Topic 6 - Response to stimuli Flashcards
Survival response
Organisms adapt to environmental changes for survival.
Taxis
Movement towards or away from a stimulus.
Negative phototaxis
Movement away from light, e.g., earthworms.
Positive phototaxis
Movement towards light, e.g., single-celled algae.
Kineses
Non-directional movement rate change in response to stimuli.
Stimulus intensity
Higher intensity increases the rate of kineses.
Tropisms
Directional growth response to environmental stimuli.
Positive phototropism
Plant shoots grow towards light for photosynthesis.
Positive gravitropism
Plant roots grow towards gravity for stability.
Positive hydrotropism
Roots grow towards water for absorption.
Plant growth factors
Chemicals like IAA that influence plant growth.
IAA (Indole-3-acetic acid)
Plant hormone causing differential growth responses.
Unequal growth
Causes bending towards or away from stimuli.
Reflex action
Unconscious, rapid response to a stimulus.
Reflex arc
Pathway involving sensory, intermediate, and motor neurones.
Receptors
Cells detecting environmental changes and stimuli.
Sensory neurones
Carry impulses from receptors to coordinators.
Coordinator
Processes impulses, either spinal cord or brain.
Motor neurones
Transmit impulses to effectors like muscles or glands.
Effectors
Muscles or glands responding to motor neurone signals.
Myelinated motor neurone
Neurone with myelin sheath for faster impulse conduction.
Dendrons
Extensions conducting impulses towards the neurone cell body.
Dendrites
Subdivisions of dendrons receiving impulses from other neurones.
Axons
Extensions conducting impulses away from the neurone cell body.
Myelin sheath
Insulating layer formed by Schwann cells around axons.
Nodes of Ranvier
Gaps in myelin sheath allowing ion movement.
Schwann cells
Cells forming the myelin sheath around axons.
Neurone
Cell that transmits electrical impulses.
Cations
Positively charged ions involved in impulse transmission.
Resting potential
Potential difference of -70mV in inactive neurone.
Sodium-potassium pump
Transports 3 Na+ out, 2 K+ in actively.
Concentration gradient
Difference in ion concentration across the membrane.
Facilitated diffusion
Passive movement of ions through channel proteins.
Channel proteins
Proteins that allow specific ion passage through membranes.
Polarised membrane
More positive ions outside than inside the neurone.
Action potential
Rapid change in membrane potential to +40mV.
Voltage-gated Na+ channels
Channels that open in response to membrane stimulation.
Depolarised membrane
Higher concentration of positive ions inside the axon.
Threshold value
Minimum stimulus level to generate an action potential.
Generator potential
Change in potential difference due to stimulus strength.
All or nothing principle
Action potential size is independent of stimulus strength.
Frequency of impulses
Indicates strength of the stimulus received.
Repolarisation
Restoration of resting potential after depolarisation.
K+ ion channels
Channels that open to allow K+ out of axon.
Refractory period
Time when axon cannot depolarise after action potential.
Myelin sheath
Insulating layer that speeds up impulse transmission.
Node of Ranvier
Gaps in myelin sheath for ion exchange.
Impulse transmission
Movement of electrical signals along neurones.
Ion diffusion
Movement of ions across membranes affecting potential.
Stimulus
Change in environment triggering neurone response.
Positive ions
Ions with a net positive charge, e.g., Na+.
Negative ions
Ions with a net negative charge, e.g., Cl-.
Action potential propagation
Wave of depolarisation moving along the axon.
Concentration of Na+
Higher outside the cell at resting potential.
Concentration of K+
Higher inside the cell at resting potential.
Saltatory conduction
Impulse jumps between nodes, speeding transmission.
Temperature effect
Higher temperature increases ion diffusion rate.
Axon diameter
Thicker axons reduce ion leakage.
Synapse
Junction between two neurons for impulse transmission.
Acetylcholine
Common neurotransmitter in cholinergic synapses.
Cholinergic synapse
Synapse using acetylcholine as a neurotransmitter.
Action potential
Electrical signal triggering neurotransmitter release.
Synaptic knob
End of neuron where neurotransmitters are released.
Calcium ions
Trigger neurotransmitter release into synaptic cleft.
Synaptic vesicles
Carry neurotransmitters to the presynaptic membrane.
Post-synaptic membrane
Membrane receiving neurotransmitters from synaptic cleft.
Sodium ions
Cause depolarization in post-synaptic neurone.
Threshold value
Minimum depolarization needed to initiate action potential.
Acetylcholinesterase
Enzyme breaking down acetylcholine in synaptic cleft.
Neuromuscular junction
Synapse between motor neurone and muscle fibre.
Sarcolemma
Post-synaptic membrane of muscle fibre.
Unidirectionality
Synapses transmit impulses in one direction only.
Summation
Combining potentials to exceed threshold for action potential.
Spatial summation
Multiple neurones converge to exceed threshold.
Temporal summation
High frequency from one neurone exceeds threshold.
Inhibitory synapse
Neurotransmitter makes post-synaptic neurone less likely to fire.
Chloride ions
Negatively charged ions entering neurone during inhibition.
Drug effects
Drugs can mimic or block neurotransmitter action.
Neurotransmitter binding
Transmitter attaches to receptors on post-synaptic membrane.
Action potential production
Triggered by sufficient depolarization in post-synaptic neurone.
Neurotransmitter reabsorption
Process of recycling neurotransmitters after action.
Impulse transmission speed
Influenced by axon diameter and temperature.
Chemical transmitters
Substances that carry impulses across synaptic gaps.
Acetylcholinesterase
Enzyme that breaks down acetylcholine in synapses.
Pacinian corpuscle
Receptor responding specifically to mechanical pressure.
Generator potential
Change in membrane potential due to stimulus.
Threshold value
Minimum stimulus required to trigger action potential.
Rods
Photoreceptors sensitive to low light conditions.
Rhodopsin
Pigment in rods that detects light.
Retinal
Light-sensitive molecule derived from rhodopsin.
Opsin
Protein component of rhodopsin involved in vision.
Iodopsin
Pigment in cones that responds to bright light.
Cones
Photoreceptors responsible for color vision and acuity.
Fovea
Area of retina with high cone concentration.
Blind spot
Area without photoreceptors where optic nerve exits.
Sensitivity
Ability to see in low light intensities.
Spatial summation
Combined input from multiple cells to exceed threshold.
Visual acuity
Ability to resolve two separate stimuli distinctly.
Bipolar cell
Neuron connecting photoreceptors to ganglion cells.
Action potential
Electrical signal transmitted along neurons.
Mitochondria
Organelles providing energy for cellular processes.
Lamellae
Membrane discs in rods containing rhodopsin.
Bleaching
Process of rhodopsin breaking down in light.
High light intensity
Condition under which iodopsin is activated.
Low light intensity
Condition under which rods are primarily active.
Cone cells
Photoreceptors functioning in bright light conditions.
Photoreceptors
Cells in the retina that detect light.
Trichromatic theory
Theory explaining color vision via three cone types.
Convergence
Process where multiple cells connect to a single neuron.
Generator potential size
Proportional to the magnitude of the stimulus.
Iodopsin
Pigment sensitive to specific light wavelengths.
450nm
Wavelength for blue light sensitive iodopsin.
520nm
Wavelength for green light sensitive iodopsin.
580nm
Wavelength for red light sensitive iodopsin.
Cone cells
Photoreceptors for color vision in the retina.
Rod cells
Photoreceptors for black and white vision.
Visual cortex
Brain region interpreting visual information.
Action potentials
Electrical impulses sent by stimulated cones.
Sino-atrial node (SAN)
Pacemaker generating impulses in the heart.
Atria
Upper chambers of the heart contracting first.
Atrioventricular node (AVN)
Delays impulse before ventricle contraction.
Purkyne fibres
Conductive muscle fibres transmitting impulses to ventricles.
Bundles of His
Pathway for impulses to ventricles from AVN.
Cardiac output
Volume of blood pumped by the heart per time.
Stroke volume
Volume of blood pumped per heartbeat.
Heart rate
Number of heartbeats per minute.
Cardiac output formula
Cardiac output = stroke volume x heart rate.
Autonomic Nervous System
Regulates involuntary body functions.
Sympathetic nervous system
Prepares body for fight or flight response.
Parasympathetic nervous system
Counteracts sympathetic effects, promoting rest.
Noradrenaline
Neurotransmitter increasing heart rate and bronchodilation.
Acetylcholine
Neurotransmitter decreasing heart rate.
Cardioinhibitory centre
Decreases heart rate via parasympathetic impulses.
Cardioacceleratory centre
Increases heart rate via sympathetic impulses.
Chemoreceptors
Detect carbon dioxide levels in blood.
Medulla oblongata
Brain region coordinating autonomic functions.
Ventricles
Lower heart chambers contracting after atria.
Impulse conduction
Process of transmitting electrical signals through heart.
Pressure receptors
Detect blood pressure changes in arteries.
Cardioacceleratory centre
Regulates heart rate via nerve impulses.
Sino-atrial node
Heart’s natural pacemaker regulating impulses.
Muscle fibres
Hundreds of cells composing muscle tissue.
Myofibrils
Subunits within muscle fibres containing sarcomeres.
Sarcomeres
Repeating units in myofibrils facilitating contraction.
Actin
Thin filaments involved in muscle contraction.
Myosin
Thick filaments that interact with actin.
I band
Light band of actin only in sarcomeres.
H zone
Dark band of myosin only in sarcomeres.
A band
Region of overlapping actin and myosin.
Sliding filament theory
Mechanism explaining muscle contraction via filament sliding.
Myosin binding site
Location on actin for myosin attachment.
Power stroke
Myosin head movement propelling actin filaments.
Recovery stroke
Myosin head detachment and repositioning after contraction.
ATP hydrolysis
Process providing energy for muscle contraction.
Sarcolemma
Membrane surrounding muscle fibres.
Calcium ions
Trigger muscle contraction by binding to proteins.
Tropomyosin
Protein regulating access to myosin binding sites.
ATPase enzyme
Enzyme hydrolyzing ATP for energy release.
Anaerobic conditions
State when oxygen supply is insufficient during exercise.
Immediate contraction
Initial muscle response using stored ATP.
Energy supply
ATP hydrolysis powers muscle movement and calcium transport.
Strenuous exercise
High-intensity activity increasing oxygen demand.
Impulses frequency increase
Response to elevated carbon dioxide levels.
Blood flow increase
Enhances carbon dioxide removal from lungs.
Carbon dioxide levels normalization
Restoration of homeostasis post-exercise.
Phosphocreatine
Molecule producing ATP without respiration in muscles.
ATP
Energy currency of the cell, adenosine triphosphate.
ADP
Adenosine diphosphate, precursor to ATP.
Aerobic conditions
Oxygen-rich environment supporting cellular respiration.
Fast twitch fibers
Muscle fibers for rapid, powerful contractions.
Slow twitch fibers
Muscle fibers for endurance and posture maintenance.
Myosin filaments
Thick filaments in muscle fibers aiding contraction.
Myoglobin
Oxygen-storing pigment in muscle tissue.
Glycogen
Stored form of glucose in muscles and liver.
Mitochondria
Organelles producing ATP through aerobic respiration.
Homeostasis
Maintenance of stable internal environment in organisms.
Negative feedback
Process reversing deviations from set levels.
Blood glucose concentration
Level of glucose in blood, ideally 80mg/100ml.
Hypertonic
Solution with higher solute concentration than cells.
Insulin
Hormone lowering blood glucose levels by promoting uptake.
Glycogenesis
Conversion of glucose to glycogen in liver cells.
Adipose tissue
Body fat storing excess energy as fat.
Glucagon
Hormone raising blood glucose levels by promoting release.
Glycogenolysis
Breakdown of glycogen into glucose.
Adrenaline
Hormone stimulating glycogenolysis during stress.
Gluconeogenesis
Production of glucose from non-carbohydrate sources.
Islets of Langerhans
Pancreatic cells regulating blood sugar through hormones.
Receptors
Proteins detecting changes in internal environment.
Effectors
Cells or organs executing responses to stimuli.
Respiration
Process converting glucose into usable energy.
Osmosis
Movement of water across a semi-permeable membrane.
Lactic acid
Byproduct of anaerobic respiration in muscles.
Glycerol
Component of fats, used in gluconeogenesis.
Amino acids
Building blocks of proteins, used in prolonged fasting.
Second Messenger
Molecule that transmits signals inside cells.
First Messenger
Hormone that binds to cell receptors.
Hormone-Receptor Complex
Binding of hormone to its specific receptor.
Adenylate Cyclase
Enzyme converting ATP to cyclic AMP.
Cyclic AMP (cAMP)
Second messenger activating protein kinases.
Protein Kinase
Enzyme that phosphorylates proteins, altering function.
Cascade Effect
Single hormone triggers multiple enzyme activations.
Tertiary Structure
Three-dimensional shape of a protein.
Diabetes
Disease affecting blood glucose regulation.
Type I Diabetes
Insulin-dependent; pancreas fails to produce insulin.
Type II Diabetes
Insulin-independent; cells resist insulin action.
Nephron
Functional unit of the kidney.
Ultrafiltration
Process filtering blood in the nephron.
Glomerulus
Capillary network where ultrafiltration occurs.
Bowman’s Capsule
Structure surrounding glomerulus, collects filtrate.
Glomerular Filtrate
Fluid filtered from blood into nephron.
Selective Reabsorption
Process returning useful substances to blood.
Proximal Convoluted Tubule
Site for glucose and ion reabsorption.
Counter Current Multiplier
Mechanism creating concentration gradients in kidneys.
Osmoregulation
Regulation of water potential in blood.
Osmoreceptors
Cells detecting changes in blood water potential.
ADH (Antidiuretic Hormone)
Hormone increasing kidney water reabsorption.
Collecting Duct
Nephron section regulating final water absorption.
Distal Convoluted Tubule
Nephron section involved in ion and water reabsorption.
Renal Artery
Blood vessel supplying kidneys with blood.
Urea
Waste product excreted in urine.
Water Potential
Measure of water concentration in solutions.
Action Potentials
Electrical signals sent by osmoreceptors.
Negative Feedback
Process maintaining homeostasis by counteracting changes.
Mitochondria
Organelles providing energy for active transport.
Microvilli
Cellular structures increasing absorption surface area.
Filtrate Concentration
Concentration of substances in nephron filtrate.
Urine Production
Excretion of waste products from the body.
