Homeostasis Flashcards
(133 cards)
1
Q
What is Homeostasis?
A
keeping a steady state (composition, properties and functions) within the body.
2
Q
Living systems respond to stress from?
A
External environment, such as changes in temperature, food, light, predators, etc.
Internal environment, such as changes in water, waste, food, aging, etc
3
Q
What is needed to maintain homeostasis?
A
The system must be able to recognize the stress and respond to it.
Stimulus - receptor - regulator - effector
4
Q
Five properties common to biological systems?
A
- operates within limits
- Requires energy
- Use feedback systems
- Can experience overshoots (conditions outside optimal levels)
- Ability to correct errors
5
Q
Systems specifically involved in homeostasis?
A
- Endocrine system (glands adn hormones)
- Nervous System (central and peripheral)
- Excretory System (kidneys)
6
Q
Endocrine System
A
Secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth and behavior
7
Q
Excretory System
A
removes waste and maintains proper concentrations of various molecules
8
Q
Nervous System
A
Faster than hormones and not as long-lasting. Conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells.
9
Q
Hormones and Other signaling molecules bind?
A
Bind to target receptors, trigering specific response pathways. Endocrine signaling is just one of the several wats that information is transmitted between animal cells.
10
Q
Intercellular communication
A
The ways that signals are transmitted between animal cells are classified by two criteria.
- Type of secreting cell (nerve vs secretory)
- Route taken by signal in reaching target (blood or nerves)
11
Q
Endocrine Signaling
A
Hormones secreted into extracellular fluids by endocrine cells reach their targets via the bloodstream. Endocrine signaling maintains homeostasis, mediates respones to stimuli, regulates growth and devlopment
12
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Synaptic Signaling
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Neurons fform specialized junctions with target cells, called suynapses. at sunapses neurons secrete molecules called neurotransmitteres that diffuse short distances and bind to receptors on target cells
13
Q
Neuroendocrine Signaling
A
In neuroendocrine signaling, specialized neurosecretory cells secrete molecules called neurohormones that travel to target cells via the bloodstream
14
Q
Negative Feedback systems
A
(opposite) the system will do the opposite of what is happening to maintain body’s environment.
15
Q
Negative feedback loop
A
inhibits a response by reducing the initial stimulus, thus preventing excessive pathway activity ex. maintaining blood calcium levels at 9-11mg/dl
16
Q
positive feedback system
A
Change in the homeostatic condition is detected by reports and transmitted to the control center. The control center activates effectors which generate a res[pmse that increases the stimulus further reinforcing the initial change. Acts to reinforce or strengthen the stimulus or change.
17
Q
Thermoregulation
A
maintenance of body temeprature within a range that enables ells to funciton efficiently
18
Q
Ectotherms
A
Cold blood animals (eg. fish, amphibians, reptiles, invertebrates)
19
Q
Endotherms
A
Warm blood animals (mammals and birds)
20
Q
Hypothalamus
A
region in the brain responsible for coordinating many nerve adn hormone functions, including temperature regulation
21
Q
Response to heat stress
A
sensors in the brain detect a rise in body temp and send a nerve message in coordination within the hypothalamus. The signal is sent to sweat glands, result is sweat evaporation resulting in cooling.
the message is set to blood vessels in the skin, causing them to dilate, resulting in cooling.
22
Q
Response to Cold stress
A
Thermoreceptors in the skin send a message to the hypthalamus which in turn sends messages to other bodt parts to increase temperature. (ex. when you are cold and start to shiver body is shaking to warm up)
23
Q
Neurons
A
Basic structural and functional units of the nervous system. Respond to stimuli, conduct electrochemical signals and release regulating chemicals. Neurons are organized into tissues called nerves. `
24
Q
Glial Cells
A
support neurons by nourishing them, removing wastes, and defending against infection. They also function as structural support cells.
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Dendrites
short branching terminals that receive impulses and relay impulses to the cell body
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An Axon
conducts impulses away from the cell body and varies in length 1nm to over 1m
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A Cell Body
Contains the nucleus and is the site of the cell's metabolic reactions
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Branching nds
Found on dendrites and axons, they increase the surface area available for receiving and sending information
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Myelin Sheath
Insulated covering over the axon of nerve cells (provides protection)
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Multipolar
Has several dendrites, and has single axon, found in brain and spinal cord
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Bipolar
Single main dendrite, single axon, found in the inner ear, the retina of eye, and the olfactory area of the brain
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Unipolar
A single process that extends from the cell body, dendrite, and axon are fused, found in the peripheral nervous system.
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Sensory Neurons
Sensory receptors receive stimuli from a nerve impulse. Sensory neurons transmit impulses from sensory receptors to the CNS
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INterneurons (relay neurons)
Carry impulses within the CNs and act as a link between the sensory and motor neurons
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Motor Neurons
transmit information from the CNs to effectors. Effectors include muscles, glands, and other organs that respond to impulses from motor neurons.
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The Reflex Arc
Some neurons are organized to enable your body to react rapidily in times of danger, even before you are consciously aware of the threat. Sudden, involuntary responses to certain stimuli are called reflexes. A reflex arc is a simple connection of neurons that results in an involuntary reflex action in response to a stimulus.
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Nerve impulses
neurons use electrical signals to communicate with other neurons, muscles and glands. The signals called nerve impulses, involve changes in the amount of electric charge across a cells plasma membrane.
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Resting Neuron
the cytoplasmic side of the membrane (inside the cell) is negative relative to the extracellular side (outside of the cell). This charge separation across the membrane is a form of potential energy called membrane potential.
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Resting membrane Potential
potential difference across a membrane in a resting neuron (about -70mV) It provides energy for generating a nerve impulse.
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Three Factors responsible for establishing resting potential are
1. The Na+-K+ pump, is the most important factor that contributes to the resting membrane potential. This system uses ATP to transport 3 sodium ions (Na) out of the cell adn 2 potassium ions (K) into the cell. The overall result of this process is a constant membrane potential of -70mV.
2. Potassium Channels are more leaky than sodium channels - some of the potassium ions ythat were pumped in are allowed to leak out (down their concentraition gradient), but not many sodium ions can enter.
3. Large negative charge inside the cell
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Polarization vs Depolarization
A neuron is polarized due to the charge difference across the membrane.
Depolarization occurs when the cells become less polarized (the membrane is reduced to less than the resting membrane potential of -mV)
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Action potential
us the movement of an electrical impulse along the plasma membrane of an axon.
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All or Non Phenomenon
if a stimulus causes the axon to depolarize to a certain level (the threshold potential) an action potential occurs. Threshold potentials are usually close to -50mV.
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What happens during action potential
1. An action potential is triggered when the threshold potential is reached. Voltage-gated sodium (Na) channels open when the threshold potential is reached.
2. sodium ions move down their concentration gradient and rush into the axon, causing depolarization of the membrane. The membrane potential difference to -90mV.
3. Voltage-gated sodium channels close to +40mV and voltage-gated potassium (K) channels open. Potassium ions move down their concentration gradient and the axon, causing the membrane to be hyperpolarization.
4. Voltage-gated potassium channels close. The sodium-potassium pump and naturally occurring diffusion restore the resting membrane potential of -70mV. The membrane is now repolarized.
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After a potential occurs
the membrane cannot be stimulated to undergo another action potential. This brief period of time (usually a few milliseconds) is called the refractory period of the membrane,
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Nords of Ranvier
Neurons that are myelinated have exposed areas on their axons
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Nerve impulse consists of a series of action potentials
Conduction of a nerve impulse along a myelinated neuron is called saltary conduction because action potentials "jump" from one node of Ranvier to the next.
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How much faster is saltatory conduction than nerve impulses
Saltatory conduction (120 m/s) than the conduction of nerve impulses in unmyelinated neurons (0.5m/s)
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Synapse
The junction between two neurons, or between a neuron and an effector.
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Synaptic Cleft
Neurons are not directly connected but have a small gap between them
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Neurotransmitters
Chemical messengers called neurotransmitters carry the nerve impulse across the synapse from one neuron to another, or from a neuron to an effector
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Synaptic Vesicles
containing neurotransmitters move toward and fuse with the presynaptic membrane. Release neurotransmitters into the synaptic cleft by exocytosis. Neurotransmitters diffuse across the synapse to reach the postsynaptic neuron or the cell membrane of an effector
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Neurotransmitters bind
to specific receptor proteins on the postsynaptic membrane. The receptor proteins can trigger ion channels to open. If depolarization of the postsynaptic membrane occurs, and the threshold is reached, then an action potential is initiated.
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CNS
Structural and functional center for the entire nervous system. The site of neural integration and processing.
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What does the CNS do
Receives sensory information, evaluates information, and initiates outgoing responses.
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Myelinated neurons form
white matter, which forms in the inner region of some areas of the brain and the outer area of the spinal cord
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Unmyelinated neurons form
grey matter, which is found around the outside areas of the brain and forms the H-shaped core of the spinal cord
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Spinal Cord
The spinal cord is a column of nerve tissue that extends out of the skull from the brain and down through within the backbone.
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Sensory and Motor
Sensory (body to the brain) and motor (brain to the effector)nerves are found within the spinal cord. It is also the primary reflex center. The tissues are protected by cerebrospinal fluid, soft layer tissues, and the spinal column (vertebrae). Injury to the spinal cord can result in paralysis.
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The Brain
is a complex centre that maintains homeostasis. It is protected by the skull and the meninges (composed of three layers of tough, elastic connective tissue)
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Three regions in the brain
Hindbrain (coordination and homeostasis), Midbrain (processing sensory input), Forebrain (thought, learning, emotion)
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Blood-brain barrier
formed by glial cells and blood vessels. It separates the blood from the CNS and selectively controls the entrance of substances into the brain from the blood.
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What does the brain requires
a constant supply of oxygen and glucose. Both of these substances can cross the blood-brain barrier through special transport mechanisms.
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Lipid-soluble substances
(eg. caffeine, nicotine, alcohol) have rapid effects on brain function because they can pass directly through the barrier.
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Cerebellum "little brain"
Located in the hindbrain, walnut shaped structure involved in unconscious coordination of posture, refleces, body movemenet and fine volunrary motor skills. Recieves sensory infromation from proprioceptors, located in koints and skeletal muscles; from balance receptros in teh inner ear; and from receptors of touch, vision and hearing
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Medulla Oblongata
located in the hindbrian. Connect the briana nd spinal cord at the base of the brainstem; coordinates many reflexes ans automatic bodily functions that maintain homeostasis, including heart rate, constriction and dilation of blood vessels, coughing and rate and depth of breathing
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Pons
Located in hindbrain, mass of fibres in the brainstem; relay centre between right and left halves of the cerebrum and cerebellum
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Midbrain
found above the pons; process sensory ionformatoin from the eyes, ears and noses. It relays visual and auditory information between hindbrain and forebrain; controls skeletal muscle movement and plays an important role in eye movement.
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Thalamus
Located in the forebrain, "the great relay station" at the base of the forebrain; provides connections between teh forebrain and the hindb rain; receives sensory information and relays it to the appropriate region of the cerebrum.
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Hypothalamus
Forebrain, regulates the bodys internal environment, behaviour, bkiid oressure, heart rate, body temperature, n=hunger, thirst/hunger, and emotions (fear, rage, pleasure) and connects the nervous system to teh endocrine system (connected tot eh pituitary gland)
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Cerebrum
forebrain; largest part of the brain, divided into right and left cerebral hemispheres which each contain centres for intellect, learning, memory, consciousness, and language - interprets and control responses tp semsory information
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Cerebral cortex
each half of the cerebrum contains a mass of white matter and a thin, outer covering of grey matter
responseable for language, memory, personality, vision, conscious, thought and emotion
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Corpus callosum
right and left halves of the cerebral hemispheres are linked with
sends messages from one hemisphere to another
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Right brain
associated with holistic and intuitive thinking, visual-spartial skills, and artistic abilities
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Left Brain
associated with sequential and logical ways of thinking and linguistic/mathematical skills
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Frontal lobes
integrate information and control critical thinking, memory, personality, and precise fine motor skills. Each side of the frontal loves controls muscles on the opposite side of the body
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Parietal Lobes
Recieves and process sensory information from teh skin. Processes information about body position and orientation
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Occipital Lobes
receives and analyzes visual information
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Temporal Lobes
Share some visual processing but mainly process auditory information. Important in understanding speech and retrieving visual and verbal memories.
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The somatic system
Controls the voluntary movement of skeletal muscles. Its neurons service the head, trunk and limbs. The spinal nerves are named for the region of the body where they are located: cervical, thoracic, lumvar, and sacral. Includes 12 pairs of cranial nerves and 31 pairs of spinal nerves, all of which are myelinated. Each spinal nerve contains both sensory and motor neurons
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The autonomic nervous system
Controls involuntary glandular and the functions of smooth and cardiac muscle. it maintains homeostasis by adjusting the body to variations in the external and internal environments without an individual having to think about it. The autonomic nervous system is controlled by the hypothalamus and the medulla oblongata. It is further divided into teh sympathetic and parasympathetic systems
82
The sympathetic nervous system
activated in stressful situations and is often referred to as the fight-or-flight response. release epinephrine and norepinephrine which are excitatroy neurotransmitters that activate the stress response (increased heart rate, increased blood pressure, and decreased digestion)
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Parasympathetic Nervous System
It is activated when the body is calm and at rest. Conserve energy, referred to as the "rest-and-digest" response. Uses the neurotransmitter acetylcholine to control responses
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Hormones
1. produced by an endocrine gland and secreted into the bloodstream (travel to targeted areas).
2. Exert their effects on a part of the body far away from the cell secreting it
3. Required in very small amounts
4. act upon specific target cells that have the appropriate receptor proteins
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Three chemicals classes of hormones
1. Polypeptides (proteins - insulin, and peptides)
2. Amine hormones derived from amino acids
3. Steriod hormones
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Lipid soluble hormones
steroid hormones - pass easily through cell membranes. Diffuse across cell membranes travel in bloodstream bound to transport proteins, diffuse through the membrane of target cells
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water-soluble hormones
while water soluble hormones (polypeptides and amines) do not
secreted by exocytosis, travel freely in the bloodstream, bind to cell-surface receptors
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Pathway of water soluble hormones
Can't diffuse across the cell, binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm enzyme activation, or a change in gene expression
eg. epinephrine - once hormones is delievered, the hormone is inactive
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Pathway of lipid soluble hormones
takes time, response to a lipid-soluble hormone is usually a change in gene expression. Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus. Protein receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes
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Multiple effects of hormones
same hormone may have different effects on target cells that have
- different receptors for the hormones
- different signal transduction pathways
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Signaling by Local Regulators
-local regulators are secreted molecules that link neighboring cells or directly regulate the secreting cells
Types of local regulators
- cytokines and growth factors
-nitric oxide
- prostaglandins
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Negative Feedback Loop (hormones)
Inhibits the actions of the inital stimulus, thus preventing excessive pathway activity (counteracts the stimulus) Example thermoregulation and blood sugar regulation
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Positive Feeback Loop (hormones)
Reinforces response to stimulus to produce on even greater response (increases stimulus) Example in mammals oxytocin causes the release of milk, causing greater suckling by offspring, which stimulates the release of more oxytocin
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Hormones produced (direct)
hormone directly stimulates a part of the body, usch as muscle and bone growth, and milk production (blood glucose levels)
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Hormones produced (tropic)
hormone that regulates hormone production of other glands in the body such as the adrenal cortex, thyropid gland and gonads
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What part of the brain regulates hormone production
Hypothalamus
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Pituitary Gland
often called the master gland is located just below the hypothalamus that releases temperature, adn sleep cycles.
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Posterior Pituitary
collection of nervous tissue and is essentially an extension of the hypothalamus. Does not produce hormones itself, instead it acts more as a storage and release site for two hormones produced by the hypothalamus
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Two hormones produced by the hypothalamus
ADH - stimulates the kidneys to retain water
Oxytocin - involved in uterine contractions
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Anterior Pituitary
connected to the hypothalamus by the hypophyseal portal vessels, a ca[illary located in the pituitary stalk, which transport hormones from the hypothalamus to the pituitary gland. Secretes 6 major hormones. Hypothalamus controls the secretions of the anterior pituitary using releasing hormones to stimulate or inhibit pituitary secretions
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anterior pituitary controls secretions of the
thyroid, adrenal cortex, mammary glands, ovaries and testies
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Human Growth Hormone
The anterior pituitary gland is able to regulate the growth, development, and metabolism through the production and secretion of hGH. Affects almost every body tissue by direct stimulation or via tropic effects (stimulates the liver to secrete hGH)
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growth factors from the liver and hGH increase which processes
- protein synthesis
- cell division and growth
- metabolic breakdown and release of fats in adipose tissue
-human growth hormone stimulates the growth of muscles, connective tissue, and the growth plates at the end of long bones
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Gigantism
caused by excess amounts of hGH from the pituitary during childhood
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Acromegaly
caused by excess amounts og hGH from the pituitary during adulthood
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Pituitary dwarfism
caused by insufficient hGH production in childhood
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Prolactin
produced in the anterior pituitary gland
Function to aid in milk production
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oxytocin
produced by the hypothalamus and stored in the posterior pituitary
Function to help with breast feeding and uterus contractions during labour
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What happens to your body when you experience stress?
The endocrine system helps you cope with stressful situations. THe stress response involves many interating hormone pathways, including those that regulate metabolism, heart rate and breathing.
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Adernal Glands
pair of organs involved in regulating the stress responserenal glands are composed of two, and adre and blood sugar levels. Each ad layers: adrenal medulla - innernal cortex - outer
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Adrenal medulla
regulating the short-term stress response
adrenal medulla secretes two hormones :
- epinephrine (adrenalin)
- norepinephrine (noradrenalin)
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Epinephrine and Norepinephrine
- trigger glucose and fattu acid release into blood
- increase oxygen delievering to blood cells
- direct blood flow towards heart, brain, and skeletal muscles and away from skin, digestive system and kidneys
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Adrenal Cortex
produces stress hormones that trigger the long-term stress response.
Hormones include -
- Gpucorticoides - increase blood sugar, metabolism and supress immune function
- Mineralocorticoids - affect salt and water balance and increase blood pressure
- Gonadocorticoids - supplement sex hormones produced by gonads
114
Cortisol
Regulars lopng term stress response. In response to a stressor the following events occur in the long-term stress response:
- the hypothalamus secretes a releasing hormone, which stimulates the anterior pituitary gland to secrete adrenocorticotiopic hormone.
- ACTH targets the adrenal cortex, which causes the secretion of cortisol.
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What does cortisol promote
The breakdown of fats and muscle increases blood glucose levels. Also an anti-inflammatory. Cortisol levels are controlled in a negative feedback loop. However, chronic high levels can impair thinking, damage the heart, and cause early death.
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Aldosterone
Main mineralocorticioid is aldosterone. It smiulate kidneys to increase absoprtion of sodium in blood, which raises blood pressure . (water follows sodium osmosis)
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Throid Gland
located below the larynx and requires iodine to produce hormones. Are also classified as lipid-soluble. Enters cells goes to the nucleus, changes gene expression to increase metabolic rate.
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What hormones are produced by the thyroid gland
Produces three hormones
- thyroxine (follicular cells)
- triiodothyronine (follicular cells)
- calcitonin (parafollicular cells)
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Action of thyroid hormones
impacts your metabolic rate
thyroid hormones increase the rate of metabolism of fats, proteins, and carbohydrates, and assists in growth and development in the targeted cells. A downside to this activity is an increase in body heat.
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Lipid metabolism
fat breakdown for energy
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Carbohydrate Metabolism
increase carb utilization to generate energy
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Cadiovascular system affect
increased heart rate, more oxygen flow to organs there needs more oxygen
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CNS
decreased levels makes the individual sluggish. Increased levels induce anxiety and nervousness
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reproductive system
decreased levels have been connected to infertility
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Hypothyroidism
produces low levels of thyroid hormones.
Example 1 - Hashimotos disease (autoimmune disorder where the body's immune system attacks the thyroid. thyroid is damaged and cannot produce enough hormones)
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Effects / Symptoms of hypothyroidism
- swelling of the thyroid
- lethargy
- thinning hair
- weight gain
- stiff muscles
- difficulty tolerating cold weather
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Hyperthyroidism
When thyroid produces too much thyroid hormones
Example Graves disease
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Symptoms of hyperthyroidism
- warm temperature
- fast metabolism
- weight loss
- palpitations
- increase appetite
- bulging eyes
- swelling of thyroid
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Goiter
thyroid becomes larger. Happens both hypothyroidism and hyperthyroidism.
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Calcitonin
Removes calcium from the blood by increasing the uptake of calcium by the bones. calcium is a vital mineral in the body that facilitats nerve conduction, muscle contraction and skeletal development
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Parathyroid Glands
responsible for calcium homeostasis. Monitor, regulate and control calcium. controls the segretion of parathyroid hormone (pTH)
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Calcium allows for
conduction - of electrical currents along nerves
muscle contraction - the primary element
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Negative feedback loop for calcium (parathyroid gland)
ca level falls, parathyroid glands release PTH, bones release ca and blood ca level rises. (kidneys can also cue for reabsorption)
