Peters Physiology Flashcards by Rafi Ahmed

List the main components of neuronal structure

Dendrites
Soma (cell body)
Axon hillock + initial segment
Axon
Synapse

How well did you know this?

Not at all

Perfectly

What is the main function of dendrites?

Receive neuronal inputs and convey graded signals towards the soma

How well did you know this?

Not at all

Perfectly

The soma of the neurone is the metabolic centre. List the structures it contains

Nucleus
Ribosomes
Mitochondria
Endoplasmic reticulum
Nissl substance

How well did you know this?

Not at all

Perfectly

What is Nissl substance?

Rough endoplasmic reticulum (ER with ribosomes)

How well did you know this?

Not at all

Perfectly

Which part of the neurone is the site of initiation of an action potential?

Axon hillock + initial segment

How well did you know this?

Not at all

Perfectly

What is the main function of an axon?

Conducts action potentials to other neurones or cells

How well did you know this?

Not at all

Perfectly

Electrical info/material can travel from the soma to presynaptic terminal (anterograde) and vice versa (retrograde). True/False?

True

Retrograde travel can welcome infection (e.g. polio)

How well did you know this?

Not at all

Perfectly

What is a synapse?

Point of chemical communication between 2 neurones

How well did you know this?

Not at all

Perfectly

List the 4 main types of neurone

Unipolar
Pseudounipolar
Bipolar
Multipolar

How well did you know this?

Not at all

Perfectly

Describe a unipolar neurone and give an example of where it may be found

No dendrite; soma only gives off axon

e.g. peripheral autonomic neurone

How well did you know this?

Not at all

Perfectly

Describe a pseudounipolar neurone and give an example of where it may be found

Short axon bifurcates into soma and central axon

e.g. dorsal root ganglion neurone

How well did you know this?

Not at all

Perfectly

Describe a bipolar neurone and give an example of where it may be found

Dendrite + soma + axon

e.g. retinal bipolar neurone

How well did you know this?

Not at all

Perfectly

Describe a multipolar neurone and give an example of where it may be found

3 or more neurites attached to soma

e.g. lower motor neurone

How well did you know this?

Not at all

Perfectly

What is the difference between Golgi type I and type II axons?

Golgi type I = long axon

Golgi type II = short axon

How well did you know this?

Not at all

Perfectly

Which channels open in neurones when membrane polarity reaches threshold (-60mV) to cause the upstroke of the action potential?

Na channels

How well did you know this?

Not at all

Perfectly

Which 2 factors determine the distance over which electrical current spreads in a neurone?

Membrane resistance

Axoplasm resistance

How well did you know this?

Not at all

Perfectly

Increasing membrane/axoplasm resistance increases the distance travelled by electrical current

Increasing membrane resistance increases the distance travelled by electrical current
(less current leaks out)

How well did you know this?

Not at all

Perfectly

A narrow axon provides high/low resistance to conduction velocity

A narrow axon provides high resistance to conduction velocity

How well did you know this?

Not at all

Perfectly

Which insulating material can help increase conduction velocity in neurones by reducing current leak?

Myelin

How well did you know this?

Not at all

Perfectly

Which cells produce myelin for neurones?

Schwann cells in PNS

Oligodendrocytes in CNS

How well did you know this?

Not at all

Perfectly

Many schwann cells and oligodendrocytes surround axons. True/False?

False

Many schwann cells surround one axon but usually only one oligodendrocyte surrounds many axons

How well did you know this?

Not at all

Perfectly

Which region does the action potential “jump” from to get between neurones in myelinated axons?

Nodes of Ranvier

How well did you know this?

Not at all

Perfectly

What are the 3 main morphological classifications of a synapse?

Axodendritic (most common)
Axosomatic
Axoaxonic (least common)

How well did you know this?

Not at all

Perfectly

Synapses can be excitatory or inhibitory. Respectfully, what are the main transmitters involved for each?

Glutamate for excitatory CNS

GABA or glycine for inhibitory CNS

How well did you know this?

Not at all

Perfectly

The excitatory postsynaptic potential (epsp) is depolarizing and the inhibitory postsynaptic potential (ipsp) is hyperpolarizing. True/False?

True

If an epsp is too weak to cause synapse, how can excitation be achieved?

Converge multiple epsp's to cause net excitation (synaptic summation)

List the sensory modalities that come under the somatosensory system

``` Touch Proprioception Temperature Pain Itch ```

What happens to the energy generated by a stimulus at a sensory nerve cell terminal?

Transduced into electrical activity which creates depolarizing (generator) potential which, if strong enough, can trigger action potential

Which receptors aid with proprioception?

Joint and muscle mechnoreceptors

Adaptation determines the firing rate of sensory neurones in response to changing stimuli. Describe the slow-adapting response

Continuous information whilst nerve being stimulated | Gives info about position, stretch, force

Adaptation determines the firing rate of sensory neurones in response to changing stimuli. Describe the rapid-adapting response

Detects change in stimulus strength and rate of movement

Adaptation determines the firing rate of sensory neurones in response to changing stimuli. Describe the very-rapid-adapting response

Responds only to very fast movement (vibration)

Primary sensory afferent fibres are grouped I-IV or Aα, Aβ, Aδ, C. Order the groups from thickest-least thickest myelination, i.e. from fastest conduction velocity to slow

Group I, group II, group III, group IV AKA Aα, Aβ, Aδ, C

What is meant by the receptive field of a sensory neurone?

The region which, when stimulated, produces a response in that neurone

Which type of sensory receptor do Aα primary sensory afferents conduct?

Proprioceptors

Which type of sensory receptor do Aβ primary sensory afferents conduct?

Mechanoreceptors of skin

Which type of sensory receptor do Aδ primary sensory afferents conduct?

Nociceptors | Thermoreceptors

Which type of sensory receptor do C primary sensory afferents conduct?

Nociceptors Thermoreceptors Itch receptors

What do free nerve endings in skin help sense?

Pain | Temperature

What do Meissner's corpuscles in skin help sense?

Touch/vibration

What do Merkel's discs in skin help sense?

Touch

What do Ruffini endings in skin help sense?

Pressure

What do Pacinian corpuscles in skin help sense?

Pressure

Two point discrimination is being able to distinguish 2 stimuli separately without overlap. Which corpuscles have higher 2 point discrimination - Pacinian or Meissner's?

Meissner's corpuscles | less overlap of receptive fields

Meissner's corpuscles, Ruffini endings, Merkel discs, Pacinian corpuscles and long hair are all supplied by which sensory fibre type?

Aβ

Short hair is supplied by which sensory fibre type?

Aδ

What is a dermatome?

Area of skin innervated by left and right dorsal roots of a spinal nerve

The spinal cord consists of grey and white matter. Ascending the cord, the proportion of which matter increases?

Proportion of white matter increases as you ascend the spinal cord

Nociceptors (fibre class ___) terminate at laminae _ and _

Nociceptors (fibre class Aδ/C) terminate at laminae I and II

Low-threshold mechanoreceptors (fibre class ___) terminate between laminae _ and _

Low-threshold mechanoreceptors (fibre class Aβ) terminate between laminae III and VI

Proprioceptors (fibre class ___) terminate between laminae _ and _

Proprioceptors (fibre class Aα) terminate between laminae VII and IX

What are the 2 main tracts of the somatic sensory pathway?

Dorsal column medial leminscal pathway | Spinothalamic tract

The dorsal column of the somatosensory pathway conveys Aα/Aβ sensory fibre info (proprioception, touch). Where does the 1' neurone synapse in the spinal cord?

All fibres synapse in brainstem and crossover to opposite side onto 2' neurone

The spinothalamic tract of the somatosensory pathway conveys Aδ/C sensory fibre info (pain, temperature). Where does the 1' neurone synapse in the spinal cord?

Synapses shortly after entry into spinal cord; fibres crossover to opposite side at different points along the cord in 2' neurone

Where do the 2' neurones in the somatosensory tracts synapse?

Thalamus

Dorsal columns of the somatosensory pathway consist of which 2 tracts?

Fasciculus gracilis | Fasciculus cuneatus

Sensory input from which spinal regions travels in fasciculus gracilis?

From T6 and below (legs and lower trunk)

Sensory input from which spinal regions travel in fasciculus cuneatus?

From T6 and above (arms and upper trunk)

What is meant by contrast enhancement in the sensory pathway?

As information is conveyed between neurones, differences in activity between adjacent neurones are amplified

Which part of the brain receives the sensory information from the somatosensory pathway (dorsal column medial lemniscus pathway + spinothalamic tract)?

Post-central gyrus (primary somatosensory cortex) via the thalamus

What is stereognosis?

Ability to recognise an object by feeling it

Which cranial nerve provides sensory innervation to the face?

Trigeminal nerve | trigeminothalamic pathway

Outline (roughly) the sensory facial areas innervated by divisions of the trigeminal nerve

Ophthalmic: nose upwards Maxillary: ala, cheeks, lateral forehead, upper lip Mandibulary: lower lip, jaw, earline

Once central terminals of the trigeminal synapse, in what do they travel to the thalamus?

Trigeminal lemniscus (runs parallel to dorsal column median lemniscus)

Where is the somatosensory cortex located?

In the post central gyrus of the parietal cortex, posterior to central sulcus

What is the name of the areas contained within the somatosensory cortex?

Broadmann areas (1, 2, 3a, 3b)

The somatosensory cortex receives input from the ventral posterolateral thalamus. What proportion of input goes to each Broadmann area?

70% to Broadmann 3a + 3b | 30% to Broadmann 1 + 2

What input and information does Broadmann area 3a receive?

Proprioceptors (muscle spindles) | Info: body position

What input and information does Broadmann area 3b receive?

Cutaneous receptors, rapid-adapting receptors, BA 3a | Info: touch (texture, shape, size)

What input and information does Broadmann area 1 receive?

Cutaneous receptors, mechanoreceptors, BA 3b | Info: texture discrimination

What input and information does Broadmann area 2 receive?

Joint afferents, Golgi tendons, BA 3a, BA 3b | Info: object perception (stereognosis)

What is the name of the somatotropic map of the body surface present on the somatosensory cortex? What does it represent?

Sensory homunculus | Reveals relative sensory cortical power devoted to each body part

There are 6 cell layers (I-VI) to the somatosensory cortex - upon which layer do thalamic inputs usually terminate?

Layer IV neurones

Give an explanation for phantom pain experienced following amputation

Cortical remapping involves the area formerly represented by the amputated body part being stimulated by adjacent body part as per the somatotropic map (homunculus)

What is a 'motor neurone pool'?

Collection of alpha-motor neurones that innervate a single muscle

What is the myotatic reflex?

When a skeletal muscle is pulled, a reverse (protective) force in the muscle spindle pulls it back

What is contained within a muscle spindle?

Intrafusal muscle fibre Ia sensory afferents Gamma-motor neurone efferents

What is the benefit of stimulating intrafusal and extrafusal fibres (alpha and gamma -motor neurones) at the same time?

Prevents the muscle spindle from going slack

What is the function of Golgi tendon organs?

Monitor changes in muscle tension to protect from overload

Where are Golgi tendon organs located?

At the junction between tendon and muscle

Group Ib afferents innervate Golgi tendon organs and synapse with alpha-motor neurones via inhibitory interneurons of the contracted muscle. What is the ultimate reflex that occurs?

Reverse myotatic reflex that maintains muscle tension within safe limits

Inhibitory interneurons mediate which reflexes in flexion/extension of muscle?

Reverse myotatic response | Reciprocal inhibition

The myotatic reflex and reciprocal inhibition occur to produce desired movement. Outline the process using quadriceps + hamstring muscle

Quadriceps contraction requires hamstring relaxation - Ia fibre supplying the alpha-motor neurone of the quadriceps inhibits the alpha-motor neurone of the hamstring VIA an inhibitory interneuron

Excitatory interneurons mediate which reflexes in flexion/extension of muscle?

Stretch reflex | Crossed extensor reflex

What is the main lateral pathway for descending spinal tracts?

Corticospinal tract

Nociceptors are primary afferent neurones comprising __ fibres and __ fibres

Nociceptors are primary afferent neurones comprising Aδ fibres and C fibres

Which fibres - Aδ or C - mediate first/fast pain?

Aδ fibres

Which fibres - Aδ or C - mediate second/slow pain?

C fibres