasympathetic nervous System

  1. Set up
  2. Origin of preganglionic nerve
  3. Location of ganglia
  4. Length of preganglionic nerve
  5. Length of Postganglionic nerve
A
  1. Two neurons in series connect CNS and effector organs
  2. Craniosacral
  3. Near or within effector organs
  4. Long pre-ganglionic neurons
  5. Short postganglionic neurons
115
Q

Neuromuscular Junction

Arrangement

Innervation

NT Storage Sites

Postsynaptic receptors

A
  • Discrete, organized structure called motor end plate
  • A skeletal muscle fibre is innervated by a single motor neuron
  • Nerve terminals
  • Postsynaptic receptors are located in the motor end plate
116
Q

Neuroeffector Junction

arrangement

innervation

NT storage sites

postsynaptic receptors

A
  • Diffuse, branching network
  • Target tissues may be innervated by many post ganglionic neurons
  • Varicosities
  • Postsynaptic receptors are widely distributed on target tissue
117
Q

Adrenergic neurons

adrenoreceptors

A

neurons that synthesize and release norepinephrine

a1, a2, B1, B2 - activated by norepinephrine or epinephrine

118
Q

Cholinergic neurons

Cholinoreceptors

A

neurons that synthesize and release ACh

nicotinic AChR, muscarinic AChR - activated by ACh

120
Q

A substantial amount of nicotine consumption will cause?

A
  1. Increased sympathetic response
  2. Increased parasympathetic response
121
Q

Non classical NTs for sympathetic NS and parasympathetic NS?

A

Para: VIP and NO

Sympa: ATP and Neuropeptice Y

122
Q

G Protein Couples Receptors

A
  • Autonomic receptors are couples to G Proteins
  1. Ligand binds
  2. GDP on a subunit is switched for GTP
  3. a + GTP dissociates, does a job
  4. GTP hydrolysis
  5. Return to a+B+Y inactive state
123
Q

Gs does

A

stimulates adenylyl syclase => more cAMP + more PKA

124
Q

Gi does

A

inhibits Adenylyl Cyclase => less cAMP, less PKA

125
Q

Gq does

A

Activates Phospholipase C => more IP3 + more DAG

IP3 => Ca2+

DAG => PKC

126
Q

a1 receptor does what with 2nd messengers?

A

stimulates PLC/IP3 => Ca2+ + PKC

127
Q

a2 receptor does what

A

inhibits AC/cAMP

smooth muscle of GI and blood vessels

128
Q

B1 and B2 autonomic receptors do what with second messengers?

where is B1/function

where is B2/function

A

stimulate AC and CAMP => PKA

SA node in heart, slivary glands, kidney / salivation etc

Smooth/skeletal muscle GI/bladder / relaxation and dilation

129
Q

Autoreceptor on sympathetic presynaptic regions

A

inhibits further release of norepinephrine from the same terminals

-ve feedback

130
Q

Heteroreceptor present on parasympathetic presynaptic regions

A

inhibits the release of ACh from parasympathetic postganglionic nerve terminals

131
Q

mAChR

A

activates PLC => IP3 + DAG => Ca2+ + PKC

Coupled to PLC and Gq protein

132
Q

nAChR

A

postganglionic neurons of the ANS

chromaffin cells

motor end plate of skeletal muscles

133
Q

Dual innervation by sympathetic and parasympathetic divisions

A
  • Most organs are dually innervated
  • Usually antagonistic
  • Sweat glands, adrenal medulla and blood vessels all only have sympathetic innervation
134
Q

Pupil

A

Dilates under sympathetic innervation due to increased NE release, a1 receptor activity in radial muscle -> mydriasis

135
Q

What is the pathophysiology of Horner’s Syndrome?

A
  • Miosis (pupil constriction). Less sweating, droopy eyelid. Damage to sympathetic nerves.
136
Q

Servomechanism

A

a control system uses -ve feedback to operate another system => eg vasomor centre in blood pressure regulation

137
Q

Temperature regulation by

A

central thermoceptors in anterior hypothalamus

138
Q

What is the mechanism for a fever?

A

Pyrogens increase the temp regulation set point in the hypothalamus

139
Q

Regulation of food intake

regulation of water intake?

A

glucoreceptors in hypothalamus

osmoreceptors in hypothalamus

140
Q

B1 activation; 5 outcomes

A

SA node - increased heart rate

AV node - increased conduction velocity

ventricular muscle = contraction

salivary gland - secretion

kidney - secrene renin

141
Q

corda equina

A

less nerve trunks near bottom of spinal cord so they come out in bundles that look like horse tails

142
Q

sympathetic nerves come out on the right side and segmental nerves on the other side

143
Q

Functions of the CNS

A
  1. Input of information - from external and internal environment
  2. Output of information to muscles, glands and control of some sense organs
  3. Integration of information - input +memory => output (behaviour)
    1. simple reflexes to complex behaviour
144
Q

Cranial nerves

A

Oh Oh Oh to touch and feel a girls vagina, ah heavan

  1. Olfactory
  2. Optic
  3. Oculomotor
  4. Trochlear (eye motor)
  5. Trigeminal (face sensory)
  6. Abducens (eye motor)
  7. Facial (face motor)
  8. Auditory (hearing balance)
  9. Glossopharyngeal (mouth sensory
  10. Vagus (autonomic)
  11. Accessory (neck motor)
  12. hypoglassal (tongue motor)
145
Q

Spinal cord function

A

input, output, local reflexes, modification of ascending and descending info

146
Q

Brainstem function

A

midbrain, pons, medulla

control of respiration, cardiovascular system, arousal, posture, visual reflexes, micturition, some auditory processing

147
Q

Cerebellum function

A

coordiantor of movement, balance

148
Q

diencephalon function

A

Thalamus, hypothalamus, pineal

control of sensory input, autonomic regulation

149
Q

Cerebrum functions

A

higher functions, speech, vision, end of sensory flow, start of motor flow

150
Q

corpus callosom function

A

major pathway for information bt the two hemispheres.

151
Q

Large axons are ___________ to stimulate

A

Easier.

A small stiumulus will exite mainly Aa efferects (motor neurons) or Ia afferents (from muscle spindles)

152
Q

Below 1um it isn’t energetically worth myelinating an axon

153
Q

Afferents are bipolar with cell bodies in dorsal root ganglion

154
Q

Outputs

Alpha

Gamma

Autonomic

A

Alpha - motorneurons to skeletal muscle

Gamma - motorneurons to muscle spindles

Autonomic - to visceral muscles and glands

155
Q

Inputs

Cutaneous

Muscle

Joints

Visceral

156
Q

Dorsal column medial leminscus system

Summary

A
  • Carries accurate touch, vibration and conscious proprioceptive information
  • Uses large diameter, faster conducting axons
  • Axons ascend ipisilaterally in the spinal cord to dorsal column nuclei in medulla
  • Second order neurons cross to the contralateral side before synapsing in the thalamus
157
Q

Anterolateral system summary

A
  • Carries pain and temp information
  • Neurons synpase in spinal cord
  • 2nd order neurons cross immediately and ascend contralaterally before synapsing in the thalamus
  • Third order neurons ascend to the somatosensory cortex and cingulate cortex (pain)
158
Q

Brown Sequard syndrome

A

damage to one side of the spinal cord causes loss of touch to one side of body and loss of pain and temperature to the other side

159
Q

Spinocerebellar system

A
  • Afferents from muscle and joint receptors
  • Large diameter, faster conduction axons
  • 1st order afferents synapse in the Clarke’s nucleus in spinal cord
  • 2nd order neurons ascend ipsilaterally in Clarke’s column and pass from brainstem to cerebellum
  • Cerebellum involved in movement, coordination, balance
160
Q

lateral tracts for which pathways

medial tracts?

A

corticospinal (pyramidal) and midbrain (rubrospinal) pathways

Include corticospinal and pathways from medulla, pons and vestibular

161
Q

Corticospinal System

A

Pyramidal System

  • fastest motor system - only 2 neurons from cortex to muscle
  • 80-90% corticospinal axons cross over at the front of brainstem and form pyramids
  • fine discriminatory movements of distal digits
  • Damage causes weakness, but primarily fingers affected
  • other 10-20% axons don’t cross over. They descend in the medial tract and cross over before synapsing on motor neurons
  • Analogous corticobulbar tract gives fine control of lower face muscles, including tongue + lips
162
Q

Extrapyramidal System

A
  • Any motor pathway that is not in corticospinal (pyramidal) system is in the extrapyramidal system
  • Pathways all start in the motor cortex and synpase at least once before proceeding to spinal cord
  • Older system (fish, birds, reptiles)
  • Posture, intiation and repetition of movement
  • Pyramidal develops slowly so this is what babies use
  • Psychotropic drugs have effects here leading to extrapyramidal symptoms
163
Q

Muscle Tone

what is it

upper and lower motor neurons

hypertonia

spasticity

hypotonicity

A
  • The resistance of a muscle to stretch. When a person tries to move a limb, there ar etwo parts: viscoelastic properties of the must and a-motorneuron activity
  • Upper motorneurons are actually interneurons descending to the “lower” a-motorneurons that inneravate
  • Hypertonia = too much tone. Increased motorneuron activity often caused by decreased inhibition of motorneurons or change in postsyn sensitivity by damage to upper motorneurons
  • Spasticity = hypertonicity after muscle stretch. A brief contraction. Any longer is a cramp
  • Hypotonicity = too little tone, flaccid. Can be caused by lower motorneuron damage, neuromuscular junction or muscle disease
164
Q

Upper motorneuron damage

A
  • Damage to upper motorneurons in pyramidal tract often caused by stroke, ALS etc
  • Consequence of flaccid paralysis (like spinal shock)
  • Followed by spastic hemiplegia or hemiparesis (paresis = weak)
  • Rapid movement of muscles causes greated increase in tone
  • Clasp knife reflex - pushing hard on joint => collapse, probably due to golgi tendon organ inhibition
  • Stretching may cause clonus = rapid, rhythmic contraction
  • Normal reflexes may increase or decrease
  • Babinski sign - upturb of big toe and fanning of toes on plantar stimulation (in babies bc their pyramidal tract isn’t full myelinated)
165
Q

afferents from skin vs muscle

A

afferents from the skin have many different connections - polysynaptic

monosynaptic are mainly from muscle receptors. These are the largest axons - fastest etc.

166
Q

Facilitation

A

Stimulate things seperately you get a small response. If you stimulate them together you get a response that is bigger than their individual responses

= facilitation

Subliminal fringe = a neuron that doesn’t fire when stimulated by A or B. It must be stimulated by both to fire.

The longer you wait after A firing to fire B, the smaller the facilitated sum reponse will be.

167
Q

Occlusion

A
  • Stimulate either strongly and you get a strong response
  • Innervate A and B together and you get a weaker response than the sum of their individual responses
  • sublinear summation is due to occlusion
168
Q

Spinal animal

A

Cut at spine

The higher you cut, the more function you get

169
Q

Spinal reflexes

A

bahviour produced entirely within the spinal cord

Two types of reflexes based on afferent input:

  1. Muscle receptor reflexes (muscle spindles, tendon organs)
  2. Cutaneous reflexes (skin pressure or pain)
170
Q

Spinal Shock

Spinal cord sextion outcomes

A
  • Following cut of spinal cord, no activity in spinal cord for about 2 weeks (flaccid paralysis), then reflexes resume and are often hyperactive.
  • probably due to loss of descending pathways and growth of new local synapses
  1. Plegia - paralysis
  2. Paresis - weakness
  3. Anaesthesia - loss of sensation
  4. Paresthesia - abnormal sensation (pins and needles)
171
Q

Spindles - explanation

A
  • Short, fusiform (spindle shaped), multinucleated, varied density
  • Some muscles so dense with them that their main job is sensation
  • Contribute to conscious sense of limb position (proprioception) and movement (kinesthesia)
172
Q

The spindle, muscle, motorneuron set up

A
  • a-motorneurons innervate muscle fibres
  • muscle fibres put out gamma motorneurons to spindles
  • Trail y-motorneuron ends go to chain spindles (nuclei in row)
  • Plate y-motorneuron ends go to bag spindles (nuclei in bag in middle)
  • Bag spindles have Ia afferents
  • Chain spindles have Ia afferents and II afferents
173
Q

Muscle spindle afferent firing (3)

A
  1. Increasing load = stretching muscle = increases firing
  2. Increasing a-motor neuron activity = contraction = less y firing
  3. Increasing y motorneuron activity stretches nuclei and increases firing
174
Q

Spindles.

Statis and dynamic

A
  • Ia (primary) are dynamic response. Respond to changing length
  • II (secondary) are static response. Respond to contant length
  • y - dynamic increases dynamic sensitivity (probably on bag spindles)
  • y-static increases static sensitivity (probably on chain spindles)
175
Q

Muscle spindles are responsible for the stretch reflex

A
  • Tendon jerk
  • Stretch muscle rapidly and it contracts
  • Stimulating the Ia afferent in a loop that stimulates the a motorneuron to contract
176
Q

reciprocal connections

A
  • Synergistic muscles work together
  • Antagonistic muscles work against each other
  • At the joint there are flexors and extensors. Two flexors are synergistic, one of each are antagonistic
  • Reciprocal innervation => antagonistic muscles to opposit things
    • Common to many reflexes/stretch reflex
177
Q

co-activation

A
  • activating a-motorneurons shortens the muscle and the spindles relax and reduce firing
  • CNS then turns up y firing so that spindles don’t relax and can still detect changes in length due to external load
178
Q

Servo controls of stretch reflex

A

They usd to think that only y-motor neurons did the stretch reflex, but then they realized that the circle of innervation means that the a-motorneurons are also helping which makes the function more stable.

179
Q

Golgi Tendon Organ Reflexes

mechanism

recent finding

A
  • Inhibit a-motorneuron activity at muscle as well as at neigbouring synergistic muscles.
  • Several muscle affected
  • Muscles are synergistic - acting together
  • Disynaptic reflex - two synapses (needs an interneuron because one neuron can do inhib and excit)
  • Extensor phase of walking had golgi tendon activity that excited motor neurons so reflex behaviour is plastic - can change during activities such as walking
180
Q

Flexion Reflex

A
  • In a spinal animal, noxious stim on distal limb leads to flexion of stimulated limb and extension of other limb
  • many muscles involved
  • Synergistic and antagonistic muscles
  • Man synapses - polysynaptic reflexes
  • Slow reflex
  • Temporal smmation - one stimulus does nothing, but several elecit a response
  • Spatial summation
  • Protective role and supportive role
181
Q

Positive supporting reaction

A

extensory thrust reflex

light pressure to spread toes leads to extension of limb

182
Q

Scratch reflex

A

Stimulate the skin on an animal’s side and they scartch same location

  • complex behaviour
  • Temporal summation
  • Spatial summation
  • Long latency
183
Q

Central pattern generators

A

Currently under research

rhythmic patterns that seem to have roots in the spinal cord

184
Q

Postural reflexes

A

balance against gravity requires information from (we need 2):

  1. Vestibular righting reflexes - signals from the vestibular system about the direction of gravity
  2. Optical righting reflexes - vision is enough if there is light
  3. Cutaneous righting reflexes - pressure on skin and proprioception from joints and muscles indicates gravity

Muscle and jiont receptors in neck provide reflex control of flexor and extensor muscles in the limbs to keep body upright. These reflexes are coordinated with the other righting reflexes.

185
Q

Romberg test

A

Subject stands with feet together and closes eyes

If their vestibular and proprioceptive inputs are comprimised the subject will sway or fall.

186
Q

neck reflexes

A

The neck muscles have many muscle spindles. Moving the head causes reflex limb movements aimes at keeping the head upright

187
Q

Postural reflexes depend on:

A
  • centres above the spinal cord
  • spinal animal doesn’t have posture
  • posture reflexes reappear if the cut is made higher
  • decebrate animal can right itself when placed on its back
188
Q

Primary motor cortex set up

A
  • Somatotopic representation of the body - motor homunculous
  • Stimulating a region on the map stimulates that region on the body. Relative to each other like on the body. Big regions for race and hand and tongue
  • Damage to part of the motor cortex leads to paralysis in the appropriate region - can recover if another part takes over its function
  • Complex connections bt diff motor areas that are also somatotopically organized
  • These areas are all involved in creating movements, but we don’t know how the movements are initiated
189
Q

Supplementary motor area

premotor area

cingulate motor area

A
  • Also involved in movement and somatotopically organized
  • Stimulating this areas also produces movements that tend to be more complex involving more muscles around a joint.
  • Premotor area also somatotopically organized; clear seperation of uppler/lower limbs; produces movement, but stronger stim is needed
  • Damage to supplementary and premotor areas leads to complex problems like apraxia
  • Cingulate motor area linked to the drive required to move and the reward acquired from moving.
190
Q

Apraxia

A

difficulty putting together complex movements like screwing in a lightbulb as a result of damage to the premotor cortex and the supplementary motor cortex

191
Q

basal ganglia

A
  • Complex connections between the cerebral cortex, basal ganglia, thalamus and spinal cord
  • Basal ganglia is part of an old system and is the only motor system in birds and lower vertebrates
  • Damage to the motor circuits involving basal ganglia cause some common movement disorders like Parkinsons:
    *
192
Q

Parkinson’s Disease

A
  • Akinesia/bradykinesia - no movement or slow movement
  • Rigidity - increased muscle contraction or tone
  • Tremor - oscillation of the limbs at 4-5 per second
  • caused by loss of cells in substantia nigra that release dopamine
  • L-DOPA a precursor of dopamine that can cros BBB has therapeutic value, but it decreases as the disease progresses
  • Surgical treatment either destroys over-active areas in brain permanently (pallidotomy) or inhibit them temporarily (deep brain stimulation)
    • Stimulation can sometimes bring wrong effect.
193
Q

Ballismus

Athetosis

Chorea

A

Basal ganglia movement disorders

  • Ballistic movements of limbs, often rotary, usually unilaterally so it is called hemiballismus.
  • Seems to be caused by damage (often strokes) to the subthalamic nuclei
  • Slow, writhing movements
  • Brisk, dancing movements
194
Q

Huntington’s disease

A
  • Best known chorea
  • Caused by excessive (40) repeats of CAG that lead to cell death in basal ganglia
  • Disease onset 30-50 yrs or earlier with more repeats
  • Causes chorea, later rigidity and akinesia (also dementia).
  • Might have been responsible for some of the salem witch trials
195
Q

Cerebellum inputs and outputs

A

The oldest part

  • Inputs:
    • Cutaneous (from spinal cord and brain stem)
    • Visual and auditory cells (via the cerebral cortex)
    • Vestibular (direct fand via the brain stem)
    • Muscle and joint receptors (from spinal cord)
  • Outputs: brainstem nuclei (nothing goes directly to spinal cord)
196
Q

Cerebellum

contralateral or ipsilateral?

flocculonodular lobe

A
  • Connections are generally ipsilateral (in contrast to cerebrum). many pathways cross midline twice)
  • Flocculondodular lobe
    • Closely associated w vestibular system
    • Mainly involved in controlling eye movements, head position, posture relative to gravity
    • Damage causes difficulty with eye and head position and balance. Patients stand with legs far apart to improve balance
    • They can still control their head eyes and limbs, just can’t correct them based on vestibular input
197
Q

Cerebellum - spinocerebellum

A
  • Central region is older - spinocerebellum
    • Recieves input from afferents of spinal cord (tracts), particularly from muscle and joint receptors
    • Somatotopically organized sensory maps of body surface - trunk at centre, outwards toward distal limbs
    • modulates descending motor pathways in brain stem and cerebral cortex
    • helps control movements by anticipation
198
Q

Lateral regions of the cerebellum

A
  • much larger in man than in apes
  • Call the cerebrocerebellum or pontocerebellum
  • recieves a wide range of sensory information (including vision and hearing) via cerebrum
  • Functions are still being discovered and include planning and adjusting movement based on sensory information, cognitive tasks useful for movements, and learning motor tasks
199
Q

Disorder caused by cerebellar damage

A
  • Hypotonia - reduction of muscle tone, reduced resistance to passive movement, ascillation after the stretch reflex
  • Ataxia - lack of coordination, Delay in starting a movement
  • Dysmetria (error in size of movement), errors in rate and regularity of repeated movement
  • Movement decomposition
  • Intention tremor - oscillation that increases with movement (in contrast to resting tremor in Parkinson’s)
  • Loss of plasticity in controlling movements, such as learning to throw darts while wearing prism glasses
  • Not paralysis!
200
Q

Ataxia and Tremors

A
  • Ataxia = range in diseases causing bad movement coordination.
    • Commonly caused by cerebellar damage (malnutrition, virus, genetic mutation, stroke, alcohol, drugs)
  • Postural tremor = small oscillation, particularly when extending hands is common. Can be caused by genetic factors, anxiety, drug or alcohol withdrawal
201
Q

eyes

A
  • Superior/inferior rectus move eyes up and down
  • Lateral/medial rectus move eyes sideways
  • Superior/inferior oblique roll eyes around visual axis
  • Occulomotor nerve drives all except Superior oblique and Lateral rectus
  • Saccades = quick, darting, normal eye movements
    • Superior colliculou (top of midbrain) has a topographic map of visual world, invovles front eye fields and posterior parietal lobe
  • Tracking movements slower and smooth, follow an object

PHYL 2041 (2 decks)

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