Exam 4 - ANS and Hormones Flashcards
Autonomic Nervous System
Part of the motor division of the peripheral nervous system responsible for involuntary (autonomic) responses and for maintaining internal homeostasis
Target Tissues of the ANS
The ANS is the efferent (outflowing) innervation of tissues other than skeletal muscle (visceral nervous system), influencing every organ in the body. The target tissues include cardiac muscle (heart rate), smooth muscle (circulatory system, arteries, blood pressure, blood flow), adipocytes, and glands (endocrine and exocrine glands).
Visceral motor neurons of the ANS
- Two neurons: Presynaptic/ preganglionic and postsynaptic/ postganglionic
- 1st neuron has its cell body in the grey matter of the CNS and travels to a ganglion where it synapses with the 2nd neuron
- 2nd neuron travels to target tissue
- 1st neuron is myelinated, 2nd is not
- This pathway can create either an inhibitory or excitatory response
- Dual innervation occurs
Ganglion
Bundle of cell bodies in the peripheral nervous system
Dual innervation
- The sympathetic and parasympathetic nervous systems regulate the same tissues
- Not all organs or target tissues are innervated by both sides of the ANS (i.e., adrenal gland and glucose stimulation only from sympathetic division)
Enteric division
Division of the ANS: Gut nervous system (GI tract)
iNANC division
Division of the ANS: Respiratory nervous system
Sympathetic division of the ANS
Responsible for “fight or flight”
Parasympathetic division of the ANS
Responsible for “rest or digest” and “feed and breed”
Sympathetic division organization
- Preganglionic neurons: All originate in grey matter of the spinal cord (T1-L2), travel out of the spinal cord via the ventral root and will synapse with a postganglionic neuron in 1 of 3 places
- Postganglionic neurons: Originate in 1 of 3 places: Sympathetic chain, collateral ganglia, adrenal
Sympathetic chain
- Where most of the synapses occur and where the majority of postsynaptic fibers originate
- Directly adjacent to the spinal cord on both sides
- Composed of interconnected ganglia
- Cell body is here and then they will travel to target tissue
- If this is the case, the pre-neuron is short and the post-neuron is long in order to travel the length of the spinal cord to target tissue
Collateral ganglia
- Located anterior to the spinal cord in the abdominal region (close to target organs of the stomach, intestines, pancreas, liver, kidney)
- Three types of ganglia (celiac, superior mesenteric, inferior mesenteric)
- If this is the case, the axons of the pre will physically pass through the sympathetic chain, nit not synapse with any of the neurons there… instead the axon continues into 1 of 3 collateral ganglia where it synapses with a post
Adrenal
- Special pathway creating a coordinated response between the nervous system and the endocrine system
- The pre synapses with the post within the adrenal gland
- Pre is very long (has to reach the adrenal gland (kidneys)) and it reaches the medulla and synapses with post
- Chromaffin cells are special, modified postganglionic cells that form an endocrine gland (receive the nervous system innervation and respond by secreting epinephrine (80%) and norepinephrine (20%) into the blood stream)
Epinephrine
Neurotransmitter secreted by the adrenal medulla in response to stress. Also known as adrenaline. Mainly impacts heart
Norepinephrine
Neurotransmitter secreted by the adrenal medulla in response to stress. Mainly impacts blood vessels
Three pathways within the sympathetic division
1.) Sympathetic chain: Most common, a short preganglionic cell synapses with a postganglionic within the sympathetic chain
2.) Collateral ganglia: In the abdominal region (closer to target organs), longer pre and shorter post
3.) Adrenal: Specialized, very long pre synapses with a chromaffin cell in the adrenal medulla that can create a neuroendocrine coordinated response
Parasympathetic division organization
- Two regions on parasympathetic outflow that sandwich the region of sympathetic outflow
1.) Cranial outflow: From the brainstem
2.) From the sacral region of the spinal cord - In either pathway, the preganglionic neurons have very long and myelinated (transmit the signal quickly over a long space) axons and the postganglionic neurons are very short and typically unmyelinated (close to target)
Cranial outflow
- Preganglion passes from the brainstem through 1 of 4 cranial nerves (all of which have motor function)
- III Oculomotor
- VII Facial
- IX Glossopharyngeal
- X Vagus
Spinal cord outflow
- Outflow around the S2-S4 sacral region
- Terminal ganglia: Ganglia between pre and post ganglionic neurons
Functional classification of neurons
Preganglionic/ postganglionic
Neurotransmitter release classification of neurons
- Cholinergic: Acetylcholine; all preganglionic cells (para and symp), all postganglionic neurons of the parasympathetic nervous system ( short ones)
- Adrenergic: Epinephrine (adrenaline) and norepinephrine; all postganglionic neurons of the parasympathetic nervous system (including chromaffin)
How do messages that originate in the CNS reach their target tissues
- ANS regulates tissues by releasing neurotransmitters (synaptic transmission is chemical)
- 2 different neurotransmitters for each pathway; one in between pre and post synaptic neurons and one in between post synaptic and target organ (effector)
Acetylcholine (cholinergic receptors)
- Two types:
1. Nicotinic (ionotropic)
2. Muscarinic (metabotropic)
If the fight or flight response mostly used a single hormone (epinephrine) to communicate a mass discharge throughout the whole body, how can opposite effects be produced? (i.e., vasoconstriction occurs to the GI tract while vasodilation occurs to the airway and skeletal muscles)
In order to produce opposite responses at each location of smooth muscle, we need different receptors (one neurotransmitter can bind to different receptors at different target tissues)
Nicotinic receptors
- On postganglionic neurons of both division
- Agonist: ACh, nicotine (both of these can bind to it)
- Ionotropic: Binds to an ion channel and causes a change in the ion channel (i.e., opening it up)
Muscarinic receptors
- On target organs of parasympathetic nervous system
- Agonist: ACh, muscarine
- When ACh binds to a metabotropic receptor, it causes a cascade of events within the cell
Epinephrine receptors (adrenergic)
- Four types:
- Beta 1/2, alpha 1/2
- Alpha
- Beta
- Beta 1
Alpha receptor
Peripheral; Brain and GI organs
Beta receptor
Supplies the heart, skeletal muscles, and lungs
Beta 1 receptor
Supplies cardiac muscle
Antagonist control
- The sympathetic and parasympathetic systems regulating tissues in opposite way (two opposite inputs)
- Not mutually exclusive
Tone
- The end product of the two divisions working together at any given time
- Most of the time, our normal function is a simultaneous input, creating a resting tone
“Fight or flight” response
- Sympathetic
- Physiological response to stressful situations
- Organized for mass discharge
- All responses coordinated by the neuroendocrine link
- Increased heart rate (increased blood flow to various tissues such as skeletal muscles)
- Constrict blood vessels in the GI tract and dilate BV in skeletal muscles (digestion not a primary concern)
- Increased respiration rate and dilation of air pathway (need oxygen)
- Sweating
Neuroendocrine link
The release of both epinephrine and norepinephrine to help responses occur simultaneously
“Rest and digest”
- Parasympathetic
- Not organized for mass discharge
- Decreased heart rate
- Increased GI activity/ dilate BV around GI
- Decreased respiration rate and airway constriction
- Sexual arousal
- SLUD (salivation, lacrimation, urination, and defecation) (and decrease HR and BP)
Neurohormones
Hormones secreted from neurons into the blood stream (chromaffin cells)
Receptor upregulation
Tissues place more receptors on a cell surface which increases sensitivity
Receptor downregulation
Cell removes receptors from the plasma membrane which decreases sensitivity
Peptide hormones
- Synthesized from DNA and made usable in a vesicle to be released
- DNA –> mRNA –> Preprohormone –> Prohormone –> Hormone
- Ex. Growth Hormone
Steroids
- Have a cholesterol backbone and are modified by enzymes to make it into a steroid hormone
- Sex steroids
- Cortical steroids
Sex steroids
Estrogen, progesterone, testosterone
Cortical steroids
Cortisol, aldosterone
Aldosterone
Electrolyte balance
Amine hormones
- Two types
1. Tyrosine
2. Tryptophan
Tyrosine
- Thyroid hormones: Thyroxine (secreted by thyroid gland)
- Catecholamines: Epinephrine (adrenal medulla), Norepinephrine (adrenal medulla), Dopamine (hypothalamus)
Tryptophan
- Melatonin (pineal gland)
G-Protein Coupled Receptors
- STUDY DIAGRAM
- Have an extracellular receptor specific for the function
- Inside the cell there are alpha, beta, and gamma subunits
- When epinephrine or norepinephrine binds and the GPCR is stimulated, an enzyme breaks up the 3 subunits
- 3 ways it can be stimulated: B Adrenergic, Alpha 2 Adrenergic, Alpha 1 Adrenergic
B Adrenergic (GPCR)
- Epinephrine or norepinephrine bind and adenylyl cyclase acts on the alpha stimulatory subunit –> Stimulates cAMP –> can stimulate CRE, CNGs, or protein kinase A
Alpha 2 Adrenergic Receptor (GPCR)
- Epinephrine or norepinephrine bind and alpha inhibitory is acted on by adenyl cyclase –> Inhibits cAMP –> inhibits CRE and CNA and PKA
Alpha 1 Adrenergic Receptor (GPCR)
- Epinephrine or norepinephrine bind and alpha q is acted on by phospholipase C –> Stimulates Pip2 which stimulates 1p3 and ca2+ OR stimulated DA6 and then protein kinase C
Describe the downstream signaling events that occur upon stimulation or inhibition of adrenergic receptors
Refer to class diagram
Describe a receptor tyrosine kinase
- Kinases are proteins that do phosphorylation (enzyme activation/ deactivation)
- The first messenger binds to the tyrosine kinase which then leads to a cascade of events inside the cell
- Not G protein mediated
- Kinases are directly couple to the receptor
- CML
CML
Leukemia medication that blocks the active site so that kinase cannot phosphorylate but the kinases can mutate as the cell grows
Lipid soluble hormones
- Steroid and thyroid hormones
- Can pass through the cell membrane so that they have their receptors inside the cell
- Need to be bound to a transport protein in the blood
- Long half life
Water soluble hormones
- Do not pass through the cell membrane so their receptors are on the outside of the cell
- They don’t need carrier proteins in the bloodstream
- Short half life
Endocrine system vs. nervous system
- NS: One cell to one or a couple cells, short duration and rapid recovery
- ES: One cell to many, long duration and long recovery
Classifications of hormonal regulation
- Change in plasma ion concentration
- Change in plasma nutrient concentration
- Neurotransmitter activation
- Circadian rhythms
- Other hormones
Change in plasma ion concentration
Ex.) Parathyroid hormone/ Calcitonin: Low calcium in the blood stimulated the release of PTH (Parathyroid gland) –> takes calcium from the bones and brings to the blood, high calcium in the blood stimulates the release of calcitonin (thyroid) –> brings calcium from the blood to the bones
Change in plasma nutrient concentration
Ex.) Insulin –> When blood glucose levels are it stimulates the release of insulin
Neurotransmitter activation
Chromaffin releases epinephrine
Circadian rhythms
Ex.) Melatonin secreted when darkness comes in
Permissiveness
When a hormone cannot work to its full potential without the presence of another hormone (ex. when thyroid hormone and epinephrine are used together, the amount of fatty acid released is much higher than when they’re alone: Thyroid hormone has a priming effect on adipose tissue)
Anterior pituitary
- Adenohypophysis
- Has epithelial tissue that is secreting the hormones and it is a neuroendocrine gland
Posterior pituitary
- Neurohypophysis
- Has nervous tissue that is secreting the hormones and it is a neuroendocrine gland
Neuroendocrine gland
Nerve but also a gland as part of the endocrine system
Releasing hormone
- First level
- Ex.) GHRH (growth hormone releasing hormone) or TRH
Tropic hormone
- Second level
- Ex.) GH (growth hormone), TSH
Effector hormone
- Last level
- Ex.) IGF-1 (Insulin-like growth factor)
Ultra short negative feedback loop
Releasing hormone on hypothalamus
Short negative feedback loop
Tropic hormone on hypothalamus (For growth hormone, short loop just inhibits hypothalamus)
Long negative feedback loop
Effector hormone on hypothalamus and anterior pituitary (For growth hormone long loop inhibits hypothalamus and anterior pituitary (somatometians))
Positive feedback loop (Breast milk)
- Prolactin regulates milk synthesis (triggered by infant sucking on breast)
- Oxytocin regulates milk let down (milk flows)
Regulation of growth hormone secretion
Growth hormone is release when…
- Low plasma glucose
- Raise plasma arginine (amino acids)
- Exercise, sleep, fasting
You can either inhibit the growth hormone releasing hormone or stimulate the growth hormone inhibiting hormone to inhibit
Direct effects of growth hormone
- Direct, effector functions: Increase the nutrients for ATP synthesis
- Glucose sparing effect
- Diabetogenic effect
Glucose sparing effect
Stimulate the lipolysis of fat which is used to make ATP
Diabetogenic effect
Stimulate liver to break down glycogen into glucose fueling growth effects
Indirect effects of growth hormone
- Indirect, tropic function (somatomedins) is growth
- Amino acid uptake, protein synthesis, cell growth and proliferation, reduction of apoptosis
Thyroid gland anatomy
- Two lobes connected by an isthmus that give butterfly shape
- Follicular cells, thyriglobulin, parafollicular cells
- Capillary plexus
Follicular cells
Thyroid hormones
Thyroglobulin
Chains of thyroid hormone
Parafollicular cells
Calcitonin
Capillary plexus
Blood supply of thyroid gland, basal faces blood and apical faces lumen
Thyroid Hormone regulation, synthesis, and secretion
- TRH regulates Thyroid hormone
- TSH stimulated thyroid hormone synthesis (TSH binds to a receptor on the basal membrane and stimulates thyroglobulin synthesis, iodine that enters the body is taken into follicular cells via secondary active transport with a sodium potassium pump, then moves to thyroid perioxiase where iodine is attached to an amino acid –> T3 or T4)
- Follicular cells go through pinocytosis and enzymes break down T3 and T4 allowing secretion into the bloodstream
Cellular effects of thyroid hormone
- Transcription of Na/K ATPase (increase oxygen consumption)
- Increased protein synthesis, glycogen breakdown, glucogenesis and fatty acid oxidation (growth and regeneration)
- Enhanced cholesterol sytnthesis (LDL uptake)
Systematic effects of thyroid hormone
- Increase BMR and heat production
- Synthesis of adrenergic receptors (permissiveness)
- Regulation of tissue growth and development
Different types of thyroid regulation
1.) Low TH levels: Stimulate TRH and TSH
2.) Low body temp: Stimulate TRH and TSH
Hyposecretion
Dwarfism: Can be caused by genes, tumors, and stress in pregnancy
Hypersecretion
- Can cause tumors
- Gigantism
- Acromegaly (Lots of bone width)
Hypothyroidism
- Cretinism: Short, disproportionate body
- Myxdema
- Tertiary causes: Dysfunctional hypothalamus
