Biology unit 14 Flashcards
Neurons
A nerve is a bundle of neurons
Electrical impulses are sent through nerves to quickly send signals around our body
Used for rapidly coordinating or regulating the bodies functions (heart rate increases, liver release glucose and bladder relaxes.
Central nervous system
Consist of brain and spinal cord
Peripheral nervous system
Consist of all other nerves in the body
neuron structure
- dendrites receive signals from surrounding neurons they are branched to allow connections with many neurons
- the axon is a long structure off the cell body that electrical signals can be rapidly sent through. It’s long length allows for signals to be sent rapidly.
neuron structure part two
- the axon terminal is where the signal is passed to the next neuron over the synapse.
- nerve signals are always sent one way
How are nerve signal sent? - Reflex responses
1) stimulus e.g pain,smell,taste,visual,chemical is is received by a receptor
2) sensory neurons past signals back to the relay neuron in the CNS
3) the relay neuron sends this signal onto the motor neuron
4) the motor neuron sent the signal to effector organ usually a muscle or gland which is dense stimulated to respond
5) reflexes allow us to respond to stimuli extremely fast without conscious thought - signal doesn’t need to be interpreted by brain
Types of neurons
Sensory neurons have their cell body half way down the axon
* Relay neurons have a short axon (as they are not sending signals long distances)
* Motor neurons have the cell body at the end with the dendrites
Optic nerve
Sends nerve signals from the rod and cones cells in the retina to the brain
Retina
Is where light is focused in the eye. It contains light sensitive rod and cone
receptor cells
Iris
Is the coloured part of the eye which affects the size of the pupil.
Lens
Is able to change shape to focus light onto the retina.
Pupil
Is the opening in the eye which allows light to enter.
Suspensory ligaments
Attaches the lens to the ciliary muscles
Cornea
Is the curved part of the eye which refracts light as it enters.
Ciliary muscles
They contract or relax to make the suspensory ligaments go slack or tight
respectively, therefore changing the shape of the lens
Radial muscles
Contract in low lights so the pupil will appear larger
Circular muscles
Contract in bright light, so the pupil will appear smaller
Rod cells
Detects differences in light intensity, does not detect colour, use extensively and dim light
Information is carried by sensory neurons to the occipital lobe
Cone cells
Detect differences in colour, different cones detect red/blue/green
Information is carried by sensory neurons to the occipital lobe
The fovea
In the eye, a tiny pit located in the
retina that provides the clearest vision of all. The eye lens will focus light on to the fovea.
* No rods, only cones
Colour
Red, green and blue cones work together
to allow us to perceive a range of colours
What is a hormone
Chemical substance produced by a gland and carried by the blood which alters the activity of one or more specific target organs
Nerves and hormones
Nerves: sends signals fast through neurons
Effect is short term
Hormones: sends signals slowly through bloodstream
Hormones that control blood glucose levels - adrenaline
Adrenaline- secreted from adrenal gland causes liver to breakdown glycogen and release glucose into the bloodstream
Hormone that control blood glucose levels - glucagon
Secreted from pancreas. Causes the liver to break down glycogen into glucose and release it into the bloodstream. Used when blood sugar levels are low but not death situation
Hormones that control blood glucose levels - insulin
Secreted from the pancreas. Causes the liver to absorb glucose in to the bloodstream and convert it to glycogen for later use. Used when our blood sugar levels are high
What is homeostasis
The maintenance of a constant internal
environment
* Homeostasis always tries to keep a variable
in our body at a set point using negative feedback
* If a variable changes from the set po’int it will be detected by a receptor, transmitted by nerves and an effector will be activated to return the variable to its set point
Type 1 diabetes
Type one diabetes is a disorder in which the pancreas failed to produce sufficient insulin to control blood glucose levels
Type one diabetes are normally treated with insulin injections - uncontrolled high blood glucose levels
Type two diabetes
The body cells no longer response to insulin produced by the pancreas- cells are resistant and don’t responds as well as they should - uncontrolled high blood glucose levels
Carbohydrate control diet and exercise regime are common treatments for type two diabetes
What is a tropism
- it’s the growth response of an organism towards or away from a stimulus
Phototropism - growing towards or away from light
Gravitropism- growing towards or away from gravity
Auxin
is a growth regulating hormone. It makes plant shoot cells elongate. Auxin. Loosen the cell wall and stimulates cell elongation. Auxin is produced in the shoot tip and moves away from light.
Gravitropism
Auxin is also produced at root tips and has the exact opposite effect on
root cells. It inhibits cell elongation
Auxin also sinks to the bottom side of roots
This inhibits cell elongation on the bottom side of the root, causing the
root to grow down
