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Questions and Answers
Which hormone is primarily responsible for regulating circadian rhythms?
Which hormone is primarily responsible for regulating circadian rhythms?
Steroid hormones exert their effects by binding to receptors located on the cell membrane.
Steroid hormones exert their effects by binding to receptors located on the cell membrane.
False
What are the two main controls for the release of Prolactin (PRL)?
What are the two main controls for the release of Prolactin (PRL)?
Prolactin-releasing factors and dopamine
The hormone __________, produced in the anterior pituitary gland, stimulates the adrenal cortex.
The hormone __________, produced in the anterior pituitary gland, stimulates the adrenal cortex.
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Match the anterior pituitary hormones with their primary targets:
Match the anterior pituitary hormones with their primary targets:
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Which neurohormone is produced by the hypothalamus to regulate the pituitary gland?
Which neurohormone is produced by the hypothalamus to regulate the pituitary gland?
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The mechanism of peptide hormones is characterized by rapid but short-lived effects.
The mechanism of peptide hormones is characterized by rapid but short-lived effects.
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What is the role of feedback loops in the endocrine system?
What is the role of feedback loops in the endocrine system?
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Where are peptide hormone receptors primarily located?
Where are peptide hormone receptors primarily located?
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Steroid hormones are stored in secretory vesicles before release.
Steroid hormones are stored in secretory vesicles before release.
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What is the mechanism of action for peptide hormones?
What is the mechanism of action for peptide hormones?
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Steroid hormones are synthesized on demand from __________.
Steroid hormones are synthesized on demand from __________.
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Which of these statements correctly describes the specificity of endocrine reflexes?
Which of these statements correctly describes the specificity of endocrine reflexes?
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The duration of endocrine signals is usually longer-lasting compared to neural signals.
The duration of endocrine signals is usually longer-lasting compared to neural signals.
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List one hormone released by the anterior pituitary gland and its target organ.
List one hormone released by the anterior pituitary gland and its target organ.
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The __________ nervous system mediates neural reflexes.
The __________ nervous system mediates neural reflexes.
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Match the hormone type with its characteristic:
Match the hormone type with its characteristic:
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How do steroid hormones primarily travel through the cell membrane?
How do steroid hormones primarily travel through the cell membrane?
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What is the main function of long-loop negative feedback in the endocrine system?
What is the main function of long-loop negative feedback in the endocrine system?
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Short-loop negative feedback is the primary mechanism for regulating endocrine functions.
Short-loop negative feedback is the primary mechanism for regulating endocrine functions.
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What are the three most common types of endocrine pathologies?
What are the three most common types of endocrine pathologies?
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In cases of low calcium levels, the ______ hormone is released to increase calcium levels.
In cases of low calcium levels, the ______ hormone is released to increase calcium levels.
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Match each type of negative feedback with its description:
Match each type of negative feedback with its description:
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Which of the following is an example of hyposecretion?
Which of the following is an example of hyposecretion?
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Functional antagonism refers to hormones that have opposing effects on the same physiological function.
Functional antagonism refers to hormones that have opposing effects on the same physiological function.
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What are the two divisions of the Peripheral Nervous System (PNS)?
What are the two divisions of the Peripheral Nervous System (PNS)?
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The ______ nervous system controls voluntary movements.
The ______ nervous system controls voluntary movements.
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Which statement about negative feedback in the endocrine system is correct?
Which statement about negative feedback in the endocrine system is correct?
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Which type of communication involves direct cytoplasmic connections between adjacent cells?
Which type of communication involves direct cytoplasmic connections between adjacent cells?
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Paracrine signaling affects cells that are not in close proximity to the signaling cell.
Paracrine signaling affects cells that are not in close proximity to the signaling cell.
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Name two forms of long-distance communication in the body.
Name two forms of long-distance communication in the body.
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Hormones are released into the __________ by the endocrine system.
Hormones are released into the __________ by the endocrine system.
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What is the result of the binding of lipophilic ligands to intracellular receptors?
What is the result of the binding of lipophilic ligands to intracellular receptors?
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Match the following receptor types with their characteristics:
Match the following receptor types with their characteristics:
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List the seven steps of a reflex control pathway.
List the seven steps of a reflex control pathway.
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Neurotransmitters are part of the endocrine system.
Neurotransmitters are part of the endocrine system.
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The __________ component of the nervous system relies on rapid, short-term effects through electrical signals.
The __________ component of the nervous system relies on rapid, short-term effects through electrical signals.
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What is the initial signal required for long-term potentiation?
What is the initial signal required for long-term potentiation?
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The blood-brain barrier allows all water-soluble compounds to freely cross.
The blood-brain barrier allows all water-soluble compounds to freely cross.
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Name the primary structure involved in the production of cerebrospinal fluid.
Name the primary structure involved in the production of cerebrospinal fluid.
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The _______ is crucial for calcium influx during long-term potentiation after the removal of Mg²⁺ block.
The _______ is crucial for calcium influx during long-term potentiation after the removal of Mg²⁺ block.
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Match the following structures of the brain with their functions:
Match the following structures of the brain with their functions:
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Study Notes
Local Communication
- Three forms of local communication exist: gap junctions, contact-dependent signals, and diffusing chemicals
- Gap junctions: Direct cytoplasmic connections between adjacent cells, allowing ions and small molecules to pass (e.g., cardiac muscle cells)
- Contact-dependent signals: Require cell-to-cell contact; cell adhesion molecules (CAMs)
- Diffusing chemicals:
- Paracrine signaling: Chemical signals released by a cell affect nearby cells, like histamine during inflammation
- Autocrine signaling: A cell releases a chemical that acts on itself (e.g., immune cells releasing interleukins)
Long-Distance Communication
- Two forms of long-distance communication exist: blood transport and neurochemicals
- Blood Transport: Substances transported through the bloodstream
- Endocrine System: Hormones released into the bloodstream, acting on distant targets (e.g., insulin regulating glucose levels)
- Neurochemicals:
- Neurotransmitters: Released by neurons into the synaptic cleft
- Neuromodulators: Modulate other neurons
- Neurohormones: Released by neurons into the blood for distant targets
- Nervous System: Electrical signals traveling along neurons, often followed by neurotransmitter release at synapses (e.g., motor neuron activation of a muscle)
Lipophilic Ligand Binding
- Ligand diffusion: Lipophilic ligands, like steroid hormones, diffuse through the cell membrane
Lipophobic Ligand Binding
- Ligand binding: A lipophobic ligand binds to a receptor on the cell surface
- Signal transduction: The receptor activates intracellular signaling pathways
- Second messenger activation: Intracellular messengers (e.g., cAMP, Ca2+) amplify the signal
- Cellular response: Changes occur in the cell (e.g., enzyme activation, ion channel changes)
Cell Surface Receptors
- Four major groups of cell surface receptors:
- Chemically gated (ligand-gated) ion channels: Respond to ligand binding by opening or closing, altering ion flow (e.g., nicotinic acetylcholine receptors)
- G Protein-Coupled Receptors (GPCRs): Activate intracellular G proteins, leading to second messenger production (e.g., adrenergic receptors)
- Receptor-Enzyme Complexes: Contain enzyme activity or are linked to enzymes (e.g., receptor tyrosine kinases like the insulin receptor).
Receptor Ligand Properties
- Specificity: Receptors bind specific ligands based on shape and chemical compatibility (e.g., insulin receptor binds only insulin)
- Competition: Different ligands can compete for the same receptor (e.g., beta-blockers and adrenaline for beta-adrenergic receptors)
- Affinity: Strength of ligand-receptor binding (high affinity ligands bind more strongly)
- Saturation: At high ligand concentrations, all receptors are occupied, and the response reaches a maximum
Reflex Control Pathways
- Seven steps in a reflex pathway: Stimulus, sensor, input signal, integrating center, output signal, effector, and response
- Stimulus: A detected change in the environment, sensed by a receptor
- Input signal: Sensory neuron transmits the signal to the integrating center
- Integrating center: Processes input and decides on a response
- Output signal: Motor neuron transmits the response signal
- Effector: The cell/organ that carries out the response
Neural vs Endocrine Reflexes
- Speed: Neural reflexes are very fast (milliseconds), endocrine reflexes are slow (minutes to hours)
- Specificity: Neural reflexes are highly specific, targeting particular cells; endocrine reflexes are broad, affecting all cells with the appropriate receptors
- Signals: Neural reflexes use electrical and chemical signals; endocrine reflexes use chemical signals (hormones in the bloodstream)
- Duration: Neural reflexes are short-lived; endocrine reflexes are longer-lasting
- Stimulus Intensity Coding: Neural reflexes code intensity by frequency of action potentials; endocrine reflexes code intensity by hormone concentration
Hormone Synthesis, Storage, and Release
- Peptide hormones: Synthesized in advance as preprohormones, stored in secretory vesicles, released by exocytosis
- Steroid hormones: Synthesized on demand from cholesterol, not stored, diffuse out of the cell immediately after synthesis
Hormone Receptors and Mechanisms of Action
- Peptide hormones: Receptors are located on the cell surface, and their mechanisms involve second messenger pathways, leading to rapid cellular responses
- Steroid hormones: Receptors are located in the cytoplasm or nucleus, and their mechanisms regulate gene expression, leading to slower, longer-lasting effects
Amine Hormones
- Three main groups of amine hormones (amino acid-derived): catecholamines, thyroid hormones, and melatonin
- Catecholamines (like epinephrine and norepinephrine): Derived from tyrosine; act like peptide hormones
- Thyroid hormones (like thyroxine and triiodothyronine): Derived from two tyrosine molecules; act like steroid hormones
- Melatonin: Derived from tryptophan; regulates circadian rhythms
Nervous System in Endocrine Reflexes
- Hypothalamus: Produces neurohormones to regulate the pituitary gland
- Neuroendocrine Reflexes: Electrical signals trigger hormone release (e.g., oxytocin during childbirth)
- Feedback loops: Coordinate hormonal and neural responses for homeostasis
Anterior Pituitary Hormones
- Six anterior pituitary hormones, their controls, and targets
- Prolactin (PRL), Thyrotropin/Thyroid-stimulating hormone (TSH), Adrenocorticotropin/adrenocorticotrophic hormone (ACTH), Growth hormone (GH), Follicle-stimulating hormone (FSH), Luteinizing hormone (LH)
Negative Feedback
- Long-loop negative feedback: Hormones from target endocrine glands inhibit the anterior pituitary and hypothalamus.
- Insulin feedback: High blood glucose stimulates insulin release, lowering blood glucose, and reducing the stimulus.
- Parathyroid hormone feedback: Low calcium levels stimulate parathyroid hormone release, increasing calcium, reducing hormone release
Endocrine Pathologies
- Common endocrine pathologies: Hypersecretion, hyposecretion, and abnormal target response (receptor/second messenger problems)
- Hypersecretion: Excessive hormone production; causes exaggerated effects
- Hyposecretion: Inadequate hormone production; can cause the overproduction of trophic hormones
- Abnormal Target Response: Target cells fail to respond appropriately (example: type 2 diabetes)
CNS and PNS
- Central Nervous System (CNS): Brain and spinal cord
- Peripheral Nervous System (PNS):
- Afferent division: Sensory input from receptors to the CNS
- Efferent division: Motor output
- Somatic Nervous System (SNS): Controls voluntary movements (skeletal muscles); usually voluntary
- Autonomic Nervous System (ANS): Controls involuntary activities (smooth muscle, cardiac muscle, glands), divided into Sympathetic and Parasympathetic divisions
- Enteric Nervous System (ENS): Network of neurons in the gastrointestinal tract
Glial Cells
- Astrocytes: Maintain the blood-brain barrier, regulate ion concentrations
- Oligodendrocytes: Myelinate CNS axons, increasing signal speed
- Microglia: Immune cells; remove debris and pathogens
- Ependymal cells: Source of neural stem cells,
- Schwann cells: Myelinate PNS axons; aid in repair
- Satellite cells: Surround neuronal cell bodies; provide support and nutrients
Graded Potentials and Action Potentials
- Graded Potentials: Local changes in membrane potential; vary in strength, decrease in strength as they spread, can be summed
- Action Potentials: Regenerating conduction signals; all-or-nothing phenomenon, cannot be summed, must reach threshold
Action Potential Changes
- Resting Phase: Resting membrane potential (~-70 mV), maintained by Na+/K+ pump and leak channels
- Depolarization: Voltage-gated Na+ channels open; Na+ influx causes the membrane potential to become more positive
- Repolarization: Voltage-gated Na+ channels close; voltage-gated K+ channels open; K+ efflux returns the membrane potential toward resting potential
- Hyperpolarization: K+ channels close slowly, causing an overshoot below resting potential before stabilizing
Refractory Periods
- Absolute refractory period: No new action potential can be initiated (Na+ channels are inactivated); prevents overlapping action potentials
- Relative refractory period: A greater-than-normal stimulus may trigger a new action potential, stronger depolarization needed
Synaptic Communication
- Ionotropic receptors: Ligand-gated ion channels, mediate fast synaptic transduction (e.g., AMPA receptors)
- Metabotropic receptors: G protein-coupled receptors, mediate slower, longer-lasting effects
- Neurotransmitters: Chemical messengers (e.g., glutamate, GABA, dopamine)
- Neuromodulators: Influence neurotransmitter release or receptor sensitivity
- Fast synaptic potentials: Brief changes in membrane potential due to ion flow
- Slow synaptic potentials: Longer-lasting changes mediated by second messengers (e.g., GPCRs)
- Excitatory Postsynaptic Potentials (EPSPs): Depolarize the membrane
- Inhibitory Postsynaptic Potentials (IPSPs): Hyperpolarize the membrane
Long-Term Potentiation (LTP)
- Initial signal: Glutamate binds to AMPA and NMDA receptors
- AMPA activation: Na+ influx through AMPA receptors causes depolarization
- NMDA activation: Depolarization removes the Mg2+ block from NMDA receptors, allowing Ca2+ influx
- Calcium role: Calcium activates intracellular signaling pathways, leading to enhanced synaptic transmission
Cerebrospinal Fluid (CSF)
- Formation: Produced by the choroid plexus in ventricles, via filtration of plasma through ependymal cells
- Distribution: Flows through the ventricles, enters the subarachnoid space, and is reabsorbed into venous circulation
- Functions: Chemical and physical protection (buoyancy, protection, homeostasis, transport)
Blood-Brain Barrier (BBB)
- Structure: Endothelial cells joined by tight junctions, astrocytic end-feet, and a basement membrane
- Functions: Selective permeability, protection from fluctuations in blood composition, homeostasis, and restriction of immune response
Cerebrum, Cerebellum, Diencephalon, Brain Stem
- Cerebrum: Two hemispheres; higher functions (sensory processing, motor control, language, memory)
- Cerebellum: Two hemispheres; coordinates movement
- Diencephalon: Interconnects cerebrum and brainstem; includes the thalamus, hypothalamus, pituitary, pineal glands
- Brain stem: Connects the cerebrum and cerebellum to the spinal cord; controls autonomic functions (heartbeat, breathing etc.)
Cerebral Cortex Lobes
- Four lobes: Frontal, Parietal, Temporal, Occipital
- Frontal lobe: Motor cortex, Broca's area, association areas (planning, decision-making)
- Parietal lobe: Primary somatosensory cortex; association areas for spatial awareness
- Temporal lobe: Primary auditory cortex, Wernicke's area, association areas for memory
- Occipital lobe: Primary visual cortex, visual association areas
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Description
This quiz explores the mechanisms of local and long-distance communication in biological systems. It covers gap junctions, contact-dependent signals, and chemical signaling, as well as blood transport and neurochemicals. Test your understanding of how cells interact and communicate across distances.
