Physiology Basics and Nervous System Overview

Unit 1 – Basics of Physiology

• Solutions: Normal saline (NS) is isotonic; 1/2 NS is hypotonic; D5 is initially isotonic but becomes hypotonic after glucose use; D5NS and D5 1/2NS start isotonic, then become hypotonic as glucose is used.
• Membrane Transport: Passive transport (diffusion, facilitated diffusion) does not require energy; Active transport (e.g., sodium-potassium pump) requires energy; Secondary active transport uses the gradient created by primary active transport to move substances (e.g., glucose) into cells.
• Reflex Pathway: Afferent signals detect a stimulus. The integrating center processes the stimulus. Efferent signals trigger a response.
• Hormone Release: The hypothalamus releases CRH, TRH, and GnRH. The anterior pituitary gland releases ACTH, TSH, and LH/FSH in response to these hormones.

Unit 2 – Nervous System and Communication

• Signal Transmission: Graded potentials are short-distance signals that decrease in strength over time. Action potentials are all-or-none signals that travel long distances.
• Brain Lobes: Frontal lobe: decision-making; Parietal lobe: sensory input processing; Occipital lobe: vision; Temporal lobe: hearing and memory.
• Lateral Inhibition: This process enhances sensory perception by inhibiting adjacent neurons.
• Vision (Rods and Cones): Rods are for low light and peripheral vision; Cones handle color and high acuity; Dark current maintains sodium channels open in the dark, thus depolarizing rods.

Unit 3 – Cardiovascular Physiology

• Pacemaker Cells (SA Node): Generate rhythmic action potentials; If channels allow slow sodium influx, driving depolarization.
• ECG Waves: P wave: atrial depolarization; QRS complex: ventricular depolarization; T wave: ventricular repolarization.
• Pressure-Volume Curve: Events include ventricular filling, isovolumetric contraction, ejection, and isovolumetric relaxation.
• Baroreflex: A reflex that helps regulate blood pressure, using sensors in the carotid arteries and aorta.

Unit 4 – Respiratory and Renal Physiology

• Respiratory Pathologies (e.g., COPD): COPD is a major respiratory pathology characterized by airflow limitation.
• CO2 Transport: Mostly transported as bicarbonate in the plasma, facilitated by carbonic anhydrase.
• Renal System (GFR Autoregulation): Mechanisms (myogenic mechanism, tubuloglomerular feedback) keep glomerular filtration rate (GFR) stable.
• Renin-Angiotensin-Aldosterone System (RAS): Renin converts angiotensinogen to ANG II, raising blood pressure and stimulating aldosterone release.
• Hormones (ADH and ANP): Antidiuretic hormone (ADH) increases water reabsorption. Aldosterone promotes sodium retention. Atrial natriuretic peptide (ANP) counteracts ADH and aldosterone by promoting sodium excretion.
• Dehydration: Triggers responses like ADH release and vasoconstriction to maintain blood pressure.

Closing Remarks

• Coverage: Units 1 through 4 were discussed, covering topics from osmolarity to pH balance.
• Exam Preparation: Emphasized the importance of continued practice for the exam success.

This quiz covers the fundamental concepts of physiology, including membrane transport, reflex pathways, and hormone release. It also explores the basics of the nervous system and communication, focusing on graded potentials and signal transmission. Test your understanding of these essential physiological mechanisms.