Animal Phys Lab Practical 1

The first machine invented to measure physiological events

Kymograph

Inventor of the Kymograph

Carl Ludwig

Electronic machines used to produce a permanent record of a physiological event

Recording oscillographs

The functioning unit of the recording oscillograph.

Recording channel

3 components of a Recording Channel

1. A sensing device

2. A processor

3. A recorder/reproducer

Picks up information from the experimental set up. Components are the Electrode and Transducer

The Sensing Device

A device used to detect electrical events (e.g. EKG, EEG, “pin,” “sleeve”)

Electrode

Transforms a non-electrical signal into an electrical signal that the computer can understand.

Transducer

Takes the electrical signal from the Transducer. Components are the Coupler and the Amplifier

Processor

Alters the electrical signal so it can be recognized by the rest of the recording channel

Coupler

This amplifies (boosts) the signal received proportionally so it can be measured

Amplifier

Device for making a permanent recording of a physiological event (the computer, printer etc.)

Reproducer/Recorder

Matches the signal from the sensing device with the processor (like setting a scale to 0)

Balancing

Standardizes the recording channel; lets us quantify our results (like setting the increments on the scale)

Calibrating

Devices for administering a controlled electrical signal to an excitable tissue to elicit a response.

Stimulators

The lowest stimulus that will elicit a physiological response

Threshold stimulus

Stimulator Variables

• Intensity

• Frequency

• Duration

The strength of a stimulus measured in volts.

Intensity

The number of impulses administered per second measured in Hertz

Frequency

The length of time each impulse lasts (Milliseconds) (NOT the total length of time impulses are administered to a subject.)

Duration

A motor neuron and all the muscle fibers it innervates- the functional unit of muscle contraction

Motor Unit

Three parts of the Motor Unit

• Neuron

• Neuromuscular Junction (NMJ)

• Muscle Fibers

The basic unit of skeletal muscle

Muscle Cell

Plasma membrane surrounding a muscle fiber

Sarcolemma

__ extend the entire length of a fiber but are arranged in compartments called sarcomeres.

Myofilaments

Parts of a Sarcomere

• Actin

• Tropomyosin and Troponin

• Myosin

Primary component of the thin myofilament.

Actin

Prevents actin and myosin from binding together

Tropomyosin and Troponin

Primary component of the thick myofilament.

Myosin

First Step of the Sliding Filament Theory

New ATP attaches to the myosin head; the cross bridge detaches

Second Step of the Sliding Filament Theory

ATP is split into ADP and Pi; cocking of the myosin head occurs

Third Step of the Sliding Filament Theory

Myosin cross bridge attaches to the actin myofilament

Fourth Step of the Sliding Filament Theory

“Power stroke” (working stroke) happens- the myosin head pivots and bends as it pulls on the actin filament, sliding it towards the M line. ADP and Pi are released

Neuron

In order for the muscle fiber to contract, a stimulus must be delivered from a neuron.

Neuromuscular Junction (NJM)

When the action potential reaches the end of the neuron, voltage-gated Ca2+ channels open and calcium rushes into the neuron

Influx of ___ causes vesicles filled with Actetylcholine to fuse with the neural membrane.

Ca2+

___ is released into the neuromuscular junction where it binds to chemically gated Na+ Channels on the sarcolemma of the muscle fiber. This causes an action potential on the sarcolemma

Acetylcholine (Ach)

3 Periods of a Normal Form Curve (Muscle cell Twitch)

• Latency

• Contraction

• Relaxation

Three Enzymes in Muscle Contraction

• Acetylcholinesterase (AchE)

• Myosin ATPase

Sarcoendoplasmic Reticulum Calcium ATPase (SERCA) pump / Calcium Pump

This enzyme breaks down Acetylcholine in the NMJ

Acetylcholinesterase (AChE)

What effect will decreased AChE function have on muscle contraction?

Increase in ACh contact with Nicotinic receptors; increase in stimulation of Ca2+ release; increase in the length of contraction

An ATPase that converts chemical energy into directed movement and can be viewed as a molecular motor; cleaves ATP at the myosin heads.

Myosin ATPase

What effects will we see from decreased function of Myosin ATPase?

Decrease in ratcheting; decrease in force; increase in contraction time

Acts to transport calcium ions from the cytosol back to the sarcoplasmic reticulum following muscle contraction; cleaves the ATP that runs the calcium pump on the SR.

SERCA/ Calcium Pump

The affects of Fatigue are:

• Depleted ATP

• Decrease in ratcheting

• Decrease in contractile force

What effect will we see from decreased function of SERCA/ Calcium Pump?

Increased time of Ca2+ in the sarcoplasm; increase in ratcheting; increase in contraction; increase in relaxation time prolonging Ca2+ residence in the sarcomere; decrease in sequester rate of Ca2+, also prolonging Ca2+ residence in the sarcomere

The effect of Smooth Muscle not having T-tubules:

The wave of depolarization is slow, with long-lasting contractions and slow relaxation

___ allows Na+ to diffuse at a slow but continuous rate, causing a slow wave of depolarization

“Leaky” Na+ channels

The smooth muscle cell membrane is more __ to ions _ and _ , allowing them to leak across the membrane and into the muscle cells.

permeable; Na+, Ca2+

Allows smooth muscle to contract, even without generating a typical action potential

Slow Wave Depolarization

When action potentials for contraction originate within the muscle, the muscle is called __

Myogenic

Smooth Muscle is modified by__

neural input

Smooth Muscle is double innervated by both the ___ and the ___

Sympathetic NS; Parasympathetic NS

In the Isolated System of the Autonomic control of smooth muscle, an isolated system includes the complete __

Short Postganglionic fiber of the Parasympathetic pathway

Parasympathetic innervation occurs via the __

Vagus Nerve

Sympathetic innervation occurs via the __

Coeliac Ganglion

Type of receptors in the Parasympathetic Pathway:

Cholinergic receptors (Nicotinic and Muscarinic)

Type of receptors in the Sympathetic Pathway:

Adrenergic Receptors (Alpha and Beta)

Neurotransmitter of the Parasympathetic Pathway that modifies the Smooth Muscle

Acetylcholine (Ach)

Neurotransmitters of the Sympathetic Pathway that modifies the Smooth Muscle

Catecholamines of Norepinephrine (NE) and Epinephrine (Epi)

Epinephrine is a __ neurotransmitter

adrenergic

Epinephrine works in the Sympathetic pathway and only bind to the __ and __ on the gut.

Alpha 2; Beta 2

___ opens K+ channels and hyperpolarizes the membrane; inhibits smooth muscle contraction.

Epinephrine

__ binds to __ receptors on the postganglionic parasympathetic nerve and muscarinic receptors on the sarcolemma.

Acetylcholine; N2

__ opens Na+ channels, depolarizes the membrane and causes an increase in contraction strength, frequency OR a smooth tonic contraction

Acetylcholine (Ach)

An anticholinesterase (potentiator of ACh) that prevents the breakdown of ACh by ACh-esterase (cholinesteras)

Physostigmine

Cause of Physostigmine on smooth muscle contraction

Contractions should increase in strength, frequency, or both because the myenteric plexus is spontaneously active.

Atropine is a __ blocker, meaning __ can no longer bind and motility decreases

muscarinic; Acetylcholine

Which component of the motor unit does lidocaine directly affect?

The lipid bilayer- makes it rigid/ less flexible and less able to generate action potential

Which component of the motor unit does d-tc directly affect?

Nicotinic (N2) receptor- blocks receptor and prevents Ach from binding and the transmission of the action potential.

The opening of what ion channels cause action potentials?

Sodium (Na+) channels

What causes a contraction when the nerve is pinched?

Mechanical disruption to the membrane allows Na+ to enter the cell, causing depolarization of the membrane and generation of an Action Potential

Where do you add lidocaine?

Sciatic Nerve

Name the nerve and muscle we are using in today’s lab.

Gastrocnemius muscle and Sciatic nerve

If temperature is decreased, what happens to the relaxation phase of a normal form curve?

Decreased temperatures slows down enzyme function, resulting in longer relaxation phase; the process of relaxation and contraction are negatively affected

Motor-unit summation is achieved by increasing the ___ of the stimulus.

Strength (intensity)

T or F: During the absolute refractory period of the nerve, a second stimulus produces a greater response than the first stimulus.

False

Smooth muscles sarcomere are arranged__

Non-linearly

What does smooth muscle not have that other types do?

T-tubules

What is the result of no T-tubules in smooth muscle?

Slow wave depolarization that produces long-lasting contractions with slow relaxation

The cell membrane smooth muscle cells are more permeable to __

Na+ and Ca2+ ions

What allows Na+ to diffuse at a slow, continuous rate, causing a slow wave of depolarization?

Leaky Na+ channels

What does it mean for the sooth muscle to be myogenic?

Action Potentials originate within the muscle and nervous system innervation is not necessary for contraction

What does it mean for something to be double innervated?

It is controlled by both the Sympathetic and Parasympathetic NS

What type of receptors are located in the Parasympathetic NS?

Cholinergic (Nicotinic, Muscarinic receptors)