Option D.2 Flashcards
outline the structure of heart tissue
cardiac muscle cells contract without stimulation by nervous system, so contraction is myogenic
It has:
branched cells aloow faster signal porpagation and contraction in 3 dimensions
connected by gap junctions called intercalated dics: helps increase blood flow and improves contraction
have many mitochondria, as they are more reliant on aerobic repsiration than skeletal muscle.
outline how the heart contracts and how that is seen on an ECG
the sinoartiral node (SA) acts as a primary pacemaker, controlling the rate of the heartbeat
- sends action potential through gap junctions to the left and right artrial walls.
- artial walls contracts, causes P wave in ECG
- AV nodes receives signal from SA node and delays it by 0.1 seconds
- sends depolarisation signal to bottom of left and right ventricles via bundles of His in the hearts septum, and then through the purkinje fibres (causes contraczion and QRS spike in ECG).
- ventricals repolarise causing T wave in ECG
what do the sounds lub and dub mean
lub: closing of AV valves at the beginning of ventrcular contraction (systole)
dub: closing of semilunar valves at the beginning of diastole
what is thrombosis
formation of a clot within a blood vessel which can be caused by cholesterol build up in vessels.
this decreases the diameter of the lumen, which increases the pressure leading to hypertension in arteries
can lead to strokes, blindness, arteriosclerosis (hardening of arteries)
- a plaque is formed when cholesterol build up on scar tissue, it makes platelets release factors that cause the formation of a clot over the plaque, forming a thrombus.
this blocks the flow of blood causing thrombosis. can cause a heart attck if it occurs in coronary artery.
what do artificial pacemakers and defibrillators do?
pacemakers: set up in body to send artificial electrical signals to heart, when a person has a irregular heartbeat
defribrillation: heart stops beating, place machine so that it aligns with the heart which sends electrical signals. goal is to shock the heart into a normal rythm that the SA node takes over.
what are endocrine glans and the endocrine system?
endocrime glands secrete their hormones directly into bloodstream rather than through a duct. ex: ovaries (progesterone and estrogen to uterus) and testes (testosterone to many diff organs)
endocrine system is slower to initiate but has a prolonged effect when compared to nervous system
what are steroid hormones
lipophilic (fat-loving) they can freely diffuse across the plasma membrane of a cell
bind to receptors in either the cytoplasm or nucleus of the target cell, to form an active receptor-hormone complex
This activated complex will move into the nucleus and bind directly to DNA, acting as a transcription factor for gene expression
Ex. estrogen, progesterone and testosterone
what are peptide hormones
hydrophylic + lipophobic (fat-hating) – meaning they cannot freely cross the plasma membrane
bind to receptors on the surface of the cell, which are typically coupled to internally anchored proteins (e.g. G proteins)
The receptor complex activates a series of intracellular molecules called second messengers, which initiate cell activity
This process is called signal transduction, because the external signal (hormone) is transduced via internal intermediaries
Examples of second messengers include cyclic AMP (cAMP), calcium ions (Ca2+), nitric oxide (NO) and protein kinases
The use of second messengers enables the amplification of the initial signal (as more molecules are activated)
Peptide hormones include insulin, glucagon, leptin, ADH and oxytocin
what is the hypothalamus and outline its role
section of the brain that links nervous and endocrine system to maintain homeostasis
-receives infro from nerves and initiates endocrine responses
Piturary Gland
lies adjacent to hypothalamus and is in contact due to portal blood syszem, consistis of two lobes:
Anterior Lobe
- hypothalamus secrectes neurochemicals, releasing factors, into portal vessels which target anterior lobe, and causes endocrine cells to release specific hormones in blood stream
Posterior Lobe
- hypothalamus secretes hormones directly into blood via neurosecretory cells that extend into posterior pituray lobe and releaase the hormones into the blood
oultine the process of lactation
controlled by two hormones: oxtocin and prolactin
Prolactin repsonsible for dev. of mammary glands and production of milk
secreted by the anterior pituitary in response to the release of PRH (prolactin releasing hormone) from the hypothalamus
The effects of prolactin are inhibited by progesterone, which prevents milk production from occurring prior to birth
oxytocin is for the release of milk from mammary glands
posterior pituitary
triggered by stimulation of sensory receptors in the breast tissue by the suckling infant
creates a positive feedback loop that will result in continuous oxytocin secretion until the infant stops feeding
what does a iodine defiency do?
affects thyroid gland, where thyroxin is produced (contains iodine in its chemical structure so cannot be produced if defiecent)
outline the affect of growth hormone
an anabolic peptide hormone that stimulates growth
It acts directly to reduce the formation of adipose cells (i.e. less nutrients stored as fat)
It acts indirectly via insulin growth factor (IGF) – produced by the liver – to increase muscle mass and bone size
how is CO2 transported in the blood
simply dissoved (not much of it)
bound to plasma proteins
as bicarbonate ions dissolved in plasma, which is more soluble and less toxic
what is the oxygen dissociation curve and explain it
shows the saturation of hemeglobin with oxygen in blood (how much of O2 is bound with hemeglobin)
partial pressue of oxygen: just the concentration of O2 in blood
the curve is a sigmoid curve- and S shaped curve
-first O difficult to lead onto Hb
- loading of first O chnages shape slightly of HB and makes it easier for second and third O to load
- fourth O also struggles relsulting in the plateau of the curve
what is the bohr shift on the oxygen dissociation curve
- during excercise more O2 is required for respiration, meaning more CO2 is produced
- more CO2 is released in blood, which reduces the ph
- increase in CO2 causes the affinity (tendency of O2 to bind to HB ) for O2 to decrease
- causes oxygen to be given up more readily by HB
on the graph, the bohr shift moves the curve to the right.
curve changes when increased CO2, increased acidity, and increased ventillation rate
