Bahan Kuliah Fungsi Antar Sel
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Transcript of Bahan Kuliah Fungsi Antar Sel
• Chemical– Autocrine & Paracrine: local signaling– Endocrine system: distant, diffuse target
• Electrical– Gap junction: local– Nervous system: fast, specific, distant target
Cell to Cell Communication:
Paracrines and Autocrines
• Local communication • Signal chemicals
diffuse to target• Example: Cytokines
– Autocrine–receptor on same cell
– Paracrine–neighboring cells
Figure 6-1c: Direct and local cell-to-cell communication
• Signal Chemicals
• Made in endocrine cells
• Transported via blood
• Receptors on target cells
Long Distance Communication: Hormones
Figure 6-2a: Long distance cell-to-cell communication
• Neurons– Electrical signal down axon– Signal molecule (neurotransmitter) to target cell
• Neurohormones– Chemical and electrical signals down axon– Hormone transported via blood to target
Long Distance Communication: Neurons and Neurohormones
Figure 6-2 b: Long distance cell-to-cell communication
Long Distance Communication: Neurons and Neurohormones
Figure 6-2b, c: Long distance cell-to-cell communication
Gap Junctions and CAMs• Protein channels -
connexin
• Direct flow to neighbor– Electrical- ions (charge)– Signal chemicals
• CAMs – Need direct surface
contact– Signal chemical
Figure 6-1a, b: Direct and local cell-to-cell communication
Signal Pathways
• Signal molecule (ligand)
• Receptor
• Intracellular signal
• Target protein
• Response
Figure 6-3: Signal pathways
Endocrine Reflex Pathways: Overview
Figure 7-9: Hormones may have multiple stimuli for their release
Receptor locations• Cytosolic or Nuclear
– Lipophilic ligand enters cell
– Often activates gene
– Slower response
• Cell membrane– Lipophobic ligand
can't enter cell
– Outer surface receptor
– Fast response Figure 6-4: Target cell receptors
• Membrane associated enzymes– External reactions– Internal reactions
• Receptors bind specific ligand– Example:
Hormones– Cell recognition
moleculesFigure 5-6: Cell membrane receptor
Homeostasis & Controls
• Successful compensation– Homeostasis
reestablished
• Failure to compensate– Pathophysiology
• Illness• Death
Figure 1-5: Homeostasis
ENDOCRINE SYSTEM
• Uses chemical signals for cell to cell communication
• Coordinates the function of cells
• Response to an endocrine signal occurs within minutes to hours
Chemical Regulating Systems: Overview
• Pheromones: organism to organism communication
• Hormones: cell to cell communication molecules– Made in gland(s) or cells– Transported by blood– Distant target tissue receptors– Activates physiological response
HORMONE CLASSIFICATION
• Protein and polypeptide
• Amine
• Steroid
PEPTIDE HORMONES
• Consist of specific amino acids
• Synthesized as large precursor proteins
• Stored in membrane-enclosed compartments
• Hydrophillic
• Surface receptor• Hormone binds• Transduction• Enzyme activation• Open channels• Second messenger
systems• Synthesis
Protein and Polypeptide Hormone Receptors
Figure 7-5: Membrane receptors for peptide hormones
Receptors– Surface– Intracellular
• Small size, OH group
• Benzine ring
• Examples– Thyroxin– Epinephrine
Amine Hormones
STEROID HORMONES
• Precursor: Cholesterol
• Lipophillic
• Immediately released from the cell following synthesis
• Cytoplasmic or nuclear receptors (mostly)
• Activate DNA for protein synthesis
• Slower acting, longer half-life
• Examples: cortisol, estrogen & testosterone
Steroid Hormones
Steroid Hormones: Action
Figure 7-7: Steroid hormone action
Summary of the Endocrine System
Figure 7-2-1: ANATOMY SUMMARY: Hormones
HYPOTHALAMUS
• Integrates functions that maintain chemical and temperature homeostasis
• Functions with the limbic system
• Controls the release of hormones from the anterior and posterior pituitary
HYPOTHALAMUS
• Synthesizes hypophysiotropic hormones in cell bodies of neurons located in the hypothalamus
• Transports hormones down the axon and stored in the nerve endings
• Secretion of hormones is in pulses
HYPOTHALAMUS: Secretion of Hypophysiotropic Hormones
• Is influenced by emotions
• Can be influenced by the metabolic state of the individual
• Delivered to the anterior pituitary via the hypothalamic-hypophyseal portal system
• Usually initiates a three-hormone sequence
Figure 11-3: Autonomic control centers in the brain
HYPOTHALAMUS
Synthesizes & releases hypophysiotropic hormones:– Thyrotropin-releasing hormone (TRH)– Corticotropin-releasing hormone (CRH)– Gonadotropin-releasing hormone (GnRH)– Growth hormone-releasing hormone (GHRH)– Growth hormone-inhibiting hormone (GHIH)– Prolactin-releasing factor (PRF)– Prolactin-inhibitn hormone (PIH)
Endocrine Control: Three Levels of Integration
Figure 7-13: Hormones of the hypothalamic-anterior pituitary pathway
Negative Feedback Controls: Long & Short Loop Reflexes
Figure 7-14: Negative feedback loops in the hypothalamicanterior
pituitary pathway
Negative Feedback Controls: Long & Short Loop Reflexes
Figure 7-15: Control pathway for cortisol secretion
ANTERIOR PITUITARY HORMONES
Growth Hormone (GH, Somatotropin): primary hormone responsible for regulating body growth, and is important in metabolism
Thyroid-stimulating Hormone (TSH): stimulates secretion of thyroid hormone & growth of thyroid gland
Adrenocorticotropic Hormone (ACTH): stimulates cortisol secretion by the adrenal cortex & promotes growth of adrenal cortex
ANTERIOR PITUITARY
Follicle-stimulating Hormone (FSH): Females: stimulates growth & development of ovarian follicles, promotes secretion of estrogen by ovaries. Males: required for sperm production
Luteinizing Hormone (LH): Females: responsible for ovulation, formation of corpus luteum in the ovary, and regulation of ovarian secretion of female sex hormones. Males: stimulates cell in the testes to secrete testosterone
Prolactin: Females: stimulates breast development and milk production. Males: involved in testicular function
• Hypothalamic stimulation–from CNS • Pituitary stimulation–from hypothalamic trophic Hs• Endocrine gland stimulation–from pituitary trophic
Hs
Endocrine Control: Three Levels of Integration
Pathologies: Over or Under Production
Figure 7-19: Negative feedback by exogenous cortisol
POSTERIOR PITUITARY
Comprised of the endings of axons from cell bodies in the hypothalamus (supraoptic and paraventricular)
Axons pass from the hypothalamus to the posterior pituitary via the hypothalamohypophysial tract
Posterior pituitary hormones are synthesized in the cell bodies of neurons in the supraoptic and paraventricular nuclei
POSTERIOR PITUITARY
Hormones synthesized in the hypothalamus are transported down the axons to the endings in the posterior pituitary
Hormones are stored in vesicles in the posterior pituitary until release into the circulation
Principal Hormones: Vasopressin & Oxytocin
Figure 7-12: Synthesis, storage, and release of posterior pituitary hormones
POSTERIOR PITUITARY
Oxytocin:
Synthesized as the precursor hormone: prepro-oxyphysin
Action primarily on the breasts and uterus
Increases contraction of smooth muscle of Vas Deferens
POSTERIOR PITUITARY
Vasopressin
Plasma osmolality is monitored by osmoreceptors in the hypothalamus
Increases in plasma osmolality stimulates secretion of vasopressin
Small changes above normal plasma osmotic pressure ( 285 mosm/kg) stimulate release of vasopressin
POSTERIOR PITUITARY
Vasopressin secretion also stimulated by:
1. Large decreases in blood volume
2. Decreases in blood pressure
POSTERIOR PITUITARY
Vasopression Action:
Decreases water excretion by kidneys (V2 receptors)
Constricts blood vessels (V1 receptors)
Increases adrenocorticortropin Hormone (V1B receptors)