Human Biology Key Concepts: Nerves, Muscles, Systems

Posted on Mar 31, 2025 in Biology

Nervous System Fundamentals

  • Information relay to muscles: Motor neurons relay information from the brain and spinal cord to muscles.
  • Neuron resting potential: Approximately -70 millivolts for most neurons.
  • Motor neuron conducting zone: Includes the axon.
  • Sodium-potassium pump mechanism: Moves ions across the neuron membrane via active transport.
  • Resting membrane potential definition: The voltage difference between the inside and outside of a neuron’s plasma membrane.
  • Action potential nature: An all-or-nothing event.
  • First event in action potential: Sodium gates open.
  • Reflex arc synapse (sensory-motor): In a reflex arc, sensory neurons synapse directly on motor neurons.
  • Myelin sheath function: Wraps around an axon.
  • Neurotransmitter location: Found in the axon ending of a motor neuron.
  • Interneuron location: Found in the spinal cord.
  • Junction between neurons: A synapse.
  • Reflex arc synapse location: Occurs in the spinal cord between sensory and motor neurons.
  • Autonomic nervous system innervation: Innervates all except skeletal muscle.
  • Parasympathetic nervous system effect: Lowers blood pressure.

Brain Structure and Function

  • Cerebrum outer edge: The cerebral cortex.
  • Left hemisphere functions: Centers for analytical skills, speech, and mathematics reside here.
  • Brain ventricle contents: Filled with cerebrospinal fluid.
  • Control of conscious activities: Primarily controlled by the cerebrum.

General Nervous System Units

  • Basic units of nervous system: Neurons (structure and function).

Sensory Systems

  • Taste and smell receptors: Involve chemoreceptors.
  • Balance and body position: Maintained by semicircular canals and sacs in the inner ear.

Muscular System Essentials

  • Smooth muscle locations: Found in the walls of the stomach, intestines, and blood vessels.
  • Skeletal muscle function: Responsible for moving most parts of the body.
  • Sarcomere definition 1: The functional unit of muscle contraction; uses ATP; consists of myofibrils.
  • Flexor muscles function: Cause a joint to bend.
  • Skeletal muscle primary role: Moves the body.
  • Smallest muscle component listed: Myofibril.
  • Myofibril thick filaments: Composed of myosin.
  • Reason for skeletal muscle stripes: The arrangement of thick and thin filaments.
  • Sarcomere definition 2: Contains actin and myosin filaments parallel to its long axis; shortens during contraction; is the area between two Z lines.
  • Neuron-muscle communication site: Neuromuscular junction.
  • Sliding filament mechanism fact: When a muscle fiber is not contracting, the thin fibers are not connected to the thick fibers.
  • Sarcoplasmic reticulum contents: High concentration of calcium ions, which are released when an action potential stimulates it.
  • Filament composition: Myosin is part of the thick filaments; actin is part of the thin filaments.
  • Muscle relaxation mechanism: In skeletal and cardiac muscles, relaxation occurs as calcium ions are pumped back into the sarcoplasmic reticulum.
  • Smooth muscle example: Muscles of the uterus.

Integumentary and Skeletal Notes

  • Dermis contents: Contains nervous tissue and blood vessels.
  • Oil gland secretion: Sebum.
  • Sub-dermis fat cell non-function: Does not produce oil.
  • Hair and nail composition: Primarily keratin.
  • Bone storage: Stores phosphorus.
  • Bone-forming cells: Osteoblasts.

Circulatory System Facts

  • Non-white blood cell type: Erythrocyte (red blood cell).
  • Anemia characteristic: An abnormally low number of erythrocytes.
  • Cardiac pacemaker: The SA node.
  • Blood pressure variation: Highest in the arteries and lowest in the veins.
  • Oxygenated blood carrier: Pulmonary veins carry well-oxygenated blood.
  • Highest blood flow velocity: Found in the arteries.
  • Assertion: Cholesterol in blood is bound to proteins as HDLs. False. (Cholesterol circulates bound to various lipoproteins, including HDLs and LDLs).

Respiratory System Mechanics

  • Inspiration mechanism: Occurs when the diaphragm contracts and moves downward.
  • Oxygen transport in blood: Most is bound to hemoglobin.
  • Respiratory passage lining secretion: Mucus.
  • Vocal cord location: Located in the larynx.
  • Tiny air tubes in lungs: Bronchioles carry air to all parts of the lungs.
  • Nose and mouth air joining point: Pharynx.
  • Cause of exhalation: Relaxation of the diaphragm.
  • Epiglottis function: Prevents food from entering the airway.

Lymphatic System Roles

  • Non-lymphatic system part: Thyroid gland.
  • Organs with lymphatic vessels: Lymph nodes are small organs associated with lymphatic vessels.
  • Lymphatic system functions:
    • Reabsorbing fluid lost from the capillaries and transporting it to the blood.
    • Absorbing fats from the digestive system.
    • Defending the body against infectious disease.