Homeostasis and Hemostasia PDF

# Homeostasis and Hemostasia ## Homeostasis - Mechanisms that maintain the internal environment. - Maintain physiological variables within appropriate limits. ### Variables fisiologicas: - **Glucemia** - **CO2** - **Volemia** - **Temperatura** - **PA** - **O2** - **Dolor** ## Hemostasia - Mechani...

# Homeostasis and Hemostasia ## Homeostasis - Mechanisms that maintain the internal environment. - Maintain physiological variables within appropriate limits. ### Variables fisiologicas: - **Glucemia** - **CO2** - **Volemia** - **Temperatura** - **PA** - **O2** - **Dolor** ## Hemostasia - Mechanisms that prevent blood loss. - Depends on: - Vessel wall - Platelets - Coagulation factors ## Agua - Fundamental element of life. - Contributes fluids to glandular secretions. - Universal solvent. - Transports nutrients and waste products. - Dilutes food during digestion and absorption. - Regulates temperature. - Maintains volemia, blood pressure, and renal function. - Maintains normal electrolyte concentrations. - **Total Body Water (TBW):** 60% of body weight. ### Factors that affect TBW: - Body fat - Age - Sex - Pregnancy - Pregnancy related changes: - Increased blood volume - Decreased physiological blood pressure ## Distribution of TBW - **Intracellular fluid (ICF):** 35% - **Extracellular fluid (ECF):** 21-25% - Interstitial fluid: 17% of TBW. - Plasma: 4-5% of TBW. ## Compartment Composition | | Intravascular | Interstitial | LIC | |--------------|--------------|-------------|------------------| | **K** | 4 mEq/L | 3.5-5.5 | 140 mEq/L | | **Na** | 142 mEq/L | 135-145 mEq/L | 10 mEq/L | | **Cl** | 101 mEq/L | 103 mEq/L | 4 mEq/L | | **HCO3** | 22-28 mEq/L | | | | **Ca2** | 2.4 mEq/L | | | | **Proteins** | 2gr/dL | 1gr/dL | 0.0001 mEq/L | ## Blood Volume - Blood volume: 4-4.5% of TBW. - Plasma volume: 4-5% of TBW. - Hematocrit: 45% ## Lymph - Lymphatic fluid: 2% of TBW. - Contains lymphocytes, proteins, and fats. ## Transcellular spaces - ~1-3% of TBW. - Located between serous membranes. - ~ 100 ml volume. - Examples: cerebrospinal fluid, gastrointestinal fluids, amniotic fluid, humors of the eye. ## Derrame - Accumulation of excess fluid in a body cavity. ## Edema - Fluid accumulation in the interstitial space. ## Types of Derrame - **Transudate:** Poor in protein and cells. Caused by imbalances in pressure and osmotic gradient, without inflammation. - **Exudate:** Rich in protein and cells. Associated with inflammation, increased vascular permeability. ## Method of Dilution Indicator - A known substance is injected into a compartment. - The substance distributes evenly in the compartment. - Concentration of the substance measured. - Formula: V=Q/C - V: Volume of compartment - Q: Quantity of indicator - C: Concentration of the indicator ## Types of Indicators - TBW: 3H2O, 2H2O, urea. - ECF: 22Na+ - Plasma volume: Albumin labelled with iodine or Evans blue. ## Fick's Law - The volume of distribution of a substance in a compartment is equal to the total quantity of the substance divided by its concentration in that compartment. ## Balance Hidrico - Equilibrium between water intake and loss. ### Water intake - Exogeneous water: Drinking - Endogeneous water: 300-400 ml/day. Produced by metabolism, primarily in form of oxygen used in respiration. ### Water losses - Respiration: 500 ml/day - Skin: 500 ml/day - Urine: 800-2000 ml/day - Feces: 100 ml/day - **Insensible losses (IL):** 700-900 ml/day - Adults: 15 ml/kg/day - Children: 30 ml/kg/day ### Water Imbalance - Disruption of the physiological balance between water intake and loss. ## Potassium - More concentrated in the ICF. - Maintains resting and membrane potential. - Contributes to muscle excitability. - Regulates acid-base balance. - Contributes to renal function. ## Sodium - More concentrated in the ECF. - Maintains fluid and electrolyte balance. - Contributes to nerve conduction and muscle contraction. - Influences blood volume and pressure. ## Albumin and Globulins - Contribute to blood viscosity. - Provide nutrition to tissues. - Contribute to osmotic pressure. - Assist with membrane transport. - Participate in blood coagulation. - Contribute to oncotic/colloid osmotic pressure. - Contribute to blood transport. - Contribute to digestion. - Assist with muscle contraction and movement. - Regulate gene expression, protein production, and cell function. - Contributed to the expression of DNA and RNA. ## Exchange between compartments - Depends on: - Membrane characteristics: - Impermeable: No movement across the membrane. - Permeable: Substances can move freely across the membrane. - Semipermeable: Allows only certain substances to pass. - Properties of molecules. ### Osmosis - Movement of solvent across a semipermeable membrane. - Regulates solute concentration on both sides of the membrane. ## Osmolarity of body fluids - Plasma osmolarity: 270-310 mOsm/L. - Hypertonic solutions: Cause cells to shrink, losing water. - Isotonic solutions: Maintain normal cell volume. - Hypotonic solution: Cause cells to swell, gaining water. ## Capillaries - Capillaries are the smallest blood vessels, responsible for exchange. - ~ 100 µm diameter. ### Types of capillaries - **Continuous capillaries:** Tight junctions. Most tissues. - **Fenestrated capillaries:** Pores through cells. Small intestine, glomerulus, endocrine glands. - **Discontinuous capillaries:** Large gaps between cells. Liver, spleen, bone marrow. ## Capillary Control - **Neural control:** - Sympathetic nerves: Release norepinephrine, which causes vasoconstriction. - Parasympathetic nerves: Release acetylcholine, which causes vasodilation. - Endothelial cells: Release vasoconstrictors (endothelin, angiotensin II) and vasodilators (NO, prostacyclin). - **Local control:** - **Metabolic:** Respond to changes in oxygen and carbon dioxide levels, pH, and nutrients. - **Myogenic:** Respond to changes in vessel wall tension, regulating blood flow. ## Starling equilibrium - Equilibrium of flow across the capillary wall between filtration and absorption. - The net fluid movement is usually absorbed, preventing edema. - Disruption of the equilibrium causes edema. ## Oncotic Pressure - Type of osmotic pressure exerted by proteins. - Proteins in the blood attract water, opposing hydrostatic pressure. - Maintains fluid within the blood vessels. ## Edema - Excess fluid buildup in the interstitial space. - Can be caused by: - Increased capillary permeability: Allergies, burns, toxins. - Decreased plasma proteins: Liver disease, malnutrition, protein-losing enteropathy. - Increased capillary pressure: Heart failure, venous obstruction. - Lymphatic obstruction: Tumors, infections, surgery. # Vision - The sense of sight. - Highly important, as 70% of sensory receptors are located in the eye. ## Structure of the Eye - **Eyeball:** Spherical, ~24 mm diameter, ~7.5 g weight. - **Eyelids:** Protect the eye. - **Eyebrows:** Prevent sweat and debris from entering the eye. - **Eyelashes:** Trap dust particles. - **Lacrimal apparatus:** Produces tears, which lubricate the eye and remove debris. ### Layer of the eyeball - **Outer layer:** - **Cornea**: Transparent, allows light to enter the eye. - **Sclera**: White, tough, provides structural support. - **Conjunctiva**: Thin membrane, covers the sclera and inner eyelid. - **Middle layer:** - **Choroid**: Vascular layer, nourishes the retina. - **Iris**: Colored part of the eye, regulates pupil size. - **Ciliary body**: Controls lens shape for focusing. - **Inner layer:** - **Retina**: Contains photoreceptor cells (rods and cones) for light detection. ## Retina - Contains light-sensitive cells. - Consists of photoreceptor cells (rods and cones), bipolar cells, and ganglion cells. - **Rods:** Sensitive to low light, responsible for night vision. - **Cones:** Sensitive to colors, responsible for bright light and color vision. - **Fovea:** Central part of the retina, contains a high density of cones, providing the sharpest vision. - **Optic nerve:** Carries visual information from the retina to the brain. ## Visual pathway - Light enters the eye. - Photoreceptor cells in the retina convert light into electrical signals. - Signals are processed through the optic nerve. - Signals reach the optic chiasm, where information from each eye is combined. - Signals travel to the thalamus, a relay center. - Signals are sent to the visual cortex in the occipital lobe of the brain. ## Color vision - Human eye contains three types of cones: red, green, and blue. - Each cone is sensitive to a range of wavelengths. - Color perception is based on the relative activation of the cones. ## Visual field - The area of space that can be seen with both eyes open. - 130° upward, 70° downwards, and 150° across the horizontal plane. ## Blind spot - The area where the optic nerve connects to the retina. - No photoreceptor cells are present. - Cannot see objects in this area. ## Visual disorders - **Myopia (nearsightedness):** Eyeball is too long. Difficulty focusing on distant objects. - **Hyperopia (farsightedness):** Eyeball is too short. Difficulty focusing on near objects. - **Astigmatism:** Irregular curvature of the cornea or lens. Blurred vision. - **Presbyopia:** Age-related loss of elasticity, difficulty focusing. - **Macular degeneration:** Damage to the macula, central vision loss. - **Cataracts:** Clouding of the lens. Blurry vision. - **Glaucoma:** Increased pressure in the eye. Can lead to optic nerve damage and blindness. - **Diabetic retinopathy:** Damage to blood vessels in the retina. - **Low vision:** Significant vision loss, corrected with glasses or surgery. # Audición - The sense of hearing. ## Structure of the ear - The ear is divided into three parts: outer ear, middle ear, and inner ear. ### Outer ear - **Pinna:** Collects sound waves. - **External auditory canal:** Directs sound waves to the eardrum. ### Middle ear - **Tympanic membrane (eardrum):** Vibrates in response to sound waves. - **Ossicles:** Three small bones (malleus, incus, and stapes) that amplify sound vibrations. - **Eustachian tube:** Connects the middle ear to the back of the throat, equalizes pressure. ### Inner ear - **Cochlea:** Spinal-shaped structure containing fluid and hair cells that convert sound waves into electrical signals. - **Vestibular system:** Contains organs responsible for balance and spatial orientation. ## Mechanism of hearing 1. **Sound waves enter the outer ear:** The pinna collects sound waves and directs them through the external auditory canal. 2. **Sound waves reach the tympanic membrane:** Vibrations cause the tympanic membrane to move. 3. **Vibrations are transferred to the ossicles:** The malleus, incus, and stapes amplify the vibrations and transfer them to the oval window of the cochlea. 4. **Fluid waves in the cochlea:** Vibrations at the oval window generate fluid waves within the cochlea. 5. **Hair cells detect fluid waves:** The basilar membrane within the cochlea vibrates in response to the fluid waves, bending the hair cells on top of it. 6. **Hair cells convert mechanical energy into electrical signals:** The bending of the hair cells triggers a release of neurotransmitters, which generate electrical signals that travel through the auditory nerve to the brain. 7. **Brain interprets signals:** The auditory cortex in the brain receives and interprets the electrical signals, providing the sense of hearing. ## Auditory pathway - Sound waves are collected by the outer ear. - Vibrations are transmitted through the middle ear. - Vibrations are converted into electrical signals in the inner ear. - Electrical signals travel through the auditory nerve. - Signals are processed in the brainstem. - Signals are relayed to the thalamus. - Signals are sent to the auditory cortex in the temporal lobe of the brain. ## Auditory disorders - **Conductive hearing loss:** Sound waves cannot reach the inner ear. - **Sensorineural hearing loss:** Damage to the inner ear or auditory nerve. - **Presbycusis:** Age-related hearing loss. - **Tinnitus:** Ringing or buzzing in the ears. - **Meniere's Disease:** Fluid buildup in the inner ear. # Olfato - Chemical sense that detects odorants. - Important for survival: - Detects dangerous substances (spoiled food, smoke). - Plays a role in social interactions and communication. ## Structure of the olfactory system - **Nose:** Entrance for air and odorant molecules. - **Nasal cavity:** Contains turbinates, which increase surface area for air flow and odorant detection. - **Olfactory epithelium:** Lines the roof of the nasal cavity, contains olfactory receptor cells. - **Olfactory bulb:** Located below the frontal lobe, receives signals from olfactory receptor cells. - **Olfactory tract:** Pathway from the olfactory bulb to the brain. ## Olfactory receptor cells - Specialized neurons that bind to odorant molecules. - Each receptor cell is sensitive to a specific type of odorant molecule. - Humans have 400 different types of olfactory receptors. - Cilia extend from receptor cells, increasing surface area for odorant detection. - Odorant molecules bind to receptors on cilia, initiating a signal cascade. - This cascade triggers electrical signals that travel through olfactory nerves to the olfactory bulb. ## Olfactory pathway - Odorant molecules enter the nose. - They dissolve in the mucus lining the nasal cavity. - They encounter olfactory receptor cells in the olfactory epithelium. - They bind to receptors, generating a signal. - The signal is transmitted through the olfactory bulb. - The signal is sent to the olfactory cortex, located in the temporal lobe of the brain. - The olfactory cortex is responsible for odor recognition, discrimination, and memory. ## Olfactory disorders - **Anosmia:** Complete loss of smell. - **Hyposmia:** Reduced sense of smell. - **Dysosmia:** Distortion of smell. - **Phantosmia:** Hallucinations of smell. # Gusto - Chemical sense that detects tastants. - Allows for taste perception, a crucial part of food enjoyment and safety. ## Structure of the gustatory system - **Tongue:** Primary organ for taste perception. - **Taste buds:** Aggregates of taste receptor cells inside papillae on the tongue. - **Papillae:** Different types of projections on the tongue. - Circumvallate: Large, circular, located in the back of the tongue. - Foliate: Fold-like, located on the sides of the tongue. - Fungiform: Mushroom-shaped, located on the anterior part of the tongue. - Filiform: Thread-like, lack taste buds, responsible for texture perception. ## Taste receptor cells - Located within taste buds. - Have microvilli that extend into taste pores, increasing surface area for tastant detection. - Each taste receptor cell is sensitive to one of five basic tastes: - **Sweet:** Sugars, artificial sweeteners. - **Salty:** Sodium chloride, other salts. - **Sour:** Acids. - **Bitter:** Alkaloids, caffeine. - **Umami:** Glutamate, other amino acids, found in savory foods. ## Taste perception - Tasting is a complex process that involves taste buds and olfactory receptor cells. - Taste buds transduce chemical signals into electrical signals. - Signals are transmitted through cranial nerves. - Signals are relayed to the gustatory cortex in the brain. ## Gustatory pathway - Tastant molecules dissolve in saliva. - They reach taste receptor cells in the taste buds. - Receptor cells trigger electrical signals. - Signals travel through cranial nerves (facial nerve, glossopharyngeal nerve, vagus nerve). - Signals reach the gustatory cortex in the temporal lobe of the brain. - The brain integrates taste information with olfactory input to create the perception of flavor. ## Gustatory disorders - **Ageusia:** Complete loss of taste. - **Hypogeusia:** Reduced sense of taste. - **Dysgeusia:** Distorted perception of taste. # Eje Hipothalamus-Hypophysis - A system of glands and organs that regulate important physiological functions, including growth, metabolism, reproduction, and stress response. - Hypothalamus: Part of the brain, controls the release of hormones from the pituitary gland. - Pituitary gland: Located at the base of the brain, releases hormones that act on other glands. - These two organs interact through a complex feedback system. ## Hypothalamus - Controls the release of hormones from the pituitary gland, also called "the master gland." - Plays a role in maintaining homeostasis. ### Hypothalamus nuclei: - **Supraoptic nucleus:** Produces vasopressin (ADH) and oxytocin. - **Paraventricular nucleus:** Produces oxytocin and vasopressin. - **Arcuate nucleus:** Produces gonadotropin releasing hormone (GnRH), growth hormone releasing hormone (GHRH), and dopamine. - **Suprachiasmatic nucleus:** Regulates circadian rhythm. - **Ventromedial nucleus:** Regulates satiety and metabolism. - **Lateral nucleus:** Regulates hunger and thirst. - **Preoptic nucleus:** Regulates temperature and GnRH secretion. - **Dorsomedial nucleus:** Regulates aggression, emotional behavior, and feeding. - **Mammillary nucleus:** Involved in memory, learning, and sexual behavior. - **Tuberoinfundibular nucleus:** Produces dopamine, which inhibits prolactin release. ## Pituitary gland - Controls the release of other hormones. - Located at the base of the brain. - Divided into two lobes: - **Anterior pituitary (adenohipofisis):** Secretes hormones that act directly on other organs. - **Posterior pituitary (neurohipofisis):** Releases hormones produced by the hypothalamus. ### Hormones secreted by the anterior pituitary: * **Growth hormone (GH):** Regulates growth, cell division, and metabolism. * **Thyroid-stimulating hormone (TSH):** Stimulates the thyroid gland to release thyroid hormones. * **Adrenocorticotropic hormone (ACTH):** Stimulates the adrenal glands to release cortisol. * **Prolactin (PRL):** Stimulates milk production in breasts. * **Follicle-stimulating hormone (FSH):** Regulates the development of egg cells in females and sperm cells in males. * **Luteinizing hormone (LH):** Stimulates ovulation in females and testosterone production in males. ### Hormones secreted by the posterior pituitary: - **Antidiuretic hormone (ADH) or Vasopressin:** Regulates water reabsorption in the kidneys, affecting blood pressure. - **Oxytocin:** Stimulates uterine contractions in labor, milk ejection, and social bonding. ## Connections between the hypothalamus and the pituitary gland - **Neural connection:** Hormones are transported via nerve fibers from the hypothalamus to the posterior pituitary (neurohipofisis). - **Vascular connection:** Hormones are transported via blood vessels from the hypothalamus to the anterior pituitary (adenohipofisis). ## Regulation of the hypothamalus-pituitary axis - This axis functions through a complex feedback loop. - The hypothalamus releases hormones that control hormone secretion by the pituitary gland. - Hypothalamic hormone release is influenced by feedback from the target glands. - Other hormones from the body or environment also regulate this axis. ## Disorders of the hypothamalus-pituitary axis - **Hypothalamic disorders:** - **Hypopituitarism:** Decreased secretion of pituitary hormones. - **Diabetes insipidus:** Deficiency in ADH production, leading to excessive urination. - **Syndrome of inappropriate antidiuretic hormone secretion (SIADH):** Overproduction of ADH, leading to water retention and hyponatremia. - **Hypothalamic amenorrhea:** Disruption of menstrual cycles due to hypothalamic dysfunction. - **Pituitary disorders:** - **Pituitary tumors:** Can cause excess or deficiency of pituitary hormones. - **Sheehan's syndrome:** Hypopituitarism after postpartum hemorrhage. # Somatosensory System - Provides information about touch, temperature, pain, and the position of the body in space. - Includes the skin, muscles, tendons, joints, and internal organs. ## Structure of the somatosensory system - **Sensory receptors:** Specialized cells that detect stimuli. - **Sensory neurons:** Nerve cells that transmit signals from receptors to the spinal cord and brain. - **Spinal cord:** Receives and relays sensory information to the brain. - **Thalamus:** Sensory relay center in the brain, which processes and sends information to the somatosensory cortex. - **Somatosensory cortex:** Located in the parietal lobe of the brain, receives and interprets sensory information. ## Sensory receptors - **Mechanoreceptors:** Detect touch, pressure, vibration, and stretch. - **Merkel discs:** Detect light touch and pressure. - **Meissner corpuscles:** Detect fine touch and vibration. - **Pacinian corpuscles:** Detect deep pressure and vibration. - **Ruffini endings:** Detect stretching and pressure. - **Hair follicle receptors:** Detect movement and pressure on hair. - **Thermoreceptors:** Detect changes in temperature. - **Cold receptors:** Detect cold temperatures. - **Warm receptors:** Detect warm temperatures. - **Nociceptors:** Detect pain. - **Free nerve endings:** Detect pain, temperature, and pressure extremes. ## Sensory pathways - **Spinal cord:** Sensory neurons transmit signals to the spinal cord. - **Dorsal column-medial lemniscus pathway:** Carries signals for touch, pressure, vibration, and proprioception. - **Spinothalamic pathway:** Carries signals for pain and temperature. - **Thalamus:** Sensory signals from the spinal cord are relayed to the thalamus. - **Somatosensory cortex:** The thalamus sends signals to the somatosensory cortex for processing and interpretation. ## Somatosensory cortex - Located in the parietal lobe of the brain. - Organized according to a "homunculus" map, where different parts of the body are represented. - Areas with greater sensitivity have larger representations. - **Primary somatosensory cortex (S1):** Receives sensory input from the thalamus. - **Secondary somatosensory cortex (S2):** Processes information from S1 and other cortical areas. - **Somatosensory association cortex:** Integrates sensory information from multiple sources. ## Sensory perception - The process of interpreting and understanding sensory information. - Depends on: - **Sensory receptors:** Detect stimuli. - **Sensory neurons:** Transmit signals. - **Brain:** Processes signals and interprets them. ## Somatosensory disorders - **Pain disorders:** Can be caused by injury, inflammation, or disease. - **Neuropathies:** Damage to nerves, affecting sensation. - **Central pain syndrome:** Chronic pain caused by damage to the central nervous system. - **Sensory neglect:** Inability to perceive or respond to stimuli on one side of the body. ## Proprioception - The sense of body position and movement in space. - Involve mechanoreceptors in muscles, joints, and tendons. - Helps with: - Balance and coordination. - Fine motor movements. - Awareness of our location. - Spatial orientation. - Plays a critical role in movement, coordination, and motor control. ## Plasticity - The ability of the somatosensory system to adapt and reorganize in response to experience. - Can occur after: - Injury - Learning - Training - Adaptation - Changes in the environment. ## Somatosensory cortex plasticity - Can change the size and function of different cortical areas. - Plays a critical role in: - Learning new motor skills. - Recovering function after injury. - Adapting to changes in the environment.