B3.1 Flashcards
How does your nervous system send impulses
It detects changes in the external environment
Sends this information to your brain where it is processed
Your brain decides on an appropriate response and sends an impulse to another part of your body telling it how to respond
What are the 3 main stages to a nervous response
- There is a change in environment (this is the STIMULUS)
- Groups of cells detect the stimulus ( these are the SENSORY RECEPTORS)
- a response occurs from the EFFECTORS. These are muscles or glands
How do muscles respond to an impulse?
By contracting
How do glands respond to an impulse
By releasing hormones
Where are receptor cells found
In your sense organs.
What do receptor cells detect?
They detect different stimuli. They change the stimulus into an electrical impulse that travels along the neurones to the CNS
Why are the CNS protected
They are made of delicate nervous tissue so are protected by bones.
The skill protects the brain
The vertebral column protects the spinal cord.
What is the receptor and stimulus for the eye
Receptor: light
Stimulus: light
What are the receptors and stimulus for the tongue
Receptor: taste
Stimulus: chemical
What are the receptors and stimulus for the skin
Receptor: pressure , temperature
Stimulus: pressure, heat
What are the receptors and stimulus for the nose
Receptor: smell , taste
Stimulus: chemical, chemical
What are the 3 types of neurones
Sensory neurones
Relay neurones
Motor neurones
What does a sensory neurone do?
It carries electrical impulses from the receptor cells to the CNS
What do relay neurones do?
They carry electrical impulses from sensory neurones to motor neurones
What do motor neurones do?
They carry electrical impulses from the CNS to effectors
What is a flow diagram for the steps involved in a nervous reaction?
Stimulus -> receptor cells -> sensory neurones -> spinal cord -> brain -> spinal cord -> motor neurones -> effector -> response
What is a co-ordinated response
A series of impulses being sent to different parts of the body producing the required action
What are voluntary actions
They occur as a result of you consciously deciding that you want to do something
What is a reflex action
They are automatic/ involuntary.
They occur without thinking
They only take 0.2 seconds
What does a dilated pupil do?
It allows more light into the eye so you can see in dim light
(Black bit is larger)
Flow diagram for a reflex action / reflex arc
Stimulus -> receptor cells -> sensory neurone -> spinal cord -> motor neurone -> effector -> response
What is the eye
It is the sense organ that allows you to see
Description and function of the cornea
Description: transparent coating on the front of the eye
Function: protects the eye, refracts light entering the eye
Description and function of the pupil
Description: central hole in the iris
Function: allows eye to enter the eye
Description and function of the iris
Description: coloured ring of muscle tissue
FUNCTION : Alters pupil size by contracting or relaxing
Description and function of the lens
Description: transparent biconvex lens
Function: focuses light clearly onto the retina
Description and function of the ciliary muscle
DESCRIPTION: a ring muscle of tissue
FUNCTION: alters the shape of the lens
Description and function of the sensory ligaments
Description: ligament tissue
Function: connects ciliary muscle to the lens
Description and function of the optic nerve
Description: nervous tissue
Function: carries nerve impulses to the brain
How are images formed?
The cornea refracts incoming light rays. This provided most of the focus to the incoming light
The light then passes through the pupil and is further refracted by the lens
This creates a sharp image in the retina
Light sensitive (photoreceptors) cells in the retina produce a nervous impulse when exposed to light.
This impulse travels down the optic nerve to the brain which interprets impulses as a visual image.
What happens so that you can focus on NEAR objects
Your ciliary muscle contracts and your lens becomes more convex (fatter)
What happens to allow you to focus on distant objects?
Your ciliary muscle relaxes and your lens becomes less convex (thinner)
What causes short sightedness
A persons lens is too strong or the eyeball is too long
What causes long sightedness
A persons lens is too weak or the eyeball is too strong
What can you do to correct short sightedness
Use a concave lens to bend the light rays outward before light enters the eye so that they now meet on the retina and the image is in focus
How can you correct long sightedness
A convex lens bends light rays inwards before they enter the eye. The light rays now meet on the retina so the image is in focus
What are the two types of photoreceptor cells in the retina
Rods and cones
What are rods
They respond to light and allow you to see in low light levels. They are not responsive to different colours
What are cones?
They respond to different colours. Different cone cells respond to red, blue and green light.
What is the function of the brain
It processes all the information collected by receptor cells about changes in your internal and external environment. It also receives and processes information from your hormonal system and produces a coordinated response
How many neurones are in an adult brain?
86 billion
What are the 5 main areas of the brain?
cerebrum cerebellum medulla Hypothalamus Pituitary gland
What does the cerebrum do?
Controls complex behaviours such as learning memory personality and conscious thought
What does the cerebellum do?
Controls posture, balance and involuntary movement
What does the medulla do?
Controls automatic actions such as heart rate ate breaking rate
What does the hypothalamus do?
Regulates temperature and water balance
What does the pituitary gland do?
Stores and releases hormones that regulate body functions
How can you investigate brain function?
Analysing the damaged region and its effects enabled scientists to work out the function of different regions
Placing electrodes inside animal and human brains. The electrodes transmit electrical impulses which result in movement in different parts of the body allowing scientists to link areas of the brain with the region of the body it controls
CT SCANS
MRI SCANS
fMRI scans
Difficulties with investigating brain function
Patients have to give consent for medical info to be shared
Many case studies need to be analysed to draw reliable conclusions.
Several areas of the brain may be involved in a specific function
Animal testing is unethical
What is a CT SCAN?
Computed tomography scans use X rays to create 3D images of inside the body
The position of any abnormalities can be linked to changes in a patients behaviour.
They cannot be used regularly as X ray radiation increases the risk of cancer
What is a MRI scan?
Magnetic resonance imaging scans use powerful magnets to identify brain abnormalities,
What is an fMRI scan?
Functional magnetic resonance imaging produced images in real time,
Scientists identify areas of the brain that show increased blood flow. These areas are active when a person is carrying out a specific activity.
What is the PNS?
It consists of all the neurones that connect the CNS to the rest of the body.
These are the sensory neurones and the motor neurones
What does the dendron do?
Carry electrical impulses to the cell body.
What does the axon do?
Transmit impulse away from the cell body
What does having a central control system mean?
Neuronal communication is faster.
How can nervous system damage to the CNS or PNS occur?
Injury
Disease
A genetic condition
Ingesting a toxic substance
What are the effects of damage to the PNS?
Inability to detect pain
Loss of co-ordination
numbness
Explain what happens to minor nerve damage in the PNS
The PNS has a limited ability to regenerate
Minor nerve damage often self-heals and the symptoms gradually decrease.
Effects of damage to the CNS
A loss of control of body systems
Partial of complete paralysis
Memory loss or processing difficulties
Why is it difficult to repair the CNS
The spinal cord is around 1.5 cm in diameter so identifying and repairing damage to an individual nerve fibre without damaging others is very difficult.
How can some conditions for the brain be treated?
Radiotherapy
Chemotherapy
Surgery
Deep brain stimulation
What can radiotherapy and chemotherapy be used to treat?
It can be used to treat a brain tumour
How can surgery be used to treat damage to the brain
It can be used to remove damaged brain tissue
What is deep brain stimulation and what does it do?
Inserting an electrode to stimulate brain function
