Study Guide - Lab practical 2 PDF

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PNB2264 PRACTICAL 2 STUDY GUIDE: (Resources: Lab PPT, Tophat, Kuracloud, and VHD; Anything from Kuracloud, TopHat, and PPT from labs can be on practical) Lab 5 Objectives:

· Histology: cerebral cortex and cerebellum - Know the cells within these two histologies

Cerebellum-Golgi staini The cerebellum is the small brain, important for motor coordination. It is situated below the occipital lobe. The cortex of cerebellum has three layers: 1. molecular (on right side of the picture), that contains dendrites of the middle layer- Purkinje cells (2) and granular cells that are closest to the white matter (left bottom side of the picture). Principal cells in the cerebellum are Purkinje cells, that are sending signals outside of the cerebellar cortex.

You will be responsible to distinguish between cerebral and cerebellar cortex during the lab.

Cerebral cortex

cerebellum

· Calculate Nernst potential, and Membrane potential (parallel conductance equation)NEED TO KNOW FORMULA

where R=universal gas constant, z=ion valence, F=Faraday's constant, T=temperature (in Kelvin), [ion]o=ion concentration outside the cell, and [ion]i=ion concentration inside the cell.

· Describe the role sodium and potassium ions have on the establishment of the resting membrane potential. The negative charge within the cell is created by the cell membrane being more permeable to potassium ion movement than sodium ion movement. In neurons, potassium ions are maintained at high concentrations within the cell while sodium ions are maintained at high concentrations outside of the cell.

Potassium conductance higher than sodium This potential exists because of a tiny excess of negative ions inside the cell— mainly large immobile organic anions—and an excess of positive ions outside (mainly sodium ions). This potential is maintained through the constant action of ATPconsuming pumps that continually re-establish this charge difference by actively

pumping ions across the membrane. · Predict how changes in ion channel conductance alter the membrane potential. Vm tends towards Eion w biggest conductance · To know what is the flow of ions under different conditions when you vary concentration gradient or voltage · To know how to read and analyze action potential recording after application of different toxins (postlab slides) Go back and read case study 1 & 2 from kura cloud lab 5 - understand

Lab 6 Objectives:

·

Learn to use hardware POWERLAB and associated software in the Lt

Read through lab 6 in kura cloud ·

What is force transducer, why do we need calibration?

First step is to do calibration of the force transducer. Raw output from the force transducer is in millivolts (mV). This raw output needs to be calibrated to give us the more meaningful force unit of milli-Newtons (mN). A force transducer is another type of sensor used in modal testing. Like an accelerometer, a piezoelectric force transducer generates an output charge or voltage that is proportional to the force applied to the transducer · What is threshold, maximal and supramaximal excitation stimulus? The threshold is that intensity (voltage) of stimulus which brings response. As the intensity (voltage) of the stimulus is increased above the threshold, more and more fibers are stimulated and the response becomes greater and greater. This stimulus, called the maximal stimulus marks the point where all of the fibers in the muscle are stimulated and responding all-or-none. Stimuli above this maximal stimulus are called supramaximal stimuli. · Reminder: single muscle fiber has all or none response, muscle (with many muscle fibers) has graded response · Twitch, Length-tension curve, frequency modulation experiments (summation, tetanus, fatigue): recordings, graphs, explanations STUDY LAB 6

Lab 7: EMG

·

Learn to use hardware POWERLAB and associated software in the Lt

Lab 7 ·

Record EMG signals in Lt

Lab 7 ·

Learn to use the annotation and to analyze signals in the Lt software.

Lab 7 ·

Learn to differentiate reciprocal activation, and co-contraction

Reciprocal activation : Reciprocal inhibition describes the process of muscles on one side of a joint relaxing to accommodate contraction on the other side of that joint. Joints are controlled by two opposing sets of muscles, extensors and flexors, which must work in synchronicity for smooth movement. When a muscle spindle is stretched and the stretch reflex is activated, the opposing muscle group must be inhibited to prevent it from working against the resulting contraction of the homonymous muscle. This inhibition is only partial, as can be seen in the EMG below. In this recording you can notice that during flexion of biceps, triceps is not completely inhibited, and vice versa. That phenomenon is called coactivation.

Muscle co-contraction occurs when agonist and antagonist muscles surrounding a joint contract simultaneously to provide joint stability. It is

also known as muscle co-contraction, since two muscle groups are contracting at the same time. Muscle co-contraction allows muscle groups surrounding a joint to become more stable.

· Define isometric and isotonic contractions and relate them to the exercises we did in lab A contraction that results in a change of length (shortening or lengthening) while the load on the muscle remains constant, is isotonic contraction. When tension exceeds the load shortening occurs- concentric contractions; when an unsupported load is greater than tension, the result is eccentric contractions. The force exerted on the object by a contracting muscle is known as muscle tension and a force exerted on a muscle by an object (usually by weight) is the load. Those two forces are opposing forces. For the muscle to shorten and thereby to move a load, muscle tension has to be greater than the opposing load. When muscle develops tension but does not shorten (does not change a length) that is an isometric contraction. The example of that would be holding a heavy object in your hand and keeping the elbow in the flexed position.

Look at lab exercises in kura cloud Lab 8 objectives: · Understand the differences between intracellular recording and extracellular recording. Intracellular recording involves measuring voltage and/or current across the membrane of a cell. For the intracellular recording, the tip of a fine sharp glass microelectrode with a tip diameter of < 1 micrometer, must be inserted inside the cell, recording the potential changes inside concerning an extracellular reference electrode. Typically, the resting membrane potential of a healthy cell will be -60 to -80 mV (more negative inside relative to outside), and during an action potential, the membrane potential might reach +40 mV (more positive inside relative to the outside). In 1963, Hodgkin and Huxley won the Nobel Prize in Physiology or Medicine for their contribution to understanding the mechanisms underlying the generation of action potentials in neurons. An extracellular recording detects only the small potential difference that arises from the action current flowing in the extracellular medium around the nerve fiber. It records potential changes at the membrane surface rather than across the membrane. In this case, one electrode is placed near the membrane, while the other reference electrode is at some location in the extracellular fluid. When detected intracellularly, the amplitude of a typical action potential measures between 80–100 mV. However, when recorded extracellularly, the amplitude appears much smaller, less than a thousandth of the amplitude of the action potential itself (measured in microvolts). The second difference of extracellular (on the right in the image below) vs. intracellular recording (on the left) is the shape of the recording. The shape of the waveform of action potential will depend in this case on the exact geometry of its contact with the electrode. In this lab, we will use two stainless steel electrodes that are both in the contact with the ventral nerve cord of the earthworm and will be recording the potential difference between two points on the nerve. For both intracellular and extracellular recording, the AP recording is biphasic, with positive and negative deflection, but for different reasons. In the intracellular recording, positive deflection represents depolarization and negative deflection represents hyperpolarization.

·

\

Describe the all-or-none response of a single axon. The all-or-none law is a principle that states that the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus. If a stimulus is

above a certain threshold, a nerve or muscle fiber will fire all or none response youtube video · Determine nerve conduction velocity using absolute (V=distance/latency period) and differential method V= D2-D1/LP2-LP1 NEED TO KNOW FORMULA The first method - the absolute method- estimates the velocity using the distance between the sites of stimulation and first recording electrode (in millimeters), and the recorded time interval between the stimulus and the positive peak of the MGF potential (in msec). The LGF velocity is obtained accordingly. Conduction Velocity is calculated by dividing distance (mm) over time (ms).

The second method- the difference method- is a classical way to measure the velocity, using a double recording setup. Here, the distance of the two recording sites and the two intervals of recorded potentials are used.

While the first method assumes that action potential generation at the site of electrical stimulation does not require any extra time, the second method provides an accurate measurement of the mean conduction velocity of the piece of axon between the two sites of recording. For both methods, it is important that electrode distances are measured, otherwise, velocities cannot be calculated. · Explain the difference between the absolute and relative refractory periods of a nerve The interval at which the second response first drops out marks the end of the refractory period, although the observed interval will depend on the strength of the stimulus. A stronger stimulus can force a second spike before the refractory period has fully ended. You may also see the amplitude of the second action potential become smaller than normal as the delay is reduced, reflecting the elevated potassium-conductance and a large number of inactivated sodium channels that trail behind the first action potential.

The refractory period in neurons occurs after an action potential and generally lasts one millisecond. Remember form lab 7 that the action potential has three phases: depolarization, repolarization, and hyperpolarization. The refractory periods are due to the inactivation property of voltage-gated sodium channels and the time that the potassium channels need to be closed. Voltage-gated sodium channels have two gating mechanisms, the activation mechanism that opens the channel with depolarization and the inactivation mechanism that closes the channel with repolarization. While the channel is in the inactive state, it will not open in response to depolarization. The period when the majority of sodium channels remain in the inactive state is the absolute

refractory period. After this period, when you apply enough higher voltage to voltageactivated sodium channels in the closed (active) state to respond to depolarization, they will open. However, voltage-gated potassium channels that opened in response to repolarization do not close as quickly as voltage-gated sodium channels; to return to the active closed state. During this time, the extra potassium conductance means that the membrane is at a higher threshold and will require a greater stimulus to cause action potentials to fire. Because of the fact that the membrane potential inside the axon becomes increasingly negative relative to the outside of the membrane, a stronger stimulus will be required to reach the threshold voltage, and thus, initiate another action potential. This period is the relative refractory period. youtube video

·

Explain biphasic recording

The BIPHASIC action potential results from the recording system which uses two surface electrodes of opposite polarity. Electrical stimulation of the nerve gives rise to a compound nerve action potential (CNAP). The resulting wave of depolarisation is conducted towards the two recording electrodes. youtube video Lab 9 objectives: · Define monosynaptic and polysynaptic reflex and reflex arc. Jendrassic maneuver Reflexes are rapid, involuntary motor responses to environmental stimuli, detected by sensory receptors. A nerve impulse travels from the receptor through a neural reflex arc to effectors. If the motor response is a contraction of skeletal muscle that is a somatic reflex. When the integration takes place in the spinal cord, the reflex is a spinal reflex. Reflexes that involve only two neurons- sensory (receptor) and motor neurons (in the spinal cord) that make one synapse are monosynaptic. If there is an interneuron in the circuitry and existence of two synapses ( 1. between the sensory neuron and the interneuron; 2. between the interneuron and the motor neuron), that is defined as a polysynaptic arc (as in the image above).

·

Understand recording and analysis

Read through that part of lab 9 · Identify the major external and internal structures of the brain on a human brain model and a preserved sheep brain. ·

Identify the cranial nerves on a human brain model or a preserved sheep brain.

·

Identify important anatomical areas on a spinal cord model or diagram.

On the cord locate

spinal model, the

following:

1. White matter 2. Dorsal root 3. Gray matter (dorsal and ventral horns) 4. Dorsal root ganglion 5. Anterior median fissure 6. Ventral root 7. Posterior median sulcus 8. Central canal

a.

Brain-Superior (Dorsal) view: 1. gyri 2. sulci 3. longitudinal cerebral fissure 4. frontal lobe 5. parietal lobe 6. occipital lobe

Brain- Lateral (Sagittal) view: 1. frontal lobe 2. parietal

lobe 3. temporal

lobe 4. occipital

lobe 5. central

sulcus 6. lateral sulcus 7.

somatomotor area

8. somatosensory area 9. cerebellum

Brain-Inferior (Ventral) view: 1. 2. 3. 4. 5.

olfactory bulb optic chiasma mammillary bodies pons medulla oblongata

cerebellu

6.

m

Brain- Midsagittal view: 1. frontal lobe 2. parietal lobe 3. occipital lobe 4. lateral ventricle 5. third ventricle 6. cerebral aqueduct 7. fourth ventricle 8. corpus callosum 9. fornix 10. optic chiasm 11. thalamus 12. pineal gland 13. superior colliculi

14. inferior colliculi 15. midbrain 16. pons 17. medulla oblongata 18. cerebellum

Cranial nerves: 12 cranial nerves, location and function (sensory, motor or mixed).

cranial nerves info website

SHEEP Spinal cord

a. Brain-Superior (Dorsal) view: 1.

gyri

2.

sulci

3. longitudinal cerebral fissure 4.

frontal lobe

5.

parietal lobe

6.

occipital lobe

Brain- Lateral (Sagittal) view: 1.

frontal lobe

2.

parietal lobe

3.

temporal lobe

4.

occipital lobe

5.

central sulcus

6.

lateral sulcus

7. somatomotor area 8. somatosensory area 9.

cerebellum

Brain-Inferior (Ventral) view: 1.

olfactory bulb

2.

optic chiasma

3.

mammillary bodies

4.

pons

5.

medulla oblongata

6.

Cerebellum

1. olfactory bulb 2. optic chiasm (crossing) 3. mammillary bodies (2 in human, one in sheep) 4. pons 5. medulla oblongata 6. cerebellum

Brain- Midsagittal view: 1.

frontal lobe

2.

parietal lobe

3.

occipital lobe

4.

lateral ventricle

5.

third ventricle

6.

cerebral aqueduct

7.

fourth ventricle

8.

corpus callosum

9.

fornix

10.

optic chiasm

11.

thalamus

12.

pineal gland

13.

superior colliculi

14.

inferior colliculi

15.

midbrain

16.

pons

17.

medulla oblongata

18.

Cerebellum

Cranial nerves: 12 cranial nerves, location and function (sensory, motor or mixed).

Lab 10 objectives: · identify selected endocrine tissue on microscope slides images- pituitary, thyroid, parathyroid, pancreas, adrenal gland

thyroid

parathyroid

Pancreas The pancreas is the main enzyme-producing accessory gland of the digestive system. It has both exocrine and endocrine functions. The exocrine part of the pancreas has closely packed serous acini, similar to those of the digestive glands. The endocrine part of the pancreas consists of isolated islands of lighter staining cells called islets of Langerhans, clumps of secretory cells supported by reticulin fibers, and containing

numerous fenestrated capillaries. There are three secretory cells types that are present:

1. alpha - secrete glucagon ( prevent blood glucose levels dropping too low) 2. beta - secrete insulin (prevent blood glucose levels dropping too high) 3. delta - secrete somatostatin (inhibits the secretion of glucagon and insulin)

pituitary

·adrenal gland

understand the physiologic importance of metabolic rate measurement. The thyroid hormones, T3 and T4, are often referred to as metabolic hormones because their levels influence the body’s basal metabolic rate, the amount of energy used by the body at rest. When T3 and T4 bind to intracellular receptors located on the mitochondria, they cause an increase in nutrient breakdown and the use of oxygen to produce ATP. In addition, T3 and T4 initiate the transcription of genes involved in glucose oxidation. Although these mechanisms prompt cells to produce more ATP, the process is inefficient, and an abnormally increased level of heat is released as a byproduct of these reactions. This so-called calorigenic effect (calor- = “heat”) raises body temperature.

Adequate levels of thyroid hormones are also required for protein synthesis and for fetal and childhood tissue development and growth. They are especially critical for normal development of the nervous system both in utero and in early childhood, and they continue to support neurological function in adults. As noted earlier, these thyroid

hormones have a complex interrelationship with reproductive hormones, and deficiencies can influence libido, fertility, and other aspects of reproductive function. Finally, thyroid hormones increase the body’s sensitivity to catecholamines (epinephrine and norepinephrine) from the adrenal medulla by upregulation of receptors in the blood vessels. When levels of T3 and T4 hormones are excessive, this effect accelerates the heart rate, strengthens the heartbeat, and increases blood pressure. Because thyroid hormones regulate metabolism, heat production, protein synthesis, and many other body functions, thyroid disorders can have severe a...