Biology: Organism Response Mechanisms

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Questions and Answers

What is the role of the sinoatrial node (SAN) in the heart?

Initiates the electrical impulse for heartbeats (correct)

Regulates the contraction of skeletal muscles

Transmits nerve impulses to the brain

Filters blood through the renal system

Which factor affects the speed of nerve impulse conduction in myelinated axons?

The thickness of the axon

The presence of the myelin sheath (correct)

The release of calcium ions

The type of neurotransmitter released

What causes depolarization in a motor neurone?

Inhibition of sodium-potassium pump

Outflux of potassium ions

Net influx of sodium ions (correct)

Increased permeability to calcium ions

What occurs during the refractory period in nerve impulse transmission?

Neuron cannot generate another action potential Signup and view all the answers

Which event occurs specifically at a cholinergic synapse?

Temporal summation of signals Signup and view all the answers

What is the role of ATP in muscle contraction?

Facilitates the binding of actin and myosin Signup and view all the answers

What characterizes fast skeletal muscle fibers compared to slow fibers?

Faster contraction speed Signup and view all the answers

What is the primary role of Purkinje fibers in the heart?

To conduct electrical impulses rapidly Signup and view all the answers

What is the correct sequence of response to a stimulus in an organism?

Stimulus → Receptor → Coordinator → Effector Signup and view all the answers

How do nerve impulses differ from hormonal responses?

Nerve impulses are specific to a target cell and produce rapid responses. Signup and view all the answers

What role do growth factors play in flowering plants?

They regulate growth by moving from growing regions to other tissues. Signup and view all the answers

What is the primary function of a Pacinian corpuscle?

To detect specific types of mechanical stimuli. Signup and view all the answers

What occurs when a receptor is stimulated?

It results in the establishment of a generator potential. Signup and view all the answers

Which of the following statements best describes taxes and kineses?

They are simple movements that help organisms stay in favorable environments. Signup and view all the answers

What is necessary for visual acuity in humans?

Connections between rods and cones in the optic nerve. Signup and view all the answers

Which type of hormone response is characterized by being slow, long-lasting, and widespread?

Mammalian hormonal responses Signup and view all the answers

Study Notes

Organisms Responding to Internal and External Changes

A stimulus is a change in the internal or external environment.
A receptor detects the stimulus.
A coordinator processes the stimulus and formulates a response.
An effector carries out the response.
Receptors are specific to one type of stimulus.
Nerve cells transmit impulses rapidly, short-lived, and localized, releasing chemical messengers directly onto target cells.
Hormones work via the blood system, producing slow, long-lasting, widespread responses.
Plant responses use hormone-like growth substances.

Stimuli, Internal and External, Lead to Responses

Organisms respond to environmental changes to increase survival chances.
In flowering plants, growth factors move, influencing growth directionally.
Indoleacetic acid (IAA) affects cell elongation, causing gravitropism (growth in response to gravity) and phototropism (growth in response to light).
Taxes and kineses help mobile organisms maintain favorable environments.
Simple reflexes, exemplified by three-neuron reflexes, provide protective responses.

Receptors

Pacinian corpuscles are receptors that respond only to specific stimuli.
Stimulation of a receptor initiates a generator potential.
Pacinian corpuscles have a specific structure.
Deformation of sodium channels in Pacinian corpuscles creates a generator potential.
The human retina has rods and cones with different sensitivities to light and color, explaining visual acuity. Optical pigments and connections in the optic nerve are important aspects of vision.

Control of Heart Rate

Myogenic stimulation and electrical activity in the heart; sinoatrial node (SAN), atrioventricular node (AVN), Purkyne tissue, and bundle of His.
The roles of chemoreceptors and pressure receptors, and the autonomic nervous system in heart rate control.

Nervous Coordination: Nerve Impulses

Myelinated motor neuron structure.
Resting potential is related to differential membrane permeability and electrochemical gradients, notably sodium and potassium ions.
Changes in membrane permeability lead to depolarization and action potential generation.
The "all-or-none" principle describes action potentials.
Action potential passage along myelinated and unmyelinated axons.
Refractory period limits impulse frequency.
Factors influencing impulse speed include myelination, saltatory conduction, axon diameter, and temperature.

Synaptic Transmission

Synapse structure (including neuromuscular junction).
Sequence of events in cholinergic synapses (unidirectionality, temporal and spatial summation, inhibition).
Comparison between cholinergic synapse and neuromuscular junction.
Effects of drugs on synapses.

Skeletal Muscle Contraction

Muscles act antagonistically to move skeletons.
Gross and microscopic skeletal muscle structure, including myofibril ultrastructure.
Actin, myosin, calcium ions, and ATP drive myofibril contraction.
Calcium, tropomyosin, and troponin involvement in the actin-myosin bridge cycle.
ATP and phosphocreatine roles in muscle contraction.
Slow and fast skeletal muscle fibres and their properties.

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Description

This quiz explores how organisms respond to internal and external stimuli. It covers the roles of receptors, coordinators, and effectors in processing these stimuli. Additionally, it examines plant responses and the effects of hormones on growth and directionality.