Muscular System

Functions and Organization of Muscle Tissue

The muscular system is essential for movement, posture, and energy metabolism. Muscles contract to produce force, generate heat, and store energy.

• Functions of a muscle: Contraction, energy/heat production, energy storage.

• Organization of a muscle: Muscles are composed of fascicles, fibers, myofibrils, and filaments. Each level contributes to the overall function and structure.

• Myofilaments: The main types are actin (thin) and myosin (thick), which interact during contraction. Other proteins include tropomyosin and troponin.

• Differences between skeletal, cardiac, and smooth fibers: Skeletal muscle is voluntary and striated, cardiac muscle is involuntary and striated, and smooth muscle is involuntary and non-striated.

• Connective tissue coverings: Muscles are surrounded by connective tissue layers: epimysium (outer), perimysium (around fascicles), and endomysium (around fibers).

Muscle Structure and Contraction

• Definitions and functions: Sarcolemma (muscle cell membrane), sarcoplasm (cytoplasm), sarcoplasmic reticulum (stores calcium), myoglobin (oxygen storage).

• Sarcomere structure: The basic contractile unit, defined by Z lines. Contains A band, I band, and H zone.

• Neuromuscular junction: Site where motor neuron communicates with muscle fiber, involving neurotransmitters like acetylcholine.

• Neurotransmitter action: Acetylcholine binds to receptors, causing sodium influx and muscle contraction.

• Why ATP and calcium are necessary: ATP provides energy for contraction; calcium triggers the interaction between actin and myosin.

• Sequence for muscular contraction: Action potential → calcium release → actin-myosin interaction → contraction.

• Cellular respiration: Muscles use anaerobic and aerobic pathways to produce ATP.

Example: During exercise, skeletal muscles use stored glycogen for rapid ATP production via anaerobic respiration, then switch to aerobic metabolism for sustained activity.

Nervous System - General and Special Senses

Overview and Organization

The nervous system coordinates body activities through electrical and chemical signals. It consists of the central and peripheral divisions, each with specialized functions.

• Structure of the Nervous System: Includes receptors (detect stimuli), processors (integrate information), and effectors (respond).

• Muscles in the Nervous System: CNS organs include the brain and spinal cord.

• Meninges: Protective layers: dura mater, arachnoid mater, pia mater.

• Peripheral Nervous System (PNS): Consists of nerves and ganglia outside the CNS.

• Autonomic and Somatic Divisions: Autonomic controls involuntary functions; somatic controls voluntary movements.

• Sympathetic and Parasympathetic: Sympathetic prepares for 'fight or flight'; parasympathetic for 'rest and digest'.

• White and Gray Matter: White matter contains myelinated axons; gray matter contains neuron cell bodies.

• Cell Types: Neurons (transmit signals) and neuroglia (support cells).

• Neuron Structure: Dendrites (receive signals), cell body (processes), axon (transmits), terminal (communicates with next cell).

• Types of Neurons: Sensory, interneuron, motor; classified by shape (unipolar, bipolar, multipolar).

• Connective tissue coverings: Epineurium (outer), perineurium (fascicle), endoneurium (fiber).

Neural Signaling and Special Senses

• Resting potential: Difference in charge across the neuron membrane at rest.

• Action potential: Rapid change in membrane potential, leading to nerve impulse.

• Synapse: Junction between neurons; neurotransmitters mediate signal transmission.

• Primary motor and sensory areas: Located in the cerebral cortex; control movement and sensation.

• Brainstem functions: Controls heart rate, water balance, body temperature.

• Brain areas: Hand, emotion, hearing, heart rate, vasoconstriction.

• Cranial nerves: Twelve pairs, each with specific sensory, motor, or mixed functions.

Example: The optic nerve (cranial nerve II) transmits visual information from the retina to the brain.

Endocrine System

Hormones and Endocrine Glands

The endocrine system regulates physiological processes through hormones secreted by glands. Hormones can be classified by structure and function.

• Hormones: Chemical messengers that regulate metabolism, growth, and homeostasis.

• Classification: Steroid hormones (lipid-based), peptide hormones (protein-based).

• Endocrine glands: Include pituitary, thyroid, adrenal, pancreas, etc.

• Peptide hormones: Synthesized from amino acids; act on cell surface receptors.

• Steroid hormones: Derived from cholesterol; act on intracellular receptors.

Major Hormones and Functions

• Pituitary hormones: Adenohypophysis (anterior) and neurohypophysis (posterior) secrete hormones controlling growth, reproduction, and metabolism.

• Adrenal cortex and medulla: Cortex produces mineralocorticoids, glucocorticoids; medulla produces catecholamines (epinephrine, norepinephrine).

• Functions of ACTH, cortisol, aldosterone, epinephrine: ACTH stimulates cortisol release; cortisol regulates metabolism and immune response; aldosterone controls sodium balance; epinephrine triggers 'fight or flight'.

• Relation of cortisol with immune system: Cortisol suppresses inflammation and immune activity.

• Insulin and glucagon: Regulate blood glucose; insulin lowers, glucagon raises.

• Diabetes mellitus: Type 1 (autoimmune destruction of insulin-producing cells), Type 2 (insulin resistance). Both affect insulin production and glucose regulation.

Example: In response to high blood glucose, the pancreas releases insulin to promote glucose uptake by cells.

Key Table: Comparison of Hormone Types

Key Equations

• Resting membrane potential:

• ATP production (cellular respiration):

• Glucose regulation:

Additional info: Academic context and expanded explanations have been added to ensure completeness and clarity for exam preparation.