Unit 5 Body Systems ( Full )

Definitons

• Ventilation: The inhalation and exhalation of air using the ventilation system

• Gas exchange: The diffusion of gases across the alveoli

• Cell respiration: A controlled release of energy from organic substance inside the cell.

Properties of gas-exchange surfaces

• Thin – Short diffusion distance

• Moist – Dissolve respiratory gases

• Large Surface area – Maximize diffusion 

• Permeable to respiratory gases – allow oxygen and carbon dioxide to pass through

• E.g. Lung, Gills

Alveoli - Adaptations

• It is the site for gas exchange

•  Large surface area:

  • There are many spherical shape alveoli

• Maintain concentration gradient:

  • Surrounded by rich blood capillaries

• Short diffusion distance:

  • Single-cell thick wall of type 1 pneumocytes

Alveoli - pneumocytes

Type 1 pneumocytes :

• Extremely thin alveolar cells that are adapted to carry out gas exchange

Type 2 pneumocytes :

• Secrete a fluid to keep the inner surface moist and allow gases to dissolve

• Secrete surfactant to reduce surface tension.

Lung ventilation

  Inspiration ( Inhalation ) Expiration ( Exhalation )

The diaphragm contracts and flattens External intercostal muscles contract Internal intercostal muscles relax Ribcage moves up and out This increases thorax volume and decreases thorax pressure Pressure inside the lungs is lower than the pressure outside Therefore, air is forced in

Diaphragm relaxes and becomes dome shaped External intercostal muscles relax Internal intercostal muscles contract Ribcage moves down and in This decreases thorax volume and increases thorax pressure Pressure inside the lungs is higher than the pressure outside Therefore, air is forced out

Lung volume measurement

• Spirometer is used to measure lung volume.

• Tidal volume: the volume of air that is breathed in or out when a person is at rest.

• Inspiratory reserve volume: the maximum volume of air that a person can breathe in.

• Expiratory reserve volume:  the maximum volume of air that a person can breathe out.

• Vital capacity: the sum of the inspiratory reserve volume, the tidal volume and the expiratory reserve volume.

Leaf structure – cross section of leaves

• Leaves are organs that are responsible for photosynthesis.

• Waxy cuticle – Prevent water loss from evaporation

• Upper epidermis – Clear layer, allows light to pass through

• Palisade mesophyll – Regular cells, contains a lot of chloroplasts

• Spongy mesophyll – Irregular cells with a lot of air space, increases surface area for gas exchange

• Guard cells – regulate the opening and closing of stomata

• Stomata – site of gas exchange [in human it is alveoli]

• Xylem – transport of water and mineral ions (from roots to leaves)

• Phloem – transport of sucrose and amino acids (from source to sink)

Factors that affect Transpiration

• Definition: Evaporation of water through the stomata.

 

Factors that affect transpiration rate	Reasons
Light intensity photosynthesis	1. Increase light intensity, increase transpiration 2. Photosynthesis occur under light, when there is light, more stomata open for gas exchange, increase evaporation.
Temperature kinetic energy	1. Increase temperature, increase transpiration 2. Increase kinetic energy in water molecules, so water evaporate faster.
Air movement water potential gradient differences Diffusion	1. Increase air movement, increase transpiration 2. Removal of the humid air, increase water potential gradient between inside and outside of the leaf. Thus water vapor diffuse faster
Humidity Water potential gradient differences Diffusion	1. Increase humidity, decrease transpiration 2. Less water potential gradient differences. Less water vapor diffuse out

Haemoglobin and oxygen transport

Haemoglobin → iron-rich protein in RBC that transports oxygen from the lungs to tissues, carbon dioxide from tissue to lungs

It consists of heme (iron) and globin, which form a complex structure enabling oxygen binding

• Oxygen is bound to haemoglobin and carried in red blood cells.

• Haemoglobin molecule consists of four polypeptide chains, with a haem prosthetic group at the centre of each chain.

• Each haem group contains one iron atom, and one oxygen molecule binds to each iron atom.

• So one haemoglobin molecule can bind up to four oxygen molecules.

Cooperative binding and Allosteric binding of haemoglobin and O2

 

Cooperative binding	Allosteric binding
Carrying oxygen Binds to haem group Increases affinity for more oxygen (induced-fit)	Carrying carbon dioxide Binds to allosteric site Decreases the affinity for oxygen (non-competitive inhibition)

Oxygen dissociation curve

• The more oxygen there is in the surroundings (high partial pressure), the more saturated the haemoglobin will be.

• The concentration of oxygen in the surroundings can be measured as a percentage or measure it as a partial pressure (PO₂, kPa)

Oxygen can only diffuse in and out of the blood from capillaries.

Oxygen dissociation curve Graph

(a) In the alveoli of the lungs 

• Oxygen is constantly being brought in by ventilation 

• Partial pressure of oxygen is kept high, at around 14 kPa. 

As blood passes through the capillaries surrounding the alveoli, oxygen is loaded on to haemoglobin and become almost 100% saturated 

(b) In tissues 

• e.g. liver or brain 

• Oxygen is used by respiration, so its partial pressure is low, about 4 kPa. 

• At this PO₂ the haemoglobin is only 50% saturated 

It unloads about half its oxygen to the cells, which use it for respiration. 

(c) In tissues that are respiring quickly 

• e.g. contracting muscle cells 

• PO₂ drops even lower, to about 2 kPa 

• haemoglobin saturation drops to about 10% 

almost 90% of the oxygen is unloaded, providing more oxygen for the muscle cells. 

(d) Actively-respiring tissues

• A lot of CO₂ is produced

• CO₂ dissolves in blood or tissue fluid to make carbonic acid and so lowers the pH

• H⁺ ions leads to a decrease of affinity for O₂ , therefore reduces the % saturation of haemoglobin at any PO₂.

• This right-hand shift is called the Bohr shift.

• So at a PO₂ of 2kPa, the % saturation is nearer 5%

95% of the oxygen are unloaded in respiring tissues.

*decrease affinity, release more O2.

blood vessels

• The circulatory system of the human body contains several different types of blood vessel:

  • Arteries → away from heart

  • Arterioles

  • Capillaries → site of exchange

  • Venules

  • Veins → to heart

adaptations of capliiaries, arteries and vein

 

	Artery	Capillary	Vein
Thickness of walls	Thick	Extremely thin - only one cell thick	Thin
Function	Carries blood away from heart	Site of materials exchange between blood and tissue	Carries blood into heart
Elasticity	Greater than vein	n/a	Less than artery
Muscularity	Greater than vein	n/a	Less than artery
Diameter of lumen	Narrower than vein	Extremely narrow (fits single RBC)	Wider than artery
Valves?	no	no	yes
Pressure of blood	high	low	low

Capillaries:

Adaptations of capillaries for exchange of materials

• One cell thick → reduces the diffusion distance for oxygen and carbon dioxide between the blood and the tissues of the body

• The thin endothelium cells of some capillaries have gaps between them called fenestrations which allow blood plasma to leak out and form tissue fluid

• Capillaries form branches in between the cells → increase the surface area for diffusion + substances to and from the cell

• Capillaries have a lumen with a small diameter →

  • Red blood cells squeeze through capillaries in single-file

  • This forces the blood to travel slowly which provides more opportunity for diffusion to occur

  • It also reduces the diffusion distance as red blood cells are brought in close contact with the capillary wall

arteries:

• narrow lumen : high pressure blood

• thick muscle fibre : prevent rupture

• thick elastic fibre : pulse.

  • elastc fibre allwos arteries to stretch - presure exerted on the artieral walls - elastic recoil - pushes blood forward. Contraction of artieries = One pulse

• vein

• thick lumen : maintain low pressure blood

• valve : prevent backflow

• thin layer of muscles and elastic fibres , srrounded by skeletal muscle.

  • skeletal muscle contract, squeeze vein , opens valve - blood move forward. Relaxes, valve close - blood trapped in vein

measurement of heart rate

• radial pulse in wrisk

• carotid pulse in neck

• The rate is the number of beats per minute (bpm).

Heart rate depends on the body’s demand for oxygen, glucose and for removal of carbon dioxide. There is a positive correlation between intensity of physical exercise and heart rate.

DVT

Deep vein thrombosis (DVT) can occur after a long period of being stationary

for example on a long haul flight or in jobs which require a lot of standing.

conorary occultion

• Coronary arteries supply the cardiac muscle with oxygen and nutrients

• Plaque buildup: build up of fatty plaque in coronary artery walls narrows the lumen, reducing blood flow to heart muscle.​

• Wall damage and stiffening: Higher pressure damages walls; inelastic fibrous tissue repairs it, hardening (sclerosis) the artery.

• Plaque rupture: Damaged plaque breaks open, triggering thrombus (clot) formation.

• Occlusion: Thrombus restricts or fully blocks (occludes) the coronary artery; dislodged pieces block smaller arterioles downstream.

consequence

• Heart attack

  • cardiac tissue requires oxygen and nutrients via conorary artieries to function

  • conorary artery blocked - result into heart attack

Treatment

• bypass surgery

blood content (4)

1. Plasma (55%) - yellow fluid contain: blood cell, nutrient, Co2, O2, hormones, antibodies, urea, heat

2. RBC(45%) - carry oxygen

3. WBC + Platelets - (less than 1%)

   • WBC: body immunity - phagocytes, lymphocytes

   • platelets: clot blood, prevent futher entry of pathogen, excessive blood loss

Tissue Fluid

• A solution that bath all cells.

• Substances do not move directly between the blood and the cell

• They first diffuse into the tissue fluid that surrounds all cells

• Then diffuse from there to the cells

Tissue Fluid - At the arterial end of the capillary bed

• Blood is at high pressure

• Blood plasma is forced out through the permeable walls

• Cells and proteins are too big to leave, so they remain in the blood

• Tissue fluid is formed by pressure filtration

Tissue Fluid - At the venous end of the capillary bed

• Blood is at low pressure

• Blood and tissue fluid are now at around the same pressure

• Tissue fluid returns by the methods below

  • Solutes enter the blood by diffusion

  • Water returns to the blood by osmosis

Tissue Fluid - Excess tissue fluid

• Not all the fluid that left the blood returns to it

• Excess tissue fluid will be drained into lymph vessels, which are found in all capillary beds

• Lymph vessels have thin walls like capillaries, tissue fluid can easily diffuse inside forming lymp

what is lymphatic system

• Consists of a network of lymph vessels flowing alongside the veins

• The vessels lead towards the heart, where the lymph drains back into the blood system near the vena cava.

• There is no pump, but there are numerous valves, and lymph is helped along by contraction of skeletal muscles.

  • collect waste and tissue from the tissue to the bloodstream

Lymphatic System Function

• The lymphatic system has three different functions:

1. It drains excess tissue fluid

2. It absorbs fats from the small intestine.

3. It is part of the immune system.

   • There are networks of lymph vessels at various places called lymph nodes

   • White blood cells are developed in lymph nodes

   • They become swollen if more white blood cells are required to fight an infection.

lymph vessel

Lymphatic vessels (or ducts) have the following features:

• Thin walls with gaps

• Valves to prevent backflow

After filtration in the lymph nodes, lymph returns to the blood circulation

Differences between the single circulation of bony fish and the double circulation of mammals

Mammals

• four chambers , two circuits 

left:  oxygenated blood enters the left side of the heart before being pumped to the body (systematic)

right: deoxygenated blood returns to right side of the heart before going to lungs ( plumonary)

• separated by a septum 

---

Fish

• 2 chambers, 1 circuit

mammal heart adaptation (8) 

 

Double circulatory system Maintain a high concentration gradient → high metabolic needs	made out of the myogenic cardiac muscle generate own electrical contractions	Sinoatrial Node (SA node) pace maker initiate heartbeat	Atrioventricular and semilunar valves ensure one-way blood flow
Four chambers (atria,ventricle) Thin musice atria - receive low-pressure blood Thick walls ventricles - generate high pumping pressure	Thicker muscle in left side of heart pump blood at high blood pressure	Coronary arteries surrounding heart Cardiac muscle is supplied with nutrients and able to remove waste	Septum separates right and left sides separate oxygenated and deoxygenated blood

Blood flow through mammalian heart

Deoxygenated

• deoxygenated blood returns from body → Vena cava (superior/interior) → right atrium → tricuspid valve → Right ventricle → pulmnary valve → Pulmonary arteries → Lungs

Oxygenated

• in the lungs , blood release Co2, Absorb O2

• Pulmonary Veins → Left atrium → bicuspid valve → Left ventricle → Aortic valve → Aorta → Body tissues

stages in cardiac cycle (3)

Atrial Systole: 

1. Electrical impulse initiated by the Sino-atrial node (SA node) [also known as the pacemaker]

2. The electrical impulse are sent through the wall of the atrium and cause atrial contraction.

3. Volume of the atrium decreases and increases the pressure.

4. Pressure in the atrium is higher than the pressure in ventricle.

5. AV valves are open , Blood is pumped into the ventricle

Ventricle systole 

1. Electrical impulse pass from SA node to Atrio-ventricular node (AVN).

2. The delay allows time for blood to transport from the atrium to the ventricles

3. AVN pass electrical impulse to Bundle of His, then spread through the Purkinje fibers in the ventricular wall

4. This cause ventricles contraction from bottom to top

5. Volume of the ventricle decreases and increases the pressure.

6. Pressure in the ventricle is higher than the pressure in the aorta and pulmonary artery.

7. Semi-lunar valves are forced open, and blood are pumped out through the aorta and pulmonary artery.

8. Pressure in the ventricle is higher than the pressure in atrium.

9. Atrio-ventricular valves are forced to close to prevent the backflow of blood.

Diastole

1. Ventricles are relaxed to allow blood to enter the atrium (Blood returns to the heart via the vena cava and pulmonary vein)

2. Pressure in the ventricle is lower than pressure in the aorta and pulmonary artery

3. Semi-lunar valves are closed to prevent the backflow of blood

4. Pressure in the ventricle is lower than pressure in the atrium

5. Atrio-ventricular valves are open

6. Blood flows passively into the ventricles

• pressure of atrium > ventricular - Av valve opens

• pressure of ventricular > pulmonary artery and aorta - SL valve open 

Pressure changes during the cardiac cycle

1. Atrial contraction begins.

2. Atria eject blood into ventricles (atrial systole) .

3. Atrial systole ends; AV valves close ('lubb’).

4. Contraction of the ventricles occurs (ventricular systole) .

5. Ventricular ejection occurs.

6. Semilunar valves close ('dupp').

7. Relaxation of the ventricles occurs (ventricular diastole) .

8. AV valves open; passive ventricular filling occurs.

vascular bundle

• Xylem → water+ minerals

• Pholem → carbon compounds - sucrose+amino acid

xylem adaptations

Lignified walls: lignin strengthens cell walls against tension. Lignin is waterproof → walls are impermeable to water

Pits: pores where water easily moves in and out of xylem

No cell contents: allow unimpeded flow of xylem sap with minimal resistance 

No End walls: allow unimpeded upwards flow of water 

Transpiration

water vapour lost via stomata

facilitates

• temperature regulation

• absorption of water and minerals from soil

• When water evaporates from cells wall during transpiration, more water is drawn from the xylem vessels to replace the loss.

• Adhesion causes water molecules to stick to the cell walls, allowing them to move through the walls of the xylem and into leaf cells.

  • This movement due to adhesion in narrow tubes is called capillary action.

• As water leaves the xylem, it creates tension / negative pressure potential within the xylem.

• This tension produces a transpiration pull, draws water upwards through xylem from roots to leaves

• Water is absorbed by the roots through osmosis to replace → generating higher hydrostatic pressure at the root which moves water up the xylem

Explain the process of transpiration and how xylem vessels are adapted for the

transport of water from roots to leaves. (7) 

MAX 5 for transpiration (marking points a,b,c,d,e,f,g,h)

a. transpiration is the loss of water from (the surface of) the leaf / through stomata;

b. loss of water by evaporation from cell walls in leaf cells causes water to be drawn from

neighbouring/other cells;

c. lost water drawn out of the xylem/creates transpirational pull;

d. transpiration pull/tension draws water up the xylem;

e. cohesion is hydrogen bonding between water molecules;

f. cohesion (of water molecules) ensures a continuous column of water;

g. adhesion of water is (hydrogen bonding) between water and other polar molecules;

h. (adhesion is involved) in capillary action in soil/in plant cell walls/lignin;

Max 3 for xylem adaptation (for marking points i,j,k,l)

i. xylem (vessels) lack cell contents for unimpeded flow;

j. xylem (vessels) have lignified walls to withstand tensions;

k. xylem (vessels) have incomplete or absent end walls for unimpeded flow;

l. xylem (vessels) have pits/pores/gaps for entry and exit of water;

 Generation of root pressure in xylem vessels by active transport of mineral ions

• plants can also push water up from the roots by generating root pressure

• Generated to cause water movement in roots and stems when transport in xylem due to transpiration is insufficient

• For example when high humidity prevents transpiration, or before the leaves of deciduous plants develop in spring

__

• Root pressure occurs as minerals are actively transported from the soil into root cells, which lowers the water potential of these cells (a lower water potential means a higher solute concentration).

• As minerals enter, the water potential in the xylem decreases, and water follows by osmosis.

• The entry of water into the xylem generates a positive pressure potential / hydrostatic pressure which pushes the column of water upwards—this is known as root pressure.

stem - draw and label and function 

• support, elevate leaves for seed dispersal and photosynthesis

epidermis - protection and waterproof 

cortex - support and photosynthesis 

pith - packing tissue ( bulking out the stem) 

xylem - transport of water from roots - leaves 

cambium - production of xylem&phloem tissue 

phloem - transport of sugar from source to sink 

root - draw label and function

• endodermis: layers of cell water pass through reach xylem

• cortex: cells loosely packed - enable movement of water

• epidermis: has root hair to increase water and mineral absorption

• xylem: transport of water from roots to leaves

• phloem: transport of sugar from source to sink

measure rate of transpiration

potometer

Phloem

• Phloem is responsible for transporting sucrose & amino acid

• Phloem is made up of the following of live cells: Companion cell and Sieve tubes.

• Connections between companion cells and sieve tubes are called plasmodesmata.

• As the cells are alive, it is possible for active transport to take place for translocation of nutrient to occur.

Adaptations of phloem sieve tubes and companion cells for translocation of sap

Sieve tube elements

• pores in sieve plate → allows sap to flow between sieve tubes

• no nucleus, reduced cytoplasm and organelles (ribosome,vacuole..) → maximises space for sap transport

Companion cell

• Presence of many mitochondria → to synthesis ATP for active transport for phloem loading / unloading

Plasmodesmata

• between companion cell and phloem sieve tube → exchange of material and communication between cells

Adaptations ease the flow of sap and enhance loading and unloading of carbon compounds into phloem sieve tubes

translocation

Active transport by phloem: Translocation (movement of sap)

Source: where carbon compounds are produced ; Sink: where carbon compounds are consumed 

1. At the source, nutrients are actively transported into the companion cell, and flow through passively through plasmodesmata to the phloem sieve tube cells 

2. This increases the solute potential, thereby causing water to enter from the xylem into the phloem sieve tube cells through osmosis (low to high solute potential) 

3. This increases the hydrostatic pressure, thereby pushing the sap towards the sink 

4. At the sink, nutrients actively/passively unload and reduces the solute potential, hence water returns back to the xylem, lowering hydrostatic pressure

skeleton (2)

• exoskeleton → Arthropods such as spiders and insects have exoskeletons consisting of chitin that cover most of their body 

• endoskeleton (Vertebrates have endoskeletons consisting of bones )

• Provide anchorage for muscles

• act as levers for movement.

joint (2)

• hinge joint ( elbow and knee)

  • one plant of movement

  • bend & straight

• ball and socket joint ( hips, shoulder)

  • large range of movement

  • protraction, retraction , abduction, adduction , rotation

measure joint

goniometer

most allowing movement joint

synovial joint

ex. human hip joint 

 

Movement at a synovial joint

 

Bone (Femur & Pelvis)	Cartilage	Synovial fluid	Ligaments	Muscles	Tendons
Provide anchorage for muscles and ligaments. Guide the types of movements that can occur at a joint.	Tough, smooth tissue that covers a bone at the joint. Helps to prevent friction by preventing contact between regions of bone that might rub together. Absorbs shock.	Fills a cavity in the joint between the cartilages on the ends of the bones. Lubricates the joint, and helps prevent friction.	Connect bone to bone.  Tough cords of tissue containing large quantities of collagen (protein). Prevent movements that would cause dislocation.	Provide forces that cause movement at the joint.	Attach muscle to bone. Composed of living tissue with large quantities of collagen. Allow forces to be transmitted between muscle and bone.

Anagonistic muscle action to facilitate internal body movements

External and internal intercostal muscle fibres oriented differently - meaning contractions pull the rib cage in opposite directions 

• External intercostals 

• Contraction pulls the rib cage up and out - aiding inhalation - and stretches the internal intercostal muscles 

• Internal intercostals 

• Contraction pulls rib cage in and down - aiding exhalation - and stretches the external intercostal muscles

skeletal muscle

• attach bones - cause movement of animal body 

• It consists of large multinucleated cells called muscle fibers.

• There are also mitochondria between the myofibrils.

level of organisation 

muscle fibres → myofibris → microfillaments → sacromere 

Structure and function of motor units in skeletal muscle

• Around the myofibrils is a specialized type of endoplasmic reticulum – the sarcoplasmic reticulum. 

• Skeletal muscles are voluntary muscles that requires electrical impulse from the brain.

• Electrical impulse are sent from the brain through the motor neuron to the neuromuscular junction.

• Each motor neuron has a set number of muscle fibers that it control called a motor unit.

Motor units

• Contraction of skeletal muscle is coordinated by motor units

• A motor unit comprises a single motor neuron

• and all of the muscle fibers that it stimulates via neuromuscular junctions

• The muscle fibres contract when stimulated by the motor neuron

• The stimulus passes from the neuron to the muscle fibre at a synapse called the neuromuscular junction

• require neurotransmitter: acetylcholine

Sarcomere and Muscle contraction

• A sarcomere is a subunit of a myofibril.

• Between two Z lines is one unit of sarcomere.

• two protein filaments : Myosin & Actin

• myosin 

  • Light bands are represented by thin actin filaments only, which are attached to either end of the Z lines.

• actin 

  • Dark band represent the region containing thick myosin filament, which contains heads that form cross-bridges by binding to the actin.

crose bridge cycle

1. When a nerve impulse arrives at the neuromuscular junction, Ca²⁺ ions are released from the sarcoplasmic reticulum

2. Ca²⁺ ions bind with troponin, causing it to change shape, moving tropomyosin to expose the myosin-binding site on actin

3. Myosin heads( hydrolyses ATP to ADP + Pi and stored that energy in its conformation, The myosin head is cocked) → bind to actin, forming crossbridges 

4. Myosin releases ADP and P_i, causing the power stroke which pulls the actin filament towards the centre of the sarcomere

5. ATP binds to myosin → myosin detach from actin → breaking the crossbridges

6. ATP is hydrolysed to ADP and P_i → The energy released from hydrolysis is used to “recock” the myosin head (into its high‑energy conformation), ready to bind further along the actin filament toward the Z line.

7. Myosin heads bind to actin at a new binding site further along the sarcomere

8. The cycle continues until Ca²⁺ is pumped back into the sarcoplasmic reticulum, or there is no ATP available

titin

1. contraction of antagonistic muscle → creates energy

2. Energy is needed to lengthen a muscle, which stretches titin

3. Titin then releases energy as it recoils, adding to the force of contraction in that muscle

• prevent overstretching of sacromere 

• holds myosin filaments in place 

Explain how a skeletal muscle contracts

pathway of nerve impulse

Stimulus (e.g., heat/pain) is detected by a receptor (e.g., thermoreceptor)

which generates a nerve impulse;

The impulse travels along the sensory neuron (afferent) to the spinal cord/inter (relay) neuron/Central Nervous System (CNS);

The interneuron synapses with a motor neuron (efferent) which carries the impulse away from the CNS;

The motor neuron transmits the impulse to the effector muscle (e.g., biceps), causing it to contract/bring about the response;

Definitions

Tropism: the turning of all or part of an organism in a particular direction in response to an external stimulus.

Synergism - work together to stimulate a process 

Antagonism - have opposing effects to regulate a process 

Positive feedback: the amplification of a body’s response to a stimulus

Circadian rhythm: Pattern of sleep cycles that organisms are adapted to

Peristalsis: Muscle contraction that moves food through the digestive tract

System integration

• This is a necessary process in living systems. Coordination is needed for component parts of a system to collectively perform an overall function

• responsible for emergent properties.

1. communication/coordination 1. hormone 2. nervous signalling

2. Transport of materials

emergent properties

• a property that is only present when parts of a system work together

• ex. Cheetah as predators

  • Flexible spine: acts as spring during running; increases stride length

  • Longer hind limb bones - increases stride length

  • Grooves on claw pads to aid grip

All of these adaptations together make the cheetah a great predator!

Integration in terms of communication

 

Nervous system	Hormones:
Nervous Systems Transmitted through neurons	Endocrine system Transmitted through the bloodstream
Electrical impulse as messenger	Hormone as a messenger
Quick in conduction	Slow in conduction(binds on receptor in target cells)
Short duration of effect	Long duration of effect
Controls both voluntary and involuntary functions (autonomic nervous system)	Controls involuntary functions

• E.g. Sympathetic(SNS) and Parasympathetic(PNS) nervous system → to control heart rate, adrenaline to control fight-or-flight response.

The brain as a central information integration organ

1. Receive info

   1. Inputs (Afferent Neurons eg. sensory): The brain receives data from the outside world (sensory) and from inside the body (pain, temperature).

2. Stores info + Processes info

   1. Process & Store: The brain interprets these signals, makes decisions, and stores memories.

3. Send signal → makes a decision + coordinates life processes

   1. Outputs (Efferent Neurons eg. motor neurons): The brain sends commands back to Effector organs eg. muscles or glands to take action

Afferent and Efferent

Afferent : Carry signal towards CNS

Efferent : Carry signal away from CNS → initiate actions

Brain structure

Cerebrum is divided into two hemispheres.

• The largest part of the brain composed of two halves known as the cerebral hemispheres.

• Involved in controlling vision, thinking, learning, emotions as well as voluntary control of the body–collectively referred to as → advanced mental activity.

Cerebellum is divided into two hemispheres

• and is responsible for: voluntary movement, coordination, and balance → movement

Brainstem is divided into

• midbrain, pons, and medulla (involuntary activities)

Parts of cerebrum

• The cerebrum contains many different parts:

  • Corpus callosum - a band that connects the two cerebral hemispheres

  • Frontal lobe - important for expressive language and higher-level functions such as learning.

  • Temporal lobe - this processes auditory information

  • Parietal lobe – important for processing somatosensory input (e.g. touch)

  • Occipital lobe - located at the back of the cerebrum this is known as the visual cortex

The brain and information processing - Cerebellum & Brain stem with medulla oblongata & hypothalamus & Pituitary gland

• Cerebellum - located underneath the cerebrum, this plays an important role in coordinating muscle movements as well as balance.

—

• Brainstem containing Medulla oblongata - located at the base of the brain, this controls many vital body processes such as breathing, heart rate, and blood pressure. → involuntary

—

• Hypothalamus - found just beneath the middle part of the brain, this is involved in thermoregulation as well as the production of hormones that are involved in the control of the pituitary gland. ex. dopamine, ADH, oxytocin, GnRH

—

• Pituitary gland - located on the underside of the brain and attached to the hypothalamus to secrete various hormones, such as oxytocin and FSH.

Nervous system includes

1. CNS

2. Neuron

→ CNS ( central nervous system )

• brain → process complex sensory input, initiate motor actions, handle high order thinking(thoughts, emotion)

• spinal cord → transmits signal between brain → body + involuntary action

→ PNS (peripheral nervous system)

• Nerves

The spinal cord as an integrating centre for unconscious processes

• Spinal cord as part of the central nervous system (CNS)

• controls some of the unconscious reflexes associated with balance and other skeletal muscle functions that are not controlled by the brain.

  • The spinal cord mediates information between the brain and PNS.

  • It integrates information from unconscious processes only.

____

• Two main tissues :

• 1. white matter

  • Transmit signal (transport)

  • Receive from sensory receptors ( Sensory receptors > Brain)

  • Transmit to other organs ( Brain > Organs )

  • composed on bundle of myelinated axons → carries electrical impulse to and from the brain.

2. Grey matter (neurons, unconscoscious processing)

   • contains cell body of motor neurons, relay neurons, and synapses

   • Process information + decision making for UNCONSCIOUS PROCESSING

   • ex. movement of digestive system

Input to the CNS through sensory neurons

• Sensory receptors (detect external/internal environement) → Sensory neurons → CNS( process information) → Motor neuron → Effector organs

Sensory receptors

1. External

   1. Touch, heat, light

2. Internal

   1. stretch receptors, chemoreceptors

Output from the cerebral hemispheres to muscles through motor neurons

• in betweem cerebral hemispheres → Motor cortex

  

contains cell body of motor neuron → axon and terminal extend to different effector organs

• Spinal cord as part of the central nervous system (CNS) controls some of the unconscious reflexes associated with balance

• and other skeletal muscle functions that are not controlled by the brain.

Nerves & Neuron

Neurons are the nerve cells

• They have long nerve fibres (axons) which may be myelinated or unmyelinated

Nerves are bundle of nerve fibre surrounded in a sheath

• Most nerves contain fibres of both sensory and motor neurons

Pain reflex arcs as an example of involuntary responses with skeletal muscle as the effector

1. stimulus → sensory receptor → sensory neuron → CNS → motor neuron → Effector organs → Response

• Receptors: Carries out transduction (the conversion of physical stimulus into electrical signal)

• Sensory neuron: Carries electrical impulse to CNS

• CNS - interneuron (relay neuron): Carries an electrical impulse to a specific motor neuron.

• Motor neuron: Carries an electrical impulse to the effector organ

• Effector: Can be either a muscle or a gland → carry out a response

Role of the cerebellum in

→ coordinating skeletal muscle contraction and balance

• The cerebellum receives information from the cerebrum, brainstem and spinal cord.

• The initiation of body movement is by the motor cortex of the cerebrum.

  • Movement begins : cerebellum receives feedback impulses from various area of the body.

  • Then sent out impulses to coordinate the movement and the timing.

Movement include

1. coordinate muscle contraction timing

2. balance

3. posture

4. things that require muscle memory
   

Hormones

Endocrine system

Endocrine glands secrete hormones directly into the bloodstream to cause changes in the body

Control of the endocrine system by the hypothalamus and pituitary gland

→ Hypothalamus attach to pituitary gland

→ links nervous system to hormonal system

• The hypothalamus can respond to input signals by inhibiting or stimulating the pituitary gland.

  • The hypothalamus has many specialized groups of cells called nuclei.

  • contain sensors for blood temperature, osmolarity, or receive information from sense organs, e.g. the eyes

  • The nuclei in the hypothalamus control the release of hormones from the pituitary gland.

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eg. Osmoregulation

1. Hypothalamus detects dehydration → promopts pituitary to releases ADH→ stimulates reabsorption of water

eg. Puberty

1. Hypothalamus releases GnRH (hormone) → stimulate pituitary gland releases LH, FSH

Modulation of sleep patterns by melatonin secretion as a part of circadian rhythms

Circadian rhythm: Pattern of sleep cycles that organisms are adapted to

Melatonin → secreted by pineal glands

• Circadian rhythm set by special groups of cells in the hypothalamus called the suprachiasmatic nuclei (SCN)

• control the secretion of the hormone melatonin from the pineal gland

Modulation of sleep patterns by melatonin secretion as a part of circadian rhythms

• Light inhibits the production of melatonin.

Light receptor → CNS → Pineal gland

• integrated by sensory neuron in eyes

• Causes drop in temperature, drowsiness, sleep

• Melatonin secretion decreases with age → sleep patterns become more irregular as we grow older.

• The body’s circadian rhythms are disrupted by traveling rapidly between time zones → Jet lag

Epinephrine (adrenaline) secretion by the adrenal glands to prepare the body for vigorous activity

• Adrenaline is responsible for flight-or-fight response / vigorous activity

• Increase glucose and oxygen supply to skeletal muscle

  • Increase heart rate ( SA Node ) and blood pressure

  • Increase blood flow to liver and muscles (vasodilation)

  • Decrease blood flow to guts and kidneys (vasoconstriction) → not essential during emergency

  • Pupil dilation

• Prepare body for vigorous, immediate response with intense muscle contractions.

• Secreted by the adrenal glands.

Feedback control

Feedback control of heart rate - sensory inputs

• The heart rate can be affected by hormones (e.g. adrenaline) and nervous control:

• The medulla ( cardiovascular control centre) controls the sino-atrial node (SAN) via nerves.

  • The sympathetic nerve speeds up the heart rate in response to a decrease in pH in the blood due to CO₂ rising

  • Impulses carried by the vagus (parasympathetic) nerve slow down the heart rate when the concentration of CO2 decreases, and pH increases

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• Nervous control of HR is coordinated by the medulla

  • Actioned by the vagus nerve (parasympathetic) and the sympathetic nerve.

  • Can be overridden by Adrenaline → stimulates the sinoatrial node to increase heart rate.

Feedback control of heart rate - baroreceptors and chemoreceptors

The structure that sets your heart rate → the pacemaker of the heart

This structure can adjust heart rate based on conditions within the body, which are sensed by

• Baroreceptors: sense changes in blood pressure in aorta

• Chemoreceptors: sense changes in pH (Co2, O2)

Located in the aortic arch and the branches of the carotid arteries.

Nerves carry signals from these receptors to the medulla in the brain

• Receptors in vessels → sensory nerves → medulla → sympathetic/parasympathetic nerves → SAN and heart.

Feedback control of heart rate and stroke volume - increase in heart rate

1. During exercise, respiration rate and blood pressure increases, the wall of the artery is stretched and detected by the baroreceptors.

2. O₂ decrease, CO₂ increase, pH decrease, these are detected by the chemoreceptors.

3. These result in an increased rate of action potential sent to the medulla.

4. Medulla will respond by sending more impulses, through the sympathetic nerve, to the SAN → increase the heart rate and the force of contraction.

5. This will increase the cardiac output.

Feedback control of heart rate and stroke volume - decrease in heart rate

1. After exercise, respiration rate and blood pressure decrease, the wall of the artery is recoiled and detected by the baroreceptors.

2. O₂ increase, CO₂ decrease, pH increase, these are detected by the chemoreceptors.

3. These result in an decrease rate of action potential sent to the medulla.

4. Medulla will respond → sending more impulses to the SAN through the parasympathetic nerve to decrease the heart rate and the force of contraction.

5. This will decrease the cardiac output.

Feedback control of ventilation rate

• During exercise, chemoreceptors in the brainstem detect a drop in pH, caused by increased CO₂ level in the blood. (refer to transport in blood)

• Chemoreceptor → send nerve impulses → respiratory center in the medulla.

• Respiratory center then sends impulses intercostal muscles and diaphragm, causing them to contract harder and faster. 

Control of peristalsis in the digestive system by the central nervous system and enteric nervous system

Peristalsis: Muscle contraction that moves food through the digestive tract

Peristalsis include voluntary and involuntary movement

• voluntary: CNS(brain&spinal cord)

  • Inititation of swallowing

  • Egestion

• Involuntary : ENS( enteric nervous system)

  • coordinating movement in the gut

HL

Tropism:

the turning of all or part of an organism in a particular direction in response to an external stimulus.

eg. phototrophism , hydrotrophism , gravitropism

• Positive: Towards stimulus

• Negative: Away stimulus

Phototrophism

• Shoot bends towards light and shows positive phototropism.

• As for roots, it bends away from light and shows negative phototropism.

Plants require sunlight and water to carry out photosynthesis 

Tropic movements mean plants are able to meet these requirements 

• Stem of the plant has positive phototropism 

• Roots of the plant have positive hydrotropism

Phytochromes

• Phytochromes are plant hormones that regulate physiological processes in plants.

• Transported in the xylem and phloem to specific regions

• Functions:

  1. signal molecules to control growth

  2. development of flowers, fruits and seeds

  3. help the plant to respond to environmental stimuli.

Phytohormones

Auxins	Cytokinins	Gibberellins	Abscisic acid(ABA)	Ethylene
Growth hormone Produced in shoot apical meristem (tip) Cell elongation for tropic movements Inhibit growth of lateral buds (causes vertical elongation)	Promote cell division  Abundant in growing tissues Produced in the roots and pass to leaves and fruits Promote cell division and differentiation of the meristem	Group of hormones  Plant growth  Produced in apical meristem of roots and shoots Elongation of shoot  Seed germination  Flower maturation Breaking seed dormancy  Delaying ageing	Inhibits elongation of stems  Induces dormancy in seeds (seeds fail to germate even in ideal conditions) Involved in the dropping of leaves*	Gas produced by ageing tissues  Causes leaves, fruits and flowers to drop  Role in fruit ripening

ABA: When water is scarce, plants synthesize more ABA, which travels to leaf guard cells to induce stomatal closure, significantly reducing transpirational water loss.

Auxin

• grow at the tip of stem

• stimulate cell elongation

• stimulate growth of plant

→ negative phototropism, auxin move away from light stimulus

Auxin : Light over head & Light on one side

Light overhead

• Auxin produced at the tip diffuses down the stem evenly 

• Auxin evenly distributed 

• All cells grow at the same rate 

• Shoot grows The shootvertically upwards

Light source to one side

• Auxin molecules move towards the shaded side of the shoot, away from the light 

• Increased concentration of auxin on the shaded side

• causes rapid cell elongation and growth on that side

• Uneven growth causes the stem to bend towards the light source

Polar auxin transport

Transport of auxin is directional 

Active directional cell-to-cell movement 

• Entry into a cell: Passively or via auxin influx carriers (proteins in membrane)

• Exit from a cell: Auxin efflux pumps (proteins in membrane)

Phototropism controlled by Auxin – Auxin gradient

• Auxin is produced at the apex (tips) of the shoot.

• When light in the shoot is detected → they trigger movements of auxins by active transport carried out by auxin efflux pumps (carriers).

• Efflux pump pumps auxin from the cytoplasm out into the cell wall, then diffuses to the next cell.

• Once it enters the cell, the auxin is trapped inside the cytoplasm until the efflux pump pumps it out again.

• Auxin efflux pumps are moved in response to the differences in light intensity, creating a concentration gradient of auxin from:

  • lower on the lighted side and higher in the shaded side.

Phototropism controlled by Auxin – Elongation of cell

• Plant cells contain auxin receptor, when auxin binds, transcription of the genes for proton pump is promoted.

• The expression of these genes causes the secretion of hydrogen ions into the cell wall.

• The hydrogen bonds between the cellulose will be weakened and loosens the cell wall.

• Allowing expansion of cell due the increase water uptake and higher turgor pressure.

Integration of root and shoot growth

• Auxin is produced in the shoot and cytokinin is produced in the root.

• Both areas are growing regions of the plant.

• Auxin is responsible for cell elongation and cytokinin is responsible for cell division.

• Both phytochromes needs to be transported to the opposing growth regions to regulate the growth of all parts of the plant and integrate both signals.

• Cytokinin is transported through xylem up the plant and auxin is transported through phloem down the plant.

Root and shoot growth work together for cell growth

• Together, the phytohormones work on meristems ( rapidly growing tissues made of undifferentiated cells) to integrate cell growth

The ratio of the two determines whether it results in:

Synergism - work together to stimulate a process 

Antagonism - have opposing effects to regulate a process 

Feedback control of fruit ripening

• Positive feedback: the amplification of a body’s response to a stimulus

• Ethylene (Ethene) is produced in ripping fruits.

• Ones ripping process started, the fruit will produce more ethene.

• When one fruit started to produce ethene, it will cause the surrounding fruit to ripen and produce even more ethene.

• This helps fruits to become more attractive to herbivores therefore increasing the seed dispersal rate in their corresponding reproductive season.

Describe how an impulse passes from the relay neuron to the motor neuron. [3]

A. impulse causes relay neuron to release of neurotransmitter into synapse;

B. neurotransmitter diffuses across the synapse and binds to its receptor on the motor neuron;

C. causing Na⁺ (voltage-gated) channels to open;

D. new impulse generated in motor neuron;

E. if threshold is reached;

Definitions

• Ligand: Molecules that bind reversibly to specific proteins.

• Receptor: The protein to which a ligand binds.

• Signal transduction pathways: A series of binding between various ligands and receptors that helps transducing the signals over varying distance between or within a cell and end with a response.

• Quorum sensing  - a mechanism by which bacteria can alter group behavior depending on population density.

• Cytokines - small proteins involved in immune response 

• Transmembrane receptors: receptors that are embedded in the cell membrane.

• Intracellular receptors: receptors that are within the cell cytoplasm

• GPCR : Multi-pass transmembrane protein receptor

• Acetylcholine receptor :  Example of chemically gated ion channel receptor & Multi-pass protein: Composed of many domains that thread back and forth across the cell membrane several times

• Tyrosine kinase ( insulin receptor)  : A pair of single pass proteins with 3 domains 

• Kinases : enzymes that use a phosphate group from ATP to phosphorylate a specific molecule

• Positive feedback : Amplifies cell signalling to enhance or reinforce a response

• Negative feedback : Dampens cell signalling to prevent over-activation of a pathway

Ligand in Chemical Signalling

• Ligand: Molecules that bind reversibly to specific proteins.

• Receptor: The protein to which a ligand binds.

• Signal transduction pathways: A series of binding between various ligands and receptors that helps transducing the signals over varying distance between or within a cell & end with a response.