Exam 3 study guide

Chapter 9: Muscles and Muscle Tissue

Key Concepts in Muscle Physiology

• Load, Tension, Isometric, Isotonic, Motor Unit:

  • Load: The force exerted by an object on a muscle.

  • Tension: The force generated by a muscle during contraction.

  • Isometric Contraction: Muscle generates tension without changing length.

  • Isotonic Contraction: Muscle changes length while moving a load (can be concentric or eccentric).

  • Motor Unit: A motor neuron and all the muscle fibers it innervates.

• Muscle Response to Increased Stimulation Frequency: Increasing the frequency of stimulation leads to summation of contractions, potentially resulting in tetanus (sustained contraction).

• Stronger Stimulus Application: More motor units are recruited, increasing the force of contraction.

• ATP Generation in Muscle (Muscle Metabolism):

  • ATP is generated by creatine phosphate breakdown, anaerobic glycolysis, and aerobic respiration.

• Factors Controlling Force of Muscle Contraction:

  • Number of muscle fibers stimulated

  • Size of muscle fibers

  • Frequency of stimulation

  • Degree of muscle stretch

• Muscle Fiber Types:

  • Slow Oxidative (fatigue-resistant, endurance)

  • Fast Oxidative (moderate resistance, intermediate speed)

  • Fast Glycolytic (fatigue quickly, powerful bursts)

• Skeletal Muscle Response to Exercise:

  • Endurance exercise increases capillaries, mitochondria, and myoglobin content.

  • Resistance exercise increases muscle fiber size (hypertrophy).

• Skeletal vs. Smooth Muscle:

  • Skeletal muscle is striated, voluntary, and attached to bones.

  • Smooth muscle is non-striated, involuntary, and found in walls of hollow organs.

• Smooth Muscle Features:

  • Contractions are slow and sustained.

  • Can contract even when stretched.

  • Regulated by autonomic nervous system, hormones, and local factors.

• Disuse Atrophy vs. Paralysis:

  • Disuse atrophy: Decrease in muscle size due to inactivity.

  • Paralysis: Loss of muscle function due to nervous system damage.

Chapter 11: Fundamentals of the Nervous System and Nervous Tissue

Nervous System Organization and Function

• Nervous System Organization:

  • Divided into Central Nervous System (CNS) and Peripheral Nervous System (PNS).

  • CNS: Brain and spinal cord; PNS: Cranial and spinal nerves.

• Neuroglia: Support cells in CNS (astrocytes, oligodendrocytes, microglia, ependymal cells) and PNS (Schwann cells, satellite cells).

• Neuron Structure and Function:

  • Cell body (soma), dendrites (receive signals), axon (transmits signals).

  • Classified by structure (multipolar, bipolar, unipolar) and function (sensory, motor, interneurons).

• Resting Membrane Potential:

  • Difference in electrical charge across the membrane at rest, typically -70 mV.

  • Maintained by sodium-potassium pump and selective permeability.

• Action Potential:

  • Rapid depolarization and repolarization of the membrane.

  • All-or-none event propagated along the axon.

  • Equation: $I = g(V_m - E_{ion})$ (current = conductance × driving force)

• Synaptic Transmission:

  • Neurotransmitters released from presynaptic neuron bind to receptors on postsynaptic neuron.

  • Can be excitatory or inhibitory.

• Neural Integration:

  • Summation of excitatory and inhibitory inputs determines if neuron will fire an action potential.

Chapter 12: The Central Nervous System

Brain Development and Structure

• Embryonic Development:

  • Neural tube forms primary brain vesicles: prosencephalon, mesencephalon, rhombencephalon.

  • These develop into adult brain structures: cerebrum, diencephalon, brainstem, cerebellum.

• Major Brain Regions:

  • Telencephalon: Cerebral hemispheres

  • Diencephalon: Thalamus, hypothalamus, epithalamus

  • Mesencephalon: Midbrain

  • Metencephalon: Pons, cerebellum

  • Myelencephalon: Medulla oblongata

• Cerebrospinal Fluid (CSF):

  • Produced by choroid plexus, circulates through ventricles, subarachnoid space, and central canal.

  • Functions: cushions brain, removes waste, provides nutrients.

• Brain Surface Anatomy:

  • Gyri: Ridges

  • Sulci: Grooves

  • Fissures: Deep grooves separating major brain regions

Cerebral Cortex and Functional Areas

• Cerebral Cortex:

  • Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory, understanding.

  • Divided into functional areas: motor, sensory, association.

• Functional Areas:

  • Primary motor cortex: Voluntary movement

  • Premotor cortex: Planning movements

  • Broca's area: Speech production

  • Primary somatosensory cortex: Receives sensory input

  • Somatosensory association cortex: Interprets sensory input

  • Visual, auditory, olfactory, gustatory, vestibular areas: Process respective sensory information

  • Prefrontal cortex: Cognition, personality, decision making

• Cerebral White Matter:

  • Consists of myelinated fibers: association, commissural, and projection fibers.

  • Association fibers: Connect different parts of the same hemisphere.

  • Commissural fibers: Connect corresponding areas of two hemispheres (e.g., corpus callosum).

  • Projection fibers: Connect cortex with lower brain or spinal cord.

• Basal Nuclei:

  • Subcortical nuclei involved in movement regulation, habit formation, and cognition.

Diencephalon and Brainstem

• Thalamus:

  • Relay station for sensory information to the cortex.

  • Inputs: sensory pathways; Outputs: cerebral cortex.

• Hypothalamus:

  • Regulates homeostasis, endocrine function, autonomic nervous system.

  • Contains nuclei controlling hunger, thirst, temperature, circadian rhythms.

  • Epithalamus: Contains pineal gland (secretes melatonin).

• Brainstem:

  • Includes midbrain, pons, medulla oblongata.

  • Controls basic life functions: heart rate, breathing, sleep, reflexes.

• Cerebellum:

  • Coordinates voluntary movements, balance, and posture.

Spinal Cord and Protection

• Spinal Cord Anatomy:

  • Extends from foramen magnum to L1/L2 vertebra.

  • Protected by vertebrae, meninges, and cerebrospinal fluid.

  • Gray matter (cell bodies) and white matter (myelinated axons).

• Ascending and Descending Pathways:

  • Ascending (sensory): Carry sensory information to the brain.

  • Descending (motor): Carry motor commands from brain to body.

• Spinal Cord Injury:

  • Damage can result in loss of sensation and/or motor function below the level of injury.

  • Complete transection results in total loss of function below injury.

• Blood-Brain Barrier:

  • Selective barrier that protects the brain from harmful substances while allowing passage of essential molecules.

Table: Comparison of Muscle Fiber Types

Fiber Type	Contraction Speed	Fatigue Resistance	Main ATP Source	Example
Slow Oxidative	Slow	High	Aerobic respiration	Postural muscles
Fast Oxidative	Fast	Intermediate	Aerobic (some anaerobic)	Leg muscles
Fast Glycolytic	Fast	Low	Anaerobic glycolysis	Arm muscles

Additional info:

• Some explanations and definitions were expanded for clarity and completeness.

• Table content inferred from standard muscle physiology knowledge.