PHYL2066 (All modules)

Nucleus

• Control centre for the cell - control protein synthesis

• Contains DNA

• Surrounded by nuclear envelope

Ribosomes

Needed for protein synthesis

Free ribosomes

• Suspended in cytosol

• Synthesises proteins that function in the cytosol

Bound ribosomes

• Bound to ER

• Synthesises proteins which function in the membrane, within organelles or outside of the cell

Cytoplasm

Area in the cell which is not the nucleus

• Contains cytosol, organelles and cytoskeleton

ER

Network of membranes joining the nucleus

Two parts:

• Rough ER

• Smooth ER

Rough ER

• Covered in “rough” ribosomes

• Where proteins are made - membrane factory

Smooth ER

• Packages proteins and transports them to the Golgi complex in vesicles

• Has specialised functions in particular cells

Golgi complex

Sorting facility of the cell

• accepts vesicles and sorts all of the proteins in them and then sends them out to where they need to go

Lysosomes & Peroxisomes

Waste facility

Vesicles containing enzymes

Lysosomes - break down organic material inside the cell

Peroxisomes - break down toxic molecules inside the cell

Enzymes

Molecules that speed up chemical reactions without getting consumed by the reaction.

Mitochondria

Powerhouse of the cell - converts food energy into cellular energy

Plasma membrane (4 traits)

1. Forms a mechanical barrier

2. Selective permeability - lipid bilayer (hydrophobic core)

3. Electrochemical gradient

4. Communication & cell signalling

Types of cell junctions (3)

1. Desmosomes - cells joined together without actually touching - epithelial cells - means everything isn’t constantly tearing

2. Tight - sewn together cells - impermeable barrier - digestive system cells

3. Gap - tunnels from one cell to another - permeable - cardiac cells

Negative feedback loop

Brining our body back to homeostasis

Example is temperature regulation

Positive feedback loop

Allows the body to operate outside the homeostatic range

Amplification effect

Example childbirth

Which molecules can pass across the membrane?

Gases and Water and Ethanol

Diffusion

Movement of molecules from an area of high concentration to an area of low concentration

What controls diffusion rate? (5)

1. Size of concentration gradient

2. Membrane surface area

3. Size of molecule

4. Diffusion distance

5. Lipid solubility of the molecule

Osmosis

Movement of water from an area of high water concentration to an area of low water concentration

OR

Movement of water from an area of low solute concentration to an area of high solute concentration

What is the unit for measuring osmolarity?

Osmolarity - number of solute particles per litre of solution

Milliosmoles/litre (mOsm/L)

Types of tonicity (3)

Isotonic - same concentration of non penetrating solutes as the ICF

Hypertonic - higher concentration than ICF

Hypotonic - lower concentration than ICF

Isotonic Solution

No net movement of water

Hypertonic Solution

Movement of water out of the cell to dilute the non penetrating solutes in the solution - cell shrinks

Hypotonic Solution

Movement of water into the cell - cell swells

Facilitated diffusion - no ATP

Happens via channels or carriers

Channels - either open or gated (chemical or voltage activated)

Carriers - changes shape to transport solutes across the membrane

Diffusion

Moving molecules down the concentration gradient

Active transport

Moving molecules against the concentration gradient

Requires ATP

Two types:

Primary Active Transport and Secondary Active Transport

PAT

Terminal phosphate in ATP is given to carrier. This causes the carrier to change shape

Example - sodium-potassium pump

SAT

Two solutes transported together in the same or opposite direction. One goes against the cg and one goes down the cg. Only possible because of PAT creating cg therefore indirectly using ATP.

Endocytosis types (3)

1. Receptor mediated endocytosis

2. Pinocytosis

3. Phagocytosis

Exocytosis

Vesicles fuse to the plasma membrane and release their contents to the outside of the cell

Graded Potentials (3)

1. Depolarisation - becomes closer to 0

2. Repolarisation - returning to resting potential

3. Hyper polarisation - becomes further from 0 = less potential

Action potential

Brief reversal of membrane potential (reaching +30mV)

Occurs only in muscle cells and axons of neurons

Voltage-gated channels

Have two gates - activation gate which opens when voltage is reached - deactivation gate which snaps shut when voltage threshold is reached

OR

Has one gate - only activation gate - slow to close

Myelination

Makes signalling faster

Thick filament components

1. Tail

2. Two heads - one which binds to actin and one which binds to ATP

3. Made up of myosin

Thin filament components

1. Actin - spherical molecules which are active sites for myosin - forms chains

2. Tropomyosin - rope like proteins which block myosin binding site when muscle is relaxed

3. Troponin - binds to actin and tropomyosin to stabilise thin filament - has calcium binding site

Sarcoplasmic reticulum

The smooth ER of muscle fibres

• Surrounds each myofibril like a mesh sleeve

• Stores calcium which is released during contraction (triggers the whole thing)

T-tubules

Part of the sarcolemma that runs between the SR. This is where the AP’s run down to get to the myofibrils

Motor unit

One motor neuron and all the fibres it innervates

One motor neuron will innervate many muscle fibres and one muscle fibre will be innervated by many motor neurons

Single versus multi-unit smooth muscle

Single:

Self-excitable

Visceral muscle

No motor units

Linked by gap junctions to function as a single unit

Calcium variations determine tension

Multi-unit

Neurogenic

Involuntary autonomic nervous system

Has motor units

Receptor types (6)

1. Mechanoreceptors

2. Thermoreceptors

3. Nociceptors

4. Chemoreceptors

5. Osmoreceptors

6. Photoreceptors

What do the receptors tell the brain? (4)

1. Modality

2. Intensity

3. Location

4. Timing

How do we identify modality?

Labelled lines

Identifying intensity

1. Frequency of AP’s

2. Number of receptors activated

Identifying stimulus location

1. Which neuron receptor field is stimulated

2. Where was that stimulation on the homunculus

Receptor adaptation

Tonic receptors - adapt slowly or not at all - pain

Physic receptors - adapt quickly - pressure

Cutaneous nociceptors

1. High threshold - sharp pain

2. Polymodal - burning pain

Types of extracellular messengers - secretory to target cell

1. Paracrines - local effect - only effect neighbouring cells

2. Neurotransmitters - local effect

3. Hormones - long distance

4. Neurhormones - long distance

What do we use ATP for? (3)

1. Mechanical work

2. Moving molecules across the membrane

3. Synthesis of new compounds

Possible synaptic drug interactions (4)

1. Alter synthesis, atonal transport storage or release of a neurotransmitter

2. Influence neurotransmitter re-uptake or destruction

3. Modify neurotransmitter interaction with the receptor

4. Replace a neurotransmitter

Functions of the cardiovascular system (4)

1. Transports O2 and nutrients to the cells

2. Removes waste products from the body (CO2)

3. Transports hormones

4. Helps maintain body temperature

Cardiac muscle cell features (5)

99% contractile muscle cells -1% autorhythmic

Striated

Desmosomes and gap junctions

Have intercalated discs between cells

Cardiac cells contract simultaneously

Spread of excitation through the heart must meet 3 criteria

1. Each chamber must pump as a unit

2. Atria should contract together and ventricles should contract together

3. Atrial excitation and contraction must complete before ventricular contraction

Systole

Contraction of the heart

Diastole

Relaxation of the heart

Heart sounds (2)

1st sound - the closure of the AV value - the beginning of systole

2nd sound - closure of semilunar valves - ventricular diastole

Cardiac output

Volume of blood pumped by each ventricle per minute

CO = heart rate (beats/minute) x stroke volume (ml/beat)

CO = MAP/TPR

PNS is dominant in resting individuals

True

Stroke volume

The amount of blood pumped out of the ventricle during contraction

SV = End diastolic volume - End systolic volume

What increases stroke volume (2)

SNS activity - increases heart rate

Venous return - more blood to pump because EDV is increased

Sympathetic stimulation enhances the contractile strength of the heart

True

Increasing venous return makes the next contraction stronger

True - because venous return causes heart muscle to stretch and as it stretches it will have more potential for next time. Cardiac muscle is normally operating slightly more tight than possible so when needed it can contract harder.

Factors influencing venous return (5)

1. Cardiac suction

2. Skeletal muscle pump

3. Venous valves

4. Respiratory pump

5. Sympathetic nervous system

Cardiac suction

Heart acting as a suction pump

When ventricles contract the AV valves are drawn downward which decreases the pressure in the atria, this means the pressure in the veins is higher and blood will move from high to low pressure. The same thing happens when the ventricles relax and the pressure decreases, the blood will be sucked from the veins and the atria to the ventricles.

Sympathetic stimulation

Increases venous return → Increases EDV → Increases stroke volume → Increases cardiac output

Korotkoff sounds

Sounds that can only be heard when blood is moving turbulently. Smooth flowing blood is silent.

Pulse pressure

Difference between systolic and diastolic pressure

Mean arterial pressure

Average blood pressure in the arteries. Closer to diastole because heart spends longer in diastole.

MAP = DP + 1/3 of PP

MAP = CO x TPR

What influences blood flow (2)

1. Cardiac output

2. Resistance to blood flow (vessel diameter)

What influences resistance

1. Blood viscosity

2. Vessel length

3. Vessel radius

Total peripheral resistance

Sum of all resistances in the circulatory system

Calculating the pressure gradient in the entire circulatory system

Pressure in arteries - the pressure in veins

MAP - Central venous pressure

Because CVP is close to zero, circulatory pressure gradient = MAP

What percentage of the capillaries are normally open at once

25%

What features make capillaries good for diffusion (3)

1. Small diffusion distance

2. Large surface area

3. Slow blood flow - extra time

Filtration

Pushing fluid out of capillary

Reabsorption

Drawing fluid back into capillary

Bulk flow

Continuous flow of fluid and solutes between capillaries and interstitial fluid

Forces driving bulk flow (2)

1. Hydrostatic pressure - blood pressure in capillaries and pressure of blood coming into the capillaries. Pressure will be higher at arteriolar end than venular end

2. Osmotic pressure - plasma proteins too large to exit capillary, osmosis draws fluid back into capillary

Net filtration pressure

Difference between capillary hydrostatic pressure and osmotic pressure. Positive NFP favours filtration, negative favours reabsoprtion.

Cardiovascular control centre

In the medulla oblongata - receives info from baroreceptors and regulates ANS activity to heart and vessels

Baroreceptors

Mechanoreceptors than respond to stretch. Located in carotid sinuses (monitor blood flow to brain) and aortic arch (monitor blood flow to systemic circulation)

Respiratory system functions (4)

1. Speech

2. Smell

3. Maintains pH of the blood - don’t really need to know details

4. Enhances venous return - when inhaling

Ventilation

The process of breathing, not just including the respiratory system but also the cardiovascular

Cells of the alveoli

Type 1 - squamous cells lining the alveoli

Type 2 - Produce surfactant

Alveolar macrophages - needed as lungs are an important barrier from our external environment to our internal environment

What optimises gas exchange

1. Short diffusion distance

2. Large surface area

Atmospheric Pressure

Pressure exerted by weight on air on objects on earths surface

Decreases with height from sea level

Sea level = 760mm Hg

Intra-alveolar pressure

Pressure inside lungs

Linked to atmospheric pressure through conducting airways - they quickly become the same

760mm Hg

Intrapleural pressure

Pressure inside pleural sac

Less than atmospheric pressure

756mm Hg (sometimes expressed as -4mm Hg)

Transmural pressure gradient

Difference in pressure across chest wall. Pressure difference between lungs and pleural cavity. Pushes the lungs out towards the thoracic wall.

Forced breathing

During exercise or disease - requires extra muscles

Forced inspiration - uses accessory muscles in neck and works against elastic recoil

Forced expiration - uses internal intercostals and abdominal muscles to work with elastic recoil

Physical factors influencing ventilation (4)

1. Airway resistance

2. Alveolar surface tension

3. Lung compliance

4. Elastic recoil

Airway resistance

Airflow rate (F) depends on the air pressure gradient (difference between AP and IAP) and airway resistance.

F = APG/R

Airway resistance is very low in healthy individuals

Increased resistance = slower airflow - this is mainly caused by reduced bronchioles radius from bronchoconstriction, mucous or fluid (like in asthma)

Lung compliance

Stretchability of the lungs during inspiration. High compliance - good stretch, low compliance - hard to stretch

Factors reducing lung compliance

High surface tension (reduced surfactant)

Scarring of lung tissue

Restrictive diseases

Elastic recoil

Ability of lungs to rebound and shrink

What influences elastic recoil (3)

1. Elastic fibres

2. Surface tension

3. Emphysema

Poor elastic recoil makes it hard to push air out

Tidal volume

Air inspired or expired during quiet breathing

Inspirations reserve volume

Extra air inspired during forced inspiration

Expiration reserve volume

Extra air expired during forced expiration

Residual volume

Air left in the lungs after forced expiration - this is left so the alveoli don’t collapse