B3 Flashcards
Describe the structure of the nervous system
The nervous system is made up of a Central Nervous System, Peripheral Nervous System, sensory, relay and motor neurones and sensory receptors.
How does the nervous system work?
The nervous system detects changes in the external environment. This information is sent to the brain which processes it, and the brain decides on an appropriate response and sends an impulse to another part of the body telling it how to respond
What are the 3 main stages to a nervous response?
Stimulus - a change in environment
Sensory receptors - groups of cells that detect stimulus
Effectors - where a response occurs (muscles/glands)
Where does the nervous system go to?
The nervous system goes to all parts of the body, and has many links
What do sensory receptors detect?
What do they change?
Different receptors detect different stimuli. They change the stimulus into electrical impulses that travel along neurones (nerve cells) to the CNS.
What do sensory neurones do? + draw a diagram of them
Sensory neurones carry electrical impulses from receptor cells to the CNS. see p.g 89
What do relay neurones do? + draw a diagram of them
Relay neurones carry electrical impulses from sensory neurones to motor neurones. see p.g. 89
What do motor neurones do? + draw a diagram of them
Motor neurones carry electrical impulses from CNS to effectors. see p.g. 89
Draw a flow diagram to summarise the steps involved in a nervous response. How long does it take?
Stimulus > Receptor Cells > Sensory Neurone > Spinal cord > Brain > Spinal cord > Motor neurone > Effector > Response - takes around 0.7s
What is a coordinated response?
A coordinated response is a series of responses that are processed together
What is a reflex action?
How long does it take?
A reflex action is automatic, and happens without thinking. They take 0.2s by skipping out the brain
When do reflex actions occur?
They often occur when you’re in danger, and take care of basic bodily functions like heart rate.
Draw a flow diagram to show a reflex arc
stimulus > receptor cells > sensory neurone > relay neurone (synapses) > motor neurone > effector > response
Draw a labelled diagram of the eye
see p.g. 92
Cornea and its function
Transparent coating on front of eye - protects the eye and refracts light entering eye
Pupil and its function
Central hole in iris - allows light to enter eye
Iris and its function
Coloured ring of muscle tissue - alters pupil size by contracting or relaxing
Lens and its function
transparent biconvex lens - focuses light clearly onto retina
Ciliary body and its function
ring of muscle tissue - alters shape of lens
Suspensory ligaments and its function
ligament tissue - connects ciliary muscle to lens
Optic nerve and its function
nervous tissue - carries nerve impulses to brain
Common defects of the eye include …
short sightedness, long sightedness and colour blindness
How is short sightedness caused?
By a person’s lens being too strong or by the eyeball being too long. A person who is short sighted cannot see distant objects clearly, and the light rays meet in front of the retina
How can short-sightedness be overcome? + draw a diagram to show this
By using a concave lens, it bends the light rays outwards so they meet at the retina
How is long sightedness caused?
By a person’s lens being too weak or by the eyeball being too short. A person who is long sighted cannot see nearby objects clearly, and the light rays meet behind of retina
How can long-sightedness be overcome? + draw a diagram to show this
By using a convex lens, it bends the light rays inwards so they meet at the retina
What is colour blindness?
Colour blindness is when people have difficulty making out different colours
What are the photoreceptor cells in the eye?
Rods and Cones
Rods
They respond to light and allow you to see in low light levels
Cones
These respond to different colours, different cone cells respond to red, green and blue light
What is the brain’s function
The brain processes all the information collected by receptor cells and produces a coordinated response using the information
Draw a labelled diagram of the brain
see p.g. 94
Cerebrum and its function
controls complex behaviours such as learning, memory, personality and conscious thought
Cerebellum and its function
controls posture, balance and involuntary movements
Medulla and its function
controls automatic action such as heart rate and breathing rate
Hypothalamus and its function
regulates temperature and water balance
Pituitary gland and its function
stores and releases hormones that regulate many body functions
Explain some of the difficulties of investigating brain function
There is the difficulty in obtaining and interpreting case studies and there is the consideration of ethical issues
What have scientists used to investigate brain function? (4)
- Mapping the brain using evidence from stroke victims
- Placing electrodes inside animal and human brains
- CT scans
- MRI scans
What ethical issues surround investigating brain function? (4)
- Patients must give consent for medical information to be shared
- Many case studies need to be analysed
- Several areas of the brain may be involved in a specific function
- Many people believe animal testing is unethical
What are the limitations of treating damage in the PNS?
The PNS has limited ability to regenerate. Minor damage often self-heals, and more severe damage can be treated through surgery
What are the limitations of treating damage in the CNS?
The CNS cannot regenerate. Any damage is permanent unless it can be treated by surgery
Why is it difficult to repair the CNS?
As it is difficult to repair an individual nerve fibre without damaging others. Spinal damage usually lead to permanent loss of function or disability
Describe the principles of hormones
Hormones are chemical messengers that are made in endocrine glands and are secreted into the blood
What are target cells?
These are the cells where specific hormones bind to specific receptors. They are in target organs
What is the endocrine system?
The endocrine system is all of the endocrine glands and hormones they produce. It controls and coordinates body processes with the nervous system
Draw a diagram of the endocrine system, labelling all of the hormones you know
see p.g. 101
What is thyroxine and where it is produced?
Thyroxine is a hormone produced in the thyroid gland.
What is the role of thyroxine in the body?
Thyroxine plays a vital role in regulating the body’s metabolic rate - the speed at which the body transfers energy from its chemical stores in order to perform its functions
What is adrenaline and where is it produced?
Adrenaline is a hormone produced in the adrenal glands, near the kidneys.
What is the role of adrenaline in the body?
Adrenaline prepares the body for intensive action, which is the ‘fight or flight’ response
What is negative feedback?
Negative feedback is when a small change is detected by sensory receptors, and effectors work to reverse the change
What does thyroxine control and how does it do this?
Thyroxine controls how much energy is available to cells, and it does this through a negative feedback system.
What happens when the body requires more energy?
The hypothalamus causes the pituitary gland to release TSH (thyroid stimulating hormone)
What does TSH do and what is the result of this?
TSH stimulates the thyroid gland to release thyroxine, which increases the metabolic rate, allowing cells to transfer additional energy
What happens when the cells have the required amount of energy?
The hypothalamus inhibits the production of TSH, so the thyroid gland stops releasing thyroxine
Draw a negative feedback cycle for controlling thyroxine levels
see p.g. 103
What hormones are involved in the menstrual cycle?
Oestrogen, Progesterone, Follicle stimulating hormone (FSH), testosterone and Luteinising hormone (LH)
What is oestrogen made by, and what is the role of oestrogen in human reproduction?
Oestrogen is made and secreted by the ovaries. It causes the lining of the uterus to build up
What is FSH made by, and what is the role of FSH in human reproduction?
FSH is secreted by the pituitary gland, and it travels to the ovaries where it causes an egg to mature
What is the role of LH in human reproduction?
LH triggers ovulation at the middle of the cycle when its levels reach a peak
What is the role of progesterone in human reproduction?
Progesterone maintains the uterus lining.
Levels of … remain high during pregnancy
progesterone
What is the menstrual cycle?
The menstrual cycle is a cycle in which a woman’s body gets ready for pregnancy. It lasts about 28 days
Draw a labelled diagram of the female reproductive system
see p.g. 104
Menstrual cycle
Day 1 -
Day 14 -
Day 1 - the lining of the uterus starts to thicken ready to receive a fertilised egg. At the same time an egg matures in one of the ovaries
Day 14 - The egg is released from the ovary - ovulation
What happens if the egg is fertilised?
If the eggs fertilised it may implant in the uterus lining, and the woman is pregnant
What happens if the egg isn’t fertilised?
The uterus lining and the egg are removed from the body
This process is known as a period or menstruation
Explain the interactions of FSH, LH, oestrogen and progesterone in the control of the menstrual cycle
- FSH stimulates the ovaries to produce oestrogen
- Oestrogen inhibits the production of FSH, to prevent more than 1 egg maturing
- Oestrogen also stimulates the production of LH
- Progesterone inhibits LH
Draw graphs to show what happens to the levels of the reproductive hormones and the uterus lining during the menstrual cycle
See p.g. 105
Why are hormones used in contraception?
Hormones can disrupt the normal female reproductive cycle
Non-hormonal methods of contraception
Non-hormonal method are barrier methods that prevent a sperm contacting the egg or physical devices that release chemical compounds that kill sperm cells or prevent the implantation of fertilised eggs
Give some examples of non-hormonal contraceptive techniques
condom, diaphragm or cervical cap, intrauterine device
Evaluate the use of a condom
Placed over penis (male) or vagina (female) - prevents sperm entering vagina
Can prevent STIs
Evaluate the use of a diaphragm or cervical cap
Inserted into vagina to cover cervix, prevents sperm cells entering uterus
not effective unless used in combination with a spermicide
Evaluate the use of IUD
Inserted into uterus, releases copper which prevents sperm surviving in uterus and Fallopian tube
remains effective for 5 - 10 years
Give some examples of hormonal contraceptive method
Oestrogen and progesterone pill, progesterone pill, intrauterine system
Evaluate the use of combined pill
Prevents ovulation by thickening mucus from cervix, stopping sperm reaching an ovum. Prevents implantation of fertilised egg onto uterus wall
taken daily for 21 days of menstrual cycle
Evaluate the use of progesterone pill
Thickens mucus from cervix, stopping sperm from reaching ovum. Thins lining of uterus preventing implantation and can prevent ovulation
must be taken around same time everyday
Evaluate the use of IUS
Inserted into uterus. Thickens mucus from cervix, stopping sperm from reaching ovum. Thins lining of uterus preventing implantation and can prevent ovulation
remains effective for 3-5 years
How effective is a male condom?
98%
How effective is a female condom?
95%
How effective is a diaphragm and cap?
92-96%
How effective is an intrauterine device?
over 99%
How effective is a combined pill?
over 99%
How effective is a progesterone pill?
over 99%
How effective is an intrauterine system?
over 99%
Explain the use of FSH in modern reproductive technologies to treat infertility
FSH can be used as an artificial fertility drug, which stimulates eggs to mature in the ovaries
Explain the use of IVF in modern reproductive technologies to treat infertility
This technique involves eggs and sperm being fertilised outside the body
FSH and LH are given to the mother to ensure that as many eggs in the ovaries mature
What is phototropism?
Phototropism means growing towards the light
What is gravitropism?
Gravitropism means growing in the same direction as gravity
What is auxin?
Auxin is a plant hormone that enables a plant to grow towards or away from a stimulus
How do plants respond to light?
Draw a diagram to explain this
When light hits one side of a shoot tip, the auxin moves to the other side. These cells then elongate, making the plant bend towards the light because of the uneven distribution of auxin
How do plants respond to gravity?
In the root and shoot, auxin gathers on the lower side. The root grows on the side with less auxin, making it bend and grow down towards gravity
Where is auxin produced?
Auxin is produced in cells near the tips of plant shoots and roots
What is Auxin’s function?
Auxins stimulate growth through cell elongation, and also help to regulate from development
What is Ethene’s function?
Cause plants to ripen by stimulating conversion of sugar to starch
What is Gibberellin’s function?
Promote growth, and end the dormancy period of seeds and buds
What are the uses of hormones?
Killing weeds, promote root growth, delaying ripening, ripening fruit, producing seedless fruit, controlling dormancy
Killing weeds
Auxin weedkillers make weeds grow too fast, and the uncontrolled growth kills the plant
Promoting root growth
Rooting powder contains auxin. Cut off a plant shoot, dip it into rooting powder and plant it. After a few days new roots develop from the cut stem
Delaying ripening
Auxin is sprayed to delay ripening, which allows a harvest to be collected at the same time
Ripening fruit
Ethene is sprayed on plants so their fruits ripen quicker, so the plants can be ready earlier in the growing season
Producing seedless fruit
If auxins are applied to unpollinated flowers the plant produces seedless fruit, as pollination produces seeds
Controlling dormancy
Commercial growers trigger seeds to germinate in the winter by spraying them with gibberellins or auxins in the greenhouse
