A2 Biology Chapter 1: Coordination and Response

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Questions and Answers

What is the primary function of the cell body in a motor neuron?

It conducts impulses away from the cell body.

It contains the nucleus and synthesizes proteins and neurotransmitters. (correct)

It provides insulation around the axon.

It carries impulses from other neurons towards the axon.

Which component of a motor neuron is responsible for carrying impulses toward the cell body?

Myelin sheath

Dendrites (correct)

Axon

Nodes of Ranvier

What role does the myelin sheath play in nerve conduction?

It promotes the growth of new neurons.

It carries impulses directly to muscle fibers.

It releases neurotransmitters at the synapse.

It speeds up nerve conduction and provides insulation. (correct)

What are the nodes of Ranvier?

Gap areas between Schwann cells along the axon. Signup and view all the answers

How do sensory receptors function in terms of energy conversion?

They transduce energy into receptor potential. Signup and view all the answers

What triggers the generation of an action potential along a sensory neuron?

Release of neurotransmitter exceeding the threshold. Signup and view all the answers

What is a characteristic difference between relay neurons and other neurons?

Relay neurons are not myelinated. Signup and view all the answers

Which of the following options correctly describes a receptor cell?

They initiate action potentials in response to stimulation. Signup and view all the answers

What is the primary function of chemoreceptors in taste buds?

To sense various chemicals in food and beverages Signup and view all the answers

Which of the following statements about sodium ion chemoreceptors is true?

They allow sodium ions to diffuse through specific channel proteins Signup and view all the answers

What role does cyclic AMP play in the sweet taste pathway?

It serves as a second messenger in the cellular signaling cascade Signup and view all the answers

What is the typical resting potential of an axon?

Between −60 mV and −70 mV Signup and view all the answers

How is an action potential generated in a sensory neuron from a receptor potential?

If the receptor potential reaches a sufficient threshold value Signup and view all the answers

What is the role of synapses in memory and learning?

They link neurons involved in passing information. Signup and view all the answers

What effect does the closure of potassium ion channels have on the membrane?

It leads to depolarization of the membrane Signup and view all the answers

Which component is not part of the striated muscle structure?

Neurotransmitter receptors Signup and view all the answers

What does the all-or-nothing law describe?

Full initiation of action potential once the threshold is met. Signup and view all the answers

What best describes the structure of a muscle fiber?

Multinucleated syncytium with organized contractile proteins. Signup and view all the answers

Which of the following is NOT a taste detected by chemoreceptors in taste buds?

Spicy Signup and view all the answers

What type of taste sensation is associated with umami?

Savoury flavor from certain amino acids Signup and view all the answers

What is the primary function of the sarcoplasmic reticulum in muscle fibers?

To transport calcium ions. Signup and view all the answers

How does the frequency of impulses change with varying stimulus intensity?

It increases with higher intensity stimuli. Signup and view all the answers

What is the role of the M line in a sarcomere?

Anchors the thick filaments Signup and view all the answers

Why does action potential amplitude remain constant along the axon?

It is maintained by ion channel activity. Signup and view all the answers

What is the primary function of the sarcoplasmic reticulum in muscle contraction?

To store and release calcium ions Signup and view all the answers

What role do T-tubules play in muscle fibers?

Carry action potentials into the muscle cell. Signup and view all the answers

What event causes the myosin binding sites on actin filaments to become exposed?

Calcium ions binding to troponin Signup and view all the answers

Which component primarily forms the thick filaments in muscle fibers?

Myosin Signup and view all the answers

What is the function of tropomyosin in muscle fibers?

To block myosin binding sites on actin during relaxation Signup and view all the answers

Which structure is NOT part of a sarcomere?

T-tubule Signup and view all the answers

What initiates the process of muscle contraction at the neuromuscular junction?

Release of neurotransmitters from the motor neuron Signup and view all the answers

Which protein component is responsible for the energy release during muscle contraction?

Myosin Signup and view all the answers

What is the main function of sensory receptor cells in the detection of stimuli?

To detect changes in the internal and external environment Signup and view all the answers

Which structure is crucial for the fast transmission of nerve impulses in myelinated neurons?

Myelin sheath Signup and view all the answers

What role do calcium ions play in the functioning of a cholinergic synapse?

They trigger the release of neurotransmitters into the synaptic cleft Signup and view all the answers

Which part of the reflex arc is responsible for transmitting information to muscles?

Motor neuron Signup and view all the answers

In the sliding filament model of muscular contraction, which proteins are primarily involved?

Myosin and actin Signup and view all the answers

What is the primary effect of auxin on plant cells during growth?

Stimulates proton pumping and cell elongation Signup and view all the answers

What is the main function of the sarcoplasmic reticulum in striated muscle contraction?

It stores and releases calcium ions Signup and view all the answers

How does the myelin sheath affect the frequency of nerve impulses?

It allows for faster impulses, thus increasing frequency Signup and view all the answers

Study Notes

Communication Systems

Nervous and endocrine systems coordinate responses to internal and external changes.
The nervous system is fast, using electrical impulses, while the endocrine system relies on hormones for slower responses.

Neuron Structure

Sensory Neurons: Transmit impulses from sensory receptors to the CNS.
Motor Neurons: Carry impulses from the CNS to effectors.
Relay Neurons: Connect sensory and motor neurons within the CNS.

Sensory Receptor Cells

Detect stimuli and stimulate nerve impulse transmission.
Example: Chemoreceptor cells in human taste buds respond to chemical stimuli.

Reflex Arc Functions

Sensory neurons detect stimuli, relay neurons process information, and motor neurons execute responses.

Action Potential Transmission

Initiated from resting potential (-60 to -70 mV).
Sodium (Na⁺) and potassium (K⁺) ions play crucial roles in impulse transmission.
Myelinated neurons increase impulse speed through saltatory conduction.

Myelin Sheath

Formed by Schwann cells wrapping around axons, aiding speed and insulation.
Nodes of Ranvier are crucial for rapid impulse transmission.

Cholinergic Synapse Structure

Involves neurotransmitter release, with calcium ions triggering exocytosis for signal transmission.

Synapse Functions

Permit unidirectional transmission and facilitate connections between multiple neurons.

Neuromuscular Junctions

Interfaces between motor neurons and muscle fibers, essential for muscle contraction initiation.

Striated Muscle Structure

Composed of muscle fibers (syncytium) containing organized contractile proteins.
Sarcomeres are the fundamental contractile units, structured between Z lines.

Sliding Filament Model

Myosin and actin filaments slide past each other during contraction.
Calcium ions bind to troponin, triggering conformational changes that expose binding sites on actin.

Venus Flytrap Mechanism

Rapid closure in response to hair stimulation, achieving trap closure via fluid movement.

Growth Regulation by Auxin

Auxin promotes cell elongation by stimulating proton pumps, acidifying cell walls.

Gibberellin Role in Germination

Gibberellin facilitates germination processes in grains like wheat and barley.

Action Potential Characteristics

All-or-nothing law: Action potentials occur only if the threshold is surpassed.
Intensity of stimuli is encoded by the frequency and number of neurons firing, not the magnitude of each action potential.

Structure of Sarcomere

A Band: Overlapping myosin and actin filaments, darker region.
I Band: Only actin filaments, lighter region.
H Band: Myosin only, lighter area within the A band.
Z Line: Attachment point for actin filaments.

Myosin and Actin Composition

Myosin: Thick filaments with fibrous protein structure, globular heads for binding.
Actin: Thin filaments composed of globular proteins twisted together with tropomyosin and troponin.

Mechanism of Muscle Contraction

Action potentials trigger calcium release from the sarcoplasmic reticulum, facilitating muscle contraction through the sliding filament mechanism involving ATP utilization.

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Description

This quiz covers the key concepts from Chapter 1 of A2 Biology, focusing on coordination and response in living organisms. Explore the comparison between the nervous and endocrine systems, and understand how they facilitate communication in response to environmental changes.