Veterinary Physiology I

This course introduces the physiological mechanisms that regulate the nervous, muscular, skeletal, and endocrine systems. It explains how electrical and chemical signals coordinate body functions, movement, homeostasis, growth, and metabolism through interactions between neurons, muscles, bones, and hormones.

1. Neurophysiology

Neurophysiology is the study of the functional properties of the nervous system, including neurons, glial cells, and neural networks. The nervous system serves as the body's rapid communication network, controlling voluntary and involuntary activities while maintaining homeostasis. Unlike the endocrine system, neural communication is rapid and depends on electrical impulses.

Organization of the Nervous System

The course describes the central nervous system (CNS), emphasizing the brain as the control center responsible for integrating sensory information and coordinating body functions. Major brain regions include:

• Cerebrum
• Diencephalon
• Brain stem
• Cerebellum

Together these structures regulate movement, sensation, cognition, and autonomic functions.

2. Ion Channels and Membrane Physiology

Neuronal excitability depends on ion channels embedded within the plasma membrane.

Three major channel types are discussed:

• Voltage-gated channels
• Chemically activated (ligand-gated) channels
• Mechanically activated channels

These channels regulate the movement of sodium, potassium, calcium, and chloride ions according to electrochemical gradients, allowing neurons to generate electrical signals.

3. Resting Membrane Potential and Action Potential

Students learn how neurons generate electrical impulses.

Important concepts include:

• Resting membrane potential
• Potassium and sodium concentration gradients
• Selective membrane permeability
• Sodium-potassium pump
• Equilibrium potential
• Nernst equation

The course explains how depolarization reaches threshold, triggering an all-or-none action potential through rapid sodium influx followed by potassium-mediated repolarization and brief hyperpolarization.

4. Synaptic Transmission

Communication between neurons occurs at synapses.

The sequence includes:

1. Arrival of an action potential
2. Opening of voltage-gated calcium channels
3. Calcium influx
4. Synaptic vesicle fusion
5. Neurotransmitter release
6. Binding to postsynaptic receptors
7. Generation of excitatory or inhibitory responses

The course also introduces synaptic vesicle recycling through endocytosis.

5. Nerve Conduction

Action potentials travel along axons by local current spread.

Two types of nerve fibers are compared:

• Unmyelinated axons: slower conduction
• Myelinated axons: rapid saltatory conduction between Nodes of Ranvier

The physiological importance of myelin and the effects of demyelinating diseases such as Guillain-Barré syndrome and multiple sclerosis are highlighted.

6. Synaptic Integration and Neurotransmitters

Neurons integrate numerous incoming signals through:

• Spatial summation
• Temporal summation

Students study:

• Excitatory postsynaptic potentials (EPSPs)
• Inhibitory postsynaptic potentials (IPSPs)
• Feedback inhibition

Major neurotransmitters discussed include:

• Glutamate
• GABA
• Glycine
• Acetylcholine
• Monoamines
• Neuropeptides

The course also introduces receptor regulation, including receptor desensitization and up-regulation.

7. Skeletal System

The skeletal system provides:

• Body support
• Protection of organs
• Sites for muscle attachment
• Mineral storage
• Blood cell production

Students examine:

• Bone classifications
• Vertebral anatomy
• Joint types
• Cellular components of bone

Bone cells covered include:

• Osteoblasts
• Osteocytes
• Osteogenic cells
• Osteoclasts
• Bone-lining cells

Bone remodeling, fracture healing, cartilage types, and bone marrow functions are also discussed.

8. Skeletal Disorders

The course introduces common musculoskeletal disorders, including:

• Osteoarthritis
• Osteoporosis
• Bone fractures
• Disc herniation
• Scoliosis
• Anterior cruciate ligament (ACL) injury
• Medial collateral ligament (MCL) injury

Students learn the basic pathology and clinical significance of these conditions.

9. Muscular System

The muscular system performs several vital functions:

• Producing movement
• Maintaining posture
• Stabilizing joints
• Generating heat
• Moving substances throughout the body

Muscle tissue possesses four major physiological properties:

• Excitability
• Contractility
• Extensibility
• Elasticity

The course distinguishes among different muscle types and explains skeletal muscle organization from whole muscle to muscle fibers and sarcomeres.

10. Muscle Contraction

Students study the sliding filament theory of muscle contraction.

Topics include:

• Sarcomere organization
• Actin
• Myosin
• Troponin
• Tropomyosin
• ATP-dependent cross-bridge cycling

The course explains how contraction shortens sarcomeres without changing filament length.

11. Muscle Injuries and Disorders

Common muscular injuries covered include:

• Muscle strains
• Ligament sprains
• Muscle cramps
• Stress-induced muscle tension

Major neuromuscular diseases discussed include:

• Poliomyelitis
• Duchenne muscular dystrophy
• Becker muscular dystrophy
• Myasthenia gravis

The physiological basis of these disorders and their effects on muscle function are introduced.

12. Exercise Physiology

The course examines the beneficial effects of exercise on both skeletal and muscular systems.

Exercise contributes to:

• Stronger bones
• Improved joint mobility
• Increased cartilage thickness
• Greater muscle strength
• Enhanced endurance
• Stronger tendons
• Better posture
• Reduced injury risk

Different adaptations to high-intensity and endurance exercise are discussed.

13. Endocrine System

The endocrine system regulates long-term physiological processes through hormones.

Major endocrine organs include:

• Hypothalamus
• Pituitary gland
• Pineal gland
• Thyroid gland
• Parathyroid gland
• Thymus
• Adrenal glands
• Pancreas
• Ovaries
• Testes

Hormones act on distant target tissues to regulate metabolism, growth, reproduction, and homeostasis.

14. Hormone Classification and Mechanisms of Action

The course classifies hormones into:

• Peptide hormones
• Amine hormones
• Steroid hormones

Students learn two major mechanisms of hormone action:

• Peptide and amine hormones: bind membrane receptors and activate second messenger systems (e.g., cAMP and IP₃).
• Steroid hormones: diffuse into cells, bind intracellular receptors, and regulate gene transcription by interacting with DNA.

15. Endocrine Disorders

The course concludes with an overview of selected endocrine disorders, including:

• Diabetes mellitus
• Hypoglycemia
• Graves disease
• Goiter

These conditions illustrate the physiological consequences of hormone excess, deficiency, or impaired regulation.

Overall Learning Outcomes

By the end of this course, students should be able to:

• Explain the organization and physiological functions of the nervous system.
• Describe ion channel function, membrane potentials, and action potential generation.
• Explain synaptic transmission and neurotransmitter action.
• Describe nerve conduction in myelinated and unmyelinated fibers.
• Explain the structure and physiology of bones, joints, and skeletal muscles.
• Describe the molecular basis of muscle contraction using the sliding filament model.
• Identify common skeletal, muscular, and neuromuscular disorders.
• Explain the physiological adaptations of the musculoskeletal system to exercise.
• Describe the organization of the endocrine system and classify hormones.
• Compare the mechanisms of action of peptide, amine, and steroid hormones.
• Recognize common endocrine disorders and their physiological basis.