Flashcards in Autoendocrine System Deck (114):
What are the two parts of the nervous system?
CNS: Brain and spinal cord
PNS: nerves that go to different parts of the body (cranial and spinal nerves)
What is the CNS made up of?
Brain and spinal cord
What is the PNS made up of?
Nerves that go to different parts of the body from the spinal cord:
Cranial and spinal nerves
What are ganglia?
Some nerves come out from the spinal cord and go out to switching stations to connect with other nerves that go out to other tissues. These switching stations are called ganglia.
What are peripheral nerves?
Very fine nerves that go out to all our tissues in the periphery.
What do we call nerves that bring in information to the CNS?
Sensory (afferent) neurons
What do we call the nerves that go from our brain to our spinal cord to other nerves?
Motor (efferent) neurons
What are the two types of motor neurons?
What do somatic neurones innervate?
What is the autonomic system divided into?
Sympathetic and parasympathetic
What is the purpose of the autonomic nervous system?
To respond to changes in the circumstances.
What does the autonomic system innervate?
Cardiac muscle, smooth muscle and glands
Where do most cell bodies lie?
In the spinal cord
What is a myelin sheath?
Layers of insulation wrapped around some but not all axons.
What would we see if we sliced across an axon with a myelin sheath?
A cell type that strongly associates with the axon called Schwann cell that wraps layers of its membrane around the axon, which is full of a protein called myelin.
What is the function of the myelin sheath?
Insulates the axons so that the nerve impulse will travel along the axon and not diverge out to the sides.
How are unmyelinated axons associated with Schwann cells?
In not such an intimate way. Several axons are associated with a Schwann cell.
How does a synapse occur?
Electrochemical signal travels to knob, and changes the structure of transmembrane proteins so that calcium ions can move into the knob through voltage-gated calcium channels. The calcium ions trigger changes that cause vesicles containing neurotransmitters to move and fuse with the membrane of the presynaptic neurone and release the contents. Neurotransmitters travel across synaptic cleft and bind to receptors on postsynaptic membrane that causes these membrane proteins to change shape leading to sodium ion influx that changes the charge of that region.
When does a synapse occur?
Between two nerves
Between a nerve and a muscle
Between a nerve and a gland
What do nerves do?
Coordinate our actions and bodily functions.
What occurs to the heart, eyes, mouth, lungs, skin, gut, and blood during the alarm response?
Heart: increase rate and contraction force (BP increases)
Eyes: dilate pupils so we are more aware of our surroundings
Mouth: decrease saliva because digestion is not important
Lungs: dilate bronchi and faster breathing
Skin: constrict peripheral blood vessels (more blood pumped into muscles), contract arrector pili muscles, increase sweat secretion to cool body
Gut: decrease digestion
Increase blood sugar for more energy.
Increase blood pressure and water retention.
What happens during the relaxation response?
Heart: decrease rate and contraction force
Eyes: contract pupils
Mouth: increase saliva
Lungs: constrict bronchi
Skin: dilate peripheral blood vessels
Gut: increase digestion
What is the fight, flight, freeze response?
Once we sense a potential threat, our body responds with a chain of reactions. First, it activates the sympathetic autonomic nervous system. The brain sends an electrical signal to the adrenal glands which flood the body with adrenaline. This initiates a short term energy burst needed to respond to the emergency.
How long does the alarm response take?
What is the collective name for the responses due to different situations?
What is another name for autonomic?
What does the autonomic system control?
Body's internal responses
What are the two divisions of the autonomic nervous system?
Sympathetic and parasympathetic
What is the sympathetic division of the autonomic nervous system associated with?
What is the parasympathetic division of the autonomic nervous system associated with?
Where does the somatic system get sensory input from?
Where does the autonomic system get sensory input from?
Interoreceptors (internal sensing)
How do we control the output of the somatic system?
Voluntary: cerebral cortex
How do we control the output of the autonomic system?
Involuntary: limbic system, hypothalamus, brain stem, spinal cord
What are the effectors of the somatic system?
What are the effectors of the autonomic system?
Smooth muscle, cardiac muscle, glands
Describe the structure of the somatic nervous system.
Nerves start off with cell body in spinal cord. Myelinated axons go out to tissues they affect. Single neurone pathway.
What neurotransmitter is used by the somatic nervous system?
What is the structure of the autonomic nervous system?
2 neurone pathway: Cell body in the spinal cord with myelinated axons does not directly go to the tissue. The preganglionic neurone goes to a ganglion switching station. It synapses with various nerves in the ganglion which radiate out to the various tissues. These are postganglionic unmyelinated neurones.
What are the two neurotransmitters used in the autonomic nervous system?
Acetyl choline (between preganglionic neurone and ganglion)
Norepinephrine/Noradrenaline (between postganglionic neurone and effector cell)
What is the exception to the use of two neurotransmitters in the autonomic nervous system?
In the sympathetic division, the neurotransmitter between the postganglionic neurone and the sweat gland cell is acetylcholine.
In the parasympathetic division, the neurotransmitter between the postganglionic neurone and the effector cell is acetylcholine.
Why is the autonomic system an inducible system?
There is always some basal activity, but we can turn it up when needed and turn it down when not needed.
Describe Raynaud disease
Excessive sympathetic stimulation following emotional stress or exposure to cold. Chronic vasoconstriction. Fingers and toes become ischaemic (lack of blood) and appear white.
What does the hypothalamus use to control internal organs?
Autonomic nervous system and pituitary gland
What is the endocrine system?
A global control system that uses hormones in our blood stream rather than nerves.
What does the hypothalamus regulate?
Behaviour patterns, circadian rhythm (sleep/wake cycles), body temperature, eating and drinking behaviour
What are endocrine organs?
Organs that secrete or respond to hormones.
Give examples the components of the endocrine system
Hypothalamus, pineal gland, pituitary, thyroid, thymus, skin, heart, liver, stomach, adrenal glands, stomach, pancreas, small intestine, ovary, testes
What forms the trunk of the endocrine system?
Hypothalamus, pituitary and adrenal glands (HPA axis)
What are hormones?
Molecules that cells produce to control the activity of some parts of the body.
What is meant by endocrine?
To produce something at one cell and affect something some distance away.
What are endocrine hormones?
Hormones produced at an endocrine cell and carried in blood to receptors on distant target cells.
What are paracrine hormones?
Hormones released by paracrine cells which travel a small distant to receptors on a nearby target cell.
What are autocrine hormones?
Hormones released by an autocrine cell, which act back on receptors of the same target cell.
Describe the control cycle of hormone release.
1) Synthesis, storage, and release of hormones occurs at the hormone-producing cell
2) Travels in blood
3) Desired response occurs at a target cell with receptors for specific hormones.
4) Hormone disposal (breakdown or excretion) and feedback signal (usually negative)
Where is the only region upon which a hormone can act?
A target cell with receptors for the hormone
How does the speed of the endocrine system compare to that of the autonomic system?
It is slower (seconds to minutes vs milliseconds)
What are the two fundamental types of hormones that cells can produce?
Lipid soluble hormones
How are lipi-soluble hormones carried in the blood? Why so?
They are transported associated with a soluble transport protein because they are themselves insoluble in the aqueous environment of blood.
What is the sequence of events when the lipid-soluble hormone reaches the target cell?
It diffuses across the lipid bilayer membrane into the cell. Cell is only affected if the cell has particular receptors that the hormone can bind to in the nucleus. The activated-receptor hormone complex alters gene expression by binding to promoter or inhibitor regions of genes. A different set of proteins is made so the cell activity is altered.
What is the sequence of events when water-soluble hormones reach the target cell?
Cannot diffuse through bilayer so binds to receptors on the surface of the cell. The receptor is linked by a transmembrane protein to an intracytoplasmic molecule called a G protein which activates an enzyme on the inside of the membrane called adenylyl cyclase. It converts ATP to cAMP which acts on protein kinases that phosphorylate other proteins (e.g. enzymes). This changes the activity of these proteins. Phosphorylated enzymes catalyse reactions that produce physiological responses.
What is the first messenger and second messenger of the sequence of events occurring when water-soluble hormones bind to target cells?
What happens when the water-soluble hormone is removed?
The G protein deactivates the adenylyl cyclase, reducing the level of cAMP, inactivating the protein kinase, dephosphorylating the enzymes, and reducing activity of the enzyme.
What is cholera?
Bacterial infection where the bacteria grow in the crypts of the small intestine and release metabolites, among which is the cholera toxin.
What is the mechanism by which the cholera toxin attacks the body?
The cholera toxin binds to the epithelial cell G proteins associated with the hormone receptors. This locks them into an activated state, so they make high levels of cAMP. This causes the gut epithelial cells to pump chloride ions out form the blood into the small intestine lumen. This causes water to follow out. This leads to chronic diarrhoea.
What is the hypothalamus made up of?
What are the lobes hanging off the hypotahlamus called?
Posterior and anterior pituitary
What connects the hypothalamus and the pituitary?
What overlays the base of the hypothalamus and the pituitary?
A bed of capillaries.
What connects the beds of capillaries of the hypothalamus and the pituitary?
The hypophyseal portal veins
How do hormones travel from the hypothalamus to the pituitary?
Diffuse out from the hypothalamus into the capillary bed. Hormones pass down the hypophyseal portal veins into the capillary bed (secondary plexus) of the anterior pituitary. The hormones then diffuse into the anterior pituitary. This either induces or inhibits hormone release from the anterior pituitary into the blood.
What does the hypothalamus release?
9 hormones: releasing and inhibiting hormones to control pituitary.
What does the pituitary release?
7 hormones: controlling endocrine organs
What do the hypothalamus and pituitary together control?
Regulate growth, development, metabolism, homeostasis.
What kind of system exists between the hypothalamus and the pituitary?
Portal system: Capillaries -> portal vein -> capillaries
Where are the adrenal glands found?
Lying on top of the kidneys.
List the layers found from the outside to the inside of the adrenal gland.
How does the medulla affect the alarm response?
Activation and production of neurotransmitter hormones from the adrenal medulla act to extend and sustain the alarm response (activation of sympathetic autonomic system)
Describe how the sympathetic neurones can effect the medulla.
Sympathetic preganglionic neurones synapse with the adrenal medulla, which triggers them to release two neurotransmitters: epinephrine and norepinephrine into the blood. The facilitates and sustains the alarm response.
What do preganglionic neurones synapse with in the medulla?
Modified postganglionic neurones acting as secretory cells.
What is the adrenal medulla stimulated by?
Acetylcholine from preganglionic neurones.
What hormones are released from the adrenal medulla?
Epinephrine and norepinephrine
What are the principal actions of the adrenal medulla?
Enhance sympathetic autonomic alarm response.
What is the first stage of the stress response? Describe it
Alarm (Fight-or-flight) response:
Sympathetic autonomic activation
Sustained through action of adrenal medulla
Describe sympathetic autonomic activation
Mobilise resources (glucose and oxygen) for immediate physical activity. Results in alertness and activity and reduced tissue damage to ward off danger or flee.
What are the two types of hormones secreted by the adrenal cortex? Give examples
Mineralocorticoids (e.g. aldosterone)
Glucocorticoids (e.g. cortisol)
What is meant by mineralocorticoids?
Mineralo: to do with controlling concentrations of metal ions
Corticoids: to do with the adrenal cortex.
What are mineralocorticoids stimulated by?
Increased K+ and angiotensin II in blood
What are the principal actions of mineralocorticoids?
Increase Na+ and water and decrease K+ in blood. This increases blood volume and pressure.
What are glucocorticoids stimulated by?
ACTH from pituitary (CRH from hypothalamus)
What is meant by gluco of glucocorticoids?
Gluco: to do with carbohydrate metabolism
What is another name for glucocorticoids?
What is CRH and ACTH and how are they linked?
Corticotropin releasing hormone made by the hypothalamus acts on the pituitary to trigger the release of adrenocorticotropic hormone which travels around the blood to the adrenal cortex where it triggers the release of cortisol.
What are the principal actions of cortisol?
Resistance reaction to stress
Alter immune responses so that the body is not producing substances that are not required.
What is the second step of the stress response?
Resistance reaction to stress
How does cortisol affect protein breakdown? What are the consequences?
Increases protein breakdown (especially in muscles). Amino acids available for new protein synthesis.
How does cortisol affect the liver and what are the consequences?
Increase of gluconeogenesis in the liver. Glucose available for ATP production.
What occurs in adipose tissue as a result of cortisol? What are the consequences?
Lipolysis increases so that triglycerides and fatty acids are available.
What is mean by resistance reaction to stress?
The change of the body's physiology to focus on the short term needs of the body to deal with immediate danger and focus less on the long term processes.
How are the blood vessels effected by cortisol? What is a consequence of this?
Altered blood vessel sensitivity to vasoconstriction increases blood pressure so that blood reaches the places it needs to.
What is the overall purpose of the list of actions of cortisol?
To up regulate processes to increase the reformation of tissue.
What is the effect of cortisol on tissues?
Anti-inflammatory to limit tissue damage. Slower tissue repair and wound healing.
How does cortisol affect the immune system?
Altered immune responsiveness so increased susceptibility to infection.
Is the action of cortisol fast or slow?
Describe how the CRH - ACTH - Cortisol pathway is a negative feedback mechanism.
Elevated cortisol inhibits the release of CRH by hypothalamic neurosecretory cells.
It also inhibits the release of ACTH by the anterior pituitary corticotrophs.
The hormone is also excreted or broken down.
Describe the two stages of the stress response.
Alarm response: immediate burst, sympathetic activaiton and adrenal medulla
Resistance reaction: slower, longer lasting, associated with hypothalamus, pituitary and adrenal cortex
How are the activities of the immune system coordinated by the neuroendocrine?
Hormones (e.g. cortisol)
How are the activities of the neuroendocrine system coordinated by the immune system?
Cytokines (immune hormones)
Describe the cave person adaptations.
Short-term remedial action (change relationship to world)
Threat system arousal: blood (energy), muscle (motor), vigilance (sensory)
Dampen unnecessary: immunity and digestion
What are the two types of stress?
Prepares us to meet certain challenges. Helpful and beneficial to change our physiology to help us solve problems.
Associated with undesirable events. Potentially harmful.
How are hostility and the heart related?
Habitually hostile people have long-term sympathetic activation. The heart works harder and capillaries are constricted. There is a greater risk of cardiac infarct (heart attack).