BIOL 316 Exam 2 Study Guide

BIOL 316 Exam 2 Study Guide

Students are responsible for all the material covered in lecture not just the topics provided below. Use this as a tool and a guide

CNS and PNS

Central Nervous System (CNS) and Peripheral Nervous System (PNS)

  • Centralization: Neurons are organized in central locations along the midline of the body.

  • Cephalization: Accumulation of a large number of neurons (the brain) in the head region.

  • Afferent vs Efferent Neurons:

    • Afferent Neurons: Carry sensory information toward the CNS.

    • Efferent Neurons: Carry information away from the CNS to effectors.

Reflex Arc Components

Understand the five components of a reflex arc and their designated functions:

  1. Receptor: Detects a stimulus.

  2. Afferent Neuron: Carries information to the CNS.

  3. Interneuron or Integrator: Processes the information.

  4. Efferent Neuron: Carries the response from the CNS to the effector.

  5. Effector: The muscle or gland that responds to the stimulus (third component of the arc).

Nervous System Organization

  • Afferent Division: Carries sensory information to the CNS.

  • CNS: Processes sensory information.

  • Efferent Division:

    • Somatic Nervous System: Responsible for voluntary control of muscles.

    • Autonomic Nervous System (ANS): Controls involuntary actions, divided into:

    • Sympathetic Nervous System (SNS): Responsible for the 'fight or flight' response.

    • Parasympathetic Nervous System (PNS): Responsible for 'rest and digest' functions.

    • Effectors:

    • Muscle: Cardiac, skeletal, and smooth muscle.

    • Exocrine glands: Release substances through ducts.

    • Endocrine glands: Release hormones into the bloodstream.

Regions of the Brain

Know the five regions of the brain and their functions:

  1. Telencephalon

  2. Diencephalon

  3. Mesencephalon

  4. Metencephalon

  5. Myelencephalon

Information Flow

Understanding how afferent and efferent information is processed within the nervous system is crucial.

Comparing the PNS and SNS

  • Sympathetic Nervous System (SNS):

    • PNS:

    • Long preganglionic and short postganglionic neurons.

    • Preganglionic neuron leaves the CNS from the craniosacral region.

    • Ganglion located at the target organ.

    • Neurotransmitter (NT) and receptors:

      • Pre-ganglionic: Acetylcholine.

      • Post-ganglionic: Acetylcholine at nicotinic receptors and muscarinic receptors on target organs.

    • SNS:

    • Short preganglionic and long postganglionic neurons.

    • Preganglionic neuron leaves the CNS from the thoracolumbar region.

    • Ganglion located in the paravertebral chain.

    • NT and receptors:

      • Pre-ganglionic: Acetylcholine.

      • Post-ganglionic: Norepinephrine at adrenergic receptors on target organs.

ANS Dual Innervation

  • Nearly all organs are under control by both PNS and SNS; they typically exert antagonistic control (one stimulates, the other inhibits).

  • Fight or Flight vs Rest and Digest: Understand the physiological differences between the two states.

  • Epinephrine Regulation by SNS: Explain how the SNS regulates the release and effects of epinephrine.

Biological Rhythms

Types of Biological Rhythms

  • Animals have biological rhythms to prepare for key events:

    • Infradian: Rhythms longer than a cycle (e.g., menstrual cycle).

    • Ultradian: Rhythms shorter than a day (e.g., feeding patterns).

    • Circadian: Daily rhythms (e.g., sleep-wake cycle).

    • Circannual: Yearly rhythms (e.g., migration).

Zeitgeber

  • Definition: A time giver, helping animals synchronize with their environment using reliable cues such as photoperiod or lunar cycles.

  • Importance of daily rhythms, demonstrating consistent patterns of wake and sleep.

  • Free-running: When an animal's internal clock is out of sync with external cues.

Suprachiasmatic Nucleus (SCN)

  • The master biological clock, synchronized across various tissues via external cues.

  • Biological clocks operate on cyclical gene expression. Activating light-inducible genes influences clock genes that regulate internal rhythms.

  • Increase in melatonin levels occurs in darkness, which influences clock gene expression.

Animal Experiments

  • Hamster Experiment: Observed that continuous light exposure resulted in the loss of the zeitgeber, leading to free-running rhythms beyond 24 hours, confirmed by actogram data.

  • Svalbard Ptarmigan: An example of an Arctic resident that can become arrhythmic in the absence of a zeitgeber, mimicking conditions in species with destroyed SCNs.

Endocrine System

Hormones

  • Peptide Hormones: Chains of amino acids that bind to cell membrane receptors.

  • Steroid Hormones: Derived from cholesterol, pass through cell membranes to bind intracellular receptors.

  • Amine Hormones: Derived from single amino acids, can bind to both membrane and intracellular receptors.

Hypothalamus and Pituitary Gland

  • Understand the anatomy and interconnections of the hypothalamus and pituitary gland.

  • Hormones of the Anterior Pituitary Gland: Understand their functions.

  • Posterior Pituitary Hormones:

    • Oxytocin: Initiates parturition and milk let-down.

    • Antidiuretic Hormone (AVP): Regulates water reabsorption in kidneys.

Hormonal Axis

  • Describe all hormones released from the hypothalamus, facilitating axes such as:

    • HPT Axis:

    • Thyrotropin releasing hormone (TRH) -> Thyroid stimulating hormone (TSH) -> Thyroid gland -> Thyroxine (T4) and Triiodothyronine (T3)

    • HPA Axis:

    • Corticotropin releasing hormone (CRH) + AVP -> Adrenocorticotropic hormone (ACTH) -> Adrenal cortex -> Cortisol (and also stimulates DHEA and aldosterone).

    • HPG Axis:

    • Gonadotropin releasing hormone (GnRH) -> Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH) -> Gonads -> Testosterone/Estradiol & gametogenesis.

    • HPS Axis:

    • Growth Hormone Releasing Hormone (GHRH) stimulates and Somatostatin (SST) inhibits growth hormone release -> Body organs -> Insulin-like Growth Factor (IGF-1).

    • HPM Axis:

    • Dopamine (from hypothalamus) -> Prolactin (from pituitary) -> Mammary tissue (no hormone release).

Skeletal Muscle

Types of Muscle Tissue

  • Three Types of Muscle Tissue:

    1. Skeletal Muscle: Voluntary control, striated.

    2. Cardiac Muscle: Involuntary control, striated.

    3. Smooth Muscle: Involuntary control, non-striated.

Sarcomere Structure

  • Definition of Sarcomere: Smallest functional unit of muscle; arranged end to end to form myofibrils.

  • Components:

    • A-Band: Dark area; overlapping actin and myosin filaments.

    • I-Band: Light area; only actin filaments.

    • M Line: Center of the sarcomere; anchors thick filaments (myosin).

    • H-Zone: Area of the A-band lacking actin filaments when the muscle is relaxed.

Sliding Filament Theory

  • The contraction process where myofilaments (myosin and actin) slide past each other. A-Bands remain constant while I-Bands and H-Zones decrease in width during contraction.

  • Cross-Bridge Cycling Process:

    • Activation at the neuromuscular junction (NT involved, receptors, and graded potentials).

    • Signal propagation through voltage-gated channels towards transverse tubules.

    • DHP and Ryanodine receptors regulate Ca2+ release from the sarcoplasmic reticulum (SR).

    • Ca2+ binds to troponin, shifting tropomyosin to unblock binding sites on actin filaments.

    • Ca2+ is then pumped back into the SR by the SERCA pump or expelled into interstitial fluid by PMCA.

Excitation-Contraction Coupling (ECC) Mechanism

  • Excitation: Electrical action potential triggers muscle contraction.

  • Contraction: Release of Ca2+ enables cross-bridge cycling and force generation.

Muscle Fiber Types

  • Three Fiber Types:

    1. Slow Oxidative (SO): Slow contraction; aerobic metabolism; resistant to fatigue.

    2. Fast Oxidative (FO): Moderate contraction; mixed metabolism.

    3. Fast Glycolytic (FG): Fast contraction; anaerobic; prone to fatigue.

Motor Unit

  • A motor unit consists of one motor neuron and all muscle fibers it innervates. Variability in size (1 to 1000s of muscle fibers) and fiber type.

  • Motor Unit Recruitment: Gradual recruitment of additional units to generate more force, favoring smaller units first (SO) before larger units (FG).

Muscle Contraction Types

  • Muscle Twitch: Force generated from a single excitation-contraction event.

  • Tetanic Contraction: Smooth and sustained contraction from a high rate of stimulation.

  • Temporal Summation: Increased force generation occurs when a motor neuron fires repeatedly, preventing muscle relaxation.

Aerobic Activity

Cost of Transport (COT)

  • Definition: Energy expenditure required for movement.

  • Comparison of locomotion types and influencing factors (gravity, medium, etc.):

    • Swimmers:

    • Gravity: Little impact; buoyancy reduces energy expenditure.

    • Medium: High viscosity; requires more energy to move through water.

    • Recovery Movement: None needed; limb movement aids in thrust generation.

    • Gait: Usually one type.

    • Fliers:

    • Gravity: Moderately impacted; they need to manage lift.

    • Medium: Minimal until reaching high speeds; can incur turbulent flow.

    • Recovery Movement: Necessary to elevate wings after each flap; consumes energy.

    • Gait: Primarily one type.

    • Runners:

    • Gravity: Greatly affects COT; must manage body weight with each contact.

    • Medium: Minimal impact from air.

    • Recovery Movement: Required for each step’s pendulum-like motion.

    • Gait: Three, e.g., walk, jog, run (also considered walking, trotting, galloping).

    • Transitioning gaits enhances efficiency and reduces transport costs.

Ranking COT

  • Ranking of locomotion forms in terms of COT:

    • Swimmers < Fliers < Runners

  • Understand how body size influences COT.

  • Distinguishing between laminar and turbulent flow:

    • Laminar Flow: Smooth, low-friction flow where layers pass an object with varying speeds.

    • Turbulent Flow: Chaotic, high-friction flow characterized by mixing and eddy currents.

Respiratory System

Gas Exchange

  • Knowledge of gas partial pressures and gradients is essential for respiration.

  • Henry's Law: Relates to gas solubility in liquids under pressure.

  • Fick’s Law: Describes diffusion across membranes as a function of surface area and partial pressure differences.

Respiratory Structures

  • Specialized structures:

    1. Lungs: Use tidal ventilation.

    2. Internal gills: Find in aquatic animals.

    3. External gills: Another adaptation for aquatic respiration.

    4. Skin: Non-specialized means of gas exchange (seen in some animals).

Ventilation Mechanisms

  • Three Ventilation Types:

    • Unidirectional: Specific flow direction through respiratory surfaces.

    • Nondirectional: Flow in multiple directions across surfaces.

    • Tidal: Air moves in and out (as with mammals).

  • Blood Flow Patterns:

    • Co-current: Blood flows with the medium.

    • Cross-current: Blood flows perpendicular to the medium.

    • Counter-current: Blood flows opposite to medium flow, maximizing gas exchange.

  • Gases move via convection and diffusion from external environments into tissues.

Efficiency of Gas Exchange

  • Oxygen extraction efficiencies ranked:

    • Insects > Fish > Birds > Mammals

  • Partial pressures at respiratory surfaces:

    • Fish: 160 mmHg > Insects: 150 mmHg = Birds: 150 mmHg > Mammals: 100 mmHg

  • Thickness of Respiratory Medium:

    • Insects: 0.01 µm < Fish: 0.1 µm = Birds: 0.1 µm < Mammals: 0.3 µm

Gas Transport in Blood

  • Gas Transport Mechanisms:

    • Dissolved in plasma.

    • Bound to hemoglobin (carbaminohemoglobin).

    • Reacts with water to form bicarbonate (HCO3-) and protons (H+).

Chemoreceptors

  • Monitor PO2, PCO2, and pH. Two types:

    • Peripheral Chemoreceptors:

    • Located in aortic arch and carotid sinus (for terrestrial animals) or in gill arches (for aquatic animals).

    • Respond primarily to changes in PO2.

    • Central Chemoreceptors:

    • Located in medulla oblongata.

    • Highly sensitive to PCO2 and pH due to blood-brain barrier permeability.

Respiratory Control Centers

  • Pre-Bötzinger Complex: Pacemaker center for respiratory rhythm.

  • Dorsal Respiratory Group (DRG): Drives inhalation.

  • Ventral Respiratory Group (VRG): Drives both inspiration and expiration.

Migration

Triggers and Tracking

  • Triggers for Migration: Photoperiod as a significant factor.

  • Tracking Small Songbird Migration: Geolocators measure sunrise/sunset times, providing unique location data for Migration paths.

  • Reasons for Migrating to Higher Latitudes:

    • Lower predation pressure.

    • Increased food availability (especially for insects).

    • Lesser competition with other species.

    • Longer photoperiods for offspring feeding.

    • Reduced parasites impacting reproduction.

Photostimulation and Detection

  • Photostimulation: Triggering biological systems (e.g., migration, reproduction) via increased day length (photoperiod).

  • Light Detection:

    • Eyes, Pineal gland, Deep brain photoreceptors (most significant for photostimulation).

Seasonal Changes in Breeding

  • Photorefractory: The process of turning biological systems off when photoperiod increases excessively.

  • Breeding Birds: Go through annual cycles of reproductive organ growth and regression.

Physiological Changes for Migration

  • Preparation involves:

    • Increasing fat reserves for energy during migration.

    • Muscle mass growth to enhance flight capability.

    • Hematocrit increase for improved oxygen transport.

    • Reduction in sleep to facilitate nocturnal migratory habits.