ANP College Study Guide: Cell Membranes, Nervous System, Muscle, and Cardiovascular Physiology

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Cell Membranes and Introduction to Physiology

Introduction to Physiology

Physiology is the study of the normal functions of living organisms and their parts. It integrates molecular, cellular, tissue, and organ-level processes to explain how the body maintains homeostasis.

Homeostasis: The maintenance of a stable internal environment despite external changes.
Levels of Organization: Includes molecules, cells, tissues, organs, and organ systems.
Physiological Themes: Structure-function relationships, biological energy use, communication, and homeostasis.
Example: Regulation of blood glucose by insulin and glucagon.

Cell Membranes

The cell membrane is a selectively permeable barrier that separates the internal environment of the cell from the external environment. It is crucial for compartmentation, communication, and transport.

Structure: Composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.
Functions: Protection, selective transport, cell signaling, and cell adhesion.
Membrane Proteins: Include channels, carriers, receptors, and enzymes.
Example: Sodium-potassium pump maintains ion gradients across the membrane.

Membrane Dynamics

Membrane dynamics refer to the movement of substances across the cell membrane, including passive and active transport mechanisms.

Passive Transport: Includes diffusion, osmosis, and facilitated diffusion. No energy required.
Active Transport: Requires energy (ATP) to move substances against their concentration gradient.
Endocytosis and Exocytosis: Bulk transport mechanisms for large molecules.
Equation: Fick's Law of Diffusion:
Example: Glucose transport via GLUT proteins.

Nervous System

Neurons: Cellular and Network Properties

Neurons are specialized cells for communication within the nervous system. They transmit electrical and chemical signals to coordinate body functions.

Structure: Includes dendrites, cell body, axon, and synaptic terminals.
Action Potential: Rapid change in membrane potential that propagates along the axon.
Synaptic Transmission: Communication between neurons via neurotransmitters.
Equation: Nernst Equation:
Example: Acetylcholine release at neuromuscular junction.

The Central Nervous System

The central nervous system (CNS) consists of the brain and spinal cord. It processes sensory information and coordinates responses.

Brain Regions: Cerebrum, cerebellum, brainstem, and diencephalon.
Spinal Cord: Conducts signals between the brain and peripheral nerves.
Functions: Sensory processing, motor control, integration, and higher cognitive functions.
Example: Reflex arc in spinal cord.

Sensory Physiology

Sensory physiology explores how sensory information is detected, transduced, and processed by the nervous system.

Sensory Receptors: Specialized cells that detect stimuli (e.g., photoreceptors, mechanoreceptors).
Transduction: Conversion of stimulus energy into electrical signals.
Pathways: Sensory information travels via specific neural pathways to the CNS.
Example: Visual pathway from retina to occipital cortex.

Efferent Division: Autonomic and Somatic Motor Control

The efferent division of the nervous system controls voluntary and involuntary movements through somatic and autonomic pathways.

Somatic Motor: Controls skeletal muscle contraction.
Autonomic Motor: Regulates involuntary functions (e.g., heart rate, digestion).
Divisions: Sympathetic and parasympathetic nervous systems.
Example: Fight-or-flight response mediated by sympathetic nerves.

Muscle Physiology

Muscle Structure and Function

Muscle tissue is responsible for movement and force generation. There are three types: skeletal, cardiac, and smooth muscle.

Skeletal Muscle: Voluntary, striated, attached to bones.
Cardiac Muscle: Involuntary, striated, found in the heart.
Smooth Muscle: Involuntary, non-striated, found in walls of organs.
Example: Biceps brachii contracts to flex the elbow.

Muscle Contraction Mechanisms

Muscle contraction is initiated by electrical signals and involves the sliding filament theory.

Sliding Filament Theory: Actin and myosin filaments slide past each other to shorten the muscle.
Excitation-Contraction Coupling: Link between action potential and muscle contraction.
Equation: Force-Length Relationship:
Example: Calcium release triggers contraction in skeletal muscle.

Control of Body Movement

Body movement is controlled by neural circuits that coordinate muscle activity.

Motor Units: A motor neuron and all the muscle fibers it innervates.
Integration: CNS integrates sensory input and motor output.
Example: Walking involves coordinated activation of multiple muscle groups.

Cardiovascular Physiology

Heart Structure and Function

The heart is a muscular organ that pumps blood throughout the body. It consists of four chambers: two atria and two ventricles.

Cardiac Cycle: Sequence of events in one heartbeat, including systole and diastole.
Electrical Activity: Initiated by the sinoatrial (SA) node and propagated through the conduction system.
Equation: Cardiac Output:
Example: ECG records electrical activity of the heart.

Blood Flow and Pressure Regulation

Blood flow is regulated by vessel diameter, blood pressure, and resistance. The cardiovascular system maintains adequate perfusion to tissues.

Blood Pressure: Force exerted by blood against vessel walls.
Regulation: Baroreceptors detect changes in pressure and adjust heart rate and vessel tone.
Equation: Mean Arterial Pressure:
Example: Vasoconstriction increases blood pressure.

Blood Components

Blood consists of plasma, red blood cells, white blood cells, and platelets. It transports oxygen, nutrients, and waste products.

Plasma: Liquid component containing proteins, electrolytes, and hormones.
Red Blood Cells: Carry oxygen via hemoglobin.
White Blood Cells: Immune defense.
Platelets: Involved in clotting.
Example: Hematocrit measures the proportion of red blood cells in blood.

Summary Table: Types of Muscle Tissue

Type	Striated?	Voluntary?	Location
Skeletal	Yes	Yes	Attached to bones
Cardiac	Yes	No	Heart
Smooth	No	No	Walls of organs

Summary Table: Blood Components

Component	Main Function
Plasma	Transport nutrients, hormones, waste
Red Blood Cells	Oxygen transport
White Blood Cells	Immune defense
Platelets	Clotting

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