PNB Practical #2

where does stimulus for muscle movement travel (5 steps)

- stimulus in cerebral cortex

- upper motor neuron

- action potential travels down corticospinal tract

- lower motor neuron

- skeletal muscle

on average 1 lower motor neurons innervates ___ skeletal muscle fibers

150

eye movements: 1 lower motor neuron innervates ____ muscle fibers

10-15

biceps brachii: 1 lower motor neuron innervates up to ____ muscle fibers

2000

if a single nerve fiber is stimulated, it will always give ...

a maximal response

3 steps of power stroke

- Ca2+ release from SR and binds to troponin

- tropomyosin shifts, exposing the myosin binding sites

- ATP is hydrolyzed triggering the contraction

what triggers the calcium release from SR

action potential

What is the I band of the sarcomere

contains only thin filaments (actin)

what is the H zone of the sarcomere

Contains only thick filament (myosin)

what is CapZ on sarcomere

the edge of the sarcomere

what is titan in the sarcomere

spring for myosin

what terminates muscle contraction

Calcium ATPase (SERCA) pumps calcium back into SR which reduces available calcium

isotonic contractions maintain ..

constant tension in the muscle as the muscle changes in lengths

2 types of isotonic contractions and what they do

- concentric: muscle shortens

- eccentric: muscle lengthens

contraction of ___ muscle causes relaxation (lengthening) of its ___ muscle

- agonist

- antagonist

(this is why in the lab when the bicep was stimulated on the graph the triceps were not & vice versa)

what is reciprocal activation

contracting muscle relaxes, antagonist contracts

what is coactivations

during reciprocal activation there is minor involuntary activity in the agonist muscle to provide support for the joint

what are isometric contractions

contractions in which the joint angle and muscle length do not change

- co contraction

(triceps and biceps are stimulated on the graph at the same time)

what is EMG and what does it measure

Electromyography -> electric muscle graph

- measures electrical activity of skeletal muscle

device = electromygraph

data = electromyogram (EMG)

in the lab where we lifted weights, where were the electrodes put

1) first, only biceps

2) then, biceps and triceps

what is powerlab

perform data acquisition, signal conditioning and pre-processing

"SIGNAL CONDITIONING"

raw EMG vs Inegrated EMG

Inegrated EMG - an average of the raw EMG -> used for analysis oft he data

4 important aspects of electrode placement

- ensure good electrical contact

- away from tendon

- avoid hairy areas

- ground electrodes should be placed as far away as possible from the recording electrodes

when holding different weights did you record an increase of EMG activity

yes

what does the largest amplitude in the recording mean

- recruited additional motor units (and therefore muscle fibers)

in the data where the forearm is extended, how will bicep and triceps look on the graph

biceps: less amplitude

triceps: more amplitude

is co contraction isometric or isotonic

isometric

is a wall sit co contraction or reciprocal activation

co contraction

is a plank isometric or isotonic

isometric

is a push up isometric or isotonic

isotonic

Put these events in chronological order

A. Ach release into synaptic cleft.

B. Action potential propagates along axon of motor neuron

C. Ach receptor binding leading to Na+ influx into the motor endplate

D. Calcium from the sarcoplasmic reticulum in fluxes into the cytosol and binds to troponin in the muscle fiber

E. Muscle contraction

F. Ca++ influx through voltage-gated channels in the axon terminal at neuromuscular junction

BFACDE

Monitoring of EMG of patients during spinal cord or brain surgery can prevent _______

- paralysis of patients after surgery

we utilized ___ to measure the electical activity of the muscle

- EMG

we are utilizing a ________ to measure muscle tension

- force transducer

what do twitch, summation, unfused tetanus, and tetanus look like on a graph

what is the relation between summation and unfused tetanus

summation leads to unfused tetanus

what does the voltage from the stimulator mimic

the activation of motor units

what does the increase of the voltage stimulator do

- more muscle fibers are stimulated -> increased muscle contraction of the muscle

relationship between motor units and muscle and the all or none idea

motor unit = all or none

muscle = variable activation via recruitment

what is on ring stand 2

- stimulator connected to machine

why is the zero- and 5-gram measurement important

- used in calibration table

- calibration gives a baseline measurement

what was changed to achieve tetanus

frequency of stimulation

what was changed to achieve maximal contraction

higher amplitude of contraction

3 causes of muscle fatigue

- build up of molecules from lactic acid (ADP, PI, MG2+, H+)

- H+ competes with Ca2+ in binding with tropomyosin

- conduction failure (lack of power stroke)

In a state of rigor mortis, muscles are highly contracted and difficult to manipulate. Why does this phenomenon occur?

A) Excess stimulation from motor neuron

B) no stimulation from motor neuron

C) Lack of ATP

D) Lack of Calcium

C) Lack of ATP

why does rigor mortis go away

decomposition of tissue

what are the fibers within an earth worm

1 medial fiber (larger)

2 lateral fibers (smaller)

how do lateral fibers differ from the medial giant fiber in terms of threshold conduction

- lateral fibers have a higher threshold and slower conduction

in giant fibers (medial fibers) nerve cells are electrically ____________, so each giant fiber can _______________________

- coupled through gap junctions

- behave as if a single axon

what is the difference between intracellular and extracellular recordings

intracellular = direct

- records voltage potential across the membrane and is more accurate

extracellular = indirectly

- records potential changes at membrane surface

-requires electrode placement near excitable cell

in the earth worm lab are we recording intracellularlly or extracellularly

extracellularly

if the stimulating electrode is placed on the left, what are the electrodes next to it from left to right

- ground electrode

- negative electrode

- positive electrode

how is the calculation made using the electrodes

potential differences between 2 recording electrodes

- charge @ positive electrode - charge @ negative electrode)

in the earth worm data, there is a quick, tall amplitude before a second one that is a little shorter and wider:

- what is the first one and what is the second

- stimulus artifact

- biphasic wave

in the recruitment of the lateral fiber what will we see

see all or nothing response

when an initial stimulus is sent what does it cause

cause action potential to propagate down the medial giant fiber

what does a stronger stimulus cause

cause recruitment of the lateral fibers

what is important to do when you are recording to ensure the signal you are seeing is real and not noise

use overlay data mode and not "solo"

what is the absolute refractory period

Na+ channels are inactivated

- not stimulus will reopen the channels to allow Na+ in and depolarize them membrane

what is the relative refractory period

some of the Na+ channels are still inactivated but some have reopened

- however: the membrane potential is more negative making it difficult to depolarize

- needs a high stimulus

how to calculate velocity using the absolute method

V= D1/LP1

D1 - distance 1

LP1 = latency period 1

how to calculate velocity using the difference method

V = (D2-D1)/(LP2-LP1)

D = distance

LP = latency period

how to tell the dorsal view vs anterior view and head vs tail

- head is closer to clitellum (chunky tag piece

- dorsal = darker

how is the earthworm oriented in this lab

- dorsal side up

- stimulator on head

what can the biphasic wave be described as

an extracellular recording that only shows the AP propagation along the fiber

what is the latency period for the medial and lateral axons

medial: from stimulus artifact to beginning of first biphasic wave

lateral: from stimulus artifact to beginning of second biphasic wave

increasing the voltage of stimulation will __ the stimulus artifact and ___ the amplitude of the action potential

- why?

- increase

- not change

Amplitute of AP depends on properties of ion channes and it is not affected by stimulation strength (all-or-none)

when two stimuli are applied to a neuron and only one response is observed, you can conclude the neuron is in

refractory period

in the brain where is white matter compared to gray matter

white is deeper to gray matter

what is cranial nerve I and is it sensory, motor, or both?

olfactory

- sensory

what is cranial nerve II and is it sensory, motor, or both?

optic

- sensory

what is cranial nerve III and is it sensory, motor, or both?

oculomotor

- motor

what is cranial nerve IV and is it sensory, motor, or both?

trochlear

- motor

what is cranial nerve V and is it sensory, motor, or both?

trigeminal

- both

what is cranial nerve VI and is it sensory, motor, or both?

abducens

- motor

what is cranial nerve VII and is it sensory, motor, or both?

facial

- both

what is cranial nerve VIII and is it sensory, motor, or both?

vestibular

- sensory

what is cranial nerve IX and is it sensory, motor, or both?

Glossopharyngeal

- both

what is cranial nerve X and is it sensory, motor, or both?

Vagus

- both

what is cranial nerve XI and is it sensory, motor, or both?

accessory

- motor

what is cranial nerve XII and is it sensory, motor, or both?

hypoglossal

- motor

is the fissure of the spinal cord in the dorsal or ventral side

ventral

what is the path of the patellar reflex arc

- sensory receptor in agonistic muscle

- sent to dorsal root

- sent to internode that connects to 2 motor neurons

- one neuron is sent to agonist muscle

- one is sent to antagonist muscle

what is the Jendrysik maneuver

- enhances tendon reflex by clasping hands together and pulling as hard as possible

- person should look somewhere else and think of other things

what is it called when there are only 2 neurons in the reflex arc

monosynaptic

what is it called when a reflex arc contains an interneuron ascending the spinal cord

polysynaptic

what are the 5 endocrine tissues in our body

- pituitary gland

- thyroid gland

- parathyroid gland

-pancreas

- adrenal gland

what is the thyroid gland responsible for

metabolism

what are the cells found in the thyroid and why are they important

follicular cells

- produce thyroglobin that is a precursor of thyroid hormones

- contain T3 and T4

- increases metabolic rate

what is the thyroid hormone pathway and what is produced in each place

TRH produced in hypothalamus

-TSH produced in anterior pituitary

- T3/T4 produced in thyroid

what are 3 important aspects of the thyroid hormones T3 and T4

- increase metabolism of carbohydrate, fats, and proteins

- increase O2 consumption

- produce heat

what are 3 important aspects of Propylthiouracil

- PTU interferes with iodination process during the production of thryroglobin

- decreases thyriod function (hypothyroidism)

- decreases O2 consumption

what are the 3 different groups in the rat experiment

- control group

- thyroid hormone

- PTU

in step 1 of the rat lab, how do we determine mL of O2 consumed

total O2 consumed across all trials/ (total time in seconds/60)

-> 3 trials x5mL per trial / (total time in seconds/60)

based on ours it was

15ml/(total time in seconds/60)

in step 2 of the rat lab, how do we determine the amount of air inhaled using mL of O2 consumed

Use O2 consumption rate from step 1 / 0.21

- atmosphere is 21% oxygen

in step 3 for the rat lab how do we normalize for mass of the mouse

calculated O2 consumption rate (Step1)/ mass of mouse in grams

what are the 4 zones of the adrenal gland

- zona glomerulosa (mineral corticoids)

- zona fasciculata (glucocoritcuts)

- zona rectularis (sex hormones)

- adrenal medulla (epinephrine and norepinephrine)

what is the iris

colored part of the eye that opens and closes the pupil

what is the pupil

hole at center of the eye that allows light to enter

what is the retina

inner most layer of the eye and composed of multiple specialized optic cells