Human Nervous System and Taste
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Questions and Answers

What is the primary function of chemoreceptors in humans?

  • Responding to thermal changes
  • Detecting chemical stimuli (correct)
  • Interpreting visual information
  • Recognizing mechanical stimuli

    • Humans possess around 1,000 chemoreceptor cells in their taste buds.

    False

    What are the five basic tastes that taste buds can detect?

    Sweet, sour, salty, umami, bitter

    Dissolved chemicals from food enter the taste bud through the taste pore and bind to the receptor cells, causing a change in the shape of the ______.

    <p>chemoreceptor protein</p> Signup and view all the answers

    Match the following components with their roles in taste sensation:

    <p>Taste buds = Detect taste Microvilli = Extend through taste pore Afferent nerve = Transmits information to the brain Medulla oblongata = Recognizes specific taste</p> Signup and view all the answers

    What is one of the main purposes of the refractory period in nerve impulse transmission?

    <p>To limit the frequency of transmitted impulses</p> Signup and view all the answers

    The synaptic cleft separates the presynaptic and postsynaptic neurones.

    <p>True</p> Signup and view all the answers

    What role do calcium ions play in cholinergic synapses?

    <p>They facilitate neurotransmitter release from the presynaptic neurone.</p> Signup and view all the answers

    The ______ is the part of the presynaptic neurone that contains organelles necessary for neurotransmitter production.

    <p>synaptic knob</p> Signup and view all the answers

    Match the following components of a cholinergic synapse with their descriptions:

    <p>Presynaptic neurone = Releases neurotransmitters into the synapse Synaptic vesicles = Store neurotransmitters until release Postsynaptic neurone = Receives neurotransmitters and generates action potentials Neurotransmitter receptors = Bind with neurotransmitters on the postsynaptic membrane</p> Signup and view all the answers

    What type of information do nerves transmit?

    <p>Electrical impulses</p> Signup and view all the answers

    Hormones provide immediate responses to stimuli.

    <p>False</p> Signup and view all the answers

    What are the two main components of the nervous system?

    <p>Central nervous system (CNS) and Peripheral nervous system (PNS)</p> Signup and view all the answers

    The network of glands that produce hormones is known as the __________ system.

    <p>endocrine</p> Signup and view all the answers

    Match the following systems with their characteristics:

    <p>Nervous System = Transmits information as electrical impulses Endocrine System = Uses hormones as chemical messengers Neurones = Cells that transmit nerve impulses Glands = Cells that produce and release substances</p> Signup and view all the answers

    Which system uses chemical messengers to transmit information?

    <p>Endocrine system</p> Signup and view all the answers

    A nerve is a bundle of blood vessels that transmit information in the nervous system.

    <p>False</p> Signup and view all the answers

    What is the function of hormones in the body?

    <p>To alter the activity of specific target organs.</p> Signup and view all the answers

    What type of neurone carries impulses from receptors to the CNS?

    <p>Sensory neurone</p> Signup and view all the answers

    Motor neurones connect sensory neurones and effectors.

    <p>False</p> Signup and view all the answers

    What is the primary function of intermediate neurones?

    <p>To connect sensory and motor neurones.</p> Signup and view all the answers

    Motor neurones have a large cell body located in the ______.

    <p>spinal cord or brain</p> Signup and view all the answers

    Match the types of neurones with their primary function:

    <p>Sensory neurone = Carries impulses to the CNS Motor neurone = Carries impulses from the CNS Intermediate neurone = Connects sensory and motor neurones Relay neurone = Found entirely in the CNS</p> Signup and view all the answers

    What is the purpose of myelin in neurones?

    <p>To insulate the axon for faster impulse transmission</p> Signup and view all the answers

    Dendrites allow neurones to receive multiple impulses from other neurones.

    <p>True</p> Signup and view all the answers

    What are the small uninsulated sections along the axon called?

    <p>Nodes of Ranvier</p> Signup and view all the answers

    What is the primary role of myelin in nerve impulse transmission?

    <p>Insulates the axon to increase speed of conduction</p> Signup and view all the answers

    The action potentials can occur at any point along a myelinated neurone.

    <p>False</p> Signup and view all the answers

    What is the term used for the jumping of action potentials between nodes of Ranvier?

    <p>saltatory conduction</p> Signup and view all the answers

    During the refractory period, the neurone's membrane cannot generate another action potential because the __________ channels remain closed.

    <p>sodium ion (Na+)</p> Signup and view all the answers

    What determines the speed of conduction of an impulse in a neurone?

    <p>The presence of myelin and diameter of the axon</p> Signup and view all the answers

    The refractory period allows for continuous firing of action potentials in a neurone.

    <p>False</p> Signup and view all the answers

    In which sections of the axon does depolarization occur in a myelinated neurone?

    <p>nodes of Ranvier</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Myelin = Insulates the axon to increase conduction speed Refractory period = Recovery phase during which no action potential can be generated Nodes of Ranvier = Uninsulated sections where action potentials occur Saltatory conduction = Jumping of action potentials between nodes</p> Signup and view all the answers

    What happens when the threshold potential is reached?

    <p>An action potential is always triggered</p> Signup and view all the answers

    An increase in stimulus strength also increases the size of the action potential.

    <p>False</p> Signup and view all the answers

    What is the process called when sodium ions enter the axon?

    <p>depolarisation</p> Signup and view all the answers

    The potential difference across the membrane reaches about ___ mV to initiate an action potential.

    <p>-50</p> Signup and view all the answers

    Match the following phases of action potentials with their descriptions:

    <p>Depolarisation = Sodium ions diffuse into the axon Repolarisation = Potassium ions diffuse out of the axon Refractory Period = The axon section is unresponsive Threshold Potential = Potential difference reaches around -50mV</p> Signup and view all the answers

    Which ion mainly causes the repolarisation of the axon membrane?

    <p>Potassium ions</p> Signup and view all the answers

    The refractory period is when the axon is responsive and can generate more action potentials.

    <p>False</p> Signup and view all the answers

    What is triggered after an initial depolarisation occurs?

    <p>positive feedback</p> Signup and view all the answers

    After sodium ion channels close, potassium ions flow ____ the axon.

    <p>out of</p> Signup and view all the answers

    What initiates the flow of current to the next section of the axon membrane?

    <p>Sodium ion diffusion</p> Signup and view all the answers

    Study Notes

    Control and Coordination

    • Different parts of the body perform different functions, but the body works as one
    • This is due to coordination systems within the body
    • Two types of coordination systems exist: the nervous system and the endocrine system
    • The nervous system uses electrical impulses (nerve impulses) to coordinate activities rapidly
    • The endocrine system uses chemical messengers (hormones), carried in the bloodstream, to control slower activities

    Comparing the Nervous and Endocrine systems

    • | Feature | Nervous system | Endocrine system |
    • |---|---|---|
    • | Parts of the system | Brains, spinal cord, nerves/neurones | Glands |
    • | Type of message | Electrical impulse | Chemical (hormone) |
    • | Method of transmission | Neurones | Bloodstream |
    • | Effectors | Muscles, glands | Target cells in specific tissues |
    • | Speed of transmission | Very fast | Slower |
    • | Duration of effect | Short (until electrical impulses stop) | Longer (until the hormone is broken down) |

    The Nervous System

    • The nervous system consists of:
      • Central nervous system (CNS):
        • Brain
        • Spinal cord
      • Peripheral nervous system (PNS):
        • Cranial nerves
        • Spinal nerves
        • Peripheral nerves
      • Neurones (nerve cells):
        • Sensory neurones (carry impulses from receptors to CNS)
        • Motor neurones (carry impulses from CNS to effectors)
        • Intermediate neurones (relay neurones, connect sensory and motor neurones)
    • A bundle of neurones is known as a nerve
    • Neurons coordinate the activities of sensory receptors, decision-making centres in the CNS, and effectors like muscles and glands

    Neurones

    • There are three main types of neurone: sensory, relay, and motor

    • Sensory neurones carry impulses from receptors to the CNS

    • Intermediate (relay) neurones are entirely within the CNS and connect sensory and motor neurones

    • Motor neurones carry impulses from the CNS to effectors (muscles or glands)

    • Each neurone has a different structure

    • Motor neurones

      • Have a large cell body at one end within the spinal cord or brain
      • Have a nucleus in the cell body
      • Have many highly-branched dendrites

    • Sensory neurones

      • Have a cell body that branches off in the middle
      • Have branches near the stimulus or in a spinal ganglion

    • A neurone has a long fibre known as an axon:

      • It is insulated by myelin, a fatty sheath
      • Myelin is made by Schwann cells wrapping around the axon, with small uninsulated sections (nodes of Ranvier)

    • Electrical impulses jump from node to node (saltatory conduction) – this speeds up transmission

    Sensory Receptor Cells

    • Receptor cells are transducers, converting one form of energy (light, heat, or sound) into an electrical impulse within a sensory neurone

    • They are often found in sense organs such as the eye, taste buds, etc., and influence the sensory neurone.

    • When stimulated, receptor cells become depolarised.

    • Only strong stimuli will elicit a sufficient depolarisation to send an impulse.

    • The strength of a stimulus affects how quickly impulses are fired, not the size of the impulse.

    • Types of sensory receptors include Mechanoreceptors, Chemoreceptors, and Photoreceptors

    Chemoreceptors

    • Chemoreceptors detect chemicals in the internal and external environments.
    • Taste is a form of chemoreception.
    • Taste buds contain chemoreceptor cells that detect different tastes (sweet, sour, salty, bitter, umami).
    • Dissolved chemicals interact with receptors
    • This changes the shape of chemoreceptors causing sodium channels in receptor cells to open.
    • This results in an action potential transmitted to the brain.

    The Reflex Arc

    • The reflex arc coordinates fast responses to stimuli, involving sensory, intermediate, and motor neurons
    • This pathway allows quick responses to potentially harmful stimuli

    Resting Potential

    • The resting potential of a neuron describes the voltage difference across the cell membrane of a neuron that is not transmitting an impulse.
    • This potential is usually around -70 mV
    • Several factors contribute to maintaining the resting potential including sodium-potassium pumps, ion diffusion, and the permeability of the membrane to different ions, as well as other factors

    Action Potential

    • Action potentials describe a rapid change in voltage across a neuron membrane, resulting in a propagating wave of depolarization along the axon.
    • Key steps include depolarization (increase in sodium), repolarization (decrease in sodium and increase in potassium), and hyperpolarization.

    Repolarisation

    • Repolarisation involves voltage-gated potassium channels opening, causing potassium ions to leave the axon rapidly, restoring the resting potential
    • Repolarization is followed by hyperpolarization, making the membrane briefly more negative than its resting potential.

    Refractory Period

    • The refractory period is the period after an action potential when a new action potential cannot be easily initiated
    • It is essential for ensuring that action potentials travel in only one direction along a neuron
    • It limits the frequency at which action potentials can be produced

    Synapse

    • A synapse is the junction between two neurons
    • Synaptic transmission
      • electrical impulses cannot 'jump' across synapses
      • chemical messengers called neurotransmitters are released from vesicles at the presynaptic membrane
      • neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane
      • this stimulates the postsynaptic neurone

    Cholinergic Synapse

    • A specific type of synapse that uses acetylcholine (ACh) as its neurotransmitter
    • Steps in cholinergic synapse function:
      1. Action potential arrives at synaptic knob.
      2. Calcium ions enter, triggering vesicle fusion and ACh release.
      3. ACh diffuses across the synaptic cleft and binds to receptors.
      4. Sodium channels open, causing depolarisation of the postsynaptic membrane.
      5. Acetylcholinesterase breaks down ACh, terminating the signal.

    Muscle Contraction

    • Striated muscle is composed of muscle fibres
    • Sarcomeres are the contractile units within myofibrils
    • The sliding filament model describes how thin (actin) and thick (myosin) filaments interact to shorten the sarcomere.
    • Proteins like troponin, tropomyosin play crucial roles in regulating myosin-actin interactions.
    • Calcium ions trigger muscle contraction by causing a shape change in troponin which moves tropomyosin, exposing myosin binding sites on actin
    • ATP hydrolysis provides energy for the myosin heads to repeat the cycle.

    Control and Coordination in Plants

    • Plant hormones, often called plant growth regulators, influence many aspects of plant growth, including elongation growth
    • Auxin is a plant hormone essential for growth, often produced at the tips of roots and shoots
    • Auxin stimulates proton pumps, lowering the pH and activating expansins to loosen cell walls
    • This increases cell expansion by osmosis.

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    Description

    Explore the fascinating functions of chemoreceptors and taste buds in humans. This quiz covers basic tastes, the role of synapses, and the components of the nervous system, providing a comprehensive overview of sensory and neural processes.

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