KNES 351 Midterm Review 1

What is the main source of energy for the brain

glucose

The brain is subdivided into 4 areas:

cerebrum, diencephalon, brainstem, cerebellum

• has 2 hemispheres: cerebral cortex and white matter + corpus callosum

• 3 deep lying neural structures: basal ganglia, amygdala and hippocampus

• where integration occurs

• subdivision of the brain

cerebrum

largest part of the brain that is responsible for perceptual, motor and cognitive functions

cerebral hemispheres

areas of the brain where higher level processing occurs

grey matter

areas of the brain where lower level processing occurs

white matter

• deep lying neural structure of the cerebrum

• movement and motor learning

basal ganglia

• deep lying neural structure of the cerebrum

• expression of emotions

amygdala

• deep lying neural structure of the cerebrum

• memory

hippocampus

sensory information leading to memory is caused by

place cells in the hippocampus

• composed of 4 lobes: frontal, parietal, occipital and temporal

• subdivision of the brain

cerebral cortex

• a lobe in the cerebral cortex

• motor planning, organizing behaviour, decision making and working memory

• where higher functions occur

frontal lobe

• a lobe in the cerebral cortex

• sensory guidance, multisensory integration, spatial awareness, vestibular cues and visual cues

parietal lobe

• a lobe in the cerebral cortex

• early visual processing

occipital lobe

• a lobe in the cerebral cortex

• vision, hearing, memory and language

temporal lobe

• part of the cerebrum, in the white matter

• bundle of axons connecting both hemispheres to allow communication between them

corpus callosum

• subdivision of the brain

• consists of the thalamus and hypothalmus

diencephalon

• part of the diencephalon

• essential link for sensory pathways from the periphery to the brain

• interconnects cerebellum and basal ganglia, and some of the cerebral cortex for cognition and movement

• information comes in and goes out of this structure

thalamus

why are olfactory receptors an exception for the requirement of the thalamus to deliver its messages to the brain?

olfactory receptors come off the cranial nerves and can travel on its own

• part of the diencephalon

• essential for neuroendocrine system as it aids in growth, eating and drinking

• aids in motivation and arousal

hypothalamus

how does the hypothalamus aid in motivation and arousal

it causes the release of neurotransmitters or hormones like dopamine and norepinephrine, etc, which chemically and electrically stimulates the brain for motivation and arousal

• subdivision of the brain

• responsible for: posture, balance, coordinating movements, error based learning, receiving somatosensory information from the spinal cord, receives copies of motor commands from cerebral cortex to aid in correcting movements

• density of neurons is higher here - because of higher processing functions

• basic integrations occur here

• works with premotor and motor cortex for reflexes

cerebellum

• brain structure that consists of the midbrain, pons and medulla

• reflexes slow down as you go up this structure due to slow diffusion

brain stem

• structure of the brain stem

• links cerebellum, basal ganglia and cerebral cortex

• involved in hearing and oculomotor control

midbrain

• structure of the brain stem

• responsible for sleep, respiration and taste

pons

• structure of the brain stem

• relays information about sensation and movement from cerebral cortex to the cerebellum

• belly of the pons

pontine nucleus

• structure of the brain stem

• regulates blood pressure and respiration, early pathways of taste, hearing, balance, head control, neck and limb muscles

medulla

• largest and simplest component of the CNS

• Receives sensory information from skin, muscles and joints

• Has motor neurons needed for voluntary movements

• Performs basic integration of somatosensory feedback and motor responses/reflexes

• Composed of 31 pairs of sensory and motor nerves

• Sensory division carries somatosensory, touch, pain, temperature and information from visceral sensory organs

• where final common pathway occurs

spinal cord

electrical impulses from body to brain

the affect

afferent tract

electrical impulses from brain to body

the effect

efferent tract

sensory into motor activity

afferent to efferent

sensorimotor integration

• part of the spinal cord

• sensory neurons from muscles and skin

dorsal horn

• part of the spinal cord

• cell bodies and axons of motor neurons that influence muscle firing patterns

Ventral Horn

• part of the spinal cord

• interneurons that influence firing patters of sensory and motor neurons

intermediate zones

more sensory and motor fibres innervating the upper limbs causing a bigger cervical spine segment

cervical enlargement

more sensory and motor fibres innervating the lower limbs causing a bigger lumbar spine segment

lumbar enlargement

why do lumbar and cervical enlargements in the spine occur?

because of the upper and lower extremities; the more muscles we have to control, the more sensory information we process and integrate, the more sensory and motor fibres is required which leads to more control and dexterity for these extremities

receptors -> information -> spinal cord and brain (afferent nerves)

sensory nerves

spinal cord and brain -> motor commands -> skeletal muscles (efferent nerves)

motor nerves

modified endings of sensory nerves; the first step in processing our senses (such as touch and proprioception)

receptors

what are the main sensory organs for proprioception

muscle spindles and GTOs

which division of the PNS controls voluntary movements

Somatic

• anatomical axis in the spinal cord and brain stem

• superior - to the top of the head

rostral

• anatomical axis in the spinal cord and brain stem

• inferior - to the tail bone

caudal

• anatomical axis in the spinal cord and brain stem

• anterior

ventral

• anatomical axis in the spinal cord and brain stem

• posterior

dorsal

• anatomical axis of the brain

• anterior - to the nose

rostral

• anatomical axis of the brain

• posterior - to the back of the head

caudal

• anatomical axis of the brain

• inferior

ventral

• anatomical axis of the brain

• superior

dorsal

non invasive tool to monitor and perturb movements to examine sensory and motor functions as participant moves their arm in the horizontal plane

• torque motors perturb movements at the shoulder/elbow

• movements are only in 2D

• allows us to: monitor and record arm movements, quantify how the NS responds to unexpected perturbations and quantify sensory and motor deficits in clinical populations

robotics

in robotics, what does a healthy subject’s relative arm movement look like?

the hand path is smooth and there is quick acceleration and deceleration in hand speed profiles

in robotics, how does the nervous system respond to perturbations?

it corrects the movements. when we are reaching for a small object which has a single point of destination, there are lots of correction shown. when we are reaching for a larger object, which has multiple points of destination, there are less corrections shown.

therefore, when a subject reaches for a larger target, perturbation and correction work together as there is less need for correction.

low accuracy demands means less correction

what are the pros of robotics? cons?

pros:

• easy to use, non invasive

• useful for quantifying and perturbating body motion

• easy to use with other tools

• useful to manipulate body motion to see how NS controls movements

cons

• expensive

• long set up

• unable to replicate 3D movement

• invasive technique recording the activity of peripheral neurons

• time consuming, but the only way to get single cell recordings

• Pioneered by KE Hagbarth and A Valbo

microneurography

how does a microneurography work?

• an electrode is put into the peripheral sensory neuron, guided by sound and signal

• a small probe is used to apply prolonged forces to determine which receptor is being recorded

• a rotating drum device is used to stimulate the skin over the finger, which calibrates to measure the position of the finger and receptive field

• the rotating drum has series of lines, contours and edges with different orientations

axon of sensory neuron and its myelin sheath

nerve fibre

bundle of individual nerve fibres

fascicle

connective tissue surrounding nerve fibres

endoneurium

connective tissue surrounding fascicles

perineurium

connective tissue surrounding nerves

epineurium

collection of all structures – connective tissue and blood vessels

nerve

what are the pros and cons of microneurography?

pros

• specific recordings

• useful for understanding periphery sensory feedback

• can be used with other tools

• useful for quantifying response properties of sensory receptors and firing patterns of motor neurons

cons

• time consuming

• invasive

• restricted small movements/simple tasks

invasive technique to record the activity of cortical neurons

electrophysiological recordings

what is the strength of a neuron’s response dependent on?

the orientation and spatial location of the stimulus on its receptive field

• for visualizing action potentials

• each line is a different trial, each vertical tick is when a neuron fired an AP

• time based

raster plots

• for visualizing firing rate over time

• averages individual trials of raster plots

post stimulus time histograms (PSTHs)

• non invasive technique to record body motion during motor tasks

• Cameras are used to record the motion of the retroreflective markers

• Used to quantify and understand pathological gait

• Useful for quantifying body motion and the underlying forces

motion capture

how does motion capture work?

• Cameras emit light in the infrared spectrum

• Light is reflected by retroreflective markers

• Cameras record at high frame rates

• Force plates record forces that occur while moving and interacting with the environment

when neurons fire when a stimulus is in their receptive field, but are otherwise silent

centre surround inhibition

what are the pros and cons of motion capture?

pros

• Easy to use and non invasive

• Useful for describing body motion and underlying forces

• Can integrate with other tools – with EMG, we can determine if a gait is a motor, structural or sensory issue

cons

• Difficult to tell whether deficits are caused by sensory or motion function

• Difficult to manipulate/perturb body motion

connective tissue surrounding muscle fibres

endomysium

connective tissue surrounding muscle fascicles

perimysium

connective tissue surrounding muscle

epimysium

bundle of muscle fibre (cells)

muscle fascicle

composed of all structures – connective tissue and blood vessels

skeletal muscle

records activity of skeletal muscle during motor tasks

2 types: surface and indwelling

electromyography (EMG)

non invasive technique to record the activity of skeletal muscle at the surface of the skin

surface EMG

how does surface EMG work?

• Uses recording electrodes and reference ground electrodes

• Ground electrodes get rid of noise

• Electrodes span muscle fibres in 2 different motor units

• These motor units will show separate firing patterns that differ in amplitude and frequency/timing

• The surface EMG records the summated activity of these motor units – firing patterns of both motor units are combined in the surface EMG recording

pros and cons of surface EMG

pros

• easy to use

• non invasive

cons

• can only record superficial muscles

• signal quality related to depth of subcutaneous tissue – fat insulates electrical activity, so the fatter the tissue, the lower signal quality

• suitable for large muscles – if small muscles are involved, there will be lots of cross talk between surrounding muscles

invasive technique to record the activity of individual motor units in a skeletal muscle

indwelling EMG

how does indwelling EMG work

• an electrode is inserted into a skeletal muscle and a reference/ground electrode

• ground electrode gets rid of noise

• typically used in medical diagnostics

• the needle electrode records from a single muscle fibre

• this technique allows recording from individual motor units

• results can show that muscles are relatively quiet at rest, while increased force generation produces increases in frequency of action potentials

pros and cons of indwelling EMG

pros

• used to record deep muscles

• potential to record single motor unit action potentials

• useful for medical diagnostics

cons

• amount of movement is restricted

• invasive

invasive technique to record the activity of individual motor units in skeletal muscle

fine wire EMG

how does fine wire emg work?

• uses a needle inserted into skeletal muscle and a reference/ground electrode

• this is then retracted, leaving the wired in the muscle

• ground electrode gets rid of noise

• used to record deep muscles in active motor tasks

pros and cons of fine wire emg

pros

• ·      used to record deep lying muscles

• ·      smaller recording surface providing better resolution, can record from small and adjacent muscles

• ·      restricts motion less compared to a needle EMG

cons

• ·      invasive

• ·      poorer resolution than needle EMG as it has a larger pick up volume

non invasive technique that uses magnetic fields to image the anatomy of the brain

• safely and routinely image tissue with water content

• water content varies in different types of tissue, influencing MRI signal and images

• the best tool for imaging and quantifying brain structure

structural MRI

what is a structural MRIs resolution in voxels

1-2

what is the strength of structural MRI measured by and what are the strength of most scanners?

Teslas. 3T

basic unit of measurements for MRIs, it varies on the strength of the magnet anf scan sequence

Voxel/Volumetric Pixel

how does a structural MRI work?

·      The human body consists of most water, consisting of hydrogen and oxygen atoms – hydrogen atoms are protons

·      The MRI places the body in a strong magnetic field

·      Normally, without a magnetic field, the proton spins are randomly aligned

·      In a magnetic field, the protons are realigned as they spin in up or down states – The positive pole of the proton is either in the up or down direction

·      The introduction of a magnetic field creates a precession of the protons – Precession: nuclear spin of the proton on a skew axis around the magnetic field

·      When introducing a magnetic field and radio waves (RF pulses), all the protons are aligned in a down spin state – When protons are in a down spin state, that is their highest energy

·      When the radio waves are removed, some protons go to the up state to release energy and bring everything back to normal

·      The MRI is measured after RF pulses 

pros and cons of MRI

pros

·      Non invasive

·      Visualization of brain and structure/anatomy

·      Good spatial resolution

·      Helps with understanding the relationship between brain structure and behaviour function

cons

·      Static snapshots of the brain anatomy, not function

·      Expensive

non invasive technique using magnetic fields to measure brain activity during functional tasks

• does not have a great measure on timing

• measures the changes in blood flow over time, demonstrating activity maps

fMRI (functional)

how does an fMRI work?

·      Measures blood oxygenation level dependent signals (BOLD)

·      If there is an increase in brain activity, this increases regional blood blow, increasing oxygen in the brain

·      Deoxygenated hemoglobin is more magnetic than oxygenated hemoglobin, resulting in different MR signals in the active and inactive parts of the brain

pros and cons of fMRI

pros

·      Non invasive

·      Allows quantification of brain activity in awake and behaving states

·      Good spatial resolution

cons

·      Poor temporal resolution

·      Can only do small movements

·      Expensive

what kind of feedback is needed for skilled voluntary motor actions?

tactile feedback

sense organ responding to mechanical stimuli – stretch, pressure, vibration

cutaneous mechanoreceptor

what are the 4 types of mechanoreceptors in glabrous skin?

• meissner

• merkel

• ruffini

• pacinian