Anatomy + Physiology Flashcards
What are the 5 key functional features of respiratory system?
- Extensive gas exchange surface area between air and circulating blood
- Moves air to and from exchange surfaces of lungs
- Protects respiratory surfaces from outside environment
- Produces sound
- Participates in olfactory sense
What are the 2 portions of the respiratory tract?
Carry air to and from exchange surfaces in lungs
Has both a…
- conducting portion (nasal cavity -> terminal bronchioles)
- respiratory portion (respiratory bronchioles + alveoli)
Describe the structure of lungs as a whole
Lungs are a network of branched passageways (branch 23 times)
- bronchioles have a irregular dichotomous pattern
- Each airway gives rise to 2 daughter airways
- alveoli surrounded by a dense network of capillaries
- alveoli appear as buds in bronchiole wall from branch 17
- from 20 onwards, whole airway is alveoli
What does the respiratory mucosa consist of, what’s its role?
It consists of an epithelial layer and an areolar layer
- lines conducting portion of respiratory system
- underlined by lamina propria
- in upper respiratory system there are mucous glands
- in conducting portion of lower respiratory system = smooth muscle that allows for dilation of terminal bronchioles
List all of the parts involved in the process of breathing?
- nasal cavity
- palates
- Pharynx
- glottis
- larynx
- trachea
- bronchi + bronchioles
- alveoli
Step 1 of respiratory pathway…
What occurs at the nasal cavity?
- Air enters through nostrils / external nares into nasal vestibule
- Nasal hairs in vestibule assist in 1st part of filtration system
- Air flows through 3 nasal meatuses which humidifies air + filters
Step 2 of respiratory pathway…
What are the 2 parts of palates + role?
Hard palate = forms floor of nasal cavity, separating nasal + oral cavities
Soft palate = extends posterior to hard palate, dividing superior nasopharynx from lower pharynx
Step 3 of respiratory pathway…
What is the pharynx, where is it located?
A chamber shared by digestive + respiratory systems
- extends from internal nares to entrances to larynx + oesophagus
3 divisions = nasopharynx, oropharynx, laryngopharynx
What surrounds the glottis?
The larynx - a cartilaginous structure
Step 4 of respiratory pathway…
What is the role of the glottis?
It’s where the voice box is found
- involved in sound production - formed via air passing through glottis
Step 5 of respiratory pathway…
Describe the trachea
It extends from bottom of larynx to part where it starts to branch off into lungs
- Tracheal cartilages give structure + support + flexibility
- Tracheal muscle allows contraction + pulling of C shaped cartilage at back of trachea to force expired air out
Step 6 of respiratory pathway…
Describe the parts of the bronchi + what’s significant about the 2 parts of bronchi?
Right and left primary bronchi - these are separated by an internal ridge (carina)
- right primary bronchus = larger in diameter + descends at a steeper angle
Each primary bronchus travels to a groove (Hilum) along medial surface of lung
Describe the bronchiole tree structure
Formed by primary bronchi + their branches
- primary bronchus branches to form secondary bronchi (lobar bronchi) in which 1 secondary bronchus goes to each lobe
- extrapulmonary + intrapulmonary bronchi = branching outside or inside lungs
Secondary bronchi branch to form tertiary (segmental) bronchi = each supplies air to a single bronchopulmonary segment
- 10 segments in right lung, 8/9 in left
What do the walls of bronchi contain?
- progressively less cartilage + more smooth muscle
- Increasing muscular effects on airway constriction + resistance
What do bronchioles not have and what are they dominated by?
Do not have cartilage
Dominated by smooth muscle
What is the role of the smooth muscle in bronchioles?
Autonomic control regulates smooth muscle, controlling the diameter of bronchioles, air flow and resistance on lungs
What are bronchodilation and bronchoconstriction?
Bronchodilation = widening of bronchiol airways, caused by sympathetic ANS activation
- reduces resistance
Bronchoconstriction = constriction of bronchi, caused by parasympathetic ANS activation
What are alveoli?
Air filled pockets in lungs
- all gas exchange occurs here
- thin membranes (short diffusion distance)
- Large surface area
What is external respiration - what processes does it include?
It includes all process involved in exchanging O2 + CO2 with the environment
- Pulmonary ventilation
- Gas diffusion
- Storage and transport of O2 + CO2
What is internal respiration also known as?
Cellular respiration
- involves the uptake of O2 and production of CO2 within individual cells
What is pulmonary ventilation?
The physical movement of air in and out of the respiratory tract
- provides alveoli ventilation = same as above just at alveoli
What is Boyles law?
It defines the relationship between gas pressure and volume
P = 1 / V
It is inversely related (as one increases, other decreases)
- e.g. as pressure decreases, volume increases etc
Relating to Boyle’s Law
In a contained gas…
External pressure forces molecules closer together
The movement of gas molecules exerts pressure on the container
Describe the compliance of the lungs
At rest, pressure of lungs = volume of lungs
- this is an indicator of expandability
Low compliance requires greater force, high compliance requires less force
When the rib cage is elevated or diaphragm is depressed during inhalation, what occurs in thoracic cavity regarding volume + pressure?
Volume increases and pressure decreases
Outline inspiration
- Initiated by respiratory control centre in medulla oblongata
- Activation of medulla = contraction of diaphragm + intercostals
- Diaphragm moves downwards + rotates lower ribs towards horizontal plane
- quiet breathing = 1cm
- force inhalation = 10cm - External intercostals also move ribs up + out, increasing thoracic cavity
Outline expiration
- In normal quiet breathing, expiration is a passive event
- Elastic fibres in connective tissues of lungs + surface tension of a film of fluid that coats the alveoli = elastic recoil
What muscles are involved during inspiration?
- Sternocleidomastoid
- scalenes
- external + internal intercostals
- diaphragm
What muscles are involved during expiration?
- internal intercostals
- external + internal abdominal oblique
- transverse + rectus abdominus
What is quiet breathing, what’s it also called?
Eupnea
- involves active inhalation + passive exhalation
- diaphragmatic breathing/ deep breathing = dominated by diaphragm
- costal breathing or shallow breathing = dominated by rib cage movements
What is forced breathing, what’s it also called?
Hyperpnea
- involves active inhalation + exhalation
- assisted by accessory muscles
- maximum levels occur in exhaustion
What’s the formula for volume of air moved each minute?
Breaths per minute x tidal volume
What’s the formula for alveolar ventilation?
Breaths per minute x (tidal volume - dead anatomical space)
What do the following refer to…
- FEV1
- FVC
- FEV1 = forced expiratory volume in 1 second
- FVC = forced vital capacity
- this is the maximum volume of gas that can be expelled from the lungs after maximum inspiration
What is the forced expiratory ratio?
FEV1 / FVC
What is the alveolus, what’s it surrounded by?
An extensive network of capillaries surrounded by elastic fibres
- this allows for the recoil during exhalation, reducing the size of alveoli to push air out of lungs
What are the 2 key adaptations of alveoli for gases to be exchanged efficiently?
- Alveoli walls must be very thin
- Surface area must be vast
Outline the alveolar epithelium - what it consists of, what they are patrolled by etc
- Consists of simple squamous epithelium also called Type I pneumocyte (thin, delicate)
- patrolled by alveolar macrophages (known as dust cells) = carry out phagocytosis of foreign objects
- also contain septal cells (type II pneumocytes) = produce surfactant
What is Henry’s law?
When gas under pressure comes into contact with liquid…
- gas dissolves in liquid until equilibrium is reached
At a given temperature…
- amount of gas in a solution is proportional to PP of that gas
What are the 5 key reasons for efficiency of gas exchange?
- Substantial differences in PP across respiratory membranes
- Distances involved in gas exchange are short
- O2 + CO2 are lipid soluble = rapid movement
- Large surface area
- Blood flow and airflow are coordinated
The blood arriving in pulmonary artery has…
In which the concentration gradient causes…
(Refer to partial pressures)
Low PO2 + High PCO2
O2 to enter and CO2 to leave blood
What is key about the systemic circuit regarding blood, what does this lead to?
Oxygenated blood mixes with deoxygenated blood from conducting passageways
- this lowers the PO2 of blood entering systemic circuit
What are the 3 key types of haemoglobin?
Oxyhaemoglobin
Deoxyhaemoglobin
Carbaminohaemoglobin
Describe the oxygen-haemoglobin saturation curve
- Higher PO2 results in a greater Hb saturation
- its a curve rather than a straight linear line because Hb changes shape each time a O2 molecule is bound
- each O2 bound makes the next O2 binding easier
- this allows Hb to bind O2 when O2 levels are low
Describe the relationship between temperature and Hb saturation
- when temperature increases, Hb releases more oxygen
- when temperature decreases, Hb holds oxygen more tightly
However temperature effects are only significant in active tissues that are generating large amounts of heat
Describe the relationship between pH + haemoglobin
Bohr effect is the result of pH on haemoglobin saturation curve
- CO2 diffuses in RBC
- an enzyme called carbonic anhydrase catalyses reaction with H2O
- produces carbonic acid = dissociates into hydrogen ion + bicarbonate ion
- hydrogen ions diffuse out of RBC, lowering pH
What effect does 2,3 biphosphoglycerate (BPG) have on Hb + O2 association
RBCs generate ATP by glycolysis = forms lactic acid + BPG
- BPG directly affects O2 binding and release (more BPG means more O2 is released from Hb)
When do BPG (biphosphoglycerate) levels rise?
What happens if BPG levels are too low?
- when pH increases
- when stimulated by certain hormones
If BPG levels are too low… haemoglobin will not release oxygen
What are the 3 pathways for carbon dioxide transport?
Are these reversible?
- Dissolve into plasma
- Bind to haemoglobin
- Converted to H2CO3 (carbonic acid)
- all of these are reversible
Describe the local control of respiration (AT TISSUES)
- increased activity of peripheral tissue
- decreased PO2 + increased PCO2
- changes in gas exchange
- increased blood flow
What is neural control of respiration?
When oxygen demand rises…cardiac output + respiratory rates rise under neural control
- both voluntary and involuntary components
Involuntary neural control of respiration
What does it regulate, what does it use?
It regulates respiratory muscle activity
- frequency + depth of inspiration
- responding to info from lungs + respiratory tract
- uses receptors = mechano, chemo, baroreceptors
Voluntary neural control of respiration
What does it regulate and affect?
It regulates activity in cerebral cortex
- affects output of respiratory centres (medulla oblongata + pons) + motor neuron’s
Describe the control of respiration in the PONS
What centres, what these do…
The apneustic and pneumotaxic centres of pons
- these are paired nuclei that adjust output of respiratory rhythmicity centers in medulla oblongata
- regulate respiratory rate + depth of respiration
Higher centres in hypothalamus, limbic system and cerebral cortex can alter activity of pneumotaxic centres
Describe the control of respiration by the MEDULLA OBLONGATA
The main role and the 2 types of groups
Main role is to establish basic pace and depth of respiration
- Dorsal respiratory group = inspiratory centre
- functions in quiet + forced breathing
- when active = diaphragm, external intercostal muscles contract = inhalation - Ventral respiratory group = inspiratory + expiratory group
- functions only in forced breathing
- when VRG expiratory centre is active (ONLY) = inhalation muscles relax and muscles of exhalation contract = Exhalation
What are the 5 key respiratory receptors?
Chemoreceptors
Baroreceptors
Stretch receptors
Irritating physical or chemical stimuli in nasal cavity, larynx or bronchial tree
Other sensations: pain, body temp, abnormal visceral sensations
RESPIRATORY REFLEXES
What are the 2 key mechanoreceptors + what do they do
Baroreceptors in aortic or carotid sinuses
- sensitive to changes in blood pressure
Stretch receptors
- respond to changes in lung volume / lung stretch
What is the Hering-Breuer reflex?
What are the 2 reflexes, what do they do?
2 mechanoreceptors involved in forced breathing (no eupnea or when Vt <1000ml)
- Inflation reflex = prevents over expansion of lungs
- as lung volume increases, DRG is inhibited and VRG is stimulated (expiratory portion) - Deflation reflex = inhibits expiratory centres
- stimulates inspiratory centres (DRG + portion of VRG) during lung deflation
RESPIRATORY REFLEXES
What do chemoreceptors respond to, where are the key locations?
They respond to changes in PCO2, PO2, pH or blood
Respiratory centres are strongly influenced by chemoreceptor input from…
1. Cranial nerve IX in carotid bodies - glossopharyngeal nerve to CNS
2. Cranial nerve X in aortic bodies - to medulla oblongata via vagus nerve
3. Central chemoreceptors that monitor cerebrospinal fluid
What do the following changes result in?
- A drop in PO2 to around 40mm Hg
- A rise of 10% in arterial PCO2
- Increase respiratory rates by 50-70%
- Increase respiratory rates by 100%
CHEMORECEPTOR STIMULATION
What does an increase in PCO2 lead to?
Stimulates chemoreceptors that accelerate breathing cycles at inspiratory centre
- this change increases the respiratory rate, encourages CO2 loss at lungs, and decreases arterial PCO2
CHEMORECEPTOR STIMULATION
What does a decrease in PCO2 lead to?
A decrease in arterial PCO2 inhibits chemoreceptors
- without stimulation, the rate of respiration decreases, slowing the rate of CO2 loss at the lungs and increasing arterial PCO2
Describing the effect of age on respiration
What is happening before birth?
Pulmonary vessels are collapsed
Lungs contain no air
Describing the effect of age on respiration
What happens at birth?
Newborn overcomes force of surface tension to inflate bronchial tree and alveoli to take first breath
Describing the effect of age on respiration
What occurs when you become more elderly?
Deterioration in elastic tissue - lower compliance and VC
Arthritic changes and decreased flexibility
Emphysema - from smoking (destruction of alveoli)
What are the components of the CV system?
Fluid medium
System of channels - blood vessels (vascular system)
Pump - heart
What are the functions of the CV system?
Transport of blood
Maintenance = vasodilation/constriction to maintain homeostasis (temperature etc)
Protection = white blood cells to fight off foreign molecules + dehydration response
How is the CV system divided?
2 parts…
- Pulmonary circuit = blood to and from lungs
- Systemic circuit = blood to and from rest of body
Describe the location of the heart using anatomical terms
Located in the thoracic cavity - near the anterior chest wall, directly posterior to sternum
- between 2 lungs
- apex of heart sits between 4th and 5th rib (called thoracic space)
- base of heart sits more centrally between 3rd + 4th rib
List the 4 key factors influencing the size of someone’s heart
- training/ exercise (thicker walls = hypertrophy)
- size of the person - determines size of pump needed
- aging - decrease in cardiac tissue + reduction in levels of activity (linked)
- sex
Outline the structure of the heart referring to the functions of the chambers
4 chambers functioning as a double pump
2 atria…
- right atrium receives blood from systemic circuit + passes it into right ventricle
- left atrium received blood from pulmonary circuit + passes it to left ventricle
2 ventricles…
- right ventricle receives blood from right atrium + pumps it into pulmonary circuit
- left ventricle received blood from left atrium + pumps it into systemic circuit
What are the values for volume of blood pumped from the heart…
- At rest
- During exercise
- Per day at rest
- 5 L/min
- 15-20 L/min
- 8000 L
What are the 3 tissues that make up the hearts wall?
Pericardium
Epicardium
Myocardium
What’s the pericardium made up of/ function of it?
- Fibrous tissue (collagen) - provides a physiological limit to expansion of heart
- Stabilises heart position - some attachment to diaphragm, great vessels + sternum
- Lubrication (pericardial fluid) - reduce friction + more efficient
What is the myocardium?
A thick muscular layer between epicardium + endocardium
- thickness varies according to function of chambers - left ventricle is thickest
What’s the structure of the myocardium?
Short and wide
Y-shaped + branched = each muscle cell is branching off + interacting with many other muscle cells
Large central nucleus and a large number of mitochondria - lots of O2 + nutrients
Involuntary due to auto-rhythmicity = myogenic
What is the role of intercalated discs?
The junction between cardiac cells made up of 2 components…
- Gap junctions = allow for depolarisation to pass between cells synchronising muscle contraction
- Desmosomes = bind adjacent myocytes together
What does the endocardium do + consist of?
- Covers all inner surfaces of the heart = internal chambers + heart valves
- consists of epithelial tissue and is continuous with epithelium of great vessels
Describe the differences between the 2 ventricles
Both ventricles hold the same amount of blood
- the wall of the LV is thick = cylindrical shape
- the wall of the RV is thin (comparatively) = pouch like shape
Why would a comparable pumping arrangement of the heart + ventricles not work?
- LV delivers blood into systemic circuit where mean pressure is 80-100 mmHg
- pumping blood around systemic circuit requires 4-6 times more pressure than pulmonary circuit
- RV delivers blood into pulmonary circuit where mean pressure is <15 mmHg
List the passageway of blood to the lungs and then to the rest of the body
- Vena cava -> right atrium -> tricuspid valve -> right ventricle -> pulmonary valve -> pulmonary artery
- Pulmonary vein -> left atrium -> bicuspid valve -> left ventricle -> aortic valve -> aorta
Outline what a heartbeat is
A single contraction of the heart
- the entire heart contracts in series - atria first, ventricles second
What are the 2 types of cardiac muscle cells?
- Contractile = produces contractions
- Cardiac pacemaker cells (nodal/ conducting) - SA node, AV node, Purkinje fibres
- These control and coordinate contractile cells
Give an overview of the cardiac cycle (SA node -> contraction)
- SA node depolarises + 2 atria contract
- SA node propagates around atria + arrives at AV node
- AV node has some auto-rhythmicity but depolarises more slowly than SA node
- Imparts a slight delay before reaching threshold + propagating around ventricles (allows blood to enter ventricles)
- Specialised fibres carry it around walls of ventricles (bundle of His + purkinje fibres)
Describe the 5 steps of the ECG Trace
- SA node activity + atria activation begin (60-100 action potentials per min at rest)
- Stimulus spreads across the atrial surfaces + reaches AV node
- There is a 100msec delay at AV node + atrial contraction begins
- Impulse travels along the inter-ventricular septum within the AV bundle and bundle branches to purkinje fibres and, by the moderator band, to the papillary muscles of right ventricles
- Impulse is distributed by purkinje fibres and relayed throughout the ventricular myocardium. Atrial contraction is completed + ventricular contraction begins
What are the 4 types of regulation of the heart rate?
- autonomic nervous system
- catecholamines
- changes in O2 / CO2 levels
- changes in blood pressure
HEART RATE REGULATION 1
What are the 2 main branches of the autonomic nervous system (ANS)? Where do these innervate?
Sympathetic nervous system = increases HR
- dominates at exercise + innervates directly at SA node
Parasympathetic nervous system (vagal) = slows HR
- dominates at rest + innervates directly at SA node
HEART RATE REGULATION 2
What are the 2 main types of catecholamines?
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
HEART RATE REGULATION 2
Where is epinephrine released from, what does it do and how?
It is released by adrenal medulla upon activation of sympathetic nerves innervating this tissue
- in response to exercise, stress, anxiety
It increases HR and contractility = positive inotropic response
- works by binding to adrenergic receptors on heart
HEART RATE REGULATION 2
Where is norepinephrine released from, what does it do and how?
It is released from adrenal medulla but mostly from spillover from sympathetic nerves innervation with blood vessels
Initially increases HR and contractility, but with longer exposure results in decreased HR
- binds to adrenergic receptors
HEART RATE REGULATION 3
What 2 things do chemoreceptors detect that causes…
- an increase in HR
- a decrease in HR
- High CO2 or low pH causes an increase in HR
- Low CO2 or high pH causes a decrease in HR
HEART RATE REGULATION 4 BARORECEPTORS
A low BP = …
Low BP = low stretch of vessels = less stretch of receptor = decreased afferent firing = increases efferent sympathetic firing + decrease parasympathetic firing
What are chordinae tendineae?
Tendonous strings that are attached to the 2 valves (attached to papillary muscles at the other end)
How do chordinae tendineae and papillary muscles work/ what do they do?
They tether these valves to the ventricular wall, so when the papillary muscles contract during ventricular systole, it pulls the chords tight to prevent the valves opening and allowing backwards blood flow
What are the 2 main systems of the CV system?
Arterial and Venous System
Describe the arterial system + components
A high pressure system delivering blood AWAY from the heart
- arteries + arterioles
What is the role of arteries and arterioles + describe structure?
Arteries = carry blood AWAY from heart
Arterioles = smallest branches of arteries that lead to capillary beds
- involved in BP regulation
- just endothelial cells surrounded by smooth muscle
- no elastin like others
What is the capillary bed comprised of?
Capillaries
Pre-capillary sphincters
Thoroughfare channels
Describe capillaries
Smallest blood vessels - thin walls = short DD
- location of exchange between blood vessels + interstitial fluid
Describe pre-capillary sphincters role
Constricts to control blood flow before entering lower pressure venous system
- ensures nothing ruptures under high pressure
Describe thoroughfare channels
A direct channel that link the arterial + venous system
- allows for continuous transition of blood between systems if there’s a blockage in bed
- same sort of role as arteriovenous anastomosis - rapid control of blood flow + temp regulation (bypass of capillary bed = collateral circulation)
List the components of the venous system
Veins and Venules
- skeletal muscle pump + venous valves additionally
Describe venules
Smallest branches of veins that collect blood from capillaries
- low pressure at this point
Describe veins
Returns blood to heart
- smooth muscle present is appropriate for allowing autonomic control over blood flow + pressure
- can vasoconstrict + assisted by skeletal muscle pump
Describe the skeletal muscle pump of the venous system
Skeletal muscle contracts
- valves open superior to contracting muscle
- valves close inferior to contracting muscle
What are venous valves + how do they work?
They are folds in the tunica intima that prevent blood from flowing backwards
- the compression of veins pushes blood towards the heart
- when the walls of veins near the valves weaken = varicose veins could result (enlarged + twisted)
Describe the common blood vessel structure
Have 3 layers = tunica intima, media and externa
- slightly different characteristics between blood vessels
- opening of blood vessel = lumen
- endothelium lines lumen
What is the tunica intima?
It encompasses the endothelial lining + connective tissue layer
- internal elastic membrane (within arteries only) providing passive elasticity to tunica intima
What is the role of the endothelium?
‘Non-stick’ role - releases vasoactive substances which affect vascular tone, BP and flow
- maintains vascular homeostasis
- vasodilators (nitric oxide) - beetroot juice as ergogenic aid (high in dietary nitrate)
- vasoconstrictors (endothelin)
What’s the role of the tunica media?
Contains concentric sheets of smooth muscle in loose connective tissue - elastic fibres in arteries, collagen in veins
- encircles endothelium that lines lumen
- binds to both inner + outer layers
- external elastic membrane (arteries only) - separates media + externa
What is the role of the tunica externa?
Anchors vessel to adjacent tissues
- contains collagen + elastic fibres, smooth muscle cells (in veins)
What is the vasa vasorum?
Small arteries and veins in walls of large arteries + veins
- they serve cells of tunica media + externa with nutrients, energy etc
What are the types of artery?
Elastic arteries
Muscular arteries
Arterioles
(Largest artery = aorta) - high elastic fibre content in tunica media
What do elastic arteries do + describe? Reservoir
Conducting arteries due to constant flow of blood under pressure
- serves as a pressure reservoir = takes pressure from contraction of heart and uses it
- very thin tunica externa
What is an example of a muscular artery - what’s different?
Femoral artery
- tunica media contains more smooth muscle + less elastin
Describe capillaries in more detail - types, what is has/ doesn’t have…
Consists of an endothelial tube, inside a thin basement membrane
- no tunica media or externa
- diameter is similar to that of a RBC
3 types = continuous, fenestrated, sinusoid
What are continuous capillaries - description, roles etc
Found in all tissues of the body (except epithelia + cartilage)
- complete endothelial lining
- permits the diffusion of water, small solutes + lipid-soluble materials (blocks RBC + plasma proteins)
Specialised continuous capillaries found in CNS + thymus = very restricted permeability
What are fenestrated capillaries - what’s different, found in?
Have pores in endothelial lining - permit rapid exchange of water + larger solutes
Found in…
- choroid plexus = produces cerebrospinal fluid
- endocrine organs
- intestinal tract
- kidneys
What are sinusoid capillaries - what they have, found in?
Have gaps between adjacent endothelial cells
- permit free exchange of water and large plasma proteins
- phagocyte cells monitor blood at sinusoids
Found in…
- liver, spleen, bone marrow, endocrine organs
What is total capillary blood flow?
It equals cardiac output (SV x HR)
- it is determined by pressure and resistance in the CV system
Describe what is meant by pressure of the CV system
Generated by the heart to overcome resistance
- absolute pressure is less important than pressure gradient
Pressure gradient = difference in pressure at 1 end of vessel compared to other end
What is meant by flow?
It is proportional to pressure gradient divided by resistance
What must circulatory pressure overcome?
Total periphery resistance
- pressure gradient across systemic circuit is about 85 mm Hg
What is total peripheral resistance affected by?
- Vascular resistance - due to friction between blood + vessel walls (as diameter decreases, resistance increases exponentially)
- Blood viscosity - harder to move through blood vessel
- Turbulence - increase by plaques (risk factors for CV) = resistance
What are hyper and hypotension?
Hypertension = abnormally high blood pressure
Hypotension = abnormally low blood pressure
What are the 4 key responses to exercise?
Increase in HR
Increase in Q
Increase in systolic BP
Redistribution of blood
Describe the redistribution of blood - not what happens
- Blood flows to tissue in proportion to their metabolic demands
- Major portion of exercise cardiac output diverts to active muscles
- Increase from 7ml per 100g (rest) to 75ml per 100g of muscle (exercise)
What are the 2 regulation systems of the heart?
Parasympathetic and sympathetic nervous system
Describe the parasympathetic nervous system - which nerve, role
Slows HR by inhibiting SA + AV node
- via the vagus nerve
Describe the sympathetic nervous system - which nerve, role
Increases HR by stimulating SA + AV node
- via cardiac accelerator nerve
Overview of regulation of HR
2 systems
- low resting HR due to parasympathetic tone
- increase in HR at onset of exercise - initial increase is due to parasympathetic withdrawal
- up to 100bpm - later increase is due to increase SNS stimulation
What causes an increased SV - what are the 2 ways?
Increased force of contraction
- Increased SNS activation = effects circulating adrenaline + noradrenaline - direct stimulation of heart
- Increased end diastolic volume (EDV) = increased stretch of sarcomeres - increased force of contraction
- training can improve LV compliance
List the 4 factors affecting EDV
- Increased activity of sympathetic nerves to veins
- Increased blood volume
- Increased skeletal muscle pump
- Increased inspiration movements
ALL ABOUT RETURNING BLOOD BACK TO HEART
What are the 6 key functions of the digestive system?
- Ingestion - taking food into body
- Mechanical processing - chewing, churning
- Digestion - larger -> smaller
- Secretion - litres of fluid (dissolve + lubricate) and buffers/ enzymes
- Absorption
- Excretion - defecate to remove waste
List the major subdivisions of the digestive tract
Oral cavity, teeth, tongue
Pharynx
Oesophagus
Stomach, small + large intestine
List the accessory organs of the digestive system
Salivary glands
Liver
Gallbladder
Pancreas
What is the peritoneum?
A serous membrane
- visceral layer covers organs - abdominal organs
- parietal layer lines cavities - abdominopelvic cavity
Peritoneal fluid - 7L/day are produced = lubrication
What are mesenteries?
A series of membranes + ligaments that suspend portions of digestive tract
- essentially a fold in peritoneum attaching intestines to stomach wall
- allows passage of blood vessels, nerves + lymphatic vessels
What does the digestive tract protect against?
Protects against…
- digestive acids + enzymes
- mechanical stresses
- bacteria - pathogens
List the histological layers of the digestive tract
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
What’s the role of plica circularis within the digestive tract?
Helps to increase SA of small intestine to promote efficient nutrient absorption
Describe + explain what the mucosa is made up of
Stratified squamous mucosal epithelium - in oral cavity, pharynx + oesophagus
- contains rapidly dividing cells = provide protection
- simple columnar mucosa cells elsewhere for absorption
Lamina propria - areolar tissue with blood, lymphatic vessels + nerve endings = protective layer in oral cavity
Muscularis mucosae - smooth muscle layer consisting of…
- inner circular layer = makes tract smaller
- outer longitudinal layer = makes tract shorter
Describe the submucosa
A layer of dense, irregular connective tissue
- has large blood vessels + lymphatic vessels
- may contain exocrine glands to secrete buffers + enzymes into tract
Submucosa plexus = neural network to innervate mucosa + submucosa
Describe the Muscularis externa + what it’s coordinated by
Smooth muscle cells consisting of inner circular and outer longitudinal layers
The movements of muscles are coordinated by enteric nervous system
- sensory, inter + motor neuron’s = contraction for muscles
- innervated by parasympathetic division of ANS to stimulate increased digestion
Describe the serosa
It’s a serous membrane covering Muscularis externa in most of digestive tract
- replaced by adventitia (dense sheath of collagen fibres to attach adjacent structures) in oral cavity, pharynx, oesophagus + rectum
How do digestive materials move along the tract?
- Rhythmic cycles of smooth muscle activity controlled by pacesetter cells
- Peristalsis
- Segmentation
Describe what rhythmic cycles of smooth muscle is (movement in digestive tract)
Smooth muscle located in Muscularis mucosae + externa
- cells undergo spontaneous depolarisation through entire muscular sheet
What is peristalsis?
Waves of muscular contraction
- Contraction of circular muscles behind bolus
- Contraction of longitudinal muscles ahead of bolus
- Contraction in circular muscle layer forces bolus forward
What is segmentation in relation to digestive movement?
Cycles of contraction that does not follow a set pattern
List the functions of the oral cavity
Sensory analysis
Mechanical processing
Lubrication
Limited digestion (carbs + lipids)
Passageway for food, liquid + air
What do salivary glands do + where are they located?
Produce 1-1.5L of saliva per day - controlled by (para)sympathetic stimulation
- contains water, buffers, electrolytes, mucins + antibodies
- found at parotid, sublingual and submandibular locations
List the roles of saliva
Lubricate mouth + contents
Dissolve chemicals
Initiate digestion of complex carbs by salivary amylase
Describe and explain the 4 phases of swallowing
- Buccal phase - bolus of food is pushed to back of mouth (oropharynx) by tongue
- Pharyngeal phase - as it passes down nasopharynx, it pushes back epiglottis (cartilage) to block trachea
- Oesophageal phase - food can then be swallowed down into oesophagus
- Bolus enters stomach
What does the oesophagus do, how does it remain in place, what does it consist of?
Conveys solid food and liquids to the stomach + prevents air from entering due to resting muscle tone
Adventitia anchors it to surrounding structures (tough connective tissue)
Consist of muscular layers + stratified squamous epithelium
What does the stomach function in?
- stores ingested food
- Mechanical breakdown (churning, muscular walls contract to mix food)
- begins chemical breakdown - by enzymes + acid (HCl - pH reduces to 2)
- production of intrinsic factor (facilitates absorption of vitamin B12)
What are some key components of the stomach?
Smooth muscle layers - circular, longitudinal, oblique
Folds - allows stomach to expand after large meal
Fundus (most superior part)
Pylorus (narrower part at exit)
What does the stomach lining consist of?
Simple columnar epithelium lines stomach - produces mucus
Gastric pits connect gastric glands in mucosa onto gastric surface - cells at base divide to replace superficial cells
Smooth muscle layers
What are the 2 stomach glands?
Gastric
Pyloric
Where are gastric glands located + what’s the role?
In fundus + body of stomach
Consists of…
- parietal cells - secrete intrinsic factor + HCI
- chief cells - secrete pepsinogen + converted to pepsin by HCI, then can breakdown proteins
- G cells - secrete gastrin (increase stomach activity)
Where are pyloric glands located + their role?
Where stomach narrows near to intestine
- produces mucous
- G cells secrete gastrin
- D cells release somatostatin (inhibits gastrin release)
Describe HCl formation by parietal cells
- carbonic anhydrase converts CO2 + H2O to carbonic acid to form hydrogen ions
- Counter transport mechanism ejects bicarbonate ions (from cell to bloodstream) and imports chloride ions
- Chloride ions diffuse across cell and exit through open channels into lumen of gastric gland
- Hydrogen ions are actively transported into lumen of gastric gland = HCI + low pH (weak acid when in parietal cells)
What mechanisms help protect the stomach from strong acids?
- mucous lining
- rapid cell division
- separated secretion of H and Cl in parietal cells
- secretion of inactive precursor (pepsinogen)
- stimulation of secretion only when needed
- inhibition of secretion - CCK, GIP, secretin
What are the regions of the small intestine + their functions?
Duodenum = 25cm long
- neutralises chyme by mixing it with digestive products
- fewer folds, fewer projections
Jejunum = 2.5m long
- chemical digestion + nutrient digestion
- many folds, large SA, finger-like projections
Ileum = 3.5m long
- contains lymphoid nodules with immune functions
Describe the structure of villi in the intestines
Villi are lined with columnar epithelial cells + has lacteal with a large fat content (for absorption)
- at base of villi = intestinal crypt - contains glands
- middle of villi = branch of lymphatic vessel called lacteal
What are the glands of the small intestine + what do they do?
Brush border enzymes - on intestinal microvilli
- break down materials in contact with brush border
- enteropeptidase activates pancreatic pro enzyme trypsinogen = trypsin
Enteroendocrine cells - produce hormones in response to pH change / nutrients
- cholecystokinin (CCK) + secretin = increase in enzyme/ bile secretion
- gastric inhibitory peptide (GIP) = inhibits gastrin activity
What do duodenal glands do?
Produces mucous = raises pH
What’s the role of intestinal juice?
Moistens chyme + keeps intestinal contents in solution + dissolved
- also buffers acids
What does the pancreas do?
Secretes pancreatic juice which contains pancreatic enzymes…
- pancreatic alpha-amylase to break down carbs
- pancreatic lipase = lipids
- nucleases = nucleotides
- proteases + peptides = proteins
Activated once they reach small intestine
What are functions of the 2 cells (endocrine and exocrine) of the pancreas?
Endocrine = secrete insulin + glucagon into bloodstream
Exocrine = secrete pancreatic juice (to ‘outside’ of body)
List some key structures of the liver + what its made up of
Made up of roughly 100,000 hexagonal lobules
Porta hepatis - opening to intestine (region of blood vessels)
Liver has 2 vessels - 1/3 blood from hepatic artery proper and 2/3 from hepatic portal vein
- this vein originates from… oesophagus, stomach, small intestine, large intestine
What do the portal areas of liver contain?
- branch of hepatic portal vein
- branch of hepatic artery proper
- branch of bile duct
Blood that flows past hepatocytes in the liver…
Then drains into…
- Absorb solutes and secrete proteins
- drains in sinusoids (then to central vein) and bile ducts
What are the key functions of the liver?
Metabolic regulation - carbs, amino acids, lipids and waste product removal
- vitamin + mineral storage
- drug inactivation
Haematological regulation - phagocytosis + antigen presentation
Bile production - break insoluble lipid droplets apart (emulsification)
Describe the storage + transport process of bile
- Liver secretes bile
- Bile is transported in bile duct to be stored in gallbladder
- When food enters small intestine - CCK is released = contraction of gallbladder and sphincter dilates so bile enters duodenum
- Bile salts then break apart lipid droplets via emulsification
Describe the structure + histology of large intestine
Wider in cross section, but a lot shorter than small intestine
Consists of… ascending colon, transverse and descending colon + sigmoid colon
Ileocaecal valve = opens to allow contents of small intestine to pass
Lack villi
Abundant mucous cells - for lubrication due to less fluid
Longitudinal layer of Muscularis externa
What are the key functions of the large intestine?
Reabsorption of water, bile salts, vitamins + organic wastes
Site of bacterial vitamin production - K, biotin, B
Compaction of intestinal contents into faeces
Storage of faeces until defecation
NEURAL CONTROL OF INTESTINAL MOVEMENT
Describe central control
Parasympathetic stimulation = increased motility + secretion
Sympathetic stimulation = inhibits above
NEURAL CONTROL OF INTESTINAL MOVEMENT
Describe the local reflexes
Refers to local responses to stretch/ pH changes
- Stretch receptors allow expansion of walls when part of gut gets full
- as food enters stomach (stomach is less acidic) and as it leaves (small intestine is more acidic)
NEURAL CONTROL OF INTESTINAL MOVEMENT
What are the 2 central gastric reflexes + describe them?
Gastroenteric reflex - stimulates motility + secretion along entire small intestine
Gastroileal reflex - triggers opening of ileocaecal valve allowing materials to pass from small intestine to large
Explain the hormonal control of the intestines
- Gastrin increases activity of stomach (acid production, smooth muscle = churning)
- once chyme moves into duodenum - gastrin inhibitory peptide (GIP) is produced to inhibit gastrin + also signals release of insulin (to breakdown glucose) - In duodenum… secretin + CCK are produced to stimulate release of pancreatic enzymes + trigger bile secretion
- VIP - vasoactive intestinal peptide - increases blood flow to intestines
After digestion, molecules released into bloodstream are…
- absorbed by cells
- broken down to provide energy for ATP synthesis
- used to synthesise carbs, proteins + lipids
Describe the digestion of carbohydrates (4)
- Preliminary breakdown in oral cavity by salivary amylase = disaccharides/ tri
- Pancreatic alpha-amylase is secreted into small intestine = break down into smaller sugars
- Enzymes on brush borders (lactase, maltase, sucrase) breakdown di into monosaccharides
- Then transported to hepatic portal system via hepatic portal vein then re enter circulation
Describe digestion of fats (4)
- Preliminary breakdown in oral cavity by lingual lipase
- Bile + pancreatic lipase at small intestines = monoglycerides + fatty acids
- Then diffuse through columnar epithelium of intestinal mucosa until lacteals
- Lacteals feed into lymphatic system then to inferior vena cava
Describe digestion of proteins (4)
- Preliminary digestion in stomach by pepsin
- Action of proteases arising from pancreas (in small intestine) = polypeptides to amino acids
- Brush border enzymes assist
- Amino acids travel to capillaries through hepatic portal vein + system to be filtered in liver
What does the lymphatic system comprise of?
Lymphatic tissue
Bone Marrow
Lymph
Lymphatic vessels
What do lymphoid cells respond to?
Protect us against disease responding to…
- pathogens
- toxins
- abnormal body cells (cancers)
What are the main pathogens that cause disease - list some examples of each
Viruses - bacteriophage, simian virus, Epstein Barr virus (glandular fever)
Bacteria - E.coli (food poisoning)
Fungi - candidiasis (oral thrush)
Parasites - schistosome
Describe the 4 components of the lymphatic tissue
- Lymph - similar to plasma + blood (fluid)
- Lymphatic vessels - carry lymph from peripheral tissues to venous system
- Lymphoid tissue + organs - spleen + tonsils, RBM + thymus
- Lymphoid cells - lymphocytes, phagocytes
List the functions of the lymphatic system
- To produce, maintain and distribute lymphocytes
- lymphocytes produced in lymphoid tissues, organs + RBM - Return fluid and solutes from peripheral tissues to blood
- Distribute hormones, nutrients + waste products from tissue of origin to circulation
Describe lymphatic vessels structure + where located
Begin as lymphatic capillaries, which are closed on one end
- located in between cells of many tissues
Formed from merging of lymphatic capillaries
- many thin walls + valves
- irregular in shape
Describe the differences between lymphatic vessels + blood capillaries [4]
- Starts as blind pockets rather than tubes
- Larger diameters
- Thinner walls
- Flat or irregular in section
After lymphatic vessels, where does the lymph go and describe them
Lymphatic trunks… which include lumbar, intestinal, bronchomediastinal, subclavian and jugular trunks
Lymph trunks then merge to form either thoracic duct or right lymphatic duct
What do the right lymphatic duct and thoracic duct do?
Right lymphatic = drains everything from top right quadrant
Thoracic duct = drains everything else (lower half of body)
What are the 3 key circulating lymphocytes?
T cells = thymus dependant
B cells = bone-marrow derived
NK cells = natural killer cells - also bone marrow derived
Describe RBM production of B / NK / T cells
- RBM produces hemocytoblasts = immature lymphoid cells
- These can then become stem cells
- Then able to differentiate into B / NK cells
- Or migrate to thymus to differentiate into T cells
- Cells then move into periphery + involved in immune response to infection
Name the different primary and secondary lymphatic organs
Primary lymphatic organs - where immune cells become immunocompetent (will meet antigen + mature)
- red bone marrow
- thymus
Secondary lymphatic organs
- lymph nodes (+ lymphoid nodules inside)
- spleen
What are the 2 vessels entering / exiting lymph node?
Afferent vessel = into lymph node
Efferent vessel = removes lymph fluid from node
List + describe the key parts of a lymph node
- subcapsular sinus
- germinal centre = B cells mature here + start to produce antibodies
- medulla cortex = find more B cells here + macrophages + plasma cells
- inner cortex = where T cells + dendritic cells are found
What are the differences between lymph organs and lymphoid nodules?
Lymph organs are separated from surrounding tissues by fibrous capsule
Whereas…
Lymphoid nodules are a bundle of lymphoid tissue without fibrous capsule
List the flow of lymph through the body
Interstitial fluid -> lymph capillaries -> lymph vessels -> lymph trunks -> lymph ducts -> subclavian veins
Describe lymph node circulation - afferent lymphatics
Flows through lymph node in a network of sinuses
- from subcapsular space (contains macrophages + dendritic cells)
- through outer cortex - contains B cells within germinal centres
- through deep cortex - dominated by T cells
- through the core (medulla) - contains B + plasma cells
- finally into hilum + efferent lymphatics
What’s the function of the lymph node?
Acts as a filter to purify the lymph before it returns to venous circulation by removing…
- debris
- pathogens
- 99% of antigens
Where are lymph nodes found within the body?
In gut, trachea, lungs + thoracic duct - protects against pathogens in digestive + respiratory systems
(Glands) - at groin + base of neck which swell in response to inflammation
What is lymphadenopathy?
Chronic or excessive enlargement of lymph nodes - indicates infections, endocrine disorders or cancer
Explain non-specific (innate) and specific immunity
Innate - block or attack any potential pathogen
- present from birth
- has no memory (no memory cells made)
Specific - identify, attack + develop immunity to a specific antigen
- acquired in response to antigens
List and explain briefly the 7 non-specific defences to pathogens
- Physical barriers - deny access to pathogens
- Phagocytic cells - engulf pathogens
- Immunological surveillance (NK cells) - flow around in blood + if meet infected / rogue cancer cell they’ll kill it
- Interferons (antiviral) - slow spread of disease
- Complement system - cover pathogen in complement proteins (homing beacon) or form complex (pore to compromise cell wall)
- Inflammation - hot sensation caused by expanding blood vessels
- Fever - mobilises defences, inhibits pathogens
Describe phagocytosis + antigen presentation - VERY simple
- Pathogen is engulfed
- Pathogen gets lysed
- Lysosome merges with something from ER which has class II MHC protein in it
- MHC protein takes bit of antigen + ships it to surface of antigen-presenting cell so T cell can recognise it
What are the 2 classes of phagocytes?
Microphages - neutrophils + eosinophils (called granulocytes)
- leave blood stream + enter peripheral tissues to fight infections
Macrophages - derived from monocytes
- distributed throughout body + may be fixed or free
- make up monocyte-macrophage system
How do activated macrophages respond to pathogens? [3 ways]
- Engulf pathogen + destroy it with lysosomal enzymes
- Bind to pathogen so other cells can destroy it
- Destroy pathogen by releasing toxic chemicals into interstitial fluid
How do NK cells actually kill the target cells - Immunological surveillance?
- NK cells bind to target cells (if normal - let it go)
- If infected, it lines up its endoplasmic reticulum and Golgi
- Then secretes perforin (little proteins) which form a small pore on the surface of target cells and cause it to lyse by osmosis
What are interferons released by + what are the 3 kinds - what do they do?
They are proteins released by activated lymphocytes + macrophages
- Alpha-interferons = produced by leukocytes + stimulate NK cells (assist in proliferation)
- Beta-interferons = secreted by fibrocytes - slow inflammation
- Gamma-interferons = secreted by T cells + NK cells - stimulates macrophage activity
Describe what complement cascade is as part of the complement system
11 complement (C) proteins named C1-C11 which circulate throughout blood + tissues
- the activation of one protein enzymatically cleaves and activates the next protein in the cascade
What are the 4 effects of complement activation?
- Attraction of phagocytes to site of infection
- Enhancement of phagocytosis by opsonisation - complement proteins dotted on surface
- Stimulation of inflammation
- Destruction of target cells membrane by forming MACs
What are the 2 pathways of activation for the complement system?
Fast and slow
classical (fast) - antibody-antigen complexes bind to C1 = forms a C3 convertase = C3b
alternative (slow) - many factors required to interact with C3b to form c3 convertase to activate more c3
- conversion of inactive protein (C3) to active form (C3b)
- this forms pores in bacterial cell wall (via membrane attack complex) = destruction of bacteria
Inflammation + Tissue Repair
What are some responses to tissue damage?
- increased blood flow
- mast cells release histamine
- phagocytes (neutrophils) move to site
- neutrophils remove debris
- clot formation / removal of debris
- activation of fibrinogen = tissue repair
Fever
How does our body temp increase + what effects does it cause?
Due to release of pyrogen = a pyrogen is any material that causes the hypothalamus to raise body temp
- mobilises defences
- accelerates repair
- inhibits pathogens
What are the 3 kinds of T cells?
T cells and B cells mature in response to a particular pathogen…
- cytotoxic T cells (CD8 - mechanism to differentiate between cell types)
- helper T cells (CD4) - help B cells produce antibodies + help T cells do the killing
- suppressor T cells - inhibit function of T and B cells
Eventually clone to form plasma + memory cells
What are the 2 divisions of specific immunity + describe them
Cell mediated (T cells)
- T cells only recognise fragments of antigenic proteins that are processed + presented in a certain way (via MHC proteins)
Humoral / antibody-mediated (B cells)
- B cells can recognise + bind to antigens in lymph, interstitial fluids + plasma
- also recognises antigens presented on MHC class II proteins
What are MHC proteins for, what are the types?
Used to distinguish ‘self’ and ‘non-self’
- Class I = on all nucleated cells
- Class II = on antigen-presenting cells (APCs) + lymphocytes
How is an infection recognised by specific immune system?
By recognising foreign antigens as either…
- free living (exogenous)
- inside host cells (endogenous)
White blood cells can differentiate ‘self-antigens’ EXPRESSED on the surface from ‘non-self antigens’ PRESENTED on cell surface
Lymphoid precursor cells are exposed to different self-antigens during development and either…
Mature - become clones that are not specific for self-antigens
Deleted
Mature to suppress self-antigen recognition
What’s the difference between antigen EXPRESSION and antigen PRESENTATION
Expression = via class I MHC proteins on cell membrane of infected somatic cells
Antigen presentation = via class II MHC proteins involved with specific immunity - APCs and lymphocytes
Describe the activation + clonal selection of Helper T cells [3]
- T cell binds to antigen presented on surface of APC - presented by MHC class II
- Binding process activates T cell - receives signal to proliferate (grows + divides many times)
- Some become memory, other secrete IL-2 to drive proliferation of killer T cells and NK cells
Describe the activation + clonal selection of cytotoxic T cells
- MHC class I molecule expresses antigen and inactive cytotoxic T cell binds
- Assistance from CD8 protein also
- Enhanced by IL-2 (released by helper T cell)
- Binding process stimulates + activates cytotoxic T cell and undergoes clonal selection
- Some go on to attack infected body cells, others become memory cells
Describe the activity of cytotoxic T cells
- Activated cytotoxic T cell releases granenzymes which break down cell membrane of infected body cell
- Cell undergoes apoptosis + microbes are released into local area
- Phagocytes come along and engulf microbes + parts of dead cells
- At same time, cytotoxic T cell releases granulysin + perforin = causes infected body cell to lyse = destruction
List some key structural parts of the antibody
- antigen binding site
- light and heavy polypeptide chain
- disulfide bond
- variable segment
- complement binding site
What are the 5 types of antibodies?
- IgG- 80% of all antibodies, passive immunity to placenta
- IgA- glandular secretions - mucus, saliva, breast milk, tears, sweat
- IgM
- IgD
- IgE
Describe the activation + clonal selections of B cells
- Inactive B cell has a B cell receptor on its surface
- It will bind to a microbe which stimulates B cell activation
- Co-stimulation by Helper T cell via several interleukins
- Then get formation of B cell clone = become plasma + memory cells
Describe the primary and secondary responses to immunity with reference to IgG and IgM levels
Primary - low levels of IgG and IgM in general, with spikes of IgG at 2 weeks and IgM at 1 week
Secondary - levels of IgM remain the same however spikes a lot sooner (less than a week) however IgG levels massively increase, however spikes at the same time
What are the 2 forms of immunity?
Active - producing an immune response - naturally or induced via vaccine
Passive - produced by transfer of antibodies from another person - natural or induced by antibodies administration
What are some issues regarding the immune system?
- allergy
- autoimmune disease
- transplant rejection
- diseases of immune system - primary + secondary
Describe what an allergy is - what it leads to and mediated by
Occurs when a person is overly reactive to a substance that is well-tolerated by most others
- allergic reactions leads to tissue damage
Mediated by IgE - mast cells produce too much of it upon exposure
Describe what autoimmune diseases are
Occurs when the immune system fails to display self-tolerance and instead attacks the persons own body tissues
- e.g. rheumatoid arthritis, chrons disease, type 1 diabetes
Describe how a transplant rejection can occur
As a result of the body recognising the transplanted organs/ tissues as non-self and mounting a specific immune response against it
- usually treated with immunosuppressants
Give an example of primary and secondary immune system diseases
Primary - severe combined immunodeficiency syndrome (SCID)
Secondary - HIV
What is the role of the endocrine system?
It regulates long term processes…
- growth
- development
- reproduction
What does the endocrine system consist of?
Hormones - chemical messengers to relay info and instructions between cells
Glands - produce the hormones
What are the key organs of the endocrine system + briefly describe what they do?
Hypothalamus - production of ADH + oxytocin
Pituitary gland - anterior lobe (produces many hormones) and posterior lobe (releases what hypothalamus produces)
Pineal gland - produces melatonin
How does endocrine communication occur?
Transmission via the bloodstream with chemical mediators being hormones
- target cells are primarily in other tissues / organs and must have correct receptors
Describe what endocrine glands are, what they do etc
They are ductless glands comprised of endocrine cells
- have a good blood supply
They secrete hormones directly into the blood stream
What are hormones + what’s their role?
Chemical messengers produced and secreted by endocrine cells into bloodstream
- they bind to receptors (binding sites) in target cells
This stimulates gene expression / protein synthesis to regulate, integrate and control a range of physiologic functions
Anabolic steroid hormones
What are they involved in?
They regulate muscle protein production by binding to receptors in the muscle = build muscles
- not all steroid hormones have this (oestrogen, progesterone and cortisol don’t) = shows very specific effects
Anabolic steroid hormones
What are the risks of using them?
- Early skeletal and sexual maturation = stunted growth
- Damage to liver + CV systems
- Male - reduces sperm count, infertility, baldness, higher risk of prostate cancer
- Female - facial hair, male pattern baldness, cessation of menstruation cycles
What are the 3 main categories of hormones + describe
- Amino acid derivatives - small molecules, structurally similar to amino acids
- usually from tyrosine (thyroid hormones + catecholamines) - Peptide hormones - consists of chains of amino acids - largest class
- thyroid-stimulating hormone, insulin etc - Lipid derivatives - 2 classes of lipid-based hormones (steroid + eicosanoids)
- fat-soluble, steroids usually derived from cholesterol (androgens, testosterone)
Why do thyroid and steroid hormones not mix well in the blood but diffuse well through lipid-bilayer?
They are lipid soluble = easy diffusion through cell membranes
Why do catecholamines and peptide hormones diffuse well into the blood but not across cell membranes?
They are water-soluble = mix well in blood
Describe hormone receptors locations [2]
On cell membrane…
- includes receptors for non-lipid soluble hormones - (nor)epinephrine, all peptide hormones + eicosanoids
- trigger signalling cascades inside cell involving G proteins + secondary messengers (cyclic AMP)
Inside cell…
- receptors for all steroid hormones + thyroid hormones
Hormonal action via cell membrane receptors - explain the activation of cAMP
- Activated G protein activates enzyme adenylate cyclase
- This converts ATP to cAMP
- cAMP activates kinase enzymes
- Activated kinases effect target cells
In relation to cAMP levels, what stimulates their increase and breakdown?
Adrenaline (epinephrine) binding to BETA receptors INCREASES cAMP
Adrenaline binding to ALPHA receptors stimulates cAMP BREAKDOWN
Describe the 5 steps of hormonal action via intracellular receptors
STEROID HORMONES
- Diffusion of hormone through membrane lipids
- Binding of hormone to cytoplasmic or nuclear receptors
- Binding of hormone receptor complex to DNA (after entering nucleus)
- Gene activation
- Transcription and mRNA production
- Translation and protein synthesis = alteration of cellular structure = target cell response
How is the previous process different for thyroid hormones?
- Transport across cell membrane
- Binding to receptors at mitochondria and nucleus = increased ATP production
- Binding of hormone-receptor complex to DNA
- Gene activation
- Transcription and mRNA production
- Translation and protein synthesis = alteration of cellular activity = target cell response
What happens to hormones after they caused a target cell response?
Free hormones = remain functional for less than 1 hour
- they bind to target cell receptors or broken down in liver, kidneys or by enzymes in plasma
Thyroid and steroid hormones = remain in circulation much longer because most are bound
- enter bloodstream - more than 99% become attached to special transport proteins
What are the 2 structures that regulate the endocrine system?
Hypothalamus and pituitary glands
What does the hypothalamus do?
Produces ADH (regulates water levels), oxytocin and regulatory hormones
- acts as an interface between nervous and endocrine systems
- regulatory hormones affect pituitary function
What does the pituitary gland do?
Anterior lobe = secretes ACTH, TSH, GH, PRL, FSH, LH, MSH (control other endocrine organs)
Posterior lobe = stores and secretes oxytocin and ADH
What are the 3 ways the hypothalamus can work?
- Production of ADH and oxytocin - released into bloodstream after transport via neurons
- Secretion of regulatory hormones to control activity of anterior lobe in pituitary gland - travel to anterior lobe of pituitary + secreted when needed to control other endocrine organs (most common)
- Control of sympathetic output to adrenal medullae - impulse travel via preganglionic motor fibres so nerves activate cells in adrenal medulla to produce catecholamines
Describe the pituitary gland location + structure
Situated inside sphenoid bone at base of cranium
Anterior lobe consists of 3 regions - pars tuberalis, distalis, intermedia
- comprised of endocrine tissue (produces anterior pituitary hormones)
Posterior lobe = neural tissue (neurons that release ADH and oxytocin)
Pars intermedia = produces melanocyte stimulating hormone (MSH)
What is the hypophyseal portal system?
A portal system is a vein that travels from one capillary bed to another second bed before travelling back to the heart
- neurosecretory neurons at median eminence secrete regulatory factors ->
- these enter fenestrated capillaries in capillary bed in hypothalamus ->
- portal veins ->
- capillary bed in anterior pituitary
Wha type of feedback is endocrine secretion?
Negative - when level of (hormone 2) gets high in target cells, negative feedback leads to inhibition of releasing hormone at start of cycle to decrease levels
What are the additional feedback controls of the endocrine system?
Prolactin regulation - stimulates mammary glands to stimulate lactation
- hypothalamus produces releasing factor (PRF) and inhibiting hormone (PIF)
Growth hormone regulation - stimulates growth of skeletal muscle, cartilage and many other tissues
- hypothalamus produces releasing hormone (GH-RH) and inhibiting hormone (GH-IH)
- these act on liver to produce somatomedins which stimulate growth
Describe the effects of growth hormone after release from anterior pituitary
Acts on liver to release somatomedins (insulin-like growth factors) = stimulate tissue growth + increase amino acid uptake/ protein synthesis
Growth hormone acts directly on tissues to…
1. Stimulates cell division in epithelial and connective tissue
2. Stimulate triglyceride breakdown in adipocytes
3. Stimulates liver glycogen breakdown
What does the anterior pituitary gland produce?
Growth hormone
What does the posterior pituitary glands produce?
Produces ADH (from osmoreceptor stimulation) as well as oxytocin
Describe the role of ADH hormone
Detects changes in water fluid levels to see if there’s dehydration or changes in electrolytes
- when dehydration = stimulation of ADH = water re absorption to maintain blood volume + pressure
Describe the role of oxytocin
Produces uterine contractions during childbirth - stimulated by sensory stimulation
- acts particularly on uterus in women or prostate gland in men
What’s the effects of alcohol on ADH?
It inhibits ADH release = increased urination and therefore dehydration
What’s the structure + role of the pineal gland and its hormone it releases?
Contains pinealocytes in between neural tissue (collaterals from visual pathway) which secretes melatonin…
- low production during daylight and high production of melatonin at night
- melatonin influences circadian rhythm (antioxidant)
Describe the location of the thyroid gland
Anterior to thyroid cartilage and larynx (in the neck)
- 2 lobes that are connected by a narrow isthmus
What’s the function of the thyroid gland?
It functions in storing and secreting thyroid hormones - thyroxin (T4) and triiodothyronine (T3)
What effects do thyroid hormones have on the body? [8]
- Increase sodium-potassium ATPase production
- Affect mitochondrial activity
- Large effects on metabolic rate
- increase O2 and energy consumption
- Increase HR
- Increase sensitivity to sympathetic stimulation
- Stimulate RBC formation
- Increase bone turnover
Describe thyroid follicles and their role
Structure: Hollow spheres lined by cuboidal epithelial surrounded by capillaries
- cells consist of protein rich fluid called colloid
Role: follicle cells synthesise tyrosine rich thyroglobulin
- iodine is then incorporated to form thyroxine and triiodothyronine
Describe what C cells produce (thyroid) and what happens when levels of (certain molecule) are high
C cells produce calcitonin (important for calcium homeostasis)
- it is released when calcium levels are HIGH to increase storage of calcium in bone and excretion of calcium in kidney
- most calcium secreted into urine if it is high in diet
High calcium levels detected by C Cells -> calcitonin production in thyroid gland -> increased calcium excretion by kidney -> calcium deposited into bone -> restore homeostasis
When a person has an iodine deficiency, what can this cause?
Derbyshire Neck - increased swelling of thyroid gland due to production of thyroglobulin but no iodine can be incorporated to synthesise thyroid hormones
- expect to see low T4 and high TRH
What happens when calcium concentration falls?
- Detected by parathyroid glands at posterior of thyroid
- Stimulates parathyroid hormone to be released
- These have 3 effects - increased re absorption of calcium by kidneys, calcium release from bone + increased calcitrol production which causes calcium absorption by digestive system
Where are parathyroid glands located and what’s their role?
Small glands on the posterior of thyroid (2 on each lobe)
- act to increase serum calcium when levels decline
Where are adrenal glands located and describe the structure
Sit on top of the kidneys
- outer layer = cortex
- inner layer = medulla
- within the cortex = zona reticularis, fasciculata and glomerulosa
Describe the functions of the medulla and cortex
Cortex - produces a range of steroid hormones (will see in more detail on next page)
Medulla - produces catecholamines which are used in fight or flight response
- increase blood glucose, HR etc
Describe what the zona reticularis, fasciculata and glomerulosa produce/function in
Reticularis - produce androgens (steroid hormones)
- anabolic effects - stimulate muscle but fairly weak
- note huge function in men but help women maintain lean mass
- can be converted to oestrogen in body - important after menopause
Fasciculata- produces glucocorticoids (cortisol)
- reacts to a sustained stressor (unlike fight or flight)
- promotes glucose synthesis, fat and protein catabolism + has anti-inflammatory effects
Glomerulosa - produces mineralocorticoids (aldosterone)
- affects electrolytes composition alongside ADH
If BP and Blood volume fall, what occurs?
- Detected by kidneys
- They release EPO and renin
- Renin activates the angiotensinogen system
- Increases aldosterone secretion from adrenal glands + ADH from posterior pituitary
- This increase retention of fluid
Where is the pancreas located and give an overview of its role
Located towards the top of the small intestine (duodenum)
- has an exocrine function that secretes digestive fluids through a duct into small intestine
What are the pancreatic islet and acini
Islet of Langerhans - contains endocrine cells
- alpha cells - produces glucagon = increases blood glucose
- beta cells - produce insulin = lowers blood glucose
Acini - exocrine cells that secrete into digestive tract
Describe the role of insulin in blood glucose regulation
- Blood glucose levels increase
- Detected by pancreatic beta cells
- These secrete insulin
- Insulin increases rate of glucose transport into target cells, increases rate of glucose utilisation + ATP generation, conversion of glucose to glycogen, more amino acid absorption and protein synthesis and increase triglyceride synthesis in adipose tissue
Why is high glucose levels bad?
Leads to diabetes and can damage small blood vessels
Describe the role of glucagon in blood glucose regulation
- Blood glucose levels decline
- Detected by pancreatic alpha cells
- Alpha cells secrete glucagon
- Glucagon leads to increased breakdown of glycogen to glucose, increase breakdown of fat to fatty acid and increased synthesis and release of glucose
What causes diabetes mellitus?
Abnormally high blood glucose levels - hyperglycaemia
If untreated it could result in…
- kidney / retinal damage
- perishable nerve damage - less sensation etc
- increased CV disease risk
What are the 2 types of diabetes, explain
Type 1 - insulin dependant
- results from inadequate insulin production
- therefore require an insulin injection
Type 2 - non-insulin dependent
- tissues respond less to insulin
- often managed with diet and exercise
Describe the different patterns of hormonal interaction
- Antagonistic (opposing) effects - 2 hormones have opposing effects (PTH + Calcitonin or glucagon + insulin)
- Synergistic (additive) effects - 2 hormones with similar effects create an amplified response (growth hormone and glucocorticoids)
- Permissive effects - one hormone is necessary for another to produce effects (thyroid hormone for effects of adrenaline)
- Integrative effects - hormones produce different but complementary effects
List the range of hormones required for normal growth
Growth hormone - protein synthesis and cellular growth
Thyroid hormones - nervous system development
Insulin - supply of energy and nutrients
Parathyroid hormone + calcitrol - calcium absorption + deposition in bones
Reproductive hormones - cell growth + differentiation / secondary sexual hormones
Some organs have secondary endocrine functions, what are they? [7]
- Heart - secrete natriuretic peptides = reduce BP and volume
- Thymus - secrete thymosins = promote lymphocyte development
- Adipose tissue - secretes leptin = suppresses appetite
- Digestive tract - hormones involved in coordination of system functions, glucose metabolism + appetite
- Kidneys - secrete EPO (RBC production), calcitrol (calcium absorption) and renin (control of BP + volume)
- Gonads - androgens (testosterone) and inhibin
- Ovaries - estrogens, progestins and inhibin
What does the general adaptation syndrome describe + what are the 3 phases?
Describes the process your body goes through when exposed to any kind of stress - positive or negative - FIGHT OR FLIGHT
- Alarm phase
- Resistance phase
- Exhaustion phase
Describe the alarm phase of the general adaptation system
Immediate short term response to crises
- Encounter challenge - sympathetic stimulation causing increased vagal activity to increase catecholamine secretion from adrenal medulla
- Mobilisation of glucose reserves - breakdown
- Changes in circulation
- Increase in heart and respiratory rates
- Increased energy use by cells
Describe the resistance phase of the general adaptation system
Long term metabolic adjustment
- Mobilisation of remaining energy reserves - lipids released by adipose tissue, amino acids from muscle
- Conservation of glucose - peripheral tissue breaks down lipids to obtain energy
- Elevation of blood glucose concentration - liver synthesises glucose from other carbs
- Conservation of salts + water and loss of K+ and H+
Describe the exhaustion phase of the general adaptation system - what’s it caused by?
Collapse of vital systems caused by…
- exhaustion of lipid reserves
- inability to produce glucocorticoids
- failure of electrolyte balance
- cumulative structural / functional damage to vital organs
