Module 2, Week 2 (week 5) Flashcards
What is homeostasis?
Balance/equilibrium on the inside of the body, maintenance of body systems within a limited range associated with health.
List 3 x functions regulated by homeostasis mechanisms?
Blood volume
Temperature regulation
Rate of breathing
List 3 x common endocrine disorders:
Hyper/hypothyroidism
Addisons Disease
Polycystic ovary syndrome
Which 4 x body fluids are cavity dependent?
Blood plasma - in blood vessels
Synovial fluid - in joints
Cerebrospinal fluid - spinal cord
Aqueous humour/vitreous body - eyes
What is the interstitial fluid referred to?
The body’s internal environment.
LIst 4 factors that can interrupt homeostasis over longer periods:
Illness/chronic infections
Surgery
Poisoning
Extreme temperatures
Which two body systems are involved in homeostasis?
The nervous system
The endocrine system
What is the endocrine system’s main way of communication with body organs?
Hormones
Are hormones a fast or slower method of communication?
Slower - much slower than nerve impulses
How do hormones move around the body?
In the blood
List the 5 x steps in the feedback system:
- Observation - how are body systems are functioning (sensory neurons)
- Analysis - are modifications required? (control centre)
3 Adjustment - Apply modifications (effector cells - muscles/glands/organs) - More observation - how is system responding to modifications? (sensory neurons)
- More analysis - are further modifications required (control centre)
What are the three steps that repeat themselves with the feedback system?
Observation
Analysis
Adjustment
or
Monitored
Evaluated
Changed
What is the meaning of the term ‘controlled condition”?
The controlled condition is the range of function within certain limits - the limits that are connected to maintaining good health and are the boundaries that the body’s negative feedback systems maintain.
In regards to the negative feedback system, what is a stimulus?
Anything that causes an internal change and may shift the balance in body systems
List the three main roles/parts of the feedback loop:
Receptor (sensory neuron/receptor) Control centre (brain) Effector (muscle/gland/organ that responds to output from brain - makes the changes required)
What does afferent mean?
Refers to the sensory nervous system and relates to information that is carried towards the CNS - input from receptors/nerves to brain.
What does efferent mean?
Efferent is output, information or directive sent from the CNS to the effector cells - skin cells, muscles, glands etc
What is the afferent pathway?
The communication from nerve endings to the CNS ‘to the brain’
What is the efferent pathway?
The communication from the brain to effector cells ‘from the brain’
Describe a receptor in the feedback system:
- The nerve ending in sensory neuron - notices changes in internal conditions
- Sends information of change to CNS
- The message is sent in the form of nerve impulses or chemical signals
- Message/signals are referred to as input
- Example - skin receptors - detect change in external temperature of air/water on skin - body responds - sweating/shivering
In the feedback system, what is the control centre and what does it do?
- The brain is the control centre
- Brain establishes range of acceptable limits for certain conditions - set point
- Brain evaluates input and compares to established set points to determine whether adjustments are needed
- Brain sends signals/directions of adjustments req to effectors (muscles/glands etc) = output
In the feedback system, what is an effector?
An effector is any cell/tissue/organ that responds to messages/adjustments (output) from brain required to maintain homeostasis (setpoint) in a body system. It enacts the changes/modifications required.
Example: temperature drops. Body detects temp change - feels cold. Brain sends signals for muscles to shiver, generating heat, raising body temp.
List the stages of the feedback system (circular - from diagram)
Controlled condition - observed
Receptor - sends input to control centre
Control centre - receives info/analyses it/sends response info to effectors
Effectors - puts changes into effect
Response occurs
Return to homeostasis - brings conditions back into acceptable range/setpoint
What is the aim of the negative feedback system?
Reverse changes instigated by stimulus that upsets ideal conditions/setpoint - bring body system (controlled condition) back to setpoint/homeostasis.
Give an example of negative feedback:
Increased blood pressure - baroreceptors detect change - relay info to brain. Brain directs message to heart/blood vessels to modify action - dilate blood vessels/reduce heart rate. Heart responds by reducing heat rate, blood vessels dilate. Blood pressure normalised.
What is a positive feedback system?
Reinforces change instigated by stimulus. Example, continuation/intensification of birth contractions until baby is born. Example, blood loss - causes blood pressure to reduce - as blood loss continues, blood pressure further reduced. Can get dangerously low.
List 3 factors involved in having a healthy body:
- Lifestyle choices
- Genetic blueprint
- Environment - air quality, water quality
What is the cause of some diseases?
Repetition of behaviours/lifestyle choices over time - smoking, diet, alcohol consumption, stress levels, exercise levels
What is a disorder?
Big changes in the structure or function of an organ/body system - internal
What is disease?
Set of signs, symptoms - that characterise specific conditions/diseases
Where is the issue of a local disease located?
One area of the body
Where is the issue noticed in systemic disease?
Many parts of body or entire body system affected
What are symptoms?
Sensations that are not observable/measurable - headache, anxiety, nausea
What are signs?
Physical responses that can be seen and measured - body temperature, swelling, rashes, inflammation etc
What is epidemiology?
Looking at diseases and how they are transmitted in individuals and communities
What is pharmacology?
The scientific study of drugs and their effects on diseases
What is a diagnosis?
Drawing conclusions/labeling diseases by observing signs and symptoms, considering medical/family history, considering lab results, physically checking the body.
Why is the interstitial fluid so important to the body and homeostasis?
Cell function is dramatically influenced by the interstitial fluid. Its volume and composition (ions) greatly impacts the cell. Compromised cell function = unwell body.
What are hormones known as?
Mediators
LIst 9 x endocrine glands:
Hypothalamus (master gland) Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pancreas Testes Ovaries Pineal glands
List 8 functions of hormones:
Regulate/control: Volume/make-up of interstitial fluid metabolism/energy in v's energy out involuntary muscle contraction glandular secretions (hormones) immune responses growth & development reproductive processes circadian rhythms
Where does hormone pathway begin?
In the interstitial fluid
What is the hormone pathway?
Interstitial fluid-blood stream-target cells
What is the response time for hormones?
Differs. Some seconds. Some minutes. Some hours to days.
Do effects last longer than nervous system?
Yes
How do endocrine glands compare with exocrine glands?
Exocrine glands release substances into ducts - which transport substances around body: sweat, sebaceous, mucous, digestive substances
Endocrine glands release substances into interstitial fluid-blood stream-to target cells. Interdependent on bloodstream/cardiovascular system. Blood levels of hormone low - only a small amount required - potent.
Name other organs that act as endocrine glands, in that they secrete hormones:
kidneys thymus stomach liver intestines skin heart adipose tissue placenta
How do hormones get to target cells from the bloodstream?
Diffuse through the interstitial fluid to target cell membrane
Name the two major types of hormones:
Water-soluble
Lipid soluble
Describe water-soluble hormones:
Dissolve in water
Circulate on their own in the blood
Diffuse from endocrine gland-interstitial fluid-bloodstream-interstitial fluid-target cell
Bind to cell receptor in cell membrane
Called the first messenger
Second messenger (cAMP) is a chemical inside the cell that is triggered by hormone and illicit desired response on cell - set of biological actions within the cell.
Example: insulin
With water-soluble hormones, what is the final response of the cell?
The function of the cell is altered due the protein function changing. This generates a physical change in the body.
How do lipid-soluble hormones travel from endocrine gland to target cell & how do they impact the target cell?
Do not dissolve in water
Cannot travel freely
Need to be transported by protein transporters in blood
When near target cells, hormone detaches from transporter and diffuses through interstitial fluid.
Lipid-soluble so can diffuse through cell membrane
Receptors often in nucleus or cytosol
Hormones affect gene expression/synthesis of proteins (enzymes)
Causes copy of RNA. New protein created. New protein changes cell behaviour
Example: testosterone
How many receptors do target cells have?
2000-10000
In regards to hormone receptors, downregulation is:
Reduction of hormone specific receptors in target cells, if there is too much hormone circulating - ensures hormone doesn’t impact too heavily
In regards to hormone receptors, upregulation is:
Increase of hormone specific receptors in target cells, if there’s low levels of hormone circulating - ensures enough hormone is accessed to get the right response - homeostasis.
What are paracrines?
Hormones that act locally - close to release
What are autocrines?
Act on cells that release the hormone
How long does the impact of a local hormone last?
Not long
Example of local (paracrine) hormones are:
Interleukin-2 - Secreted by T Cells - acts locally. Causes increase in generation of T cells, which increases secretion of interleukin-2 = boost in capacity of immune response
Example of autocrine hormone:
Interleukin-2 again - also acts on its own cells
What organ inactivates circulating hormones?
Liver inactivates circulating hormones. Excess hormones excreted through kidneys
Examples of lipid-soluble hormones:
steroid hormones - testosterone, oestrogen, progesterone, aldosterone, calcitriol
thyroid hormones - thyroxine (T4), triiodothyronine (T3)
gas, nitric oxide (NO)
Examples of water-soluble hormones:
amine hormones (amino acids less Co2) peptide hormones eicosanoid hormones (prostaglandins & leukotrienes)
epinephrine, norepinephrine (catecholamines), melatonin, histamine, seratonin
List 3 ways the interaction of receptors and hormones can be impacted:
- the amount of hormone in the blood
- the number of receptors in the target cell
- the effect of other circulating hormones (some hormones need other hormones to get maximum impact - a hormone could permit/approve the action of another hormone)
How can secondary hormone increase the effects of the primary hormone?
- increase the number of receptors in the cell membrane of the target cell
- assist with access to enzyme that enhances primary hormone function
What’s the synergising effect?
When the outcome of two complementary hormones is greater than the effect of each hormone on their own.
What’s the antagonistic effect?
When one hormone provides the opposite effect of another - counteractive - insulin builds glycogen in liver - glucagon breaks glycogen in liver
How do hormones warn cells about their pending action?
They bind to their receptors - it’s the heads up
List 4 examples of second messengers in water-soluble hormone action:
Cyclic AMP (cAMP)
Neurotransmitters
Neuropeptides
Sensory transduction mechanisms
What’s another name for the pituitary gland?
The hypophysis
Where are hypothalamic hormones produced?
In the hypothalamus
How do hypothalamic hormones reach the anterior pituitary?
Travel down axons of hypothalamus to hypothyseal portal veins. Travel to anterior pituitary through hypophyseal portal veins.
Name two types of hormones released by the hypothalamus:
releasing hormones
inhibiting hormones
List 7 hormones released by the anterior pituitary:
- Growth hormone
- Thyroid-stimulating hormone (TSH)
- Follicle-stimulating hormone (FSH)
- Luteinising hormone (LH)
- Prolactin
- Adrenocorticotropic hormone
- Melanocyte-stimulating hormone
Describe how where the posterior pituitary hormones are synthesized, how they are transported and released:
Pituitary hormones are produced in the hypothalamus and travel to the pituitary via the axons in hypothalamus neurons.
Hormones are stored in the posterior pituitary until required. Action Potentials trigger the release of hormones from PP - released into blood stream - reach target cells
Name the two hormones stored and released by the posterior pituitary:
Oxytocin
Antidiuretic hormone
Areas affected by endocrine hormones:
Growth/development
Metabolism
Homeostasis
Reproduction
What’s the main tissue type of the posterior pituitary?
Neural tissue
What’s the main tissue type of the anterior pituitary?
Glandular
How does the hypothalamus impact both the endocrine system and the nervous system?
It links them - influencing both systems
Name the 5 x types of hormones secreted from the anterior pituitary:
- somatotrophs - hGH = human growth hormone / insuln-like growth factors (IGF)
- Thyrotrophs - TSH
- Gonadotrophs - FSH, LH - act on gonads
- Lacotrophs - prolactin (lactation)
Coricotrophs - adrenocorticotropic hormone (ACTH) & melanocyte-stimulating hormone
What is the main function of the thyroid hormones?
Regulating metabolism - sets the basal metabolic rate
Heat production - higher the metabolic rate, the more heat produced
Tissue growth regulation
Rate of heart and impacts blood pressure
Where is thyroid hormone produced?
Thyroid follicles - part of thyroid tissue
Production of thyroid hormones require a substance/molecule from food. What is this molecule?
Iodide (iodine)
What does do thyroid hormones set with the basal metabolic rate?
How quickly oxygen is consumed and energy is used at rest.
Explain the negative feedback loop for thyroid hormones:
- low T3 & T4 levels detected in blood
- Hypothalamus releases thyrotropin-releasing hormone (TRH) to anterior pituitary gland
- Anterior pituitary gland releases thyroid-stimulating hormone
- Thyroid follicles are triggered by TSH and release T3 & T4 hormones into the bloodstream
- Increase of T3 & T4 noticed in bloodstream. This triggers the halt of both TSH in anterior pituitary and thyrotropin-releasing hormone (TRH) in hypothalamus. L
What is hyperthyroidism?
When the thyroid gland is overactive, producing/releasing too much thyroid hormones
What is a disease that causes hyperthyroidism?
Graves disease - an autoimmune disease.
Antibodies same shape as TSH, so bind with TSH receptors, triggering the release of TSH.
Antibodies are not controlled by negative feedback loops, so continue to stimulate the release of TSH - too much T3 & T4 released. Causes awful symptoms including bulging eyes.
What are the symptoms of hyperthyroidism?
Increased basal metabolic rate - increases appetite, but also weight loss - can’t match food intake/energy use.
Increased catabolism of carbs, fats, proteins - leads to muscle breakdown/loss of muscular strength
Increase heat production - people sweat a lot and become intolerant to heat
Increased anxiety, grumpy behaviours
Increased heart rate - palpitations
What is hypothyroidism?
When not enough thyroid hormones are produced
What happens with hypothyroidism:
Thyroid gland cannot function properly
Reduced thyrotropin-releasing hormone from hypothalamus
Reduced TSH from anterior pituitary
Low iodine consumption in diet
Symptom can be the development of goiter - an enlarged thyroid gland
What is the name of the disorder relating to hypothyroidism present from birth and what are the effects on the infant?
Cretinism
Brain doesn’t develop properly - may not be able to be rectified
List the symptoms of hypothyroidism:
Reduction in basal metabolic rate - reduces appetite, however, metabolic rate is so low, weight gain occurs easily.
Reduction in the rate that carbs, fats and protein are broken down which means people feel tired - their energy is low.
Reduction in generation of heat - temperature drops - hard to bare cooler temperatures - more sensitive to cold
Reduction in mental alertness - responses are slower, memory compromised, reflexes slower, speech retarded
Cardiovascular system affected - heart rate reduced, weaker heart strength
Are there generally higher T3 or T4 levels in the blood?
T4
Is T3 more potent than T4?
Yes, T3 is more potent than T4
In cells, are they more likely to use T3 or T4?
T3 - by removing 1 x iodine atom
Which protein transporter transports thyroid hormones?
Thyroxine-binding globulin (TBG)
How do thyroid hormones affect sodium/potassium pumps?
Thyroid hormones are involved in triggering the production of sodium/potassium pumps. These pumps use ATP for energy, the byproduct being heat. This is the link between thyroid hormones and heat/temperature regulation.
Which other hormones does the thyroid hormones enhance?
norepinephrine and epinephrine. They do this by upregulating the receptors they bind to (beta B receptors), which impacts the heart rate and increased strength of heartbeats and blood pressure.
In the thyroid follicles there are a special type of cells that are adjacent to follicle cells, parafollicular cells. What do they secrete?
They secrete calcitonin, a hormone that works to reduce blood calcium levels, allowing the bone to absorb more, and reducing the breakdown of calcium in the bones to supply the bloodstream.
