Lecture 1 Flashcards
What is pericardius
Swollen bit on heart that puts pressure on it, need a pericardecromy which is removal of the sac
Features of the heart
Pumps blood one way
Leakproof
Regular and automatic
Able to chance output when required
Where is the heart located ?
In mediastinum ( between 2 lungs ) and in the Thoracic Cavity in rib cage . 5th intercostal space of ribs = apex (bottom of the heart) 3rd = base
Diaphragm function
Between chest and ribs, expands to push chest up and down
What are the two systems pumping blood
Pulmonary circulation ( carry’s Blood low in oxygen to lungs then to heart)
Systemic Circulation (oxygen rich blood to body )
Heart structure from right side top to bottom
Superior vena cava (blood from body to heart)
Right pulmonary artery ( blood to right lung)
Right pulmonary veins ( blood back from lungs to heart )
Right atrium ( top chamber of heart)
Inferior vena cava (blood from lower body to heart)
Right ventricle (lower chamber of heart)
Heart structure from left side top to bottom
Aorta (carries blood to body)
Left pulmonary artery (blood to left lung)
Left pulmonary veins (back from left lung)
Left atrium (top chamber)
Left ventricle (bottom chamber)
What is the circulation of blood (deoxygenated blood to oxygenated blood)
Low 02 blood enters the vena cave from body then leaves the R AND L pulmonary arteries to lungs.
High 02 blood enters the R AND L pulmonary veins from lungs and leaves through the aorta to body.
What are the layers of tissue in the heart
- Pericardial sac
- parietal pericardium
- pericardial cavity
- epicardium
- myocardium
- endocardium ;
- loose connective tissue
- squamous epithelium
What is pericardial cavity filled with and what function
Pericardial fluid and reduces friction as the heart beats
What is the sac called where the heart is contained
Pericardial sac (made of collagen fibres)
What lines the pericardial sac and what is it made off
Outer parietal pericardium and inner visceral pericardium separates by the pericardial cavity
What is the fluid called in the pericardial cavity
Pericardial fluid that acts as lubricant
What is the heart wall made of
Thick myocardium composed of cardiac muscle cells
Heart chambers lined by endocardium ( thin layer of AEOLAR connective tissue covered by SIMPLE SQUAMOUS epithelium )
What is the different between skeletal muscle cells and cardiac muscle cells
Cardiac muscle cells=
Short ( not long )
Branched ( allows link neighbour cells )
Single nucleus because short
Striated like skeletal
Involuntary control by the autonomic nervous system
What are intercalculated discs
Allow all cardiac cells to perform as one unit
What are the cells that physically join adjacent cells together
Desmosomes
What electrically links cells together in heart
GAP junctions
What is the conduction system in the heart
Sino-Atrial Node in the wall of right Atrium (“pacemaker”) passes signal onto Atrio-Ventricular Node passes to Atrio-Ventricular Bundle (between R and L ventricles) which branches in 2 down to apex then travels to Purkinje fibres which delivers signal to muscle cells in wall by diffusing up sides.
How does Sa node initiate signal?
Specialised cardiac muscle cells that can become spontaneously active without any outside influence, 75x per min approx
What are the valves in the heart?
-prevent back flow of blood Right tricuspid atrio -ventricular valve Right Semilunar valve Left bicuspid atrio ventricular valve Left semilunar valve
What is attached to left and right tricuspid and bicuspid valves
Chordae Tendinea (threads of connective tissue attach valve to Papillary muscles which contract to pull on tendons and o prevent back flow of blood Bi cuspid = 2 flaps of connective tissue Tri cuspid = 3
What are the two types of control of heart activity?
Intrinsic control and extrinsic control
I= hearts own in-built processes e.g. can control rhythm without outside factors
E= nervous system and endocrine system affect on heart activity
What is the main thing that controls the heart activity ?
Sino Atrial Node = specialised cardiac muscle cells at the back of the right atrium near superior vena cava which become spontaneously active (generate its own action potential)
What are the three ions involved in the cardiac muscle cell?
Na, K + and Ca2+
What are the three phases in SA action potential ?
Phase 4 then 0 then 3
Why is there no resting membrane potential?
Because pacemaker continually setting rhythm
What happens in phase 4
Na+ channels open @ -60mV = slow Na+ channels, Na moves down conc gradient from High outside to Low inside.
Slowly make inside of cell positive
“FUNNY CURRENT” - chnagein m potential
When reaches -50mV, Na channels close and Ca channels open ( T-type Ca2+ channel) making inside more positive.
What happens during phase 0?
Membrane potential reaches -40mV then L-type (longlasting) Ca2+ channels open and more Ca enters cell which causes m potential to rise to 20mV
RAPID INCREASE
What happens during phase 3 of SA action potential?
Ca channels close and K+ channels open, low conc outside cells so K+ leave cell and cell becomes negatively charged down to -60mV
How does SA node cause heart to beat after action potential?
Pass onto next cell - Cardiac muscle cell by GAP junction and causes it to contract
What stops signal from causing the atria and ventricles to contract at the same time
The fiberous skeleton is a wall of fiberous connective tissues that separates the atria and ventricles and is an insulating material. Stops the signal from spreading so has to go through the conduction system.
What is the difference between the cardiac muscle action potential and the SA action potential
CM action potential is much shorter than SA node action potential
What are the phases of the CM action potential ?
0, 1, 2, 3, 4
Phase 4 of Cardiac muscle action potential ?
Some K+ are open so K+ leaks out the cell, cell is still negative and at resting membrane potential -90mV
End of old cell signal and start of new cell signal
(Cardiac muscles are branched to transmission through GAP junctions will happen at number of points)
What happens during phase 0 of the cardiac muscle action potential?
- action potential from adjacent cell causes fast Na+ channels open and the inside becomes more positive until the membrane potential reaches -70mV (from -90mV), threshold then more Na+ channels open till +30mV
- ALSO @-40mV Long Lasting Ca2+ channels open and Ca enters then at PEAK Na+ channels close but Ca channels stay open
What happens during phase 1 of cardiac muscle cell action potential ?
Briefly K+ channels open up and lots of K+ on inside go outside cell and cell becomes more negative.
(Brief repolarisation)
What happens during phase 2 during cardiac muscle action potential?
Long lasting Ca2+ channels still open so positive charge going in cell.
K+ leakage through ungated K+ channels so cell becoming negative too.
This maintains membrane potential.
Plateau Pase
What happens during phase 3 of cardiac muscle action potential ?
Ca2+ channels close which allows K+ outflow to predominate out of cell
Membrane potential decreases to -90mV (resting membrane potential)
DEPOLARISATION
Back to phase 4
What is key difference between action potential of SA node and Cardiac muscle cell ?
SA node action potential is longer than CMC
