Anatomy Lab Practical

Verapamil

Calcium channel blocker cardiac depressant and vasodilator

Describe the mechanisms by which epinephrine affects heart rate.

Epinephrine INCREASES heart rate and contractibility by stimulating the sinoatrial (SA) node and the atrioventricular (AV) node and enhancing Ca2+ ion release via second messenger pathways. Mimics effects of sympathetic nervous system.

Acetylcholine

Muscarinic receptor agonist Action: Released by parasympathetic nerves, such as the vagus nerve. Effect: Decreases heart rate and force of contractions

Pilocarpine

Muscarinic receptor agonist Action: Stimulates muscarinic acetylcholine receptors in the heart. Effect: Decreases heart rate

Atropine

Muscarinic receptor blocker (antagonist) Action: Blocks muscarinic acetylcholine receptors in the heart. Effect: Increases heart rate

Inferior rectus

Rotates the eye downward and toward the midline

Pituitary Gland Histology

A = Posterior pituitary B = Anterior pituitary

Describe the volunteer's skin potential response after the startle, gasp, and thump stimuli. How can you explain these findings?

The startle showed the quickest hand and foot latency as well has highest amplitude. The gasp was in the middle of the results and the sternal thump showed in general the slowest latency and smallest amplitude. The exact amplitude measurements were not able to be recorded as the software on this page only displayed the time. To explain these findings, some different types of tissues are only supplied by just one division of the ANS. As a result, the gasp response activates the SNS by the stimulation of lung stretch receptors which in turn would eventually increase heart rate.

How did temperature affect heart rate?

Warm temperatures increase heart rate while cool temperatures decrease heart rate.

Ouabain

inhibits the sodium potassium ATP-ase, boosting intracellular calcium and increasing myocardial contractility in a failing heart. speeds up the heart

Testicle Histology

know it

Sympathetic Nervous System

1. Accelerates heart rate (SA node) 2. Increases force of contraction of the ventricular myocardium 3. Norepinephrine is released at sympathetic nerve terminals and acts on beta-adrenergic receptors in the pacemaker cells of the sinoatrial node and on cardiac muscle cells of the ventricles 4. Action of norepinephrine (and epinephrine) on the heart is blocked by beta-blockers

Parasympathetic Nervous System

1. Slows down heart rate (SA node0 2. Does not alter force of contraction of ventricles because it doesn't innervate them 3. Acetylcholine is released at parasympathetic nerve terminals and acts on nicotinic receptors on intramural neurons which also release acetylcholine, which binds to muscarinic receptors in the pacemaker cells of SA node 4. Muscarinic receptors are blocked by atropine

Describe the mechanisms by which acetylcholine affects heart rate.

Acetylcholine DECREASES heart rate by hyperpolarizing pacemaker cells in the cardiac muscle by opening potassium ion channels.

Compare the effect of acetylcholine on cardiac muscle with its effect on skeletal muscle. Can you explain the mechanistic basis for the difference?

Acetylcholine causes INCREASED activation of SKELETAL muscle, but it INHIBITS CARDIAC muscle contractions In skeletal muscle, acetylcholine receptors are coupled to sodium channels, causing a depolarization and an increase in excitability of the tissue In cardiac muscle, acetylcholine receptors are instead coupled to potassium channels. When these potassium channels open, they cause hyperpolarization and a decrease in excitability of the tissue

Epinephrine

Adrenergic receptor agonist Action: Released into the bloodstream by the adrenal medulla Effect: Increases heart rate and force of contraction

Norepinephrine

Adrenergic receptor agonist increases heart rate and blood pressure

Phentolamine

Alpha receptor antagonist increases heart rate

Describe the mechanisms by which atropine followed by acetylcholine affects heart rate.

Atropine binds and blocks acetylcholine receptors. This prevents acetylcholine from decreasing the heart rate so heart rate INCREASES.

Propranolol

Beta receptor antagonist slows down heart rate

How can you explain the change in potential across the hand and foot that follows peripheral nerve stimulation?

The change in potential across the hand and foot correlates to the sweat glands being activated by different stimulations. The hand's sweat glands are controlled through the sympathetic stimulation of their nerves creating a different in potential between the two.

How do the latencies and amplitudes in the skin of the hand and the foot compare? Explain any differences in the latencies.

The hand will have a higher amplitude than the foot but the foot will have a higher latency value than the hand. Since the foot stimulus has to travel a longer distance in order to produce a response, we would expect a higher latency time than that of the hand.

Lateral rectus

rotates the eye away from the midline

Superior oblique

rotates the eye downward and away from midline

Medial rectus

rotates the eye toward the midline

Inferior oblique

rotates the eye upward and away from the midline

Superior rectus

rotates the eye upward and towards the midline