Biology Unt 1 (B3 Tissue structures and function)

What is an epithelial tissue?

• Covers all the surfaces of the body

• Lines all the tubes

• This group of tissues forms a protective barrier.

(They are found inside of the lungs)

What is a muscle tissue?

Allows body parts to move through contraction

What is a connective tissue?

Connective tissue supports, connects, and protects other tissues and organs.

What is a nervous tissue?

Nervous tissue transmits information throughout the body.

What are the 2 types of epithelial tissues?

Columnar and squamous 

What is the role of the ciliated epithelial cell? ( within the columnar epithelium)

Hair like structures on their cell membrane called cilia- moves mucus containing trapped pathogens away from the lungs.

found in trachea and bronchi

what is the role of the goblet cell? ( within the columnar epithelium)

• Produces a protein called mucin

• which traps pathogens that have been inhaled in. 

• found in trachea and bronchi

Where in the lungs are squamous epithelial tissues found?

Alveoli

What is the shape of squamous epithelial cells?

Flat and thin- often one cell thick

How are the gases in the alveoli wall adapted to travel into and out of the bloodstream?

• Large surface area- more surface available for the diffusion of o2 to occur

• Squamous epithelium (SEC) is one cell thick- short diffusion pathway as oxygen molecules have to pass through one thin SEC to get to capillaries

• Rich network of capillaries- keeps a strong oxygen gradient because oxygenated blood moves away and is replaced by deoxygenated blood.

Which factors increase the risk of developing chronic bronchitis?

smoking, silica dust and air pollution

what happens to the structures of the lungs when a person suffers from chronic bronchitis?

• Inflammation of bronchi and narrows airway

• increased number of mucus in the gland

• airway is obstructed by thick mucus

• makes it harder for air to move in and out of lungs, leading to coughing and breathing difficulties.

Emphysema is caused by smoking. Describe what happens to the alveoli when a person suffers from emphysema and give symptoms

• smoke damages cilia

• pathogens get trapped in the mucus

• macrophages move to lungs to kill bacteria

• macrophages release enzymes to breakdown alveoli

• surface area decreases and diffusion is slower

SYMPTOMS: easily tired, fatigue or breathlessness when exercising

Explain why a person suffering from emphysema may feel tired

• has a smaller surface area (lung tissue)

• reduction in oxygen uptake

• leads to more anaerobic respiration

Differences of epithelium and endothelium tissues

Epithelium- is a lining tissue that covers OUTSIDE surfaces

Endothelium- is a lining tissue that covers INSIDE surfaces

What is the role of the endothelium inside arteries and veins?

• Lines the inside of the blood vessels

• These cells are smooth and flat

• Which reduces resistance for blood flowing through them

Explain the role of the endothelium in blood capillaries

• capillaries are one cell thick

• this layer of single cells are endothelial cells

• thin to provide short diffusion pathways

Atherosclerosis- Explain the problems caused if cholesterol accumulates in the walls of the arteries

• causes an inflammatory response which gets bigger

• so narrows lumen of the artery

• and decreases blood flow through the lumen of the artery

These deposits are called plaque and fatty deposit

1. To try and help the body, what engulfs the cholesterol and what do they become

2. Explain how atheroma leads to blood clots

1. A type of phagocyte called macrophage which become foam cells

(2)

• Endo of artery gets damaged

• cholesterol is deposited behind endo + launches immune response

• macrophages engulf cholesterol + form foam cells

• This combination of macrophage and cholesterol forms a plaque

• lumen of artery gets narrow and increases BP more, atherome can burst

• causes blood clots as it stops the flow of blood and o2 to cells for respiration

• If this occurs in coronary artery, can lead to heart attack

Explain the risk factors that can lead to atherosclerosis/cardiovascular disease

Smoking (carbon monoxide and nicotine)- 

• carbon monoxide binds to haemoglobin and reduces o2 transport

• BP and heart rate increase, greater risk of damaged endothelium

• Nicotine increases platelets stickiness so higher risk of blood clots

Diet-

• Raises blood cholesterol levels

• more cholesterol available for macrophages to engulf, so more foam cells and plaque formation

• salt increases blood volume which raises BP 

High blood pressure-

• Increased BP damages the endothelium

• damage triggers an inflammatory response

• macrophages engulf cholesterol, forming foam cells 

• build up of plaque behind the endothelium

Describe the structure of the myelin sheath

• made up of schwann cells which wrap around the axon

• cell membrane is made up of mostly lipids

• lipids are electrical insulators

What is the purpose of myelin?

• myelin sheath acts as an insulator

• lipids prevents the loss of ions from motor neurones

• increases the speed of electrical impulse

The resting potential of neurones is -65mV. Explain what this means

• inside of axon is more negative that the outside

• creates negative resting potential of -65mV

• There are more positive ions outside the axon than inside

Explain how the resting potential is set up and maintained

1. The sodium–potassium pump moves 3 Na⁺ out of the neurone and 2 K⁺ in, using ATP.

2. This makes Na⁺ more concentrated outside the neurone.

3. It also makes K⁺ more concentrated inside the neurone.

4. K⁺ diffuses out through open potassium channels because of its concentration gradient.

5. Na⁺ channels remain closed, preventing Na⁺ from re-entering.

6. Because more positive ions leave than enter, the inside becomes negatively charged compared to the outside, producing the resting potential of about –65 mV.

Describe the events of the action potential

• Depolarisation Occurs & Na+ channels open, permeability to Na+ ion increases & enter axon by diffusion

• Threshold- increased membrane potential -70mV to -50mV and threshold reached (all or nothing law)

• Voltage-gated Na+ ion channels open & Na+ channels close at +30mV

• Action potential occurs

• Repolarisation occurs- K+ ion channel opens, permeability to K+ ion increases & leave axon by diffusion.

• Hyperpolarisation occurs at -90mV, reference to refractory period

What is the purpose of hyperpolarisation?

• prevents neurone from being re stimulated instantly

• The period of time when no new action potential can be generated is called the refractory period

• This is important as it helps ensure action potential travels in one direction down a neurone

What is the term for when the action potential jumps from node to node?

Saltatory conduction

How does saltatory conduction affect conduction and why?

• Schwann cells wrap around the axon to form a myelin sheath

• This increases the speed of nerve conduction

• Myelin acts as an insulator preventing ion loss

• Action potentials only occur at the nodes of ranvier

What factors would affect this normal ECG?

• increase of heart rate caused by exercise, then QRS complex would be closer together

Describe the events of the synapse

1. Action potential reaches the presynaptic neurone.

2. Voltage gated channels open; Ca²⁺ diffuses into presynaptic neurone

3. Vesicles move to and fuse with the presynaptic membrane.

4. Neurotransmitters are released into the synaptic cleft- (exocytosis)

5. Neurotransmitters diffuse across the cleft.

6. They bind to receptors on the postsynaptic membrane.

7. Na+ channels open; Na⁺ diffuses in the postsynaptic neurone.

8. A new action potential is generated in post synaptic membrane

What happens to neurotransmitters after depolarisation?

• Neurotransmitters are removed from receptors.

• They are broken down by enzymes in the synaptic cleft.

• Breakdown products are reabsorbed into the presynaptic neuron.

• They are repackaged into vesicles to make more neurotransmitter.

Neurotransmitters are attached to postsynaptic membrane after depolarisation. Why is this important?

• Allows postsynaptic neurone to rest

• Na+ ion channels close after depolarisation

• Neurotransmitter are reused in presynaptic neurone

What is an inhibitory neurotransmitter?

• Decreases the likelihood of an action potential.

• closes Na⁺ channels or opening Cl⁻ channels.

• Makes the membrane more negative → harder to reach threshold.

What is an excitatory neurotransmitter?

• Increases the likelihood of an action potential.

• Works by opening Na⁺ channels.

• Makes the membrane less negative → easier to reach threshold.

Explain how agonists work

• Chemicals with a similar shape to neurotransmitters.

• Bind to the same receptors.

• Produce a similar response to the natural neurotransmitter.

• Examples: nicotine, muscarine.

Explain why nicotine and muscarine are classed as agonists

• They both mimic acetylcholine (neurotransmitter)

• Increases the activity of receptors

• Binds to neurotransmitter receptor of postsynaptic neurone

• Causes Na+ ion channel to open

Explain how antagonists work

• Chemicals have a similar shape to the normal neurotransmitter.

• They bind to the same receptor sites.

• They do not trigger a response.

• They block the normal neurotransmitter from working.

• Examples: atropine and curare.

Explain why atropine and curare are classed as antagonists

• They have opposite effects on the neurotransmitter, they are similar to

• Binds to the neurotransmitter receptor of postsynaptic neurone

• Causes opposite response

1. What is parkinson’s disease?

2. What is the role of dopamine in the body? Link to number one.

1. A disease caused by the death of some neurones in the brain that release dopamine

2. This decreases the amount of dopamine being released at synapse and affects movement.

In parkinson’s, there is a ? supply of dopamine releases at synapses in the brain

Higher

If there is a reduces amount of dopamine, explain why it may lead to uncontrolled jerky movements

• Less dopamine (neurotransmitter) released into synaptic cleft from pre-synaptic neurone

• Less dopamine diffuses across synaptic cleft to post-synaptic neurone

• Less dopamine attaches to its complementary receptor on membrane of post-synaptic neurone

• Less ion channels open so there’s less depolarisation of post-synaptic neurones

Explain how L-dopa works

• L-dopa is a precursor for dopamine

• It can enter the brain and convert into dopamine & increases amount of dopamine in brain

• More dopamine is released into + diffuses across synaptic cleft

• More dopamine binds to receptor on post-synaptic neurone + depolarises neurone

How would a dopamine agonist work?

• It would have a similar shape as dopamine neurotransmitters

• The agonist would bind to receptors on post-synaptic membrane + have similar affect to dopamine

1. What is the role of serotonin in the body?

2. In some cases of depression, there is a ? supply of serotonin released at synapses in the brain

1. Its a neurotransmitter that regulates mood

2. Lower

If there is a reduced supply of serotonin, explain why it may lead to a low mood

• Less serotonin (neurotransmitter) released into synaptic cleft from pre-synaptic neurone

• Less serotonin diffuses across synaptic cleft to post-synaptic neurone

• Less serotonin attaches to its complementary receptor on membrane of post-synaptic neurone

• Less ion channels open so there’s less depolarisation of post-synaptic neurones

Why do muscle fibres contain many mitochondria?

• site of aerobic respiration

• molecules need atp for contraction of muscles

1. Arrange the following from smallest to largest- myofilaments, muscle fibres, myofibrils and muscles

2. How are they related to one another?

1. muscle, muscle fibres, myofibrils and myofilaments

(2)

• muscles are like ropes

• muscle fibres are strands inside the rope

• myofibrils are tiny threads inside each strand

• myofilaments such as actin & myosin made the threads work

COMPARE SLOW TWITCH FIBRES AND FAST TWITCH FIBRES

• ST has slower speed, FT has rapid speed

• ST has lots of blood vessels as they need big supply of o2, FT use less blood vessels

• ST use aerobic respiration, FT uses anaerobic respiration

• ST has many mitochondria for long lasting energy, FT has fewer mitochondria

• ST has lots of myoglobin as it stores o2, FT uses less myoglobin

• ST are red due to lots of myoglobin, FT are white due to less myoglobin

Explain 2 advantages of fast muscle fibres having lots of glycogen

• Quick energy supply- glycogen can be broken down quickly, which gives them energy almost immediately

• Works without oxygen- uses anaerobic r that needs glycogen so lots stored helps produce energy when no o2 is available.

1. why do ST use less glycogen?

2. How powerfully do they both contract?

3. How quickly do they fatigue?

1. ST mainly uses o2, not large stores of glycogen for long duration activities.

2. ST not very powerful as they’re built for endurance, FT very powerful as its built for quick strong bursts of force

3. ST slow to fatigue due to using o2 efficiently and less build up of lactic acid, FT fast to fatigue as anaerobic r produces lactic acid that tires them