Flashcards in Autonomic and Endocrine Systems Deck (88):
What makes up the CNS?
What makes up the PNS?
What are afferent nerves?
Nerves which bring impulses from the PNS to the CNS
What are efferent nerves?
Nerves which take impulses from the CNS to the PNS
What are the different types of motor neuron?
What do somatic motor neurons control?
Voluntary motion via skeletal muscle
What do autonomic nerves involve?
The sympathetic (fight/flight) and parasympathetic (rest/digest) branches.
These alter cardiac and smooth muscle as well as glands, to continue to live under various conditions
What are the three main parts of a neuron, and what are they made of?
Axon (much longer in proportion to cell body)
All made of cytoplasm.
What is the difference between myelinated and unmyelinated neurons?
Myelinated neurons have a schwann cell literally wrapped around the axon, with myelin interfacing around the axon
Unmyelinated neurons have a single schwann cell wrapped around many axons, to hold them together, but no myelin involved.
What is the function of nerves?
They cooordinate our action and bodily functions, to allow us to respond to stimuli
What are the steps of nerve impulse conduction?
1. Impulse arrives at presynaptic membrane, depolarizing and opening voltage gated Ca2+ channels.
2. Ca2+ encourages vesicles of neurotransmitters to bind to the presynaptic membrane and leave into the synaptic cleft via exocytosis
3. Neurotransmitters bind to ligand-gated channels in the postsynaptic membrane, causing it to depolarize due to inflow of Na+, causing the conduction of the impulse
(All this happens within milliseconds)
What is involved with the alarm response and what causes it?
Caused by the sympathetic branch of the ANS
- Increased HR & contractility
- Contraction of arrector pili muscles (hair stands on end) and increased secretion from sweat glands.
- Constriction of blood vessels in skin to send more blood to muscles
- Dilation of pupils for greater visual acuity
- Decreased salivation
- Dilation of bronchi
Increased blood sugar to give more glucose to muscles
- Increased BP and H2O retention
- Decreased digestion
- Increased resp. rate to increase O2 in the blood.
What is involved with the relaxation response and what causes it?
Caused by the parasympathetic branch of the ANS
- Decreased HR & contractility
- Contraction of pupils
- Increased salivation
- Dilation of peripheral blood vessels
- Constriction of bronchi
- Increased digestion
What are the sympathetic nerve responses associated with?
Why is sympathetic innervation important?
It gives the body the opportunity to be active
What are the parasympathetic responses associated with?
Why is parasympathetic innervation important?
It gives the body the opportunity to recuperate
Where does sensory input for the ANS come from?
Interoceptors detecting change in O2 levels, hinger, BP.
Some impulses from the somatic nervous system
Where does sensory input for the SNS come from?
Special senses and somatic senses
What controls ANS output?
Involuntary control by the limbic system, hypothalamus, brain stem and spinal cord, to change the body's environment.
What controls SNS output?
Voluntary cerebral cortex decisions- causes body movements
What is the motor pathway type in ANS?
Two neuron pathway- post- and pre-ganglionic pathways
What is the motor pathway type in SNS?
One neuron pathway- just LMNs
What are the neurotransmitters involved in the ANS, and what neurons use them?
ACh is used by preganglionic axons, postganglionic parasympathetic, and postganglionic sympathetic, although only to some sweat glands
Norepinephrine is used by postganglionic sympathetic fibres to places other than some sweat glands
What are the neurotransmitters involved in the SNS?
What are the effectors in the ANS?
Smooth and cardiac muscle, glands
What are the effectors in the SMS?
How are Parasympathetic and Sympathetic used in tandem?
Both are always active, but can be turned up and down like a dimmer.
When there is danger, symp. increases while parasymp. decreases and vice versa
This is important as if they are constantly in use, bad outcomes may result.
What is a similarity between ANS and SNS neurons?
Both start within the spinal cord
What are the differences between ANS and SNS neurons?
ANS has two neurons: The pre-ganglionic and post-ganglionic, of which only the pre-ganglionic is myelinated.
The two synapse in the autonomic ganglion, using ACh,
The SNS only has a single, myelinated neuron
Why is it important that the ANS synapses in the ganglia?
It allows a single signal from a pre-ganglionic neuron to be sent to multiple post-ganglionic neurons.
What does a cholinergic neuron use as a neurotransmitter?
What does an adrenergic neuron use as a neurotransmitter?
What does an adrenergic receptor accept as a neurotransmitter?
What does a muscarinic receptor accept as a neurotransmitter?
What is the pathology of reynaud's disease?
It is due to excessive sympathetic nervous activity due to stress or cold.
This causes chronic vasoconstriction in the fingers and toes, which become ischaemic and turn white
What is the function of the hypothalamus?
Controls internal organs via ANS and pituitary gland
Regulates behavioral patterns, circadian rhythms and the sleep/wake cycle
Controls body temp
Regulates eating and drinking
Regulates ANS and endocrine system
What are the major glands in the endocrine system?
What is the function of endocrine organs?
What are circulating hormones?
Molecules made by a cell of an endocrine organ to flow through the blood to affect cells somewhere else- distant.
What are the 2 types of local hormones?
Autocrines and paracrines
What are paracrine hormones?
Hormones produced by a cell of an endocrine organ which flows through the IF to a nearby target cell
What are autocrine hormones?
Hormones produced by a cell of an endocrine organ which acts on itself.
What is the feedback cycle of hormone production?
1. In endocrine tissues, hormones are synthesized, stored and released
2. Travel through blood
3. Elicit desired response from target cell with receptors for the specific hormone, by altering its function
4. Feedback signal
What are the 3 methods of getting rid of hormones?
1. Using them- so that their conc. decreases
2. Hormone disposal via breakdown/excretion
3. Feedback signal- the target tissue releases a signal to say 'yes, I've responded!', or the level of hormones in the blood is high enough to inhibit production of further hormones.
What are lipid-soluble hormones?
Hormones which are able to diffuse through the cell's membrane, but cannot be in blood alone, so must be carried by a water soluble transport protein
What are the steps of lipid-soluble hormones acting on a cell?
1. Lipid soluble hormone leaves its transport protein and diffuses into a cell through the bilayer.
2. If the nucleus of the cell has an appropriate receptor, the activated hormone-receptor complex alters gene expression via transcription to make new RNA in order to enact a structure/function change within the cell.
3. Newly formed mRNA directs synthesis of spec. proteins.
Without the hormone, structure/function reverts back.
What are some examples of lipid-soluble hormones?
Steroid hormones, thyroid hormones
What are water soluble hormones?
Hormones which are soluble in water, and so do not use transport proteins in the blood. However, they are unable to cross the lipid bilayer without a transport protein
What are the steps of water-soluble hormones acting on a cell?
1. If a cell has the specific receptor, the hormone will bind to it, activating a G protein, which activates adenyl cyclase
2. Conversion of ATP to cAMP, which acts as a second messenger
3. cAMP activates protein Kinase
4. Activated kinases begin a phosphorylation cascade
5. Phosphorylyzed encymes catalyze a reaction to produce physiological responses
6. When reaction is over, all messengers revert back, and the cell returns to normal function
What are some examples of water soluble hormones?
Catecholamines, peptides and proteins.
What connects the hypothalamus to the pituitary gland?
What are the two parts of the pituitary gland, and how do you distinguish them?
There is the anterior and the posterior pituitary. The anterior is located below the optic chasm, with the pituitary behind it.
What does the hypothalamus do in terms of hormones?
It produces 9 hormones, which are releasing or inhibiting. It controls the release of hormones from the pituitary gland
What does the pituitary gland do in terms of hormones?
It produces 7 hormones to control the endocrine organs.
What do the hypothalamus and pituitary gland do collectively?
Regulate growth, development, metabolism and homeostasis.
How do the hypothalamus and anterior pituitary gland communicate?
Via the hypophyseal portal veins (primary on hypo, secondary on pit). This is a system which delivers blood from the capillaries on the hypothalamus to the capillaries on the anterior pituitary, as well as the hormones within the blood.
The hormones produced in the anterior pituitary are then released into the blood, which flows through the rest of the body.
How do the hypothalamus and the posterior pituitary gland communicate?
The hypothalamus produces 2 hormones, and sends them as neurotransmitters via neurons between the two. This action potential causes the posterior pituitary to release the neurotransmitter hormones into the blood, sending them around the body.
What are chromaffin cells?
They are modified postganglionic neurons, acting as secretory cells
They are located in the adrenal medulla
What do chromaffin cells do?
They secrete epi and norepi directly into the bloodstream
How are chromaffin cells activated?
A preganglionic neuron terminates at these cells, which then produce and release epi/NE.
What hormones are produced by the adrenal medulla?
Epi and Norepi
What stimulates the adrenal medulla to produce its hormones?
ACh released by preganglionic neurons stimulates Epi and NE
What are the principal actions of epi and norepi (of adrenal medulla)?
Enhances sympathetic ANS alarm response
What hormones are produced by the adrenal cortex?
Mineralocorticoids (eg. aldosterone)
Glucocorticoids (eg. cortisol)
What stimulates the release of mineralocorticoids from the adrenal cortex?
Increased K+ and angiotensin II in the blood
What stimulates the release of glucocorticoids from the adrenal cortex?
ACTH from the pituitary gland. This is stimulated by CRH from the hypothalamus
What are the principal actions of mineralocorticoids?
Increase blood Na+ and water retention, to increase blood volume. Decreased K+ in blood to increase blood pressure by controlling osmolarity
What are the principal actions of glucocorticoids in from the adrenal cortex?
Resistance reaction to stress, dampening inflammation and immune responses so that we don't expend energy on things we don't need.
What is the negative feedback mechanism for cortisol in the hypothalamus/pituitary?
1. Hypothalamus releases 'cortisol releasing hormone (CRH)' via the portal veins.
2. Corticotrophin (ACTH) released from the anterior pituitary and released into the bloodstream
3. Adrenal cortex produces cortisol
4. The increased level of cortisol inhibits the production of ACTH in the anterior pituitary
5. Increased cortisol also inhibits the production of CRH by the hypothalamus.
What are the 7 actions of cortisol in terms of the stress response?
- Protein breakdown
- Resistance to stress
- Immune depression
What is protein breakdown (due to glucocorticoids)?
Increased protein breakdown in muscle fibres- amino acids released into blood to be used for synthesis of new protein to rebuild, or ATP
What is gluconeogenesis (due to glucocorticoids)?
Liver cells convert some amino acids or lactic acids to glucose, to be used for ATP
What is lipolysis (due to glucocorticoids)?
Breakdown of triglycerides and release of fatty acids from adipose tissue into the blood, to be used to build more tissue
What is resistance to stress (due to glucocorticoids)?
Increased glucose and ATP to respond to stressors such as exercise, fasting, fright, extreme temp., high altitude, bleeding, infection, surgery, trauma and dis-ease
What is vasoconstriction (due to glucocorticoids)?
Blood vessels are more sensitive to hormones causing vasoconstriction, leading to increased blood pressure, allowing more blood to be diverted to essential organs
What is anti-inflammatory (due to glucocorticoids)?
Inhibition of white blood cells to limit tissue damage due to their actions- however, if this is too acute it can retard tissue repair and healing, so it is important to have a balance.
What is immune depression? (due to glucocorticoids)
Stops immune cells functioning as much- used as a therapy following organ transplants to decrease graft rejection.
What are features of the stress response?
- Sympathetic ANS activation
- Mobilize resources for immediate physical activity
- Glucose and oxygen consumption increases
- Alertness and activity increaes
- Fight or flight
- Reduction in damage to tissues
What are the two steps of the stress response?
- Resistance reaction
What is the fight-or-flight stage of the stress response?
- Immediate burst of hormones/activity
- Sympathetic ANS activation
- Involvement of the adrenal medulla
- Production of Epi and Norepi to extend the alarm response
- Essentially, it's the mixing of the nervous and adrenal responses.
What is the resistance reaction of the stress response?
- Slow, long lasting
- Associated with HPA axis
- Cortisol production
What are the two pathways of the stress response when a stressor is applied?
Pathway 1: Fight/Flight
2. Sympathetic nerve activation using NE as postganglionic neurotransmitter
4. Adrenal medulla activated, secreting Epi and NE. Visceral effectors affected (heart, liver, vasculature etc).
5. Alarm response of rapid HR, cold sweat, pale skin, goosebumps and rapid breathing. It's extended by Epi and NE.
Pathway 2: Resistance
6. Neurosecretory cells release CRH into primary hypophyseal plexus, through portal vein to ant. pituitary
7. Ant. Pit. produces ACTH and releases into bloodstream
8. Reaches adrenal cortex, which releases cortisol into the bloodstream
9. Resistance reaction of increased glucose, fatty acids and amino acids. Sensitization of vessels, and reduced inflammatory and immune responses
10. High levels of cortisol in the blood after stressor removal
11. High levels inhibit ACTH and CRH secretion
How does the neuro-endocrine system affect the immune system?
- ANS post ganglionic nerves alters the body's response to antigens
- Hormones such as cortisol alter the balance of responsiveness
How does the immune system affect the neuroendocrine system?
Via cytokines, which influence how the nervous system responds.
What is the difference between eustress and distress?
Eustress is acute stress, which can be helpful and prepare us for challenges
Distress is chronic stress, where the alarm response is sustained, with the potential to cause harm.
Overall, what does the stress response do, and what does it promote and inhibit?
It takes short-term remedial action to change our relationship to the world.
It promotes energy in the blood, movement through our muscles, and vigilance via our senses.
It inhibits unnecessary actions, such as immune responses and digestion