Cardiovascular

Question 1

Contractile myocardial cells

Answer 1

arranged in layer, connected by INTERCALATED DISCs, which contain GAP JUNCTIONS. These form the bulk of the atria and ventricles.
contain lots of actin and myosin, striated appearance.

Question 2

Nodal tissue

Answer 2

1% of cardiac cells
small round cells with no or little contractile protein.
specialized for the GENERATION and CONDUCTION of ACTION POTENTIALS in the atria
contain gap junctions.

Question 3

Pacemaker cells

Answer 3

Pk gradually reduces, permeability to sodium and calcium causes increase in pacemaker potential.
at threshold voltage, calcium channels open and slow AP occurs.
Na+ enters
Ca2+(temporary) enters
Ca2+(long channels), enters
K+exits

Question 4

Ventricular cells

Answer 4

Pk is higher so lower RMP, depolarisation is due to opening of voltage-gated Na+ channels opening;
Na+ enters
Ca2+(long channels) enters
K+ exits.

Question 5

ECG waves

Answer 5

p wave; atrial depolarisation
qrs wave; ventricular depolarisation
T; ventricular repolarisation.

Question 6

Cardiac cycle stages

Answer 6

Isovolumetric relaxation
ventricular filling
isovolumetric contraction
ventricular ejection

Question 7

Preload

Answer 7

How much blood is in the ventricle after diastole. more preload = longer sarcomere length.
frank starling; more preload means more force required to empty ventricle

Question 8

Afterload

Answer 8

the tension the fibres must generate before they can shorted - the pressure required to open valves.
dependent on MABP

Question 9

law of laplace

Answer 9

Pxr
T = ——-
2xu

Question 10

Intrinsic heart control:

Answer 10

preload & afterload
very limited role in contraction; higher MABP causes slightly faster AP generation

Question 11

extrinsic heart control mechanisms

Answer 11

nervous and endocrine, major controls.
tonic signaling to heart
- parasympathetic signaling decreases HR
- sympathetic signaling increases HR

Question 12

Blood vessel flow and control

Answer 12

from most impact to least impact;
- myogenic regulation
- endothelial secretions, vasoactive metabolistes and autacoids,
- extrinsic factors.

Question 13

MABP

Answer 13

arterial baroreceptors
- receptors on aortic & carotid sinus
–> afferent fibers in vagus and glossopharyngeal nerves
–>CNS brainstem centres
–> tonically active, more activity = more pressure

carotid and aortic chemoreceptors
- CO2 concentration

cardiopulmonary baroreceptors

central chemoreceptors

Question 14

explain foetal circulation

Answer 14

check the book you lazy fuck.

Question 15

Pulmonary blood flow regulation

Answer 15

1. gravity
2. hypoxia
3. endothelial control
4. sympathetic nervous system