Anatomy and Physiology II Unit 14 Review: Integration and Coordination

Key Concepts and Terminology

• Action potential: electrical signal that propagates along the axon of a neuron, enabling communication between neurons and other cells
• Neurotransmitters: chemical messengers released by neurons that bind to receptors on target cells, altering their activity (acetylcholine, dopamine, serotonin)
• Synapse: junction between two neurons or between a neuron and another cell type where neurotransmitters are released and received
• Hormone: chemical messenger secreted by endocrine glands into the bloodstream, regulating various physiological processes
• Homeostasis: maintenance of relatively stable internal conditions despite changes in the external environment
  • Achieved through negative feedback loops that counteract deviations from the set point
  • Positive feedback loops amplify changes and are less common (childbirth, blood clotting)
• Hypothalamus: region of the brain that integrates nervous and endocrine systems by controlling the pituitary gland and regulating various homeostatic processes (body temperature, hunger, thirst)
• Pituitary gland: master endocrine gland located at the base of the brain that secretes hormones regulating growth, metabolism, and other endocrine glands

Nervous System Overview

• Central nervous system (CNS): consists of the brain and spinal cord, processes information and generates responses
• Peripheral nervous system (PNS): consists of nerves that connect the CNS to the rest of the body, transmitting signals to and from the CNS
  • Somatic nervous system: controls voluntary movements and receives sensory input from the external environment
  • Autonomic nervous system: regulates involuntary functions (heart rate, digestion, respiration)
    • Sympathetic division: prepares the body for "fight or flight" responses
    • Parasympathetic division: promotes "rest and digest" activities
• Neurons: specialized cells that transmit electrical and chemical signals
  • Sensory neurons: convey information from sensory receptors to the CNS
  • Motor neurons: carry signals from the CNS to muscles and glands
  • Interneurons: connect sensory and motor neurons, processing information within the CNS
• Glial cells: support and protect neurons, maintain homeostasis, and participate in signal transmission (astrocytes, oligodendrocytes, Schwann cells)

Endocrine System Basics

• Endocrine glands: ductless glands that secrete hormones directly into the bloodstream (pituitary, thyroid, adrenal, pancreas)
• Hormones: classified by chemical structure
  • Peptide hormones: composed of amino acids, water-soluble (insulin, growth hormone)
  • Steroid hormones: derived from cholesterol, lipid-soluble (estrogen, testosterone, cortisol)
• Hormone receptors: specific proteins on target cells that bind to hormones, initiating cellular responses
  • Cell surface receptors: bind water-soluble hormones and activate second messenger systems
  • Intracellular receptors: bind lipid-soluble hormones and directly influence gene expression
• Hormone regulation: achieved through negative feedback loops involving the hypothalamus, pituitary, and target glands
  • Tropic hormones: released by the pituitary to stimulate other endocrine glands (thyroid-stimulating hormone, adrenocorticotropic hormone)
• Endocrine disorders: result from hormone imbalances (hyperthyroidism, diabetes mellitus, Cushing's syndrome)

Homeostasis and Feedback Loops

• Set point: optimal level or range for a physiological variable (body temperature, blood glucose, blood pressure)
• Sensors: detect changes in the internal environment and send signals to the control center (thermoreceptors, chemoreceptors, baroreceptors)
• Control center: receives input from sensors and generates appropriate responses to maintain homeostasis (hypothalamus, medulla oblongata)
• Effectors: carry out the responses generated by the control center to restore homeostasis (muscles, glands, organs)
• Negative feedback: mechanism that counteracts deviations from the set point to maintain stability
  • Example: regulation of blood glucose levels by insulin and glucagon
• Positive feedback: mechanism that amplifies changes, leading to a rapid response or end point
  • Example: oxytocin release during childbirth, causing uterine contractions and further oxytocin release
• Feedforward regulation: anticipatory mechanism that initiates responses before homeostasis is disrupted (increased heart rate and respiration before exercise)

Integration of Nervous and Endocrine Systems

• Hypothalamus: key integrator of nervous and endocrine systems
  • Contains neurosecretory cells that synthesize and release hormones (antidiuretic hormone, oxytocin)
  • Regulates the anterior pituitary through releasing and inhibiting hormones (corticotropin-releasing hormone, growth hormone-releasing hormone)
• Autonomic nervous system: modulates endocrine function
  • Sympathetic stimulation: increases secretion of adrenal medullary hormones (epinephrine, norepinephrine)
  • Parasympathetic stimulation: promotes digestion and energy storage, influencing insulin secretion
• Hormonal influence on nervous system: hormones can modulate neuronal activity and development
  • Thyroid hormones: essential for normal brain development and function
  • Sex hormones: influence sexual differentiation of the brain and behavior
• Stress response: coordinated activation of the hypothalamic-pituitary-adrenal axis and sympathetic nervous system
  • Corticotropin-releasing hormone stimulates adrenocorticotropic hormone release, leading to cortisol secretion
  • Cortisol mobilizes energy reserves and suppresses immune function

Coordination of Body Functions

• Circadian rhythms: daily cycles of physiological processes regulated by the suprachiasmatic nucleus in the hypothalamus
  • Melatonin secretion by the pineal gland: promotes sleep and entrains circadian rhythms to light-dark cycles
• Reproductive function: coordinated by the hypothalamic-pituitary-gonadal axis
  • Gonadotropin-releasing hormone stimulates the release of follicle-stimulating hormone and luteinizing hormone
  • Sex hormones (estrogen, testosterone) regulate reproductive development, menstrual cycle, and spermatogenesis
• Metabolism and energy balance: regulated by the hypothalamus and various hormones
  • Leptin: adipose tissue hormone that signals energy reserves to the hypothalamus, suppressing appetite
  • Ghrelin: stomach hormone that stimulates appetite and promotes food intake
  • Thyroid hormones: increase basal metabolic rate and stimulate catabolism
• Cardiovascular and respiratory control: mediated by the medulla oblongata and autonomic nervous system
  • Baroreceptor reflex: maintains blood pressure homeostasis by adjusting heart rate and vascular tone
  • Chemoreceptor reflex: regulates respiration based on blood levels of oxygen, carbon dioxide, and pH

Clinical Applications and Disorders

• Diabetes mellitus: disorder of glucose metabolism caused by insufficient insulin secretion (type 1) or insulin resistance (type 2)
  • Complications: cardiovascular disease, neuropathy, nephropathy, retinopathy
• Thyroid disorders: result from excessive (hyperthyroidism) or deficient (hypothyroidism) thyroid hormone production
  • Graves' disease: autoimmune disorder causing hyperthyroidism
  • Hashimoto's thyroiditis: autoimmune disorder causing hypothyroidism
• Adrenal disorders: involve abnormalities in the secretion of adrenal hormones
  • Addison's disease: primary adrenal insufficiency, leading to deficiencies in cortisol and aldosterone
  • Cushing's syndrome: excessive cortisol production, often due to long-term glucocorticoid therapy
• Neurological disorders: affect the structure or function of the nervous system
  • Alzheimer's disease: progressive neurodegenerative disorder characterized by memory loss and cognitive decline
  • Parkinson's disease: movement disorder caused by the loss of dopaminergic neurons in the substantia nigra
  • Multiple sclerosis: autoimmune disorder that damages the myelin sheath surrounding nerve fibers

Study Tips and Review Questions

• Create a concept map linking the nervous and endocrine systems, highlighting their interactions and shared functions
• Use mnemonic devices to remember the functions of key hormones and neurotransmitters (e.g., "FLAT PE" for the effects of sympathetic activation: Fear, Liver glycogenolysis, Adrenaline release, Tachycardia, Pupil dilation, Ejaculation)
• Practice drawing and labeling diagrams of the brain, spinal cord, and major endocrine glands
• Summarize the steps involved in a negative feedback loop, using specific examples from the nervous and endocrine systems
• Compare and contrast the actions of the sympathetic and parasympathetic divisions of the autonomic nervous system
• Explain how the hypothalamus integrates nervous and endocrine functions, providing specific examples of hormones and their effects
• Describe the role of the nervous and endocrine systems in maintaining homeostasis, using examples such as blood glucose regulation and the stress response
• Review the key features and functions of neurons, neurotransmitters, and hormones, and how they enable communication within and between the nervous and endocrine systems