KNES 251 Midterm #2 (Lectures 11-23)

what is meant by the term perturbation?

disruptions that cause us to stress

what is the function of interneurons?

turn excitatory stimulus to inhibitory stimulus

what is a dermatome?

area of skin supplied by neurons that all arise from a specific spinal segment

what is meant by the term ipsilateral?

different structures on the same side

what is gaba?

inhibitory neurotransmitter

what is the function of gaba?

opens and closes gates, usually rushes Cl in

what is glutamate?

excitatory neurotransmitter (not always)

what is glutamate usually associated with?

Na rushing in

what is meant by excitatory?

increase fire and rate of neuron

what is meant by inhibitory?

decreases fire and rate of receiving neuron

What is a motor unit?

Single motor neuron and all of the muscle fibres it stimulates

What’s a motor pool?

All of the motor units stimulating a given muscle

What does unfused tetanus show us?

Build up of Ca close to the max

What does fused tetanus show us?

maximum build of Ca

Of the motor units learned, which is the fastest?

FF motor units, FG muscle fibres

Of the motor units learned, which is the slowest?

S type motor units, SO muscle fibres

When do fast twitch muscle fibres fatigue more?

When stimulated for an extended period of time

Which of the muscle fibres lasts longest?

Slow

What is proprioception?

Brains understating of where body is in space

What is kinesthesia?

Brains understanding of movement

What is mechanotransduction?

mechanical energy is converted into a voltage change for action potential in sensory afferent neurons

What is a cutaneous receptive field?

Region of skin that is capable of evoking action potentials in cutaneous afferent

What is glabrous skin?

Non-hairy skin

What cells are slow adapting type 1?

Merkel cell

What cutaneous receptors are fast adapting type 1?

Meissner corpuscles

What is meant by type 1 cutaneous receptors?

Superficial receptors

What is meant by type 2 cutaneous receptors?

Deep receptors

What cutaneous receptors are slow adapting type 2?

Ruffini endings

What cutaneous receptors are fast adapting type 2?

Pacinian corpuscles

List the cutaneous receptors in order of most sensitive to indentation to least.

Pacinian, meisnner’s, merkel, Ruffini endings

What are the characteristics of SA1 Receptors?

Irregular discharge when stimulated, highly sensitive to edges and curvature, moderately low threshold, uneven spaces between AP

What are the characteristics of SA2 Receptors?

Regular discharge when stimulated, very sensitive to skin stretch, high threshold to indentation, not in non-human primates

What are the characteristics of FA1 Receptors?

Codes for velocity of skin indentation and motion across skin, 40% of innervation in hand, sensitive to low frequency vibrations, low threshold

What are the characteristics of Fast adapting receptors in terms of action potentials?

Fire action potentials during change in indentation, stop when holding indentation

What are the characteristics of slow adapting receptors in terms of action potentials?

When stimulated they continue firing action potentials the whole time and don’t stop till indentation stops

What are the characteristics of FA2 Receptors?

Codes for acceleration, change in indentation rate, picks up high frequencies, extremely low threshold

What is the innervation ratio of type 1 cutaneous receptors?

More than one attached to axon, multiple hot spots

What is the innervation ratio of type 2 cutaneous receptors?

Only 1 attached to its axon, 1 hotspot

Where are type 1 cutaneous receptors more dense?

Finger tips

Where are type 2 cutaneous receptors more dense?

Evenly distributed through hand

Where are vibration sensitive receptors found?

Skin, joint capsules, digestive system

what are nociceptors?

pain/chemo receptors that measure inflammation and chemicals to detect damage

what are thermally gated receptors (temperature receptors)? How do they open?

respond to heat, heat causes protein channels to break down and ions flow in

what is the relation between thermoreceptors and nociceptors?

thermoreceptors fire action potentials then asymptote, as they asymptote nociceptors begin firing to alert about tissue damage

what is capsaicin? What does it do?

lipid based molecule that enters cell directly and artificially initiates a heat response

what causes us to experience the feeling of spice?

capsaicin

why is capsaicin able to enter the cell directly?

because it is lipid based

what does GTO stand for?

golgi tendon organ

where are ruffini endings and GTO’s found, respectively?

epidermal tissue, muscle

What is the Ib afferent?

sensory ending of the GTO that weaves between collagen strands

what happens to the Ib afferent when collagen strands are pulled?

they come together and crush Ib afferent nerve endings opening mechanically gated receptors allowing ions in

do all muscle fibres connect to the GTO?

no

what GTO’s innervated by?

Ib afferents

what do GTO’s measure?

active force production and stress caused by it

What are Ia afferent?

primary afferent endings in muscle spindles

what is meant by type II ending?

secondary endings in the muscle spindles

what does the GTO firing rate closely follow?

EMG

what are the two things joint receptors can measure?

pressure or changes at extreme ends of range of motion

what is the main characteristic of joint receptors and how they measure?

they cannot different between flexion, extension, and pressure

what are joint receptors useful for?

knowing when we’re at the end of range of motion

are joint receptors useful for proprioception and kinesthesia?

no

which afferent axon types have a high conduction velocity?

Ia, Ib, II

which receptor types have a high conduction velocity?

muscle spindles and GTO

what receptor types have a slow conduction velocity?

merkel, meissner, pacinian, ruffini endings and joint receptors

what did sherrington publish?

Integrative action of the nervous system

what did “The integrative action of the nervous system” observe?

spinal reflexes

who coined the terms neuron and synapse?

Charles Sherrington

Before Sherrington’s work what were reflexes thought to be a result of?

isolated activity within a reflex arc

after Sherrington’s work what were reflexes thought to be a result of?

extensive integration of synaptic inputs within the spinal cord

what is meant by the term disynaptic connectivity?

two synapses connect to act on final neuron

what is meant by monosynaptic connectivity?

one synapse acts on final neuron

what is meant by polysynaptic connectivity?

more than 2 synapses act on final neuron

what are convergent pathways?

many sensory organs feeding up to the brain, many to one

what are divergent pathways?

travelling through multiple pathways, one to many

what is feedback excitation?

neuron feeds back into itself and causes excitation, positive feedback

what is feedback inhibition?

neuron feeds back into itself but causes inhibition, negative feedback

what is an example of feedback inhibition?

renshaw cell

what shape represents excitatory stimuli?

triangle

what shape represents inhibitory stimuli?

circle

how many types of neurotransmitters does one neuron produce?

one that can be either excitatory or inhibitory

what is the basic anatomy/path of a reflex?

stimulus sends action potential to sensory neuron in the spinal cord which directly synapses to alpha motor neurons causing contraction

what type of connectivity is a basic reflex?

monosynaptic

what is divergence?

single muscle spindle connects to a large number of neurons in a motor pool or the whole pool

explain the step 1 of a basic muscle stretch reflex

hammer tap stretches tendon stretching sensory receptors in extensor muscle

explain the step 2A of a muscle stretch reflex

sensory neuron synapses with and excites motor neuron in spinal cord

explain the step 2B of a muscle stretch reflex

sensory neuron also excites spinal interneuron

explain the step 2C of a muscle stretch reflex

interneuron synapses inhibiting motor neuron to flexor muscles

explain the step 3A of a muscle stretch reflex

motor neuron conducts action potential to synapses on extensor muscle fibres causing it to contract

explain the step 3B of a muscle stretch reflex

flexor muscles relax because activity is inhibited

explain the step 4 of a muscle stretch reflex

limb extends

what does the gaba neurotransmitter do in a muscle stretch reflex?

opens ligand gated Chlorine channels reducing firing rate and stopping action potentials therefore reducing force

what is a synergist muscle?

muscle that supports the direction of movement of the agonist muscle

what is a tonic excitatory input?

another sensory input or descending input that can increase or decrease stimulation

what is the purpose of faciliatory inputs?

provides extra stimulation to reach threshold when the tap isn’t enough

what are cutaneous withdrawal reflexes?

activates appropriate muscles to adaptively and rapidly withdraw the correct limb

when does the cutaneous withdrawal reflex occur?

when the skin is stimulated by a sudden painful event on the skin’s surface

what type of receptor is associated with cutaneous withdrawal reflexes?

nociceptors

what is gastrocnemius RF? What movement does it allow for?

plantar flexion

what is tibialis anterior RF?What movement does it allow for?

dorsal flexion

What is the role of muscle spindles, GTO, and cutaneous receptors in cutaneous withdrawal reflex

informs the spinal cord about your position and what limb/muscle to retract