STEM CELLS ESSAY | Life Science Grade 12

STEM CELLS ESSAY

Describe two types of stem cell therapy and for each type explain Two advantages and Two disadvantages of processes

Embryonic stem cell therapy
❖ It is extracted rom the human foetus/ umbilical cord
❖ To allow the development of other types of cells or organs
❖ Which ay be required for the body

Advantages
❖ Medical benefits on therapeutic cloning
❖ Discovery for treatment and cure for diseases
❖ Limbs or organs formed can be used in transplantations
❖ Cells can be cultured relatively under lab conditions
❖ To form large number of required cells

Disadvantages
❖ Patient’s body might reject them
❖ Destruction of blastocysts might be involved
❖ And can lead to long term effects due to interference with nature

Adult stem cell therapy
❖ Undifferentiated cells among
❖ Differentiated cells in tissues or organs
❖ Can renew Sir specialized cells types

Advantages
❖ They are able to generate new cells
❖ They can b cultured to produce larger quantity of cells
❖ Therefore they can treat injuries and diseases
❖ Your own cells can be used leading to no rejection

Disadvantages
❖ Generating of large quantity of cells may be difficult
❖ Due to small number of removed strong cells
❖ Differentiation of cell type is limited
❖ Undifferentiated cells are rare in mature tissues
❖ Isolation of these cells will be difficult

HUMAN EYE (ACCOMMODATION), HEARING ,BALANCE AND EQUILIBRIUM

A goal keeper prevented a ball from scoring when he dived to his right after that ball was kicked towards him. Just before he dived he heard his team-mate shout “your ball”. Describe how his eye adjusted to see the ball travelled towards him and describe how he heard his team-mate and maintained his balance as he dived.

As the ball travelled towards him
❖ accommodation took place
❖ ciliary muscles contracted
❖ suspensory ligaments became slack
❖ causing reduction of tension in lens
❖ lens became more convex
❖ refractive power of lens increased
❖ Image of ball fell on the retina. 

Hearing
❖ Pinna trapped sound waves into auditory canal
❖ Causing tympanic membrane to vibrate
❖ These vibrations were transferred into 3 ossicles (hammer, anvil and
stirrup))
❖ Which caused oval window to vibrate
❖ Which increased pressure of waves in cochlear
❖ Which stimulated the Organs of Corti
❖ To convert the stimulus into a nerve impulse
❖ Which was transported by auditory nerve
❖ And interpreted on the Cerebrum.

BALANCE AND EQUILIBRIUM
As he dived
❖ A change in direction and speed of the body
❖ Causes the movement if fluid in the semi circular canals
❖ Which stimulates the cristae
❖ A change in the position of the head
❖ Stimulated the maculae in the atriculus and succulus
❖ The stimuli were converted into impulses
❖ Which were transported along the auditory nerve
❖ And interpreted in the cerebrum
❖ Which sent impulses to the muscles
❖ To restore balance and equilibrium.

Hearing and reflex action:

Explain how a guy hears a sound of howling dog and how he is able to rapidly respond as the dog’s nose touched his leg.
Hearing.
❖ The pinna trapped sound into the auditory canal
❖ Causing tympanic membrane to vibrate
❖ That vibrations were transferred into tree ossicles (hammer, anvil and stirrup)
❖ Which caused oval window to vibrate
❖ Which increased pressure of waves in cochlear
❖ Which stimulated organs of corti
❖ To convert stimulus into impulses
❖ Which were transported along the auditory nerve
❖ And interpreted on the cerebrum.

Reflex action
❖ When the dogs nose touched his leg
❖ Receptors in the skin received the stimulus
❖ Which were converted into nerve impulses
❖ Impulses traveled along the sensory neuron
❖ Towards the spinal cord along dorsal root
❖ Of the spinal nerve
❖ In the spinal cord, Sensory neurons made synaptic contact with connector
❖ Impulses were transmitted along motor neuron
❖ Along the ventral root of the spinal nerve
❖ To the effector muscle
❖ Which contracted and pulled his leg away

Protection of human body

Describe how nervous and endocrine systems protect the body. Use
suitable example to describe how this protection through reflex
action and the hormone Adrenalin

Reflex action -removal of hand from being burnt
❖ Receptors in the skin receives stimulus
❖ Which are converted into nerve impulses
❖ This impulses travel via sensory neuron
❖ To the spinal cord
❖ Where sensory neuron make synaptic contact
❖ With connector
❖ Impulses are transmitted via motor neuron
❖ Along ventral root
❖ To the effector muscle
❖ Which contract and pull hand away

Adrenalin -example when you are chased by a dog
❖ Brain become aware of danger
❖ Through impulses from sense organs
❖ Adrenal gland become stimulated to secrete Adrenalin
❖ Message is then sent to various organs
❖ Blood vessels to the heart and brain dilate
❖ To increase heart rate
❖ Rate and depth of breathing increases
❖ Glycogen is converted into glucose
❖ Vital organs receive more glucose
❖ To increase muscle tone
❖ Pupil dilates
❖ Allowing rapid response to ensure safety

Hypothalamus and Adrenalin

Describe the role of hypothalamus and Adrenal gland in bringing
about changes to blood vessels of the skin and explain why this
changes take place.

Hypothalamus
❖ Changes in temperature are detected by thermo-receptors in the skin
❖ Stimulus are converted into nerve impulses
❖ Transmitted to the hypothalamus
❖ Which send impulses to the muscle layer of artrioles of the skin On cold day
❖ Artrioles close to the skin surface constrict
❖ Less blood flows to the capillaries close to skin surface
❖ Sweat production decreases On hot day
❖ Artrioles close to the skin surface dilate
❖ More blood flows to the capillaries close to the skin surface
❖ More heat is radiated/ more heat is lost

Adrenal gland
❖ Secretes adrenalin
❖ That prepares body to cope with emergency
❖ Adrenalin causes blood vessels of the skin to constrict
❖ Less blood flows to the skin surface
❖ Because skin is not a important organ during emergency
❖ Redirecting more blood/oxygen and food to vital organs
❖ To enable the body to respond during emergency

Response to unilateral light

Plants and humans respond to light differently explain how plant stem and human eye respond to unilateral light.

Plant stem
❖ Plant response to unilateral light is positive phototrophic
❖ Auxins produced in the tip of the stem
❖ So that there is high concentration of auxins on the darker side
❖ Which stimulate growth
❖ Low concentration of auxins on the light exposed side
❖ Inhibits growth
❖ There is uneven growth
❖ Which causes stem to bend towards light

How humans receive and interprets light
❖ Light enters the eye trough cornea
❖ Which refracts light
❖ Light passes through aqueous humor
❖ And pupil
❖ The size of pupil is adjusted by Iris
❖ To regulate the amount of light entering the eye
❖ Light then passes through lens
❖ Which also refracts the light
❖ Light is then passed through vitreous humor
❖ And reaches the retina
❖ Which has photo receptors and cones
❖ Which convert light stimulus into nerve impulses

 

MUTATIONS AND GENETIC DISORDERS

Explain how different types of mutations lead to genetic disorders
Types of mutations- is the sudden change in genetic composition of an individual.
❖ Gene mutation
❖ Result to changes in the structure of DNA in single strand
❖ Chromosomal aberration
❖ Change in the structure/number of chromosomes in a cell
❖ Harmful mutations
❖ Result in genetic disorder
❖ That decrease the structure of an organism

Genetic disorders
❖ Haemophilia
❖ Blood doesn’t clot
❖ Due to non-produced protein for blood clot
❖ Colour blindness
❖ Inability to differentiate between different colours
❖ Due to absence of necessary protein for photo receptors
❖ Albinism
❖ Lack of pigment in the skin
❖ Due to absence of protein that forms melanin
❖ Down syndrome
❖ The person has extra chromosome 21
❖ Due to non-disjunction (during meiosis)