Animal Physiology Lecture Notes

Week 10: Homeostasis and Membrane Potential

Homeostasis

• Definition: Maintenance of a stable internal environment (e.g., blood pH, CO2 concentration, temperature, and osmotic balance).
• Key Components:
  • Receptor: Detects changes and sends a signal to the control center.
  • Control Center: Determines the normal range and sends instructions to the effector.
  • Effector: Implements changes to return to balance (e.g., sweating to cool down).
• Role of Hypothalamus: Regulates body temperature.
• Heat Loss and Prevention:
  • Evaporation, conduction, and radiation.
  • Countercurrent principle: Reduces heat loss via heat exchange between blood vessels.

Hormones Involved in Homeostasis

• Thyroxin: Regulates metabolic rate and body temperature.
• Leptin: Secreted by adipose tissue, reduces appetite by acting on the hypothalamus.
• Melatonin: Regulates sleep cycles, affected by light exposure.
• Insulin and Glucagon: Produced by the pancreas, regulate blood glucose levels.
• Diabetes Types:
  • Type I: Autoimmune, no insulin production.
  • Type II: Insulin resistance, often diet-related.

Feedback Regulation

• Negative Feedback: Maintains stability by reversing changes (e.g., body temperature control).
• Positive Feedback: Amplifies responses (e.g., blood clotting).

Week 11: Membrane Potential

Membrane Potential Overview

• Definition: Difference in electrical charge across a cell membrane, vital for functions like nerve signaling and muscle contraction.
• Resting Membrane Potential (RMP): Around -70 mV in many cells.

Sodium-Potassium Pump (Na⁺/K⁺-ATPase)

• Function: Moves 3 Na⁺ out and 2 K⁺ into the cell, using ATP.
• Importance: Establishes the electrochemical gradient, critical for RMP.

Ion Channels

• Types:
  • Ligand-gated
  • Mechanically-gated
  • Always open
  • Voltage-gated

Action Potential

• Process:
  1. Depolarization: Na⁺ influx due to voltage-gated Na⁺ channels. Positive feedback loop.
  2. Repolarization: K⁺ efflux restores negative membrane potential.
  3. Hyperpolarization: Overshoot of repolarization.
• Refractory Period: Time post-impulse when a neuron can't fire.
• Myelination: Speeds up signal transmission. Issues in diseases like multiple sclerosis.

Week 13: Sensory Physiology

Neurons

• Structure: Dendrites (receive signals), axon (transmits impulses), soma (cell body).
• Central Nervous System (CNS): Brain and spinal cord.
• Peripheral Nervous System (PNS): Connects CNS to limbs and organs.

Sensory Receptors

• Mechanoreceptors: Detect pressure, vibration.
• Photoreceptors: Rods and cones in the retina; responsible for vision.
• Thermoreceptors: Detect temperature changes.
• Chemoreceptors: Detect chemical stimuli in taste and smell.

Vision

• Components: Cornea, lens, retina (with rods and cones).
• Color Vision: Mediated by cones sensitive to different wavelengths (trichromacy).

Hearing

• Ear Structure: Pinna, auditory canal, ossicles for sound transmission.
• Cochlea: Converts sound into neural signals.

Weeks 14-20: Other Topics (Muscle, Autonomic Nervous System, Endocrinology, Circulation, Reproduction, Respiration, Osmoregulation)

• Detailed exploration of specific topics not mentioned in the provided transcript.

Sources

• https://bio.libretexts.org/Courses/Hanover_College/Comparative_Anatomy_and_Physiology_of_Animals/06%3A_Sensory_Physiology
• https://louis.pressbooks.pub/generalbiology2leclab/chapter/the-peripheral-nervous-system/