B3 - Organism-Level Systems Flashcards
Describe the role of sensory neurones.
To send nervous (electrical) impulses from receptors to the central nervous system (CNS)
Give some examples of effectors.
1) muscle
2) gland
What is the purpose of a reflex action?
To stop you injuring yourself
Describe the pathway from stimulus to response.
1) stimulus
2) receptor
3) sensory neurone
4) central nervous system
5) motor neurone
6) effector
7) response
What term describes an eye condition in which a person can’t tell the difference between certain colours?
Colour blindness
What are electrical impulses passed along?
The axon of a neurone
Why do neurones have dendrites?
So they connect with lots of other neurones
What does a fatty (myelin) sheath do?
Acts as an electrical insulator, speeding up the electrical impulse
What is the connection between two neurones called?
A synapse
What happens in a synapse?
1) the electrical impulse triggers the release of transmitter chemicals, which diffuse across the gap
2) these chemicals bind to receptor molecules in the membrane of the next neurone. This sets off a new electrical impulse
What do sensory receptors detect?
A change in your environment (a stimulus)
What do receptors in your eyes detect?
Light
What do receptors in your skin detect?
1) touch (pressure)
2) temperature change
What does the central nervous system consist of?
1) brain
2) spinal cord
Describe the pathway of a reflex arc from stimulus to response.
1) stimulus
2) receptor
3) sensory neurone
4) relay neurone
5) motor neurone
6) effector
7) response
What does the cornea do in the eye?
Refracts (bends) light into the eye
What does the iris do in the eye?
Controls how much light enters the pupil (the hole in the middle)
What does the lens do in the eye?
Refracts light, focusing it onto the retina
What does the ciliary body do in the eye?
Contains ciliary muscles, which are attached to suspensory ligaments - they work together to alter the shape of the lens
What is the retina covered in?
Receptors called rods and cones
When are rods more sensitive?
In dim light
What can’t rods sense?
Colour
What are cones sensitive to?
Different colours
What does the optic nerve do in the eye?
Carries impulses from the receptors to the brain
How does the eye focus light?
By changing the shape of the lens
To look at distant objects, what happens?
1) the ciliary muscle relaxes, which allows the suspensory ligaments to pull tight
2) this pulls the lens into a less rounded shape so light is refracted less
To look at close objects, what happens?
1) the ciliary muscle contracts, which slackens the suspensory ligaments
2) the lens becomes a more rounded shape, so light is refracted more
What are long-sighted people unable to focus on?
Near objects
What are short-sighted people unable to focus on
Distant objects
What lens can correct long-sightedness?
Convex
What lens can correct short-sightedness?
Concave
What is an alternative to glasses or contact lenses?
Corneal laser surgery
What is the most common form of colour blindness?
Red-green
How is red-green colour blindness caused?
When red or green cones in the retina are not working properly
What can be used to help people see colours more normally?
Tinted lenses
What is the brain responsible for?
Complex behaviours
What is the brain made up of?
Billions of interconnected neurones
What is the cerebrum responsible for?
1) consciousness
2) intelligence
3) memory
4) language
What does the hypothalamus do?
1) maintains body temperature at the normal level
2) produces hormones that control the pituitary gland
What does the pituitary gland do?
Produces many important hormones, such as some of those involved in the menstrual cycle
What does the medulla do?
Controls unconscious activities (things you don’t have to think about doing) like breathing and your heart rate
What is the cerebellum responsible for?
Muscle coordination
Why can investigating brain function be tricky?
1) if a person is severely brain damaged, it may be unethical to study them as they might not be able to give informed consent
2) studying the brains of people who have dies relies on people donating their brains for research
3) there can be problems when interpreting the results of case studies
What things could go wrong with the brain or other parts of the nervous system?
1) injuries to the brain or spinal cord
2) tumours
3) diseases
Why are problems in the brain difficult to treat successfully?
1) it’s hard to repair damage to the nervous system
2) if a problem occurs in a part of the nervous system that’s not easy to access it can be hard to treat
3) treatment for problems in the nervous system may lead to permanent damage
Why is it hard to repair damage to the nervous system?
1) neurones in the central nervous system don’t readily repair themselves
2) scientists haven’t developed a way to repair nervous tissue in the central nervous system
What are hormones?
Chemicals produced in various glands called endocrine glands
What system do the endocrine glands make up?
Endocrine system
What are the cells affected by hormones called?
Target cells
What is an organ that contains target cells called?
Target organ
What gland is adrenaline released by?
Adrenal glands (which are located just above the kidneys)
What does adrenaline prepare the body for?
‘Fight or flight’
How does adrenaline prepare the body for ‘flight or fight’?
Activating processes that increase the supply of oxygen and glucose to cells
How does adrenaline increase heart rate and blood pressure?
Adrenaline binds to specific receptors in the heart. This causes the heart muscle to contract more frequently and with more force
How does adrenaline increase respiration?
Increased heart rate and blood pressure increases blood flow to the the muscles, so the cells receive more oxygen and glucose needed for respiration
How does adrenaline increase blood sugar level?
Adrenaline binds to receptors in the liver. This causes the liver to break down its glycogen stores to release glucose
What gland is thyroxine released by?
Thhyroid glands ( found in the neck)
What does thyroxine regulate?
Metabolism
What is metabolic rate?
The speed at which chemical reactions in the body occur
What is metabolic rate important for?
1) growth
2) protein synthesis
Where is thyroid stimulating hormone (TSH) released from?
Pituitary gland
What is testosterone?
The main male sex hormone
Where is testosterone produced?
Testes
What does testosterone stimulate?
Sperm production
What is testosterone important for in the development of?
The male reproductive system
What is oestrogen?
The main female sex hormone
Where is oestrogen produced?
Ovaries
What does oestrogen promote the development of?
Female sexual characteristics
Where is progesterone produced?
Ovaries
What does progesterone support?
Pregnancy
Where is FSH (follicle-stimulating hormone) produced?
Pituitary gland
Where is LH (luteinising hormone) produced?
Pituitary gland
What is the menstrual cycle?
The monthly sequence of events in which the female body releases an egg and prepares the uterus (womb) in case it receives a fertilised egg
What are the four stages of the menstrual cycle?
1) Day 1 is when menstruation starts
2) The lining of the uterus builds up again
3) An egg develops and is released (ovulation)
4) The lining is then maintained
What happens at day 1 of the menstrual cycle?
The uterus lining breaks down and is released
What happens from days 4 to 14 of the menstrual cycle?
The lining of the uterus builds up again, into a thick spongy layer full of blood vessels ready to receive a fertilised egg
What happens at about day 14 of the menstrual cycle?
An egg develops and is released from an ovary
What happens for about 14 days, from day 14 to day 28 in the menstrual cycle?
The lining is then maintained. If no fertilised egg is implanted into the uterus wall by day 28, the spongy lining starts to break down again and the whole cycle starts over
What four hormones control the menstrual cycle?
1) FSH
2) Oestrogen
3) LH
4) Progesterone
What does FSH do?
1) causes an egg to mature in one of the ovaries
2) stimulates the ovaries to produce oestrogen
What does Oestrogen do?
1) causes the lining of the uterus to thicken and grow
2) stimulates the production of LH
3) inhibits the production of FSH so that only one egg is released in each cycle
What does LH do?
1) stimulates the release of an egg at day 14 (ovulation)
2) indirectly stimulates progesterone production
What does progesterone do?
1) maintains the lining of the uterus. When the level of progesterone falls and there’s a low oestrogen level, the lining breaks down
2) inhibits the production of FSH and LH
3) a low progesterone level allows FSH to increase and then the whole cycle starts again
