Integration of Physiological Systems Flashcards
What does the frontal lobe control?
What does the parietal lobe control?
What does the temporal lobe control?
What does the occipital lobe control?
What does the cerebellum control?
Decisions, emotion, speech, planning, motor control.
Sensory information
Hearing, facial recognition, memory
Visual information
Simple coordination, balance
Describe the features of the primary motor cortex.
Has a somatotopic map
Initiates movement
Requires the least electrical stimulation to work
Describe the features of the premotor area.
Split into dorsal and ventral: dorsal has full somatotopic map, ventral has no leg region on its map
Initiates controlled movement, acts through primary cortex
Requires more electrical stimulation than primary to work
Describe the features of the supplementary motor cortex (SMA).
Split into SMA proper and preSMA
Proper has map, linked to all others, requires greater voltage
Pre doesn’t initiate movement, not connected to other motor cortextes, involved in planning complex movement
Describe the features of the cingulate motor areas.
Three types: dorsal, ventra and rostral, all have somatotopic maps
Connected to all other motor areas
Involved in anticipation of movement
What are the differences between a receptor potential and an action potential?
RP is graded whereas an AP is not, RP can be hyperpolarising or depolarising whereas action potentials always lead to depolarisation of the membrane
RP tapers out, AP frequency reduces
How do Meissner and pacinian corpuscles respond to different forms of physical contact?
How do Ruffini corpuscles and Merkel discs respond to different forms of physical contact?
Adapt rapidly to stroking and vibration
Adapt slowly to stretch of skin and steady pressure/ texture
What tells you about the intensity of a sensory stimulus?
The frequency of nerve impulses
What are the functions of these brain structures:
- Cerebellum
- Thalamus
- Brainstem
- Basalganglia
Coordinate movement, equilibrium
Major sensory relay and intergration centre
Basal, crucial for deeply programmed functions
Control and refine movement
What area of the brain did patients studied by Broca and Wernick have damage to?
What did they find?
Broca - damage to left posterior inferior frontal gyrus, these patients couldn’t’ speak
Wernicke - left posterior section of the superior temporal gyrus, these patients couldn’t understand speech
What is the corpus callosum?
A wide flat bundle of largely myelinated nerve fibres which allow the brain hemispheres to communicate. Enables the brain to coordinate sensory and motor impulses
What are the ligands for gustatory receptors?
Sour: taste of acids, detection of protons (H+)
Salty: Na+
Umami: glutamate, nucleotides
Sweet and bitter: more complex larger molecules, various organic molecules
What type of cells are taste buds?
Epithelial or glial
Describe each of these taste bud cell types (i.e. what taste they perceive, their form etc.):
- glial like cells
- receptor cells
- presynaptic cells
Glial like cells - most abundant, responsible for perceiving salt, enclose the other cells in thin lamellae, glial cells don’t form synapses
Receptor cells - receptors for sweet, bitter or umami, don’t form synapses
Presynaptic cells - express ion channel for sour taste, behave like a typical receptor, form synapses with primary gustatory neurones
What is decussation?
Do taste signals do it?
Crossing over to opposite brain signals
No
How does olfactory transduction occur?
Only one basic signalling system, odorants bind to specific G-protein coupled receptors with cAMP as a second messenger. Each receptor has a specific receptor protein. The outside region is hypervariable the insides are identical and interact with the signalling system
How does odorant perception occur?
Receptors have different ranges, odorants activate different combinations of receptors, odorants bind to G-protein membrane protein which activates a cascade that depolarises the cell
What is the range of human hearing?
In what range is human hearing most sensitive?
Above what amplitude does sound cause damage to hearing?
What amplitude is conversation at?
20 - 20,000Hz
1000 - 3000Hz
80dB
~60dB
What do theses areas of the human ear do?
- outer ear
- eardrum
- middle ear cavity
Outer ear (pinna) - amplifies and directs sound
Eardrum (tympanic membrane) - vibrates with external sound
Middle ear cavity - filled with air contains
- malleus (hammer)
- incus (anvil)
- stapes (stirrup)
Which amplify movement of eardrum into oval window
Inner ear (cochlea) filled with endolymph which vibrates with the movement of the oval window so sound can be detected by sensory receptors
How does the attenuation reflex work?
Loud sounds make two muscles (tensor tympani muscle and stapedius muscle) contract making the chain of ossicles more rigid and diminishing sound conduction
What does the auditory (eustachian tube) do?
Exposes the middle ear to atmospheric pressure by connecting it to the pharynx, normally closed but opens during yawning, swallowing or sneezing
What transmitter do ear hair cells use?
Glutamate
Describe these types of hearing loss and their causes:
- conductive
- sensorineural
- central
Damage to external or middle ear, ear clogged with wax, damage to tympanic membrane, fluid in middle ear, disease/ trauma to malleus
Damage to inner ear structures, treat with implants, excessive noise damages hair cells, they are also lost with age
Damage to neural pathways or auditory cortex, uncommon cause
What does the vestibular system do?
What do the macula do?
What do the crista do?
Detects change in motion and head position, located in the inner ear, has two receptors macula and crista
Perceive gravity using calcium carbonate crystals
Perceive acceleration/ deceleration of movement, movement shifts the jelly like cupula and triggers a response in hair cells in the crista
What is the range for visible light?
400 - 750nm
What is the cornea?
Transparent layer that protects the eye, involved in focusing and refracting light
What is the iris/ pupil?
A muscle that constricts and relaxes to regulate the diameter of the pupil. The pupil shrinks/ expands to match changing light conditions
What is the lens?
A transparent tissue, made of tightly packed crystallin proteins, attached to the ciliary muscle and enables fine focusing of light
What is the aqueous humour, where is it found?
What is the vitreous humour, where is it found?
Low protein plasma like fluid found in the front eye chamber
Clear gelatinous substance, keeps the retina in place, found in the main eye chamber
Does the eye use a concave or convex lens?
Convex
What is the retina?
Covers the inside of the eyeball, contains cells sensitive to light
Describe rods and cones.
Rods - most common (in mammals), sensitive to light so can work at low light intensities
Cones - three types, red blue and green
What happens when 11-cis-retinal is hit by light?
It photoisomersises to the all trans retinal form which no longer fits in the opsin protein. Causing the protein to change conformation triggering a phototransduction cascade in the photoreceptor cell
Describe the phototransduction cascade.
Photon hits causing 11-cis-retinal to be converted to all trans form
Causes a conformation change which activates transducin
Transducin activates a cGMP phosphodiesterase
This breaks down cCGP
A reduction in cGMP causes cGMP sensitive ion channels to close hyperpolarising the photoreceptors membrane
How to photoreceptors respond to stimulation?
They hyperopolarise
Where do ganglion cells project?
What are they involved in?
Superchiasmatic nucleus - main site of circadian clock
Oilvary pretectal nucleus - involved in pupil reflex
Can do everything but conscious vision (don’t project to visual cortex)
What ligands stimulate gastric acid secretion in the GI tract?
ACh
Histamine
Gastrin
Describe the three areas of the stomach.
Fundus - least innovated, least muscular, food stored here when you swallow
Corpus - most secretion occurs here, filled with glands, well innovated - pace maker zone in stomach contractions begins here
Antrum - undergoes most contractions, point is reduction of size of food to fit through small aperture
What are the four parts of the GI tract?
Mucosa - epithelium, connective tissue (lamina propria), thin muscle layer, blood capilaries and branches of the lymphatic system
Glands
Mucosae
Submucosa
In the contraction of the GI tract what type of contraction do tonic muscles do? What type of contraction do phasic muscles do?
Sustain contractions e.g. Sphincters
Cycle of contraction and reaction
How many litres of liquid pass through the GI tract every day?
9L
What are the three phases of secretion in the gut?
Cephalic phase - receptors in the head stimulated by thought, sight, smell, taste of food, involves parasympathetic nervous system (vagus nerve), feed forward mechanism readies physiological processes e.g. Pavlov’s dogs
Gastric phase - secretion of acid, pepsinogen and intrinsic factor, produce mucus bicarbonate layer,
Intestinal phase - food in intestine, more bicarbonate secretion, inhibition of gastric acid, production of pancreatic fluid
Describe the production of bile acid?
Continually produced
Stimulated by gut endocrine system
Gall bladder releases concentrated bile straight into gut
Contraction also stimulates liver to produce more bile
Once used 90 - 95% re absorbed by ileum, taken up again by liver
~5% enters colon, bacteria convert to secondary bile salt (can be absorbed or lost to faeces
Recycling happens around 10 times a day
What are the methods of sodium transport?
Coupled transport: Na/ glucose of Na/amino acid cotransporters
Sodium proton exchanger: Na-H exchanger
Parallel Na-H and Cl-HCO3 exchangers, exchange sodium for a bicarbonate, takes out last sodium in faecal stream, very efficient
Epithelial Na channel
What happens to potassium in the small and large intestine?
The small intestine absorbs potassium, the large secretes it.
The gut acts as a regulator of potassium balance.
What are the two mechanisms of potassium secretion in the gut?
Passive, moves with water
Active secretion, involves sodium
What effect does Aldosterone have on potassium and sodium levels and how does it do this?
Increases sodium absorption
Enhances potassium loss from body by increasing activity of sodium potassium pump, and increases activity of apical potassium channel
What is secretory diarrhoea?
What is osmatic diarrhoea?
Caused by a bacteria or toxin e.g. Cholera causes semi permanent opening of chloride channels, leaks chloride into the lumen, causing loss of water and sodium. Fasting doesn’t stop the diarrhoea like food poisoning does.
Presence of un digested food, if foods (carbs) arnt absorbed the carbs change the osmolality of gut lumen, higher in lumen than gut so water moves to gut. Common result of lactose intolerance, reduced with fasting
Describe the functions of the liver.
Secretes bile - essential for the absorption/ digestion of fats
Detoxification - waste metabolic products are rendered into secretable form by liver, many waste products aren’t soluble, liver makes them soluble to be secreted in urine and faeces
Protein metabolism - converts ammonia to urea to get rid of it, also synthesises plasma proteins (albumin), globulins, fibrinogen and prothrombin
Red blood cell turnover - destruction and formation of RBC (breakdown of pigments in haemoglobin)
Storage organ - e.g. Glycogen, fat, vitamins (A, B12, and D), key store for iron, synthesis of vitamin K (important for coagulation pathway)
Regulates metabolism - of carbs, major store of glycogen which is broken down when blood sugar gets low
Lipid metabolism - re absorbs cholestrol
What happens in the liver if pressure in venous circulation rises?
Fluid will not drain, as there will be no pressure gradient, stasis of blood occurs, leaks out and gets stuck in body cavity where liver sits, accumulation of fluid in abdomen, causes cirrhosis (scaring of liver) and pressure rise in vein
What is secretin?
A hormone produced by the duodenum when acidic chime enters it, secretin activates liver to increase bile manufacturing
What percentage of bile salts are made in the liver, what percentage are re-circulated?
Where in the GI tract are bile salts absorbed?
Liver can only make ~5% of bile salts, 95% need to be re-circulated
Terminal ileum
What is Jaundice?
What are the three possible causes?
How can you tell if bilirubin is pre or post hepatic?
Accumulation of bilirubin, yellowing of skin and eyes
Pre hepatic - too much RBC destruction, e.g. Malaria, sickle cell anemia
Intra-hepatic - infection in liver, cannot process bilirubin properly
Post-hepatic - gallstone blocks biliary system
Whether the bilirubin is conjugated or not (has or hans’t been through the liver) tells you whether it’s pre or post hepatic
Where does the bile duct empty into?
Duodenum
What are the two blood supplies into the liver?
What is the purpose of the hepatic portal vein?
Arterial supply from the hepatic artery
Venous supply from the hepatic portal vein
Drains the GI-tract and delivers absorbed nutrients directly to the liver
What are Kupffer cells (found in the liver)?
Macrophages found in sinusoids
What are bile salts derived from?
What do they do?
What is the main bile pigment?
What is conjugation?
Cholesterol
Emulsify fat droplets in the duodenum, facilitate fat and cholesterol absorption, solubilise cholestrol
Bilirubin
Process where bile salts combine with another molecule (e.g. Glycine or taurine) which makes them more soluble in aqueous solutions as they are more readily ionised
What stimulates the release of cholecystokinin from pancreatic acinar cells?
Mix of small peptides and amino acids sensed in the duodenum
What are the three phases of protein digestion by enzymes?
Luminal - release of peptidases from pancreas
Membrane - amino peptidases embedded
Cytoplasmic - peptidases within cell itself
What is the enzyme that cleaves trypsinogen to trypsin?
Enterokinase
How do endo and exopeptidases work in protein digestion?
Endopeptidases digest internal peptide bonds
Exopeptidases digest terminal peptide bonds to release amino acids (two types amino peptidases and carboxypeptidases)
What are the three transport mechanisms for peptides?
Di and tripeptides co-transport with H+
Amino acids co-transport with Na+
Small peptides are carried intact across the cell by transcyrosis
After pancreatic lipase digestion what four products are you left with?
MAG (monoacylglycerol)
Cholesterol
Lysolecithin
Fatty acid
What are the 10 steps of lipid digestion?
- Action of lingual and gastric lipase liberates LCFS
- LCFA stimulates bile release and pancreatic lipase secretion
- Bile emulsifies fat droplets in SI lumen
- Mixed micelles formed
- Micelles disintergrate at luminal surface, releasing digestion products for absorption
- Lipid absorption through diffusion, collision or carrier proteins
- Translocate to smooth ER
- Reassembled back into lipid on cytosolic surface
- ApoB48 from rough ER added by MTP
- Migrate through Golgi before leaving basolateral surface and entering lacteal
In endocrinology what are the three main groups of hormones?
Amino acid derivatives: tryptophan, tyrosine
Peptides: TRH, growth hormone
Steroids
Where do endocrine glands secrete to?
Where do exocrine glands secrete to?
Directly into the blood
Onto an epithelial surface (usually via a duct)
What is the only hormone to have both stimulatory and inhibitory regulation from the pituitary?
Growth hormone
What effect does dopamine have when released from the hypothalamus?
What type of hormone structure does dopamine have?
Targets the lactotroph in the pituitary, inhibits prolactin release
Monoamine
Where are hypothalamic factors released into?
What does the pituitary portal system do?
Name the posterior pituitary hormones.
A highly vascularised region called the median eminence
Transfers releasing and inhibitory hormones from hypothalamus to anterior pituitary
Oxytocin and vasopressin
Describe the synthesis of amine hormones?
Describe the synthesis of steroid hormones?
Describe the synthesis of peptide hormones?
Adrenal amines - synthesised from tyrosine, sorted in vesicles
Thyroid amines - larger, synthesised in two step pathway
Cholesterol starting point, steroid hormones stored not as hormone but as lipids, when cell stimulated, steroid synthesised and released, of through post translational modification (broken into smaller sub peptides or dimerised)
DNA transcribed in nucleus into mRNA, mRNA interacts with rough ER, recursor peptide synthesised, packaged in Golgi, stored in secretory vesicles in cytoplasm similar to amine hormones
What type of hormones use membrane bound receptors?
What type of hormones use intra cellular receptors?
Hydrophilic peptide and amine hormones, cause a rapid response
Steroids and thyroid hormones, slow response, stimulate gene expression
What part of the thyroid gland secretes thyroxine (T4) and tri-idothyronine (T3)?
What is in the central cavity of the thyroid?
Where are the C cells in the thyroid and what do they secrete
The epithelial outer layer (follicular cells)
Filled with colloid.
Present in basement membrane and between follicles. Secretes calcitonin .
What are the two molecules required for the synthesis of thyroid hormones (T3 and T4)?
Thyroglobulin and iodine
What is an example of a disease that causes hyperthyroidism?
What is an example of a disease that causes hypothyroidism?
Grave’s disease - an autoimmune disease where antibodies activate the TSH receptor
Iodine deficiency
Hashimoto’s disease - autoimmune thyroid destruction
Myxedema
What is the enzyme that converts T4 to T3?
Deiodinase 2
What makes up 75% of the adrenal gland?
What are the three subunits of the cortex?
The cortex
Zona glomerulosa (10%), zona fasciculata (75%), zona reticularis (15%)
What is the main role of mineralocorticoids?
What are the three tissues glucocorticoids act on?
Increase blood pressure
White adipose, liver and skeletal muscle
What are some disorders of cortisol secretion?
Cushing’s syndrome - hyper-secretion
Addison’s disease - hypo-secretion
What does stimulation of the zona reticularis by ACTH cause?
The production of pre-androgens which are converted to testier one in target tissues
What is the main cell type in the adrenal medulla?
Chromffin cell, which produce either adrenaline or nor-adrenaline
What are the three types of cell in the islets of langerhans? What do they secrete?
Alpha - glucagon
Beta - insulin
Delta - somatostatin
What is the precursor for calcitriol?
What does calcitriol do?
What effect does calcium have on parathyroid glands?
What are the physiological roles of PTH?
Vitamin D
Increase intestinal absorption of calcium - increasing the plasma calcium
Low calcium stimulates chief cells, high calcium inhibits them
Increase plasma calcium
What stimulates the release of GHRH from the hypothalamus?
What inhibits and stimulates the release of GH from the pituitary gland?
What is IGF-1 important for?
What are the direct and indirect effects of GH?
What is it called when you get hyper-secretion of growth hormone as a adult?
Sleep, exercise and stress
Somatostatin and GHRH
Antagonises insulin, synergies with cortisol, causes local production of IGF-1
Stimulates production of IGF-1 from the pituitary
GH negative feedback and is a mediator of GH’s negative effects
Acromegaly
What makes up seminiferous tubules in the tetstes?
Where are Leydig cells found?
Where does somatogenesis occur?
What effect does FSH have on spermatogenesis?
What effect does testosterone have on spermatogenesis?
What inhibits FSH?
Sertoli cells
Between tubules
Sertoil cell layer
Affects Sertoli cells, initiates spermatogenesis, and production of ABP and inhibin (which inhibits FSH)
Affects Leydig cells, stimulates production of testosterone, required for maintinance of spermatogenesis (via androgen binding protein)
What causes the anticipatory rise in ventilatory volume in response to exercise?
What is EPOC?
What is the Fick principle, what does it show?
What is the equation for cardiac output?
What is VO2max? What factors influence it?
What is the main limit in factor in athlete performance, O2 delivery or utilisation?
When does the lactate threshold occur?
The action of catecholamines (adrenaline and noradrenaline) on the respiratory centre in the brain
Exercise post oxygen consumption (oxygen debt)
VO2 = cardiac output X (arterial - venous)O2 difference
Demonstrates relationship between metabolism and cardiorespiratory function
Cardiac output = heart rate X stroke volume
Max volume of oxygen consumed by the body each minuet during exercise at sea level
Pulmonary diffusory capacity, capilarisation, muscle fibre type, cardiac output, oxygen carrying capacity/ amount of RBC
O2 delivery - stroke volume is the main limiting factor
When lactate production > lactate removal determined by oxidative capacity of skeletal muscle
How does exercise reduce postparandial triglyceride concentration?
By two complimentary mechanisms: increases activation of lipoprotein lipase in the skeletal muscle so increased triglyceride clearance, reduced hepatic VLDL secretion
In mammals where is the master circadian clock?
What entrains (synchronises) biological rhythms to the external environment?
In the suprachiasmatic nucleus of the hypothalamus
Zeitgebers (e.g. Light)
Where is the pineal gland?
What is the main cell type of the pineal gland?
What is the major source in the body of melatonin?
What is melatonin synthesised from? What is the key rate limiting enzyme in melatonin biosynthesis?
Near the thalamus, part of the epithalamus in the diencephalon
Pinealocytes
Pineal gland
Tryptophan
AA-NAT
