Muscle Contraction and Reflexes

Test Preparation Considerations

• Importance of considering schedules and events like Fox Day in academic planning.

• Assurance that with the remaining days, sufficient time exists to complete coursework.

Review of Previous Activities

Importance of Muscle Contraction in Health Programs

• Students planning for medical or health-related careers need to understand muscle contraction.

• Examples include:

  • Physical therapy necessitates knowledge of muscle function.

  • Even non-health-related majors can find this information beneficial.

Muscle Contraction and Movement

Key Terms and Concepts

• Muscle Contraction: Contraction results in movement.

• Reflexes: Involuntary responses to stimuli.

Examples of Reflexes

• Patellar Reflex: Tests the pathway of the muscle responsible for extending the knee.

• Coughing: Mechanism to eliminate irritants from airways.

• Sneezing: Another reflex that expels pathogens.

• Swallowing: A reflex developed from birth, essential for food intake.

Specific Reflexes Discussed

• Inhalation and Exhalation: Breathing patterns governed by muscle contraction.

• Eye Reflexes: Blinking controlled by circular and radial muscles of the iris and the ciliary muscles.

• Blood Pressure and Heart Function:

  • Blood pressure rises with arteriolar vasoconstriction.

  • Heart can constantly contract, exhibiting muscular involvement in involuntary functions.

Muscle Functions and Types

Skeletal Muscle

• Definition: Striated muscle attached to bones, allows voluntary movement.

• Tendons: Connective tissue attaching muscle to bone, structured with bundles of collagen.

• Muscle Fibers:

  • Motor neurons control multiple muscle fibers, allowing efficient contraction of the entire muscle simultaneously.

Control of Muscles by the Nervous System

• Central Nervous System: Controls skeletal muscle through motor neurons.

• Somatic Nervous System: Responsible for voluntary muscle movement.

• Homunculus: A distorted representation illustrating the degree of control by the brain over different body parts:

  • Larger size in certain areas indicates greater motor neuron control.

Types of Muscle According to Control

Cardiac and Smooth Muscles

• Cardiac Muscle: Found in the heart, involuntary control.

• Smooth Muscle: Found in organs and systems, also involuntary; controlled by the autonomic nervous system.

Autonomic Nervous System Functions

Sympathetic and Parasympathetic Responses

• Sympathetic Division: Activates 'fight or flight', increases heart rate, respiration; dilates airways.

• Parasympathetic Division: Activates 'rest and digest', slows heart rate, promotes digestion.

Specific Functions of Each Division

• Airway Responses:

  • Sympathetic: Airway dilates.

  • Parasympathetic: Airway constricts (radial muscles of the iris).

• Urinary System Reflex:

  • Micturition: Urination, controlled by smooth muscles in the urinary bladder.

Involuntary Urinary Responses

Mechanism of Urination

• When bladder is full, signals sent to the central nervous system signify pressure and the need for micturition.

• Reflex is autonomic, primarily parasympathetic.

• Inhibition during Anxiety: The anxiety response can stop urination.

Reproductive Reflexes

Mechanisms of Erection and Ejaculation

• Erection:

  • Controlled by a parasympathetic response involving increased blood flow.

• Ejaculation:

  • Sympathetic response characterized by stress, increased heart rate, and rapid physical response.

Physiological Response and Feedback Control

• Role of Hypothalamus: Acts as a thermostat, regulates body temperature and responses to infection (fever).

• Importance of Reflexes: Reflex mechanisms help maintain homeostasis and respond to environmental changes.

Summary of Homeostasis and Nervous System Interaction

• The body maintains balance (homeostasis) through communication between nervous system reflexes and physiological responses.

• Pathways for voluntary and involuntary control can influence physical and emotional states in a clinical setting.