B3 Flashcards
How do nerve impulses travel through your nervous system (conscious)
Stimulus → Receptor cells → sensory neurone → Spinal cord → Brain → Spinal cord → motor neurone → Effector response
What do relay neurones do
Carry electrical impulses from sensory neurons to your motor neurons
And from the spinal cord to motor neurones
What is the reflex arc
The pathway of an impulse during a reflex reaction
Stimulus → receptor cells → Sensory neurone → spinal cord → motor neurone → effector →response
What does a motor neurone do
Carry electrical impulses from the cns to the effectors
What do sensory neurones do
Carry electrical impulses from receptor cells to cns
How are nerve impulses moved across neurones
The synaptic cleff is the area between two neurons.
A nerve impulse pushes the Neurotransmitters in vesicles to the edge of the presynaptic neurone
It diffuses across the postsynaptic neurone where it binds to the receptors (lock and key hypothesis) which creates a new nerve impulse
An example of a neurotransmitter used is adenosine
What are the main parts of an eye and what are there functions
Suspensory ligament - alters the shape of the lense (so does ciliary muscle)
Retina - contains photoreceptors (rods and cones)
Optic nerve - carries impulses to the brain
Lense - refracts and focuses light onto the retina (so does the cornea)
Pupil - allows light into the eye
Iris - controls the size of the pupil
What two muscles is the iris made of, and what are their purposes
The circular (inside) and radial (outside) muscles
When the circular muscle contracts the radial relaxes, letting less light into the eye
(Constriction)
When the radial contracts the circular relaxes, letting more light into the eye
(Dilation)
How do we focus on close objects.
The lens must be thicker to refract the light more.
The ciliary muscle contracts causing the suspensory ligament to slacken (reducing tension)
This makes the lens bulge and be more convex
How do we focus on far images
The lens needs to refract light less
The ciliary muscle relaxes, making the suspensory ligament taught, increasing tension.
The greater tension makes the lens stretch becoming less convex
What is the process of focusing on different distanced objects called
Accomodation
What is hyperopia and why does it occur.
Long sightedness (cant focus on close objects)
It occurs when the focal point is too far behind the eye or the eyeball is too short (or lens is less convex)
A convex (converging) lens is used to fix it (light refracts more)
What is myopia and why does it occur
Short - sightedness (cant focus far objects)
Focal point is in front of the retinas
Eyeball is too long / lens refracts too much
This is fixed using a concave lens which refracts the light outwards
What are rods and cones
Rods - respond to light
Cones - respond to colours
What is colour blindness
The inability to see certain colours due to a lack of cones
It is sex linked and more common in men
What are the parts of the brain?
Cerebrum - controls complex behaviour ( learning / voluntary movement / conscious thought(
Cerebellum - controls posture balance and involuntary movement
Hypothalamus - thermal / water (osmoregulation) regulation
Pituitary gland - controls hormones / stores and releases hormones
Medulla - controls automatic reactions like heart rate
What are hormones?
Chemical messengers that cause a response in specific target hormones
What is the endocrine system
All the endocrine glands and the hormones they produce.
An endocrine gland is a gland which secretes hormones
What is a target organ
Organ a hormone has effect on
How are hormones carried
In the blood stream in plasma
How are the endocrine system and the nervous system related
They both send messages around the body for a response.
Together they control and coordinate body processes
They provide information about changes in your environment
What are target cells and what do hormones do to them
Target cells are cells which a hormone is able to bind to.
Hormones diffuse out of the blood and bind to receptors (with a complimentary active site) found on the cells membrane or cytoplasm
Differences between the nervous system and endocrine system
Nerves - travel fast through electrical impulses, and act for a short time over a small area
Hormones - travel slower through the blood, and act for a longer time for a larger ara
Name 3 hormones, what they do, and the gland they are released from.
Testosterone - Released from the testes, promotes growth of secondary male characteristics
Thyroxine - Released from the thyroid (found in your throat) gland and controls metabolic rate
Adrenaline - released from your adrenal gland (above the kidneys) and is responsible for your fight or flight response
What is negative feedback
A process in homeostasis:
A change away from the normal value is detected and your body works to return that value to normal through the use of effectors
What is homeostasis
A process which:
Maintains internal body conditions within a narrow range
What does adrenaline do
When you feel threatened or scared the brain (specifically your hypothalamus) signals the adrenal glands to secrete adrenaline
This results in:
Higher respiration rate, more oxygen is needed to produce more ATP
Increasing heart rate (to transport the oxygen elsewhere)
Blood diversion from non essential organs like skin or your digestive system to the blood.
What is TRH and what releases it
TRH - thyroid releasing hormone (released by the hypothalamus)
It travels through the blood stream and binds to the pituitary gland
What is TSH and what gland is it secreted by
TSH - thyroid stimulating hormone (released by the anterior pituitary gland)
Binds to the thyroid causing thyroxine to be produced
How is negative feedback used to keep thyroxine levels stable.
-The hypothalamus detects a change in thyroxine levels
-It releases TRH which is transported through the blood to the anterior pituitary gland
-once it binds to that TSH is released which then travels through the blood to the thyroid gland
-TSh binds to specific shaped receptors on the thyroid gland
-thyroxine is then produced
-the hypothalamus detects this and stops producing TRH
-the thyroxine increase inhibits the production of TSH
What is Goitre
A condition which causes a swollen thyroid gland due to an iodine deficiency
Iodine is required for the production of thyroxine, so people with goitre will have a lower metabolism
What is FSH
Follicle stimulating hormone - is secreted by the pituitary gland and travels to the ovaries where it causes an egg to mature
It also stimulates the ovaries to produce Oestrogen
What is LH
Luteinising Hormone - triggers ovulation (also comes from the pituitary gland)
Causes empty egg follicles to develop into the corpus luteum - so progesterone is released
Inhibits FSH and oestrogen
What is Oestrogen
Oestrogen is a hormone secreted by the ovaries and causes the uterus lining to build up
It inhibits FSH from being produced. And it stimulates the pituitary gland to release LH
What is progesterone
Progesterone is a hormone secreted by the corpus luteum in the ovaries. It maintains the uterus lining
This hormone remains high during pregnancy.
It inhibits FSH and LH
What is the menstraul cycle
The 28 day cycle where a woman’s body is prepared for pregnancy
What is the menstrual cycle
The 28 day cycle where a woman’s body is prepared for pregnancy
What happens during day 0-5 of the menstrual cycle
Menstruation (a period) will occur.
The uterus lining breaks down
What happens during day 5-13 of the menstrual cycle
The uterus lining thickens (high amounts of oestrogen)
What happens during day 14 of the menstrual cycle
Ovulation - an egg is released by the ovaries, and empty egg follicles break down into the corpus luteum
(High amounts of LH around / before day 14)
What happens during day 14-28 of the menstrual cycle
The uterus lining stays the same
(High amounts of progesterone)
What happens if an egg isnt fertilised by day 28
The uterus lining (endometrium) breaks down
What is a haploid cell, and what is a diploid cell
Haploid cell contains one set chromosomes (sperm or egg)
A diploid cell contains two sets chromosomes (e.g a Zygote)
What is contraception
Methods used to prevent pregnancy split into hormonal and non hormonal.
Currently hormonal systems only effect the female reproductive system
What are the non hormonal methods of contraception and how do they work.
Condoms - placed over the penis or inside the vagina, prevents sperm from entering the vagina. They are a one time use and prevent STIs
Diaphragm or cervical cap - inserted into the cervix to prevent sperm entering the uterus. Removed 6+ hours after sexual intercourse ( only effective if paired with spermicide)
IUD - Inserted into the uterus and releases copper which prevents sperm surviving in fallopian tubes or the cervix. Can also prevent ovum implantation
(Effective for 5-10 years)
How effective is each method of contraception
Male condom 98%
Female condom 95%
Diaphragm and cap 92-96%
(Assuming they are used correctly)
The other methods are over 99%
Why are some people infertile.
Too old
Blocked sperm ducts
Not enough sperm produced
A lack of mature eggs
A failure from the ovaries to release an egg
How does fertility treatment work.
FSH can be used as a drug to try and stimulate eggs to mature in the ovaries.
What is IVF and how does it work.
In vitro fertilisation is the process of binding a sperm cell and an egg cell outside of the female reproductive system.
Eggs are taken from the female using a vaginal ultrasound + anesthetic
Sperm capacitation must occur (through ejaculation)
Prepare the semen and eggs and then IVF can occur in 2 ways
Conventional - Egg is surrounded by sperm cells and one binds with the egg
Intra-cytoplasmic sperm injection (ICSI) - one specific sperm is inserted into the egg
Once this is done the zygote (at its current stage a blastocyst) will be incubated for around 5 days where it should have grown to 32 cells.
Multiple embryos are then transferred back into the woman for a higher chance of success
What is tropism
Growth or movement in one direction due to stimulus
What is phototropism and how does it work
Negative (nothing happens)+ positive
Plant grows toward the light
Auxin in the shoot tip diffuses down and away from the light causing a faster rate of cell elongation on the side of most auxin. This makes the plant grow to the light
What is gravitropism and how does ot work
Gravitropism is the plants roots moving with gravity
Auxins diffuse down the root.
Cell elongation occurs on the side with the least auxin
What are the three main plant hormones and what do they do
Auxin - promotes cell elingation and fruit development
Ethene - ripens fruit by converting starch in glucose
Gibberellins - promotes cell elongation and breaks seed dormancy
Give three practical uses of plant hormones
Plants can be gassed with ethene a day before they are taken to the shops ensuring they are as ripe as possible
Seedless fruit can be made by adding auxin to them as it can cause fruit development even without fertilisation
(Parthenocarpy)
Weed killer is made using auxins. As broader leaves have a greater diffusion area they will gain more auxins, causing them to grow uncontrollably and die
Gibberellins can be used to make seeds germinate
Where can your thermoreceptors and osmoreceptors be found
In your brain - in the hypothalamus
They can also be found in the skin to detect external temperatures
How does your body detect an increase or decrease in your body temperature.
Your thermoreceptors will detect a change in the temperature of your blood away from 37°C
What happens when your body gets too cold.
Shivering (thermogenics) - muscles contract and relax - aerobic respiration is exothermic so energy is released heating you up + break down of atp is exothermic releasing even more energy
Hairs raising - Your erector muscles control your body hairs and when they contract your body hairs rise. When they rise air is trapped, the air will warm up as its close to your skin and cant rise to escape so heat loss by convection is released
Vasoconstriction - Arterioles constrict which reduces blood flow to the capillaries at the skin so less heat is lost by radiation
What happens when you are too hot
Vasodilation - Arterioles widen and blood rushes to capillaries near your skin. Heat lost by radiation increases - this is what causes your skin to turn red
Sweating - sweat produced by sweat gland (exocrine gland). When it evaporates thermal energy is transferred into the environment
Water is also held together by hydrogen bonds they absorb thermal energy to break and then the water can evaporate (endothermic reaction)
Erector muscles relax
What is glucose homeostasis
Process to keep glucose concentration levels stable
How are glucose levels kept stable
When you eat your blood glucose level increases
The pancreas detects a change
The pancreas releases insulin
This travels through the blood and binds to specific target receptors in muscles and the liver (target organ)
This causes glucose to be converted to glycogen
Then your blood sugar level decreases
Whats the average blood glucose concentration
90mg / 100ml of blood
How is glycogen converted back into glucose
Pancreas detects decrease of blood glucose concentration using receptors
Glucagon is secreted into the blood stream . - by the pancreas
Glucagon binds to target receptors in the muscles or liver
Glucagon causes glycogen to break down back into the blood
This makes the blood glucose concentration increase
What is type 1 diabetes
Your body is unable to produce insulin as beta cells (insulin producing cells) in the pancreas are destroyed by your immune system.
This can be controlled through insulin injections
What is type 2 diabetes
Often occurs due to obesity
Body doesn’t produce enough insulin
They could also have insulin resistance
Insulin resistance happens when people produce too much insulin and they become insulin deficient
This can also be controlled by insulin injections
What is Hypoglycemia and hyperglycemia
1) Low glucose levels in the blood
2) High glucose levels in the blood
What are the two main functions of the kidney
Excretion - removal of metabolic waste (water h2o or urea)
Osmoregulation - maintains water potential in the blood
How is urea produced
Urea is produced by the breakdown of amino acids as when they break down ammonia is released. This is dangerous so it combines with carbon dioxide to form urea
What does the term renal refer to.
Renal refers to the kidneys
What is the structure of a sensory neuron
The dendrites are connected to a dendron.
The dendron passes through the cell body, then through the axon to the axon terminals.
The axon / denron is surround by the mylin sheath
What do dendrites do
Receive a neuro-transmitter which starts a nerve impulse
What does the axon terminal do
It releases neuro-transmitters which bind to receptors on the dendrites
What does the dendron / axon do
They join the dendrites and axon terminals together allowing electrical impulses to pass.
The impulse travels through these
What does the mylin sheath do
Protects / insulates the neuron the
Speeds up the transport of nerve impulses
Maintains the impulse strength
What days are the best days for fertilisation
The days before ovulation, days 12-14
What is metabolic waste
The products that cannot be used up
These waste products are as a result of metabolic reactions
What is the structure of the kidney
He kidney is made up of nephrons which all connect to each other through collecting ducts
Your kidney is made of a
capsule - outer membrane of the kidney (maintains the kidneys shape)
Cortex - outer part of the kidney
Medulla - inner part of the kidney
The kidney is also connected to the ureter which takes urine to the bladder
Renal artery / vein
How is the nephron structured
The glomerulus is located inside the bowman capsule
Glomerulus - complex web of capillaries and it filters the blood
Bowmans capsule - The filtrate travels through here and into the proximal convoluted tubule
From the proximal convoluted tubule it travels to the loops of henlé and then up to the distal convoluted tubule
It then enters the collecting duct and leaves the kidney
What is each process that occurd in nephron and where they do they occur
Ultrafiltration - in the glomerolous, ions, amino acids, glucose, salt and water are absorbed into the bowmans capsule
Selective reabsorption - in the proximal convoluted tubule (some ions some water, all sugars and amino acids are abslrbed back into the blood stream)
Reabsorbtion - in the collecting duct. some water is reabsorbed / most salts/ions are reabsorbed - the filtrate remains as ions water and urea
What is adh / what does it do and what releases it
Anti - diuretic hormone released by the pituitary glands
It causes the collecting duct to be more permeable to water so more is absorbed
What is the structure of a motor neuron
It only has an axon surrounded by a mylin sheath
The cell body is found by the dendrites
It has dendrites and axon terminals
What is the structure of a relay neuron
It has dendrites and axons connected to a cell body
What happens when you have a low water potential in your blood
(Kidneys)
Your pituitary gland will release more adh
This means the collecting duct will be more permeable to water, so more water is released back into the blood
Results in more concentrated urine
What is the pns
All neurons outside the cns
(Peripheral nervous system)
What happens when the pns is damaged (symptoms)
Inability to detect pain
Numbness
Lack of coordination
What happens when the cns is damaged
Loss of control of body systems
Partial or complete paralysis
Memory loss or processing difficulties
How can brain function be investigated
Through scans
Mri
Pet scans
Ct scand
Fmri scans
How does each scan work and what are its dangers
MRI - magnetic fields + radio waves to map inages of the brain (whole body goes in the machine, so pacemakers and artificial joints can be damaged) It looks at structure and gives high res images
PET - uses radiotracers (e.g radioactive glucose), releases positrons that show function. This produces gama rays which are dangerous
CT - x ray images of the brain - low resolution image that looks at structure
FMRI - uses responses of oxygenated and deoxygenated blood to show brain response. Has the same issues as mri scans
X-rays - use ionising radiation which in large / frequent amounts can cause mutation or damage to DNA
Advantages and disadvantages of studying the brain
Advantages:
Alows for a greater understanding of how the brain works
Can help decide treatment for certain injuries
Disadvantages:
ethical issues → (can ppl w brain damage consent)
Its fragile → damage to tissue can remove brain functions
Risk of damage from radiation.
May be hard to find volunteers to study
People with brain damage cant give fully informed consent
Difficult to pinpoint a function
What does a convex lens do
Refracts light inward to a point
(Thick lens)
What does a concave lens do
Disperses light outwards
(Thin one)
What happens when the iris constricts
The circular muscle (smaller inside muscle) contracts and the radial (larger outside muscle) relaxes.
This makes the pupils diametermaller and lets less light in
What happens when the iris dilates
The circular muscle (smaller inside muscle) relaxes and the radial (larger outside muscle) contracts.
This increases the pupils diameter, letting in more light
Why does caffeine stop you from being tired
Adenosine ( a neuro transmitter) binds to the postsynaptic neuron.
Caffeine has the same shape and can bind instead, which means the feeling of drowsiness will be produced less
Where are most motor neurons found
By the brain and spinal chord
What is a synapse
A junction between two neurons
What is FSH + what does it do
Follicle stimulating hormone
Causes egg to mature in the ovaries
Stimulates production of oestrogen
Secreatrd by the pituitary gland
What is oestrogen + whats it do
Causes the lining of the uterus to build up
Secreted by the ovaries
Inhibits FSH
Stimulates release of LH
What is LH + what it do
Luteinising hormone.
When this hormone peaks ovulation occurs.
Causes empty follicles to break down into the corpus leuteum
What is progesterone + whats it do
Maintains the uterus lining
Released by the corpus luteum
Inhibits LH, Oestrogen and FSH
What does the progesterone pill do
Thickens cervical mucus stopping sperm from reaching an ovum.
Thins the uterus lining, preventing implantation.
It can also prevent ovulation.
It must be taken around the same time every day
What does the combined pill do
(Oestrogen and progesteron)
Prevents ovulation,
thickens cervical mucus preventing the sperm from reaching an ovum.
Prevents fertilised eggs implanting into the uterus.
Taken for 21 days of the menstrual cycle
What does an IUS do
An intrauterine system
Thickens cervical mucus stopping sperm from reaching an ovum.
Thins the uterus lining, preventing implantation.
It can also prevent ovulation.
It must be taken around the same time every day
What are two common methods of excretion
Breathing out and through the kidneys (urination)
Where is glycogen stored
In the liver or the muscles
Issues of using case studies to study the brain
May not be able to consent → finding volunteers is hard
Very specific study
