Physiology of Excitable Tissues
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Questions and Answers

What is the term for a stimulus that produces the maximal response, where all motor units are recruited?

  • Submaximal stimulus
  • Threshold stimulus
  • Maximal stimulus (correct)
  • Supramaximal stimulus

    • What is the name of the complex responsible for generating respiratory rhythm?

  • Medulla oblongata complex
  • Respiratory pacemaker
  • Interneuron complex
  • Pre-Bötzinger complex (correct)

    • What is the typical resting membrane potential of skeletal muscle cells?

  • -70 mV
  • -60 mV
  • -90 mV (correct)
  • -50 mV

    • What is the term for the potential ability of excitable tissue to generate excitation and cause responses without external stimulus?

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

    What is the term for the transitional stage from physiological resting state to functional activity state?

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

    Which ions are primarily responsible for the generation of resting membrane potential?

    <p>Na+, K+, A-</p> Signup and view all the answers

    What is the term for a stimulus that exceeds the maximal value but does not increase the response beyond the maximal response?

    <p>Supramaximal stimulus</p> Signup and view all the answers

    What is the name of the state where the cell does not perform external work and has minimal metabolic intensity?

    <p>Physiological resting state</p> Signup and view all the answers

    What is the typical resting membrane potential of nerve cells?

    <p>-70 mV</p> Signup and view all the answers

    What is the term for the potential difference between the inside and outside of a cell under resting conditions?

    <p>Resting membrane potential</p> Signup and view all the answers

    What is the primary function of excitable tissues?

    <p>To generate and transmit electrochemical impulses</p> Signup and view all the answers

    What is the term for the ability of a tissue to respond to stimulation?

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

    What type of stimulus would a pinching sensation be classified as?

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

    What is the term for the transition of an excitable tissue from a resting state to a specific activity?

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

    What classification of stimuli is based on the origin of the stimulus?

    <p>Natural and artificial</p> Signup and view all the answers

    What is the term for a stimulus that is below the threshold and does not evoke a response?

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

    What type of stimuli is an electric shock an example of?

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

    What is the term for the specific response of an excitable tissue to a stimulus?

    <p>Action potential</p> Signup and view all the answers

    What classification of stimuli is based on the correspondence of the receptor and the stimulus?

    <p>Adequate and inadequate</p> Signup and view all the answers

    What is the term for the strength of a stimulus?

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

    What is the primary cause of the transition from PRS to FAS?

    <p>A stimulus or environmental change</p> Signup and view all the answers

    What is the minimum contraction of a whole muscle?

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

    What is the role of calcium ions in the contraction phase of a twitch?

    <p>Release of calcium ions from the sarcoplasmic reticulum</p> Signup and view all the answers

    What is the time period during which an organ or cell is incapable of repeating a particular action?

    <p>Refractory period</p> Signup and view all the answers

    What is the stage of activity when the cell performs its specific function or external work?

    <p>Functional activity state (FAS)</p> Signup and view all the answers

    What is the purpose of the restoration stage?

    <p>To restore the resting membrane potential (RMP)</p> Signup and view all the answers

    What is the result of a rapid rise in membrane potential opening of Na+ channels in the cellular membrane?

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

    What is the stage of activity characterized by a slow transition from FAS back to PRS?

    <p>Restoration stage</p> Signup and view all the answers

    What is the result of the release of acetylcholine from the motor end-plate?

    <p>Depolarization of the cell membrane</p> Signup and view all the answers

    What is the stage of the action potential characterized by a rapid decrease in membrane potential?

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

    What is the primary effect of the influx of Na+ ions on the biological membrane?

    <p>Depolarization of the cell membrane</p> Signup and view all the answers

    During which stage of the action potential does the permeability of the cell membrane to K ions increase?

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

    What is the primary function of the Na+/K+ pumps during the action potential?

    <p>To return the ion concentration to its original state</p> Signup and view all the answers

    What is the effect of the efflux of potassium ions on the membrane potential?

    <p>It becomes more negative</p> Signup and view all the answers

    During which stage of the action potential does the Na+ influx decrease significantly?

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

    What is the characteristic of the membrane potential during hyperpolarization?

    <p>It becomes more negative</p> Signup and view all the answers

    What is the primary cause of the decrease in membrane potential during hyperpolarization?

    <p>Efflux of potassium ions</p> Signup and view all the answers

    What is the characteristic of the membrane potential during the resting state?

    <p>It is the same as the resting potential</p> Signup and view all the answers

    What is the effect of the Na+ channels deactivating during the action potential?

    <p>Repolarization of the cell membrane</p> Signup and view all the answers

    What is the primary function of the K+ gates during the action potential?

    <p>To control the efflux of potassium ions</p> Signup and view all the answers

    What is the approximate percentage of body mass that skeletal muscles comprise?

    <p>36%</p> Signup and view all the answers

    What type of muscle fiber is responsible for moving visceral organs?

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

    What is a characteristic of single-unit smooth muscle?

    <p>Displays rhythmicity</p> Signup and view all the answers

    How do gap junctions contribute to the function of single-unit smooth muscle?

    <p>They allow for rapid spread of electrical signals</p> Signup and view all the answers

    What is the primary difference between smooth muscle cells and striated muscle cells?

    <p>Size of the cells</p> Signup and view all the answers

    What type of muscle fiber is responsible for pumping blood?

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

    What is the characteristic of smooth muscle cells that allows them to produce more cells during a lifetime?

    <p>Their ability to proliferate</p> Signup and view all the answers

    What is the term for the type of smooth muscle that is found in the walls of hollow and tubular organs?

    <p>Visceral smooth muscle</p> Signup and view all the answers

    What is the characteristic of smooth muscle that allows it to respond to humoral irritants?

    <p>Its ability to respond to hormonal changes</p> Signup and view all the answers

    What is the function of gap junctions in smooth muscle tissue?

    <p>To allow for the transmission of electrical signals</p> Signup and view all the answers

    What is the function of the transverse tubules in muscle fibers?

    <p>To carry action potentials deep into the muscle fiber</p> Signup and view all the answers

    What is the role of tropomyosin and troponin in muscle contraction?

    <p>To regulate the binding of myosin to actin</p> Signup and view all the answers

    What is the name of the protein that connects myosin filaments to the Z discs in muscle fibers?

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

    What is the name of the line that separates one sarcomere from another in a muscle fiber?

    <p>Z line</p> Signup and view all the answers

    What is the function of the myosin head in muscle contraction?

    <p>To bind to actin filaments during muscle contraction</p> Signup and view all the answers

    What is the name of the theory that explains how muscles contract to produce force?

    <p>The Sliding Filament Theory</p> Signup and view all the answers

    What is the role of calcium ions in muscle contraction?

    <p>To regulate the binding of myosin to actin</p> Signup and view all the answers

    What is the name of the compartment of myofibrils that is the smallest contractile unit of a muscle fiber?

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

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

    <p>To store calcium ions for muscle contraction</p> Signup and view all the answers

    What is the name of the protein that determines the length of thin filaments in muscle fibers?

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

    What is the primary characteristic of multi-unit smooth muscle?

    <p>Fibers are richly supplied with nerve endings and have motor units</p> Signup and view all the answers

    Which type of muscle is characterized by automaticity and contraction without external stimulation?

    <p>Heart muscle</p> Signup and view all the answers

    What is the function of the sarcoplasmic reticulum in skeletal muscle cells?

    <p>Reabsorbs calcium ions during relaxation</p> Signup and view all the answers

    What is the main difference between smooth muscle and skeletal muscle in terms of contraction?

    <p>Smooth muscle contractions are slower and longer</p> Signup and view all the answers

    What is the characteristic of skeletal muscle fibers?

    <p>Long, cylindrical, and striated</p> Signup and view all the answers

    What is the main function of skeletal muscle?

    <p>Support and maintenance of body posture</p> Signup and view all the answers

    What is the characteristic of smooth muscle in terms of gap junctions?

    <p>Has few or no gap junctions, requiring individual electrical impulses</p> Signup and view all the answers

    What is the primary function of the myofibrils in skeletal muscle cells?

    <p>To contract and relax during muscle function</p> Signup and view all the answers

    What is the characteristic of skeletal muscle cells?

    <p>Long, cylindrical, and multi-nucleated</p> Signup and view all the answers

    What is the main difference between skeletal muscle and heart muscle in terms of control?

    <p>Skeletal muscle is voluntary, while heart muscle is involuntary</p> Signup and view all the answers

    What is necessary for a skeletal muscle contraction to occur?

    <p>There must be a neural stimulus, enough Ca ions, and ATP</p> Signup and view all the answers

    What happens when there is no more ATP in the muscle cell?

    <p>The muscle becomes fatigued and stops contracting</p> Signup and view all the answers

    What is the role of Ca ions in muscle contraction?

    <p>Ca ions bind to troponin, exposing actin sites for myosin</p> Signup and view all the answers

    What happens when there are no more impulses sent from the CNS?

    <p>The muscle becomes relaxed and stops contracting</p> Signup and view all the answers

    What is the term for the condition when muscles tense up after death?

    <p>Rigor mortis</p> Signup and view all the answers

    What is necessary for the release of neurotransmitter from the axon terminal?

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

    What happens when the release of acetylcholine stops in the neuro-muscular synapse?

    <p>The muscle becomes relaxed and stops contracting</p> Signup and view all the answers

    What is the term for the transition from a state of muscle contraction to a state of muscle relaxation?

    <p>Mechanism of skeletal muscle relaxation</p> Signup and view all the answers

    What is the primary source of energy for muscle contraction?

    <p>Adenosine triphosphate (ATP)</p> Signup and view all the answers

    What is the role of creatine phosphate in muscle contraction?

    <p>Regenerating ATP from ADP</p> Signup and view all the answers

    What is the primary function of the nervous system in muscle contraction?

    <p>Sending signals to muscles to contract</p> Signup and view all the answers

    What is the result of muscle metabolism during strenuous exercise?

    <p>Accumulation of lactic acid leading to fatigue and soreness</p> Signup and view all the answers

    What is the primary difference between the central nervous system (CNS) and the peripheral nervous system (PNS)?

    <p>CNS is the brain and spinal cord, while PNS is the nerves</p> Signup and view all the answers

    What is the primary source of energy for the anaerobic glycolysis pathway?

    <p>Glycogen stored in muscles</p> Signup and view all the answers

    What is the primary function of oxidative phosphorylation in muscle metabolism?

    <p>Generating ATP through the breakdown of glucose</p> Signup and view all the answers

    What is the primary effect of the influx of sodium ions on the muscle cell membrane?

    <p>Increase in membrane potential</p> Signup and view all the answers

    What is the primary function of satellite cells in ganglia?

    <p>Regulate nutrient and neurotransmitter levels</p> Signup and view all the answers

    What is the primary function of neuroglia cells?

    <p>To regenerate and promote plasticity in the nervous system</p> Signup and view all the answers

    What is the characteristic of unipolar neurons?

    <p>They have one process that includes both an axon and a dendrite</p> Signup and view all the answers

    What is the function of dendrites in neurons?

    <p>To receive information from the periphery and transmit it to the cell body</p> Signup and view all the answers

    What is the type of transport responsible for moving substances from the cell body to the synapse?

    <p>Anterograde transport</p> Signup and view all the answers

    What is the function of axonal transport in neurons?

    <p>To move substances to and from the cell body through the axon</p> Signup and view all the answers

    What is the classification of nerve fibers based on structure?

    <p>Myelinated and unmyelinated nerve fibers</p> Signup and view all the answers

    What is the function of interneurons in the nervous system?

    <p>To integrate information between sensory and motor neurons</p> Signup and view all the answers

    What is the primary function of the autonomic nervous system?

    <p>Metabolism in organs and function of tissues</p> Signup and view all the answers

    What is the main functional unit of the nervous system?

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

    What is the function of myelin sheaths in the nervous system?

    <p>Electrical insulation, speeding information conduction</p> Signup and view all the answers

    What is the role of ependymal cells in the CNS?

    <p>Production of cerebrospinal fluid</p> Signup and view all the answers

    What is the function of the dendrites of a neuron?

    <p>Receiving input from other neurons or stimuli</p> Signup and view all the answers

    What is the term for the site of communication between a neuron and its target cell?

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

    What is the function of oligodendrocytes in the CNS?

    <p>Myelination of axons</p> Signup and view all the answers

    What is the function of astrocytes in the CNS?

    <p>Maintenance of the blood-brain barrier and recycling of ions and neurotransmitters</p> Signup and view all the answers

    What is the primary function of myelin in nerve fibers?

    <p>To facilitate the transmission of electrical signals along the axon</p> Signup and view all the answers

    What is the term for nerve fibers with a diameter of 12-20 μm and a conduction velocity of 70-120 m/s?

    <p>Aα fibers</p> Signup and view all the answers

    What is the term for the loss of the myelin sheath with a relatively undamaged axon due to different pathological processes?

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

    What is the primary function of oligodendrocytes in the CNS?

    <p>To form the myelin sheath around axons</p> Signup and view all the answers

    What is the term for the nerve fibers that release acetylcholine at their synapse when an impulse is transmitted?

    <p>Cholinergic nerve fibers</p> Signup and view all the answers

    What is the term for the point where the cell body and axon meet?

    <p>Axon hillock</p> Signup and view all the answers

    What is the characteristic of Group C nerve fibers?

    <p>They are unmyelinated and have a high threshold</p> Signup and view all the answers

    What is the primary function of myelination in nerve fibers?

    <p>To insulate the nerve fiber and increase the rate of transmission</p> Signup and view all the answers

    What is the primary function of metabotropic receptors in the postsynaptic neuron?

    <p>To indirectly activate nearby ion channels through a secondary messenger</p> Signup and view all the answers

    What is the effect of the influx of Cl- ions on the postsynaptic membrane potential?

    <p>Hyperpolarization of the membrane</p> Signup and view all the answers

    What is the characteristic of ionotropic receptors that allows for rapid signaling?

    <p>Direct allowance of ions to pass through the membrane</p> Signup and view all the answers

    What is the primary difference between excitatory and inhibitory postsynaptic potentials?

    <p>The direction of ion flow</p> Signup and view all the answers

    What is the term for the type of receptor that is involved in the indirect activation of nearby ion channels?

    <p>Metabotropic receptor</p> Signup and view all the answers

    What is the primary purpose of the reuptake of neurotransmitters by the pre-synaptic cell?

    <p>To recycle the neurotransmitters for future use</p> Signup and view all the answers

    What is the primary function of glycine in the body?

    <p>To control hearing processing and pain transmission</p> Signup and view all the answers

    What is the main difference between autonomic and somatic reflex arcs?

    <p>The presence of an autonomic ganglion</p> Signup and view all the answers

    Which type of inhibition occurs when the inhibitory synaptic knob is located directly on the termination of the presynaptic excitatory fiber?

    <p>Presynaptic inhibition</p> Signup and view all the answers

    What determines the strength of a stimulus?

    <p>The amplitude of the action potential</p> Signup and view all the answers

    What is the primary function of the interneuron in the central nervous system?

    <p>To process and integrate the sensory information</p> Signup and view all the answers

    What is the result of the release of an inhibitory neurotransmitter from the presynaptic terminal in postsynaptic inhibition?

    <p>Hyperpolarization of the postsynaptic neuron</p> Signup and view all the answers

    What is the characteristic of autonomic reflexes that distinguishes them from somatic reflexes?

    <p>They have a longer reflex time</p> Signup and view all the answers

    What is the term for the type of inhibition that occurs without the participation of inhibitory structures?

    <p>Post-excitation inhibition</p> Signup and view all the answers

    What is the primary function of inhibitory neurotransmitters in the central nervous system?

    <p>To coordinate the action of flexors and extensors</p> Signup and view all the answers

    What is the effect of the release of an inhibitory neurotransmitter, such as GABA, on the postsynaptic neuron?

    <p>Hyperpolarization of the neuronal membrane</p> Signup and view all the answers

    What is the purpose of spatial summation in neurons?

    <p>To increase the likelihood of an action potential</p> Signup and view all the answers

    What is the role of glutamate in neurotransmission?

    <p>It is an excitatory neurotransmitter that increases the likelihood of an action potential</p> Signup and view all the answers

    What is the effect of temporal summation in neurons?

    <p>It increases the likelihood of an action potential</p> Signup and view all the answers

    What is the primary function of inhibitory neurotransmitters, such as GABA?

    <p>To inhibit the neuron and decrease the likelihood of an action potential</p> Signup and view all the answers

    What is the primary effect of the parasympathetic nervous system on blood vessels?

    <p>Dilation of blood vessels except coronary</p> Signup and view all the answers

    Which type of receptor is found in autonomic ganglia of the sympathetic nervous system?

    <p>N-cholinoreceptors</p> Signup and view all the answers

    What is the primary function of the sympathoadrenal system?

    <p>Physiological response to outside stimuli</p> Signup and view all the answers

    Where are the ganglia of the parasympathetic nervous system located?

    <p>Close to the organ to be innervated or within it</p> Signup and view all the answers

    What is the primary neurotransmitter released at the presynaptic pole of the parasympathetic nervous system?

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

    What type of receptors are responsible for detecting changes in concentration of solutes in body fluids and changes in osmotic activity?

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

    What is the primary function of cell-surface receptors?

    <p>To trigger signaling pathways in response to external ligands</p> Signup and view all the answers

    Which type of receptors are typically the targets of fast neurotransmitters such as acetylcholine (nicotinic) and GABA?

    <p>Ion channel-linked receptors</p> Signup and view all the answers

    What is the term for receptors that are sensitive to specific chemicals, including receptors for smell and taste, and receptors that detect O2 and CO2 concentrations in blood?

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

    What is the term for receptors that are embedded in the sensory neuron itself and react to an external influence?

    <p>Primary receptors</p> Signup and view all the answers

    What is the primary function of calmodulin in the context of synaptic transmission?

    <p>To bind calcium ions and cause vesicles to migrate towards the presynaptic membrane</p> Signup and view all the answers

    What is the term for the potential difference between the inside and outside of the postsynaptic membrane during synaptic transmission?

    <p>Excitatory postsynaptic potential (EPSP)</p> Signup and view all the answers

    What is the purpose of the enzyme that deactivates the neurotransmitter in the synaptic gap?

    <p>To prevent the accumulation of neurotransmitters in the synaptic gap</p> Signup and view all the answers

    What is the direction of transmission of excitation in synapses?

    <p>From the presynaptic membrane to the postsynaptic membrane</p> Signup and view all the answers

    What is the term for the time period from neurotransmitter release to receptor channel binding?

    <p>Less than a millionth of a second</p> Signup and view all the answers

    What is the approximate number of neurotransmitter molecules released in neuromuscular synapses?

    <p>30-50 thousand</p> Signup and view all the answers

    What is the effect of excitatory neurotransmitters on ion channels?

    <p>They open Na+ and Ca2+ channels and inhibit K+ and Cl- channels</p> Signup and view all the answers

    What is the characteristic of receptors that respond to neurotransmitters?

    <p>They are located only on the postsynaptic membrane</p> Signup and view all the answers

    What is the primary function of ion channels in synaptic transmission?

    <p>To generate a postsynaptic potential</p> Signup and view all the answers

    What is the term for the type of GABA receptors that are structurally different from GABAA receptors?

    <p>GABAC receptors</p> Signup and view all the answers

    Which part of the brain controls emotions, hearing, vision, and all precision of voluntary actions?

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

    What is the outer layer of grey matter of the cerebrum found only in mammals?

    <p>Cerebral cortex</p> Signup and view all the answers

    Which lobe of the cerebral hemisphere is responsible for controlling somatic sensory functions?

    <p>Parietal lobe</p> Signup and view all the answers

    What is the term for the organization of the cerebrum, where the right hemisphere controls the left side of the body and the left hemisphere controls the right side of the body?

    <p>Contralateral organization</p> Signup and view all the answers

    Which part of the brain is responsible for controlling all voluntary actions in the body?

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

    What is the term for the structure that connects the two cerebral hemispheres?

    <p>Corpus callosum</p> Signup and view all the answers

    Which part of the brain is responsible for controlling involuntary actions, such as breathing and heart rate?

    <p>Brain stem</p> Signup and view all the answers

    What is the term for the part of the brain that relays sensory information to the cerebral cortex?

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

    What is the primary function of the cerebral cortex?

    <p>Analysis of the external environment and cognitive abilities</p> Signup and view all the answers

    What is the characteristic of the basal ganglia that is thought to be involved in various cognitive, emotional, and movement-related functions?

    <p>Extensive connections with other brain regions</p> Signup and view all the answers

    What is the difference between the cerebral cortex of lower developed animals and higher developed ones?

    <p>Localization of functional zones</p> Signup and view all the answers

    What is the role of the basal ganglia in movement?

    <p>Facilitation of desired movements and inhibition of unwanted movements</p> Signup and view all the answers

    What is the structure that is divided into regions, such as visual, auditory, and speech areas?

    <p>Cerebral cortex</p> Signup and view all the answers

    What is the consequence of severe brain injury in higher developed animals?

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

    What is the structure that is associated with behavior, instincts, and cognitive abilities?

    <p>Cerebral cortex</p> Signup and view all the answers

    What is the characteristic of the motor zone and sensory zone in each hemisphere of the cerebral cortex?

    <p>They are functionally divided</p> Signup and view all the answers

    What is the primary function of the autonomic nervous system?

    <p>Innervates cardiac muscle, smooth muscle, and glands</p> Signup and view all the answers

    What is the difference between the sympathetic and parasympathetic nervous systems?

    <p>Sympathetic has shorter preganglionic fibers, parasympathetic has longer preganglionic fibers</p> Signup and view all the answers

    What is the neurotransmitter released by preganglionic fibers in the sympathetic nervous system?

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

    What is the function of postganglionic fibers in the sympathetic nervous system?

    <p>Release norepinephrine</p> Signup and view all the answers

    What is the primary difference between the somatic and autonomic nervous systems?

    <p>Somatic is voluntary, autonomic is involuntary</p> Signup and view all the answers

    What is the function of the parasympathetic nervous system?

    <p>Decrease heart rate and blood pressure</p> Signup and view all the answers

    What is the primary function of the peripheral nervous system?

    <p>Control voluntary actions</p> Signup and view all the answers

    What is the difference between preganglionic and postganglionic fibers?

    <p>Preganglionic fibers are shorter, postganglionic fibers are longer</p> Signup and view all the answers

    Which part of the hypothalamus is responsible for synthesizing neurohormones?

    <p>Nucleus supraopticus</p> Signup and view all the answers

    What is the primary function of the cerebellum?

    <p>Maintaining posture and balance</p> Signup and view all the answers

    What is the term for hormones produced and released by neuroendocrine cells?

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

    Where are vasopressin and oxytocin transported to?

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

    What is the function of the hypothalamo-hypophyseal tract?

    <p>Transporting hormones from the hypothalamus to the pituitary gland</p> Signup and view all the answers

    What is the primary function of the amygdala in the brain?

    <p>Processing emotional responses</p> Signup and view all the answers

    What is the term for the middle part of the hypothalamus?

    <p>Middle hypothalamus</p> Signup and view all the answers

    What is the result of damage to the hippocampus?

    <p>Impaired ability to learn new information</p> Signup and view all the answers

    What is the function of the epithalamus?

    <p>Connecting the limbic system to other parts of the brain</p> Signup and view all the answers

    What is the role of the reticular formation in the brain?

    <p>Maintaining alertness and orientation</p> Signup and view all the answers

    What is the characteristic of the hippocampus in terms of microstructural changes?

    <p>Dendrites quickly form new branches and new synapses are formed</p> Signup and view all the answers

    What is the term for the process by which neurosecretory cells secrete hormones into the blood?

    <p>Humoral transport</p> Signup and view all the answers

    What is the effect of stimulating the amygdala on the body's automatic fear response?

    <p>It increases the fear response</p> Signup and view all the answers

    What is the result of damage to the hypothalamus?

    <p>Affecting the production of certain hormones</p> Signup and view all the answers

    What is the characteristic of the limbic system in terms of damage?

    <p>It leads to uncontrolled emotions and aggression</p> Signup and view all the answers

    What is the role of the reticular formation in the development of conditioned reflexes?

    <p>It is essential for the development of conditioned reflexes</p> Signup and view all the answers

    Study Notes

    Physiology of Excitable Tissues

    • Excitable tissues are capable of generating and transmitting electrochemical impulses along the membrane, known as action potential.
    • Examples of excitable tissues include muscle tissue, nervous tissue, and glandular tissue.

    Classification of Stimuli

    • By type of energy: mechanical, thermal, electrical, and chemical
    • By origin: natural or artificial
    • By nature of stimuli: rhythmic, arrhythmic, and individual
    • By correspondence of receptor and stimulus: adequate and inadequate
    • By strength: subthreshold, threshold, submaximal, maximal, and supramaximal

    Strength of Stimuli

    • Subthreshold stimuli: do not evoke any response
    • Threshold stimulus: just sufficient to elicit response and produce minimal contraction
    • Submaximal stimuli: produce a graded response
    • Maximal stimulus: produces the maximal response
    • Supramaximal stimulus: exceeds the maximal value, but does not increase the response beyond the maximal response

    Automaticity

    • The potential ability of excitable tissue to generate excitation and cause responses without external stimulus
    • Some cells can switch from resting state to functional activity state spontaneously, without an external stimulus

    Natural States of Excitable Tissue

    • Physiological resting state (PRS): a passive stage with minimal metabolic intensity
    • Functional activity state (FAS): a stage of activity when the cell performs its specific function, with a significant increase in metabolism
    • Restoration stage: a transitional stage during which the cell returns to PRS

    Membrane Potential

    • The potential difference between the inside and outside of the cell under resting conditions
    • Resting membrane potential (RMP) values for different cells:
      • Nerve cells (neurons): ~ -70 mV
      • Skeletal muscle cells: ~ -90 mV
      • Smooth muscle cells: ~ -60 mV
    • RMP is generated by the unequal distribution of ions between the inside and outside of the cell

    Action Potential

    • A reversible change in polarization that occurs in the cell membrane
    • Three stages:
      1. Depolarization: rapid change in membrane potential, opening of Na+ channels
      2. Repolarization: permeability of the cell membrane to K ions increases, K ions flow out of the cell
      3. Hyperpolarization: change in potential that makes the membrane more polarized, caused by efflux of potassium ions and closing of potassium channels

    Refractory Period

    • A period of time during which an organ or cell is incapable of repeating a particular action
    • Absolute refractory period: corresponds to depolarization and repolarization
    • Relative refractory period: corresponds to hyperpolarization

    Muscles

    • Muscle cells are called muscle fibers, which are narrow and long, and comprise ~36% of the body mass.
    • There are three types of muscle fibers: smooth, skeletal, and cardiac.

    Smooth Muscle

    • Smooth muscle fibers are smaller than striated muscle fibers, with each cell containing one nucleus.
    • More cells can be produced during a lifetime.
    • There are two types of smooth muscle:
      • Visceral or single-unit smooth muscle: responds to stimulation as a single unit, with gap junctions allowing electrical signals to spread rapidly.
      • Multi-unit smooth muscle: muscle fibers are less well organized, require multiple nerve fibers to stimulate, and do not react to humoral irritants.

    Smooth Muscle vs. Skeletal Muscle

    • Smooth muscles are innervated by the autonomic nervous system, have automaticity, and contractions are slower and last longer.
    • Smooth muscles can remain in a state of contraction for a long time, and consume little energy compared to skeletal muscles.
    • Smooth muscles have plasticity, allowing them to stretch significantly.

    Cardiac Muscle (Myocardium)

    • Cardiac muscle works continuously, has automaticity, and muscle fibers are short, branched, and bound in a meshwork.
    • All myocardial cells have the same excitability, contracting simultaneously and equally strongly.
    • Cardiac muscle is not under voluntary control.

    Skeletal Muscle

    • Skeletal muscle is attached to the skeleton, skin, and fascia, and can be controlled by the animal's will.
    • Skeletal muscle fibers are arranged parallel, and groups of muscle fibers form bundles, muscles.
    • Skeletal muscle as an organ includes nerves and blood vessels.
    • Skeletal muscle functions include ensuring movements, controlling body posture, supporting, heat production, and defense.

    Skeletal Muscle Physiological Properties

    • Skeletal muscle has excitability, contractility, conductivity, stretchability, elasticity, and plasticity.

    Skeletal Muscle Structure

    • Skeletal muscle cells are long, cylindrical, and striated, with multiple nuclei.
    • Muscle fibers are dominated by myofibrils, which consist of myofilaments.
    • Myofibrils are organized in a repetitive pattern, with the smallest unit being the sarcomere.

    Microscopic Anatomy of a Skeletal Muscle Fiber

    • A skeletal muscle fiber consists of:
      • Sarcolemma (muscle fiber cell membrane)
      • Sarcoplasm (muscle fiber cytoplasm)
      • Sarcoplasmic reticulum (smooth endoplasmic reticulum)
      • Transverse tubules (formed by invaginations of the sarcolemma)
      • Myofibril (bundle of thread-like contractile elements)
      • Myofilaments (extremely fine thread-like proteins)

    Myofilaments

    • There are four types of myofilaments:
      • Thick filaments (myosin)
      • Thin filaments (actin)
      • Elastic filaments (titin)
      • Non-elastic filaments (nebulin)

    Functional Division of Structural Elements

    • Motor (contractile): actin, myosin
    • Regulators: tropomyosin, troponin
    • Structural: nebulin, titin, α-actinin, myomesin, transverse tubules

    Sarcomere

    • The sarcomere is the smallest contractile unit of a muscle fiber, a compartment of myofibrils.
    • A sarcomere consists of:
      • Z line
      • M line
      • H zone
      • I band
      • A band

    Sliding Filament Theory of Muscular Contraction

    • The actin and myosin filaments within the sarcomeres bind to create cross-bridges and slide past one another, creating a contraction.
    • The theory explains how cross-bridges are formed and the subsequent contraction of muscle.

    Skeletal Muscle Contraction

    • The process of skeletal muscle contraction involves:
      1. Release of neurotransmitter acetylcholine at the efferent somatic neuron-muscle synapse.
      2. Action potential occurring and spreading through the sarcolemma and T tubules.
      3. Release of Ca ions and spread into the sarcoplasm.
      4. Combination of calcium ions with troponin, exposing actin binding sites.
      5. Attachment of the activated myosin head to the actin binding site.
      6. Movement of the myosin head, producing a power stroke, resulting in the sliding of the filaments.
      7. Detachment of the myosin head from the actin site, and return to its original position.
      8. Repeated cycle of contraction as long as calcium and ATP are present.

    Muscle Contraction Mechanism

    • Voluntary muscle contraction is regulated by the motor center of the cerebral cortex
    • Involuntary contraction is regulated by the lower centers, e.g., in the spinal cord
    • Information with impulses from the CNS is carried by motor neurons, which are brought to the muscle fiber through synapses
    • An action potential occurs, and the muscle contracts, but only with enough Ca ions
    • Ca ions are needed for:
      • The release of neurotransmitter from the axon terminal
      • Binding to troponin, causing a position change in tropomyosin, exposing the actin sites that myosin will attach to for muscle contraction

    Requirements for Skeletal Muscle Contraction

    • Neural stimulus
    • Calcium in the muscle cells
    • ATP must be available for energy

    Mechanism of Skeletal Muscle Relaxation

    • No impulses are sent from the CNS to the motor center
    • The release of the neurotransmitter ACH stops in the neuro-muscular synapse
    • ACH-esterase neutralizes already released ACH at the synapse, stopping the generation of action potentials
    • Ca2+ releasing channels close, and efflux of ions to the extracellular environment occurs
    • The blocking effect of Ca ions to troponin and tropomyosin stops
    • Transverse bridges of acto-myosin complex collapse, and the previous structural order is restored

    RIGOR MORTIS

    • The condition where muscles tense up after death

    Stopping a Contraction

    • Energy system fatigue: No more ATP left in the muscle cell
    • Nervous system fatigue: The nervous system cannot create impulses sufficiently or quickly enough to maintain the stimulus and cause calcium release
    • Voluntary nervous system control: The nerve that tells the muscle to contract stops sending signals
    • Sensory nervous system information: Feedback from sensory neurons indicating muscle injury or other factors

    Muscle Metabolism (Energy)

    • Muscles perform hard work and need a lot of energy
    • Energy is required for both muscle contraction and relaxation
    • Chemical energy is released and converted into mechanical and thermal energy
    • ATP is the only energy source used directly for contractile activity
    • ATP is derived from creatine phosphate (CP), muscle glycogen, and lipids
    • ATP is resynthesized from these sources through various pathways:
      • Transfer of high-energy phosphate from CP to ADP
      • Anaerobic Glycolysis
      • Oxidative phosphorylation

    Energy Coverage of Muscle Contraction

    • The ATP-CP system: Energy is derived from ATP molecules present in muscles, and creatine phosphate is used to quickly regenerate ATP
    • Anaerobic Glycolysis: Energy is produced from glycogen, and 2 ATP and 2 pyruvic acid molecules are generated
    • Oxidative phosphorylation: Energy is produced from glucose, pyruvic acid, and free fatty acids, and 36 ATP molecules are generated

    Nervous Tissue

    Division of the Nervous System (NS)

    • The nervous system is divided into two subdivisions: the central nervous system (CNS) and the peripheral nervous system (PNS)
    • The CNS includes the brain and spinal cord
    • The PNS includes nerves that go to the CNS (afferent) and from the CNS to muscles and internal organs (efferent)

    Neuron

    • Neurons are the main functional structural units that form the grey matter of the brain and ganglia
    • Upon receiving stimuli, nerve cells switch from a physiological resting state to a functional activity state
    • Neurons are responsible for computation and communication in the nervous system
    • They are electrically active and release chemical signals to communicate between each other and with target cells

    Neuroglia Cells

    • Neuroglia cells provide nourishment and support to neurons
    • Types of neuroglia cells:
      • Astrocytes: maintain the blood-brain barrier and preserve the chemical environment
      • Oligodendrocytes: myelinate axons in the CNS
      • Ependymal cells: line ventricles and central canal and are involved in cerebrospinal fluid production
      • Microglia: remove cell debris, wastes, and pathogens
      • Schwann cells: myelinate axons in the PNS
      • Satellite cells: regulate nutrient and neurotransmitter levels around neurons in ganglia

    Neuron Classification by Shape

    • Unipolar neurons: have one process that includes both an axon and a dendrite
    • Bipolar neurons: have two processes, an axon and a dendrite, that extend from each end of the cell body
    • Multipolar neurons: have more than two processes, an axon, and two or more dendrites

    Axonal Transport

    • Axonal transport is a cellular process responsible for the movement of mitochondria, lipids, synaptic vesicles, proteins, and other organelles to and from a neuron's cell body
    • Movements along axons occur in two ways:
      • Anterograde transport: from the cell body to the synapse
      • Retrograde transport: from the axon termini to the cell body

    Classification of Nerve Fibers

    • By function:
      • Somatic: innervate skeletal muscles
      • Autonomic: innervate internal organs and blood vessels
      • Secretory: innervate glands and stimulate secretion
      • Sensory (afferent): transmit impulses to the CNS
      • Motor (efferent): carry impulses toward the body surface
      • Interneurons (association neurons): any neurons between a sensory and a motor neuron
    • By structure: myelinated and unmyelinated nerve fibers
    • By type of synapse and neurotransmitter: adrenergic, cholinergic, peptidergic, etc.
    • By diameter and conduction velocity

    Direct and Indirect Binding to Postsynaptic Receptors

    • There are two types of receptor channels:
      • Direct (ionotropic receptors): allow ions to pass through the membrane, neurotransmitter acts as a key to open the ion channel, and it's the fastest type of channel (0.5 ms)
      • Indirect (metabotropic or G protein coupled receptors): binding of neurotransmitter to receptor causes release of a secondary messenger, which indirectly activates nearby ion channels, and it's a slower process (30 ms to 1 second)

    Postsynaptic Potentials

    • Postsynaptic potentials can be either excitatory (depolarizing) or inhibitory (hyperpolarizing)
    • Excitatory Postsynaptic Potentials (EPSPs):
      • Excitatory ion channels are permeable to Na+ and K+
      • Binding of excitatory neurotransmitter to receptor on postsynaptic membrane causes partial depolarization of postsynaptic cell membrane, increasing the likelihood of an action potential (AP)
    • Inhibitory Postsynaptic Potentials (IPSPs):
      • Inhibitory ion channels are permeable to Cl- and K+
      • Binding of inhibitory neurotransmitter to receptor on postsynaptic membrane causes hyperpolarization of postsynaptic membrane, making it more difficult for the cell membrane potential to reach threshold, thereby reducing the likelihood of an action potential (AP)

    Excitatory and Inhibitory Synapses

    • Excitatory synapses: presynaptic neuron releases an excitatory transmitter (e.g., glutamate), which depolarizes the postsynaptic cell membrane, increasing the likelihood of an action potential (AP)
    • Inhibitory synapses: presynaptic neuron releases an inhibitory neurotransmitter (e.g., GABA), which hyperpolarizes the postsynaptic cell membrane, reducing the likelihood of an action potential (AP)

    Inhibition

    • Inhibition is a reversible change in the excitability of a nerve cell, decreasing its functional activity
    • Inhibition is important in regulating various opposing processes, such as coordinating the action of flexors and extensors
    • Disruptions in inhibitory processes can lead to disturbances in the nervous system, such as neurosis, depression, etc.

    Types of Inhibition

    • By localization: presynaptic (indirect) and postsynaptic (direct)
    • By the nature of the process: mainly hyperpolarization (and occasionally strong depolarization)

    Patterns of Neurotransmission

    • A, B, C, D, E, and F are neurons in a tract that projects from left to right
    • Neurons B, D, and E release excitatory neurotransmitters, while neurons A and F release inhibitory neurotransmitters
    • The net effect of neuronal interactions on neurotransmission from B to C is shown in a table

    Inactivation of Neurotransmitters

    • Enzymatic deactivation: acetylcholine is broken down into acetate and choline in the synaptic gap
    • Reuptake: some neurotransmitters are removed by specific transporter proteins on the presynaptic membrane
    • Simple diffusion: neurotransmitters such as dopamine are able to diffuse away from their targeted synaptic junctions and are eliminated from the body

    Classification of Reflexes

    • Inborn reflexes or unconditioned reflexes
    • Learned (acquired) reflexes or conditioned reflexes

    Reflex Arc

    • The reflex arc contains five basic components:
      1. Sensory receptor
      2. Sensory (afferent) neuron
      3. Interneuron in the central nervous system
      4. Motor (efferent) neuron
      5. Effector (target organ)

    Autonomic Nervous System

    • Is not subject to the will of the animal
    • Innervates mainly internal organs and blood vessels
    • Autonomic nerve centers are scattered in different parts of the CNS
    • Autonomic reflexes have a relatively long reflex time
    • Autonomic reactions are diffuse, involving many organs

    Neurotransmitters/Receptors

    • Acetylcholine is the neurotransmitter of the parasympathetic nervous system
    • Norepinephrine is the neurotransmitter of the sympathetic nervous system
    • There are several types of receptors in the postsynaptic membrane:
      • M-cholinoreceptors (Muscarinic acetylcholine receptors)
      • N-cholinoreceptors (Nicotinic acetylcholine receptors)
      • Adrenoreceptors (α and β)

    Receptors

    • A cellular receptor is a molecule that responds to external and/or internal environment changes

    • Receptors detect stimulus from different modalities (energy forms) and convert them into electrical signals

    • Classification of receptors based on what type of irritation they perceive:

      • Photoreceptors
      • Mechanoreceptors
      • Thermoreceptors
      • Osmoreceptors
      • Chemoreceptors
      • Nociceptors### Ion Channel-Linked Receptors

    • Ion channel-linked receptors bind a ligand and open a channel through the membrane, allowing specific ions to pass through in milliseconds.

    • Signaling molecules act as keys to open ion channels.

    • These receptors are typically the targets of fast neurotransmitters such as acetylcholine (nicotinic) and GABA.

    GABA Receptors

    • GABA receptors respond to the neurotransmitter gamma-aminobutyric acid (GABA), the chief inhibitory compound in the CNS.
    • There are three classes of GABA receptors:
      • Ionotropic (ligand-gated) GABAA receptors
      • Metabotropic (G protein-coupled) GABAB receptors
      • Ionotropic (ligand-gated) GABAC receptors (structurally different from GABAA)

    Neurotransmitter Transmission

    • Neurotransmitter release from presynaptic cells is triggered by Ca ions entering the cell through action potentials.
    • Neurotransmitters pass through the synaptic gap and connect with their receptors on the postsynaptic plasmalemma.
    • Ion channels open by direct or indirect binding, resulting in a postsynaptic potential.
    • Approximately 30,000-50,000 neurotransmitter molecules are released in neuromuscular synapses, and 200,000-500,000 in nerve-nerve synapses.
    • Enzymes that deactivate neurotransmitters, such as cholinesterase, are present in the synaptic gap.

    Excitatory Neurotransmitters

    • Excitatory neurotransmitters cause a depolarization called the excitatory postsynaptic potential (EPSP).
    • EPSP opens Na and Ca ion channels, but inhibits the activity of K and Cl ions.
    • Each neurotransmitter has its own specific receptor.

    Synaptic Transmission

    • Excitation in synapses is transferred only in one way, from the presynaptic membrane to the postsynaptic membrane.
    • Receptors that respond to neurotransmitters are located only on the postsynaptic membrane.
    • The time it takes for the impulse to propagate across the synapses is called the synaptic delay.

    Peripheral Nervous System (PNS)

    • The PNS is the communication link between the Central Nervous System (CNS) and muscles and glands. • The PNS has two divisions: the Autonomic Nervous System (ANS) and the Somatic Nervous System. • The ANS is the involuntary branch of the PNS, innervating cardiac muscle, smooth muscle, most exocrine glands, some endocrine glands, and adipose tissue. • The Somatic Nervous System is subject to voluntary control, innervating skeletal muscle.

    Autonomic Nervous System (ANS)

    • The ANS has two subdivisions: the Sympathetic Nervous System and the Parasympathetic Nervous System. • The Sympathetic Nervous System originates from the thoracic and lumbar regions of the spinal cord. • The Parasympathetic Nervous System originates from the cranial and sacral areas of the CNS. • Sympathetic preganglionic fibers are shorter, while parasympathetic preganglionic fibers are longer. • Sympathetic postganglionic fibers release norepinephrine, which binds to α1, α2, β1, β2 adrenoreceptors. • Parasympathetic postganglionic fibers release acetylcholine, which binds to M-cholinoreceptors.

    Brain Anatomy

    Cerebrum

    • The cerebrum consists of two cerebral hemispheres, the right and the left. • The cerebrum is the largest part of the brain, containing the cerebral cortex, hippocampus, and basal ganglia. • The cerebrum controls emotions, hearing, vision, and voluntary actions with the assistance of the cerebellum.

    Cerebral Hemispheres

    • Each hemisphere is divided into four lobes: frontal, parietal, occipital, and temporal. • The right hemisphere controls and processes signals from the left side of the body, while the left hemisphere controls and processes signals from the right side of the body.

    Cerebral Cortex

    • The cerebral cortex is a thin layer of gray matter covering the surface of the cerebral hemispheres. • It is the highest part of the CNS, the most complex in structure and function, and associated with behavior, analysis of the external environment, instincts, and cognitive abilities. • Each hemisphere has a motor zone and a sensory zone, functionally divided into regions such as visual area, auditory area, and speech area.

    Basal Ganglia

    • The basal ganglia are a group of structures found deep within the cerebral hemispheres, including the caudate, putamen, and globus pallidus. • The basal ganglia are involved in movement, cognitive, emotional, and movement-related functions, and facilitation of desired movements and inhibition of unwanted movements.

    Hypothalamus

    • The hypothalamus is involved in the synthesis of neurohormones and their secretion to the hypophysis (pituitary gland). • The hypothalamus produces vasopressin and oxytocin, which are transported via the hypothalamo-hypophyseal tract to the neurohypophysis. • The hypothalamus also produces hypothalamic hypophysiotropic hormones, which are transported via the blood capillaries to the adenohypophysis.

    Epithalamus

    • The epithalamus produces melatonin, signaling nighttime sleep. • It connects the limbic system to other parts of the brain.

    Cerebellum

    • The cerebellum is divided into two distinct parts: the oldest part involved in balance adjustment, and the newest part involved in coordination of muscle activity. • The cerebellum maintains posture and balance, and is involved in orientation and alertness reflex, and in the development of conditioned reflexes.

    Amygdala

    • The amygdala is an almond-shaped structure located next to the hippocampus. • It is involved in emotional responses, including feelings of happiness, fear, anger, and anxiety, and formation of new memories. • The amygdala is linked with the fight-or-flight response and can influence the body's automatic fear response.

    Damage to the Limbic System

    • Amygdala damage can result in more aggression, irritability, loss of control of emotions, and deficits in recognizing emotions. • Hippocampus damage can lead to deficits in learning and memory. • Hypothalamus damage can affect the production of certain hormones, leading to mood and emotion disorders. • Uncontrolled emotions can result in more aggression, anxiety, and agitation, as well as olfactory impairments, memory impairments, and abnormal biological rhythms.

    Reticular Formation (RAS)

    • The reticular formation is a set of interconnected nuclei located throughout the brainstem. • It is a network of neurons that play a crucial role in regulating sleep, arousal, and attention.

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    Physiology of Excitable Tissues (PDF)

    Description

    Learn about excitable tissues, their reaction to stimuli, and the properties of muscle, nervous, and glandular tissues. Understand excitability and the transition of excitation.

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